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DSA: properly handle FIPS 186-4 (4.6 + 4.7)

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Karel Miko 2016-10-10 21:51:22 +02:00 committed by karel-m
parent 498538f6ef
commit ecbac7324e
2 changed files with 6 additions and 0 deletions
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3
src/pk/dsa/dsa_sign_hash.c
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@ -84,6 +84,9 @@ retry:
if (mp_iszero(r) == LTC_MP_YES) { goto retry; } if (mp_iszero(r) == LTC_MP_YES) { goto retry; }
/* FIPS 186-4 4.6: use leftmost min(bitlen(q), bitlen(hash)) */
if (inlen > (unsigned long)(key->qord)) inlen = (unsigned long)(key->qord);
/* now find s = (in + xr)/k mod q */ /* now find s = (in + xr)/k mod q */
if ((err = mp_read_unsigned_bin(tmp, (unsigned char *)in, inlen)) != CRYPT_OK) { goto error; } if ((err = mp_read_unsigned_bin(tmp, (unsigned char *)in, inlen)) != CRYPT_OK) { goto error; }
if ((err = mp_mul(key->x, r, s)) != CRYPT_OK) { goto error; } if ((err = mp_mul(key->x, r, s)) != CRYPT_OK) { goto error; }

3
src/pk/dsa/dsa_verify_hash.c
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@ -54,6 +54,9 @@ int dsa_verify_hash_raw( void *r, void *s,
goto error; goto error;
} }
/* FIPS 186-4 4.7: use leftmost min(bitlen(q), bitlen(hash)) bits of 'hash' */
if (hashlen > (unsigned long)(key->qord)) hashlen = (unsigned long)(key->qord);
/* w = 1/s mod q */ /* w = 1/s mod q */
if ((err = mp_invmod(s, key->q, w)) != CRYPT_OK) { goto error; } if ((err = mp_invmod(s, key->q, w)) != CRYPT_OK) { goto error; }