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
32int 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
43ECDSA_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
56int 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
67int 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
88static 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 (!ossl_bn_gen_dsa_nonce_fixed_top(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 (!ossl_bn_priv_rand_range_fixed_top(k, order, 0, ctx)) {
155                    ERR_raise(ERR_LIB_EC, EC_R_RANDOM_NUMBER_GENERATION_FAILED);
156                    goto err;
157                }
158            }
159        } while (ossl_bn_is_word_fixed_top(k, 0));
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
203int 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
209ECDSA_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 */
353int 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
378int 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