| /* 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. |
| * |
| * Tom St Denis, tomstdenis@gmail.com, http://libtomcrypt.org |
| */ |
| #include "tomcrypt.h" |
| |
| /** |
| @file rsa_verify_hash.c |
| RSA PKCS v2 PSS signature verification, Tom St Denis |
| */ |
| |
| #ifdef MRSA |
| |
| /** |
| (PKCS #1, v2.0) de-sign then PSS depad |
| @param sig The signature data |
| @param siglen The length of the signature data (octets) |
| @param hash The hash of the message that was signed |
| @param hashlen The length of the hash of the message that was signed (octets) |
| @param hash_idx The index of the desired hash |
| @param saltlen The length of the salt used during signature |
| @param stat [out] The result of the signature comparison, 1==valid, 0==invalid |
| @param key The public RSA key corresponding to the key that performed the signature |
| @return CRYPT_OK on success (even if the signature is invalid) |
| */ |
| int rsa_verify_hash(const unsigned char *sig, unsigned long siglen, |
| const unsigned char *hash, unsigned long hashlen, |
| int hash_idx, unsigned long saltlen, |
| int *stat, rsa_key *key) |
| { |
| unsigned long modulus_bitlen, modulus_bytelen, x; |
| int err; |
| unsigned char *tmpbuf; |
| |
| LTC_ARGCHK(hash != NULL); |
| LTC_ARGCHK(sig != NULL); |
| LTC_ARGCHK(stat != NULL); |
| LTC_ARGCHK(key != NULL); |
| |
| /* default to invalid */ |
| *stat = 0; |
| |
| /* valid hash ? */ |
| if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) { |
| return err; |
| } |
| |
| /* get modulus len in bits */ |
| modulus_bitlen = mp_count_bits(&(key->N)); |
| |
| /* outlen must be at least the size of the modulus */ |
| modulus_bytelen = mp_unsigned_bin_size(&(key->N)); |
| if (modulus_bytelen != siglen) { |
| return CRYPT_INVALID_PACKET; |
| } |
| |
| /* allocate temp buffer for decoded sig */ |
| tmpbuf = XMALLOC(siglen); |
| if (tmpbuf == NULL) { |
| return CRYPT_MEM; |
| } |
| |
| /* RSA decode it */ |
| x = siglen; |
| if ((err = rsa_exptmod(sig, siglen, tmpbuf, &x, PK_PUBLIC, key)) != CRYPT_OK) { |
| XFREE(tmpbuf); |
| return err; |
| } |
| |
| /* PSS decode it */ |
| err = pkcs_1_pss_decode(hash, hashlen, tmpbuf, x, saltlen, hash_idx, modulus_bitlen, stat); |
| XFREE(tmpbuf); |
| return err; |
| } |
| |
| #endif /* MRSA */ |