1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
|
/*
* Copyright 1995-2016 The OpenSSL Project Authors. All Rights Reserved.
*
* Licensed under the OpenSSL license (the "License"). You may not use
* this file except in compliance with the License. You can obtain a copy
* in the file LICENSE in the source distribution or at
* https://www.openssl.org/source/license.html
*/
/* Original version from Steven Schoch <schoch@sheba.arc.nasa.gov> */
#include <stdio.h>
#include "internal/cryptlib.h"
#include <openssl/bn.h>
#include <openssl/sha.h>
#include "dsa_locl.h"
#include <openssl/asn1.h>
static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa);
static int dsa_sign_setup_no_digest(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
BIGNUM **rp);
static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in, BIGNUM **kinvp,
BIGNUM **rp, const unsigned char *dgst, int dlen);
static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
DSA_SIG *sig, DSA *dsa);
static int dsa_init(DSA *dsa);
static int dsa_finish(DSA *dsa);
static DSA_METHOD openssl_dsa_meth = {
"OpenSSL DSA method",
dsa_do_sign,
dsa_sign_setup_no_digest,
dsa_do_verify,
NULL, /* dsa_mod_exp, */
NULL, /* dsa_bn_mod_exp, */
dsa_init,
dsa_finish,
DSA_FLAG_FIPS_METHOD,
NULL,
NULL,
NULL
};
const DSA_METHOD *DSA_OpenSSL(void)
{
return &openssl_dsa_meth;
}
static DSA_SIG *dsa_do_sign(const unsigned char *dgst, int dlen, DSA *dsa)
{
BIGNUM *kinv = NULL;
BIGNUM *m;
BIGNUM *xr;
BIGNUM *r, *s;
BN_CTX *ctx = NULL;
int reason = ERR_R_BN_LIB;
DSA_SIG *ret = NULL;
int rv = 0;
m = BN_new();
xr = BN_new();
if (m == NULL || xr == NULL)
goto err;
if (!dsa->p || !dsa->q || !dsa->g) {
reason = DSA_R_MISSING_PARAMETERS;
goto err;
}
ret = DSA_SIG_new();
if (ret == NULL)
goto err;
DSA_SIG_get0(&r, &s, ret);
ctx = BN_CTX_new();
if (ctx == NULL)
goto err;
redo:
if (!dsa_sign_setup(dsa, ctx, &kinv, &r, dgst, dlen))
goto err;
if (dlen > BN_num_bytes(dsa->q))
/*
* if the digest length is greater than the size of q use the
* BN_num_bits(dsa->q) leftmost bits of the digest, see fips 186-3,
* 4.2
*/
dlen = BN_num_bytes(dsa->q);
if (BN_bin2bn(dgst, dlen, m) == NULL)
goto err;
/* Compute s = inv(k) (m + xr) mod q */
if (!BN_mod_mul(xr, dsa->priv_key, r, dsa->q, ctx))
goto err; /* s = xr */
if (!BN_add(s, xr, m))
goto err; /* s = m + xr */
if (BN_cmp(s, dsa->q) > 0)
if (!BN_sub(s, s, dsa->q))
goto err;
if (!BN_mod_mul(s, s, kinv, dsa->q, ctx))
goto err;
/*
* Redo if r or s is zero as required by FIPS 186-3: this is very
* unlikely.
*/
if (BN_is_zero(r) || BN_is_zero(s))
goto redo;
rv = 1;
err:
if (rv == 0) {
DSAerr(DSA_F_DSA_DO_SIGN, reason);
DSA_SIG_free(ret);
ret = NULL;
}
BN_CTX_free(ctx);
BN_clear_free(m);
BN_clear_free(xr);
BN_clear_free(kinv);
return ret;
}
static int dsa_sign_setup_no_digest(DSA *dsa, BN_CTX *ctx_in,
BIGNUM **kinvp, BIGNUM **rp)
{
return dsa_sign_setup(dsa, ctx_in, kinvp, rp, NULL, 0);
}
static int dsa_sign_setup(DSA *dsa, BN_CTX *ctx_in,
BIGNUM **kinvp, BIGNUM **rp,
const unsigned char *dgst, int dlen)
{
BN_CTX *ctx = NULL;
BIGNUM *k, *kinv = NULL, *r = *rp;
int ret = 0;
if (!dsa->p || !dsa->q || !dsa->g) {
DSAerr(DSA_F_DSA_SIGN_SETUP, DSA_R_MISSING_PARAMETERS);
return 0;
}
k = BN_new();
if (k == NULL)
goto err;
if (ctx_in == NULL) {
if ((ctx = BN_CTX_new()) == NULL)
goto err;
} else
ctx = ctx_in;
/* Get random k */
do {
if (dgst != NULL) {
/*
* We calculate k from SHA512(private_key + H(message) + random).
* This protects the private key from a weak PRNG.
*/
if (!BN_generate_dsa_nonce(k, dsa->q, dsa->priv_key, dgst,
dlen, ctx))
goto err;
} else if (!BN_rand_range(k, dsa->q))
goto err;
} while (BN_is_zero(k));
BN_set_flags(k, BN_FLG_CONSTTIME);
if (dsa->flags & DSA_FLAG_CACHE_MONT_P) {
if (!BN_MONT_CTX_set_locked(&dsa->method_mont_p,
dsa->lock, dsa->p, ctx))
goto err;
}
/* Compute r = (g^k mod p) mod q */
/*
* We do not want timing information to leak the length of k, so we
* compute g^k using an equivalent exponent of fixed length. (This
* is a kludge that we need because the BN_mod_exp_mont() does not
* let us specify the desired timing behaviour.)
*/
if (!BN_add(k, k, dsa->q))
goto err;
if (BN_num_bits(k) <= BN_num_bits(dsa->q)) {
if (!BN_add(k, k, dsa->q))
goto err;
}
if ((dsa)->meth->bn_mod_exp != NULL) {
if (!dsa->meth->bn_mod_exp(dsa, r, dsa->g, k, dsa->p, ctx,
dsa->method_mont_p))
goto err;
} else {
if (!BN_mod_exp_mont(r, dsa->g, k, dsa->p, ctx, dsa->method_mont_p))
goto err;
}
if (!BN_mod(r, r, dsa->q, ctx))
goto err;
/* Compute part of 's = inv(k) (m + xr) mod q' */
if ((kinv = BN_mod_inverse(NULL, k, dsa->q, ctx)) == NULL)
goto err;
BN_clear_free(*kinvp);
*kinvp = kinv;
kinv = NULL;
ret = 1;
err:
if (!ret)
DSAerr(DSA_F_DSA_SIGN_SETUP, ERR_R_BN_LIB);
if (ctx != ctx_in)
BN_CTX_free(ctx);
BN_clear_free(k);
return ret;
}
static int dsa_do_verify(const unsigned char *dgst, int dgst_len,
DSA_SIG *sig, DSA *dsa)
{
BN_CTX *ctx;
BIGNUM *u1, *u2, *t1;
BN_MONT_CTX *mont = NULL;
BIGNUM *r, *s;
int ret = -1, i;
if (!dsa->p || !dsa->q || !dsa->g) {
DSAerr(DSA_F_DSA_DO_VERIFY, DSA_R_MISSING_PARAMETERS);
return -1;
}
i = BN_num_bits(dsa->q
|