xref: /freebsd/crypto/openssl/crypto/ec/ecdsa_ossl.c (revision 535af610) 
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 
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 
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 
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 
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     s = ECDSA_do_sign_ex(dgst, dlen, kinv, r, eckey);
74     if (s == NULL) {
75         *siglen = 0;
76         return 0;
77     }
78     *siglen = i2d_ECDSA_SIG(s, sig != NULL ? &sig : NULL);
79     ECDSA_SIG_free(s);
80     return 1;
81 }
82 
83 static int ecdsa_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in,
84                             BIGNUM **kinvp, BIGNUM **rp,
85                             const unsigned char *dgst, int dlen)
86 {
87     BN_CTX *ctx = NULL;
88     BIGNUM *k = NULL, *r = NULL, *X = NULL;
89     const BIGNUM *order;
90     EC_POINT *tmp_point = NULL;
91     const EC_GROUP *group;
92     int ret = 0;
93     int order_bits;
94     const BIGNUM *priv_key;
95 
96     if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL) {
97         ERR_raise(ERR_LIB_EC, ERR_R_PASSED_NULL_PARAMETER);
98         return 0;
99     }
100     if ((priv_key = EC_KEY_get0_private_key(eckey)) == NULL) {
101         ERR_raise(ERR_LIB_EC, EC_R_MISSING_PRIVATE_KEY);
102         return 0;
103     }
104 
105     if (!EC_KEY_can_sign(eckey)) {
106         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
107         return 0;
108     }
109 
110     if ((ctx = ctx_in) == NULL) {
111         if ((ctx = BN_CTX_new_ex(eckey->libctx)) == NULL) {
112             ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
113             return 0;
114         }
115     }
116 
117     k = BN_secure_new();        /* this value is later returned in *kinvp */
118     r = BN_new();               /* this value is later returned in *rp */
119     X = BN_new();
120     if (k == NULL || r == NULL || X == NULL) {
121         ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
122         goto err;
123     }
124     if ((tmp_point = EC_POINT_new(group)) == NULL) {
125         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
126         goto err;
127     }
128     order = EC_GROUP_get0_order(group);
129 
130     /* Preallocate space */
131     order_bits = BN_num_bits(order);
132     /* Check the number of bits here so that an infinite loop is not possible */
133     if (order_bits < MIN_ECDSA_SIGN_ORDERBITS
134         || !BN_set_bit(k, order_bits)
135         || !BN_set_bit(r, order_bits)
136         || !BN_set_bit(X, order_bits))
137         goto err;
138 
139     do {
140         /* get random k */
141         do {
142             if (dgst != NULL) {
143                 if (!BN_generate_dsa_nonce(k, order, priv_key,
144                                            dgst, dlen, ctx)) {
145                     ERR_raise(ERR_LIB_EC, EC_R_RANDOM_NUMBER_GENERATION_FAILED);
146                     goto err;
147                 }
148             } else {
149                 if (!BN_priv_rand_range_ex(k, order, 0, ctx)) {
150                     ERR_raise(ERR_LIB_EC, EC_R_RANDOM_NUMBER_GENERATION_FAILED);
151                     goto err;
152                 }
153             }
154         } while (BN_is_zero(k));
155 
156         /* compute r the x-coordinate of generator * k */
157         if (!EC_POINT_mul(group, tmp_point, k, NULL, NULL, ctx)) {
158             ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
159             goto err;
160         }
161 
162         if (!EC_POINT_get_affine_coordinates(group, tmp_point, X, NULL, ctx)) {
163             ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
164             goto err;
165         }
166 
167         if (!BN_nnmod(r, X, order, ctx)) {
168             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
169             goto err;
170         }
171     } while (BN_is_zero(r));
172 
173     /* compute the inverse of k */
174     if (!ossl_ec_group_do_inverse_ord(group, k, k, ctx)) {
175         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
176         goto err;
177     }
178 
179     /* clear old values if necessary */
180     BN_clear_free(*rp);
181     BN_clear_free(*kinvp);
182     /* save the pre-computed values  */
183     *rp = r;
184     *kinvp = k;
185     ret = 1;
186  err:
187     if (!ret) {
188         BN_clear_free(k);
189         BN_clear_free(r);
190     }
191     if (ctx != ctx_in)
192         BN_CTX_free(ctx);
193     EC_POINT_free(tmp_point);
194     BN_clear_free(X);
195     return ret;
196 }
197 
198 int ossl_ecdsa_simple_sign_setup(EC_KEY *eckey, BN_CTX *ctx_in, BIGNUM **kinvp,
199                                  BIGNUM **rp)
200 {
201     return ecdsa_sign_setup(eckey, ctx_in, kinvp, rp, NULL, 0);
202 }
203 
204 ECDSA_SIG *ossl_ecdsa_simple_sign_sig(const unsigned char *dgst, int dgst_len,
205                                       const BIGNUM *in_kinv, const BIGNUM *in_r,
206                                       EC_KEY *eckey)
207 {
208     int ok = 0, i;
209     int retries = 0;
210     BIGNUM *kinv = NULL, *s, *m = NULL;
211     const BIGNUM *order, *ckinv;
212     BN_CTX *ctx = NULL;
213     const EC_GROUP *group;
214     ECDSA_SIG *ret;
215     const BIGNUM *priv_key;
216 
217     group = EC_KEY_get0_group(eckey);
218     priv_key = EC_KEY_get0_private_key(eckey);
219 
220     if (group == NULL) {
221         ERR_raise(ERR_LIB_EC, ERR_R_PASSED_NULL_PARAMETER);
222         return NULL;
223     }
224     if (priv_key == NULL) {
225         ERR_raise(ERR_LIB_EC, EC_R_MISSING_PRIVATE_KEY);
226         return NULL;
227     }
228 
229     if (!EC_KEY_can_sign(eckey)) {
230         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
231         return NULL;
232     }
233 
234     ret = ECDSA_SIG_new();
235     if (ret == NULL) {
236         ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
237         return NULL;
238     }
239     ret->r = BN_new();
240     ret->s = BN_new();
241     if (ret->r == NULL || ret->s == NULL) {
242         ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
243         goto err;
244     }
245     s = ret->s;
246 
247     if ((ctx = BN_CTX_new_ex(eckey->libctx)) == NULL
248         || (m = BN_new()) == NULL) {
249         ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
250         goto err;
251     }
252 
253     order = EC_GROUP_get0_order(group);
254     i = BN_num_bits(order);
255     /*
256      * Need to truncate digest if it is too long: first truncate whole bytes.
257      */
258     if (8 * dgst_len > i)
259         dgst_len = (i + 7) / 8;
260     if (!BN_bin2bn(dgst, dgst_len, m)) {
261         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
262         goto err;
263     }
264     /* If still too long, truncate remaining bits with a shift */
265     if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
266         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
267         goto err;
268     }
269     do {
270         if (in_kinv == NULL || in_r == NULL) {
271             if (!ecdsa_sign_setup(eckey, ctx, &kinv, &ret->r, dgst, dgst_len)) {
272                 ERR_raise(ERR_LIB_EC, ERR_R_ECDSA_LIB);
273                 goto err;
274             }
275             ckinv = kinv;
276         } else {
277             ckinv = in_kinv;
278             if (BN_copy(ret->r, in_r) == NULL) {
279                 ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
280                 goto err;
281             }
282         }
283 
284         /*
285          * With only one multiplicant being in Montgomery domain
286          * multiplication yields real result without post-conversion.
287          * Also note that all operations but last are performed with
288          * zero-padded vectors. Last operation, BN_mod_mul_montgomery
289          * below, returns user-visible value with removed zero padding.
290          */
291         if (!bn_to_mont_fixed_top(s, ret->r, group->mont_data, ctx)
292             || !bn_mul_mont_fixed_top(s, s, priv_key, group->mont_data, ctx)) {
293             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
294             goto err;
295         }
296         if (!bn_mod_add_fixed_top(s, s, m, order)) {
297             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
298             goto err;
299         }
300         /*
301          * |s| can still be larger than modulus, because |m| can be. In
302          * such case we count on Montgomery reduction to tie it up.
303          */
304         if (!bn_to_mont_fixed_top(s, s, group->mont_data, ctx)
305             || !BN_mod_mul_montgomery(s, s, ckinv, group->mont_data, ctx)) {
306             ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
307             goto err;
308         }
309 
310         if (BN_is_zero(s)) {
311             /*
312              * if kinv and r have been supplied by the caller, don't
313              * generate new kinv and r values
314              */
315             if (in_kinv != NULL && in_r != NULL) {
316                 ERR_raise(ERR_LIB_EC, EC_R_NEED_NEW_SETUP_VALUES);
317                 goto err;
318             }
319             /* Avoid infinite loops cause by invalid group parameters */
320             if (retries++ > MAX_ECDSA_SIGN_RETRIES) {
321                 ERR_raise(ERR_LIB_EC, EC_R_TOO_MANY_RETRIES);
322                 goto err;
323             }
324         } else {
325             /* s != 0 => we have a valid signature */
326             break;
327         }
328     } while (1);
329 
330     ok = 1;
331  err:
332     if (!ok) {
333         ECDSA_SIG_free(ret);
334         ret = NULL;
335     }
336     BN_CTX_free(ctx);
337     BN_clear_free(m);
338     BN_clear_free(kinv);
339     return ret;
340 }
341 
342 /*-
343  * returns
344  *      1: correct signature
345  *      0: incorrect signature
346  *     -1: error
347  */
348 int ossl_ecdsa_verify(int type, const unsigned char *dgst, int dgst_len,
349                       const unsigned char *sigbuf, int sig_len, EC_KEY *eckey)
350 {
351     ECDSA_SIG *s;
352     const unsigned char *p = sigbuf;
353     unsigned char *der = NULL;
354     int derlen = -1;
355     int ret = -1;
356 
357     s = ECDSA_SIG_new();
358     if (s == NULL)
359         return ret;
360     if (d2i_ECDSA_SIG(&s, &p, sig_len) == NULL)
361         goto err;
362     /* Ensure signature uses DER and doesn't have trailing garbage */
363     derlen = i2d_ECDSA_SIG(s, &der);
364     if (derlen != sig_len || memcmp(sigbuf, der, derlen) != 0)
365         goto err;
366     ret = ECDSA_do_verify(dgst, dgst_len, s, eckey);
367  err:
368     OPENSSL_free(der);
369     ECDSA_SIG_free(s);
370     return ret;
371 }
372 
373 int ossl_ecdsa_simple_verify_sig(const unsigned char *dgst, int dgst_len,
374                                  const ECDSA_SIG *sig, EC_KEY *eckey)
375 {
376     int ret = -1, i;
377     BN_CTX *ctx;
378     const BIGNUM *order;
379     BIGNUM *u1, *u2, *m, *X;
380     EC_POINT *point = NULL;
381     const EC_GROUP *group;
382     const EC_POINT *pub_key;
383 
384     /* check input values */
385     if (eckey == NULL || (group = EC_KEY_get0_group(eckey)) == NULL ||
386         (pub_key = EC_KEY_get0_public_key(eckey)) == NULL || sig == NULL) {
387         ERR_raise(ERR_LIB_EC, EC_R_MISSING_PARAMETERS);
388         return -1;
389     }
390 
391     if (!EC_KEY_can_sign(eckey)) {
392         ERR_raise(ERR_LIB_EC, EC_R_CURVE_DOES_NOT_SUPPORT_SIGNING);
393         return -1;
394     }
395 
396     ctx = BN_CTX_new_ex(eckey->libctx);
397     if (ctx == NULL) {
398         ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
399         return -1;
400     }
401     BN_CTX_start(ctx);
402     u1 = BN_CTX_get(ctx);
403     u2 = BN_CTX_get(ctx);
404     m = BN_CTX_get(ctx);
405     X = BN_CTX_get(ctx);
406     if (X == NULL) {
407         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
408         goto err;
409     }
410 
411     order = EC_GROUP_get0_order(group);
412     if (order == NULL) {
413         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
414         goto err;
415     }
416 
417     if (BN_is_zero(sig->r) || BN_is_negative(sig->r) ||
418         BN_ucmp(sig->r, order) >= 0 || BN_is_zero(sig->s) ||
419         BN_is_negative(sig->s) || BN_ucmp(sig->s, order) >= 0) {
420         ERR_raise(ERR_LIB_EC, EC_R_BAD_SIGNATURE);
421         ret = 0;                /* signature is invalid */
422         goto err;
423     }
424     /* calculate tmp1 = inv(S) mod order */
425     if (!ossl_ec_group_do_inverse_ord(group, u2, sig->s, ctx)) {
426         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
427         goto err;
428     }
429     /* digest -> m */
430     i = BN_num_bits(order);
431     /*
432      * Need to truncate digest if it is too long: first truncate whole bytes.
433      */
434     if (8 * dgst_len > i)
435         dgst_len = (i + 7) / 8;
436     if (!BN_bin2bn(dgst, dgst_len, m)) {
437         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
438         goto err;
439     }
440     /* If still too long truncate remaining bits with a shift */
441     if ((8 * dgst_len > i) && !BN_rshift(m, m, 8 - (i & 0x7))) {
442         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
443         goto err;
444     }
445     /* u1 = m * tmp mod order */
446     if (!BN_mod_mul(u1, m, u2, order, ctx)) {
447         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
448         goto err;
449     }
450     /* u2 = r * w mod q */
451     if (!BN_mod_mul(u2, sig->r, u2, order, ctx)) {
452         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
453         goto err;
454     }
455 
456     if ((point = EC_POINT_new(group)) == NULL) {
457         ERR_raise(ERR_LIB_EC, ERR_R_MALLOC_FAILURE);
458         goto err;
459     }
460     if (!EC_POINT_mul(group, point, u1, pub_key, u2, ctx)) {
461         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
462         goto err;
463     }
464 
465     if (!EC_POINT_get_affine_coordinates(group, point, X, NULL, ctx)) {
466         ERR_raise(ERR_LIB_EC, ERR_R_EC_LIB);
467         goto err;
468     }
469 
470     if (!BN_nnmod(u1, X, order, ctx)) {
471         ERR_raise(ERR_LIB_EC, ERR_R_BN_LIB);
472         goto err;
473     }
474     /*  if the signature is correct u1 is equal to sig->r */
475     ret = (BN_ucmp(u1, sig->r) == 0);
476  err:
477     BN_CTX_end(ctx);
478     BN_CTX_free(ctx);
479     EC_POINT_free(point);
480     return ret;
481 }
482