Mercurial > dropbear
annotate src/pk/dsa/dsa_verify_hash.c @ 209:39d5d58461d6 libtomcrypt-orig LTC_1.05
Import of libtomcrypt 1.05
| author | Matt Johnston <matt@ucc.asn.au> |
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| date | Wed, 06 Jul 2005 03:53:40 +0000 |
| parents | 1c15b283127b |
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| rev | line source |
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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 "tomcrypt.h" |
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12 |
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13 /** |
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14 @file dsa_verify_hash.c |
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15 DSA implementation, verify a signature, Tom St Denis |
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16 */ |
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17 |
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18 |
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19 #ifdef MDSA |
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20 |
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21 /** |
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22 Verify a DSA signature |
| 209 | 23 @param r DSA "r" parameter |
| 24 @param s DSA "s" parameter | |
| 25 @param hash The hash that was signed | |
| 26 @param hashlen The length of the hash that was signed | |
| 27 @param stat [out] The result of the signature verification, 1==valid, 0==invalid | |
| 28 @param key The corresponding public DH key | |
| 29 @return CRYPT_OK if successful (even if the signature is invalid) | |
| 30 */ | |
| 31 int dsa_verify_hash_raw( mp_int *r, mp_int *s, | |
| 32 const unsigned char *hash, unsigned long hashlen, | |
| 33 int *stat, dsa_key *key) | |
| 34 { | |
| 35 mp_int w, v, u1, u2; | |
| 36 int err; | |
| 37 | |
| 38 LTC_ARGCHK(r != NULL); | |
| 39 LTC_ARGCHK(s != NULL); | |
| 40 LTC_ARGCHK(stat != NULL); | |
| 41 LTC_ARGCHK(key != NULL); | |
| 42 | |
| 43 /* default to invalid signature */ | |
| 44 *stat = 0; | |
| 45 | |
| 46 /* init our variables */ | |
| 47 if ((err = mp_init_multi(&w, &v, &u1, &u2, NULL)) != MP_OKAY) { | |
| 48 return mpi_to_ltc_error(err); | |
| 49 } | |
| 50 | |
| 51 /* neither r or s can be null or >q*/ | |
| 52 if (mp_iszero(r) == MP_YES || mp_iszero(s) == MP_YES || mp_cmp(r, &key->q) != MP_LT || mp_cmp(s, &key->q) != MP_LT) { | |
| 53 err = CRYPT_INVALID_PACKET; | |
| 54 goto done; | |
| 55 } | |
| 56 | |
| 57 /* w = 1/s mod q */ | |
| 58 if ((err = mp_invmod(s, &key->q, &w)) != MP_OKAY) { goto error; } | |
| 59 | |
| 60 /* u1 = m * w mod q */ | |
| 61 if ((err = mp_read_unsigned_bin(&u1, (unsigned char *)hash, hashlen)) != MP_OKAY) { goto error; } | |
| 62 if ((err = mp_mulmod(&u1, &w, &key->q, &u1)) != MP_OKAY) { goto error; } | |
| 63 | |
| 64 /* u2 = r*w mod q */ | |
| 65 if ((err = mp_mulmod(r, &w, &key->q, &u2)) != MP_OKAY) { goto error; } | |
| 66 | |
| 67 /* v = g^u1 * y^u2 mod p mod q */ | |
| 68 if ((err = mp_exptmod(&key->g, &u1, &key->p, &u1)) != MP_OKAY) { goto error; } | |
| 69 if ((err = mp_exptmod(&key->y, &u2, &key->p, &u2)) != MP_OKAY) { goto error; } | |
| 70 if ((err = mp_mulmod(&u1, &u2, &key->p, &v)) != MP_OKAY) { goto error; } | |
| 71 if ((err = mp_mod(&v, &key->q, &v)) != MP_OKAY) { goto error; } | |
| 72 | |
| 73 /* if r = v then we're set */ | |
| 74 if (mp_cmp(r, &v) == MP_EQ) { | |
| 75 *stat = 1; | |
| 76 } | |
| 77 | |
| 78 err = CRYPT_OK; | |
| 79 goto done; | |
| 80 | |
| 81 error : err = mpi_to_ltc_error(err); | |
| 82 done : mp_clear_multi(&w, &v, &u1, &u2, NULL); | |
| 83 return err; | |
| 84 } | |
| 85 | |
| 86 /** | |
| 87 Verify a DSA signature | |
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88 @param sig The signature |
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89 @param siglen The length of the signature (octets) |
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90 @param hash The hash that was signed |
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91 @param hashlen The length of the hash that was signed |
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92 @param stat [out] The result of the signature verification, 1==valid, 0==invalid |
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93 @param key The corresponding public DH key |
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94 @return CRYPT_OK if successful (even if the signature is invalid) |
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95 */ |
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96 int dsa_verify_hash(const unsigned char *sig, unsigned long siglen, |
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97 const unsigned char *hash, unsigned long hashlen, |
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98 int *stat, dsa_key *key) |
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99 { |
| 209 | 100 int err; |
| 101 mp_int r, s; | |
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102 |
| 209 | 103 if ((err = mp_init_multi(&r, &s, NULL)) != CRYPT_OK) { |
| 104 return CRYPT_MEM; | |
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105 } |
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106 |
| 209 | 107 /* decode the sequence */ |
| 108 if ((err = der_decode_sequence_multi(sig, siglen, | |
| 109 LTC_ASN1_INTEGER, 1UL, &r, | |
| 110 LTC_ASN1_INTEGER, 1UL, &s, | |
| 111 LTC_ASN1_EOL, 0UL, NULL)) != CRYPT_OK) { | |
| 112 goto LBL_ERR; | |
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113 } |
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114 |
| 209 | 115 /* do the op */ |
| 116 err = dsa_verify_hash_raw(&r, &s, hash, hashlen, stat, key); | |
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117 |
| 209 | 118 LBL_ERR: |
| 119 mp_clear_multi(&r, &s, NULL); | |
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120 return err; |
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121 } |
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122 |
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123 #endif |
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124 |
| 209 | 125 |
| 126 /* $Source: /cvs/libtom/libtomcrypt/src/pk/dsa/dsa_verify_hash.c,v $ */ | |
| 127 /* $Revision: 1.8 $ */ | |
| 128 /* $Date: 2005/05/15 21:48:59 $ */ |