This patch adds the helpers crypto_clone_ahash and crypto_clone_shash.
They are the hash-specific counterparts of crypto_clone_tfm.
This allows code paths that cannot otherwise allocate a hash tfm
object to do so. Once a new tfm has been obtained its key could
then be changed without impacting other users.
Note that only algorithms that implement clone_tfm can be cloned.
However, all keyless hashes can be cloned by simply reusing the
tfm object.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: Simon Horman <simon.horman@corigine.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The HASH_ALG_COMMON macro cannot be parsed by kdoc so mark it as
a normal comment instead of kdoc. Also add HASH_ALG_COMMON as a
structure member of shash_alg.
Fixes: 0e4e6d7094df ("crypto: hash - Count error stats differently")
Reported-by: Stephen Rothwell <sfr@canb.auug.org.au>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Move all stat code specific to hash into the hash code.
While we're at it, change the stats so that bytes and counts
are always incremented even in case of error. This allows the
reference counting to be removed as we can now increment the
counters prior to the operation.
After the operation we simply increase the error count if necessary.
This is safe as errors can only occur synchronously (or rather,
the existing code already ignored asynchronous errors which are
only visible to the callback function).
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Add helper function to determine if a given synchronous hash is supported.
Signed-off-by: Hannes Reinecke <hare@suse.de>
Reviewed-by: Sagi Grimberg <sagi@grimberg.me>
Reviewed-by: Chaitanya Kulkarni <kch@nvidia.com>
Reviewed-by: Himanshu Madhani <himanshu.madhani@oracle.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: Christoph Hellwig <hch@lst.de>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Given that crypto_alloc_tfm() may return ERR pointers, and to avoid
crashes on obscure error paths where such pointers are presented to
crypto_destroy_tfm() (such as [0]), add an ERR_PTR check there
before dereferencing the second argument as a struct crypto_tfm
pointer.
[0] https://lore.kernel.org/linux-crypto/000000000000de949705bc59e0f6@google.com/
Reported-by: syzbot+12cf5fbfdeba210a89dd@syzkaller.appspotmail.com
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Unlike many other structure types defined in the crypto API, the
'shash_desc' structure is permitted to live on the stack, which
implies its contents may not be accessed by DMA masters. (This is
due to the fact that the stack may be located in the vmalloc area,
which requires a different virtual-to-physical translation than the
one implemented by the DMA subsystem)
Our definition of CRYPTO_MINALIGN_ATTR is based on ARCH_KMALLOC_MINALIGN,
which may take DMA constraints into account on architectures that support
non-cache coherent DMA such as ARM and arm64. In this case, the value is
chosen to reflect the largest cacheline size in the system, in order to
ensure that explicit cache maintenance as required by non-coherent DMA
masters does not affect adjacent, unrelated slab allocations. On arm64,
this value is currently set at 128 bytes.
This means that applying CRYPTO_MINALIGN_ATTR to struct shash_desc is both
unnecessary (as it is never used for DMA), and undesirable, given that it
wastes stack space (on arm64, performing the alignment costs 112 bytes in
the worst case, and the hole between the 'tfm' and '__ctx' members takes
up another 120 bytes, resulting in an increased stack footprint of up to
232 bytes.) So instead, let's switch to the minimum SLAB alignment, which
does not take DMA constraints into account.
Note that this is a no-op for x86.
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This patch removes AHASH_REQUEST_ON_STACK which is unused.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This patch adds the type-safe init_tfm/exit_tfm functions to the
ahash interface. This is meant to replace the unsafe cra_init and
cra_exit interface.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
As said by Linus:
A symmetric naming is only helpful if it implies symmetries in use.
Otherwise it's actively misleading.
In "kzalloc()", the z is meaningful and an important part of what the
caller wants.
In "kzfree()", the z is actively detrimental, because maybe in the
future we really _might_ want to use that "memfill(0xdeadbeef)" or
something. The "zero" part of the interface isn't even _relevant_.
The main reason that kzfree() exists is to clear sensitive information
that should not be leaked to other future users of the same memory
objects.
Rename kzfree() to kfree_sensitive() to follow the example of the recently
added kvfree_sensitive() and make the intention of the API more explicit.
In addition, memzero_explicit() is used to clear the memory to make sure
that it won't get optimized away by the compiler.
The renaming is done by using the command sequence:
git grep -w --name-only kzfree |\
xargs sed -i 's/kzfree/kfree_sensitive/'
followed by some editing of the kfree_sensitive() kerneldoc and adding
a kzfree backward compatibility macro in slab.h.
[akpm@linux-foundation.org: fs/crypto/inline_crypt.c needs linux/slab.h]
[akpm@linux-foundation.org: fix fs/crypto/inline_crypt.c some more]
Suggested-by: Joe Perches <joe@perches.com>
Signed-off-by: Waiman Long <longman@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Acked-by: David Howells <dhowells@redhat.com>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Johannes Weiner <hannes@cmpxchg.org>
Cc: Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>
Cc: James Morris <jmorris@namei.org>
Cc: "Serge E. Hallyn" <serge@hallyn.com>
Cc: Joe Perches <joe@perches.com>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: David Rientjes <rientjes@google.com>
Cc: Dan Carpenter <dan.carpenter@oracle.com>
Cc: "Jason A . Donenfeld" <Jason@zx2c4.com>
Link: http://lkml.kernel.org/r/20200616154311.12314-3-longman@redhat.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Drop the doubled word "in" in a comment.
Signed-off-by: Randy Dunlap <rdunlap@infradead.org>
Cc: Herbert Xu <herbert@gondor.apana.org.au>
Cc: "David S. Miller" <davem@davemloft.net>
Cc: linux-crypto@vger.kernel.org
Acked-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Currently the simplest use of the shash API is to use
crypto_shash_digest() to digest a whole buffer. However, this still
requires allocating a hash descriptor (struct shash_desc). Many users
don't really want to preallocate one and instead just use a one-off
descriptor on the stack like the following:
{
SHASH_DESC_ON_STACK(desc, tfm);
int err;
desc->tfm = tfm;
err = crypto_shash_digest(desc, data, len, out);
shash_desc_zero(desc);
}
Wrap this in a new helper function crypto_shash_tfm_digest() that can be
used instead of the above.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The shash interface supports a dynamic descsize field because of
the presence of fallbacks (it's just padlock-sha actually, perhaps
we can remove it one day). As it is the API does not verify the
setting of descsize at all. It is up to the individual algorithms
to ensure that descsize does not exceed the specified maximum value
of HASH_MAX_DESCSIZE (going above would cause stack corruption).
In order to allow the API to impose this limit directly, this patch
adds init_tfm/exit_tfm hooks to the shash_alg structure. We can
then verify the descsize setting in the API directly.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Reviewed-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Now that all users of the deprecated ablkcipher interface have been
moved to the skcipher interface, ablkcipher is no longer used and
can be removed.
Reviewed-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Based on 1 normalized pattern(s):
this program is free software you can redistribute it and or modify
it under the terms of the gnu general public license as published by
the free software foundation either version 2 of the license or at
your option any later version
extracted by the scancode license scanner the SPDX license identifier
GPL-2.0-or-later
has been chosen to replace the boilerplate/reference in 3029 file(s).
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Reviewed-by: Allison Randal <allison@lohutok.net>
Cc: linux-spdx@vger.kernel.org
Link: https://lkml.kernel.org/r/20190527070032.746973796@linutronix.de
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
The "hmac(sha3-224-generic)" algorithm has a descsize of 368 bytes,
which is greater than HASH_MAX_DESCSIZE (360) which is only enough for
sha3-224-generic. The check in shash_prepare_alg() doesn't catch this
because the HMAC template doesn't set descsize on the algorithms, but
rather sets it on each individual HMAC transform.
This causes a stack buffer overflow when SHASH_DESC_ON_STACK() is used
with hmac(sha3-224-generic).
Fix it by increasing HASH_MAX_DESCSIZE to the real maximum. Also add a
sanity check to hmac_init().
This was detected by the improved crypto self-tests in v5.2, by loading
the tcrypt module with CONFIG_CRYPTO_MANAGER_EXTRA_TESTS=y enabled. I
didn't notice this bug when I ran the self-tests by requesting the
algorithms via AF_ALG (i.e., not using tcrypt), probably because the
stack layout differs in the two cases and that made a difference here.
KASAN report:
BUG: KASAN: stack-out-of-bounds in memcpy include/linux/string.h:359 [inline]
BUG: KASAN: stack-out-of-bounds in shash_default_import+0x52/0x80 crypto/shash.c:223
Write of size 360 at addr ffff8880651defc8 by task insmod/3689
CPU: 2 PID: 3689 Comm: insmod Tainted: G E 5.1.0-10741-g35c99ffa20edd #11
Hardware name: QEMU Standard PC (i440FX + PIIX, 1996), BIOS 1.10.2-1 04/01/2014
Call Trace:
__dump_stack lib/dump_stack.c:77 [inline]
dump_stack+0x86/0xc5 lib/dump_stack.c:113
print_address_description+0x7f/0x260 mm/kasan/report.c:188
__kasan_report+0x144/0x187 mm/kasan/report.c:317
kasan_report+0x12/0x20 mm/kasan/common.c:614
check_memory_region_inline mm/kasan/generic.c:185 [inline]
check_memory_region+0x137/0x190 mm/kasan/generic.c:191
memcpy+0x37/0x50 mm/kasan/common.c:125
memcpy include/linux/string.h:359 [inline]
shash_default_import+0x52/0x80 crypto/shash.c:223
crypto_shash_import include/crypto/hash.h:880 [inline]
hmac_import+0x184/0x240 crypto/hmac.c:102
hmac_init+0x96/0xc0 crypto/hmac.c:107
crypto_shash_init include/crypto/hash.h:902 [inline]
shash_digest_unaligned+0x9f/0xf0 crypto/shash.c:194
crypto_shash_digest+0xe9/0x1b0 crypto/shash.c:211
generate_random_hash_testvec.constprop.11+0x1ec/0x5b0 crypto/testmgr.c:1331
test_hash_vs_generic_impl+0x3f7/0x5c0 crypto/testmgr.c:1420
__alg_test_hash+0x26d/0x340 crypto/testmgr.c:1502
alg_test_hash+0x22e/0x330 crypto/testmgr.c:1552
alg_test.part.7+0x132/0x610 crypto/testmgr.c:4931
alg_test+0x1f/0x40 crypto/testmgr.c:4952
Fixes: b68a7ec1e9 ("crypto: hash - Remove VLA usage")
Reported-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Cc: <stable@vger.kernel.org> # v4.20+
Cc: Kees Cook <keescook@chromium.org>
Signed-off-by: Eric Biggers <ebiggers@google.com>
Reviewed-by: Kees Cook <keescook@chromium.org>
Tested-by: Corentin Labbe <clabbe.montjoie@gmail.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The flags field in 'struct shash_desc' never actually does anything.
The only ostensibly supported flag is CRYPTO_TFM_REQ_MAY_SLEEP.
However, no shash algorithm ever sleeps, making this flag a no-op.
With this being the case, inevitably some users who can't sleep wrongly
pass MAY_SLEEP. These would all need to be fixed if any shash algorithm
actually started sleeping. For example, the shash_ahash_*() functions,
which wrap a shash algorithm with the ahash API, pass through MAY_SLEEP
from the ahash API to the shash API. However, the shash functions are
called under kmap_atomic(), so actually they're assumed to never sleep.
Even if it turns out that some users do need preemption points while
hashing large buffers, we could easily provide a helper function
crypto_shash_update_large() which divides the data into smaller chunks
and calls crypto_shash_update() and cond_resched() for each chunk. It's
not necessary to have a flag in 'struct shash_desc', nor is it necessary
to make individual shash algorithms aware of this at all.
Therefore, remove shash_desc::flags, and document that the
crypto_shash_*() functions can be called from any context.
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
All crypto_stats functions use the struct xxx_request for feeding stats,
but in some case this structure could already be freed.
For fixing this, the needed parameters (len and alg) will be stored
before the request being executed.
Fixes: cac5818c25 ("crypto: user - Implement a generic crypto statistics")
Reported-by: syzbot <syzbot+6939a606a5305e9e9799@syzkaller.appspotmail.com>
Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
All the 32-bit fields need to be 64-bit. In some cases, UINT32_MAX crypto
operations can be done in seconds.
Reported-by: Eric Biggers <ebiggers@kernel.org>
Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This patch implement a generic way to get statistics about all crypto
usages.
Signed-off-by: Corentin Labbe <clabbe@baylibre.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
In the quest to remove all stack VLA usage from the kernel[1], this
removes the VLAs in SHASH_DESC_ON_STACK (via crypto_shash_descsize())
by using the maximum allowable size (which is now more clearly captured
in a macro), along with a few other cases. Similar limits are turned into
macros as well.
A review of existing sizes shows that SHA512_DIGEST_SIZE (64) is the
largest digest size and that sizeof(struct sha3_state) (360) is the
largest descriptor size. The corresponding maximums are reduced.
[1] https://lkml.kernel.org/r/CA+55aFzCG-zNmZwX4A2FQpadafLfEzK6CC=qPXydAacU1RqZWA@mail.gmail.com
Signed-off-by: Kees Cook <keescook@chromium.org>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Prevent improper use of req->result field in ahash update, init, export and
import functions in drivers code. A driver should use ahash request context
if it needs to save internal state.
Signed-off-by: Kamil Konieczny <k.konieczny@partner.samsung.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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: Tobin C. Harding <me@tobin.cc>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
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: syzbot <syzkaller@googlegroups.com>
Cc: stable@vger.kernel.org
Signed-off-by: Eric Biggers <ebiggers@google.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
* fix documentation of return values for crypto_ahash_init(),
crypto_ahash_finup(), crypto_ahash_final(),
crypto_ahash_digest() and crypto_ahash_update()
Also while at it:
* add notes for device driver developers in struct ahash_alg
description
* fix description of @final method in struct ahash_alg
* fix typo in crypto_ahash_finup() description
Signed-off-by: Kamil Konieczny <k.konieczny@partner.samsung.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The documentation states that crypto_ahash_reqsize() provides the size
of the state structure used by crypto_ahash_export(). But it's actually
crypto_ahash_statesize() which provides this size.
Signed-off-by: Rabin Vincent <rabinv@axis.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Update comments to avoid any complaints from Sphinx during compilation.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Jonathan Corbet <corbet@lwn.net>
This patch adds helpers to retrieve the alg name and driver name
of crypto_shash and crypto_ahash objects.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
As the size of an ahash_request or shash_desc is variable, it's
awkward to zero them explicitly. This patch adds helpers to do
that which should be used when they are created on the stack.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This patch adds a way for ahash users to determine whether a key
is required by a crypto_ahash transform.
Cc: stable@vger.kernel.org
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This patch adds the missing helper crypto_ahash_blocksize which
returns the block size of an ahash algorithm.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This patch adds the helper AHASH_REQUEST_ON_STACK for those users
of ahash that are synchronous only.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This patch fix some typos found in crypto-API.xml.
It is because the file is generated from comments in sources,
so I had to fix typo in sources.
Signed-off-by: Masanari Iida <standby24x7@gmail.com>
Acked-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Fix documentation typo for shash_alg->descsize.
Add documentation for initially uncovered member variables.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The API function calls exported by the kernel crypto API for SHASHes
to be used by consumers are documented.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The API function calls exported by the kernel crypto API for AHASHes
to be used by consumers are documented.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
The hash data structures needed to be filled in by cipher developers are
documented.
Signed-off-by: Stephan Mueller <smueller@chronox.de>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Add a macro which replaces the use of a Variable Length Array In Struct (VLAIS)
with a C99 compliant equivalent. This macro instead allocates the appropriate
amount of memory using an char array.
The new code can be compiled with both gcc and clang.
struct shash_desc contains a flexible array member member ctx declared with
CRYPTO_MINALIGN_ATTR, so sizeof(struct shash_desc) aligns the beginning
of the array declared after struct shash_desc with long long.
No trailing padding is required because it is not a struct type that can
be used in an array.
The CRYPTO_MINALIGN_ATTR is required so that desc is aligned with long long
as would be the case for a struct containing a member with
CRYPTO_MINALIGN_ATTR.
If you want to get to the ctx at the end of the shash_desc as before you can do
so using shash_desc_ctx(shash)
Signed-off-by: Behan Webster <behanw@converseincode.com>
Reviewed-by: Mark Charlebois <charlebm@gmail.com>
Acked-by: Herbert Xu <herbert@gondor.apana.org.au>
Cc: Michał Mirosław <mirqus@gmail.com>
Change formal parameters to not clash with global names to
eliminate many W=2 warnings.
Signed-off-by: Mark Rustad <mark.d.rustad@intel.com>
Signed-off-by: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
When an shash algorithm is exported as ahash, ahash will access
its digest size through hash_alg_common. That's why the shash
layout needs to match hash_alg_common. This wasn't the case
because the alignment weren't identical.
This patch fixes the problem.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This patch exports the finup operation where available and adds
a default finup operation for ahash. The operations final, finup
and digest also will now deal with unaligned result pointers by
copying it. Finally export/import operations are will now be
exported too.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Now that all ahash implementations have been converted to the new
ahash type, we can remove old_ahash_alg and its associated support.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This patch converts crypto_ahash to the new style. The old ahash
algorithm type is retained until the existing ahash implementations
are also converted. All ahash users will automatically get the
new crypto_ahash type.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This patch changes descsize to a run-time attribute so that
implementations can change it in their init functions.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This patch changes the kfree call to kzfree for async requests.
As the request may contain sensitive data it needs to be zeroed
before it can be reallocated by others.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This patch replaces the full descriptor export with an export of
the partial hash state. This allows the use of a consistent export
format across all implementations of a given algorithm.
This is useful because a number of cases require the use of the
partial hash state, e.g., PadLock can use the SHA1 hash state
to get around the fact that it can only hash contiguous data
chunks.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
This function is needed by algorithms that don't know their own
block size, e.g., in s390 where the code is common between multiple
versions of SHA.
Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Herbert Xu