Add FIPS 202 SHA-3 hash signature support in x509 certificates, pkcs7
signatures, and authenticode signatures. Supports hashes of size 256
and up, as 224 is too weak for any practical purposes.
Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Add support in rsa-pkcs1pad for FIPS 202 SHA-3 hashes, sizes 256 and
up. As 224 is too weak for any practical purposes.
Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Register FIPS 202 SHA-3 hashes in hash info for IMA and other
users. Sizes 256 and up, as 224 is too weak for any practical
purposes.
Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The "ahash" API provides access to both CPU-based and hardware offload-
based implementations of hash algorithms. Typically the former are
implemented as "shash" algorithms under the hood, while the latter are
implemented as "ahash" algorithms. The "ahash" API provides access to
both. Various kernel subsystems use the ahash API because they want to
support hashing hardware offload without using a separate API for it.
Yet, the common case is that a crypto accelerator is not actually being
used, and ahash is just wrapping a CPU-based shash algorithm.
This patch optimizes the ahash API for that common case by eliminating
the extra indirect call for each ahash operation on top of shash.
It also fixes the double-counting of crypto stats in this scenario
(though CONFIG_CRYPTO_STATS should *not* be enabled by anyone interested
in performance anyway...), and it eliminates redundant checking of
CRYPTO_TFM_NEED_KEY. As a bonus, it also shrinks struct crypto_ahash.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Since the previous patch made crypto_shash_type visible to ahash.c,
change checks for '->cra_type != &crypto_ahash_type' to '->cra_type ==
&crypto_shash_type'. This makes more sense and avoids having to
forward-declare crypto_ahash_type. The result is still the same, since
the type is either shash or ahash here.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The functions that are involved in implementing the ahash API on top of
an shash algorithm belong better in ahash.c, not in shash.c where they
currently are. Move them.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
struct ahash_request_priv is unused, so remove it.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Now that the alignmask for ahash and shash algorithms is always 0,
simplify crypto_gcm_create_common() accordingly.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Now that the alignmask for ahash and shash algorithms is always 0,
simplify chachapoly_create() accordingly.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Now that the alignmask for ahash and shash algorithms is always 0,
simplify crypto_ccm_create_common() accordingly.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Now that the alignmask for ahash and shash algorithms is always 0,
crypto_ahash_alignmask() always returns 0 and will be removed. In
preparation for this, stop checking crypto_ahash_alignmask() in testmgr.
As a result of this change,
test_sg_division::offset_relative_to_alignmask and
testvec_config::key_offset_relative_to_alignmask no longer have any
effect on ahash (or shash) algorithms. Therefore, also stop setting
these flags in default_hash_testvec_configs[].
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Now that the alignmask for ahash and shash algorithms is always 0,
simplify the code in authenc accordingly.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Now that the alignmask for ahash and shash algorithms is always 0,
simplify the code in authenc accordingly.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Currently, the ahash API checks the alignment of all key and result
buffers against the algorithm's declared alignmask, and for any
unaligned buffers it falls back to manually aligned temporary buffers.
This is virtually useless, however. First, since it does not apply to
the message, its effect is much more limited than e.g. is the case for
the alignmask for "skcipher". Second, the key and result buffers are
given as virtual addresses and cannot (in general) be DMA'ed into, so
drivers end up having to copy to/from them in software anyway. As a
result it's easy to use memcpy() or the unaligned access helpers.
The crypto_hash_walk_*() helper functions do use the alignmask to align
the message. But with one exception those are only used for shash
algorithms being exposed via the ahash API, not for native ahashes, and
aligning the message is not required in this case, especially now that
alignmask support has been removed from shash. The exception is the
n2_core driver, which doesn't set an alignmask.
In any case, no ahash algorithms actually set a nonzero alignmask
anymore. Therefore, remove support for it from ahash. The benefit is
that all the code to handle "misaligned" buffers in the ahash API goes
away, reducing the overhead of the ahash API.
This follows the same change that was made to shash.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Per section 4.c. of the IETF Trust Legal Provisions, "Code Components"
in IETF Documents are licensed on the terms of the BSD-3-Clause license:
https://trustee.ietf.org/documents/trust-legal-provisions/tlp-5/
The term "Code Components" specifically includes ASN.1 modules:
https://trustee.ietf.org/documents/trust-legal-provisions/code-components-list-3/
Add an SPDX identifier as well as a copyright notice pursuant to section
6.d. of the Trust Legal Provisions to all ASN.1 modules in the tree
which are derived from IETF Documents.
Section 4.d. of the Trust Legal Provisions requests that each Code
Component identify the RFC from which it is taken, so link that RFC
in every ASN.1 module.
Signed-off-by: Lukas Wunner <lukas@wunner.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The health test result in the current code is only given for the currently
processed raw time stamp. This implies to react on the health test error,
the result must be checked after each raw time stamp being processed. To
avoid this constant checking requirement, any health test error is recorded
and stored to be analyzed at a later time, if needed.
This change ensures that the power-up test catches any health test error.
Without that patch, the power-up health test result is not enforced.
The introduced changes are already in use with the user space version of
the Jitter RNG.
Fixes: 04597c8dd6 ("jitter - add RCT/APT support for different OSRs")
Reported-by: Joachim Vandersmissen <git@jvdsn.com>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Now that the shash algorithm type does not support nonzero alignmasks,
shash_alg::base.cra_alignmask is always 0, so OR-ing it into another
value is a no-op.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Now that the shash algorithm type does not support nonzero alignmasks,
shash_alg::base.cra_alignmask is always 0, so OR-ing it into another
value is a no-op.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Now that the shash algorithm type does not support nonzero alignmasks,
crypto_shash_alignmask() always returns 0 and will be removed. In
preparation for this, stop checking crypto_shash_alignmask() in testmgr.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Now that the shash algorithm type does not support nonzero alignmasks,
crypto_shash_alignmask() always returns 0 and will be removed. In
preparation for this, stop checking crypto_shash_alignmask() in drbg.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Currently, the shash API checks the alignment of all message, key, and
digest buffers against the algorithm's declared alignmask, and for any
unaligned buffers it falls back to manually aligned temporary buffers.
This is virtually useless, however. In the case of the message buffer,
cryptographic hash functions internally operate on fixed-size blocks, so
implementations end up needing to deal with byte-aligned data anyway
because the length(s) passed to ->update might not be divisible by the
block size. Word-alignment of the message can theoretically be helpful
for CRCs, like what was being done in crc32c-sparc64. But in practice
it's better for the algorithms to use unaligned accesses or align the
message themselves. A similar argument applies to the key and digest.
In any case, no shash algorithms actually set a nonzero alignmask
anymore. Therefore, remove support for it from shash. The benefit is
that all the code to handle "misaligned" buffers in the shash API goes
away, reducing the overhead of the shash API.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The xcbc template is setting its alignmask to that of its underlying
'cipher'. Yet, it doesn't care itself about how its inputs and outputs
are aligned, which is ostensibly the point of the alignmask. Instead,
xcbc actually just uses its alignmask itself to runtime-align certain
fields in its tfm and desc contexts appropriately for its underlying
cipher. That is almost entirely pointless too, though, since xcbc is
already using the cipher API functions that handle alignment themselves,
and few ciphers set a nonzero alignmask anyway. Also, even without
runtime alignment, an alignment of at least 4 bytes can be guaranteed.
Thus, at best this code is optimizing for the rare case of ciphers that
set an alignmask >= 7, at the cost of hurting the common cases.
Therefore, this patch removes the manual alignment code from xcbc and
makes it stop setting an alignmask.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The vmac template is setting its alignmask to that of its underlying
'cipher'. This doesn't actually accomplish anything useful, though, so
stop doing it. (vmac_update() does have an alignment bug, where it
assumes u64 alignment when it shouldn't, but that bug exists both before
and after this patch.) This is a prerequisite for removing support for
nonzero alignmasks from shash.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The hmac template is setting its alignmask to that of its underlying
unkeyed hash algorithm, and it is aligning the ipad and opad fields in
its tfm context to that alignment. However, hmac does not actually need
any sort of alignment itself, which makes this pointless except to keep
the pads aligned to what the underlying algorithm prefers. But very few
shash algorithms actually set an alignmask, and it is being removed from
those remaining ones; also, after setkey, the pads are only passed to
crypto_shash_import and crypto_shash_export which ignore the alignmask.
Therefore, make the hmac template stop setting an alignmask and simply
use natural alignment for ipad and opad. Note, this change also moves
the pads from the beginning of the tfm context to the end, which makes
much more sense; the variable-length fields should be at the end.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The cmac template is setting its alignmask to that of its underlying
'cipher'. Yet, it doesn't care itself about how its inputs and outputs
are aligned, which is ostensibly the point of the alignmask. Instead,
cmac actually just uses its alignmask itself to runtime-align certain
fields in its tfm and desc contexts appropriately for its underlying
cipher. That is almost entirely pointless too, though, since cmac is
already using the cipher API functions that handle alignment themselves,
and few ciphers set a nonzero alignmask anyway. Also, even without
runtime alignment, an alignment of at least 4 bytes can be guaranteed.
Thus, at best this code is optimizing for the rare case of ciphers that
set an alignmask >= 7, at the cost of hurting the common cases.
Therefore, this patch removes the manual alignment code from cmac and
makes it stop setting an alignmask.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The cbcmac template is aligning a field in its desc context to the
alignmask of its underlying 'cipher', at runtime. This is almost
entirely pointless, since cbcmac is already using the cipher API
functions that handle alignment themselves, and few ciphers set a
nonzero alignmask anyway. Also, even without runtime alignment, an
alignment of at least 4 bytes can be guaranteed.
Thus, at best this code is optimizing for the rare case of ciphers that
set an alignmask >= 7, at the cost of hurting the common cases.
Therefore, remove the manual alignment code from cbcmac.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Most shash algorithms don't have custom ->import and ->export functions,
resulting in the memcpy() based default being used. Yet,
crypto_shash_import() and crypto_shash_export() still make an indirect
call, which is expensive. Therefore, change how the default import and
export are called to make it so that crypto_shash_import() and
crypto_shash_export() don't do an indirect call in this case.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The modular build fails because the self-test code depends on pkcs7
which in turn depends on x509 which contains the self-test.
Split the self-test out into its own module to break the cycle.
Fixes: 3cde3174eb ("certs: Add FIPS selftests")
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: Jarkko Sakkinen <jarkko@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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: 31865c4c4d ("crypto: skcipher - Add lskcipher")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Set the error value to -EINVAL instead of zero when the underlying
name (within "ecb()") fails basic sanity checks.
Fixes: 8aee5d4ebd ("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>
It is possible to stand up own certificates and sign PE-COFF binaries
using SHA-224. However it never became popular or needed since it has
similar costs as SHA-256. Windows Authenticode infrastructure never
had support for SHA-224, and all secureboot keys used fro linux
vmlinuz have always been using at least SHA-256.
Given the point of mscode_parser is to support interoperatiblity with
typical de-facto hashes, remove support for SHA-224 to avoid
posibility of creating interoperatibility issues with rhboot/shim,
grub, and non-linux systems trying to sign or verify vmlinux.
SHA-224 itself is not removed from the kernel, as it is truncated
SHA-256. If requested I can write patches to remove SHA-224 support
across all of the drivers.
Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Removes support for sha1 signed kernel modules, importing sha1 signed
x.509 certificates.
rsa-pkcs1pad keeps sha1 padding support, which seems to be used by
virtio driver.
sha1 remains available as there are many drivers and subsystems using
it. Note only hmac(sha1) with secret keys remains cryptographically
secure.
In the kernel there are filesystems, IMA, tpm/pcr that appear to be
using sha1. Maybe they can all start to be slowly upgraded to
something else i.e. blake3, ParallelHash, SHAKE256 as needed.
Signed-off-by: Dimitri John Ledkov <dimitri.ledkov@canonical.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
When the source scatterlist is a single page, optimize the first hash
step of adiantum to use crypto_shash_digest() instead of
init/update/final, and use the same local kmap for both hashing the bulk
part and loading the narrow part of the source data.
Likewise, when the destination scatterlist is a single page, optimize
the second hash step of adiantum to use crypto_shash_digest() instead of
init/update/final, and use the same local kmap for both hashing the bulk
part and storing the narrow part of the destination data.
In some cases these optimizations improve performance significantly.
Note: ideally, for optimal performance each architecture should
implement the full "adiantum(xchacha12,aes)" algorithm and fully
optimize the contiguous buffer case to use no indirect calls. That's
not something I've gotten around to doing, though. This commit just
makes a relatively small change that provides some benefit with the
existing template-based approach.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Fold shash_digest_unaligned() into its only remaining caller. Also,
avoid a redundant check of CRYPTO_TFM_NEED_KEY by replacing the call to
crypto_shash_init() with shash->init(desc). Finally, replace
shash_update_unaligned() + shash_final_unaligned() with
shash_finup_unaligned() which does exactly that.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
For an shash algorithm that doesn't implement ->digest, currently
crypto_shash_digest() with aligned input makes 5 indirect calls: 1 to
shash_digest_unaligned(), 1 to ->init, 2 to ->update ('alignmask + 1'
bytes, then the rest), then 1 to ->final. This is true even if the
algorithm implements ->finup. This is caused by an unnecessary fallback
to code meant to handle unaligned inputs. In fact,
crypto_shash_digest() already does the needed alignment check earlier.
Therefore, optimize the number of indirect calls for aligned inputs to 3
when the algorithm implements ->finup. It remains at 5 when the
algorithm implements neither ->finup nor ->digest.
Similarly, for an shash algorithm that doesn't implement ->finup,
currently crypto_shash_finup() with aligned input makes 4 indirect
calls: 1 to shash_finup_unaligned(), 2 to ->update, and
1 to ->final. Optimize this to 3 calls.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Since commit adad556efc ("crypto: api - Fix built-in testing
dependency failures"), the following warning appears when booting an
x86_64 kernel that is configured with
CONFIG_CRYPTO_MANAGER_EXTRA_TESTS=y and CONFIG_CRYPTO_AES_NI_INTEL=y,
even when CONFIG_CRYPTO_XTS=y and CONFIG_CRYPTO_AES=y:
alg: skcipher: skipping comparison tests for xts-aes-aesni because xts(ecb(aes-generic)) is unavailable
This is caused by an issue in the xts template where it allocates an
"aes" single-block cipher without declaring a dependency on it via the
crypto_spawn mechanism. This issue was exposed by the above commit
because it reversed the order that the algorithms are tested in.
Specifically, when "xts(ecb(aes-generic))" is instantiated and tested
during the comparison tests for "xts-aes-aesni", the "xts" template
allocates an "aes" crypto_cipher for encrypting tweaks. This resolves
to "aes-aesni". (Getting "aes-aesni" instead of "aes-generic" here is a
bit weird, but it's apparently intended.) Due to the above-mentioned
commit, the testing of "aes-aesni", and the finalization of its
registration, now happens at this point instead of before. At the end
of that, crypto_remove_spawns() unregisters all algorithm instances that
depend on a lower-priority "aes" implementation such as "aes-generic"
but that do not depend on "aes-aesni". However, because "xts" does not
use the crypto_spawn mechanism for its "aes", its dependency on
"aes-aesni" is not recognized by crypto_remove_spawns(). Thus,
crypto_remove_spawns() unexpectedly unregisters "xts(ecb(aes-generic))".
Fix this issue by making the "xts" template use the crypto_spawn
mechanism for its "aes" dependency, like what other templates do.
Note, this fix could be applied as far back as commit f1c131b454
("crypto: xts - Convert to skcipher"). However, the issue only got
exposed by the much more recent changes to how the crypto API runs the
self-tests, so there should be no need to backport this to very old
kernels. Also, an alternative fix would be to flip the list iteration
order in crypto_start_tests() to restore the original testing order.
I'm thinking we should do that too, since the original order seems more
natural, but it shouldn't be relied on for correctness.
Fixes: adad556efc ("crypto: api - Fix built-in testing dependency failures")
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
In case a health test error occurs during runtime, the power-up health
tests are rerun to verify that the noise source is still good and
that the reported health test error was an outlier. For performing this
power-up health test, the already existing entropy collector instance
is used instead of allocating a new one. This change has the following
implications:
* The noise that is collected as part of the newly run health tests is
inserted into the entropy collector and thus stirs the existing
data present in there further. Thus, the entropy collected during
the health test is not wasted. This is also allowed by SP800-90B.
* The power-on health test is not affected by the state of the entropy
collector, because it resets the APT / RCT state. The remainder of
the state is unrelated to the health test as it is only applied to
newly obtained time stamps.
This change also fixes a bug report about an allocation while in an
atomic lock (the lock is taken in jent_kcapi_random, jent_read_entropy
is called and this can call jent_entropy_init).
Fixes: 04597c8dd6 ("jitter - add RCT/APT support for different OSRs")
Reported-by: Dan Carpenter <dan.carpenter@linaro.org>
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
As skcipher spawns may be of the type lskcipher, only the common
fields may be accessed. This was already the case but use the
correct helpers to make this more obvious.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
As skcipher spawns may be of the type lskcipher, only the common
fields may be accessed. This was already the case but use the
correct helpers to make this more obvious.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
As skcipher spawns may be of the type lskcipher, only the common
fields may be accessed. This was already the case but use the
correct helpers to make this more obvious.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
As skcipher spawns may be of the type lskcipher, only the common
fields may be accessed. This was already the case but use the
correct helpers to make this more obvious.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
As skcipher spawns may be of the type lskcipher, only the common
fields may be accessed. This was already the case but use the
correct helpers to make this more obvious.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
As skcipher spawns may be of the type lskcipher, only the common
fields may be accessed. This was already the case but use the
correct helpers to make this more obvious.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
As skcipher spawns may be of the type lskcipher, only the common
fields may be accessed. This was already the case but use the
correct helpers to make this more obvious.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
As skcipher spawns may be of the type lskcipher, only the common
fields may be accessed. This was already the case but use the
correct helpers to make this more obvious.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
As skcipher spawns may be of the type lskcipher, only the common
fields may be accessed. This was already the case but use the
correct helpers to make this more obvious.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
As skcipher spawns may be of the type lskcipher, only the common
fields may be accessed. This was already the case but use the
correct helpers to make this more obvious.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
As skcipher spawns may be of the type lskcipher, only the common
fields may be accessed. This was already the case but use the
correct helpers to make this more obvious.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Dimitri John Ledkov