Mercurial > dropbear
view libtomcrypt/src/pk/pkcs1/pkcs_1_pss_encode.c @ 652:17962b2a6b8f
- Make sure we don't use channel-specific data after it has been freed
with a ChanType->closehandler()
author | Matt Johnston <matt@ucc.asn.au> |
---|---|
date | Sun, 04 Dec 2011 05:27:29 +0800 (2011-12-03) |
parents | 0cbe8f6dbf9e |
children | f849a5ca2efc |
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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. * * 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 $ */