diff options
Diffstat (limited to 'libtomcrypt/src/pk/pkcs1/pkcs_1_pss_encode.c')
| -rw-r--r-- | libtomcrypt/src/pk/pkcs1/pkcs_1_pss_encode.c | 175 |
1 files changed, 175 insertions, 0 deletions
diff --git a/libtomcrypt/src/pk/pkcs1/pkcs_1_pss_encode.c b/libtomcrypt/src/pk/pkcs1/pkcs_1_pss_encode.c new file mode 100644 index 0000000..64bd312 --- /dev/null +++ b/libtomcrypt/src/pk/pkcs1/pkcs_1_pss_encode.c @@ -0,0 +1,175 @@ +/* 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_encode.c + PKCS #1 PSS Signature Padding, Tom St Denis +*/ + +#ifdef PKCS_1 + +/** + PKCS #1 v2.00 Signature Encoding + @param msghash The hash to encode + @param msghashlen The length of the hash (octets) + @param saltlen The length of the salt desired (octets) + @param prng An active PRNG context + @param prng_idx The index of the PRNG desired + @param hash_idx The index of the hash desired + @param modulus_bitlen The bit length of the RSA modulus + @param out [out] The destination of the encoding + @param outlen [in/out] The max size and resulting size of the encoded data + @return CRYPT_OK if successful +*/ +int pkcs_1_pss_encode(const unsigned char *msghash, unsigned long msghashlen, + unsigned long saltlen, prng_state *prng, + int prng_idx, int hash_idx, + unsigned long modulus_bitlen, + unsigned char *out, unsigned long *outlen) +{ + unsigned char *DB, *mask, *salt, *hash; + unsigned long x, y, hLen, modulus_len; + int err; + hash_state md; + + LTC_ARGCHK(msghash != NULL); + LTC_ARGCHK(out != NULL); + LTC_ARGCHK(outlen != NULL); + + /* ensure hash and PRNG are valid */ + if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) { + return err; + } + if ((err = prng_is_valid(prng_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)) { + 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; + } + + + /* generate random salt */ + if (saltlen > 0) { + if (prng_descriptor[prng_idx].read(salt, saltlen, prng) != saltlen) { + err = CRYPT_ERROR_READPRNG; + goto LBL_ERR; + } + } + + /* M = (eight) 0x00 || msghash || salt, hash = H(M) */ + if ((err = hash_descriptor[hash_idx].init(&md)) != CRYPT_OK) { + goto LBL_ERR; + } + zeromem(DB, 8); + if ((err = hash_descriptor[hash_idx].process(&md, DB, 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, salt, saltlen)) != CRYPT_OK) { + goto LBL_ERR; + } + if ((err = hash_descriptor[hash_idx].done(&md, hash)) != CRYPT_OK) { + goto LBL_ERR; + } + + /* generate DB = PS || 0x01 || salt, PS == modulus_len - saltlen - hLen - 2 zero bytes */ + x = 0; + XMEMSET(DB + x, 0, modulus_len - saltlen - hLen - 2); + x += modulus_len - saltlen - hLen - 2; + DB[x++] = 0x01; + XMEMCPY(DB + x, salt, saltlen); + x += saltlen; + + /* 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]; + } + + /* output is DB || hash || 0xBC */ + if (*outlen < modulus_len) { + *outlen = modulus_len; + err = CRYPT_BUFFER_OVERFLOW; + goto LBL_ERR; + } + + /* DB len = modulus_len - hLen - 1 */ + y = 0; + XMEMCPY(out + y, DB, modulus_len - hLen - 1); + y += modulus_len - hLen - 1; + + /* hash */ + XMEMCPY(out + y, hash, hLen); + y += hLen; + + /* 0xBC */ + out[y] = 0xBC; + + /* now clear the 8*modulus_len - modulus_bitlen most significant bits */ + out[0] &= 0xFF >> ((modulus_len<<3) - (modulus_bitlen-1)); + + /* store output size */ + *outlen = modulus_len; + 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_encode.c,v $ */ +/* $Revision: 1.7 $ */ +/* $Date: 2006/06/16 21:53:41 $ */ |