Mercurial > dropbear
view libtomcrypt/src/pk/pkcs1/pkcs_1_pss_decode.c @ 1938:77bc00dcc19f default tip main master
Bump version to 2022.82
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Fri, 01 Apr 2022 14:43:27 +0800 |
parents | 6dba84798cd5 |
children |
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/* LibTomCrypt, modular cryptographic library -- Tom St Denis * * LibTomCrypt is a library that provides various cryptographic * algorithms in a highly modular and flexible manner. * * The library is free for all purposes without any express * guarantee it works. */ #include "tomcrypt.h" /** @file pkcs_1_pss_decode.c PKCS #1 PSS Signature Padding, Tom St Denis */ #ifdef LTC_PKCS_1 /** PKCS #1 v2.00 PSS decode @param msghash The hash to verify @param msghashlen The length of the hash (octets) @param sig The signature data (encoded data) @param siglen The length of the signature data (octets) @param saltlen The length of the salt used (octets) @param hash_idx The index of the hash desired @param modulus_bitlen The bit length of the RSA modulus @param res [out] The result of the comparison, 1==valid, 0==invalid @return CRYPT_OK if successful (even if the comparison failed) */ int pkcs_1_pss_decode(const unsigned char *msghash, unsigned long msghashlen, const unsigned char *sig, unsigned long siglen, unsigned long saltlen, int hash_idx, unsigned long modulus_bitlen, int *res) { unsigned char *DB, *mask, *salt, *hash; unsigned long x, y, hLen, modulus_len; int err; hash_state md; LTC_ARGCHK(msghash != NULL); LTC_ARGCHK(res != NULL); /* default to invalid */ *res = 0; /* ensure hash is valid */ if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) { return err; } hLen = hash_descriptor[hash_idx].hashsize; modulus_bitlen--; modulus_len = (modulus_bitlen>>3) + (modulus_bitlen & 7 ? 1 : 0); /* check sizes */ if ((saltlen > modulus_len) || (modulus_len < hLen + saltlen + 2)) { return CRYPT_PK_INVALID_SIZE; } /* allocate ram for DB/mask/salt/hash of size modulus_len */ DB = XMALLOC(modulus_len); mask = XMALLOC(modulus_len); salt = XMALLOC(modulus_len); hash = XMALLOC(modulus_len); if (DB == NULL || mask == NULL || salt == NULL || hash == NULL) { if (DB != NULL) { XFREE(DB); } if (mask != NULL) { XFREE(mask); } if (salt != NULL) { XFREE(salt); } if (hash != NULL) { XFREE(hash); } return CRYPT_MEM; } /* ensure the 0xBC byte */ if (sig[siglen-1] != 0xBC) { err = CRYPT_INVALID_PACKET; goto LBL_ERR; } /* copy out the DB */ x = 0; XMEMCPY(DB, sig + x, modulus_len - hLen - 1); x += modulus_len - hLen - 1; /* copy out the hash */ XMEMCPY(hash, sig + x, hLen); /* x += hLen; */ /* check the MSB */ if ((sig[0] & ~(0xFF >> ((modulus_len<<3) - (modulus_bitlen)))) != 0) { err = CRYPT_INVALID_PACKET; goto LBL_ERR; } /* generate mask of length modulus_len - hLen - 1 from hash */ if ((err = pkcs_1_mgf1(hash_idx, hash, hLen, mask, modulus_len - hLen - 1)) != CRYPT_OK) { goto LBL_ERR; } /* xor against DB */ for (y = 0; y < (modulus_len - hLen - 1); y++) { DB[y] ^= mask[y]; } /* now clear the first byte [make sure smaller than modulus] */ DB[0] &= 0xFF >> ((modulus_len<<3) - (modulus_bitlen)); /* DB = PS || 0x01 || salt, PS == modulus_len - saltlen - hLen - 2 zero bytes */ /* check for zeroes and 0x01 */ for (x = 0; x < modulus_len - saltlen - hLen - 2; x++) { if (DB[x] != 0x00) { err = CRYPT_INVALID_PACKET; goto LBL_ERR; } } /* check for the 0x01 */ if (DB[x++] != 0x01) { err = CRYPT_INVALID_PACKET; goto LBL_ERR; } /* M = (eight) 0x00 || msghash || salt, mask = H(M) */ if ((err = hash_descriptor[hash_idx].init(&md)) != CRYPT_OK) { goto LBL_ERR; } zeromem(mask, 8); if ((err = hash_descriptor[hash_idx].process(&md, mask, 8)) != CRYPT_OK) { goto LBL_ERR; } if ((err = hash_descriptor[hash_idx].process(&md, msghash, msghashlen)) != CRYPT_OK) { goto LBL_ERR; } if ((err = hash_descriptor[hash_idx].process(&md, DB+x, saltlen)) != CRYPT_OK) { goto LBL_ERR; } if ((err = hash_descriptor[hash_idx].done(&md, mask)) != CRYPT_OK) { goto LBL_ERR; } /* mask == hash means valid signature */ if (XMEM_NEQ(mask, hash, hLen) == 0) { *res = 1; } err = CRYPT_OK; LBL_ERR: #ifdef LTC_CLEAN_STACK zeromem(DB, modulus_len); zeromem(mask, modulus_len); zeromem(salt, modulus_len); zeromem(hash, modulus_len); #endif XFREE(hash); XFREE(salt); XFREE(mask); XFREE(DB); return err; } #endif /* LTC_PKCS_1 */ /* ref: $Format:%D$ */ /* git commit: $Format:%H$ */ /* commit time: $Format:%ai$ */