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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 /* Submited by Dobes Vandermeer ([email protected]) */ |
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12 |
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13 #include "mycrypt.h" |
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14 |
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15 /* |
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16 (1) append zeros to the end of K to create a B byte string |
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17 (e.g., if K is of length 20 bytes and B=64, then K will be |
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18 appended with 44 zero bytes 0x00) |
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19 (2) XOR (bitwise exclusive-OR) the B byte string computed in step |
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20 (1) with ipad (ipad = the byte 0x36 repeated B times) |
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21 (3) append the stream of data 'text' to the B byte string resulting |
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22 from step (2) |
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23 (4) apply H to the stream generated in step (3) |
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24 (5) XOR (bitwise exclusive-OR) the B byte string computed in |
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25 step (1) with opad (opad = the byte 0x5C repeated B times.) |
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26 (6) append the H result from step (4) to the B byte string |
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27 resulting from step (5) |
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28 (7) apply H to the stream generated in step (6) and output |
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29 the result |
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30 */ |
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31 |
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32 #ifdef HMAC |
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33 |
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34 #define HMAC_BLOCKSIZE hash_descriptor[hash].blocksize |
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35 |
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36 int hmac_init(hmac_state *hmac, int hash, const unsigned char *key, unsigned long keylen) |
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37 { |
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143
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38 unsigned char *buf; |
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39 unsigned long hashsize; |
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40 unsigned long i, z; |
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41 int err; |
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42 |
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43 _ARGCHK(hmac != NULL); |
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143
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44 _ARGCHK(key != NULL); |
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45 |
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143
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46 /* valid hash? */ |
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47 if ((err = hash_is_valid(hash)) != CRYPT_OK) { |
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48 return err; |
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49 } |
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143
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50 hmac->hash = hash; |
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51 hashsize = hash_descriptor[hash].hashsize; |
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52 |
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53 /* valid key length? */ |
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54 if (keylen == 0) { |
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55 return CRYPT_INVALID_KEYSIZE; |
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56 } |
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57 |
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143
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58 /* allocate ram for buf */ |
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59 buf = XMALLOC(HMAC_BLOCKSIZE); |
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60 if (buf == NULL) { |
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61 return CRYPT_MEM; |
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62 } |
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63 |
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143
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64 /* allocate memory for key */ |
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65 hmac->key = XMALLOC(HMAC_BLOCKSIZE); |
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66 if (hmac->key == NULL) { |
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67 XFREE(buf); |
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68 return CRYPT_MEM; |
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69 } |
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70 |
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71 /* (1) make sure we have a large enough key */ |
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72 if(keylen > HMAC_BLOCKSIZE) { |
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143
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73 z = HMAC_BLOCKSIZE; |
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74 if ((err = hash_memory(hash, key, keylen, hmac->key, &z)) != CRYPT_OK) { |
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75 goto __ERR; |
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76 } |
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77 if(hashsize < HMAC_BLOCKSIZE) { |
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78 zeromem((hmac->key) + hashsize, (size_t)(HMAC_BLOCKSIZE - hashsize)); |
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79 } |
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80 keylen = hashsize; |
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81 } else { |
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143
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82 XMEMCPY(hmac->key, key, (size_t)keylen); |
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83 if(keylen < HMAC_BLOCKSIZE) { |
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84 zeromem((hmac->key) + keylen, (size_t)(HMAC_BLOCKSIZE - keylen)); |
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85 } |
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86 } |
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87 |
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143
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88 /* Create the initial vector for step (3) */ |
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89 for(i=0; i < HMAC_BLOCKSIZE; i++) { |
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90 buf[i] = hmac->key[i] ^ 0x36; |
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91 } |
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92 |
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143
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93 /* Pre-pend that to the hash data */ |
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94 if ((err = hash_descriptor[hash].init(&hmac->md)) != CRYPT_OK) { |
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95 goto __ERR; |
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96 } |
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97 |
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143
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98 if ((err = hash_descriptor[hash].process(&hmac->md, buf, HMAC_BLOCKSIZE)) != CRYPT_OK) { |
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99 goto __ERR; |
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100 } |
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101 goto done; |
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102 __ERR: |
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103 /* free the key since we failed */ |
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104 XFREE(hmac->key); |
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105 done: |
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106 #ifdef CLEAN_STACK |
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107 zeromem(buf, HMAC_BLOCKSIZE); |
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108 #endif |
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109 |
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110 XFREE(buf); |
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111 return err; |
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112 } |
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113 |
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114 #endif |
