2015-05-25 13:10:20 +00:00
/*
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* Non - physical true random number generator based on timing jitter - -
* Jitter RNG standalone code .
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*
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
* Copyright Stephan Mueller < smueller @ chronox . de > , 2015 - 2023
2015-05-25 13:10:20 +00:00
*
* Design
* = = = = = =
*
2020-07-19 16:49:59 +00:00
* See https : //www.chronox.de/jent.html
2015-05-25 13:10:20 +00:00
*
* License
* = = = = = = =
*
* Redistribution and use in source and binary forms , with or without
* modification , are permitted provided that the following conditions
* are met :
* 1. Redistributions of source code must retain the above copyright
* notice , and the entire permission notice in its entirety ,
* including the disclaimer of warranties .
* 2. Redistributions in binary form must reproduce the above copyright
* notice , this list of conditions and the following disclaimer in the
* documentation and / or other materials provided with the distribution .
* 3. The name of the author may not be used to endorse or promote
* products derived from this software without specific prior
* written permission .
*
* ALTERNATIVELY , this product may be distributed under the terms of
* the GNU General Public License , in which case the provisions of the GPL2 are
* required INSTEAD OF the above restrictions . ( This clause is
* necessary due to a potential bad interaction between the GPL and
* the restrictions contained in a BSD - style copyright . )
*
* THIS SOFTWARE IS PROVIDED ` ` AS IS ' ' AND ANY EXPRESS OR IMPLIED
* WARRANTIES , INCLUDING , BUT NOT LIMITED TO , THE IMPLIED WARRANTIES
* OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE , ALL OF
* WHICH ARE HEREBY DISCLAIMED . IN NO EVENT SHALL THE AUTHOR BE
* LIABLE FOR ANY DIRECT , INDIRECT , INCIDENTAL , SPECIAL , EXEMPLARY , OR
* CONSEQUENTIAL DAMAGES ( INCLUDING , BUT NOT LIMITED TO , PROCUREMENT
* OF SUBSTITUTE GOODS OR SERVICES ; LOSS OF USE , DATA , OR PROFITS ; OR
* BUSINESS INTERRUPTION ) HOWEVER CAUSED AND ON ANY THEORY OF
* LIABILITY , WHETHER IN CONTRACT , STRICT LIABILITY , OR TORT
* ( INCLUDING NEGLIGENCE OR OTHERWISE ) ARISING IN ANY WAY OUT OF THE
* USE OF THIS SOFTWARE , EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
* DAMAGE .
*/
/*
* This Jitterentropy RNG is based on the jitterentropy library
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
* version 3.4 .0 provided at https : //www.chronox.de/jent.html
2015-05-25 13:10:20 +00:00
*/
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# ifdef __OPTIMIZE__
# error "The CPU Jitter random number generator must not be compiled with optimizations. See documentation. Use the compiler switch -O0 for compiling jitterentropy.c."
# endif
typedef unsigned long long __u64 ;
typedef long long __s64 ;
typedef unsigned int __u32 ;
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
typedef unsigned char u8 ;
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# define NULL ((void *) 0)
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/* The entropy pool */
struct rand_data {
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
/* SHA3-256 is used as conditioner */
# define DATA_SIZE_BITS 256
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/* all data values that are vital to maintain the security
* of the RNG are marked as SENSITIVE . A user must not
* access that information while the RNG executes its loops to
* calculate the next random value . */
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
void * hash_state ; /* SENSITIVE hash state entropy pool */
__u64 prev_time ; /* SENSITIVE Previous time stamp */
__u64 last_delta ; /* SENSITIVE stuck test */
__s64 last_delta2 ; /* SENSITIVE stuck test */
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unsigned int flags ; /* Flags used to initialize */
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
unsigned int osr ; /* Oversample rate */
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# define JENT_MEMORY_ACCESSLOOPS 128
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# define JENT_MEMORY_SIZE \
( CONFIG_CRYPTO_JITTERENTROPY_MEMORY_BLOCKS * \
CONFIG_CRYPTO_JITTERENTROPY_MEMORY_BLOCKSIZE )
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unsigned char * mem ; /* Memory access location with size of
* memblocks * memblocksize */
unsigned int memlocation ; /* Pointer to byte in *mem */
unsigned int memblocks ; /* Number of memory blocks in *mem */
unsigned int memblocksize ; /* Size of one memory block in bytes */
unsigned int memaccessloops ; /* Number of memory accesses per random
* bit generation */
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/* Repetition Count Test */
crypto: jitter - permanent and intermittent health errors
According to SP800-90B, two health failures are allowed: the intermittend
and the permanent failure. So far, only the intermittent failure was
implemented. The permanent failure was achieved by resetting the entire
entropy source including its health test state and waiting for two or
more back-to-back health errors.
This approach is appropriate for RCT, but not for APT as APT has a
non-linear cutoff value. Thus, this patch implements 2 cutoff values
for both RCT/APT. This implies that the health state is left untouched
when an intermittent failure occurs. The noise source is reset
and a new APT powerup-self test is performed. Yet, whith the unchanged
health test state, the counting of failures continues until a permanent
failure is reached.
Any non-failing raw entropy value causes the health tests to reset.
The intermittent error has an unchanged significance level of 2^-30.
The permanent error has a significance level of 2^-60. Considering that
this level also indicates a false-positive rate (see SP800-90B section 4.2)
a false-positive must only be incurred with a low probability when
considering a fleet of Linux kernels as a whole. Hitting the permanent
error may cause a panic(), the following calculation applies: Assuming
that a fleet of 10^9 Linux kernels run concurrently with this patch in
FIPS mode and on each kernel 2 health tests are performed every minute
for one year, the chances of a false positive is about 1:1000
based on the binomial distribution.
In addition, any power-up health test errors triggered with
jent_entropy_init are treated as permanent errors.
A permanent failure causes the entire entropy source to permanently
return an error. This implies that a caller can only remedy the situation
by re-allocating a new instance of the Jitter RNG. In a subsequent
patch, a transparent re-allocation will be provided which also changes
the implied heuristic entropy assessment.
In addition, when the kernel is booted with fips=1, the Jitter RNG
is defined to be part of a FIPS module. The permanent error of the
Jitter RNG is translated as a FIPS module error. In this case, the entire
FIPS module must cease operation. This is implemented in the kernel by
invoking panic().
The patch also fixes an off-by-one in the RCT cutoff value which is now
set to 30 instead of 31. This is because the counting of the values
starts with 0.
Reviewed-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Reviewed-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-03-27 07:03:52 +00:00
unsigned int rct_count ; /* Number of stuck values */
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/* Adaptive Proportion Test cutoff values */
unsigned int apt_cutoff ; /* Intermittent health test failure */
unsigned int apt_cutoff_permanent ; /* Permanent health test failure */
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# define JENT_APT_WINDOW_SIZE 512 /* Data window size */
/* LSB of time stamp to process */
# define JENT_APT_LSB 16
# define JENT_APT_WORD_MASK (JENT_APT_LSB - 1)
unsigned int apt_observations ; /* Number of collected observations */
unsigned int apt_count ; /* APT counter */
unsigned int apt_base ; /* APT base reference */
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unsigned int health_failure ; /* Record health failure */
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unsigned int apt_base_set : 1 ; /* APT base reference set? */
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} ;
/* Flags that can be used to initialize the RNG */
# define JENT_DISABLE_MEMORY_ACCESS (1<<2) / * Disable memory access for more
* entropy , saves MEMORY_SIZE RAM for
* entropy collector */
/* -- error codes for init function -- */
# define JENT_ENOTIME 1 /* Timer service not available */
# define JENT_ECOARSETIME 2 /* Timer too coarse for RNG */
# define JENT_ENOMONOTONIC 3 /* Timer is not monotonic increasing */
# define JENT_EVARVAR 5 / * Timer does not produce variations of
* variations ( 2 nd derivation of time is
* zero ) . */
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# define JENT_ESTUCK 8 /* Too many stuck results during init. */
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# define JENT_EHEALTH 9 /* Health test failed during initialization */
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# define JENT_ERCT 10 /* RCT failed during initialization */
# define JENT_EHASH 11 /* Hash self test failed */
# define JENT_EMEM 12 /* Can't allocate memory for initialization */
2020-04-17 19:33:33 +00:00
2023-10-19 07:40:42 +00:00
# define JENT_RCT_FAILURE 1 /* Failure in RCT health test. */
# define JENT_APT_FAILURE 2 /* Failure in APT health test. */
# define JENT_PERMANENT_FAILURE_SHIFT 16
# define JENT_PERMANENT_FAILURE(x) (x << JENT_PERMANENT_FAILURE_SHIFT)
# define JENT_RCT_FAILURE_PERMANENT JENT_PERMANENT_FAILURE(JENT_RCT_FAILURE)
# define JENT_APT_FAILURE_PERMANENT JENT_PERMANENT_FAILURE(JENT_APT_FAILURE)
crypto: jitter - add oversampling of noise source
The output n bits can receive more than n bits of min entropy, of course,
but the fixed output of the conditioning function can only asymptotically
approach the output size bits of min entropy, not attain that bound.
Random maps will tend to have output collisions, which reduces the
creditable output entropy (that is what SP 800-90B Section 3.1.5.1.2
attempts to bound).
The value "64" is justified in Appendix A.4 of the current 90C draft,
and aligns with NIST's in "epsilon" definition in this document, which is
that a string can be considered "full entropy" if you can bound the min
entropy in each bit of output to at least 1-epsilon, where epsilon is
required to be <= 2^(-32).
Note, this patch causes the Jitter RNG to cut its performance in half in
FIPS mode because the conditioning function of the LFSR produces 64 bits
of entropy in one block. The oversampling requires that additionally 64
bits of entropy are sampled from the noise source. If the conditioner is
changed, such as using SHA-256, the impact of the oversampling is only
one fourth, because for the 256 bit block of the conditioner, only 64
additional bits from the noise source must be sampled.
This patch is derived from the user space jitterentropy-library.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2021-12-20 06:21:53 +00:00
/*
* The output n bits can receive more than n bits of min entropy , of course ,
* but the fixed output of the conditioning function can only asymptotically
* approach the output size bits of min entropy , not attain that bound . Random
* maps will tend to have output collisions , which reduces the creditable
* output entropy ( that is what SP 800 - 90 B Section 3.1 .5 .1 .2 attempts to bound ) .
*
* The value " 64 " is justified in Appendix A .4 of the current 90 C draft ,
* and aligns with NIST ' s in " epsilon " definition in this document , which is
* that a string can be considered " full entropy " if you can bound the min
* entropy in each bit of output to at least 1 - epsilon , where epsilon is
* required to be < = 2 ^ ( - 32 ) .
*/
# define JENT_ENTROPY_SAFETY_FACTOR 64
# include <linux/fips.h>
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# include <linux/minmax.h>
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# include "jitterentropy.h"
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/***************************************************************************
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* Adaptive Proportion Test
*
* This test complies with SP800 - 90 B section 4.4 .2 .
2015-05-25 13:10:20 +00:00
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
2023-09-21 11:48:11 +00:00
/*
* See the SP 800 - 90 B comment # 10 b for the corrected cutoff for the SP 800 - 90 B
* APT .
2024-03-29 15:53:45 +00:00
* https : //www.untruth.org/~josh/sp80090b/UL%20SP800-90B-final%20comments%20v1.9%2020191212.pdf
2024-03-29 15:44:54 +00:00
* In the syntax of R , this is C = 2 + qbinom ( 1 − 2 ^ ( − 30 ) , 511 , 2 ^ ( - 1 / osr ) ) .
2023-09-21 11:48:11 +00:00
* ( The original formula wasn ' t correct because the first symbol must
* necessarily have been observed , so there is no chance of observing 0 of these
* symbols . )
*
* For the alpha < 2 ^ - 53 , R cannot be used as it uses a float data type without
* arbitrary precision . A SageMath script is used to calculate those cutoff
* values .
*
* For any value above 14 , this yields the maximal allowable value of 512
* ( by FIPS 140 - 2 IG 7.19 Resolution # 16 , we cannot choose a cutoff value that
* renders the test unable to fail ) .
*/
static const unsigned int jent_apt_cutoff_lookup [ 15 ] = {
325 , 422 , 459 , 477 , 488 , 494 , 499 , 502 ,
505 , 507 , 508 , 509 , 510 , 511 , 512 } ;
static const unsigned int jent_apt_cutoff_permanent_lookup [ 15 ] = {
355 , 447 , 479 , 494 , 502 , 507 , 510 , 512 ,
512 , 512 , 512 , 512 , 512 , 512 , 512 } ;
# define ARRAY_SIZE(x) (sizeof(x) / sizeof((x)[0]))
static void jent_apt_init ( struct rand_data * ec , unsigned int osr )
{
/*
* Establish the apt_cutoff based on the presumed entropy rate of
* 1 / osr .
*/
if ( osr > = ARRAY_SIZE ( jent_apt_cutoff_lookup ) ) {
ec - > apt_cutoff = jent_apt_cutoff_lookup [
ARRAY_SIZE ( jent_apt_cutoff_lookup ) - 1 ] ;
ec - > apt_cutoff_permanent = jent_apt_cutoff_permanent_lookup [
ARRAY_SIZE ( jent_apt_cutoff_permanent_lookup ) - 1 ] ;
} else {
ec - > apt_cutoff = jent_apt_cutoff_lookup [ osr - 1 ] ;
ec - > apt_cutoff_permanent =
jent_apt_cutoff_permanent_lookup [ osr - 1 ] ;
}
}
2021-08-24 21:05:13 +00:00
/*
2020-04-17 19:33:33 +00:00
* Reset the APT counter
*
* @ ec [ in ] Reference to entropy collector
*/
static void jent_apt_reset ( struct rand_data * ec , unsigned int delta_masked )
{
/* Reset APT counter */
ec - > apt_count = 0 ;
ec - > apt_base = delta_masked ;
ec - > apt_observations = 0 ;
}
2021-08-24 21:05:13 +00:00
/*
2020-04-17 19:33:33 +00:00
* Insert a new entropy event into APT
*
* @ ec [ in ] Reference to entropy collector
* @ delta_masked [ in ] Masked time delta to process
*/
static void jent_apt_insert ( struct rand_data * ec , unsigned int delta_masked )
{
/* Initialize the base reference */
if ( ! ec - > apt_base_set ) {
ec - > apt_base = delta_masked ;
ec - > apt_base_set = 1 ;
return ;
}
2023-10-19 07:40:42 +00:00
if ( delta_masked = = ec - > apt_base ) {
2020-04-17 19:33:33 +00:00
ec - > apt_count + + ;
2023-10-19 07:40:42 +00:00
/* Note, ec->apt_count starts with one. */
if ( ec - > apt_count > = ec - > apt_cutoff_permanent )
ec - > health_failure | = JENT_APT_FAILURE_PERMANENT ;
else if ( ec - > apt_count > = ec - > apt_cutoff )
ec - > health_failure | = JENT_APT_FAILURE ;
}
2020-04-17 19:33:33 +00:00
ec - > apt_observations + + ;
if ( ec - > apt_observations > = JENT_APT_WINDOW_SIZE )
jent_apt_reset ( ec , delta_masked ) ;
}
/***************************************************************************
* Stuck Test and its use as Repetition Count Test
*
* The Jitter RNG uses an enhanced version of the Repetition Count Test
* ( RCT ) specified in SP800 - 90 B section 4.4 .1 . Instead of counting identical
* back - to - back values , the input to the RCT is the counting of the stuck
* values during the generation of one Jitter RNG output block .
*
* The RCT is applied with an alpha of 2 ^ { - 30 } compliant to FIPS 140 - 2 IG 9.8 .
*
* During the counting operation , the Jitter RNG always calculates the RCT
* cut - off value of C . If that value exceeds the allowed cut - off value ,
* the Jitter RNG output block will be calculated completely but discarded at
* the end . The caller of the Jitter RNG is informed with an error code .
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
2021-08-24 21:05:13 +00:00
/*
2020-04-17 19:33:33 +00:00
* Repetition Count Test as defined in SP800 - 90 B section 4.4 .1
*
* @ ec [ in ] Reference to entropy collector
* @ stuck [ in ] Indicator whether the value is stuck
*/
static void jent_rct_insert ( struct rand_data * ec , int stuck )
{
if ( stuck ) {
ec - > rct_count + + ;
2023-10-19 07:40:42 +00:00
/*
* The cutoff value is based on the following consideration :
* alpha = 2 ^ - 30 or 2 ^ - 60 as recommended in SP800 - 90 B .
* In addition , we require an entropy value H of 1 / osr as this
* is the minimum entropy required to provide full entropy .
* Note , we collect ( DATA_SIZE_BITS + ENTROPY_SAFETY_FACTOR ) * osr
* deltas for inserting them into the entropy pool which should
* then have ( close to ) DATA_SIZE_BITS bits of entropy in the
* conditioned output .
*
* Note , ec - > rct_count ( which equals to value B in the pseudo
* code of SP800 - 90 B section 4.4 .1 ) starts with zero . Hence
* we need to subtract one from the cutoff value as calculated
* following SP800 - 90 B . Thus C = ceil ( - log_2 ( alpha ) / H ) = 30 * osr
* or 60 * osr .
*/
if ( ( unsigned int ) ec - > rct_count > = ( 60 * ec - > osr ) ) {
ec - > rct_count = - 1 ;
ec - > health_failure | = JENT_RCT_FAILURE_PERMANENT ;
} else if ( ( unsigned int ) ec - > rct_count > = ( 30 * ec - > osr ) ) {
ec - > rct_count = - 1 ;
ec - > health_failure | = JENT_RCT_FAILURE ;
}
2020-04-17 19:33:33 +00:00
} else {
crypto: jitter - permanent and intermittent health errors
According to SP800-90B, two health failures are allowed: the intermittend
and the permanent failure. So far, only the intermittent failure was
implemented. The permanent failure was achieved by resetting the entire
entropy source including its health test state and waiting for two or
more back-to-back health errors.
This approach is appropriate for RCT, but not for APT as APT has a
non-linear cutoff value. Thus, this patch implements 2 cutoff values
for both RCT/APT. This implies that the health state is left untouched
when an intermittent failure occurs. The noise source is reset
and a new APT powerup-self test is performed. Yet, whith the unchanged
health test state, the counting of failures continues until a permanent
failure is reached.
Any non-failing raw entropy value causes the health tests to reset.
The intermittent error has an unchanged significance level of 2^-30.
The permanent error has a significance level of 2^-60. Considering that
this level also indicates a false-positive rate (see SP800-90B section 4.2)
a false-positive must only be incurred with a low probability when
considering a fleet of Linux kernels as a whole. Hitting the permanent
error may cause a panic(), the following calculation applies: Assuming
that a fleet of 10^9 Linux kernels run concurrently with this patch in
FIPS mode and on each kernel 2 health tests are performed every minute
for one year, the chances of a false positive is about 1:1000
based on the binomial distribution.
In addition, any power-up health test errors triggered with
jent_entropy_init are treated as permanent errors.
A permanent failure causes the entire entropy source to permanently
return an error. This implies that a caller can only remedy the situation
by re-allocating a new instance of the Jitter RNG. In a subsequent
patch, a transparent re-allocation will be provided which also changes
the implied heuristic entropy assessment.
In addition, when the kernel is booted with fips=1, the Jitter RNG
is defined to be part of a FIPS module. The permanent error of the
Jitter RNG is translated as a FIPS module error. In this case, the entire
FIPS module must cease operation. This is implemented in the kernel by
invoking panic().
The patch also fixes an off-by-one in the RCT cutoff value which is now
set to 30 instead of 31. This is because the counting of the values
starts with 0.
Reviewed-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Reviewed-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-03-27 07:03:52 +00:00
/* Reset RCT */
2020-04-17 19:33:33 +00:00
ec - > rct_count = 0 ;
}
}
static inline __u64 jent_delta ( __u64 prev , __u64 next )
{
# define JENT_UINT64_MAX (__u64)(~((__u64) 0))
return ( prev < next ) ? ( next - prev ) :
( JENT_UINT64_MAX - prev + 1 + next ) ;
}
2021-08-24 21:05:13 +00:00
/*
2020-04-17 19:33:33 +00:00
* Stuck test by checking the :
* 1 st derivative of the jitter measurement ( time delta )
* 2 nd derivative of the jitter measurement ( delta of time deltas )
* 3 rd derivative of the jitter measurement ( delta of delta of time deltas )
*
* All values must always be non - zero .
*
* @ ec [ in ] Reference to entropy collector
* @ current_delta [ in ] Jitter time delta
*
* @ return
* 0 jitter measurement not stuck ( good bit )
* 1 jitter measurement stuck ( reject bit )
*/
static int jent_stuck ( struct rand_data * ec , __u64 current_delta )
{
__u64 delta2 = jent_delta ( ec - > last_delta , current_delta ) ;
__u64 delta3 = jent_delta ( ec - > last_delta2 , delta2 ) ;
ec - > last_delta = current_delta ;
ec - > last_delta2 = delta2 ;
/*
* Insert the result of the comparison of two back - to - back time
* deltas .
*/
2021-11-21 14:14:20 +00:00
jent_apt_insert ( ec , current_delta ) ;
2020-04-17 19:33:33 +00:00
if ( ! current_delta | | ! delta2 | | ! delta3 ) {
/* RCT with a stuck bit */
jent_rct_insert ( ec , 1 ) ;
return 1 ;
}
/* RCT with a non-stuck bit */
jent_rct_insert ( ec , 0 ) ;
return 0 ;
}
2023-09-21 11:48:11 +00:00
/*
2023-10-19 07:40:42 +00:00
* Report any health test failures
*
* @ ec [ in ] Reference to entropy collector
*
* @ return a bitmask indicating which tests failed
* 0 No health test failure
* 1 RCT failure
* 2 APT failure
* 1 < < JENT_PERMANENT_FAILURE_SHIFT RCT permanent failure
* 2 < < JENT_PERMANENT_FAILURE_SHIFT APT permanent failure
2023-09-21 11:48:11 +00:00
*/
2023-10-19 07:40:42 +00:00
static unsigned int jent_health_failure ( struct rand_data * ec )
crypto: jitter - permanent and intermittent health errors
According to SP800-90B, two health failures are allowed: the intermittend
and the permanent failure. So far, only the intermittent failure was
implemented. The permanent failure was achieved by resetting the entire
entropy source including its health test state and waiting for two or
more back-to-back health errors.
This approach is appropriate for RCT, but not for APT as APT has a
non-linear cutoff value. Thus, this patch implements 2 cutoff values
for both RCT/APT. This implies that the health state is left untouched
when an intermittent failure occurs. The noise source is reset
and a new APT powerup-self test is performed. Yet, whith the unchanged
health test state, the counting of failures continues until a permanent
failure is reached.
Any non-failing raw entropy value causes the health tests to reset.
The intermittent error has an unchanged significance level of 2^-30.
The permanent error has a significance level of 2^-60. Considering that
this level also indicates a false-positive rate (see SP800-90B section 4.2)
a false-positive must only be incurred with a low probability when
considering a fleet of Linux kernels as a whole. Hitting the permanent
error may cause a panic(), the following calculation applies: Assuming
that a fleet of 10^9 Linux kernels run concurrently with this patch in
FIPS mode and on each kernel 2 health tests are performed every minute
for one year, the chances of a false positive is about 1:1000
based on the binomial distribution.
In addition, any power-up health test errors triggered with
jent_entropy_init are treated as permanent errors.
A permanent failure causes the entire entropy source to permanently
return an error. This implies that a caller can only remedy the situation
by re-allocating a new instance of the Jitter RNG. In a subsequent
patch, a transparent re-allocation will be provided which also changes
the implied heuristic entropy assessment.
In addition, when the kernel is booted with fips=1, the Jitter RNG
is defined to be part of a FIPS module. The permanent error of the
Jitter RNG is translated as a FIPS module error. In this case, the entire
FIPS module must cease operation. This is implemented in the kernel by
invoking panic().
The patch also fixes an off-by-one in the RCT cutoff value which is now
set to 30 instead of 31. This is because the counting of the values
starts with 0.
Reviewed-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Reviewed-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-03-27 07:03:52 +00:00
{
2023-10-19 07:40:42 +00:00
/* Test is only enabled in FIPS mode */
if ( ! fips_enabled )
return 0 ;
crypto: jitter - permanent and intermittent health errors
According to SP800-90B, two health failures are allowed: the intermittend
and the permanent failure. So far, only the intermittent failure was
implemented. The permanent failure was achieved by resetting the entire
entropy source including its health test state and waiting for two or
more back-to-back health errors.
This approach is appropriate for RCT, but not for APT as APT has a
non-linear cutoff value. Thus, this patch implements 2 cutoff values
for both RCT/APT. This implies that the health state is left untouched
when an intermittent failure occurs. The noise source is reset
and a new APT powerup-self test is performed. Yet, whith the unchanged
health test state, the counting of failures continues until a permanent
failure is reached.
Any non-failing raw entropy value causes the health tests to reset.
The intermittent error has an unchanged significance level of 2^-30.
The permanent error has a significance level of 2^-60. Considering that
this level also indicates a false-positive rate (see SP800-90B section 4.2)
a false-positive must only be incurred with a low probability when
considering a fleet of Linux kernels as a whole. Hitting the permanent
error may cause a panic(), the following calculation applies: Assuming
that a fleet of 10^9 Linux kernels run concurrently with this patch in
FIPS mode and on each kernel 2 health tests are performed every minute
for one year, the chances of a false positive is about 1:1000
based on the binomial distribution.
In addition, any power-up health test errors triggered with
jent_entropy_init are treated as permanent errors.
A permanent failure causes the entire entropy source to permanently
return an error. This implies that a caller can only remedy the situation
by re-allocating a new instance of the Jitter RNG. In a subsequent
patch, a transparent re-allocation will be provided which also changes
the implied heuristic entropy assessment.
In addition, when the kernel is booted with fips=1, the Jitter RNG
is defined to be part of a FIPS module. The permanent error of the
Jitter RNG is translated as a FIPS module error. In this case, the entire
FIPS module must cease operation. This is implemented in the kernel by
invoking panic().
The patch also fixes an off-by-one in the RCT cutoff value which is now
set to 30 instead of 31. This is because the counting of the values
starts with 0.
Reviewed-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Reviewed-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-03-27 07:03:52 +00:00
2023-10-19 07:40:42 +00:00
return ec - > health_failure ;
2020-04-17 19:33:33 +00:00
}
/***************************************************************************
* Noise sources
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
2015-05-25 13:10:20 +00:00
2021-08-24 21:05:13 +00:00
/*
2015-05-25 13:10:20 +00:00
* Update of the loop count used for the next round of
* an entropy collection .
*
* Input :
* @ bits is the number of low bits of the timer to consider
* @ min is the number of bits we shift the timer value to the right at
* the end to make sure we have a guaranteed minimum value
*
* @ return Newly calculated loop counter
*/
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
static __u64 jent_loop_shuffle ( unsigned int bits , unsigned int min )
2015-05-25 13:10:20 +00:00
{
__u64 time = 0 ;
__u64 shuffle = 0 ;
unsigned int i = 0 ;
unsigned int mask = ( 1 < < bits ) - 1 ;
jent_get_nstime ( & time ) ;
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
2015-05-25 13:10:20 +00:00
/*
2019-05-29 19:24:25 +00:00
* We fold the time value as much as possible to ensure that as many
* bits of the time stamp are included as possible .
2015-05-25 13:10:20 +00:00
*/
2019-05-29 19:24:25 +00:00
for ( i = 0 ; ( ( DATA_SIZE_BITS + bits - 1 ) / bits ) > i ; i + + ) {
2015-05-25 13:10:20 +00:00
shuffle ^ = time & mask ;
time = time > > bits ;
}
/*
* We add a lower boundary value to ensure we have a minimum
* RNG loop count .
*/
return ( shuffle + ( 1 < < min ) ) ;
}
2021-08-24 21:05:13 +00:00
/*
2015-05-25 13:10:20 +00:00
* CPU Jitter noise source - - this is the noise source based on the CPU
* execution time jitter
*
2019-05-29 19:24:25 +00:00
* This function injects the individual bits of the time value into the
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
* entropy pool using a hash .
2015-05-25 13:10:20 +00:00
*
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
* ec [ in ] entropy collector
* time [ in ] time stamp to be injected
* stuck [ in ] Is the time stamp identified as stuck ?
2015-05-25 13:10:20 +00:00
*
* Output :
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
* updated hash context in the entropy collector or error code
2015-05-25 13:10:20 +00:00
*/
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
static int jent_condition_data ( struct rand_data * ec , __u64 time , int stuck )
2015-05-25 13:10:20 +00:00
{
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
# define SHA3_HASH_LOOP (1<<3)
struct {
int rct_count ;
unsigned int apt_observations ;
unsigned int apt_count ;
unsigned int apt_base ;
} addtl = {
ec - > rct_count ,
ec - > apt_observations ,
ec - > apt_count ,
ec - > apt_base
} ;
return jent_hash_time ( ec - > hash_state , time , ( u8 * ) & addtl , sizeof ( addtl ) ,
SHA3_HASH_LOOP , stuck ) ;
2015-05-25 13:10:20 +00:00
}
2021-08-24 21:05:13 +00:00
/*
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* Memory Access noise source - - this is a noise source based on variations in
* memory access times
*
* This function performs memory accesses which will add to the timing
* variations due to an unknown amount of CPU wait states that need to be
* added when accessing memory . The memory size should be larger than the L1
* caches as outlined in the documentation and the associated testing .
*
* The L1 cache has a very high bandwidth , albeit its access rate is usually
* slower than accessing CPU registers . Therefore , L1 accesses only add minimal
* variations as the CPU has hardly to wait . Starting with L2 , significant
* variations are added because L2 typically does not belong to the CPU any more
* and therefore a wider range of CPU wait states is necessary for accesses .
* L3 and real memory accesses have even a wider range of wait states . However ,
* to reliably access either L3 or memory , the ec - > mem memory must be quite
* large which is usually not desirable .
*
2020-04-17 19:33:33 +00:00
* @ ec [ in ] Reference to the entropy collector with the memory access data - - if
* the reference to the memory block to be accessed is NULL , this noise
* source is disabled
* @ loop_cnt [ in ] if a value not equal to 0 is set , use the given value
* number of loops to perform the LFSR
2015-05-25 13:10:20 +00:00
*/
2020-04-17 19:33:33 +00:00
static void jent_memaccess ( struct rand_data * ec , __u64 loop_cnt )
2015-05-25 13:10:20 +00:00
{
unsigned int wrap = 0 ;
__u64 i = 0 ;
# define MAX_ACC_LOOP_BIT 7
# define MIN_ACC_LOOP_BIT 0
__u64 acc_loop_cnt =
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
jent_loop_shuffle ( MAX_ACC_LOOP_BIT , MIN_ACC_LOOP_BIT ) ;
2015-05-25 13:10:20 +00:00
if ( NULL = = ec | | NULL = = ec - > mem )
2020-04-17 19:33:33 +00:00
return ;
2015-05-25 13:10:20 +00:00
wrap = ec - > memblocksize * ec - > memblocks ;
/*
* testing purposes - - allow test app to set the counter , not
* needed during runtime
*/
if ( loop_cnt )
acc_loop_cnt = loop_cnt ;
for ( i = 0 ; i < ( ec - > memaccessloops + acc_loop_cnt ) ; i + + ) {
2019-05-29 19:24:25 +00:00
unsigned char * tmpval = ec - > mem + ec - > memlocation ;
2015-05-25 13:10:20 +00:00
/*
* memory access : just add 1 to one byte ,
* wrap at 255 - - memory access implies read
* from and write to memory location
*/
* tmpval = ( * tmpval + 1 ) & 0xff ;
/*
* Addition of memblocksize - 1 to pointer
* with wrap around logic to ensure that every
* memory location is hit evenly
*/
ec - > memlocation = ec - > memlocation + ec - > memblocksize - 1 ;
ec - > memlocation = ec - > memlocation % wrap ;
}
}
/***************************************************************************
* Start of entropy processing logic
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
2021-08-24 21:05:13 +00:00
/*
2015-05-25 13:10:20 +00:00
* This is the heart of the entropy generation : calculate time deltas and
2019-05-29 19:24:25 +00:00
* use the CPU jitter in the time deltas . The jitter is injected into the
* entropy pool .
2015-05-25 13:10:20 +00:00
*
* WARNING : ensure that - > prev_time is primed before using the output
* of this function ! This can be done by calling this function
* and not using its result .
*
2020-04-17 19:33:33 +00:00
* @ ec [ in ] Reference to entropy collector
2015-05-25 13:10:20 +00:00
*
2019-05-29 19:24:25 +00:00
* @ return result of stuck test
2015-05-25 13:10:20 +00:00
*/
2023-09-21 11:48:11 +00:00
static int jent_measure_jitter ( struct rand_data * ec , __u64 * ret_current_delta )
2015-05-25 13:10:20 +00:00
{
__u64 time = 0 ;
__u64 current_delta = 0 ;
2020-04-17 19:33:33 +00:00
int stuck ;
2015-05-25 13:10:20 +00:00
/* Invoke one noise source before time measurement to add variations */
jent_memaccess ( ec , 0 ) ;
/*
* Get time stamp and calculate time delta to previous
* invocation to measure the timing variations
*/
jent_get_nstime ( & time ) ;
2020-04-17 19:33:33 +00:00
current_delta = jent_delta ( ec - > prev_time , time ) ;
2015-05-25 13:10:20 +00:00
ec - > prev_time = time ;
2020-04-17 19:33:33 +00:00
/* Check whether we have a stuck measurement. */
stuck = jent_stuck ( ec , current_delta ) ;
2019-05-29 19:24:25 +00:00
/* Now call the next noise sources which also injects the data */
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
if ( jent_condition_data ( ec , current_delta , stuck ) )
stuck = 1 ;
2015-05-25 13:10:20 +00:00
2023-09-21 11:48:11 +00:00
/* return the raw entropy value */
if ( ret_current_delta )
* ret_current_delta = current_delta ;
2020-04-17 19:33:33 +00:00
return stuck ;
2015-05-25 13:10:20 +00:00
}
2021-08-24 21:05:13 +00:00
/*
2015-05-25 13:10:20 +00:00
* Generator of one 64 bit random number
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
* Function fills rand_data - > hash_state
2015-05-25 13:10:20 +00:00
*
2020-04-17 19:33:33 +00:00
* @ ec [ in ] Reference to entropy collector
2015-05-25 13:10:20 +00:00
*/
static void jent_gen_entropy ( struct rand_data * ec )
{
crypto: jitter - add oversampling of noise source
The output n bits can receive more than n bits of min entropy, of course,
but the fixed output of the conditioning function can only asymptotically
approach the output size bits of min entropy, not attain that bound.
Random maps will tend to have output collisions, which reduces the
creditable output entropy (that is what SP 800-90B Section 3.1.5.1.2
attempts to bound).
The value "64" is justified in Appendix A.4 of the current 90C draft,
and aligns with NIST's in "epsilon" definition in this document, which is
that a string can be considered "full entropy" if you can bound the min
entropy in each bit of output to at least 1-epsilon, where epsilon is
required to be <= 2^(-32).
Note, this patch causes the Jitter RNG to cut its performance in half in
FIPS mode because the conditioning function of the LFSR produces 64 bits
of entropy in one block. The oversampling requires that additionally 64
bits of entropy are sampled from the noise source. If the conditioner is
changed, such as using SHA-256, the impact of the oversampling is only
one fourth, because for the 256 bit block of the conditioner, only 64
additional bits from the noise source must be sampled.
This patch is derived from the user space jitterentropy-library.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2021-12-20 06:21:53 +00:00
unsigned int k = 0 , safety_factor = 0 ;
if ( fips_enabled )
safety_factor = JENT_ENTROPY_SAFETY_FACTOR ;
2015-05-25 13:10:20 +00:00
/* priming of the ->prev_time value */
2023-09-21 11:48:11 +00:00
jent_measure_jitter ( ec , NULL ) ;
2015-05-25 13:10:20 +00:00
2021-11-30 14:10:09 +00:00
while ( ! jent_health_failure ( ec ) ) {
2019-05-29 19:24:25 +00:00
/* If a stuck measurement is received, repeat measurement */
2023-09-21 11:48:11 +00:00
if ( jent_measure_jitter ( ec , NULL ) )
2015-05-25 13:10:20 +00:00
continue ;
/*
* We multiply the loop value with - > osr to obtain the
* oversampling rate requested by the caller
*/
crypto: jitter - add oversampling of noise source
The output n bits can receive more than n bits of min entropy, of course,
but the fixed output of the conditioning function can only asymptotically
approach the output size bits of min entropy, not attain that bound.
Random maps will tend to have output collisions, which reduces the
creditable output entropy (that is what SP 800-90B Section 3.1.5.1.2
attempts to bound).
The value "64" is justified in Appendix A.4 of the current 90C draft,
and aligns with NIST's in "epsilon" definition in this document, which is
that a string can be considered "full entropy" if you can bound the min
entropy in each bit of output to at least 1-epsilon, where epsilon is
required to be <= 2^(-32).
Note, this patch causes the Jitter RNG to cut its performance in half in
FIPS mode because the conditioning function of the LFSR produces 64 bits
of entropy in one block. The oversampling requires that additionally 64
bits of entropy are sampled from the noise source. If the conditioner is
changed, such as using SHA-256, the impact of the oversampling is only
one fourth, because for the 256 bit block of the conditioner, only 64
additional bits from the noise source must be sampled.
This patch is derived from the user space jitterentropy-library.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Reviewed-by: Simo Sorce <simo@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2021-12-20 06:21:53 +00:00
if ( + + k > = ( ( DATA_SIZE_BITS + safety_factor ) * ec - > osr ) )
2015-05-25 13:10:20 +00:00
break ;
}
}
2021-08-24 21:05:13 +00:00
/*
2015-05-25 13:10:20 +00:00
* Entry function : Obtain entropy for the caller .
*
* This function invokes the entropy gathering logic as often to generate
* as many bytes as requested by the caller . The entropy gathering logic
* creates 64 bit per invocation .
*
* This function truncates the last 64 bit entropy value output to the exact
* size specified by the caller .
*
2020-04-17 19:33:33 +00:00
* @ ec [ in ] Reference to entropy collector
* @ data [ in ] pointer to buffer for storing random data - - buffer must already
* exist
* @ len [ in ] size of the buffer , specifying also the requested number of random
* in bytes
2015-05-25 13:10:20 +00:00
*
* @ return 0 when request is fulfilled or an error
*
* The following error codes can occur :
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
* - 1 entropy_collector is NULL or the generation failed
crypto: jitter - permanent and intermittent health errors
According to SP800-90B, two health failures are allowed: the intermittend
and the permanent failure. So far, only the intermittent failure was
implemented. The permanent failure was achieved by resetting the entire
entropy source including its health test state and waiting for two or
more back-to-back health errors.
This approach is appropriate for RCT, but not for APT as APT has a
non-linear cutoff value. Thus, this patch implements 2 cutoff values
for both RCT/APT. This implies that the health state is left untouched
when an intermittent failure occurs. The noise source is reset
and a new APT powerup-self test is performed. Yet, whith the unchanged
health test state, the counting of failures continues until a permanent
failure is reached.
Any non-failing raw entropy value causes the health tests to reset.
The intermittent error has an unchanged significance level of 2^-30.
The permanent error has a significance level of 2^-60. Considering that
this level also indicates a false-positive rate (see SP800-90B section 4.2)
a false-positive must only be incurred with a low probability when
considering a fleet of Linux kernels as a whole. Hitting the permanent
error may cause a panic(), the following calculation applies: Assuming
that a fleet of 10^9 Linux kernels run concurrently with this patch in
FIPS mode and on each kernel 2 health tests are performed every minute
for one year, the chances of a false positive is about 1:1000
based on the binomial distribution.
In addition, any power-up health test errors triggered with
jent_entropy_init are treated as permanent errors.
A permanent failure causes the entire entropy source to permanently
return an error. This implies that a caller can only remedy the situation
by re-allocating a new instance of the Jitter RNG. In a subsequent
patch, a transparent re-allocation will be provided which also changes
the implied heuristic entropy assessment.
In addition, when the kernel is booted with fips=1, the Jitter RNG
is defined to be part of a FIPS module. The permanent error of the
Jitter RNG is translated as a FIPS module error. In this case, the entire
FIPS module must cease operation. This is implemented in the kernel by
invoking panic().
The patch also fixes an off-by-one in the RCT cutoff value which is now
set to 30 instead of 31. This is because the counting of the values
starts with 0.
Reviewed-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Reviewed-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-03-27 07:03:52 +00:00
* - 2 Intermittent health failure
* - 3 Permanent health failure
2015-05-25 13:10:20 +00:00
*/
2015-06-23 14:18:54 +00:00
int jent_read_entropy ( struct rand_data * ec , unsigned char * data ,
unsigned int len )
2015-05-25 13:10:20 +00:00
{
2015-06-23 14:18:54 +00:00
unsigned char * p = data ;
2015-05-25 13:10:20 +00:00
if ( ! ec )
2015-06-23 14:18:54 +00:00
return - 1 ;
2015-05-25 13:10:20 +00:00
2021-03-17 01:44:03 +00:00
while ( len > 0 ) {
2023-10-19 07:40:42 +00:00
unsigned int tocopy , health_test_result ;
2015-05-25 13:10:20 +00:00
jent_gen_entropy ( ec ) ;
2020-04-17 19:33:33 +00:00
2023-10-19 07:40:42 +00:00
health_test_result = jent_health_failure ( ec ) ;
if ( health_test_result > JENT_PERMANENT_FAILURE_SHIFT ) {
2020-04-17 19:33:33 +00:00
/*
crypto: jitter - permanent and intermittent health errors
According to SP800-90B, two health failures are allowed: the intermittend
and the permanent failure. So far, only the intermittent failure was
implemented. The permanent failure was achieved by resetting the entire
entropy source including its health test state and waiting for two or
more back-to-back health errors.
This approach is appropriate for RCT, but not for APT as APT has a
non-linear cutoff value. Thus, this patch implements 2 cutoff values
for both RCT/APT. This implies that the health state is left untouched
when an intermittent failure occurs. The noise source is reset
and a new APT powerup-self test is performed. Yet, whith the unchanged
health test state, the counting of failures continues until a permanent
failure is reached.
Any non-failing raw entropy value causes the health tests to reset.
The intermittent error has an unchanged significance level of 2^-30.
The permanent error has a significance level of 2^-60. Considering that
this level also indicates a false-positive rate (see SP800-90B section 4.2)
a false-positive must only be incurred with a low probability when
considering a fleet of Linux kernels as a whole. Hitting the permanent
error may cause a panic(), the following calculation applies: Assuming
that a fleet of 10^9 Linux kernels run concurrently with this patch in
FIPS mode and on each kernel 2 health tests are performed every minute
for one year, the chances of a false positive is about 1:1000
based on the binomial distribution.
In addition, any power-up health test errors triggered with
jent_entropy_init are treated as permanent errors.
A permanent failure causes the entire entropy source to permanently
return an error. This implies that a caller can only remedy the situation
by re-allocating a new instance of the Jitter RNG. In a subsequent
patch, a transparent re-allocation will be provided which also changes
the implied heuristic entropy assessment.
In addition, when the kernel is booted with fips=1, the Jitter RNG
is defined to be part of a FIPS module. The permanent error of the
Jitter RNG is translated as a FIPS module error. In this case, the entire
FIPS module must cease operation. This is implemented in the kernel by
invoking panic().
The patch also fixes an off-by-one in the RCT cutoff value which is now
set to 30 instead of 31. This is because the counting of the values
starts with 0.
Reviewed-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Reviewed-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-03-27 07:03:52 +00:00
* At this point , the Jitter RNG instance is considered
* as a failed instance . There is no rerun of the
* startup test any more , because the caller
* is assumed to not further use this instance .
2020-04-17 19:33:33 +00:00
*/
crypto: jitter - permanent and intermittent health errors
According to SP800-90B, two health failures are allowed: the intermittend
and the permanent failure. So far, only the intermittent failure was
implemented. The permanent failure was achieved by resetting the entire
entropy source including its health test state and waiting for two or
more back-to-back health errors.
This approach is appropriate for RCT, but not for APT as APT has a
non-linear cutoff value. Thus, this patch implements 2 cutoff values
for both RCT/APT. This implies that the health state is left untouched
when an intermittent failure occurs. The noise source is reset
and a new APT powerup-self test is performed. Yet, whith the unchanged
health test state, the counting of failures continues until a permanent
failure is reached.
Any non-failing raw entropy value causes the health tests to reset.
The intermittent error has an unchanged significance level of 2^-30.
The permanent error has a significance level of 2^-60. Considering that
this level also indicates a false-positive rate (see SP800-90B section 4.2)
a false-positive must only be incurred with a low probability when
considering a fleet of Linux kernels as a whole. Hitting the permanent
error may cause a panic(), the following calculation applies: Assuming
that a fleet of 10^9 Linux kernels run concurrently with this patch in
FIPS mode and on each kernel 2 health tests are performed every minute
for one year, the chances of a false positive is about 1:1000
based on the binomial distribution.
In addition, any power-up health test errors triggered with
jent_entropy_init are treated as permanent errors.
A permanent failure causes the entire entropy source to permanently
return an error. This implies that a caller can only remedy the situation
by re-allocating a new instance of the Jitter RNG. In a subsequent
patch, a transparent re-allocation will be provided which also changes
the implied heuristic entropy assessment.
In addition, when the kernel is booted with fips=1, the Jitter RNG
is defined to be part of a FIPS module. The permanent error of the
Jitter RNG is translated as a FIPS module error. In this case, the entire
FIPS module must cease operation. This is implemented in the kernel by
invoking panic().
The patch also fixes an off-by-one in the RCT cutoff value which is now
set to 30 instead of 31. This is because the counting of the values
starts with 0.
Reviewed-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Reviewed-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-03-27 07:03:52 +00:00
return - 3 ;
2023-10-19 07:40:42 +00:00
} else if ( health_test_result ) {
2020-04-17 19:33:33 +00:00
/*
crypto: jitter - permanent and intermittent health errors
According to SP800-90B, two health failures are allowed: the intermittend
and the permanent failure. So far, only the intermittent failure was
implemented. The permanent failure was achieved by resetting the entire
entropy source including its health test state and waiting for two or
more back-to-back health errors.
This approach is appropriate for RCT, but not for APT as APT has a
non-linear cutoff value. Thus, this patch implements 2 cutoff values
for both RCT/APT. This implies that the health state is left untouched
when an intermittent failure occurs. The noise source is reset
and a new APT powerup-self test is performed. Yet, whith the unchanged
health test state, the counting of failures continues until a permanent
failure is reached.
Any non-failing raw entropy value causes the health tests to reset.
The intermittent error has an unchanged significance level of 2^-30.
The permanent error has a significance level of 2^-60. Considering that
this level also indicates a false-positive rate (see SP800-90B section 4.2)
a false-positive must only be incurred with a low probability when
considering a fleet of Linux kernels as a whole. Hitting the permanent
error may cause a panic(), the following calculation applies: Assuming
that a fleet of 10^9 Linux kernels run concurrently with this patch in
FIPS mode and on each kernel 2 health tests are performed every minute
for one year, the chances of a false positive is about 1:1000
based on the binomial distribution.
In addition, any power-up health test errors triggered with
jent_entropy_init are treated as permanent errors.
A permanent failure causes the entire entropy source to permanently
return an error. This implies that a caller can only remedy the situation
by re-allocating a new instance of the Jitter RNG. In a subsequent
patch, a transparent re-allocation will be provided which also changes
the implied heuristic entropy assessment.
In addition, when the kernel is booted with fips=1, the Jitter RNG
is defined to be part of a FIPS module. The permanent error of the
Jitter RNG is translated as a FIPS module error. In this case, the entire
FIPS module must cease operation. This is implemented in the kernel by
invoking panic().
The patch also fixes an off-by-one in the RCT cutoff value which is now
set to 30 instead of 31. This is because the counting of the values
starts with 0.
Reviewed-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Reviewed-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-03-27 07:03:52 +00:00
* Perform startup health tests and return permanent
* error if it fails .
2020-04-17 19:33:33 +00:00
*/
2023-10-19 07:40:42 +00:00
if ( jent_entropy_init ( 0 , 0 , NULL , ec ) ) {
/* Mark the permanent error */
ec - > health_failure & =
JENT_RCT_FAILURE_PERMANENT |
JENT_APT_FAILURE_PERMANENT ;
crypto: jitter - permanent and intermittent health errors
According to SP800-90B, two health failures are allowed: the intermittend
and the permanent failure. So far, only the intermittent failure was
implemented. The permanent failure was achieved by resetting the entire
entropy source including its health test state and waiting for two or
more back-to-back health errors.
This approach is appropriate for RCT, but not for APT as APT has a
non-linear cutoff value. Thus, this patch implements 2 cutoff values
for both RCT/APT. This implies that the health state is left untouched
when an intermittent failure occurs. The noise source is reset
and a new APT powerup-self test is performed. Yet, whith the unchanged
health test state, the counting of failures continues until a permanent
failure is reached.
Any non-failing raw entropy value causes the health tests to reset.
The intermittent error has an unchanged significance level of 2^-30.
The permanent error has a significance level of 2^-60. Considering that
this level also indicates a false-positive rate (see SP800-90B section 4.2)
a false-positive must only be incurred with a low probability when
considering a fleet of Linux kernels as a whole. Hitting the permanent
error may cause a panic(), the following calculation applies: Assuming
that a fleet of 10^9 Linux kernels run concurrently with this patch in
FIPS mode and on each kernel 2 health tests are performed every minute
for one year, the chances of a false positive is about 1:1000
based on the binomial distribution.
In addition, any power-up health test errors triggered with
jent_entropy_init are treated as permanent errors.
A permanent failure causes the entire entropy source to permanently
return an error. This implies that a caller can only remedy the situation
by re-allocating a new instance of the Jitter RNG. In a subsequent
patch, a transparent re-allocation will be provided which also changes
the implied heuristic entropy assessment.
In addition, when the kernel is booted with fips=1, the Jitter RNG
is defined to be part of a FIPS module. The permanent error of the
Jitter RNG is translated as a FIPS module error. In this case, the entire
FIPS module must cease operation. This is implemented in the kernel by
invoking panic().
The patch also fixes an off-by-one in the RCT cutoff value which is now
set to 30 instead of 31. This is because the counting of the values
starts with 0.
Reviewed-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Reviewed-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-03-27 07:03:52 +00:00
return - 3 ;
2023-10-19 07:40:42 +00:00
}
crypto: jitter - permanent and intermittent health errors
According to SP800-90B, two health failures are allowed: the intermittend
and the permanent failure. So far, only the intermittent failure was
implemented. The permanent failure was achieved by resetting the entire
entropy source including its health test state and waiting for two or
more back-to-back health errors.
This approach is appropriate for RCT, but not for APT as APT has a
non-linear cutoff value. Thus, this patch implements 2 cutoff values
for both RCT/APT. This implies that the health state is left untouched
when an intermittent failure occurs. The noise source is reset
and a new APT powerup-self test is performed. Yet, whith the unchanged
health test state, the counting of failures continues until a permanent
failure is reached.
Any non-failing raw entropy value causes the health tests to reset.
The intermittent error has an unchanged significance level of 2^-30.
The permanent error has a significance level of 2^-60. Considering that
this level also indicates a false-positive rate (see SP800-90B section 4.2)
a false-positive must only be incurred with a low probability when
considering a fleet of Linux kernels as a whole. Hitting the permanent
error may cause a panic(), the following calculation applies: Assuming
that a fleet of 10^9 Linux kernels run concurrently with this patch in
FIPS mode and on each kernel 2 health tests are performed every minute
for one year, the chances of a false positive is about 1:1000
based on the binomial distribution.
In addition, any power-up health test errors triggered with
jent_entropy_init are treated as permanent errors.
A permanent failure causes the entire entropy source to permanently
return an error. This implies that a caller can only remedy the situation
by re-allocating a new instance of the Jitter RNG. In a subsequent
patch, a transparent re-allocation will be provided which also changes
the implied heuristic entropy assessment.
In addition, when the kernel is booted with fips=1, the Jitter RNG
is defined to be part of a FIPS module. The permanent error of the
Jitter RNG is translated as a FIPS module error. In this case, the entire
FIPS module must cease operation. This is implemented in the kernel by
invoking panic().
The patch also fixes an off-by-one in the RCT cutoff value which is now
set to 30 instead of 31. This is because the counting of the values
starts with 0.
Reviewed-by: Vladis Dronov <vdronov@redhat.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Reviewed-by: Marcelo Henrique Cerri <marcelo.cerri@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-03-27 07:03:52 +00:00
return - 2 ;
2020-04-17 19:33:33 +00:00
}
2024-08-19 14:18:44 +00:00
tocopy = min ( DATA_SIZE_BITS / 8 , len ) ;
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
if ( jent_read_random_block ( ec - > hash_state , p , tocopy ) )
return - 1 ;
2015-05-25 13:10:20 +00:00
len - = tocopy ;
p + = tocopy ;
}
return 0 ;
}
/***************************************************************************
* Initialization logic
* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
2015-06-23 14:18:54 +00:00
struct rand_data * jent_entropy_collector_alloc ( unsigned int osr ,
crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2023-04-21 06:08:04 +00:00
unsigned int flags ,
void * hash_state )
2015-05-25 13:10:20 +00:00
{
struct rand_data * entropy_collector ;
2015-06-23 14:18:54 +00:00
entropy_collector = jent_zalloc ( sizeof ( struct rand_data ) ) ;
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if ( ! entropy_collector )
return NULL ;
if ( ! ( flags & JENT_DISABLE_MEMORY_ACCESS ) ) {
/* Allocate memory for adding variations based on memory
* access
*/
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entropy_collector - > mem = jent_kvzalloc ( JENT_MEMORY_SIZE ) ;
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if ( ! entropy_collector - > mem ) {
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jent_zfree ( entropy_collector ) ;
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return NULL ;
}
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entropy_collector - > memblocksize =
CONFIG_CRYPTO_JITTERENTROPY_MEMORY_BLOCKSIZE ;
entropy_collector - > memblocks =
CONFIG_CRYPTO_JITTERENTROPY_MEMORY_BLOCKS ;
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entropy_collector - > memaccessloops = JENT_MEMORY_ACCESSLOOPS ;
}
/* verify and set the oversampling rate */
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if ( osr = = 0 )
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osr = 1 ; /* H_submitter = 1 / osr */
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entropy_collector - > osr = osr ;
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entropy_collector - > flags = flags ;
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crypto: jitter - replace LFSR with SHA3-256
Using the kernel crypto API, the SHA3-256 algorithm is used as
conditioning element to replace the LFSR in the Jitter RNG. All other
parts of the Jitter RNG are unchanged.
The application and use of the SHA-3 conditioning operation is identical
to the user space Jitter RNG 3.4.0 by applying the following concept:
- the Jitter RNG initializes a SHA-3 state which acts as the "entropy
pool" when the Jitter RNG is allocated.
- When a new time delta is obtained, it is inserted into the "entropy
pool" with a SHA-3 update operation. Note, this operation in most of
the cases is a simple memcpy() onto the SHA-3 stack.
- To cause a true SHA-3 operation for each time delta operation, a
second SHA-3 operation is performed hashing Jitter RNG status
information. The final message digest is also inserted into the
"entropy pool" with a SHA-3 update operation. Yet, this data is not
considered to provide any entropy, but it shall stir the entropy pool.
- To generate a random number, a SHA-3 final operation is performed to
calculate a message digest followed by an immediate SHA-3 init to
re-initialize the "entropy pool". The obtained message digest is one
block of the Jitter RNG that is returned to the caller.
Mathematically speaking, the random number generated by the Jitter RNG
is:
aux_t = SHA-3(Jitter RNG state data)
Jitter RNG block = SHA-3(time_i || aux_i || time_(i-1) || aux_(i-1) ||
... || time_(i-255) || aux_(i-255))
when assuming that the OSR = 1, i.e. the default value.
This operation implies that the Jitter RNG has an output-blocksize of
256 bits instead of the 64 bits of the LFSR-based Jitter RNG that is
replaced with this patch.
The patch also replaces the varying number of invocations of the
conditioning function with one fixed number of invocations. The use
of the conditioning function consistent with the userspace Jitter RNG
library version 3.4.0.
The code is tested with a system that exhibited the least amount of
entropy generated by the Jitter RNG: the SiFive Unmatched RISC-V
system. The measured entropy rate is well above the heuristically
implied entropy value of 1 bit of entropy per time delta. On all other
tested systems, the measured entropy rate is even higher by orders
of magnitude. The measurement was performed using updated tooling
provided with the user space Jitter RNG library test framework.
The performance of the Jitter RNG with this patch is about en par
with the performance of the Jitter RNG without the patch.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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entropy_collector - > hash_state = hash_state ;
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/* Initialize the APT */
jent_apt_init ( entropy_collector , osr ) ;
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/* fill the data pad with non-zero values */
jent_gen_entropy ( entropy_collector ) ;
return entropy_collector ;
}
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void jent_entropy_collector_free ( struct rand_data * entropy_collector )
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{
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jent_kvzfree ( entropy_collector - > mem , JENT_MEMORY_SIZE ) ;
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entropy_collector - > mem = NULL ;
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jent_zfree ( entropy_collector ) ;
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}
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int jent_entropy_init ( unsigned int osr , unsigned int flags , void * hash_state ,
struct rand_data * p_ec )
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{
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/*
* If caller provides an allocated ec , reuse it which implies that the
* health test entropy data is used to further still the available
* entropy pool .
*/
struct rand_data * ec = p_ec ;
int i , time_backwards = 0 , ret = 0 , ec_free = 0 ;
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unsigned int health_test_result ;
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if ( ! ec ) {
ec = jent_entropy_collector_alloc ( osr , flags , hash_state ) ;
if ( ! ec )
return JENT_EMEM ;
ec_free = 1 ;
} else {
/* Reset the APT */
jent_apt_reset ( ec , 0 ) ;
/* Ensure that a new APT base is obtained */
ec - > apt_base_set = 0 ;
/* Reset the RCT */
ec - > rct_count = 0 ;
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/* Reset intermittent, leave permanent health test result */
ec - > health_failure & = ( ~ JENT_RCT_FAILURE ) ;
ec - > health_failure & = ( ~ JENT_APT_FAILURE ) ;
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}
2020-04-17 19:33:33 +00:00
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/* We could perform statistical tests here, but the problem is
* that we only have a few loop counts to do testing . These
* loop counts may show some slight skew and we produce
* false positives .
*
* Moreover , only old systems show potentially problematic
* jitter entropy that could potentially be caught here . But
* the RNG is intended for hardware that is available or widely
* used , but not old systems that are long out of favor . Thus ,
* no statistical tests .
*/
/*
* We could add a check for system capabilities such as clock_getres or
* check for CONFIG_X86_TSC , but it does not make much sense as the
* following sanity checks verify that we have a high - resolution
* timer .
*/
/*
* TESTLOOPCOUNT needs some loops to identify edge systems . 100 is
* definitely too little .
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*
* SP800 - 90 B requires at least 1024 initial test cycles .
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*/
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# define TESTLOOPCOUNT 1024
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# define CLEARCACHE 100
for ( i = 0 ; ( TESTLOOPCOUNT + CLEARCACHE ) > i ; i + + ) {
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__u64 start_time = 0 , end_time = 0 , delta = 0 ;
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2019-05-29 19:24:25 +00:00
/* Invoke core entropy collection logic */
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jent_measure_jitter ( ec , & delta ) ;
end_time = ec - > prev_time ;
start_time = ec - > prev_time - delta ;
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/* test whether timer works */
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if ( ! start_time | | ! end_time ) {
ret = JENT_ENOTIME ;
goto out ;
}
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/*
* test whether timer is fine grained enough to provide
* delta even when called shortly after each other - - this
* implies that we also have a high resolution timer
*/
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if ( ! delta | | ( end_time = = start_time ) ) {
ret = JENT_ECOARSETIME ;
goto out ;
}
2019-05-29 19:24:25 +00:00
2015-05-25 13:10:20 +00:00
/*
* up to here we did not modify any variable that will be
* evaluated later , but we already performed some work . Thus we
* already have had an impact on the caches , branch prediction ,
* etc . with the goal to clear it to get the worst case
* measurements .
*/
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if ( i < CLEARCACHE )
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continue ;
/* test whether we have an increasing timer */
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if ( ! ( end_time > start_time ) )
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time_backwards + + ;
}
/*
* we allow up to three times the time running backwards .
* CLOCK_REALTIME is affected by adjtime and NTP operations . Thus ,
* if such an operation just happens to interfere with our test , it
* should not fail . The value of 3 should cover the NTP case being
* performed during our test run .
*/
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if ( time_backwards > 3 ) {
ret = JENT_ENOMONOTONIC ;
goto out ;
}
2015-05-25 13:10:20 +00:00
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/* Did we encounter a health test failure? */
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health_test_result = jent_health_failure ( ec ) ;
if ( health_test_result ) {
ret = ( health_test_result & JENT_RCT_FAILURE ) ? JENT_ERCT :
JENT_EHEALTH ;
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goto out ;
}
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out :
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if ( ec_free )
jent_entropy_collector_free ( ec ) ;
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return ret ;
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}
