md: add variable length output interface

* cipher/crc.c (_gcry_digest_spec_crc32)
(_gcry_digest_spec_crc32_rfc1510, _gcry_digest_spec_crc24_rfc2440): Set
'extract' NULL.
* cipher/gostr3411-94.c (_gcry_digest_spec_gost3411_94)
(_gcry_digest_spec_gost3411_cp): Ditto.
* cipher/keccak.c (_gcry_digest_spec_sha3_224)
(_gcry_digest_spec_sha3_256, _gcry_digest_spec_sha3_384)
(_gcry_digest_spec_sha3_512): Ditto.
* cipher/md2.c (_gcry_digest_spec_md2): Ditto.
* cipher/md4.c (_gcry_digest_spec_md4): Ditto.
* cipher/md5.c (_gcry_digest_spec_md5): Ditto.
* cipher/rmd160.c (_gcry_digest_spec_rmd160): Ditto.
* cipher/sha1.c (_gcry_digest_spec_sha1): Ditto.
* cipher/sha256.c (_gcry_digest_spec_sha224)
(_gcry_digest_spec_sha256): Ditto.
* cipher/sha512.c (_gcry_digest_spec_sha384)
(_gcry_digest_spec_sha512): Ditto.
* cipher/stribog.c (_gcry_digest_spec_stribog_256)
(_gcry_digest_spec_stribog_512): Ditto.
* cipher/tiger.c (_gcry_digest_spec_tiger)
(_gcry_digest_spec_tiger1, _gcry_digest_spec_tiger2): Ditto.
* cipher/whirlpool.c (_gcry_digest_spec_whirlpool): Ditto.
* cipher/md.c (md_enable): Do not allow combination of HMAC and
'expandable-output function'.
(md_final): Check if spec->read is NULL before calling.
(md_read): Ditto.
(md_extract, _gcry_md_extract): New.
* doc/gcrypt.texi: Add SHA3 algorithms and gcry_md_extract.
* src/cipher-proto.h (gcry_md_extract_t): New.
(gcry_md_spec_t): Add 'extract'.
* src/gcrypt-int.g (_gcry_md_extract): New.
* src/gcrypt.h.in (gcry_md_extract): New.
* src/libgcrypt.def: Add gcry_md_extract.
* src/libgcrypt.vers: Add gcry_md_extract.
* src/visibility.c (gcry_md_extract): New.
* src/visibility.h (gcry_md_extract): New.
--

Patch adds new interface for reading output from 'expandable-output
function' MD algorithms that can give variable length output (ie.
SHAKE algorithms from FIPS-202). New function to read output is

 gpg_error_t gcry_md_extract(gcry_md_hd_t md, int algo,
			     void *buffer, size_t length);

Function implicitly finalizes algorithm so that no new input can
be given. Subsequents calls of the function return more output
bytes from the algorithm.

Signed-off-by: Jussi Kivilinna <jussi.kivilinna@iki.fi>

1 files changed, 2 insertions, 0 deletions

diff --git a/src/gcrypt-int.h b/src/gcrypt-int.h
index 8014d617..d3673079 100644
--- a/src/gcrypt-int.h
+++ b/src/gcrypt-int.h
@@ -129,6 +129,8 @@ gpg_err_code_t _gcry_md_ctl (gcry_md_hd_t hd, int cmd,
                           void *buffer, size_t buflen);
 void _gcry_md_write (gcry_md_hd_t hd, const void *buffer, size_t length);
 unsigned char *_gcry_md_read (gcry_md_hd_t hd, int algo);
+gpg_error_t _gcry_md_extract (gcry_md_hd_t hd, int algo, void *buffer,
+                              size_t length);
 void _gcry_md_hash_buffer (int algo, void *digest,
                            const void *buffer, size_t length);
 gpg_err_code_t _gcry_md_hash_buffers (int algo, unsigned int flags,