annotate rsa_v15_verify_hash.c @ 164:cd1143579f00 libtomcrypt LTC_DB_0.44

mpi.c isn't needed if we're using libtommath seperately
author Matt Johnston <matt@ucc.asn.au>
date Sun, 02 Jan 2005 17:19:46 +0000
parents 5d99163f7e32
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1 /* LibTomCrypt, modular cryptographic library -- Tom St Denis
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2 *
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3 * LibTomCrypt is a library that provides various cryptographic
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4 * algorithms in a highly modular and flexible manner.
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5 *
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6 * The library is free for all purposes without any express
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7 * guarantee it works.
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8 *
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9 * Tom St Denis, [email protected], http://libtomcrypt.org
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10 */
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11
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12 #include "mycrypt.h"
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13
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14 #ifdef MRSA
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15
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16 /* de-sign then PKCS v1.5 depad */
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17 int rsa_v15_verify_hash(const unsigned char *sig, unsigned long siglen,
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18 const unsigned char *msghash, unsigned long msghashlen,
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19 prng_state *prng, int prng_idx,
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20 int hash_idx, int *stat,
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21 rsa_key *key)
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22 {
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23 unsigned long modulus_bitlen, modulus_bytelen, x;
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24 int err;
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25 unsigned char *tmpbuf;
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26
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27 _ARGCHK(msghash != NULL);
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28 _ARGCHK(sig != NULL);
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29 _ARGCHK(stat != NULL);
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30 _ARGCHK(key != NULL);
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31
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32 /* default to invalid */
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33 *stat = 0;
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34
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35 /* valid hash ? */
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36 if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) {
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37 return err;
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38 }
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39
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40 if ((err = prng_is_valid(prng_idx)) != CRYPT_OK) {
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41 return err;
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42 }
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43
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44 /* get modulus len in bits */
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45 modulus_bitlen = mp_count_bits(&(key->N));
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46
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47 /* outlen must be at least the size of the modulus */
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48 modulus_bytelen = mp_unsigned_bin_size(&(key->N));
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49 if (modulus_bytelen != siglen) {
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50 return CRYPT_INVALID_PACKET;
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51 }
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52
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53 /* allocate temp buffer for decoded sig */
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54 tmpbuf = XMALLOC(siglen);
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55 if (tmpbuf == NULL) {
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56 return CRYPT_MEM;
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57 }
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58
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59 /* RSA decode it */
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60 x = siglen;
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61 if ((err = rsa_exptmod(sig, siglen, tmpbuf, &x, PK_PUBLIC, prng, prng_idx, key)) != CRYPT_OK) {
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62 XFREE(tmpbuf);
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63 return err;
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64 }
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65
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66 /* PSS decode it */
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67 err = pkcs_1_v15_sa_decode(msghash, msghashlen, tmpbuf, x, hash_idx, modulus_bitlen, stat);
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68 XFREE(tmpbuf);
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69 return err;
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70 }
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71
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72 #endif