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  1. 25 Jan, 2018 9 commits
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  11. 12 Jan, 2018 9 commits
    • tcharding's avatar
      crypto: doc - clear htmldocs build warnings for crypto/hash · b40fa82c
      tcharding authored 
      SPHINX build emits multiple warnings of kind:

	warning: duplicate section name 'Note'

(when building kernel via make target 'htmldocs')

This is caused by repeated use of comments of form:

	* Note: soau soaeusoa uoe

We can change the format without loss of clarity and clear the build
warnings.

Add '**[mandatory]**' or '**[optional]**' as kernel-doc field element
description prefix

This renders in HTML as (prefixes in bold)

final
    [mandatory] Retrieve result from the driver. This function finalizes the
    transformation and retrieves the resulting hash from the driver and
    pushes it back to upper layers. No data processing happens at this
    point unless hardware requires it to finish the transformation (then
    the data buffered by the device driver is processed).
Signed-off-by: default avatarTobin C. Harding <me@tobin.cc>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
      b40fa82c
    • Eric Biggers's avatar
      crypto: x86/salsa20 - cleanup and convert to skcipher API · c9a3ff8f
      Eric Biggers authored 
      Convert salsa20-asm from the deprecated "blkcipher" API to the
"skcipher" API, in the process fixing it up to use the generic helpers.
This allows removing the salsa20_keysetup() and salsa20_ivsetup()
assembly functions, which aren't performance critical; the C versions do
just fine.

This also fixes the same bug that salsa20-generic had, where the state
array was being maintained directly in the transform context rather than
on the stack or in the request context.  Thus, if multiple threads used
the same Salsa20 transform concurrently they produced the wrong results.
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
      c9a3ff8f
    • Eric Biggers's avatar
      crypto: salsa20 - export generic helpers · eb772f37
      Eric Biggers authored 
      Export the Salsa20 constants, transform context, and initialization
functions so that they can be reused by the x86 implementation.
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
      eb772f37
    • Eric Biggers's avatar
      crypto: salsa20-generic - cleanup and convert to skcipher API · b62b3db7
      Eric Biggers authored 
      Convert salsa20-generic from the deprecated "blkcipher" API to the
"skcipher" API, in the process fixing it up to be thread-safe (as the
crypto API expects) by maintaining each request's state separately from
the transform context.

Also remove the unnecessary cra_alignmask and tighten validation of the
key size by accepting only 16 or 32 bytes, not anything in between.

These changes bring the code close to the way chacha20-generic does
things, so hopefully it will be easier to maintain in the future.

However, the way Salsa20 interprets the IV is still slightly different;
that was not changed.
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
      b62b3db7
    • Arnd Bergmann's avatar
      crypto: aes-generic - build with -Os on gcc-7+ · 148b974d
      Arnd Bergmann authored 
      While testing other changes, I discovered that gcc-7.2.1 produces badly
optimized code for aes_encrypt/aes_decrypt. This is especially true when
CONFIG_UBSAN_SANITIZE_ALL is enabled, where it leads to extremely
large stack usage that in turn might cause kernel stack overflows:

crypto/aes_generic.c: In function 'aes_encrypt':
crypto/aes_generic.c:1371:1: warning: the frame size of 4880 bytes is larger than 2048 bytes [-Wframe-larger-than=]
crypto/aes_generic.c: In function 'aes_decrypt':
crypto/aes_generic.c:1441:1: warning: the frame size of 4864 bytes is larger than 2048 bytes [-Wframe-larger-than=]

I verified that this problem exists on all architectures that are
supported by gcc-7.2, though arm64 in particular is less affected than
the others. I also found that gcc-7.1 and gcc-8 do not show the extreme
stack usage but still produce worse code than earlier versions for this
file, apparently because of optimization passes that generally provide
a substantial improvement in object code quality but understandably fail
to find any shortcuts in the AES algorithm.

Possible workarounds include

a) disabling -ftree-pre and -ftree-sra optimizations, this was an earlier
   patch I tried, which reliably fixed the stack usage, but caused a
   serious performance regression in some versions, as later testing
   found.

b) disabling UBSAN on this file or all ciphers, as suggested by Ard
   Biesheuvel. This would lead to massively better crypto performance in
   UBSAN-enabled kernels and avoid the stack usage, but there is a concern
   over whether we should exclude arbitrary files from UBSAN at all.

c) Forcing the optimization level in a different way. Similar to a),
   but rather than deselecting specific optimization stages,
   this now uses "gcc -Os" for this file, regardless of the
   CONFIG_CC_OPTIMIZE_FOR_PERFORMANCE/SIZE option. This is a reliable
   workaround for the stack consumption on all architecture, and I've
   retested the performance results now on x86, cycles/byte (lower is
   better) for cbc(aes-generic) with 256 bit keys:

			-O2     -Os
	gcc-6.3.1	14.9	15.1
	gcc-7.0.1	14.7	15.3
	gcc-7.1.1	15.3	14.7
	gcc-7.2.1	16.8	15.9
	gcc-8.0.0	15.5	15.6

This implements the option c) by enabling forcing -Os on all compiler
versions starting with gcc-7.1. As a workaround for PR83356, it would
only be needed for gcc-7.2+ with UBSAN enabled, but since it also shows
better performance on gcc-7.1 without UBSAN, it seems appropriate to
use the faster version here as well.

Side note: during testing, I also played with the AES code in libressl,
which had a similar performance regression from gcc-6 to gcc-7.2,
but was three times slower overall. It might be interesting to
investigate that further and possibly port the Linux implementation
into that.

Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83356
Link: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=83651
Cc: Richard Biener <rguenther@suse.de>
Cc: Jakub Jelinek <jakub@gcc.gnu.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarArnd Bergmann <arnd@arndb.de>
Acked-by: default avatarArd Biesheuvel <ard.biesheuvel@linaro.org>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
      148b974d
    • Eric Biggers's avatar
      crypto: aead - prevent using AEADs without setting key · dc26c17f
      Eric Biggers authored 
      Similar to what was done for the hash API, update the AEAD API to track
whether each transform has been keyed, and reject encryption/decryption
if a key is needed but one hasn't been set.

This isn't quite as important as the equivalent fix for the hash API
because AEADs always require a key, so are unlikely to be used without
one.  Still, tracking the key will prevent accidental unkeyed use.
algif_aead also had to track the key anyway, so the new flag replaces
that and slightly simplifies the algif_aead implementation.
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
      dc26c17f
    • Eric Biggers's avatar
      crypto: skcipher - prevent using skciphers without setting key · f8d33fac
      Eric Biggers authored 
      Similar to what was done for the hash API, update the skcipher API to
track whether each transform has been keyed, and reject
encryption/decryption if a key is needed but one hasn't been set.

This isn't as important as the equivalent fix for the hash API because
symmetric ciphers almost always require a key (the "null cipher" is the
only exception), so are unlikely to be used without one.  Still,
tracking the key will prevent accidental unkeyed use.  algif_skcipher
also had to track the key anyway, so the new flag replaces that and
simplifies the algif_skcipher implementation.
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
      f8d33fac
    • Eric Biggers's avatar
      crypto: ghash - remove checks for key being set · 4e1d14bc
      Eric Biggers authored 
      Now that the crypto API prevents a keyed hash from being used without
setting the key, there's no need for GHASH to do this check itself.
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
      4e1d14bc
    • Eric Biggers's avatar
      crypto: hash - prevent using keyed hashes without setting key · 9fa68f62
      Eric Biggers authored 
      Currently, almost none of the keyed hash algorithms check whether a key
has been set before proceeding.  Some algorithms are okay with this and
will effectively just use a key of all 0's or some other bogus default.
However, others will severely break, as demonstrated using
"hmac(sha3-512-generic)", the unkeyed use of which causes a kernel crash
via a (potentially exploitable) stack buffer overflow.

A while ago, this problem was solved for AF_ALG by pairing each hash
transform with a 'has_key' bool.  However, there are still other places
in the kernel where userspace can specify an arbitrary hash algorithm by
name, and the kernel uses it as unkeyed hash without checking whether it
is really unkeyed.  Examples of this include:

    - KEYCTL_DH_COMPUTE, via the KDF extension
    - dm-verity
    - dm-crypt, via the ESSIV support
    - dm-integrity, via the "internal hash" mode with no key given
    - drbd (Distributed Replicated Block Device)

This bug is especially bad for KEYCTL_DH_COMPUTE as that requires no
privileges to call.

Fix the bug for all users by adding a flag CRYPTO_TFM_NEED_KEY to the
->crt_flags of each hash transform that indicates whether the transform
still needs to be keyed or not.  Then, make the hash init, import, and
digest functions return -ENOKEY if the key is still needed.

The new flag also replaces the 'has_key' bool which algif_hash was
previously using, thereby simplifying the algif_hash implementation.
Reported-by: default avatarsyzbot <syzkaller@googlegroups.com>
Cc: stable@vger.kernel.org
Signed-off-by: default avatarEric Biggers <ebiggers@google.com>
Signed-off-by: default avatarHerbert Xu <herbert@gondor.apana.org.au>
      9fa68f62
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