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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 #include "mycrypt.h" |
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12 |
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13 /* PKCS #1 v1.5 Signature Padding -- Tom St Denis */ |
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14 |
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15 #ifdef PKCS_1 |
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16 |
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17 int pkcs_1_v15_sa_encode(const unsigned char *msghash, unsigned long msghashlen, |
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18 int hash_idx, unsigned long modulus_bitlen, |
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19 unsigned char *out, unsigned long *outlen) |
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20 { |
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21 unsigned long derlen, modulus_bytelen, x, y; |
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22 int err; |
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23 |
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24 _ARGCHK(msghash != NULL) |
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25 _ARGCHK(out != NULL); |
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26 _ARGCHK(outlen != NULL); |
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27 |
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28 if ((err = hash_is_valid(hash_idx)) != CRYPT_OK) { |
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29 return err; |
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30 } |
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31 |
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32 /* hack, to detect any hash without a DER OID */ |
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33 if (hash_descriptor[hash_idx].DERlen == 0) { |
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34 return CRYPT_INVALID_ARG; |
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35 } |
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36 |
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37 /* get modulus len */ |
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38 modulus_bytelen = (modulus_bitlen>>3) + (modulus_bitlen & 7 ? 1 : 0); |
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39 |
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40 /* get der len ok? Forgive my lame German accent.... */ |
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41 derlen = hash_descriptor[hash_idx].DERlen; |
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42 |
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43 /* valid sizes? */ |
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44 if (msghashlen + 3 + derlen > modulus_bytelen) { |
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45 return CRYPT_PK_INVALID_SIZE; |
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46 } |
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47 |
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48 if (*outlen < modulus_bytelen) { |
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49 return CRYPT_BUFFER_OVERFLOW; |
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50 } |
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51 |
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52 /* packet is 0x00 0x01 PS 0x00 T, where PS == 0xFF repeated modulus_bytelen - 3 - derlen - msghashlen times, T == DER || hash */ |
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53 x = 0; |
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54 out[x++] = 0x00; |
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55 out[x++] = 0x01; |
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56 for (y = 0; y < (modulus_bytelen - 3 - derlen - msghashlen); y++) { |
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57 out[x++] = 0xFF; |
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58 } |
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59 out[x++] = 0x00; |
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60 for (y = 0; y < derlen; y++) { |
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61 out[x++] = hash_descriptor[hash_idx].DER[y]; |
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62 } |
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63 for (y = 0; y < msghashlen; y++) { |
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64 out[x++] = msghash[y]; |
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65 } |
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66 |
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67 *outlen = modulus_bytelen; |
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68 return CRYPT_OK; |
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69 } |
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70 |
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71 #endif /* PKCS_1 */ |
