1 /*
2 * Elliptic curve DSA
3 *
4 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
5 * SPDX-License-Identifier: Apache-2.0
6 *
7 * Licensed under the Apache License, Version 2.0 (the "License"); you may
8 * not use this file except in compliance with the License.
9 * You may obtain a copy of the License at
10 *
11 * http://www.apache.org/licenses/LICENSE-2.0
12 *
13 * Unless required by applicable law or agreed to in writing, software
14 * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
15 * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
16 * See the License for the specific language governing permissions and
17 * limitations under the License.
18 *
19 * This file is part of mbed TLS (https://tls.mbed.org)
20 */
21
22 /*
23 * References:
24 *
25 * SEC1 http://www.secg.org/index.php?action=secg,docs_secg
26 */
27
28 #if !defined(MBEDTLS_CONFIG_FILE)
29 #include "mbedtls/config.h"
30 #else
31 #include MBEDTLS_CONFIG_FILE
32 #endif
33
34 #if defined(MBEDTLS_ECDSA_C)
35
36 #include "mbedtls/ecdsa.h"
37 #include "mbedtls/asn1write.h"
38
39 #include <string.h>
40
41 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
42 #include "mbedtls/hmac_drbg.h"
43 #endif
44
45 #if defined(MBEDTLS_PLATFORM_C)
46 #include "mbedtls/platform.h"
47 #else
48 #include <stdlib.h>
49 #define mbedtls_calloc calloc
50 #define mbedtls_free free
51 #endif
52
53 #include "mbedtls/platform_util.h"
54
55 /* Parameter validation macros based on platform_util.h */
56 #define ECDSA_VALIDATE_RET( cond ) \
57 MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_ECP_BAD_INPUT_DATA )
58 #define ECDSA_VALIDATE( cond ) \
59 MBEDTLS_INTERNAL_VALIDATE( cond )
60
61 #if defined(MBEDTLS_ECP_RESTARTABLE)
62
63 /*
64 * Sub-context for ecdsa_verify()
65 */
66 struct mbedtls_ecdsa_restart_ver
67 {
68 mbedtls_mpi u1, u2; /* intermediate values */
69 enum { /* what to do next? */
70 ecdsa_ver_init = 0, /* getting started */
71 ecdsa_ver_muladd, /* muladd step */
72 } state;
73 };
74
75 /*
76 * Init verify restart sub-context
77 */
ecdsa_restart_ver_init(mbedtls_ecdsa_restart_ver_ctx * ctx)78 static void ecdsa_restart_ver_init( mbedtls_ecdsa_restart_ver_ctx *ctx )
79 {
80 mbedtls_mpi_init( &ctx->u1 );
81 mbedtls_mpi_init( &ctx->u2 );
82 ctx->state = ecdsa_ver_init;
83 }
84
85 /*
86 * Free the components of a verify restart sub-context
87 */
ecdsa_restart_ver_free(mbedtls_ecdsa_restart_ver_ctx * ctx)88 static void ecdsa_restart_ver_free( mbedtls_ecdsa_restart_ver_ctx *ctx )
89 {
90 if( ctx == NULL )
91 return;
92
93 mbedtls_mpi_free( &ctx->u1 );
94 mbedtls_mpi_free( &ctx->u2 );
95
96 ecdsa_restart_ver_init( ctx );
97 }
98
99 /*
100 * Sub-context for ecdsa_sign()
101 */
102 struct mbedtls_ecdsa_restart_sig
103 {
104 int sign_tries;
105 int key_tries;
106 mbedtls_mpi k; /* per-signature random */
107 mbedtls_mpi r; /* r value */
108 enum { /* what to do next? */
109 ecdsa_sig_init = 0, /* getting started */
110 ecdsa_sig_mul, /* doing ecp_mul() */
111 ecdsa_sig_modn, /* mod N computations */
112 } state;
113 };
114
115 /*
116 * Init verify sign sub-context
117 */
ecdsa_restart_sig_init(mbedtls_ecdsa_restart_sig_ctx * ctx)118 static void ecdsa_restart_sig_init( mbedtls_ecdsa_restart_sig_ctx *ctx )
119 {
120 ctx->sign_tries = 0;
121 ctx->key_tries = 0;
122 mbedtls_mpi_init( &ctx->k );
123 mbedtls_mpi_init( &ctx->r );
124 ctx->state = ecdsa_sig_init;
125 }
126
127 /*
128 * Free the components of a sign restart sub-context
129 */
ecdsa_restart_sig_free(mbedtls_ecdsa_restart_sig_ctx * ctx)130 static void ecdsa_restart_sig_free( mbedtls_ecdsa_restart_sig_ctx *ctx )
131 {
132 if( ctx == NULL )
133 return;
134
135 mbedtls_mpi_free( &ctx->k );
136 mbedtls_mpi_free( &ctx->r );
137 }
138
139 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
140 /*
141 * Sub-context for ecdsa_sign_det()
142 */
143 struct mbedtls_ecdsa_restart_det
144 {
145 mbedtls_hmac_drbg_context rng_ctx; /* DRBG state */
146 enum { /* what to do next? */
147 ecdsa_det_init = 0, /* getting started */
148 ecdsa_det_sign, /* make signature */
149 } state;
150 };
151
152 /*
153 * Init verify sign_det sub-context
154 */
ecdsa_restart_det_init(mbedtls_ecdsa_restart_det_ctx * ctx)155 static void ecdsa_restart_det_init( mbedtls_ecdsa_restart_det_ctx *ctx )
156 {
157 mbedtls_hmac_drbg_init( &ctx->rng_ctx );
158 ctx->state = ecdsa_det_init;
159 }
160
161 /*
162 * Free the components of a sign_det restart sub-context
163 */
ecdsa_restart_det_free(mbedtls_ecdsa_restart_det_ctx * ctx)164 static void ecdsa_restart_det_free( mbedtls_ecdsa_restart_det_ctx *ctx )
165 {
166 if( ctx == NULL )
167 return;
168
169 mbedtls_hmac_drbg_free( &ctx->rng_ctx );
170
171 ecdsa_restart_det_init( ctx );
172 }
173 #endif /* MBEDTLS_ECDSA_DETERMINISTIC */
174
175 #define ECDSA_RS_ECP &rs_ctx->ecp
176
177 /* Utility macro for checking and updating ops budget */
178 #define ECDSA_BUDGET( ops ) \
179 MBEDTLS_MPI_CHK( mbedtls_ecp_check_budget( grp, &rs_ctx->ecp, ops ) );
180
181 /* Call this when entering a function that needs its own sub-context */
182 #define ECDSA_RS_ENTER( SUB ) do { \
183 /* reset ops count for this call if top-level */ \
184 if( rs_ctx != NULL && rs_ctx->ecp.depth++ == 0 ) \
185 rs_ctx->ecp.ops_done = 0; \
186 \
187 /* set up our own sub-context if needed */ \
188 if( mbedtls_ecp_restart_is_enabled() && \
189 rs_ctx != NULL && rs_ctx->SUB == NULL ) \
190 { \
191 rs_ctx->SUB = mbedtls_calloc( 1, sizeof( *rs_ctx->SUB ) ); \
192 if( rs_ctx->SUB == NULL ) \
193 return( MBEDTLS_ERR_ECP_ALLOC_FAILED ); \
194 \
195 ecdsa_restart_## SUB ##_init( rs_ctx->SUB ); \
196 } \
197 } while( 0 )
198
199 /* Call this when leaving a function that needs its own sub-context */
200 #define ECDSA_RS_LEAVE( SUB ) do { \
201 /* clear our sub-context when not in progress (done or error) */ \
202 if( rs_ctx != NULL && rs_ctx->SUB != NULL && \
203 ret != MBEDTLS_ERR_ECP_IN_PROGRESS ) \
204 { \
205 ecdsa_restart_## SUB ##_free( rs_ctx->SUB ); \
206 mbedtls_free( rs_ctx->SUB ); \
207 rs_ctx->SUB = NULL; \
208 } \
209 \
210 if( rs_ctx != NULL ) \
211 rs_ctx->ecp.depth--; \
212 } while( 0 )
213
214 #else /* MBEDTLS_ECP_RESTARTABLE */
215
216 #define ECDSA_RS_ECP NULL
217
218 #define ECDSA_BUDGET( ops ) /* no-op; for compatibility */
219
220 #define ECDSA_RS_ENTER( SUB ) (void) rs_ctx
221 #define ECDSA_RS_LEAVE( SUB ) (void) rs_ctx
222
223 #endif /* MBEDTLS_ECP_RESTARTABLE */
224
225 /*
226 * Derive a suitable integer for group grp from a buffer of length len
227 * SEC1 4.1.3 step 5 aka SEC1 4.1.4 step 3
228 */
derive_mpi(const mbedtls_ecp_group * grp,mbedtls_mpi * x,const unsigned char * buf,size_t blen)229 static int derive_mpi( const mbedtls_ecp_group *grp, mbedtls_mpi *x,
230 const unsigned char *buf, size_t blen )
231 {
232 int ret;
233 size_t n_size = ( grp->nbits + 7 ) / 8;
234 size_t use_size = blen > n_size ? n_size : blen;
235
236 MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( x, buf, use_size ) );
237 if( use_size * 8 > grp->nbits )
238 MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( x, use_size * 8 - grp->nbits ) );
239
240 /* While at it, reduce modulo N */
241 if( mbedtls_mpi_cmp_mpi( x, &grp->N ) >= 0 )
242 MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( x, x, &grp->N ) );
243
244 cleanup:
245 return( ret );
246 }
247
248 #if !defined(MBEDTLS_ECDSA_SIGN_ALT)
249 /*
250 * Compute ECDSA signature of a hashed message (SEC1 4.1.3)
251 * Obviously, compared to SEC1 4.1.3, we skip step 4 (hash message)
252 */
ecdsa_sign_restartable(mbedtls_ecp_group * grp,mbedtls_mpi * r,mbedtls_mpi * s,const mbedtls_mpi * d,const unsigned char * buf,size_t blen,int (* f_rng)(void *,unsigned char *,size_t),void * p_rng,mbedtls_ecdsa_restart_ctx * rs_ctx)253 static int ecdsa_sign_restartable( mbedtls_ecp_group *grp,
254 mbedtls_mpi *r, mbedtls_mpi *s,
255 const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
256 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng,
257 mbedtls_ecdsa_restart_ctx *rs_ctx )
258 {
259 int ret, key_tries, sign_tries;
260 int *p_sign_tries = &sign_tries, *p_key_tries = &key_tries;
261 mbedtls_ecp_point R;
262 mbedtls_mpi k, e, t;
263 mbedtls_mpi *pk = &k, *pr = r;
264
265 /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */
266 if( grp->N.p == NULL )
267 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
268
269 /* Make sure d is in range 1..n-1 */
270 if( mbedtls_mpi_cmp_int( d, 1 ) < 0 || mbedtls_mpi_cmp_mpi( d, &grp->N ) >= 0 )
271 return( MBEDTLS_ERR_ECP_INVALID_KEY );
272
273 mbedtls_ecp_point_init( &R );
274 mbedtls_mpi_init( &k ); mbedtls_mpi_init( &e ); mbedtls_mpi_init( &t );
275
276 ECDSA_RS_ENTER( sig );
277
278 #if defined(MBEDTLS_ECP_RESTARTABLE)
279 if( rs_ctx != NULL && rs_ctx->sig != NULL )
280 {
281 /* redirect to our context */
282 p_sign_tries = &rs_ctx->sig->sign_tries;
283 p_key_tries = &rs_ctx->sig->key_tries;
284 pk = &rs_ctx->sig->k;
285 pr = &rs_ctx->sig->r;
286
287 /* jump to current step */
288 if( rs_ctx->sig->state == ecdsa_sig_mul )
289 goto mul;
290 if( rs_ctx->sig->state == ecdsa_sig_modn )
291 goto modn;
292 }
293 #endif /* MBEDTLS_ECP_RESTARTABLE */
294
295 *p_sign_tries = 0;
296 do
297 {
298 if( *p_sign_tries++ > 10 )
299 {
300 ret = MBEDTLS_ERR_ECP_RANDOM_FAILED;
301 goto cleanup;
302 }
303
304 /*
305 * Steps 1-3: generate a suitable ephemeral keypair
306 * and set r = xR mod n
307 */
308 *p_key_tries = 0;
309 do
310 {
311 if( *p_key_tries++ > 10 )
312 {
313 ret = MBEDTLS_ERR_ECP_RANDOM_FAILED;
314 goto cleanup;
315 }
316
317 MBEDTLS_MPI_CHK( mbedtls_ecp_gen_privkey( grp, pk, f_rng, p_rng ) );
318
319 #if defined(MBEDTLS_ECP_RESTARTABLE)
320 if( rs_ctx != NULL && rs_ctx->sig != NULL )
321 rs_ctx->sig->state = ecdsa_sig_mul;
322
323 mul:
324 #endif
325 MBEDTLS_MPI_CHK( mbedtls_ecp_mul_restartable( grp, &R, pk, &grp->G,
326 f_rng, p_rng, ECDSA_RS_ECP ) );
327 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pr, &R.X, &grp->N ) );
328 }
329 while( mbedtls_mpi_cmp_int( pr, 0 ) == 0 );
330
331 #if defined(MBEDTLS_ECP_RESTARTABLE)
332 if( rs_ctx != NULL && rs_ctx->sig != NULL )
333 rs_ctx->sig->state = ecdsa_sig_modn;
334
335 modn:
336 #endif
337 /*
338 * Accounting for everything up to the end of the loop
339 * (step 6, but checking now avoids saving e and t)
340 */
341 ECDSA_BUDGET( MBEDTLS_ECP_OPS_INV + 4 );
342
343 /*
344 * Step 5: derive MPI from hashed message
345 */
346 MBEDTLS_MPI_CHK( derive_mpi( grp, &e, buf, blen ) );
347
348 /*
349 * Generate a random value to blind inv_mod in next step,
350 * avoiding a potential timing leak.
351 */
352 MBEDTLS_MPI_CHK( mbedtls_ecp_gen_privkey( grp, &t, f_rng, p_rng ) );
353
354 /*
355 * Step 6: compute s = (e + r * d) / k = t (e + rd) / (kt) mod n
356 */
357 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( s, pr, d ) );
358 MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &e, &e, s ) );
359 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &e, &e, &t ) );
360 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( pk, pk, &t ) );
361 MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( s, pk, &grp->N ) );
362 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( s, s, &e ) );
363 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( s, s, &grp->N ) );
364 }
365 while( mbedtls_mpi_cmp_int( s, 0 ) == 0 );
366
367 #if defined(MBEDTLS_ECP_RESTARTABLE)
368 if( rs_ctx != NULL && rs_ctx->sig != NULL )
369 mbedtls_mpi_copy( r, pr );
370 #endif
371
372 cleanup:
373 mbedtls_ecp_point_free( &R );
374 mbedtls_mpi_free( &k ); mbedtls_mpi_free( &e ); mbedtls_mpi_free( &t );
375
376 ECDSA_RS_LEAVE( sig );
377
378 return( ret );
379 }
380
381 /*
382 * Compute ECDSA signature of a hashed message
383 */
mbedtls_ecdsa_sign(mbedtls_ecp_group * grp,mbedtls_mpi * r,mbedtls_mpi * s,const mbedtls_mpi * d,const unsigned char * buf,size_t blen,int (* f_rng)(void *,unsigned char *,size_t),void * p_rng)384 int mbedtls_ecdsa_sign( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
385 const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
386 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
387 {
388 ECDSA_VALIDATE_RET( grp != NULL );
389 ECDSA_VALIDATE_RET( r != NULL );
390 ECDSA_VALIDATE_RET( s != NULL );
391 ECDSA_VALIDATE_RET( d != NULL );
392 ECDSA_VALIDATE_RET( f_rng != NULL );
393 ECDSA_VALIDATE_RET( buf != NULL || blen == 0 );
394
395 return( ecdsa_sign_restartable( grp, r, s, d, buf, blen,
396 f_rng, p_rng, NULL ) );
397 }
398 #endif /* !MBEDTLS_ECDSA_SIGN_ALT */
399
400 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
401 /*
402 * Deterministic signature wrapper
403 */
ecdsa_sign_det_restartable(mbedtls_ecp_group * grp,mbedtls_mpi * r,mbedtls_mpi * s,const mbedtls_mpi * d,const unsigned char * buf,size_t blen,mbedtls_md_type_t md_alg,mbedtls_ecdsa_restart_ctx * rs_ctx)404 static int ecdsa_sign_det_restartable( mbedtls_ecp_group *grp,
405 mbedtls_mpi *r, mbedtls_mpi *s,
406 const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
407 mbedtls_md_type_t md_alg,
408 mbedtls_ecdsa_restart_ctx *rs_ctx )
409 {
410 int ret;
411 mbedtls_hmac_drbg_context rng_ctx;
412 mbedtls_hmac_drbg_context *p_rng = &rng_ctx;
413 unsigned char data[2 * MBEDTLS_ECP_MAX_BYTES];
414 size_t grp_len = ( grp->nbits + 7 ) / 8;
415 const mbedtls_md_info_t *md_info;
416 mbedtls_mpi h;
417
418 if( ( md_info = mbedtls_md_info_from_type( md_alg ) ) == NULL )
419 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
420
421 mbedtls_mpi_init( &h );
422 mbedtls_hmac_drbg_init( &rng_ctx );
423
424 ECDSA_RS_ENTER( det );
425
426 #if defined(MBEDTLS_ECP_RESTARTABLE)
427 if( rs_ctx != NULL && rs_ctx->det != NULL )
428 {
429 /* redirect to our context */
430 p_rng = &rs_ctx->det->rng_ctx;
431
432 /* jump to current step */
433 if( rs_ctx->det->state == ecdsa_det_sign )
434 goto sign;
435 }
436 #endif /* MBEDTLS_ECP_RESTARTABLE */
437
438 /* Use private key and message hash (reduced) to initialize HMAC_DRBG */
439 MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( d, data, grp_len ) );
440 MBEDTLS_MPI_CHK( derive_mpi( grp, &h, buf, blen ) );
441 MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &h, data + grp_len, grp_len ) );
442 mbedtls_hmac_drbg_seed_buf( p_rng, md_info, data, 2 * grp_len );
443
444 #if defined(MBEDTLS_ECP_RESTARTABLE)
445 if( rs_ctx != NULL && rs_ctx->det != NULL )
446 rs_ctx->det->state = ecdsa_det_sign;
447
448 sign:
449 #endif
450 #if defined(MBEDTLS_ECDSA_SIGN_ALT)
451 ret = mbedtls_ecdsa_sign( grp, r, s, d, buf, blen,
452 mbedtls_hmac_drbg_random, p_rng );
453 #else
454 ret = ecdsa_sign_restartable( grp, r, s, d, buf, blen,
455 mbedtls_hmac_drbg_random, p_rng, rs_ctx );
456 #endif /* MBEDTLS_ECDSA_SIGN_ALT */
457
458 cleanup:
459 mbedtls_hmac_drbg_free( &rng_ctx );
460 mbedtls_mpi_free( &h );
461
462 ECDSA_RS_LEAVE( det );
463
464 return( ret );
465 }
466
467 /*
468 * Deterministic signature wrapper
469 */
mbedtls_ecdsa_sign_det(mbedtls_ecp_group * grp,mbedtls_mpi * r,mbedtls_mpi * s,const mbedtls_mpi * d,const unsigned char * buf,size_t blen,mbedtls_md_type_t md_alg)470 int mbedtls_ecdsa_sign_det( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
471 const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
472 mbedtls_md_type_t md_alg )
473 {
474 ECDSA_VALIDATE_RET( grp != NULL );
475 ECDSA_VALIDATE_RET( r != NULL );
476 ECDSA_VALIDATE_RET( s != NULL );
477 ECDSA_VALIDATE_RET( d != NULL );
478 ECDSA_VALIDATE_RET( buf != NULL || blen == 0 );
479
480 return( ecdsa_sign_det_restartable( grp, r, s, d, buf, blen, md_alg, NULL ) );
481 }
482 #endif /* MBEDTLS_ECDSA_DETERMINISTIC */
483
484 #if !defined(MBEDTLS_ECDSA_VERIFY_ALT)
485 /*
486 * Verify ECDSA signature of hashed message (SEC1 4.1.4)
487 * Obviously, compared to SEC1 4.1.3, we skip step 2 (hash message)
488 */
ecdsa_verify_restartable(mbedtls_ecp_group * grp,const unsigned char * buf,size_t blen,const mbedtls_ecp_point * Q,const mbedtls_mpi * r,const mbedtls_mpi * s,mbedtls_ecdsa_restart_ctx * rs_ctx)489 static int ecdsa_verify_restartable( mbedtls_ecp_group *grp,
490 const unsigned char *buf, size_t blen,
491 const mbedtls_ecp_point *Q,
492 const mbedtls_mpi *r, const mbedtls_mpi *s,
493 mbedtls_ecdsa_restart_ctx *rs_ctx )
494 {
495 int ret;
496 mbedtls_mpi e, s_inv, u1, u2;
497 mbedtls_ecp_point R;
498 mbedtls_mpi *pu1 = &u1, *pu2 = &u2;
499
500 mbedtls_ecp_point_init( &R );
501 mbedtls_mpi_init( &e ); mbedtls_mpi_init( &s_inv );
502 mbedtls_mpi_init( &u1 ); mbedtls_mpi_init( &u2 );
503
504 /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */
505 if( grp->N.p == NULL )
506 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
507
508 ECDSA_RS_ENTER( ver );
509
510 #if defined(MBEDTLS_ECP_RESTARTABLE)
511 if( rs_ctx != NULL && rs_ctx->ver != NULL )
512 {
513 /* redirect to our context */
514 pu1 = &rs_ctx->ver->u1;
515 pu2 = &rs_ctx->ver->u2;
516
517 /* jump to current step */
518 if( rs_ctx->ver->state == ecdsa_ver_muladd )
519 goto muladd;
520 }
521 #endif /* MBEDTLS_ECP_RESTARTABLE */
522
523 /*
524 * Step 1: make sure r and s are in range 1..n-1
525 */
526 if( mbedtls_mpi_cmp_int( r, 1 ) < 0 || mbedtls_mpi_cmp_mpi( r, &grp->N ) >= 0 ||
527 mbedtls_mpi_cmp_int( s, 1 ) < 0 || mbedtls_mpi_cmp_mpi( s, &grp->N ) >= 0 )
528 {
529 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
530 goto cleanup;
531 }
532
533 /*
534 * Step 3: derive MPI from hashed message
535 */
536 MBEDTLS_MPI_CHK( derive_mpi( grp, &e, buf, blen ) );
537
538 /*
539 * Step 4: u1 = e / s mod n, u2 = r / s mod n
540 */
541 ECDSA_BUDGET( MBEDTLS_ECP_OPS_CHK + MBEDTLS_ECP_OPS_INV + 2 );
542
543 MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( &s_inv, s, &grp->N ) );
544
545 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( pu1, &e, &s_inv ) );
546 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pu1, pu1, &grp->N ) );
547
548 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( pu2, r, &s_inv ) );
549 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( pu2, pu2, &grp->N ) );
550
551 #if defined(MBEDTLS_ECP_RESTARTABLE)
552 if( rs_ctx != NULL && rs_ctx->ver != NULL )
553 rs_ctx->ver->state = ecdsa_ver_muladd;
554
555 muladd:
556 #endif
557 /*
558 * Step 5: R = u1 G + u2 Q
559 */
560 MBEDTLS_MPI_CHK( mbedtls_ecp_muladd_restartable( grp,
561 &R, pu1, &grp->G, pu2, Q, ECDSA_RS_ECP ) );
562
563 if( mbedtls_ecp_is_zero( &R ) )
564 {
565 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
566 goto cleanup;
567 }
568
569 /*
570 * Step 6: convert xR to an integer (no-op)
571 * Step 7: reduce xR mod n (gives v)
572 */
573 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &R.X, &R.X, &grp->N ) );
574
575 /*
576 * Step 8: check if v (that is, R.X) is equal to r
577 */
578 if( mbedtls_mpi_cmp_mpi( &R.X, r ) != 0 )
579 {
580 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
581 goto cleanup;
582 }
583
584 cleanup:
585 mbedtls_ecp_point_free( &R );
586 mbedtls_mpi_free( &e ); mbedtls_mpi_free( &s_inv );
587 mbedtls_mpi_free( &u1 ); mbedtls_mpi_free( &u2 );
588
589 ECDSA_RS_LEAVE( ver );
590
591 return( ret );
592 }
593
594 /*
595 * Verify ECDSA signature of hashed message
596 */
mbedtls_ecdsa_verify(mbedtls_ecp_group * grp,const unsigned char * buf,size_t blen,const mbedtls_ecp_point * Q,const mbedtls_mpi * r,const mbedtls_mpi * s)597 int mbedtls_ecdsa_verify( mbedtls_ecp_group *grp,
598 const unsigned char *buf, size_t blen,
599 const mbedtls_ecp_point *Q,
600 const mbedtls_mpi *r,
601 const mbedtls_mpi *s)
602 {
603 ECDSA_VALIDATE_RET( grp != NULL );
604 ECDSA_VALIDATE_RET( Q != NULL );
605 ECDSA_VALIDATE_RET( r != NULL );
606 ECDSA_VALIDATE_RET( s != NULL );
607 ECDSA_VALIDATE_RET( buf != NULL || blen == 0 );
608
609 return( ecdsa_verify_restartable( grp, buf, blen, Q, r, s, NULL ) );
610 }
611 #endif /* !MBEDTLS_ECDSA_VERIFY_ALT */
612
613 /*
614 * Convert a signature (given by context) to ASN.1
615 */
ecdsa_signature_to_asn1(const mbedtls_mpi * r,const mbedtls_mpi * s,unsigned char * sig,size_t * slen)616 static int ecdsa_signature_to_asn1( const mbedtls_mpi *r, const mbedtls_mpi *s,
617 unsigned char *sig, size_t *slen )
618 {
619 int ret;
620 unsigned char buf[MBEDTLS_ECDSA_MAX_LEN];
621 unsigned char *p = buf + sizeof( buf );
622 size_t len = 0;
623
624 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &p, buf, s ) );
625 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &p, buf, r ) );
626
627 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &p, buf, len ) );
628 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &p, buf,
629 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );
630
631 memcpy( sig, p, len );
632 *slen = len;
633
634 return( 0 );
635 }
636
637 /*
638 * Compute and write signature
639 */
mbedtls_ecdsa_write_signature_restartable(mbedtls_ecdsa_context * ctx,mbedtls_md_type_t md_alg,const unsigned char * hash,size_t hlen,unsigned char * sig,size_t * slen,int (* f_rng)(void *,unsigned char *,size_t),void * p_rng,mbedtls_ecdsa_restart_ctx * rs_ctx)640 int mbedtls_ecdsa_write_signature_restartable( mbedtls_ecdsa_context *ctx,
641 mbedtls_md_type_t md_alg,
642 const unsigned char *hash, size_t hlen,
643 unsigned char *sig, size_t *slen,
644 int (*f_rng)(void *, unsigned char *, size_t),
645 void *p_rng,
646 mbedtls_ecdsa_restart_ctx *rs_ctx )
647 {
648 int ret;
649 mbedtls_mpi r, s;
650 ECDSA_VALIDATE_RET( ctx != NULL );
651 ECDSA_VALIDATE_RET( hash != NULL );
652 ECDSA_VALIDATE_RET( sig != NULL );
653 ECDSA_VALIDATE_RET( slen != NULL );
654
655 mbedtls_mpi_init( &r );
656 mbedtls_mpi_init( &s );
657
658 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
659 (void) f_rng;
660 (void) p_rng;
661
662 MBEDTLS_MPI_CHK( ecdsa_sign_det_restartable( &ctx->grp, &r, &s, &ctx->d,
663 hash, hlen, md_alg, rs_ctx ) );
664 #else
665 (void) md_alg;
666
667 #if defined(MBEDTLS_ECDSA_SIGN_ALT)
668 MBEDTLS_MPI_CHK( mbedtls_ecdsa_sign( &ctx->grp, &r, &s, &ctx->d,
669 hash, hlen, f_rng, p_rng ) );
670 #else
671 MBEDTLS_MPI_CHK( ecdsa_sign_restartable( &ctx->grp, &r, &s, &ctx->d,
672 hash, hlen, f_rng, p_rng, rs_ctx ) );
673 #endif /* MBEDTLS_ECDSA_SIGN_ALT */
674 #endif /* MBEDTLS_ECDSA_DETERMINISTIC */
675
676 MBEDTLS_MPI_CHK( ecdsa_signature_to_asn1( &r, &s, sig, slen ) );
677
678 cleanup:
679 mbedtls_mpi_free( &r );
680 mbedtls_mpi_free( &s );
681
682 return( ret );
683 }
684
685 /*
686 * Compute and write signature
687 */
mbedtls_ecdsa_write_signature(mbedtls_ecdsa_context * ctx,mbedtls_md_type_t md_alg,const unsigned char * hash,size_t hlen,unsigned char * sig,size_t * slen,int (* f_rng)(void *,unsigned char *,size_t),void * p_rng)688 int mbedtls_ecdsa_write_signature( mbedtls_ecdsa_context *ctx,
689 mbedtls_md_type_t md_alg,
690 const unsigned char *hash, size_t hlen,
691 unsigned char *sig, size_t *slen,
692 int (*f_rng)(void *, unsigned char *, size_t),
693 void *p_rng )
694 {
695 ECDSA_VALIDATE_RET( ctx != NULL );
696 ECDSA_VALIDATE_RET( hash != NULL );
697 ECDSA_VALIDATE_RET( sig != NULL );
698 ECDSA_VALIDATE_RET( slen != NULL );
699 return( mbedtls_ecdsa_write_signature_restartable(
700 ctx, md_alg, hash, hlen, sig, slen, f_rng, p_rng, NULL ) );
701 }
702
703 #if !defined(MBEDTLS_DEPRECATED_REMOVED) && \
704 defined(MBEDTLS_ECDSA_DETERMINISTIC)
mbedtls_ecdsa_write_signature_det(mbedtls_ecdsa_context * ctx,const unsigned char * hash,size_t hlen,unsigned char * sig,size_t * slen,mbedtls_md_type_t md_alg)705 int mbedtls_ecdsa_write_signature_det( mbedtls_ecdsa_context *ctx,
706 const unsigned char *hash, size_t hlen,
707 unsigned char *sig, size_t *slen,
708 mbedtls_md_type_t md_alg )
709 {
710 ECDSA_VALIDATE_RET( ctx != NULL );
711 ECDSA_VALIDATE_RET( hash != NULL );
712 ECDSA_VALIDATE_RET( sig != NULL );
713 ECDSA_VALIDATE_RET( slen != NULL );
714 return( mbedtls_ecdsa_write_signature( ctx, md_alg, hash, hlen, sig, slen,
715 NULL, NULL ) );
716 }
717 #endif
718
719 /*
720 * Read and check signature
721 */
mbedtls_ecdsa_read_signature(mbedtls_ecdsa_context * ctx,const unsigned char * hash,size_t hlen,const unsigned char * sig,size_t slen)722 int mbedtls_ecdsa_read_signature( mbedtls_ecdsa_context *ctx,
723 const unsigned char *hash, size_t hlen,
724 const unsigned char *sig, size_t slen )
725 {
726 ECDSA_VALIDATE_RET( ctx != NULL );
727 ECDSA_VALIDATE_RET( hash != NULL );
728 ECDSA_VALIDATE_RET( sig != NULL );
729 return( mbedtls_ecdsa_read_signature_restartable(
730 ctx, hash, hlen, sig, slen, NULL ) );
731 }
732
733 /*
734 * Restartable read and check signature
735 */
mbedtls_ecdsa_read_signature_restartable(mbedtls_ecdsa_context * ctx,const unsigned char * hash,size_t hlen,const unsigned char * sig,size_t slen,mbedtls_ecdsa_restart_ctx * rs_ctx)736 int mbedtls_ecdsa_read_signature_restartable( mbedtls_ecdsa_context *ctx,
737 const unsigned char *hash, size_t hlen,
738 const unsigned char *sig, size_t slen,
739 mbedtls_ecdsa_restart_ctx *rs_ctx )
740 {
741 int ret;
742 unsigned char *p = (unsigned char *) sig;
743 const unsigned char *end = sig + slen;
744 size_t len;
745 mbedtls_mpi r, s;
746 ECDSA_VALIDATE_RET( ctx != NULL );
747 ECDSA_VALIDATE_RET( hash != NULL );
748 ECDSA_VALIDATE_RET( sig != NULL );
749
750 mbedtls_mpi_init( &r );
751 mbedtls_mpi_init( &s );
752
753 if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
754 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
755 {
756 ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
757 goto cleanup;
758 }
759
760 if( p + len != end )
761 {
762 ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA +
763 MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
764 goto cleanup;
765 }
766
767 if( ( ret = mbedtls_asn1_get_mpi( &p, end, &r ) ) != 0 ||
768 ( ret = mbedtls_asn1_get_mpi( &p, end, &s ) ) != 0 )
769 {
770 ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
771 goto cleanup;
772 }
773 #if defined(MBEDTLS_ECDSA_VERIFY_ALT)
774 if( ( ret = mbedtls_ecdsa_verify( &ctx->grp, hash, hlen,
775 &ctx->Q, &r, &s ) ) != 0 )
776 goto cleanup;
777 #else
778 if( ( ret = ecdsa_verify_restartable( &ctx->grp, hash, hlen,
779 &ctx->Q, &r, &s, rs_ctx ) ) != 0 )
780 goto cleanup;
781 #endif /* MBEDTLS_ECDSA_VERIFY_ALT */
782
783 /* At this point we know that the buffer starts with a valid signature.
784 * Return 0 if the buffer just contains the signature, and a specific
785 * error code if the valid signature is followed by more data. */
786 if( p != end )
787 ret = MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH;
788
789 cleanup:
790 mbedtls_mpi_free( &r );
791 mbedtls_mpi_free( &s );
792
793 return( ret );
794 }
795
796 #if !defined(MBEDTLS_ECDSA_GENKEY_ALT)
797 /*
798 * Generate key pair
799 */
mbedtls_ecdsa_genkey(mbedtls_ecdsa_context * ctx,mbedtls_ecp_group_id gid,int (* f_rng)(void *,unsigned char *,size_t),void * p_rng)800 int mbedtls_ecdsa_genkey( mbedtls_ecdsa_context *ctx, mbedtls_ecp_group_id gid,
801 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
802 {
803 ECDSA_VALIDATE_RET( ctx != NULL );
804 ECDSA_VALIDATE_RET( f_rng != NULL );
805
806 return( mbedtls_ecp_group_load( &ctx->grp, gid ) ||
807 mbedtls_ecp_gen_keypair( &ctx->grp, &ctx->d, &ctx->Q, f_rng, p_rng ) );
808 }
809 #endif /* !MBEDTLS_ECDSA_GENKEY_ALT */
810
811 /*
812 * Set context from an mbedtls_ecp_keypair
813 */
mbedtls_ecdsa_from_keypair(mbedtls_ecdsa_context * ctx,const mbedtls_ecp_keypair * key)814 int mbedtls_ecdsa_from_keypair( mbedtls_ecdsa_context *ctx, const mbedtls_ecp_keypair *key )
815 {
816 int ret;
817 ECDSA_VALIDATE_RET( ctx != NULL );
818 ECDSA_VALIDATE_RET( key != NULL );
819
820 if( ( ret = mbedtls_ecp_group_copy( &ctx->grp, &key->grp ) ) != 0 ||
821 ( ret = mbedtls_mpi_copy( &ctx->d, &key->d ) ) != 0 ||
822 ( ret = mbedtls_ecp_copy( &ctx->Q, &key->Q ) ) != 0 )
823 {
824 mbedtls_ecdsa_free( ctx );
825 }
826
827 return( ret );
828 }
829
830 /*
831 * Initialize context
832 */
mbedtls_ecdsa_init(mbedtls_ecdsa_context * ctx)833 void mbedtls_ecdsa_init( mbedtls_ecdsa_context *ctx )
834 {
835 ECDSA_VALIDATE( ctx != NULL );
836
837 mbedtls_ecp_keypair_init( ctx );
838 }
839
840 /*
841 * Free context
842 */
mbedtls_ecdsa_free(mbedtls_ecdsa_context * ctx)843 void mbedtls_ecdsa_free( mbedtls_ecdsa_context *ctx )
844 {
845 if( ctx == NULL )
846 return;
847
848 mbedtls_ecp_keypair_free( ctx );
849 }
850
851 #if defined(MBEDTLS_ECP_RESTARTABLE)
852 /*
853 * Initialize a restart context
854 */
mbedtls_ecdsa_restart_init(mbedtls_ecdsa_restart_ctx * ctx)855 void mbedtls_ecdsa_restart_init( mbedtls_ecdsa_restart_ctx *ctx )
856 {
857 ECDSA_VALIDATE( ctx != NULL );
858
859 mbedtls_ecp_restart_init( &ctx->ecp );
860
861 ctx->ver = NULL;
862 ctx->sig = NULL;
863 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
864 ctx->det = NULL;
865 #endif
866 }
867
868 /*
869 * Free the components of a restart context
870 */
mbedtls_ecdsa_restart_free(mbedtls_ecdsa_restart_ctx * ctx)871 void mbedtls_ecdsa_restart_free( mbedtls_ecdsa_restart_ctx *ctx )
872 {
873 if( ctx == NULL )
874 return;
875
876 mbedtls_ecp_restart_free( &ctx->ecp );
877
878 ecdsa_restart_ver_free( ctx->ver );
879 mbedtls_free( ctx->ver );
880 ctx->ver = NULL;
881
882 ecdsa_restart_sig_free( ctx->sig );
883 mbedtls_free( ctx->sig );
884 ctx->sig = NULL;
885
886 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
887 ecdsa_restart_det_free( ctx->det );
888 mbedtls_free( ctx->det );
889 ctx->det = NULL;
890 #endif
891 }
892 #endif /* MBEDTLS_ECP_RESTARTABLE */
893
894 #endif /* MBEDTLS_ECDSA_C */
895