diff options
Diffstat (limited to 'libtomcrypt/src/pk/pkcs1/pkcs_1_pss_decode.c')
| -rw-r--r-- | libtomcrypt/src/pk/pkcs1/pkcs_1_pss_decode.c | 177 |
1 files changed, 177 insertions, 0 deletions
diff --git a/libtomcrypt/src/pk/pkcs1/pkcs_1_pss_decode.c b/libtomcrypt/src/pk/pkcs1/pkcs_1_pss_decode.c new file mode 100644 index 0000000..2c16d50 --- /dev/null +++ b/libtomcrypt/src/pk/pkcs1/pkcs_1_pss_decode.c @@ -0,0 +1,177 @@ +/* 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.com + */ +#include "tomcrypt.h" + +/** + @file pkcs_1_pss_decode.c + PKCS #1 PSS Signature Padding, Tom St Denis +*/ + +#ifdef 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_len = (modulus_bitlen>>3) + (modulus_bitlen & 7 ? 1 : 0); + + /* check sizes */ + if ((saltlen > modulus_len) || + (modulus_len < hLen + saltlen + 2) || (siglen != modulus_len)) { + 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-1)))) != 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-1)); + + /* 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 (XMEMCMP(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 /* PKCS_1 */ + +/* $Source: /cvs/libtom/libtomcrypt/src/pk/pkcs1/pkcs_1_pss_decode.c,v $ */ +/* $Revision: 1.9 $ */ +/* $Date: 2006/11/30 02:37:21 $ */ |