Juan Castillo | a57a4d5 | 2015-04-02 15:44:20 +0100 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (c) 2015, ARM Limited and Contributors. All rights reserved. |
| 3 | * |
| 4 | * Redistribution and use in source and binary forms, with or without |
| 5 | * modification, are permitted provided that the following conditions are met: |
| 6 | * |
| 7 | * Redistributions of source code must retain the above copyright notice, this |
| 8 | * list of conditions and the following disclaimer. |
| 9 | * |
| 10 | * Redistributions in binary form must reproduce the above copyright notice, |
| 11 | * this list of conditions and the following disclaimer in the documentation |
| 12 | * and/or other materials provided with the distribution. |
| 13 | * |
| 14 | * Neither the name of ARM nor the names of its contributors may be used |
| 15 | * to endorse or promote products derived from this software without specific |
| 16 | * prior written permission. |
| 17 | * |
| 18 | * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" |
| 19 | * AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE |
| 20 | * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE |
| 21 | * ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE |
| 22 | * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR |
| 23 | * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF |
| 24 | * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS |
| 25 | * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN |
| 26 | * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| 27 | * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE |
| 28 | * POSSIBILITY OF SUCH DAMAGE. |
| 29 | */ |
| 30 | |
| 31 | /* |
| 32 | * X509 parser based on PolarSSL |
| 33 | * |
| 34 | * This module implements functions to check the integrity of a X509v3 |
| 35 | * certificate ASN.1 structure and extract authentication parameters from the |
| 36 | * extensions field, such as an image hash or a public key. |
| 37 | */ |
| 38 | |
| 39 | #include <assert.h> |
| 40 | #include <img_parser_mod.h> |
| 41 | #include <mbedtls_common.h> |
| 42 | #include <stddef.h> |
| 43 | #include <stdint.h> |
| 44 | #include <string.h> |
| 45 | |
| 46 | /* mbedTLS headers */ |
| 47 | #include <polarssl/asn1.h> |
| 48 | #include <polarssl/oid.h> |
| 49 | #include <polarssl/platform.h> |
| 50 | |
| 51 | /* Maximum OID string length ("a.b.c.d.e.f ...") */ |
| 52 | #define MAX_OID_STR_LEN 64 |
| 53 | |
| 54 | #define LIB_NAME "mbedTLS X509v3" |
| 55 | |
| 56 | /* Temporary variables to speed up the authentication parameters search. These |
| 57 | * variables are assigned once during the integrity check and used any time an |
| 58 | * authentication parameter is requested, so we do not have to parse the image |
| 59 | * again */ |
| 60 | static asn1_buf tbs; |
| 61 | static asn1_buf v3_ext; |
| 62 | static asn1_buf pk; |
| 63 | static asn1_buf sig_alg; |
| 64 | static asn1_buf signature; |
| 65 | |
| 66 | /* |
| 67 | * Get X509v3 extension |
| 68 | * |
| 69 | * Global variable 'v3_ext' must point to the extensions region |
| 70 | * in the certificate. No need to check for errors since the image has passed |
| 71 | * the integrity check. |
| 72 | */ |
| 73 | static int get_ext(const char *oid, void **ext, unsigned int *ext_len) |
| 74 | { |
| 75 | int oid_len; |
| 76 | size_t len; |
| 77 | unsigned char *end_ext_data, *end_ext_octet; |
| 78 | unsigned char *p; |
| 79 | const unsigned char *end; |
| 80 | char oid_str[MAX_OID_STR_LEN]; |
| 81 | asn1_buf extn_oid; |
| 82 | int is_critical; |
| 83 | |
| 84 | assert(oid != NULL); |
| 85 | |
| 86 | p = v3_ext.p; |
| 87 | end = v3_ext.p + v3_ext.len; |
| 88 | |
| 89 | asn1_get_tag(&p, end, &len, ASN1_CONSTRUCTED | ASN1_SEQUENCE); |
| 90 | |
| 91 | while (p < end) { |
| 92 | memset(&extn_oid, 0x0, sizeof(extn_oid)); |
| 93 | is_critical = 0; /* DEFAULT FALSE */ |
| 94 | |
| 95 | asn1_get_tag(&p, end, &len, ASN1_CONSTRUCTED | ASN1_SEQUENCE); |
| 96 | end_ext_data = p + len; |
| 97 | |
| 98 | /* Get extension ID */ |
| 99 | extn_oid.tag = *p; |
| 100 | asn1_get_tag(&p, end, &extn_oid.len, ASN1_OID); |
| 101 | extn_oid.p = p; |
| 102 | p += extn_oid.len; |
| 103 | |
| 104 | /* Get optional critical */ |
| 105 | asn1_get_bool(&p, end_ext_data, &is_critical); |
| 106 | |
| 107 | /* Extension data */ |
| 108 | asn1_get_tag(&p, end_ext_data, &len, ASN1_OCTET_STRING); |
| 109 | end_ext_octet = p + len; |
| 110 | |
| 111 | /* Detect requested extension */ |
| 112 | oid_len = oid_get_numeric_string(oid_str, |
| 113 | MAX_OID_STR_LEN, &extn_oid); |
| 114 | if (oid_len == POLARSSL_ERR_OID_BUF_TOO_SMALL) { |
| 115 | return IMG_PARSER_ERR; |
| 116 | } |
| 117 | if ((oid_len == strlen(oid_str)) && !strcmp(oid, oid_str)) { |
| 118 | *ext = (void *)p; |
| 119 | *ext_len = (unsigned int)len; |
| 120 | return IMG_PARSER_OK; |
| 121 | } |
| 122 | |
| 123 | /* Next */ |
| 124 | p = end_ext_octet; |
| 125 | } |
| 126 | |
| 127 | return IMG_PARSER_ERR_NOT_FOUND; |
| 128 | } |
| 129 | |
| 130 | |
| 131 | /* |
| 132 | * Check the integrity of the certificate ASN.1 structure. |
| 133 | * Extract the relevant data that will be used later during authentication. |
| 134 | */ |
| 135 | static int cert_parse(void *img, unsigned int img_len) |
| 136 | { |
| 137 | int ret, is_critical; |
| 138 | size_t len; |
| 139 | unsigned char *p, *end, *crt_end; |
| 140 | asn1_buf sig_alg1, sig_alg2; |
| 141 | |
| 142 | p = (unsigned char *)img; |
| 143 | len = img_len; |
| 144 | end = p + len; |
| 145 | |
| 146 | /* |
| 147 | * Certificate ::= SEQUENCE { |
| 148 | * tbsCertificate TBSCertificate, |
| 149 | * signatureAlgorithm AlgorithmIdentifier, |
| 150 | * signatureValue BIT STRING } |
| 151 | */ |
| 152 | ret = asn1_get_tag(&p, end, &len, ASN1_CONSTRUCTED | ASN1_SEQUENCE); |
| 153 | if (ret != 0) { |
| 154 | return IMG_PARSER_ERR_FORMAT; |
| 155 | } |
| 156 | |
| 157 | if (len > (size_t)(end - p)) { |
| 158 | return IMG_PARSER_ERR_FORMAT; |
| 159 | } |
| 160 | crt_end = p + len; |
| 161 | |
| 162 | /* |
| 163 | * TBSCertificate ::= SEQUENCE { |
| 164 | */ |
| 165 | tbs.p = p; |
| 166 | ret = asn1_get_tag(&p, end, &len, ASN1_CONSTRUCTED | ASN1_SEQUENCE); |
| 167 | if (ret != 0) { |
| 168 | return IMG_PARSER_ERR_FORMAT; |
| 169 | } |
| 170 | end = p + len; |
| 171 | tbs.len = end - tbs.p; |
| 172 | |
| 173 | /* |
| 174 | * Version ::= INTEGER { v1(0), v2(1), v3(2) } |
| 175 | */ |
| 176 | ret = asn1_get_tag(&p, end, &len, |
| 177 | ASN1_CONTEXT_SPECIFIC | ASN1_CONSTRUCTED | 0); |
| 178 | if (ret != 0) { |
| 179 | return IMG_PARSER_ERR_FORMAT; |
| 180 | } |
| 181 | p += len; |
| 182 | |
| 183 | /* |
| 184 | * CertificateSerialNumber ::= INTEGER |
| 185 | */ |
| 186 | ret = asn1_get_tag(&p, end, &len, ASN1_INTEGER); |
| 187 | if (ret != 0) { |
| 188 | return IMG_PARSER_ERR_FORMAT; |
| 189 | } |
| 190 | p += len; |
| 191 | |
| 192 | /* |
| 193 | * signature AlgorithmIdentifier |
| 194 | */ |
| 195 | sig_alg1.p = p; |
| 196 | ret = asn1_get_tag(&p, end, &len, ASN1_CONSTRUCTED | ASN1_SEQUENCE); |
| 197 | if (ret != 0) { |
| 198 | return IMG_PARSER_ERR_FORMAT; |
| 199 | } |
| 200 | if ((end - p) < 1) { |
| 201 | return IMG_PARSER_ERR_FORMAT; |
| 202 | } |
| 203 | sig_alg1.len = (p + len) - sig_alg1.p; |
| 204 | p += len; |
| 205 | |
| 206 | /* |
| 207 | * issuer Name |
| 208 | */ |
| 209 | ret = asn1_get_tag(&p, end, &len, ASN1_CONSTRUCTED | ASN1_SEQUENCE); |
| 210 | if (ret != 0) { |
| 211 | return IMG_PARSER_ERR_FORMAT; |
| 212 | } |
| 213 | p += len; |
| 214 | |
| 215 | /* |
| 216 | * Validity ::= SEQUENCE { |
| 217 | * notBefore Time, |
| 218 | * notAfter Time } |
| 219 | * |
| 220 | */ |
| 221 | ret = asn1_get_tag(&p, end, &len, ASN1_CONSTRUCTED | ASN1_SEQUENCE); |
| 222 | if (ret != 0) { |
| 223 | return IMG_PARSER_ERR_FORMAT; |
| 224 | } |
| 225 | p += len; |
| 226 | |
| 227 | /* |
| 228 | * subject Name |
| 229 | */ |
| 230 | ret = asn1_get_tag(&p, end, &len, ASN1_CONSTRUCTED | ASN1_SEQUENCE); |
| 231 | if (ret != 0) { |
| 232 | return IMG_PARSER_ERR_FORMAT; |
| 233 | } |
| 234 | p += len; |
| 235 | |
| 236 | /* |
| 237 | * SubjectPublicKeyInfo |
| 238 | */ |
| 239 | pk.p = p; |
| 240 | ret = asn1_get_tag(&p, end, &len, ASN1_CONSTRUCTED | ASN1_SEQUENCE); |
| 241 | if (ret != 0) { |
| 242 | return IMG_PARSER_ERR_FORMAT; |
| 243 | } |
| 244 | pk.len = (p + len) - pk.p; |
| 245 | p += len; |
| 246 | |
| 247 | /* |
| 248 | * issuerUniqueID [1] IMPLICIT UniqueIdentifier OPTIONAL, |
| 249 | */ |
| 250 | ret = asn1_get_tag(&p, end, &len, |
| 251 | ASN1_CONTEXT_SPECIFIC | ASN1_CONSTRUCTED | 1); |
| 252 | if (ret != 0) { |
| 253 | if (ret != POLARSSL_ERR_ASN1_UNEXPECTED_TAG) { |
| 254 | return IMG_PARSER_ERR_FORMAT; |
| 255 | } |
| 256 | } else { |
| 257 | p += len; |
| 258 | } |
| 259 | |
| 260 | /* |
| 261 | * subjectUniqueID [2] IMPLICIT UniqueIdentifier OPTIONAL, |
| 262 | */ |
| 263 | ret = asn1_get_tag(&p, end, &len, |
| 264 | ASN1_CONTEXT_SPECIFIC | ASN1_CONSTRUCTED | 2); |
| 265 | if (ret != 0) { |
| 266 | if (ret != POLARSSL_ERR_ASN1_UNEXPECTED_TAG) { |
| 267 | return IMG_PARSER_ERR_FORMAT; |
| 268 | } |
| 269 | } else { |
| 270 | p += len; |
| 271 | } |
| 272 | |
| 273 | /* |
| 274 | * extensions [3] EXPLICIT Extensions OPTIONAL |
| 275 | */ |
| 276 | ret = asn1_get_tag(&p, end, &len, |
| 277 | ASN1_CONTEXT_SPECIFIC | ASN1_CONSTRUCTED | 3); |
| 278 | if (ret != 0) { |
| 279 | return IMG_PARSER_ERR_FORMAT; |
| 280 | } |
| 281 | |
| 282 | /* |
| 283 | * Extensions ::= SEQUENCE SIZE (1..MAX) OF Extension |
| 284 | */ |
| 285 | v3_ext.p = p; |
| 286 | ret = asn1_get_tag(&p, end, &len, ASN1_CONSTRUCTED | ASN1_SEQUENCE); |
| 287 | if (ret != 0) { |
| 288 | return IMG_PARSER_ERR_FORMAT; |
| 289 | } |
| 290 | v3_ext.len = (p + len) - v3_ext.p; |
| 291 | |
| 292 | /* |
| 293 | * Check extensions integrity |
| 294 | */ |
| 295 | while (p < end) { |
| 296 | ret = asn1_get_tag(&p, end, &len, |
| 297 | ASN1_CONSTRUCTED | ASN1_SEQUENCE); |
| 298 | if (ret != 0) { |
| 299 | return IMG_PARSER_ERR_FORMAT; |
| 300 | } |
| 301 | |
| 302 | /* Get extension ID */ |
| 303 | ret = asn1_get_tag(&p, end, &len, ASN1_OID); |
| 304 | if (ret != 0) { |
| 305 | return IMG_PARSER_ERR_FORMAT; |
| 306 | } |
| 307 | p += len; |
| 308 | |
| 309 | /* Get optional critical */ |
| 310 | ret = asn1_get_bool(&p, end, &is_critical); |
| 311 | if ((ret != 0) && (ret != POLARSSL_ERR_ASN1_UNEXPECTED_TAG)) { |
| 312 | return IMG_PARSER_ERR_FORMAT; |
| 313 | } |
| 314 | |
| 315 | /* Data should be octet string type */ |
| 316 | ret = asn1_get_tag(&p, end, &len, ASN1_OCTET_STRING); |
| 317 | if (ret != 0) { |
| 318 | return IMG_PARSER_ERR_FORMAT; |
| 319 | } |
| 320 | p += len; |
| 321 | } |
| 322 | |
| 323 | if (p != end) { |
| 324 | return IMG_PARSER_ERR_FORMAT; |
| 325 | } |
| 326 | |
| 327 | end = crt_end; |
| 328 | |
| 329 | /* |
| 330 | * } |
| 331 | * -- end of TBSCertificate |
| 332 | * |
| 333 | * signatureAlgorithm AlgorithmIdentifier |
| 334 | */ |
| 335 | sig_alg2.p = p; |
| 336 | ret = asn1_get_tag(&p, end, &len, ASN1_CONSTRUCTED | ASN1_SEQUENCE); |
| 337 | if (ret != 0) { |
| 338 | return IMG_PARSER_ERR_FORMAT; |
| 339 | } |
| 340 | if ((end - p) < 1) { |
| 341 | return IMG_PARSER_ERR_FORMAT; |
| 342 | } |
| 343 | sig_alg2.len = (p + len) - sig_alg2.p; |
| 344 | p += len; |
| 345 | |
| 346 | /* Compare both signature algorithms */ |
| 347 | if (sig_alg1.len != sig_alg2.len) { |
| 348 | return IMG_PARSER_ERR_FORMAT; |
| 349 | } |
| 350 | if (0 != memcmp(sig_alg1.p, sig_alg2.p, sig_alg1.len)) { |
| 351 | return IMG_PARSER_ERR_FORMAT; |
| 352 | } |
| 353 | memcpy(&sig_alg, &sig_alg1, sizeof(sig_alg)); |
| 354 | |
| 355 | /* |
| 356 | * signatureValue BIT STRING |
| 357 | */ |
| 358 | signature.p = p; |
| 359 | ret = asn1_get_tag(&p, end, &len, ASN1_BIT_STRING); |
| 360 | if (ret != 0) { |
| 361 | return IMG_PARSER_ERR_FORMAT; |
| 362 | } |
| 363 | signature.len = (p + len) - signature.p; |
| 364 | p += len; |
| 365 | |
| 366 | /* Check certificate length */ |
| 367 | if (p != end) { |
| 368 | return IMG_PARSER_ERR_FORMAT; |
| 369 | } |
| 370 | |
| 371 | return IMG_PARSER_OK; |
| 372 | } |
| 373 | |
| 374 | |
| 375 | /* Exported functions */ |
| 376 | |
| 377 | static void init(void) |
| 378 | { |
| 379 | mbedtls_init(); |
| 380 | } |
| 381 | |
| 382 | static int check_integrity(void *img, unsigned int img_len) |
| 383 | { |
| 384 | return cert_parse(img, img_len); |
| 385 | } |
| 386 | |
| 387 | /* |
| 388 | * Extract an authentication parameter from an X509v3 certificate |
| 389 | */ |
| 390 | static int get_auth_param(const auth_param_type_desc_t *type_desc, |
| 391 | void *img, unsigned int img_len, |
| 392 | void **param, unsigned int *param_len) |
| 393 | { |
| 394 | int rc = IMG_PARSER_OK; |
| 395 | |
| 396 | /* We do not use img because the check_integrity function has already |
| 397 | * extracted the relevant data (v3_ext, pk, sig_alg, etc) */ |
| 398 | |
| 399 | switch (type_desc->type) { |
| 400 | case AUTH_PARAM_RAW_DATA: |
| 401 | /* Data to be signed */ |
| 402 | *param = (void *)tbs.p; |
| 403 | *param_len = (unsigned int)tbs.len; |
| 404 | break; |
| 405 | case AUTH_PARAM_HASH: |
| 406 | /* All these parameters are included as X509v3 extensions */ |
| 407 | rc = get_ext(type_desc->cookie, param, param_len); |
| 408 | break; |
| 409 | case AUTH_PARAM_PUB_KEY: |
| 410 | if (type_desc->cookie != 0) { |
| 411 | /* Get public key from extension */ |
| 412 | rc = get_ext(type_desc->cookie, param, param_len); |
| 413 | } else { |
| 414 | /* Get the subject public key */ |
| 415 | *param = (void *)pk.p; |
| 416 | *param_len = (unsigned int)pk.len; |
| 417 | } |
| 418 | break; |
| 419 | case AUTH_PARAM_SIG_ALG: |
| 420 | /* Get the certificate signature algorithm */ |
| 421 | *param = (void *)sig_alg.p; |
| 422 | *param_len = (unsigned int)sig_alg.len; |
| 423 | break; |
| 424 | case AUTH_PARAM_SIG: |
| 425 | /* Get the certificate signature */ |
| 426 | *param = (void *)signature.p; |
| 427 | *param_len = (unsigned int)signature.len; |
| 428 | break; |
| 429 | default: |
| 430 | rc = IMG_PARSER_ERR_NOT_FOUND; |
| 431 | break; |
| 432 | } |
| 433 | |
| 434 | return rc; |
| 435 | } |
| 436 | |
| 437 | REGISTER_IMG_PARSER_LIB(IMG_CERT, LIB_NAME, init, \ |
| 438 | check_integrity, get_auth_param); |