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scram: fix HMAC-SHA-512

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HMAC was originally implemented for SHA1 digest according to RFC2104.
The RFC defined blocksize for all digests as 64 bytes. But RFC4868
requires blocksize for SHA384/SHA512 to be 128 bytes.

Extend HMAC implementation to support variable blocksize and fix it for
SHA384/SHA512.
This commit is contained in:
Dmitry Podgorny
2020-01-13 00:58:13 +02:00
parent 1ca10fd167
commit faa46d28a5
1 changed files with 14 additions and 10 deletions
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24
src/scram.c
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@@ -27,7 +27,7 @@
#include "scram.h" #include "scram.h"
#define HMAC_BLOCK_SIZE 64 #define HMAC_BLOCK_SIZE_MAX 128
static const uint8_t ipad = 0x36; static const uint8_t ipad = 0x36;
static const uint8_t opad = 0x5C; static const uint8_t opad = 0x5C;
@@ -72,33 +72,37 @@ static void crypto_HMAC(const struct hash_alg *alg,
size_t len, size_t len,
uint8_t *digest) uint8_t *digest)
{ {
uint8_t key_pad[HMAC_BLOCK_SIZE]; uint8_t key_pad[HMAC_BLOCK_SIZE_MAX];
uint8_t key_ipad[HMAC_BLOCK_SIZE]; uint8_t key_ipad[HMAC_BLOCK_SIZE_MAX];
uint8_t key_opad[HMAC_BLOCK_SIZE]; uint8_t key_opad[HMAC_BLOCK_SIZE_MAX];
uint8_t sha_digest[SCRAM_DIGEST_SIZE]; uint8_t sha_digest[SCRAM_DIGEST_SIZE];
int i; size_t blocksize;
size_t i;
union common_hash_ctx ctx; union common_hash_ctx ctx;
memset(key_pad, 0, sizeof(key_pad)); assert(alg->digest_size <= HMAC_BLOCK_SIZE_MAX);
if (key_len <= HMAC_BLOCK_SIZE) { blocksize = alg->digest_size < 48 ? 64 : 128;
memset(key_pad, 0, blocksize);
if (key_len <= blocksize) {
memcpy(key_pad, key, key_len); memcpy(key_pad, key, key_len);
} else { } else {
/* according to RFC2104 */ /* according to RFC2104 */
alg->hash(key, key_len, key_pad); alg->hash(key, key_len, key_pad);
} }
for (i = 0; i < HMAC_BLOCK_SIZE; i++) { for (i = 0; i < blocksize; i++) {
key_ipad[i] = key_pad[i] ^ ipad; key_ipad[i] = key_pad[i] ^ ipad;
key_opad[i] = key_pad[i] ^ opad; key_opad[i] = key_pad[i] ^ opad;
} }
alg->init((void *)&ctx); alg->init((void *)&ctx);
alg->update((void *)&ctx, key_ipad, HMAC_BLOCK_SIZE); alg->update((void *)&ctx, key_ipad, blocksize);
alg->update((void *)&ctx, text, len); alg->update((void *)&ctx, text, len);
alg->final((void *)&ctx, sha_digest); alg->final((void *)&ctx, sha_digest);
alg->init((void *)&ctx); alg->init((void *)&ctx);
alg->update((void *)&ctx, key_opad, HMAC_BLOCK_SIZE); alg->update((void *)&ctx, key_opad, blocksize);
alg->update((void *)&ctx, sha_digest, alg->digest_size); alg->update((void *)&ctx, sha_digest, alg->digest_size);
alg->final((void *)&ctx, digest); alg->final((void *)&ctx, digest);
} }