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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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19 mp_int k, kinv, tmp, r, s; |
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20 unsigned char buf[512]; |
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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 |
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25 _ARGCHK(in != NULL); |
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26 _ARGCHK(out != NULL); |
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27 _ARGCHK(outlen != NULL); |
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28 _ARGCHK(key != NULL); |
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29 |
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30 if ((err = prng_is_valid(wprng)) != CRYPT_OK) { |
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31 return err; |
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32 } |
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33 if (key->type != PK_PRIVATE) { |
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34 return CRYPT_PK_NOT_PRIVATE; |
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35 } |
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36 |
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37 /* check group order size */ |
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38 if (key->qord >= (int)sizeof(buf)) { |
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39 return CRYPT_INVALID_ARG; |
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40 } |
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41 |
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42 /* Init our temps */ |
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43 if ((err = mp_init_multi(&k, &kinv, &r, &s, &tmp, NULL)) != MP_OKAY) { goto error; } |
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44 |
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45 retry: |
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46 |
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47 do { |
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48 /* gen random k */ |
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49 if (prng_descriptor[wprng].read(buf, key->qord, prng) != (unsigned long)key->qord) { |
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50 err = CRYPT_ERROR_READPRNG; |
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51 goto done; |
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52 } |
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53 |
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54 /* read k */ |
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55 if ((err = mp_read_unsigned_bin(&k, buf, key->qord)) != MP_OKAY) { goto error; } |
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56 |
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57 /* k > 1 ? */ |
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58 if (mp_cmp_d(&k, 1) != MP_GT) { goto retry; } |
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59 |
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60 /* test gcd */ |
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61 if ((err = mp_gcd(&k, &key->q, &tmp)) != MP_OKAY) { goto error; } |
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62 } while (mp_cmp_d(&tmp, 1) != MP_EQ); |
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63 |
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64 /* now find 1/k mod q */ |
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65 if ((err = mp_invmod(&k, &key->q, &kinv)) != MP_OKAY) { goto error; } |
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66 |
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67 /* now find r = g^k mod p mod q */ |
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68 if ((err = mp_exptmod(&key->g, &k, &key->p, &r)) != MP_OKAY) { goto error; } |
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69 if ((err = mp_mod(&r, &key->q, &r)) != MP_OKAY) { goto error; } |
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70 |
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71 if (mp_iszero(&r) == MP_YES) { goto retry; } |
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72 |
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73 /* now find s = (in + xr)/k mod q */ |
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74 if ((err = mp_read_unsigned_bin(&tmp, (unsigned char *)in, inlen)) != MP_OKAY) { goto error; } |
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75 if ((err = mp_mul(&key->x, &r, &s)) != MP_OKAY) { goto error; } |
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76 if ((err = mp_add(&s, &tmp, &s)) != MP_OKAY) { goto error; } |
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77 if ((err = mp_mulmod(&s, &kinv, &key->q, &s)) != MP_OKAY) { goto error; } |
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78 |
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79 if (mp_iszero(&s) == MP_YES) { goto retry; } |
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80 |
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81 /* now store em both */ |
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82 |
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83 /* first check that we have enough room */ |
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84 if (*outlen < (unsigned long)(PACKET_SIZE + 4 + mp_unsigned_bin_size(&s) + mp_unsigned_bin_size(&r))) { |
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85 err = CRYPT_BUFFER_OVERFLOW; |
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86 goto done; |
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87 } |
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88 |
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89 /* packet header */ |
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90 packet_store_header(out, PACKET_SECT_DSA, PACKET_SUB_SIGNED); |
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91 y = PACKET_SIZE; |
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92 |
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93 /* store length of r */ |
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94 len = mp_unsigned_bin_size(&r); |
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95 out[y++] = (len>>8)&255; |
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96 out[y++] = len&255; |
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97 |
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98 /* store r */ |
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99 if ((err = mp_to_unsigned_bin(&r, out+y)) != MP_OKAY) { goto error; } |
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100 y += len; |
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101 |
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102 /* store length of s */ |
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103 len = mp_unsigned_bin_size(&s); |
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104 out[y++] = (len>>8)&255; |
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105 out[y++] = len&255; |
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106 |
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107 /* store s */ |
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108 if ((err = mp_to_unsigned_bin(&s, out+y)) != MP_OKAY) { goto error; } |
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109 y += len; |
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110 |
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111 /* reset size */ |
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112 *outlen = y; |
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113 |
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114 err = CRYPT_OK; |
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115 goto done; |
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116 |
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117 error : err = mpi_to_ltc_error(err); |
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118 done : mp_clear_multi(&k, &kinv, &r, &s, &tmp, NULL); |
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119 #ifdef CLEAN_STACK |
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120 zeromem(buf, sizeof(buf)); |
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121 #endif |
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122 return err; |
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123 } |
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124 |
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125 #endif |
