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Remove support for the "Crypto usage statistics" feature
(CONFIG_CRYPTO_STATS). This feature does not appear to have ever been
used, and it is harmful because it significantly reduces performance and
is a large maintenance burden.
Covering each of these points in detail:
1. Feature is not being used
Since these generic crypto statistics are only readable using netlink,
it's fairly straightforward to look for programs that use them. I'm
unable to find any evidence that any such programs exist. For example,
Debian Code Search returns no hits except the kernel header and kernel
code itself and translations of the kernel header:
https://codesearch.debian.net/search?q=CRYPTOCFGA_STAT&literal=1&perpkg=1
The patch series that added this feature in 2018
(https://lore.kernel.org/linux-crypto/1537351855-16618-1-git-send-email-clabbe@baylibre.com/)
said "The goal is to have an ifconfig for crypto device." This doesn't
appear to have happened.
It's not clear that there is real demand for crypto statistics. Just
because the kernel provides other types of statistics such as I/O and
networking statistics and some people find those useful does not mean
that crypto statistics are useful too.
Further evidence that programs are not using CONFIG_CRYPTO_STATS is that
it was able to be disabled in RHEL and Fedora as a bug fix
(https://gitlab.com/redhat/centos-stream/src/kernel/centos-stream-9/-/merge_requests/2947).
Even further evidence comes from the fact that there are and have been
bugs in how the stats work, but they were never reported. For example,
before Linux v6.7 hash stats were double-counted in most cases.
There has also never been any documentation for this feature, so it
might be hard to use even if someone wanted to.
2. CONFIG_CRYPTO_STATS significantly reduces performance
Enabling CONFIG_CRYPTO_STATS significantly reduces the performance of
the crypto API, even if no program ever retrieves the statistics. This
primarily affects systems with a large number of CPUs. For example,
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/2039576 reported
that Lustre client encryption performance improved from 21.7GB/s to
48.2GB/s by disabling CONFIG_CRYPTO_STATS.
It can be argued that this means that CONFIG_CRYPTO_STATS should be
optimized with per-cpu counters similar to many of the networking
counters. But no one has done this in 5+ years. This is consistent
with the fact that the feature appears to be unused, so there seems to
be little interest in improving it as opposed to just disabling it.
It can be argued that because CONFIG_CRYPTO_STATS is off by default,
performance doesn't matter. But Linux distros tend to error on the side
of enabling options. The option is enabled in Ubuntu and Arch Linux,
and until recently was enabled in RHEL and Fedora (see above). So, even
just having the option available is harmful to users.
3. CONFIG_CRYPTO_STATS is a large maintenance burden
There are over 1000 lines of code associated with CONFIG_CRYPTO_STATS,
spread among 32 files. It significantly complicates much of the
implementation of the crypto API. After the initial submission, many
fixes and refactorings have consumed effort of multiple people to keep
this feature "working". We should be spending this effort elsewhere.
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Acked-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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The lskcipher glue code for skcipher needs to copy the IV every
time rather than only on the first and last request. Otherwise
those algorithms that use IV to perform chaining may break, e.g.,
CBC.
This is because crypto_skcipher_import/export do not include the
IV as part of the saved state.
Reported-by: syzbot+b90b904ef6bdfdafec1d@syzkaller.appspotmail.com
Fixes: 662ea18d089b ("crypto: skcipher - Make use of internal state")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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When ecb is used to wrap an lskcipher, the statesize isn't set
correctly. Fix this by making the simple instance creator set
the statesize.
Reported-by: syzbot+8ffb0839a24e9c6bfa76@syzkaller.appspotmail.com
Reported-by: Edward Adam Davis <eadavis@qq.com>
Fixes: 662ea18d089b ("crypto: skcipher - Make use of internal state")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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This patch adds code to the skcipher/lskcipher API to make use
of the internal state if present. In particular, the skcipher
lskcipher wrapper will allocate a buffer for the IV/state and
feed that to the underlying lskcipher algorithm.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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Unlike chaining modes such as CBC, stream ciphers other than CTR
usually hold an internal state that must be preserved if the
operation is to be done piecemeal. This has not been represented
in the API, resulting in the inability to split up stream cipher
operations.
This patch adds the basic representation of an internal state to
skcipher and lskcipher. In the interest of backwards compatibility,
the default has been set such that existing users are assumed to
be operating in one go as opposed to piecemeal.
With the new API, each lskcipher/skcipher algorithm has a new
attribute called statesize. For skcipher, this is the size of
the buffer that can be exported or imported similar to ahash.
For lskcipher, instead of providing a buffer of ivsize, the user
now has to provide a buffer of ivsize + statesize.
Each skcipher operation is assumed to be final as they are now,
but this may be overridden with a request flag. When the override
occurs, the user may then export the partial state and reimport
it later.
For lskcipher operations this is reversed. All operations are
not final and the state will be exported unless the FINAL bit is
set. However, the CONT bit still has to be set for the state
to be used.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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When an algorithm of the new "lskcipher" type is exposed through the
"skcipher" API, calls to crypto_skcipher_setkey() don't pass on the
CRYPTO_TFM_REQ_FORBID_WEAK_KEYS flag to the lskcipher. This causes
self-test failures for ecb(des), as weak keys are not rejected anymore.
Fix this.
Fixes: 31865c4c4db2 ("crypto: skcipher - Add lskcipher")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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Set the error value to -EINVAL instead of zero when the underlying
name (within "ecb()") fails basic sanity checks.
Fixes: 8aee5d4ebd11 ("crypto: lskcipher - Add compatibility wrapper around ECB")
Reported-by: kernel test robot <lkp@intel.com>
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Closes: https://lore.kernel.org/r/202310111323.ZjK7bzjw-lkp@intel.com/
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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As an aid to the transition from cipher algorithm implementations
to lskcipher, add a temporary wrapper when creating simple lskcipher
templates by using ecb(X) instead of X if an lskcipher implementation
of X cannot be found.
This can be reverted once all cipher implementations have switched
over to lskcipher.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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Add a new API type lskcipher designed for taking straight kernel
pointers instead of SG lists. Its relationship to skcipher will
be analogous to that between shash and ahash.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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