Mercurial > dropbear
view libtomcrypt/src/pk/pkcs1/pkcs_1_oaep_encode.c @ 397:2908122e9eed channel-fix
disapproval of revision '1250b8af44b62d8f4fe0f8d9fc7e7a1cc34e7e1c'
author | Matt Johnston <matt@ucc.asn.au> |
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date | Sat, 03 Feb 2007 08:10:09 +0000 |
parents | 1b9e69c058d2 |
children | 0cbe8f6dbf9e |
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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, [email protected], http://libtomcrypt.org */ #include "tomcrypt.h" /** @file pkcs_1_oaep_encode.c OAEP Padding for PKCS #1, Tom St Denis */ #ifdef PKCS_1 /** PKCS #1 v2.00 OAEP encode @param msg The data to encode @param msglen The length of the data to encode (octets) @param lparam A session or system parameter (can be NULL) @param lparamlen The length of the lparam data @param modulus_bitlen The bit length of the RSA modulus @param prng An active PRNG state @param prng_idx The index of the PRNG desired @param hash_idx The index of the hash desired @param out [out] The destination for the encoded data @param outlen [in/out] The max size and resulting size of the encoded data @return CRYPT_OK if successful */ int pkcs_1_oaep_encode(const unsigned char *msg, unsigned long msglen, const unsigned char *lparam, unsigned long lparamlen, unsigned long modulus_bitlen, prng_state *prng, int prng_idx, int hash_idx, unsigned char *out, unsigned long *outlen) { unsigned char *DB, *seed, *mask; unsigned long hLen, x, y, modulus_len; int err; LTC_ARGCHK(msg != NULL); LTC_ARGCHK(out != NULL); LTC_ARGCHK(outlen != NULL); /* test valid hash */ if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) { return err; } /* valid prng */ 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); /* test message size */ if ((2*hLen >= (modulus_len - 2)) || (msglen > (modulus_len - 2*hLen - 2))) { return CRYPT_PK_INVALID_SIZE; } /* allocate ram for DB/mask/salt of size modulus_len */ DB = XMALLOC(modulus_len); mask = XMALLOC(modulus_len); seed = XMALLOC(hLen); if (DB == NULL || mask == NULL || seed == NULL) { if (DB != NULL) { XFREE(DB); } if (mask != NULL) { XFREE(mask); } if (seed != NULL) { XFREE(seed); } return CRYPT_MEM; } /* get lhash */ /* DB == lhash || PS || 0x01 || M, PS == k - mlen - 2hlen - 2 zeroes */ x = modulus_len; if (lparam != NULL) { if ((err = hash_memory(hash_idx, lparam, lparamlen, DB, &x)) != CRYPT_OK) { goto LBL_ERR; } } else { /* can't pass hash_memory a NULL so use DB with zero length */ if ((err = hash_memory(hash_idx, DB, 0, DB, &x)) != CRYPT_OK) { goto LBL_ERR; } } /* append PS then 0x01 (to lhash) */ x = hLen; y = modulus_len - msglen - 2*hLen - 2; XMEMSET(DB+x, 0, y); x += y; /* 0x01 byte */ DB[x++] = 0x01; /* message (length = msglen) */ XMEMCPY(DB+x, msg, msglen); x += msglen; /* now choose a random seed */ if (prng_descriptor[prng_idx].read(seed, hLen, prng) != hLen) { err = CRYPT_ERROR_READPRNG; goto LBL_ERR; } /* compute MGF1 of seed (k - hlen - 1) */ if ((err = pkcs_1_mgf1(seed, hLen, hash_idx, 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]; } /* compute MGF1 of maskedDB (hLen) */ if ((err = pkcs_1_mgf1(DB, modulus_len - hLen - 1, hash_idx, mask, hLen)) != CRYPT_OK) { goto LBL_ERR; } /* XOR against seed */ for (y = 0; y < hLen; y++) { seed[y] ^= mask[y]; } /* create string of length modulus_len */ if (*outlen < modulus_len) { err = CRYPT_BUFFER_OVERFLOW; goto LBL_ERR; } /* start output which is 0x00 || maskedSeed || maskedDB */ x = 0; out[x++] = 0x00; XMEMCPY(out+x, seed, hLen); x += hLen; XMEMCPY(out+x, DB, modulus_len - hLen - 1); x += modulus_len - hLen - 1; *outlen = x; err = CRYPT_OK; LBL_ERR: #ifdef LTC_CLEAN_STACK zeromem(DB, modulus_len); zeromem(seed, hLen); zeromem(mask, modulus_len); #endif XFREE(seed); XFREE(mask); XFREE(DB); return err; } #endif /* PKCS_1 */ /* $Source: /cvs/libtom/libtomcrypt/src/pk/pkcs1/pkcs_1_oaep_encode.c,v $ */ /* $Revision: 1.4 $ */ /* $Date: 2005/05/05 14:35:59 $ */