xref: /freebsd/crypto/openssl/crypto/ec/ecdsa_ossl.c (revision a7148ab39c03abd4d1a84997c70bf96f15dd2a09) 
1 /*
2  * Copyright 2002-2024 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 
134     if ((order = EC_GROUP_get0_order(group)) == NULL) {
135         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
136         goto err;
137     }
138 
139     /* Preallocate space */
140     order_bits = BN_num_bits(order);
141     /* Check the number of bits here so that an infinite loop is not possible */
142     if (order_bits < MIN_ECDSA_SIGN_ORDERBITS
143         || !BN_set_bit(k, order_bits)
144         || !BN_set_bit(r, order_bits)
145         || !BN_set_bit(X, order_bits))
146         goto err;
147 
148     do {
149         /* get random k */
150         do {
151             if (dgst != NULL) {
152                 if (!ossl_bn_gen_dsa_nonce_fixed_top(k, order, priv_key,
153                                                      dgst, dlen, ctx)) {
154                     ERR_raise(ERR_LIB_EC, EC_R_RANDOM_NUMBER_GENERATION_FAILED);
155                     goto err;
156                 }
157             } else {
158                 if (!ossl_bn_priv_rand_range_fixed_top(k, order, 0, ctx)) {
159                     ERR_raise(ERR_LIB_EC, EC_R_RANDOM_NUMBER_GENERATION_FAILED);
160                     goto err;
161                 }
162             }
163         } while (ossl_bn_is_word_fixed_top(k, 0));
164 
165         /* compute r the x-coordinate of generator * k */
166         if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
167             ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
168             goto err;
169         }
170 
171         if (!EC_POINT_get_affine_coordinates(group, tmp_point, X, NULL, ctx)) {
172             ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
173             goto err;
174         }
175 
176         if (!BN_nnmod(r, X, order, ctx)) {
177             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
178             goto err;
179         }
180     } while (BN_is_zero(r));
181 
182     /* compute the inverse of k */
183     if (!ossl_ec_group_do_inverse_ord(group, k, k, ctx)) {
184         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
185         goto err;
186     }
187 
188     /* clear old values if necessary */
189     BN_clear_free(*rp);
190     BN_clear_free(*kinvp);
191     /* save the pre-computed values  */
192     *rp = r;
193     *kinvp = k;
194     ret = 1;
195  err:
196     if (!ret) {
197         BN_clear_free(k);
198         BN_clear_free(r);
199     }
200     if (ctx != ctx_in)
201         BN_CTX_free(ctx);
202     EC_POINT_free(tmp_point);
203     BN_clear_free(X);
204     return ret;
205 }
206 
ossl_ecdsa_simple_sign_setup(EC_KEY * eckey,BN_CTX * ctx_in,BIGNUM ** kinvp,BIGNUM ** rp)207 int ossl_ecdsa_simple_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
208                                  BIGNUM **rp)
209 {
210     return ecdsa_sign_setup(eckey, ctx_in, kinvp, rp, NULL, 0);
211 }
212 
ossl_ecdsa_simple_sign_sig(const unsigned char * dgst,int dgst_len,const BIGNUM * in_kinv,const BIGNUM * in_r,EC_KEY * eckey)213 ECDSA_SIG *ossl_ecdsa_simple_sign_sig(const unsigned char *dgst, int dgst_len,
214                                       const BIGNUM *in_kinv, const BIGNUM *in_r,
215                                       EC_KEY *eckey)
216 {
217     int ok = 0, i;
218     int retries = 0;
219     BIGNUM *kinv = NULL, *s, *m = NULL;
220     const BIGNUM *order, *ckinv;
221     BN_CTX *ctx = NULL;
222     const EC_GROUP *group;
223     ECDSA_SIG *ret;
224     const BIGNUM *priv_key;
225 
226     group = EC_KEY_get0_group(eckey);
227     priv_key = EC_KEY_get0_private_key(eckey);
228 
229     if (group == NULL) {
230         ERR_raise(ERR_LIB_EC, ERR_R_PASSED_NULL_PARAMETER);
231         return NULL;
232     }
233     if (priv_key == NULL) {
234         ERR_raise(ERR_LIB_EC, EC_R_MISSING_PRIVATE_KEY);
235         return NULL;
236     }
237 
238     if (!EC_KEY_can_sign(eckey)) {
239         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
240         return NULL;
241     }
242 
243     ret = ECDSA_SIG_new();
244     if (ret == NULL) {
245         ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
246         return NULL;
247     }
248     ret->r = BN_new();
249     ret->s = BN_new();
250     if (ret->r == NULL || ret->s == NULL) {
251         ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
252         goto err;
253     }
254     s = ret->s;
255 
256     if ((ctx = BN_CTX_new_ex(eckey->libctx)) == NULL
257         || (m = BN_new()) == NULL) {
258         ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
259         goto err;
260     }
261 
262     if ((order = EC_GROUP_get0_order(group)) == NULL) {
263         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
264         goto err;
265     }
266 
267     i = BN_num_bits(order);
268     /*
269      * Need to truncate digest if it is too long: first truncate whole bytes.
270      */
271     if (8 * dgst_len > i)
272         dgst_len = (i + 7) / 8;
273     if (!BN_bin2bn(dgst, dgst_len, m)) {
274         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
275         goto err;
276     }
277     /* If still too long, truncate remaining bits with a shift */
278     if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
279         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
280         goto err;
281     }
282     do {
283         if (in_kinv == NULL || in_r == NULL) {
284             if (!ecdsa_sign_setup(eckey, ctx, &kinv, &ret->r, dgst, dgst_len)) {
285                 ERR_raise(ERR_LIB_EC, ERR_R_ECDSA_LIB);
286                 goto err;
287             }
288             ckinv = kinv;
289         } else {
290             ckinv = in_kinv;
291             if (BN_copy(ret->r, in_r) == NULL) {
292                 ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
293                 goto err;
294             }
295         }
296 
297         /*
298          * With only one multiplicant being in Montgomery domain
299          * multiplication yields real result without post-conversion.
300          * Also note that all operations but last are performed with
301          * zero-padded vectors. Last operation, BN_mod_mul_montgomery
302          * below, returns user-visible value with removed zero padding.
303          */
304         if (!bn_to_mont_fixed_top(s, ret->r, group->mont_data, ctx)
305             || !bn_mul_mont_fixed_top(s, s, priv_key, group->mont_data, ctx)) {
306             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
307             goto err;
308         }
309         if (!bn_mod_add_fixed_top(s, s, m, order)) {
310             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
311             goto err;
312         }
313         /*
314          * |s| can still be larger than modulus, because |m| can be. In
315          * such case we count on Montgomery reduction to tie it up.
316          */
317         if (!bn_to_mont_fixed_top(s, s, group->mont_data, ctx)
318             || !BN_mod_mul_montgomery(s, s, ckinv, group->mont_data, ctx)) {
319             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
320             goto err;
321         }
322 
323         if (BN_is_zero(s)) {
324             /*
325              * if kinv and r have been supplied by the caller, don't
326              * generate new kinv and r values
327              */
328             if (in_kinv != NULL && in_r != NULL) {
329                 ERR_raise(ERR_LIB_EC, EC_R_NEED_NEW_SETUP_VALUES);
330                 goto err;
331             }
332             /* Avoid infinite loops cause by invalid group parameters */
333             if (retries++ > MAX_ECDSA_SIGN_RETRIES) {
334                 ERR_raise(ERR_LIB_EC, EC_R_TOO_MANY_RETRIES);
335                 goto err;
336             }
337         } else {
338             /* s != 0 => we have a valid signature */
339             break;
340         }
341     } while (1);
342 
343     ok = 1;
344  err:
345     if (!ok) {
346         ECDSA_SIG_free(ret);
347         ret = NULL;
348     }
349     BN_CTX_free(ctx);
350     BN_clear_free(m);
351     BN_clear_free(kinv);
352     return ret;
353 }
354 
355 /*-
356  * returns
357  *      1: correct signature
358  *      0: incorrect signature
359  *     -1: error
360  */
ossl_ecdsa_verify(int type,const unsigned char * dgst,int dgst_len,const unsigned char * sigbuf,int sig_len,EC_KEY * eckey)361 int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,
362                       const unsigned char *sigbuf, int sig_len, EC_KEY *eckey)
363 {
364     ECDSA_SIG *s;
365     const unsigned char *p = sigbuf;
366     unsigned char *der = NULL;
367     int derlen = -1;
368     int ret = -1;
369 
370     s = ECDSA_SIG_new();
371     if (s == NULL)
372         return ret;
373     if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
374         goto err;
375     /* Ensure signature uses DER and doesn't have trailing garbage */
376     derlen = i2d_ECDSA_SIG(s, &der);
377     if (derlen != sig_len || memcmp(sigbuf, der, derlen) != 0)
378         goto err;
379     ret = ECDSA_do_verify(dgst, dgst_len, s, eckey);
380  err:
381     OPENSSL_free(der);
382     ECDSA_SIG_free(s);
383     return ret;
384 }
385 
ossl_ecdsa_simple_verify_sig(const unsigned char * dgst,int dgst_len,const ECDSA_SIG * sig,EC_KEY * eckey)386 int ossl_ecdsa_simple_verify_sig(const unsigned char *dgst, int dgst_len,
387                                  const ECDSA_SIG *sig, EC_KEY *eckey)
388 {
389     int ret = -1, i;
390     BN_CTX *ctx;
391     const BIGNUM *order;
392     BIGNUM *u1, *u2, *m, *X;
393     EC_POINT *point = NULL;
394     const EC_GROUP *group;
395     const EC_POINT *pub_key;
396 
397     /* check input values */
398     if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
399         (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
400         ERR_raise(ERR_LIB_EC, EC_R_MISSING_PARAMETERS);
401         return -1;
402     }
403 
404     if (!EC_KEY_can_sign(eckey)) {
405         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
406         return -1;
407     }
408 
409     ctx = BN_CTX_new_ex(eckey->libctx);
410     if (ctx == NULL) {
411         ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
412         return -1;
413     }
414     BN_CTX_start(ctx);
415     u1 = BN_CTX_get(ctx);
416     u2 = BN_CTX_get(ctx);
417     m = BN_CTX_get(ctx);
418     X = BN_CTX_get(ctx);
419     if (X == NULL) {
420         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
421         goto err;
422     }
423 
424     order = EC_GROUP_get0_order(group);
425     if (order == NULL) {
426         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
427         goto err;
428     }
429 
430     if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
431         BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
432         BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
433         ERR_raise(ERR_LIB_EC, EC_R_BAD_SIGNATURE);
434         ret = 0;                /* signature is invalid */
435         goto err;
436     }
437     /* calculate tmp1 = inv(S) mod order */
438     if (!ossl_ec_group_do_inverse_ord(group, u2, sig->s, ctx)) {
439         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
440         goto err;
441     }
442     /* digest -> m */
443     i = BN_num_bits(order);
444     /*
445      * Need to truncate digest if it is too long: first truncate whole bytes.
446      */
447     if (8 * dgst_len > i)
448         dgst_len = (i + 7) / 8;
449     if (!BN_bin2bn(dgst, dgst_len, m)) {
450         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
451         goto err;
452     }
453     /* If still too long truncate remaining bits with a shift */
454     if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
455         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
456         goto err;
457     }
458     /* u1 = m * tmp mod order */
459     if (!BN_mod_mul(u1, m, u2, order, ctx)) {
460         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
461         goto err;
462     }
463     /* u2 = r * w mod q */
464     if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
465         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
466         goto err;
467     }
468 
469     if ((point = EC_POINT_new(group)) == NULL) {
470         ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
471         goto err;
472     }
473     if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
474         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
475         goto err;
476     }
477 
478     if (!EC_POINT_get_affine_coordinates(group, point, X, NULL, ctx)) {
479         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
480         goto err;
481     }
482 
483     if (!BN_nnmod(u1, X, order, ctx)) {
484         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
485         goto err;
486     }
487     /*  if the signature is correct u1 is equal to sig->r */
488     ret = (BN_ucmp(u1, sig->r) == 0);
489  err:
490     BN_CTX_end(ctx);
491     BN_CTX_free(ctx);
492     EC_POINT_free(point);
493     return ret;
494 }
495