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When comparing MAC hashes, AEAD authentication tags, or other hash
values in the context of authentication or integrity checking, it
is important not to leak timing information to a potential attacker,
i.e. when communication happens over a network.
Bytewise memory comparisons (such as memcmp) are usually optimized so
that they return a nonzero value as soon as a mismatch is found. E.g,
on x86_64/i5 for 512 bytes this can be ~50 cyc for a full mismatch
and up to ~850 cyc for a full match (cold). This early-return behavior
can leak timing information as a side channel, allowing an attacker to
iteratively guess the correct result.
This patch adds a new method crypto_memneq ("memory not equal to each
other") to the crypto API that compares memory areas of the same length
in roughly "constant time" (cache misses could change the timing, but
since they don't reveal information about the content of the strings
being compared, they are effectively benign). Iow, best and worst case
behaviour take the same amount of time to complete (in contrast to
memcmp).
Note that crypto_memneq (unlike memcmp) can only be used to test for
equality or inequality, NOT for lexicographical order. This, however,
is not an issue for its use-cases within the crypto API.
We tried to locate all of the places in the crypto API where memcmp was
being used for authentication or integrity checking, and convert them
over to crypto_memneq.
crypto_memneq is declared noinline, placed in its own source file,
and compiled with optimizations that might increase code size disabled
("Os") because a smart compiler (or LTO) might notice that the return
value is always compared against zero/nonzero, and might then
reintroduce the same early-return optimization that we are trying to
avoid.
Using #pragma or __attribute__ optimization annotations of the code
for disabling optimization was avoided as it seems to be considered
broken or unmaintained for long time in GCC [1]. Therefore, we work
around that by specifying the compile flag for memneq.o directly in
the Makefile. We found that this seems to be most appropriate.
As we use ("Os"), this patch also provides a loop-free "fast-path" for
frequently used 16 byte digests. Similarly to kernel library string
functions, leave an option for future even further optimized architecture
specific assembler implementations.
This was a joint work of James Yonan and Daniel Borkmann. Also thanks
for feedback from Florian Weimer on this and earlier proposals [2].
[1] http://gcc.gnu.org/ml/gcc/2012-07/msg00211.html
[2] https://lkml.org/lkml/2013/2/10/131
Signed-off-by: James Yonan <james@openvpn.net>
Signed-off-by: Daniel Borkmann <dborkman@redhat.com>
Cc: Florian Weimer <fw@deneb.enyo.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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Pull crypto update from Herbert Xu:
- XTS mode optimisation for twofish/cast6/camellia/aes on x86
- AVX2/x86_64 implementation for blowfish/twofish/serpent/camellia
- SSSE3/AVX/AVX2 optimisations for sha256/sha512
- Added driver for SAHARA2 crypto accelerator
- Fix for GMAC when used in non-IPsec secnarios
- Added generic CMAC implementation (including IPsec glue)
- IP update for crypto/atmel
- Support for more than one device in hwrng/timeriomem
- Added Broadcom BCM2835 RNG driver
- Misc fixes
* git://git.kernel.org/pub/scm/linux/kernel/git/herbert/crypto-2.6: (59 commits)
crypto: caam - fix job ring cleanup code
crypto: camellia - add AVX2/AES-NI/x86_64 assembler implementation of camellia cipher
crypto: serpent - add AVX2/x86_64 assembler implementation of serpent cipher
crypto: twofish - add AVX2/x86_64 assembler implementation of twofish cipher
crypto: blowfish - add AVX2/x86_64 implementation of blowfish cipher
crypto: tcrypt - add async cipher speed tests for blowfish
crypto: testmgr - extend camellia test-vectors for camellia-aesni/avx2
crypto: aesni_intel - fix Kconfig problem with CRYPTO_GLUE_HELPER_X86
crypto: aesni_intel - add more optimized XTS mode for x86-64
crypto: x86/camellia-aesni-avx - add more optimized XTS code
crypto: cast6-avx: use new optimized XTS code
crypto: x86/twofish-avx - use optimized XTS code
crypto: x86 - add more optimized XTS-mode for serpent-avx
xfrm: add rfc4494 AES-CMAC-96 support
crypto: add CMAC support to CryptoAPI
crypto: testmgr - add empty test vectors for null ciphers
crypto: testmgr - add AES GMAC test vectors
crypto: gcm - fix rfc4543 to handle async crypto correctly
crypto: gcm - make GMAC work when dst and src are different
hwrng: timeriomem - added devicetree hooks
...
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If the gcm cipher used by rfc4543 does not complete request immediately,
the authentication tag is not copied to destination buffer. Patch adds
correct async logic for this case.
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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The GMAC code assumes that dst==src, which causes problems when trying to add
rfc4543(gcm(aes)) test vectors.
So fix this code to work when source and destination buffer are different.
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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rfc4543(gcm(*)) code for GMAC assumes that assoc scatterlist always contains
only one segment and only makes use of this first segment. However ipsec passes
assoc with three segments when using 'extended sequence number' thus in this
case rfc4543(gcm(*)) fails to function correctly. Patch fixes this issue.
Reported-by: Chaoxing Lin <Chaoxing.Lin@ultra-3eti.com>
Tested-by: Chaoxing Lin <Chaoxing.Lin@ultra-3eti.com>
Cc: stable@vger.kernel.org
Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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Replace PTR_ERR followed by ERR_PTR by ERR_CAST, to be more concise.
The semantic patch that makes this change is as follows:
(http://coccinelle.lip6.fr/)
// <smpl>
@@
expression err,x;
@@
- err = PTR_ERR(x);
if (IS_ERR(x))
- return ERR_PTR(err);
+ return ERR_CAST(x);
// </smpl>
Signed-off-by: Julia Lawall <Julia.Lawall@lip6.fr>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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Use scatterwalk_crypto_chain in favor of locally defined chaining functions.
Signed-off-by: Steffen Klassert <steffen.klassert@secunet.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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This patch adds the RFC4543 (GMAC) wrapper for GCM similar to the
existing RFC4106 wrapper. The main differences between GCM and GMAC are
the contents of the AAD and that the plaintext is empty for the latter.
Signed-off-by: Tobias Brunner <tobias@strongswan.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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The flow of the complete function (xxx_done) in gcm.c is as follow:
void complete(struct crypto_async_request *areq, int err)
{
struct aead_request *req = areq->data;
if (!err) {
err = async_next_step();
if (err == -EINPROGRESS || err == -EBUSY)
return;
}
complete_for_next_step(areq, err);
}
But *areq may be destroyed in async_next_step(), this makes
complete_for_next_step() can not work properly. To fix this, one of
following methods is used for each complete function.
- Add a __complete() for each complete(), which accept struct
aead_request *req instead of areq, so avoid using areq after it is
destroyed.
- Expand complete_for_next_step().
The fixing method is based on the idea of Herbert Xu.
Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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Remove the dedicated GHASH implementation in GCM, and uses the GHASH
digest algorithm instead. This will make GCM uses hardware accelerated
GHASH implementation automatically if available.
ahash instead of shash interface is used, because some hardware
accelerated GHASH implementation needs asynchronous interface.
Signed-off-by: Huang Ying <ying.huang@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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This patch introduces the rfc4106 wrapper for GCM just as we have an
rfc4309 wrapper for CCM. The purpose of the wrapper is to include part
of the IV in the key so that it can be negotiated by IPsec.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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This patch converts the gcm algorithm over to crypto_grab_skcipher
which is a prerequisite for IV generation.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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This patch adds the gcm_base template which takes a block cipher
parameter instead of cipher. This allows the user to specify a
specific CTR implementation.
This also fixes a leak of the cipher algorithm that was previously
looked up but never freed.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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This patch adds the necessary changes for GCM to be used with async
ciphers. This would allow it to be used with hardware devices that
support CTR.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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As discussed previously, this patch moves the basic CTR functionality
into a chainable algorithm called ctr. The IPsec-specific variant of
it is now placed on top with the name rfc3686.
So ctr(aes) gives a chainable cipher with IV size 16 while the IPsec
variant will be called rfc3686(ctr(aes)). This patch also adjusts
gcm accordingly.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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This patch fixes the request context alignment so that it is actually
aligned to the value required by the algorithm.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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The abreq structure is currently allocated on the stack. This is broken
if the underlying algorithm is asynchronous. This patch changes it so
that it's taken from the private context instead which has been enlarged
accordingly.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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Unfortunately the generic chaining hasn't been ported to all architectures
yet, and notably not s390. So this patch restores the chainging that we've
been using previously which does work everywhere.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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The scatterwalk infrastructure is used by algorithms so it needs to
move out of crypto for future users that may live in drivers/crypto
or asm/*/crypto.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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This patch changes gcm/authenc to return EBADMSG instead of EINVAL for
ICV mismatches. This convention has already been adopted by IPsec.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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The crypto_aead convention for ICVs is to include it directly in the
output. If we decided to change this in future then we would make
the ICV (if the algorithm has an explicit one) available in the
request itself.
For now no algorithm needs this so this patch changes gcm to conform
to this convention. It also adjusts the tcrypt aead tests to take
this into account.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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As it is authsize is an algorithm paramter which cannot be changed at
run-time. This is inconvenient because hardware that implements such
algorithms would have to register each authsize that they support
separately.
Since authsize is a property common to all AEAD algorithms, we can add
a function setauthsize that sets it at run-time, just like setkey.
This patch does exactly that and also changes authenc so that authsize
is no longer a parameter of its template.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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Add GCM/GMAC support to cryptoapi.
GCM (Galois/Counter Mode) is an AEAD mode of operations for any block cipher
with a block size of 16. The typical example is AES-GCM.
Signed-off-by: Mikko Herranen <mh1@iki.fi>
Reviewed-by: Mika Kukkonen <mika.kukkonen@nsn.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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