linux/net/sunrpc/Kconfig
Ard Biesheuvel e33d2a7b30 SUNRPC: remove RC4-HMAC-MD5 support from KerberosV
The RC4-HMAC-MD5 KerberosV algorithm is based on RFC 4757 [0], which
was specifically issued for interoperability with Windows 2000, but was
never intended to receive the same level of support. The RFC says

  The IETF Kerberos community supports publishing this specification as
  an informational document in order to describe this widely
  implemented technology.  However, while these encryption types
  provide the operations necessary to implement the base Kerberos
  specification [RFC4120], they do not provide all the required
  operations in the Kerberos cryptography framework [RFC3961].  As a
  result, it is not generally possible to implement potential
  extensions to Kerberos using these encryption types.  The Kerberos
  encryption type negotiation mechanism [RFC4537] provides one approach
  for using such extensions even when a Kerberos infrastructure uses
  long-term RC4 keys.  Because this specification does not implement
  operations required by RFC 3961 and because of security concerns with
  the use of RC4 and MD4 discussed in Section 8, this specification is
  not appropriate for publication on the standards track.

  The RC4-HMAC encryption types are used to ease upgrade of existing
  Windows NT environments, provide strong cryptography (128-bit key
  lengths), and provide exportable (meet United States government
  export restriction requirements) encryption.  This document describes
  the implementation of those encryption types.

Furthermore, this RFC was re-classified as 'historic' by RFC 8429 [1] in
2018, stating that 'none of the encryption types it specifies should be
used'

Note that other outdated algorithms are left in place (some of which are
guarded by CONFIG_SUNRPC_DISABLE_INSECURE_ENCTYPES), so this should only
adversely affect interoperability with Windows NT/2000 systems that have
not received any updates since 2008 (but are connected to a network
nonetheless)

[0] https://tools.ietf.org/html/rfc4757
[1] https://tools.ietf.org/html/rfc8429

Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: J. Bruce Fields <bfields@redhat.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
2020-09-11 14:39:15 +10:00

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# SPDX-License-Identifier: GPL-2.0-only
config SUNRPC
tristate
depends on MULTIUSER
config SUNRPC_GSS
tristate
select OID_REGISTRY
depends on MULTIUSER
config SUNRPC_BACKCHANNEL
bool
depends on SUNRPC
config SUNRPC_SWAP
bool
depends on SUNRPC
config RPCSEC_GSS_KRB5
tristate "Secure RPC: Kerberos V mechanism"
depends on SUNRPC && CRYPTO
depends on CRYPTO_MD5 && CRYPTO_DES && CRYPTO_CBC && CRYPTO_CTS
depends on CRYPTO_ECB && CRYPTO_HMAC && CRYPTO_SHA1 && CRYPTO_AES
default y
select SUNRPC_GSS
help
Choose Y here to enable Secure RPC using the Kerberos version 5
GSS-API mechanism (RFC 1964).
Secure RPC calls with Kerberos require an auxiliary user-space
daemon which may be found in the Linux nfs-utils package
available from http://linux-nfs.org/. In addition, user-space
Kerberos support should be installed.
If unsure, say Y.
config SUNRPC_DISABLE_INSECURE_ENCTYPES
bool "Secure RPC: Disable insecure Kerberos encryption types"
depends on RPCSEC_GSS_KRB5
default n
help
Choose Y here to disable the use of deprecated encryption types
with the Kerberos version 5 GSS-API mechanism (RFC 1964). The
deprecated encryption types include DES-CBC-MD5, DES-CBC-CRC,
and DES-CBC-MD4. These types were deprecated by RFC 6649 because
they were found to be insecure.
N is the default because many sites have deployed KDCs and
keytabs that contain only these deprecated encryption types.
Choosing Y prevents the use of known-insecure encryption types
but might result in compatibility problems.
config SUNRPC_DEBUG
bool "RPC: Enable dprintk debugging"
depends on SUNRPC && SYSCTL
select DEBUG_FS
help
This option enables a sysctl-based debugging interface
that is be used by the 'rpcdebug' utility to turn on or off
logging of different aspects of the kernel RPC activity.
Disabling this option will make your kernel slightly smaller,
but makes troubleshooting NFS issues significantly harder.
If unsure, say Y.
config SUNRPC_XPRT_RDMA
tristate "RPC-over-RDMA transport"
depends on SUNRPC && INFINIBAND && INFINIBAND_ADDR_TRANS
default SUNRPC && INFINIBAND
select SG_POOL
help
This option allows the NFS client and server to use RDMA
transports (InfiniBand, iWARP, or RoCE).
To compile this support as a module, choose M. The module
will be called rpcrdma.ko.
If unsure, or you know there is no RDMA capability on your
hardware platform, say N.