Disallow XOF algorithms for gcry_md_hash_bufferssanitizer-fixes

* cipher/md.c (_gcry_md_hash_buffer): Skip calculation for XOFs.
(_gcry_md_hash_buffers): Fail when XOFs are selected.
* doc/gcrypt.texi: Explicitly document above behavior for XOFs.
* tests/benchmark.c: Skip benchmarking hash functions without a fixed
output length.
--

Caught by UndefinedBehaviorSanitizer while running tests/benchmarks
where gcry_md_hash_buffer(GCRY_MD_SHAKE128) would result in
memcpy(digest, NULL, 0).

Signed-off-by: Peter Wu <peter@lekensteyn.nl>

1 files changed, 3 insertions, 1 deletions

diff --git a/doc/gcrypt.texi b/doc/gcrypt.texi
index 3265a706..9481be9e 100644
--- a/doc/gcrypt.texi
+++ b/doc/gcrypt.texi
@@ -3378,6 +3378,7 @@ described by @var{iov} and @var{iovcnt}.  @var{digest} must be
 allocated by the caller, large enough to hold the message digest
 yielded by the the specified algorithm @var{algo}.  This required size
 may be obtained by using the function @code{gcry_md_get_algo_dlen}.
+This function cannot be used for extendable-output functions.
 
 @var{iov} is an array of buffer descriptions with @var{iovcnt} items.
 The caller should zero out the structures in this array and for each
@@ -3402,7 +3403,8 @@ immediately returns the message digest of the @var{length} bytes at
 @var{buffer}.  @var{digest} must be allocated by the caller, large
 enough to hold the message digest yielded by the the specified algorithm
 @var{algo}.  This required size may be obtained by using the function
-@code{gcry_md_get_algo_dlen}.
+@code{gcry_md_get_algo_dlen}.  This function has no effect for
+extendable-output functions.
 
 Note that in contrast to @code{gcry_md_hash_buffers} this function
 will abort the process if an unavailable algorithm is used.