67 lines
1.7 KiB
C
67 lines
1.7 KiB
C
/* LibTomCrypt, modular cryptographic library -- Tom St Denis
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*
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* LibTomCrypt is a library that provides various cryptographic
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* algorithms in a highly modular and flexible manner.
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*
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* The library is free for all purposes without any express
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* guarantee it works.
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*
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* Tom St Denis, tomstdenis@iahu.ca, http://libtomcrypt.org
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*/
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#include "mycrypt.h"
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#ifdef MRSA
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/* decrypt then PKCS #1 v1.5 depad */
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int rsa_v15_decrypt_key(const unsigned char *in, unsigned long inlen,
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unsigned char *outkey, unsigned long keylen,
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prng_state *prng, int prng_idx,
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int *res, rsa_key *key)
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{
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unsigned long modulus_bitlen, modulus_bytelen, x;
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int err;
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unsigned char *tmp;
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_ARGCHK(outkey != NULL);
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_ARGCHK(key != NULL);
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_ARGCHK(res != NULL);
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/* default to invalid */
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*res = 0;
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/* valid prng ? */
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if ((err = prng_is_valid(prng_idx)) != CRYPT_OK) {
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return err;
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}
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/* get modulus len in bits */
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modulus_bitlen = mp_count_bits(&(key->N));
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/* outlen must be at least the size of the modulus */
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modulus_bytelen = mp_unsigned_bin_size(&(key->N));
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if (modulus_bytelen != inlen) {
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return CRYPT_INVALID_PACKET;
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}
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/* allocate ram */
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tmp = XMALLOC(inlen);
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if (tmp == NULL) {
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return CRYPT_MEM;
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}
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/* rsa decode the packet */
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x = inlen;
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if ((err = rsa_exptmod(in, inlen, tmp, &x, PK_PRIVATE, prng, prng_idx, key)) != CRYPT_OK) {
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XFREE(tmp);
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return err;
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}
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/* PKCS #1 v1.5 depad */
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err = pkcs_1_v15_es_decode(tmp, x, modulus_bitlen, outkey, keylen, res);
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XFREE(tmp);
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return err;
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}
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#endif
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