1/*
2 * Copyright 2002-2019 The OpenSSL Project Authors. All Rights Reserved.
3 *
4 * Licensed under the OpenSSL license (the "License").  You may not use
5 * this file except in compliance with the License.  You can obtain a copy
6 * in the file LICENSE in the source distribution or at
7 * https://www.openssl.org/source/license.html
8 */
9
10#include <string.h>
11#include <openssl/err.h>
12#include <openssl/obj_mac.h>
13#include <openssl/rand.h>
14#include "crypto/bn.h"
15#include "ec_local.h"
16
17int ossl_ecdsa_sign(int type, const unsigned char *dgst, int dlen,
18                    unsigned char *sig, unsigned int *siglen,
19                    const BIGNUM *kinv, const BIGNUM *r, EC_KEY *eckey)
20{
21    ECDSA_SIG *s;
22
23    s = ECDSA_do_sign_ex(dgst, dlen, kinv, r, eckey);
24    if (s == NULL) {
25        *siglen = 0;
26        return 0;
27    }
28    *siglen = i2d_ECDSA_SIG(s, &sig);
29    ECDSA_SIG_free(s);
30    return 1;
31}
32
33static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
34                            BIGNUM **kinvp, BIGNUM **rp,
35                            const unsigned char *dgst, int dlen)
36{
37    BN_CTX *ctx = NULL;
38    BIGNUM *k = NULL, *r = NULL, *X = NULL;
39    const BIGNUM *order;
40    EC_POINT *tmp_point = NULL;
41    const EC_GROUP *group;
42    int ret = 0;
43    int order_bits;
44    const BIGNUM *priv_key;
45
46    if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
47        ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_PASSED_NULL_PARAMETER);
48        return 0;
49    }
50    if ((priv_key = EC_KEY_get0_private_key(eckey)) == NULL) {
51        ECerr(EC_F_ECDSA_SIGN_SETUP, EC_R_MISSING_PRIVATE_KEY);
52        return 0;
53    }
54
55    if (!EC_KEY_can_sign(eckey)) {
56        ECerr(EC_F_ECDSA_SIGN_SETUP, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
57        return 0;
58    }
59
60    if ((ctx = ctx_in) == NULL) {
61        if ((ctx = BN_CTX_new()) == NULL) {
62            ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
63            return 0;
64        }
65    }
66
67    k = BN_new();               /* this value is later returned in *kinvp */
68    r = BN_new();               /* this value is later returned in *rp */
69    X = BN_new();
70    if (k == NULL || r == NULL || X == NULL) {
71        ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_MALLOC_FAILURE);
72        goto err;
73    }
74    if ((tmp_point = EC_POINT_new(group)) == NULL) {
75        ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
76        goto err;
77    }
78    order = EC_GROUP_get0_order(group);
79
80    /* Preallocate space */
81    order_bits = BN_num_bits(order);
82    if (!BN_set_bit(k, order_bits)
83        || !BN_set_bit(r, order_bits)
84        || !BN_set_bit(X, order_bits))
85        goto err;
86
87    do {
88        /* get random k */
89        do {
90            if (dgst != NULL) {
91                if (!BN_generate_dsa_nonce(k, order, priv_key,
92                                           dgst, dlen, ctx)) {
93                    ECerr(EC_F_ECDSA_SIGN_SETUP,
94                          EC_R_RANDOM_NUMBER_GENERATION_FAILED);
95                    goto err;
96                }
97            } else {
98                if (!BN_priv_rand_range(k, order)) {
99                    ECerr(EC_F_ECDSA_SIGN_SETUP,
100                          EC_R_RANDOM_NUMBER_GENERATION_FAILED);
101                    goto err;
102                }
103            }
104        } while (BN_is_zero(k));
105
106        /* compute r the x-coordinate of generator * k */
107        if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
108            ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
109            goto err;
110        }
111
112        if (!EC_POINT_get_affine_coordinates(group, tmp_point, X, NULL, ctx)) {
113            ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_EC_LIB);
114            goto err;
115        }
116
117        if (!BN_nnmod(r, X, order, ctx)) {
118            ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
119            goto err;
120        }
121    } while (BN_is_zero(r));
122
123    /* compute the inverse of k */
124    if (!ec_group_do_inverse_ord(group, k, k, ctx)) {
125        ECerr(EC_F_ECDSA_SIGN_SETUP, ERR_R_BN_LIB);
126        goto err;
127    }
128
129    /* clear old values if necessary */
130    BN_clear_free(*rp);
131    BN_clear_free(*kinvp);
132    /* save the pre-computed values  */
133    *rp = r;
134    *kinvp = k;
135    ret = 1;
136 err:
137    if (!ret) {
138        BN_clear_free(k);
139        BN_clear_free(r);
140    }
141    if (ctx != ctx_in)
142        BN_CTX_free(ctx);
143    EC_POINT_free(tmp_point);
144    BN_clear_free(X);
145    return ret;
146}
147
148int ossl_ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
149                          BIGNUM **rp)
150{
151    return ecdsa_sign_setup(eckey, ctx_in, kinvp, rp, NULL, 0);
152}
153
154ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
155                               const BIGNUM *in_kinv, const BIGNUM *in_r,
156                               EC_KEY *eckey)
157{
158    int ok = 0, i;
159    BIGNUM *kinv = NULL, *s, *m = NULL;
160    const BIGNUM *order, *ckinv;
161    BN_CTX *ctx = NULL;
162    const EC_GROUP *group;
163    ECDSA_SIG *ret;
164    const BIGNUM *priv_key;
165
166    group = EC_KEY_get0_group(eckey);
167    priv_key = EC_KEY_get0_private_key(eckey);
168
169    if (group == NULL) {
170        ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_PASSED_NULL_PARAMETER);
171        return NULL;
172    }
173    if (priv_key == NULL) {
174        ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_MISSING_PRIVATE_KEY);
175        return NULL;
176    }
177
178    if (!EC_KEY_can_sign(eckey)) {
179        ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
180        return NULL;
181    }
182
183    ret = ECDSA_SIG_new();
184    if (ret == NULL) {
185        ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
186        return NULL;
187    }
188    ret->r = BN_new();
189    ret->s = BN_new();
190    if (ret->r == NULL || ret->s == NULL) {
191        ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
192        goto err;
193    }
194    s = ret->s;
195
196    if ((ctx = BN_CTX_new()) == NULL
197        || (m = BN_new()) == NULL) {
198        ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
199        goto err;
200    }
201
202    order = EC_GROUP_get0_order(group);
203    i = BN_num_bits(order);
204    /*
205     * Need to truncate digest if it is too long: first truncate whole bytes.
206     */
207    if (8 * dgst_len > i)
208        dgst_len = (i + 7) / 8;
209    if (!BN_bin2bn(dgst, dgst_len, m)) {
210        ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
211        goto err;
212    }
213    /* If still too long, truncate remaining bits with a shift */
214    if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
215        ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
216        goto err;
217    }
218    do {
219        if (in_kinv == NULL || in_r == NULL) {
220            if (!ecdsa_sign_setup(eckey, ctx, &kinv, &ret->r, dgst, dgst_len)) {
221                ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_ECDSA_LIB);
222                goto err;
223            }
224            ckinv = kinv;
225        } else {
226            ckinv = in_kinv;
227            if (BN_copy(ret->r, in_r) == NULL) {
228                ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_MALLOC_FAILURE);
229                goto err;
230            }
231        }
232
233        /*
234         * With only one multiplicant being in Montgomery domain
235         * multiplication yields real result without post-conversion.
236         * Also note that all operations but last are performed with
237         * zero-padded vectors. Last operation, BN_mod_mul_montgomery
238         * below, returns user-visible value with removed zero padding.
239         */
240        if (!bn_to_mont_fixed_top(s, ret->r, group->mont_data, ctx)
241            || !bn_mul_mont_fixed_top(s, s, priv_key, group->mont_data, ctx)) {
242            ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
243            goto err;
244        }
245        if (!bn_mod_add_fixed_top(s, s, m, order)) {
246            ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
247            goto err;
248        }
249        /*
250         * |s| can still be larger than modulus, because |m| can be. In
251         * such case we count on Montgomery reduction to tie it up.
252         */
253        if (!bn_to_mont_fixed_top(s, s, group->mont_data, ctx)
254            || !BN_mod_mul_montgomery(s, s, ckinv, group->mont_data, ctx)) {
255            ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, ERR_R_BN_LIB);
256            goto err;
257        }
258
259        if (BN_is_zero(s)) {
260            /*
261             * if kinv and r have been supplied by the caller, don't
262             * generate new kinv and r values
263             */
264            if (in_kinv != NULL && in_r != NULL) {
265                ECerr(EC_F_OSSL_ECDSA_SIGN_SIG, EC_R_NEED_NEW_SETUP_VALUES);
266                goto err;
267            }
268        } else {
269            /* s != 0 => we have a valid signature */
270            break;
271        }
272    } while (1);
273
274    ok = 1;
275 err:
276    if (!ok) {
277        ECDSA_SIG_free(ret);
278        ret = NULL;
279    }
280    BN_CTX_free(ctx);
281    BN_clear_free(m);
282    BN_clear_free(kinv);
283    return ret;
284}
285
286/*-
287 * returns
288 *      1: correct signature
289 *      0: incorrect signature
290 *     -1: error
291 */
292int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,
293                      const unsigned char *sigbuf, int sig_len, EC_KEY *eckey)
294{
295    ECDSA_SIG *s;
296    const unsigned char *p = sigbuf;
297    unsigned char *der = NULL;
298    int derlen = -1;
299    int ret = -1;
300
301    s = ECDSA_SIG_new();
302    if (s == NULL)
303        return ret;
304    if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
305        goto err;
306    /* Ensure signature uses DER and doesn't have trailing garbage */
307    derlen = i2d_ECDSA_SIG(s, &der);
308    if (derlen != sig_len || memcmp(sigbuf, der, derlen) != 0)
309        goto err;
310    ret = ECDSA_do_verify(dgst, dgst_len, s, eckey);
311 err:
312    OPENSSL_free(der);
313    ECDSA_SIG_free(s);
314    return ret;
315}
316
317int ossl_ecdsa_verify_sig(const unsigned char *dgst, int dgst_len,
318                          const ECDSA_SIG *sig, EC_KEY *eckey)
319{
320    int ret = -1, i;
321    BN_CTX *ctx;
322    const BIGNUM *order;
323    BIGNUM *u1, *u2, *m, *X;
324    EC_POINT *point = NULL;
325    const EC_GROUP *group;
326    const EC_POINT *pub_key;
327
328    /* check input values */
329    if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
330        (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
331        ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_MISSING_PARAMETERS);
332        return -1;
333    }
334
335    if (!EC_KEY_can_sign(eckey)) {
336        ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
337        return -1;
338    }
339
340    ctx = BN_CTX_new();
341    if (ctx == NULL) {
342        ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
343        return -1;
344    }
345    BN_CTX_start(ctx);
346    u1 = BN_CTX_get(ctx);
347    u2 = BN_CTX_get(ctx);
348    m = BN_CTX_get(ctx);
349    X = BN_CTX_get(ctx);
350    if (X == NULL) {
351        ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
352        goto err;
353    }
354
355    order = EC_GROUP_get0_order(group);
356    if (order == NULL) {
357        ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
358        goto err;
359    }
360
361    if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
362        BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
363        BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
364        ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, EC_R_BAD_SIGNATURE);
365        ret = 0;                /* signature is invalid */
366        goto err;
367    }
368    /* calculate tmp1 = inv(S) mod order */
369    if (!ec_group_do_inverse_ord(group, u2, sig->s, ctx)) {
370        ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
371        goto err;
372    }
373    /* digest -> m */
374    i = BN_num_bits(order);
375    /*
376     * Need to truncate digest if it is too long: first truncate whole bytes.
377     */
378    if (8 * dgst_len > i)
379        dgst_len = (i + 7) / 8;
380    if (!BN_bin2bn(dgst, dgst_len, m)) {
381        ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
382        goto err;
383    }
384    /* If still too long truncate remaining bits with a shift */
385    if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
386        ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
387        goto err;
388    }
389    /* u1 = m * tmp mod order */
390    if (!BN_mod_mul(u1, m, u2, order, ctx)) {
391        ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
392        goto err;
393    }
394    /* u2 = r * w mod q */
395    if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
396        ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
397        goto err;
398    }
399
400    if ((point = EC_POINT_new(group)) == NULL) {
401        ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_MALLOC_FAILURE);
402        goto err;
403    }
404    if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
405        ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
406        goto err;
407    }
408
409    if (!EC_POINT_get_affine_coordinates(group, point, X, NULL, ctx)) {
410        ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_EC_LIB);
411        goto err;
412    }
413
414    if (!BN_nnmod(u1, X, order, ctx)) {
415        ECerr(EC_F_OSSL_ECDSA_VERIFY_SIG, ERR_R_BN_LIB);
416        goto err;
417    }
418    /*  if the signature is correct u1 is equal to sig->r */
419    ret = (BN_ucmp(u1, sig->r) == 0);
420 err:
421    BN_CTX_end(ctx);
422    BN_CTX_free(ctx);
423    EC_POINT_free(point);
424    return ret;
425}
426