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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 #ifdef MDSA |
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14 |
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15 int dsa_sign_hash(const unsigned char *in, unsigned long inlen, |
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16 unsigned char *out, unsigned long *outlen, |
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17 prng_state *prng, int wprng, dsa_key *key) |
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18 { |
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143
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19 mp_int k, kinv, tmp, r, s; |
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20 unsigned char *buf; |
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21 int err, y; |
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22 unsigned long len; |
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23 |
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24 _ARGCHK(in != NULL); |
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25 _ARGCHK(out != NULL); |
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26 _ARGCHK(outlen != NULL); |
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27 _ARGCHK(key != NULL); |
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28 |
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29 if ((err = prng_is_valid(wprng)) != CRYPT_OK) { |
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30 return err; |
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31 } |
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32 if (key->type != PK_PRIVATE) { |
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33 return CRYPT_PK_NOT_PRIVATE; |
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34 } |
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35 |
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36 /* check group order size */ |
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143
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37 if (key->qord >= MDSA_MAX_GROUP) { |
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38 return CRYPT_INVALID_ARG; |
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39 } |
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40 |
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143
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41 buf = XMALLOC(MDSA_MAX_GROUP); |
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42 if (buf == NULL) { |
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43 return CRYPT_MEM; |
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44 } |
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45 |
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46 /* Init our temps */ |
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47 if ((err = mp_init_multi(&k, &kinv, &r, &s, &tmp, NULL)) != MP_OKAY) { goto error; } |
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48 |
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49 retry: |
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50 |
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51 do { |
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52 /* gen random k */ |
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53 if (prng_descriptor[wprng].read(buf, key->qord, prng) != (unsigned long)key->qord) { |
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54 err = CRYPT_ERROR_READPRNG; |
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143
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55 goto __ERR; |
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56 } |
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57 |
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58 /* read k */ |
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59 if ((err = mp_read_unsigned_bin(&k, buf, key->qord)) != MP_OKAY) { goto error; } |
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60 |
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61 /* k > 1 ? */ |
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62 if (mp_cmp_d(&k, 1) != MP_GT) { goto retry; } |
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63 |
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64 /* test gcd */ |
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65 if ((err = mp_gcd(&k, &key->q, &tmp)) != MP_OKAY) { goto error; } |
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66 } while (mp_cmp_d(&tmp, 1) != MP_EQ); |
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67 |
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68 /* now find 1/k mod q */ |
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69 if ((err = mp_invmod(&k, &key->q, &kinv)) != MP_OKAY) { goto error; } |
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70 |
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71 /* now find r = g^k mod p mod q */ |
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72 if ((err = mp_exptmod(&key->g, &k, &key->p, &r)) != MP_OKAY) { goto error; } |
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73 if ((err = mp_mod(&r, &key->q, &r)) != MP_OKAY) { goto error; } |
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74 |
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75 if (mp_iszero(&r) == MP_YES) { goto retry; } |
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76 |
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77 /* now find s = (in + xr)/k mod q */ |
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78 if ((err = mp_read_unsigned_bin(&tmp, (unsigned char *)in, inlen)) != MP_OKAY) { goto error; } |
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79 if ((err = mp_mul(&key->x, &r, &s)) != MP_OKAY) { goto error; } |
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80 if ((err = mp_add(&s, &tmp, &s)) != MP_OKAY) { goto error; } |
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81 if ((err = mp_mulmod(&s, &kinv, &key->q, &s)) != MP_OKAY) { goto error; } |
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82 |
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83 if (mp_iszero(&s) == MP_YES) { goto retry; } |
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84 |
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85 /* now store em both */ |
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86 |
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87 /* first check that we have enough room */ |
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88 if (*outlen < (unsigned long)(PACKET_SIZE + 4 + mp_unsigned_bin_size(&s) + mp_unsigned_bin_size(&r))) { |
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89 err = CRYPT_BUFFER_OVERFLOW; |
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143
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90 goto __ERR; |
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91 } |
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92 |
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93 /* packet header */ |
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94 packet_store_header(out, PACKET_SECT_DSA, PACKET_SUB_SIGNED); |
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95 y = PACKET_SIZE; |
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96 |
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97 /* store length of r */ |
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98 len = mp_unsigned_bin_size(&r); |
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99 out[y++] = (len>>8)&255; |
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100 out[y++] = len&255; |
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101 |
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102 /* store r */ |
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103 if ((err = mp_to_unsigned_bin(&r, out+y)) != MP_OKAY) { goto error; } |
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104 y += len; |
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105 |
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106 /* store length of s */ |
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107 len = mp_unsigned_bin_size(&s); |
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108 out[y++] = (len>>8)&255; |
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109 out[y++] = len&255; |
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110 |
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111 /* store s */ |
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112 if ((err = mp_to_unsigned_bin(&s, out+y)) != MP_OKAY) { goto error; } |
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113 y += len; |
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114 |
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115 /* reset size */ |
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116 *outlen = y; |
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117 |
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118 err = CRYPT_OK; |
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119 goto __ERR; |
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120 |
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143
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121 error: |
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122 err = mpi_to_ltc_error(err); |
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123 __ERR: |
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124 mp_clear_multi(&k, &kinv, &r, &s, &tmp, NULL); |
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125 #ifdef CLEAN_STACK |
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126 zeromem(buf, MDSA_MAX_GROUP); |
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127 #endif |
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128 XFREE(buf); |
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129 return err; |
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130 } |
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131 |
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132 #endif |
