1 /*
2 * PSA RSA layer on top of Mbed TLS crypto
3 */
4 /*
5 * Copyright The Mbed TLS Contributors
6 * SPDX-License-Identifier: Apache-2.0 OR GPL-2.0-or-later
7 */
8
9 #include "common.h"
10
11 #if defined(MBEDTLS_PSA_CRYPTO_C)
12
13 #include <psa/crypto.h>
14 #include "psa_crypto_core.h"
15 #include "psa_crypto_random_impl.h"
16 #include "psa_crypto_rsa.h"
17 #include "psa_crypto_hash.h"
18
19 #include <stdlib.h>
20 #include <string.h>
21 #include "mbedtls/platform.h"
22
23 #include <mbedtls/rsa.h>
24 #include <mbedtls/error.h>
25 #include <mbedtls/pk.h>
26 #include <mbedtls/pk_internal.h>
27
28 #if defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PKCS1V15_CRYPT) || \
29 defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_OAEP) || \
30 defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PKCS1V15_SIGN) || \
31 defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PSS) || \
32 defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_KEY_PAIR) || \
33 defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_PUBLIC_KEY)
34
35 /* Mbed TLS doesn't support non-byte-aligned key sizes (i.e. key sizes
36 * that are not a multiple of 8) well. For example, there is only
37 * mbedtls_rsa_get_len(), which returns a number of bytes, and no
38 * way to return the exact bit size of a key.
39 * To keep things simple, reject non-byte-aligned key sizes. */
psa_check_rsa_key_byte_aligned(const mbedtls_rsa_context * rsa)40 static psa_status_t psa_check_rsa_key_byte_aligned(
41 const mbedtls_rsa_context *rsa)
42 {
43 mbedtls_mpi n;
44 psa_status_t status;
45 mbedtls_mpi_init(&n);
46 status = mbedtls_to_psa_error(
47 mbedtls_rsa_export(rsa, &n, NULL, NULL, NULL, NULL));
48 if (status == PSA_SUCCESS) {
49 if (mbedtls_mpi_bitlen(&n) % 8 != 0) {
50 status = PSA_ERROR_NOT_SUPPORTED;
51 }
52 }
53 mbedtls_mpi_free(&n);
54 return status;
55 }
56
mbedtls_psa_rsa_load_representation(psa_key_type_t type,const uint8_t * data,size_t data_length,mbedtls_rsa_context ** p_rsa)57 psa_status_t mbedtls_psa_rsa_load_representation(
58 psa_key_type_t type, const uint8_t *data, size_t data_length,
59 mbedtls_rsa_context **p_rsa)
60 {
61 psa_status_t status;
62 mbedtls_pk_context ctx;
63 size_t bits;
64 mbedtls_pk_init(&ctx);
65
66 /* Parse the data. */
67 if (PSA_KEY_TYPE_IS_KEY_PAIR(type)) {
68 status = mbedtls_to_psa_error(
69 mbedtls_pk_parse_key(&ctx, data, data_length, NULL, 0));
70 } else {
71 status = mbedtls_to_psa_error(
72 mbedtls_pk_parse_public_key(&ctx, data, data_length));
73 }
74 if (status != PSA_SUCCESS) {
75 goto exit;
76 }
77
78 /* We have something that the pkparse module recognizes. If it is a
79 * valid RSA key, store it. */
80 if (mbedtls_pk_get_type(&ctx) != MBEDTLS_PK_RSA) {
81 status = PSA_ERROR_INVALID_ARGUMENT;
82 goto exit;
83 }
84
85 /* The size of an RSA key doesn't have to be a multiple of 8. Mbed TLS
86 * supports non-byte-aligned key sizes, but not well. For example,
87 * mbedtls_rsa_get_len() returns the key size in bytes, not in bits. */
88 bits = PSA_BYTES_TO_BITS(mbedtls_rsa_get_len(mbedtls_pk_rsa(ctx)));
89 if (bits > PSA_VENDOR_RSA_MAX_KEY_BITS) {
90 status = PSA_ERROR_NOT_SUPPORTED;
91 goto exit;
92 }
93 status = psa_check_rsa_key_byte_aligned(mbedtls_pk_rsa(ctx));
94 if (status != PSA_SUCCESS) {
95 goto exit;
96 }
97
98 /* Copy out the pointer to the RSA context, and reset the PK context
99 * such that pk_free doesn't free the RSA context we just grabbed. */
100 *p_rsa = mbedtls_pk_rsa(ctx);
101 ctx.pk_info = NULL;
102
103 exit:
104 mbedtls_pk_free(&ctx);
105 return status;
106 }
107 #endif /* defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PKCS1V15_CRYPT) ||
108 * defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_OAEP) ||
109 * defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PKCS1V15_SIGN) ||
110 * defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PSS) ||
111 * defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_KEY_PAIR) ||
112 * defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_PUBLIC_KEY) */
113
114 #if defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_KEY_PAIR) || \
115 defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_PUBLIC_KEY)
116
mbedtls_psa_rsa_import_key(const psa_key_attributes_t * attributes,const uint8_t * data,size_t data_length,uint8_t * key_buffer,size_t key_buffer_size,size_t * key_buffer_length,size_t * bits)117 psa_status_t mbedtls_psa_rsa_import_key(
118 const psa_key_attributes_t *attributes,
119 const uint8_t *data, size_t data_length,
120 uint8_t *key_buffer, size_t key_buffer_size,
121 size_t *key_buffer_length, size_t *bits)
122 {
123 psa_status_t status;
124 mbedtls_rsa_context *rsa = NULL;
125
126 /* Parse input */
127 status = mbedtls_psa_rsa_load_representation(attributes->core.type,
128 data,
129 data_length,
130 &rsa);
131 if (status != PSA_SUCCESS) {
132 goto exit;
133 }
134
135 *bits = (psa_key_bits_t) PSA_BYTES_TO_BITS(mbedtls_rsa_get_len(rsa));
136
137 /* Re-export the data to PSA export format, such that we can store export
138 * representation in the key slot. Export representation in case of RSA is
139 * the smallest representation that's allowed as input, so a straight-up
140 * allocation of the same size as the input buffer will be large enough. */
141 status = mbedtls_psa_rsa_export_key(attributes->core.type,
142 rsa,
143 key_buffer,
144 key_buffer_size,
145 key_buffer_length);
146 exit:
147 /* Always free the RSA object */
148 mbedtls_rsa_free(rsa);
149 mbedtls_free(rsa);
150
151 return status;
152 }
153
mbedtls_psa_rsa_export_key(psa_key_type_t type,mbedtls_rsa_context * rsa,uint8_t * data,size_t data_size,size_t * data_length)154 psa_status_t mbedtls_psa_rsa_export_key(psa_key_type_t type,
155 mbedtls_rsa_context *rsa,
156 uint8_t *data,
157 size_t data_size,
158 size_t *data_length)
159 {
160 #if defined(MBEDTLS_PK_WRITE_C)
161 int ret;
162 mbedtls_pk_context pk;
163 uint8_t *pos = data + data_size;
164
165 mbedtls_pk_init(&pk);
166 pk.pk_info = &mbedtls_rsa_info;
167 pk.pk_ctx = rsa;
168
169 /* PSA Crypto API defines the format of an RSA key as a DER-encoded
170 * representation of the non-encrypted PKCS#1 RSAPrivateKey for a
171 * private key and of the RFC3279 RSAPublicKey for a public key. */
172 if (PSA_KEY_TYPE_IS_KEY_PAIR(type)) {
173 ret = mbedtls_pk_write_key_der(&pk, data, data_size);
174 } else {
175 ret = mbedtls_pk_write_pubkey(&pos, data, &pk);
176 }
177
178 if (ret < 0) {
179 /* Clean up in case pk_write failed halfway through. */
180 memset(data, 0, data_size);
181 return mbedtls_to_psa_error(ret);
182 }
183
184 /* The mbedtls_pk_xxx functions write to the end of the buffer.
185 * Move the data to the beginning and erase remaining data
186 * at the original location. */
187 if (2 * (size_t) ret <= data_size) {
188 memcpy(data, data + data_size - ret, ret);
189 memset(data + data_size - ret, 0, ret);
190 } else if ((size_t) ret < data_size) {
191 memmove(data, data + data_size - ret, ret);
192 memset(data + ret, 0, data_size - ret);
193 }
194
195 *data_length = ret;
196 return PSA_SUCCESS;
197 #else
198 (void) type;
199 (void) rsa;
200 (void) data;
201 (void) data_size;
202 (void) data_length;
203 return PSA_ERROR_NOT_SUPPORTED;
204 #endif /* MBEDTLS_PK_WRITE_C */
205 }
206
mbedtls_psa_rsa_export_public_key(const psa_key_attributes_t * attributes,const uint8_t * key_buffer,size_t key_buffer_size,uint8_t * data,size_t data_size,size_t * data_length)207 psa_status_t mbedtls_psa_rsa_export_public_key(
208 const psa_key_attributes_t *attributes,
209 const uint8_t *key_buffer, size_t key_buffer_size,
210 uint8_t *data, size_t data_size, size_t *data_length)
211 {
212 psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
213 mbedtls_rsa_context *rsa = NULL;
214
215 status = mbedtls_psa_rsa_load_representation(
216 attributes->core.type, key_buffer, key_buffer_size, &rsa);
217 if (status != PSA_SUCCESS) {
218 return status;
219 }
220
221 status = mbedtls_psa_rsa_export_key(PSA_KEY_TYPE_RSA_PUBLIC_KEY,
222 rsa,
223 data,
224 data_size,
225 data_length);
226
227 mbedtls_rsa_free(rsa);
228 mbedtls_free(rsa);
229
230 return status;
231 }
232 #endif /* defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_KEY_PAIR) ||
233 * defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_PUBLIC_KEY) */
234
235 #if defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_KEY_PAIR) && \
236 defined(MBEDTLS_GENPRIME)
psa_rsa_read_exponent(const uint8_t * domain_parameters,size_t domain_parameters_size,int * exponent)237 static psa_status_t psa_rsa_read_exponent(const uint8_t *domain_parameters,
238 size_t domain_parameters_size,
239 int *exponent)
240 {
241 size_t i;
242 uint32_t acc = 0;
243
244 if (domain_parameters_size == 0) {
245 *exponent = 65537;
246 return PSA_SUCCESS;
247 }
248
249 /* Mbed TLS encodes the public exponent as an int. For simplicity, only
250 * support values that fit in a 32-bit integer, which is larger than
251 * int on just about every platform anyway. */
252 if (domain_parameters_size > sizeof(acc)) {
253 return PSA_ERROR_NOT_SUPPORTED;
254 }
255 for (i = 0; i < domain_parameters_size; i++) {
256 acc = (acc << 8) | domain_parameters[i];
257 }
258 if (acc > INT_MAX) {
259 return PSA_ERROR_NOT_SUPPORTED;
260 }
261 *exponent = acc;
262 return PSA_SUCCESS;
263 }
264
mbedtls_psa_rsa_generate_key(const psa_key_attributes_t * attributes,uint8_t * key_buffer,size_t key_buffer_size,size_t * key_buffer_length)265 psa_status_t mbedtls_psa_rsa_generate_key(
266 const psa_key_attributes_t *attributes,
267 uint8_t *key_buffer, size_t key_buffer_size, size_t *key_buffer_length)
268 {
269 psa_status_t status;
270 mbedtls_rsa_context rsa;
271 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
272 int exponent;
273
274 status = psa_rsa_read_exponent(attributes->domain_parameters,
275 attributes->domain_parameters_size,
276 &exponent);
277 if (status != PSA_SUCCESS) {
278 return status;
279 }
280
281 mbedtls_rsa_init(&rsa, MBEDTLS_RSA_PKCS_V15, MBEDTLS_MD_NONE);
282 ret = mbedtls_rsa_gen_key(&rsa,
283 mbedtls_psa_get_random,
284 MBEDTLS_PSA_RANDOM_STATE,
285 (unsigned int) attributes->core.bits,
286 exponent);
287 if (ret != 0) {
288 return mbedtls_to_psa_error(ret);
289 }
290
291 status = mbedtls_psa_rsa_export_key(attributes->core.type,
292 &rsa, key_buffer, key_buffer_size,
293 key_buffer_length);
294 mbedtls_rsa_free(&rsa);
295
296 return status;
297 }
298 #endif /* defined(MBEDTLS_PSA_BUILTIN_KEY_TYPE_RSA_KEY_PAIR)
299 * defined(MBEDTLS_GENPRIME) */
300
301 /****************************************************************/
302 /* Sign/verify hashes */
303 /****************************************************************/
304
305 #if defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PKCS1V15_SIGN) || \
306 defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PSS)
307
308 /* Decode the hash algorithm from alg and store the mbedtls encoding in
309 * md_alg. Verify that the hash length is acceptable. */
psa_rsa_decode_md_type(psa_algorithm_t alg,size_t hash_length,mbedtls_md_type_t * md_alg)310 static psa_status_t psa_rsa_decode_md_type(psa_algorithm_t alg,
311 size_t hash_length,
312 mbedtls_md_type_t *md_alg)
313 {
314 psa_algorithm_t hash_alg = PSA_ALG_SIGN_GET_HASH(alg);
315 const mbedtls_md_info_t *md_info = mbedtls_md_info_from_psa(hash_alg);
316 *md_alg = mbedtls_md_get_type(md_info);
317
318 /* The Mbed TLS RSA module uses an unsigned int for hash length
319 * parameters. Validate that it fits so that we don't risk an
320 * overflow later. */
321 #if SIZE_MAX > UINT_MAX
322 if (hash_length > UINT_MAX) {
323 return PSA_ERROR_INVALID_ARGUMENT;
324 }
325 #endif
326
327 /* For signatures using a hash, the hash length must be correct. */
328 if (alg != PSA_ALG_RSA_PKCS1V15_SIGN_RAW) {
329 if (md_info == NULL) {
330 return PSA_ERROR_NOT_SUPPORTED;
331 }
332 if (mbedtls_md_get_size(md_info) != hash_length) {
333 return PSA_ERROR_INVALID_ARGUMENT;
334 }
335 }
336
337 return PSA_SUCCESS;
338 }
339
mbedtls_psa_rsa_sign_hash(const psa_key_attributes_t * attributes,const uint8_t * key_buffer,size_t key_buffer_size,psa_algorithm_t alg,const uint8_t * hash,size_t hash_length,uint8_t * signature,size_t signature_size,size_t * signature_length)340 psa_status_t mbedtls_psa_rsa_sign_hash(
341 const psa_key_attributes_t *attributes,
342 const uint8_t *key_buffer, size_t key_buffer_size,
343 psa_algorithm_t alg, const uint8_t *hash, size_t hash_length,
344 uint8_t *signature, size_t signature_size, size_t *signature_length)
345 {
346 psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
347 mbedtls_rsa_context *rsa = NULL;
348 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
349 mbedtls_md_type_t md_alg;
350
351 status = mbedtls_psa_rsa_load_representation(attributes->core.type,
352 key_buffer,
353 key_buffer_size,
354 &rsa);
355 if (status != PSA_SUCCESS) {
356 return status;
357 }
358
359 status = psa_rsa_decode_md_type(alg, hash_length, &md_alg);
360 if (status != PSA_SUCCESS) {
361 goto exit;
362 }
363
364 if (signature_size < mbedtls_rsa_get_len(rsa)) {
365 status = PSA_ERROR_BUFFER_TOO_SMALL;
366 goto exit;
367 }
368
369 #if defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PKCS1V15_SIGN)
370 if (PSA_ALG_IS_RSA_PKCS1V15_SIGN(alg)) {
371 mbedtls_rsa_set_padding(rsa, MBEDTLS_RSA_PKCS_V15,
372 MBEDTLS_MD_NONE);
373 ret = mbedtls_rsa_pkcs1_sign(rsa,
374 mbedtls_psa_get_random,
375 MBEDTLS_PSA_RANDOM_STATE,
376 MBEDTLS_RSA_PRIVATE,
377 md_alg,
378 (unsigned int) hash_length,
379 hash,
380 signature);
381 } else
382 #endif /* MBEDTLS_PSA_BUILTIN_ALG_RSA_PKCS1V15_SIGN */
383 #if defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PSS)
384 if (PSA_ALG_IS_RSA_PSS(alg)) {
385 mbedtls_rsa_set_padding(rsa, MBEDTLS_RSA_PKCS_V21, md_alg);
386 ret = mbedtls_rsa_rsassa_pss_sign(rsa,
387 mbedtls_psa_get_random,
388 MBEDTLS_PSA_RANDOM_STATE,
389 MBEDTLS_RSA_PRIVATE,
390 MBEDTLS_MD_NONE,
391 (unsigned int) hash_length,
392 hash,
393 signature);
394 } else
395 #endif /* MBEDTLS_PSA_BUILTIN_ALG_RSA_PSS */
396 {
397 status = PSA_ERROR_INVALID_ARGUMENT;
398 goto exit;
399 }
400
401 if (ret == 0) {
402 *signature_length = mbedtls_rsa_get_len(rsa);
403 }
404 status = mbedtls_to_psa_error(ret);
405
406 exit:
407 mbedtls_rsa_free(rsa);
408 mbedtls_free(rsa);
409
410 return status;
411 }
412
413 #if defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PSS)
rsa_pss_expected_salt_len(psa_algorithm_t alg,const mbedtls_rsa_context * rsa,size_t hash_length)414 static int rsa_pss_expected_salt_len(psa_algorithm_t alg,
415 const mbedtls_rsa_context *rsa,
416 size_t hash_length)
417 {
418 if (PSA_ALG_IS_RSA_PSS_ANY_SALT(alg)) {
419 return MBEDTLS_RSA_SALT_LEN_ANY;
420 }
421 /* Otherwise: standard salt length, i.e. largest possible salt length
422 * up to the hash length. */
423 int klen = (int) mbedtls_rsa_get_len(rsa); // known to fit
424 int hlen = (int) hash_length; // known to fit
425 int room = klen - 2 - hlen;
426 if (room < 0) {
427 return 0; // there is no valid signature in this case anyway
428 } else if (room > hlen) {
429 return hlen;
430 } else {
431 return room;
432 }
433 }
434 #endif /* MBEDTLS_PSA_BUILTIN_ALG_RSA_PSS */
435
mbedtls_psa_rsa_verify_hash(const psa_key_attributes_t * attributes,const uint8_t * key_buffer,size_t key_buffer_size,psa_algorithm_t alg,const uint8_t * hash,size_t hash_length,const uint8_t * signature,size_t signature_length)436 psa_status_t mbedtls_psa_rsa_verify_hash(
437 const psa_key_attributes_t *attributes,
438 const uint8_t *key_buffer, size_t key_buffer_size,
439 psa_algorithm_t alg, const uint8_t *hash, size_t hash_length,
440 const uint8_t *signature, size_t signature_length)
441 {
442 psa_status_t status = PSA_ERROR_CORRUPTION_DETECTED;
443 mbedtls_rsa_context *rsa = NULL;
444 int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED;
445 mbedtls_md_type_t md_alg;
446
447 status = mbedtls_psa_rsa_load_representation(attributes->core.type,
448 key_buffer,
449 key_buffer_size,
450 &rsa);
451 if (status != PSA_SUCCESS) {
452 goto exit;
453 }
454
455 status = psa_rsa_decode_md_type(alg, hash_length, &md_alg);
456 if (status != PSA_SUCCESS) {
457 goto exit;
458 }
459
460 if (signature_length != mbedtls_rsa_get_len(rsa)) {
461 status = PSA_ERROR_INVALID_SIGNATURE;
462 goto exit;
463 }
464
465 #if defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PKCS1V15_SIGN)
466 if (PSA_ALG_IS_RSA_PKCS1V15_SIGN(alg)) {
467 mbedtls_rsa_set_padding(rsa, MBEDTLS_RSA_PKCS_V15,
468 MBEDTLS_MD_NONE);
469 ret = mbedtls_rsa_pkcs1_verify(rsa,
470 mbedtls_psa_get_random,
471 MBEDTLS_PSA_RANDOM_STATE,
472 MBEDTLS_RSA_PUBLIC,
473 md_alg,
474 (unsigned int) hash_length,
475 hash,
476 signature);
477 } else
478 #endif /* MBEDTLS_PSA_BUILTIN_ALG_RSA_PKCS1V15_SIGN */
479 #if defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PSS)
480 if (PSA_ALG_IS_RSA_PSS(alg)) {
481 int slen = rsa_pss_expected_salt_len(alg, rsa, hash_length);
482 mbedtls_rsa_set_padding(rsa, MBEDTLS_RSA_PKCS_V21, md_alg);
483 ret = mbedtls_rsa_rsassa_pss_verify_ext(rsa,
484 mbedtls_psa_get_random,
485 MBEDTLS_PSA_RANDOM_STATE,
486 MBEDTLS_RSA_PUBLIC,
487 md_alg,
488 (unsigned int) hash_length,
489 hash,
490 md_alg,
491 slen,
492 signature);
493 } else
494 #endif /* MBEDTLS_PSA_BUILTIN_ALG_RSA_PSS */
495 {
496 status = PSA_ERROR_INVALID_ARGUMENT;
497 goto exit;
498 }
499
500 /* Mbed TLS distinguishes "invalid padding" from "valid padding but
501 * the rest of the signature is invalid". This has little use in
502 * practice and PSA doesn't report this distinction. */
503 status = (ret == MBEDTLS_ERR_RSA_INVALID_PADDING) ?
504 PSA_ERROR_INVALID_SIGNATURE :
505 mbedtls_to_psa_error(ret);
506
507 exit:
508 mbedtls_rsa_free(rsa);
509 mbedtls_free(rsa);
510
511 return status;
512 }
513
514 #endif /* defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PKCS1V15_SIGN) ||
515 * defined(MBEDTLS_PSA_BUILTIN_ALG_RSA_PSS) */
516
517 #endif /* MBEDTLS_PSA_CRYPTO_C */
518