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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 |
