1 /*
2  * Copyright 2002-2023 The OpenSSL Project Authors. All Rights Reserved.
3  *
4  * Licensed under the Apache License 2.0 (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 /*
11  * ECDSA low level APIs are deprecated for public use, but still ok for
12  * internal use.
13  */
14 #include "internal/deprecated.h"
15 
16 #include <string.h>
17 #include <openssl/err.h>
18 #include <openssl/obj_mac.h>
19 #include <openssl/rand.h>
20 #include "crypto/bn.h"
21 #include "ec_local.h"
22 
23 #define MIN_ECDSA_SIGN_ORDERBITS 64
24 /*
25  * It is highly unlikely that a retry will happen,
26  * Multiple retries would indicate that something is wrong
27  * with the group parameters (which would normally only happen
28  * with a bad custom group).
29  */
30 #define MAX_ECDSA_SIGN_RETRIES 8
31 
ossl_ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)32 int ossl_ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
33                           BIGNUM **rp)
34 {
35     if (eckey->group->meth->ecdsa_sign_setup == NULL) {
36         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_ECDSA);
37         return 0;
38     }
39 
40     return eckey->group->meth->ecdsa_sign_setup(eckey, ctx_in, kinvp, rp);
41 }
42 
ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len, const BIGNUM *in_kinv, const BIGNUM *in_r, EC_KEY *eckey)43 ECDSA_SIG *ossl_ecdsa_sign_sig(const unsigned char *dgst, int dgst_len,
44                                const BIGNUM *in_kinv, const BIGNUM *in_r,
45                                EC_KEY *eckey)
46 {
47     if (eckey->group->meth->ecdsa_sign_sig == NULL) {
48         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_ECDSA);
49         return NULL;
50     }
51 
52     return eckey->group->meth->ecdsa_sign_sig(dgst, dgst_len,
53                                               in_kinv, in_r, eckey);
54 }
55 
ossl_ecdsa_verify_sig(const unsigned char *dgst, int dgst_len, const ECDSA_SIG *sig, EC_KEY *eckey)56 int ossl_ecdsa_verify_sig(const unsigned char *dgst, int dgst_len,
57                           const ECDSA_SIG *sig, EC_KEY *eckey)
58 {
59     if (eckey->group->meth->ecdsa_verify_sig == NULL) {
60         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_ECDSA);
61         return 0;
62     }
63 
64     return eckey->group->meth->ecdsa_verify_sig(dgst, dgst_len, sig, eckey);
65 }
66 
ossl_ecdsa_sign(int type, const unsigned char *dgst, int dlen, unsigned char *sig, unsigned int *siglen, const BIGNUM *kinv, const BIGNUM *r, EC_KEY *eckey)67 int ossl_ecdsa_sign(int type, const unsigned char *dgst, int dlen,
68                     unsigned char *sig, unsigned int *siglen,
69                     const BIGNUM *kinv, const BIGNUM *r, EC_KEY *eckey)
70 {
71     ECDSA_SIG *s;
72 
73     if (sig == NULL && (kinv == NULL || r == NULL)) {
74         *siglen = ECDSA_size(eckey);
75         return 1;
76     }
77 
78     s = ECDSA_do_sign_ex(dgst, dlen, kinv, r, eckey);
79     if (s == NULL) {
80         *siglen = 0;
81         return 0;
82     }
83     *siglen = i2d_ECDSA_SIG(s, sig != NULL ? &sig : NULL);
84     ECDSA_SIG_free(s);
85     return 1;
86 }
87 
ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp, const unsigned char *dgst, int dlen)88 static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
89                             BIGNUM **kinvp, BIGNUM **rp,
90                             const unsigned char *dgst, int dlen)
91 {
92     BN_CTX *ctx = NULL;
93     BIGNUM *k = NULL, *r = NULL, *X = NULL;
94     const BIGNUM *order;
95     EC_POINT *tmp_point = NULL;
96     const EC_GROUP *group;
97     int ret = 0;
98     int order_bits;
99     const BIGNUM *priv_key;
100 
101     if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
102         ERR_raise(ERR_LIB_EC, ERR_R_PASSED_NULL_PARAMETER);
103         return 0;
104     }
105     if ((priv_key = EC_KEY_get0_private_key(eckey)) == NULL) {
106         ERR_raise(ERR_LIB_EC, EC_R_MISSING_PRIVATE_KEY);
107         return 0;
108     }
109 
110     if (!EC_KEY_can_sign(eckey)) {
111         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
112         return 0;
113     }
114 
115     if ((ctx = ctx_in) == NULL) {
116         if ((ctx = BN_CTX_new_ex(eckey->libctx)) == NULL) {
117             ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
118             return 0;
119         }
120     }
121 
122     k = BN_secure_new();        /* this value is later returned in *kinvp */
123     r = BN_new();               /* this value is later returned in *rp */
124     X = BN_new();
125     if (k == NULL || r == NULL || X == NULL) {
126         ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
127         goto err;
128     }
129     if ((tmp_point = EC_POINT_new(group)) == NULL) {
130         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
131         goto err;
132     }
133     order = EC_GROUP_get0_order(group);
134 
135     /* Preallocate space */
136     order_bits = BN_num_bits(order);
137     /* Check the number of bits here so that an infinite loop is not possible */
138     if (order_bits < MIN_ECDSA_SIGN_ORDERBITS
139         || !BN_set_bit(k, order_bits)
140         || !BN_set_bit(r, order_bits)
141         || !BN_set_bit(X, order_bits))
142         goto err;
143 
144     do {
145         /* get random k */
146         do {
147             if (dgst != NULL) {
148                 if (!BN_generate_dsa_nonce(k, order, priv_key,
149                                            dgst, dlen, ctx)) {
150                     ERR_raise(ERR_LIB_EC, EC_R_RANDOM_NUMBER_GENERATION_FAILED);
151                     goto err;
152                 }
153             } else {
154                 if (!BN_priv_rand_range_ex(k, order, 0, ctx)) {
155                     ERR_raise(ERR_LIB_EC, EC_R_RANDOM_NUMBER_GENERATION_FAILED);
156                     goto err;
157                 }
158             }
159         } while (BN_is_zero(k));
160 
161         /* compute r the x-coordinate of generator * k */
162         if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
163             ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
164             goto err;
165         }
166 
167         if (!EC_POINT_get_affine_coordinates(group, tmp_point, X, NULL, ctx)) {
168             ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
169             goto err;
170         }
171 
172         if (!BN_nnmod(r, X, order, ctx)) {
173             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
174             goto err;
175         }
176     } while (BN_is_zero(r));
177 
178     /* compute the inverse of k */
179     if (!ossl_ec_group_do_inverse_ord(group, k, k, ctx)) {
180         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
181         goto err;
182     }
183 
184     /* clear old values if necessary */
185     BN_clear_free(*rp);
186     BN_clear_free(*kinvp);
187     /* save the pre-computed values  */
188     *rp = r;
189     *kinvp = k;
190     ret = 1;
191  err:
192     if (!ret) {
193         BN_clear_free(k);
194         BN_clear_free(r);
195     }
196     if (ctx != ctx_in)
197         BN_CTX_free(ctx);
198     EC_POINT_free(tmp_point);
199     BN_clear_free(X);
200     return ret;
201 }
202 
ossl_ecdsa_simple_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp, BIGNUM **rp)203 int ossl_ecdsa_simple_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
204                                  BIGNUM **rp)
205 {
206     return ecdsa_sign_setup(eckey, ctx_in, kinvp, rp, NULL, 0);
207 }
208 
ossl_ecdsa_simple_sign_sig(const unsigned char *dgst, int dgst_len, const BIGNUM *in_kinv, const BIGNUM *in_r, EC_KEY *eckey)209 ECDSA_SIG *ossl_ecdsa_simple_sign_sig(const unsigned char *dgst, int dgst_len,
210                                       const BIGNUM *in_kinv, const BIGNUM *in_r,
211                                       EC_KEY *eckey)
212 {
213     int ok = 0, i;
214     int retries = 0;
215     BIGNUM *kinv = NULL, *s, *m = NULL;
216     const BIGNUM *order, *ckinv;
217     BN_CTX *ctx = NULL;
218     const EC_GROUP *group;
219     ECDSA_SIG *ret;
220     const BIGNUM *priv_key;
221 
222     group = EC_KEY_get0_group(eckey);
223     priv_key = EC_KEY_get0_private_key(eckey);
224 
225     if (group == NULL) {
226         ERR_raise(ERR_LIB_EC, ERR_R_PASSED_NULL_PARAMETER);
227         return NULL;
228     }
229     if (priv_key == NULL) {
230         ERR_raise(ERR_LIB_EC, EC_R_MISSING_PRIVATE_KEY);
231         return NULL;
232     }
233 
234     if (!EC_KEY_can_sign(eckey)) {
235         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
236         return NULL;
237     }
238 
239     ret = ECDSA_SIG_new();
240     if (ret == NULL) {
241         ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
242         return NULL;
243     }
244     ret->r = BN_new();
245     ret->s = BN_new();
246     if (ret->r == NULL || ret->s == NULL) {
247         ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
248         goto err;
249     }
250     s = ret->s;
251 
252     if ((ctx = BN_CTX_new_ex(eckey->libctx)) == NULL
253         || (m = BN_new()) == NULL) {
254         ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
255         goto err;
256     }
257 
258     order = EC_GROUP_get0_order(group);
259     i = BN_num_bits(order);
260     /*
261      * Need to truncate digest if it is too long: first truncate whole bytes.
262      */
263     if (8 * dgst_len > i)
264         dgst_len = (i + 7) / 8;
265     if (!BN_bin2bn(dgst, dgst_len, m)) {
266         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
267         goto err;
268     }
269     /* If still too long, truncate remaining bits with a shift */
270     if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
271         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
272         goto err;
273     }
274     do {
275         if (in_kinv == NULL || in_r == NULL) {
276             if (!ecdsa_sign_setup(eckey, ctx, &kinv, &ret->r, dgst, dgst_len)) {
277                 ERR_raise(ERR_LIB_EC, ERR_R_ECDSA_LIB);
278                 goto err;
279             }
280             ckinv = kinv;
281         } else {
282             ckinv = in_kinv;
283             if (BN_copy(ret->r, in_r) == NULL) {
284                 ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
285                 goto err;
286             }
287         }
288 
289         /*
290          * With only one multiplicant being in Montgomery domain
291          * multiplication yields real result without post-conversion.
292          * Also note that all operations but last are performed with
293          * zero-padded vectors. Last operation, BN_mod_mul_montgomery
294          * below, returns user-visible value with removed zero padding.
295          */
296         if (!bn_to_mont_fixed_top(s, ret->r, group->mont_data, ctx)
297             || !bn_mul_mont_fixed_top(s, s, priv_key, group->mont_data, ctx)) {
298             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
299             goto err;
300         }
301         if (!bn_mod_add_fixed_top(s, s, m, order)) {
302             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
303             goto err;
304         }
305         /*
306          * |s| can still be larger than modulus, because |m| can be. In
307          * such case we count on Montgomery reduction to tie it up.
308          */
309         if (!bn_to_mont_fixed_top(s, s, group->mont_data, ctx)
310             || !BN_mod_mul_montgomery(s, s, ckinv, group->mont_data, ctx)) {
311             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
312             goto err;
313         }
314 
315         if (BN_is_zero(s)) {
316             /*
317              * if kinv and r have been supplied by the caller, don't
318              * generate new kinv and r values
319              */
320             if (in_kinv != NULL && in_r != NULL) {
321                 ERR_raise(ERR_LIB_EC, EC_R_NEED_NEW_SETUP_VALUES);
322                 goto err;
323             }
324             /* Avoid infinite loops cause by invalid group parameters */
325             if (retries++ > MAX_ECDSA_SIGN_RETRIES) {
326                 ERR_raise(ERR_LIB_EC, EC_R_TOO_MANY_RETRIES);
327                 goto err;
328             }
329         } else {
330             /* s != 0 => we have a valid signature */
331             break;
332         }
333     } while (1);
334 
335     ok = 1;
336  err:
337     if (!ok) {
338         ECDSA_SIG_free(ret);
339         ret = NULL;
340     }
341     BN_CTX_free(ctx);
342     BN_clear_free(m);
343     BN_clear_free(kinv);
344     return ret;
345 }
346 
347 /*-
348  * returns
349  *      1: correct signature
350  *      0: incorrect signature
351  *     -1: error
352  */
ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len, const unsigned char *sigbuf, int sig_len, EC_KEY *eckey)353 int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,
354                       const unsigned char *sigbuf, int sig_len, EC_KEY *eckey)
355 {
356     ECDSA_SIG *s;
357     const unsigned char *p = sigbuf;
358     unsigned char *der = NULL;
359     int derlen = -1;
360     int ret = -1;
361 
362     s = ECDSA_SIG_new();
363     if (s == NULL)
364         return ret;
365     if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
366         goto err;
367     /* Ensure signature uses DER and doesn't have trailing garbage */
368     derlen = i2d_ECDSA_SIG(s, &der);
369     if (derlen != sig_len || memcmp(sigbuf, der, derlen) != 0)
370         goto err;
371     ret = ECDSA_do_verify(dgst, dgst_len, s, eckey);
372  err:
373     OPENSSL_free(der);
374     ECDSA_SIG_free(s);
375     return ret;
376 }
377 
ossl_ecdsa_simple_verify_sig(const unsigned char *dgst, int dgst_len, const ECDSA_SIG *sig, EC_KEY *eckey)378 int ossl_ecdsa_simple_verify_sig(const unsigned char *dgst, int dgst_len,
379                                  const ECDSA_SIG *sig, EC_KEY *eckey)
380 {
381     int ret = -1, i;
382     BN_CTX *ctx;
383     const BIGNUM *order;
384     BIGNUM *u1, *u2, *m, *X;
385     EC_POINT *point = NULL;
386     const EC_GROUP *group;
387     const EC_POINT *pub_key;
388 
389     /* check input values */
390     if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
391         (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
392         ERR_raise(ERR_LIB_EC, EC_R_MISSING_PARAMETERS);
393         return -1;
394     }
395 
396     if (!EC_KEY_can_sign(eckey)) {
397         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
398         return -1;
399     }
400 
401     ctx = BN_CTX_new_ex(eckey->libctx);
402     if (ctx == NULL) {
403         ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
404         return -1;
405     }
406     BN_CTX_start(ctx);
407     u1 = BN_CTX_get(ctx);
408     u2 = BN_CTX_get(ctx);
409     m = BN_CTX_get(ctx);
410     X = BN_CTX_get(ctx);
411     if (X == NULL) {
412         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
413         goto err;
414     }
415 
416     order = EC_GROUP_get0_order(group);
417     if (order == NULL) {
418         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
419         goto err;
420     }
421 
422     if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
423         BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
424         BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
425         ERR_raise(ERR_LIB_EC, EC_R_BAD_SIGNATURE);
426         ret = 0;                /* signature is invalid */
427         goto err;
428     }
429     /* calculate tmp1 = inv(S) mod order */
430     if (!ossl_ec_group_do_inverse_ord(group, u2, sig->s, ctx)) {
431         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
432         goto err;
433     }
434     /* digest -> m */
435     i = BN_num_bits(order);
436     /*
437      * Need to truncate digest if it is too long: first truncate whole bytes.
438      */
439     if (8 * dgst_len > i)
440         dgst_len = (i + 7) / 8;
441     if (!BN_bin2bn(dgst, dgst_len, m)) {
442         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
443         goto err;
444     }
445     /* If still too long truncate remaining bits with a shift */
446     if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
447         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
448         goto err;
449     }
450     /* u1 = m * tmp mod order */
451     if (!BN_mod_mul(u1, m, u2, order, ctx)) {
452         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
453         goto err;
454     }
455     /* u2 = r * w mod q */
456     if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
457         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
458         goto err;
459     }
460 
461     if ((point = EC_POINT_new(group)) == NULL) {
462         ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
463         goto err;
464     }
465     if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
466         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
467         goto err;
468     }
469 
470     if (!EC_POINT_get_affine_coordinates(group, point, X, NULL, ctx)) {
471         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
472         goto err;
473     }
474 
475     if (!BN_nnmod(u1, X, order, ctx)) {
476         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
477         goto err;
478     }
479     /*  if the signature is correct u1 is equal to sig->r */
480     ret = (BN_ucmp(u1, sig->r) == 0);
481  err:
482     BN_CTX_end(ctx);
483     BN_CTX_free(ctx);
484     EC_POINT_free(point);
485     return ret;
486 }
487