Bug Summary

File:lib/nettle/ecc_verify_hash.c
Location:line 67, column 8
Description:Although the value stored to 'err' is used in the enclosing expression, the value is never actually read from 'err'

Annotated Source Code

1/*
2 * Copyright (C) 2011-2012 Free Software Foundation, Inc.
3 *
4 * This file is part of GNUTLS.
5 *
6 * The GNUTLS library is free software; you can redistribute it and/or
7 * modify it under the terms of the GNU Lesser General Public License
8 * as published by the Free Software Foundation; either version 3 of
9 * the License, or (at your option) any later version.
10 *
11 * This library is distributed in the hope that it will be useful, but
12 * WITHOUT ANY WARRANTY; without even the implied warranty of
13 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
14 * Lesser General Public License for more details.
15 *
16 * You should have received a copy of the GNU Lesser General Public License
17 * along with this program. If not, see <http://www.gnu.org/licenses/>
18 *
19 */
20
21/* Based on public domain code of LibTomCrypt by Tom St Denis.
22 * Adapted to gmp and nettle by Nikos Mavrogiannopoulos.
23 */
24
25#include "ecc.h"
26
27/*
28 @file ecc_verify_hash.c
29 ECC Crypto, Tom St Denis
30*/
31
32/* verify
33 *
34 * w = s^-1 mod n
35 * u1 = xw
36 * u2 = rw
37 * X = u1*G + u2*Q
38 * v = X_x1 mod n
39 * accept if v == r
40 */
41
42/*
43 Verify an ECC signature
44 @param signature The signature to verify
45 @param hash The hash (message digest) that was signed
46 @param hashlen The length of the hash (octets)
47 @param stat Result of signature, 1==valid, 0==invalid
48 @param key The corresponding public ECC key
49 @return 0 if successful (even if the signature is not valid)
50*/
51int
52ecc_verify_hash (struct dsa_signature *signature,
53 const unsigned char *hash, unsigned long hashlen,
54 int *stat, ecc_key * key)
55{
56 ecc_point *mG, *mQ;
57 mpz_t v, w, u1, u2, e;
58 int err;
59
60 if (signature == NULL((void*)0) || hash == NULL((void*)0) || stat == NULL((void*)0) || key == NULL((void*)0))
61 return -1;
62
63 /* default to invalid signature */
64 *stat = 0;
65
66 /* allocate ints */
67 if ((err = mp_init_multi (&v, &w, &u1, &u2, &e, NULL((void*)0))) != 0)
Although the value stored to 'err' is used in the enclosing expression, the value is never actually read from 'err'
68 {
69 return -1;
70 }
71
72 /* allocate points */
73 mG = ecc_new_point ();
74 mQ = ecc_new_point ();
75 if (mQ == NULL((void*)0) || mG == NULL((void*)0))
76 {
77 err = -1;
78 goto error;
79 }
80
81 /* check for (0) */
82 if (mpz_cmp_ui (signature->r, 0)(__builtin_constant_p (0) && (0) == 0 ? ((signature->
r)->_mp_size < 0 ? -1 : (signature->r)->_mp_size >
0) : __gmpz_cmp_ui (signature->r,0)) == 0 || mpz_cmp_ui (signature->s, 0)(__builtin_constant_p (0) && (0) == 0 ? ((signature->
s)->_mp_size < 0 ? -1 : (signature->s)->_mp_size >
0) : __gmpz_cmp_ui (signature->s,0)) == 0
83 || mpz_cmp__gmpz_cmp (signature->r, key->order) >= 0
84 || mpz_cmp__gmpz_cmp (signature->s, key->order) >= 0)
85 {
86 err = -1;
87 goto error;
88 }
89
90 /* read hash */
91 nettle_mpz_set_str_256_u (e, hashlen, hash);
92
93 /* w = s^-1 mod n */
94 mpz_invert__gmpz_invert (w, signature->s, key->order);
95
96 /* u1 = ew */
97 mpz_mul__gmpz_mul (u1, e, w);
98 mpz_mod__gmpz_mod (u1, u1, key->order);
99
100 /* u2 = rw */
101 mpz_mul__gmpz_mul (u2, signature->r, w);
102 mpz_mod__gmpz_mod (u2, u2, key->order);
103
104 /* find mG and mQ */
105 mpz_set__gmpz_set (mG->x, key->Gx);
106 mpz_set__gmpz_set (mG->y, key->Gy);
107 mpz_set_ui__gmpz_set_ui (mG->z, 1);
108
109 mpz_set__gmpz_set (mQ->x, key->pubkey.x);
110 mpz_set__gmpz_set (mQ->y, key->pubkey.y);
111 mpz_set__gmpz_set (mQ->z, key->pubkey.z);
112
113 /* compute u1*mG + u2*mQ = mG */
114 if ((err = ecc_mulmod (u1, mG, mG, key->A, key->prime, 0)) != 0)
115 {
116 goto error;
117 }
118 if ((err = ecc_mulmod (u2, mQ, mQ, key->A, key->prime, 0)) != 0)
119 {
120 goto error;
121 }
122
123 /* add them */
124 if ((err =
125 ecc_projective_add_point (mQ, mG, mG, key->A, key->prime)) != 0)
126 {
127 goto error;
128 }
129
130 /* reduce */
131 if ((err = ecc_map (mG, key->prime)) != 0)
132 {
133 goto error;
134 }
135
136 /* v = X_x1 mod n */
137 mpz_mod__gmpz_mod (v, mG->x, key->order);
138
139 /* does v == r */
140 if (mpz_cmp__gmpz_cmp (v, signature->r) == 0)
141 {
142 *stat = 1;
143 }
144
145 /* clear up and return */
146 err = 0;
147error:
148 ecc_del_point (mG);
149 ecc_del_point (mQ);
150 mp_clear_multi (&v, &w, &u1, &u2, &e, NULL((void*)0));
151 return err;
152}
153
154/* $Source: /webcvs/gnutls/gnutls/clang/report-1ds23z.html,v $ */
155/* $Revision: 1.1 $ */
156/* $Date: 2012/01/20 14:01:16 $ */