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crypto: chacha20 - Fix keystream alignment for chacha20_block()

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When chacha20_block() outputs the keystream block, it uses 'u32' stores
directly.  However, the callers (crypto/chacha20_generic.c and
drivers/char/random.c) declare the keystream buffer as a 'u8' array,
which is not guaranteed to have the needed alignment.

Fix it by having both callers declare the keystream as a 'u32' array.
For now this is preferable to switching over to the unaligned access
macros because chacha20_block() is only being used in cases where we can
easily control the alignment (stack buffers).

Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This commit is contained in:
Eric Biggers 2017-11-22 11:51:39 -08:00 committed by Herbert Xu
parent 796c99fbd7
commit 9f480faec5
4 changed files with 18 additions and 17 deletions
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6
crypto/chacha20_generic.c
View File

@ -18,20 +18,20 @@
static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src, static void chacha20_docrypt(u32 *state, u8 *dst, const u8 *src,
unsigned int bytes) unsigned int bytes)
{ {
u8 stream[CHACHA20_BLOCK_SIZE]; u32 stream[CHACHA20_BLOCK_WORDS];
if (dst != src) if (dst != src)
memcpy(dst, src, bytes); memcpy(dst, src, bytes);
while (bytes >= CHACHA20_BLOCK_SIZE) { while (bytes >= CHACHA20_BLOCK_SIZE) {
chacha20_block(state, stream); chacha20_block(state, stream);
crypto_xor(dst, stream, CHACHA20_BLOCK_SIZE); crypto_xor(dst, (const u8 *)stream, CHACHA20_BLOCK_SIZE);
bytes -= CHACHA20_BLOCK_SIZE; bytes -= CHACHA20_BLOCK_SIZE;
dst += CHACHA20_BLOCK_SIZE; dst += CHACHA20_BLOCK_SIZE;
} }
if (bytes) { if (bytes) {
chacha20_block(state, stream); chacha20_block(state, stream);
crypto_xor(dst, stream, bytes); crypto_xor(dst, (const u8 *)stream, bytes);
} }
} }

24
drivers/char/random.c
View File

@ -431,9 +431,9 @@ static int crng_init = 0;
static int crng_init_cnt = 0; static int crng_init_cnt = 0;
#define CRNG_INIT_CNT_THRESH (2*CHACHA20_KEY_SIZE) #define CRNG_INIT_CNT_THRESH (2*CHACHA20_KEY_SIZE)
static void _extract_crng(struct crng_state *crng, static void _extract_crng(struct crng_state *crng,
__u8 out[CHACHA20_BLOCK_SIZE]); __u32 out[CHACHA20_BLOCK_WORDS]);
static void _crng_backtrack_protect(struct crng_state *crng, static void _crng_backtrack_protect(struct crng_state *crng,
__u8 tmp[CHACHA20_BLOCK_SIZE], int used); __u32 tmp[CHACHA20_BLOCK_WORDS], int used);
static void process_random_ready_list(void); static void process_random_ready_list(void);
static void _get_random_bytes(void *buf, int nbytes); static void _get_random_bytes(void *buf, int nbytes);
@ -817,7 +817,7 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
unsigned long flags; unsigned long flags;
int i, num; int i, num;
union { union {
__u8 block[CHACHA20_BLOCK_SIZE]; __u32 block[CHACHA20_BLOCK_WORDS];
__u32 key[8]; __u32 key[8];
} buf; } buf;
@ -851,7 +851,7 @@ static void crng_reseed(struct crng_state *crng, struct entropy_store *r)
} }
static void _extract_crng(struct crng_state *crng, static void _extract_crng(struct crng_state *crng,
__u8 out[CHACHA20_BLOCK_SIZE]) __u32 out[CHACHA20_BLOCK_WORDS])
{ {
unsigned long v, flags; unsigned long v, flags;
@ -867,7 +867,7 @@ static void _extract_crng(struct crng_state *crng,
spin_unlock_irqrestore(&crng->lock, flags); spin_unlock_irqrestore(&crng->lock, flags);
} }
static void extract_crng(__u8 out[CHACHA20_BLOCK_SIZE]) static void extract_crng(__u32 out[CHACHA20_BLOCK_WORDS])
{ {
struct crng_state *crng = NULL; struct crng_state *crng = NULL;
@ -885,7 +885,7 @@ static void extract_crng(__u8 out[CHACHA20_BLOCK_SIZE])
* enough) to mutate the CRNG key to provide backtracking protection. * enough) to mutate the CRNG key to provide backtracking protection.
*/ */
static void _crng_backtrack_protect(struct crng_state *crng, static void _crng_backtrack_protect(struct crng_state *crng,
__u8 tmp[CHACHA20_BLOCK_SIZE], int used) __u32 tmp[CHACHA20_BLOCK_WORDS], int used)
{ {
unsigned long flags; unsigned long flags;
__u32 *s, *d; __u32 *s, *d;
@ -897,14 +897,14 @@ static void _crng_backtrack_protect(struct crng_state *crng,
used = 0; used = 0;
} }
spin_lock_irqsave(&crng->lock, flags); spin_lock_irqsave(&crng->lock, flags);
s = (__u32 *) &tmp[used]; s = &tmp[used / sizeof(__u32)];
d = &crng->state[4]; d = &crng->state[4];
for (i=0; i < 8; i++) for (i=0; i < 8; i++)
*d++ ^= *s++; *d++ ^= *s++;
spin_unlock_irqrestore(&crng->lock, flags); spin_unlock_irqrestore(&crng->lock, flags);
} }
static void crng_backtrack_protect(__u8 tmp[CHACHA20_BLOCK_SIZE], int used) static void crng_backtrack_protect(__u32 tmp[CHACHA20_BLOCK_WORDS], int used)
{ {
struct crng_state *crng = NULL; struct crng_state *crng = NULL;
@ -920,7 +920,7 @@ static void crng_backtrack_protect(__u8 tmp[CHACHA20_BLOCK_SIZE], int used)
static ssize_t extract_crng_user(void __user *buf, size_t nbytes) static ssize_t extract_crng_user(void __user *buf, size_t nbytes)
{ {
ssize_t ret = 0, i = CHACHA20_BLOCK_SIZE; ssize_t ret = 0, i = CHACHA20_BLOCK_SIZE;
__u8 tmp[CHACHA20_BLOCK_SIZE]; __u32 tmp[CHACHA20_BLOCK_WORDS];
int large_request = (nbytes > 256); int large_request = (nbytes > 256);
while (nbytes) { while (nbytes) {
@ -1507,7 +1507,7 @@ static void _warn_unseeded_randomness(const char *func_name, void *caller,
*/ */
static void _get_random_bytes(void *buf, int nbytes) static void _get_random_bytes(void *buf, int nbytes)
{ {
__u8 tmp[CHACHA20_BLOCK_SIZE]; __u32 tmp[CHACHA20_BLOCK_WORDS];
trace_get_random_bytes(nbytes, _RET_IP_); trace_get_random_bytes(nbytes, _RET_IP_);
@ -2114,7 +2114,7 @@ u64 get_random_u64(void)
if (use_lock) if (use_lock)
read_lock_irqsave(&batched_entropy_reset_lock, flags); read_lock_irqsave(&batched_entropy_reset_lock, flags);
if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) { if (batch->position % ARRAY_SIZE(batch->entropy_u64) == 0) {
extract_crng((u8 *)batch->entropy_u64); extract_crng((__u32 *)batch->entropy_u64);
batch->position = 0; batch->position = 0;
} }
ret = batch->entropy_u64[batch->position++]; ret = batch->entropy_u64[batch->position++];
@ -2144,7 +2144,7 @@ u32 get_random_u32(void)
if (use_lock) if (use_lock)
read_lock_irqsave(&batched_entropy_reset_lock, flags); read_lock_irqsave(&batched_entropy_reset_lock, flags);
if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) { if (batch->position % ARRAY_SIZE(batch->entropy_u32) == 0) {
extract_crng((u8 *)batch->entropy_u32); extract_crng(batch->entropy_u32);
batch->position = 0; batch->position = 0;
} }
ret = batch->entropy_u32[batch->position++]; ret = batch->entropy_u32[batch->position++];

3
include/crypto/chacha20.h
View File

@ -13,12 +13,13 @@
#define CHACHA20_IV_SIZE 16 #define CHACHA20_IV_SIZE 16
#define CHACHA20_KEY_SIZE 32 #define CHACHA20_KEY_SIZE 32
#define CHACHA20_BLOCK_SIZE 64 #define CHACHA20_BLOCK_SIZE 64
#define CHACHA20_BLOCK_WORDS (CHACHA20_BLOCK_SIZE / sizeof(u32))
struct chacha20_ctx { struct chacha20_ctx {
u32 key[8]; u32 key[8];
}; };
void chacha20_block(u32 *state, void *stream); void chacha20_block(u32 *state, u32 *stream);
void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv); void crypto_chacha20_init(u32 *state, struct chacha20_ctx *ctx, u8 *iv);
int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key, int crypto_chacha20_setkey(struct crypto_skcipher *tfm, const u8 *key,
unsigned int keysize); unsigned int keysize);

2
lib/chacha20.c
View File

@ -21,7 +21,7 @@ static inline u32 rotl32(u32 v, u8 n)
return (v << n) | (v >> (sizeof(v) * 8 - n)); return (v << n) | (v >> (sizeof(v) * 8 - n));
} }
extern void chacha20_block(u32 *state, void *stream) void chacha20_block(u32 *state, u32 *stream)
{ {
u32 x[16], *out = stream; u32 x[16], *out = stream;
int i; int i;