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[proxmark3-svn] / common / mbedtls / ecdsa.c
1 /*
2 * Elliptic curve DSA
3 *
4 * Copyright (C) 2006-2015, ARM Limited, All Rights Reserved
5 * SPDX-License-Identifier: GPL-2.0
6 *
7 * This program is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 2 of the License, or
10 * (at your option) any later version.
11 *
12 * This program is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License along
18 * with this program; if not, write to the Free Software Foundation, Inc.,
19 * 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
20 *
21 * This file is part of mbed TLS (https://tls.mbed.org)
22 */
23
24 /*
25 * References:
26 *
27 * SEC1 http://www.secg.org/index.php?action=secg,docs_secg
28 */
29
30 #if !defined(MBEDTLS_CONFIG_FILE)
31 #include "mbedtls/config.h"
32 #else
33 #include MBEDTLS_CONFIG_FILE
34 #endif
35
36 #if defined(MBEDTLS_ECDSA_C)
37
38 #include "mbedtls/ecdsa.h"
39 #include "mbedtls/asn1write.h"
40
41 #include <string.h>
42
43 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
44 #include "mbedtls/hmac_drbg.h"
45 #endif
46
47 /*
48 * Derive a suitable integer for group grp from a buffer of length len
49 * SEC1 4.1.3 step 5 aka SEC1 4.1.4 step 3
50 */
51 static int derive_mpi( const mbedtls_ecp_group *grp, mbedtls_mpi *x,
52 const unsigned char *buf, size_t blen )
53 {
54 int ret;
55 size_t n_size = ( grp->nbits + 7 ) / 8;
56 size_t use_size = blen > n_size ? n_size : blen;
57
58 MBEDTLS_MPI_CHK( mbedtls_mpi_read_binary( x, buf, use_size ) );
59 if( use_size * 8 > grp->nbits )
60 MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( x, use_size * 8 - grp->nbits ) );
61
62 /* While at it, reduce modulo N */
63 if( mbedtls_mpi_cmp_mpi( x, &grp->N ) >= 0 )
64 MBEDTLS_MPI_CHK( mbedtls_mpi_sub_mpi( x, x, &grp->N ) );
65
66 cleanup:
67 return( ret );
68 }
69
70 #if !defined(MBEDTLS_ECDSA_SIGN_ALT)
71 /*
72 * Compute ECDSA signature of a hashed message (SEC1 4.1.3)
73 * Obviously, compared to SEC1 4.1.3, we skip step 4 (hash message)
74 */
75 int mbedtls_ecdsa_sign( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
76 const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
77 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
78 {
79 int ret, key_tries, sign_tries, blind_tries;
80 mbedtls_ecp_point R;
81 mbedtls_mpi k, e, t;
82
83 /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */
84 if( grp->N.p == NULL )
85 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
86
87 /* Make sure d is in range 1..n-1 */
88 if( mbedtls_mpi_cmp_int( d, 1 ) < 0 || mbedtls_mpi_cmp_mpi( d, &grp->N ) >= 0 )
89 return( MBEDTLS_ERR_ECP_INVALID_KEY );
90
91 mbedtls_ecp_point_init( &R );
92 mbedtls_mpi_init( &k ); mbedtls_mpi_init( &e ); mbedtls_mpi_init( &t );
93
94 sign_tries = 0;
95 do
96 {
97 /*
98 * Steps 1-3: generate a suitable ephemeral keypair
99 * and set r = xR mod n
100 */
101 key_tries = 0;
102 do
103 {
104 MBEDTLS_MPI_CHK( mbedtls_ecp_gen_keypair( grp, &k, &R, f_rng, p_rng ) );
105 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( r, &R.X, &grp->N ) );
106
107 if( key_tries++ > 10 )
108 {
109 ret = MBEDTLS_ERR_ECP_RANDOM_FAILED;
110 goto cleanup;
111 }
112 }
113 while( mbedtls_mpi_cmp_int( r, 0 ) == 0 );
114
115 /*
116 * Step 5: derive MPI from hashed message
117 */
118 MBEDTLS_MPI_CHK( derive_mpi( grp, &e, buf, blen ) );
119
120 /*
121 * Generate a random value to blind inv_mod in next step,
122 * avoiding a potential timing leak.
123 */
124 blind_tries = 0;
125 do
126 {
127 size_t n_size = ( grp->nbits + 7 ) / 8;
128 MBEDTLS_MPI_CHK( mbedtls_mpi_fill_random( &t, n_size, f_rng, p_rng ) );
129 MBEDTLS_MPI_CHK( mbedtls_mpi_shift_r( &t, 8 * n_size - grp->nbits ) );
130
131 /* See mbedtls_ecp_gen_keypair() */
132 if( ++blind_tries > 30 )
133 return( MBEDTLS_ERR_ECP_RANDOM_FAILED );
134 }
135 while( mbedtls_mpi_cmp_int( &t, 1 ) < 0 ||
136 mbedtls_mpi_cmp_mpi( &t, &grp->N ) >= 0 );
137
138 /*
139 * Step 6: compute s = (e + r * d) / k = t (e + rd) / (kt) mod n
140 */
141 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( s, r, d ) );
142 MBEDTLS_MPI_CHK( mbedtls_mpi_add_mpi( &e, &e, s ) );
143 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &e, &e, &t ) );
144 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &k, &k, &t ) );
145 MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( s, &k, &grp->N ) );
146 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( s, s, &e ) );
147 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( s, s, &grp->N ) );
148
149 if( sign_tries++ > 10 )
150 {
151 ret = MBEDTLS_ERR_ECP_RANDOM_FAILED;
152 goto cleanup;
153 }
154 }
155 while( mbedtls_mpi_cmp_int( s, 0 ) == 0 );
156
157 cleanup:
158 mbedtls_ecp_point_free( &R );
159 mbedtls_mpi_free( &k ); mbedtls_mpi_free( &e ); mbedtls_mpi_free( &t );
160
161 return( ret );
162 }
163 #endif /* MBEDTLS_ECDSA_SIGN_ALT */
164
165 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
166 /*
167 * Deterministic signature wrapper
168 */
169 int mbedtls_ecdsa_sign_det( mbedtls_ecp_group *grp, mbedtls_mpi *r, mbedtls_mpi *s,
170 const mbedtls_mpi *d, const unsigned char *buf, size_t blen,
171 mbedtls_md_type_t md_alg )
172 {
173 int ret;
174 mbedtls_hmac_drbg_context rng_ctx;
175 unsigned char data[2 * MBEDTLS_ECP_MAX_BYTES];
176 size_t grp_len = ( grp->nbits + 7 ) / 8;
177 const mbedtls_md_info_t *md_info;
178 mbedtls_mpi h;
179
180 if( ( md_info = mbedtls_md_info_from_type( md_alg ) ) == NULL )
181 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
182
183 mbedtls_mpi_init( &h );
184 mbedtls_hmac_drbg_init( &rng_ctx );
185
186 /* Use private key and message hash (reduced) to initialize HMAC_DRBG */
187 MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( d, data, grp_len ) );
188 MBEDTLS_MPI_CHK( derive_mpi( grp, &h, buf, blen ) );
189 MBEDTLS_MPI_CHK( mbedtls_mpi_write_binary( &h, data + grp_len, grp_len ) );
190 mbedtls_hmac_drbg_seed_buf( &rng_ctx, md_info, data, 2 * grp_len );
191
192 ret = mbedtls_ecdsa_sign( grp, r, s, d, buf, blen,
193 mbedtls_hmac_drbg_random, &rng_ctx );
194
195 cleanup:
196 mbedtls_hmac_drbg_free( &rng_ctx );
197 mbedtls_mpi_free( &h );
198
199 return( ret );
200 }
201 #endif /* MBEDTLS_ECDSA_DETERMINISTIC */
202
203 #if !defined(MBEDTLS_ECDSA_VERIFY_ALT)
204 /*
205 * Verify ECDSA signature of hashed message (SEC1 4.1.4)
206 * Obviously, compared to SEC1 4.1.3, we skip step 2 (hash message)
207 */
208 int mbedtls_ecdsa_verify( mbedtls_ecp_group *grp,
209 const unsigned char *buf, size_t blen,
210 const mbedtls_ecp_point *Q, const mbedtls_mpi *r, const mbedtls_mpi *s)
211 {
212 int ret;
213 mbedtls_mpi e, s_inv, u1, u2;
214 mbedtls_ecp_point R;
215
216 mbedtls_ecp_point_init( &R );
217 mbedtls_mpi_init( &e ); mbedtls_mpi_init( &s_inv ); mbedtls_mpi_init( &u1 ); mbedtls_mpi_init( &u2 );
218
219 /* Fail cleanly on curves such as Curve25519 that can't be used for ECDSA */
220 if( grp->N.p == NULL )
221 return( MBEDTLS_ERR_ECP_BAD_INPUT_DATA );
222
223 /*
224 * Step 1: make sure r and s are in range 1..n-1
225 */
226 if( mbedtls_mpi_cmp_int( r, 1 ) < 0 || mbedtls_mpi_cmp_mpi( r, &grp->N ) >= 0 ||
227 mbedtls_mpi_cmp_int( s, 1 ) < 0 || mbedtls_mpi_cmp_mpi( s, &grp->N ) >= 0 )
228 {
229 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
230 goto cleanup;
231 }
232
233 /*
234 * Additional precaution: make sure Q is valid
235 */
236 MBEDTLS_MPI_CHK( mbedtls_ecp_check_pubkey( grp, Q ) );
237
238 /*
239 * Step 3: derive MPI from hashed message
240 */
241 MBEDTLS_MPI_CHK( derive_mpi( grp, &e, buf, blen ) );
242
243 /*
244 * Step 4: u1 = e / s mod n, u2 = r / s mod n
245 */
246 MBEDTLS_MPI_CHK( mbedtls_mpi_inv_mod( &s_inv, s, &grp->N ) );
247
248 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &u1, &e, &s_inv ) );
249 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &u1, &u1, &grp->N ) );
250
251 MBEDTLS_MPI_CHK( mbedtls_mpi_mul_mpi( &u2, r, &s_inv ) );
252 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &u2, &u2, &grp->N ) );
253
254 /*
255 * Step 5: R = u1 G + u2 Q
256 *
257 * Since we're not using any secret data, no need to pass a RNG to
258 * mbedtls_ecp_mul() for countermesures.
259 */
260 MBEDTLS_MPI_CHK( mbedtls_ecp_muladd( grp, &R, &u1, &grp->G, &u2, Q ) );
261
262 if( mbedtls_ecp_is_zero( &R ) )
263 {
264 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
265 goto cleanup;
266 }
267
268 /*
269 * Step 6: convert xR to an integer (no-op)
270 * Step 7: reduce xR mod n (gives v)
271 */
272 MBEDTLS_MPI_CHK( mbedtls_mpi_mod_mpi( &R.X, &R.X, &grp->N ) );
273
274 /*
275 * Step 8: check if v (that is, R.X) is equal to r
276 */
277 if( mbedtls_mpi_cmp_mpi( &R.X, r ) != 0 )
278 {
279 ret = MBEDTLS_ERR_ECP_VERIFY_FAILED;
280 goto cleanup;
281 }
282
283 cleanup:
284 mbedtls_ecp_point_free( &R );
285 mbedtls_mpi_free( &e ); mbedtls_mpi_free( &s_inv ); mbedtls_mpi_free( &u1 ); mbedtls_mpi_free( &u2 );
286
287 return( ret );
288 }
289 #endif /* MBEDTLS_ECDSA_VERIFY_ALT */
290
291 /*
292 * Convert a signature (given by context) to ASN.1
293 */
294 int ecdsa_signature_to_asn1( const mbedtls_mpi *r, const mbedtls_mpi *s,
295 unsigned char *sig, size_t *slen )
296 {
297 int ret;
298 unsigned char buf[MBEDTLS_ECDSA_MAX_LEN];
299 unsigned char *p = buf + sizeof( buf );
300 size_t len = 0;
301
302 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &p, buf, s ) );
303 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_mpi( &p, buf, r ) );
304
305 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_len( &p, buf, len ) );
306 MBEDTLS_ASN1_CHK_ADD( len, mbedtls_asn1_write_tag( &p, buf,
307 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) );
308
309 memcpy( sig, p, len );
310 *slen = len;
311
312 return( 0 );
313 }
314
315 /*
316 * Compute and write signature
317 */
318 int mbedtls_ecdsa_write_signature( mbedtls_ecdsa_context *ctx, mbedtls_md_type_t md_alg,
319 const unsigned char *hash, size_t hlen,
320 unsigned char *sig, size_t *slen,
321 int (*f_rng)(void *, unsigned char *, size_t),
322 void *p_rng )
323 {
324 int ret;
325 mbedtls_mpi r, s;
326
327 mbedtls_mpi_init( &r );
328 mbedtls_mpi_init( &s );
329
330 #if defined(MBEDTLS_ECDSA_DETERMINISTIC)
331 (void) f_rng;
332 (void) p_rng;
333
334 MBEDTLS_MPI_CHK( mbedtls_ecdsa_sign_det( &ctx->grp, &r, &s, &ctx->d,
335 hash, hlen, md_alg ) );
336 #else
337 (void) md_alg;
338
339 MBEDTLS_MPI_CHK( mbedtls_ecdsa_sign( &ctx->grp, &r, &s, &ctx->d,
340 hash, hlen, f_rng, p_rng ) );
341 #endif
342
343 MBEDTLS_MPI_CHK( ecdsa_signature_to_asn1( &r, &s, sig, slen ) );
344
345 cleanup:
346 mbedtls_mpi_free( &r );
347 mbedtls_mpi_free( &s );
348
349 return( ret );
350 }
351
352 #if ! defined(MBEDTLS_DEPRECATED_REMOVED) && \
353 defined(MBEDTLS_ECDSA_DETERMINISTIC)
354 int mbedtls_ecdsa_write_signature_det( mbedtls_ecdsa_context *ctx,
355 const unsigned char *hash, size_t hlen,
356 unsigned char *sig, size_t *slen,
357 mbedtls_md_type_t md_alg )
358 {
359 return( mbedtls_ecdsa_write_signature( ctx, md_alg, hash, hlen, sig, slen,
360 NULL, NULL ) );
361 }
362 #endif
363
364 /*
365 * Read and check signature
366 */
367 int mbedtls_ecdsa_read_signature( mbedtls_ecdsa_context *ctx,
368 const unsigned char *hash, size_t hlen,
369 const unsigned char *sig, size_t slen )
370 {
371 int ret;
372 unsigned char *p = (unsigned char *) sig;
373 const unsigned char *end = sig + slen;
374 size_t len;
375 mbedtls_mpi r, s;
376
377 mbedtls_mpi_init( &r );
378 mbedtls_mpi_init( &s );
379
380 if( ( ret = mbedtls_asn1_get_tag( &p, end, &len,
381 MBEDTLS_ASN1_CONSTRUCTED | MBEDTLS_ASN1_SEQUENCE ) ) != 0 )
382 {
383 ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
384 goto cleanup;
385 }
386
387 if( p + len != end )
388 {
389 ret = MBEDTLS_ERR_ECP_BAD_INPUT_DATA +
390 MBEDTLS_ERR_ASN1_LENGTH_MISMATCH;
391 goto cleanup;
392 }
393
394 if( ( ret = mbedtls_asn1_get_mpi( &p, end, &r ) ) != 0 ||
395 ( ret = mbedtls_asn1_get_mpi( &p, end, &s ) ) != 0 )
396 {
397 ret += MBEDTLS_ERR_ECP_BAD_INPUT_DATA;
398 goto cleanup;
399 }
400
401 if( ( ret = mbedtls_ecdsa_verify( &ctx->grp, hash, hlen,
402 &ctx->Q, &r, &s ) ) != 0 )
403 goto cleanup;
404
405 /* At this point we know that the buffer starts with a valid signature.
406 * Return 0 if the buffer just contains the signature, and a specific
407 * error code if the valid signature is followed by more data. */
408 if( p != end )
409 ret = MBEDTLS_ERR_ECP_SIG_LEN_MISMATCH;
410
411 cleanup:
412 mbedtls_mpi_free( &r );
413 mbedtls_mpi_free( &s );
414
415 return( ret );
416 }
417
418 #if !defined(MBEDTLS_ECDSA_GENKEY_ALT)
419 /*
420 * Generate key pair
421 */
422 int mbedtls_ecdsa_genkey( mbedtls_ecdsa_context *ctx, mbedtls_ecp_group_id gid,
423 int (*f_rng)(void *, unsigned char *, size_t), void *p_rng )
424 {
425 return( mbedtls_ecp_group_load( &ctx->grp, gid ) ||
426 mbedtls_ecp_gen_keypair( &ctx->grp, &ctx->d, &ctx->Q, f_rng, p_rng ) );
427 }
428 #endif /* MBEDTLS_ECDSA_GENKEY_ALT */
429
430 /*
431 * Set context from an mbedtls_ecp_keypair
432 */
433 int mbedtls_ecdsa_from_keypair( mbedtls_ecdsa_context *ctx, const mbedtls_ecp_keypair *key )
434 {
435 int ret;
436
437 if( ( ret = mbedtls_ecp_group_copy( &ctx->grp, &key->grp ) ) != 0 ||
438 ( ret = mbedtls_mpi_copy( &ctx->d, &key->d ) ) != 0 ||
439 ( ret = mbedtls_ecp_copy( &ctx->Q, &key->Q ) ) != 0 )
440 {
441 mbedtls_ecdsa_free( ctx );
442 }
443
444 return( ret );
445 }
446
447 /*
448 * Initialize context
449 */
450 void mbedtls_ecdsa_init( mbedtls_ecdsa_context *ctx )
451 {
452 mbedtls_ecp_keypair_init( ctx );
453 }
454
455 /*
456 * Free context
457 */
458 void mbedtls_ecdsa_free( mbedtls_ecdsa_context *ctx )
459 {
460 mbedtls_ecp_keypair_free( ctx );
461 }
462
463 #endif /* MBEDTLS_ECDSA_C */
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