Mercurial > dropbear
view libtomcrypt/src/pk/pkcs1/pkcs_1_oaep_decode.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_decode.c OAEP Padding for PKCS #1, Tom St Denis */ #ifdef PKCS_1 /** PKCS #1 v2.00 OAEP decode @param msg The encoded data to decode @param msglen The length of the encoded data (octets) @param lparam The session or system data (can be NULL) @param lparamlen The length of the lparam @param modulus_bitlen The bit length of the RSA modulus @param hash_idx The index of the hash desired @param out [out] Destination of decoding @param outlen [in/out] The max size and resulting size of the decoding @param res [out] Result of decoding, 1==valid, 0==invalid @return CRYPT_OK if successful (even if invalid) */ int pkcs_1_oaep_decode(const unsigned char *msg, unsigned long msglen, const unsigned char *lparam, unsigned long lparamlen, unsigned long modulus_bitlen, int hash_idx, unsigned char *out, unsigned long *outlen, int *res) { 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); LTC_ARGCHK(res != NULL); /* default to invalid packet */ *res = 0; /* test valid hash */ 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); /* test hash/message size */ if ((2*hLen >= (modulus_len - 2)) || (msglen != modulus_len)) { 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; } /* ok so it's now in the form 0x00 || maskedseed || maskedDB 1 || hLen || modulus_len - hLen - 1 */ /* must have leading 0x00 byte */ if (msg[0] != 0x00) { err = CRYPT_OK; goto LBL_ERR; } /* now read the masked seed */ x = 1; XMEMCPY(seed, msg + x, hLen); x += hLen; /* now read the masked DB */ XMEMCPY(DB, msg + x, modulus_len - hLen - 1); x += modulus_len - hLen - 1; /* 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]; } /* 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]; } /* now DB == lhash || PS || 0x01 || M, PS == k - mlen - 2hlen - 2 zeroes */ /* compute lhash and store it in seed [reuse temps!] */ x = modulus_len; if (lparam != NULL) { if ((err = hash_memory(hash_idx, lparam, lparamlen, seed, &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, seed, &x)) != CRYPT_OK) { goto LBL_ERR; } } /* compare the lhash'es */ if (memcmp(seed, DB, hLen) != 0) { err = CRYPT_OK; goto LBL_ERR; } /* now zeroes before a 0x01 */ for (x = hLen; x < (modulus_len - hLen - 1) && DB[x] == 0x00; x++) { /* step... */ } /* error out if wasn't 0x01 */ if (x == (modulus_len - hLen - 1) || DB[x] != 0x01) { err = CRYPT_OK; goto LBL_ERR; } /* rest is the message (and skip 0x01) */ if ((modulus_len - hLen - 1) - ++x > *outlen) { err = CRYPT_BUFFER_OVERFLOW; goto LBL_ERR; } /* copy message */ *outlen = (modulus_len - hLen - 1) - x; XMEMCPY(out, DB + x, modulus_len - hLen - 1 - x); x += modulus_len - hLen - 1; /* valid packet */ *res = 1; 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_decode.c,v $ */ /* $Revision: 1.5 $ */ /* $Date: 2005/06/18 02:37:06 $ */