1 /* X.509 certificate parser 2 * 3 * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved. 4 * Written by David Howells (dhowells@redhat.com) 5 * 6 * This program is free software; you can redistribute it and/or 7 * modify it under the terms of the GNU General Public Licence 8 * as published by the Free Software Foundation; either version 9 * 2 of the Licence, or (at your option) any later version. 10 */ 11 12 #define pr_fmt(fmt) "X.509: "fmt 13 #include <linux/kernel.h> 14 #include <linux/export.h> 15 #include <linux/slab.h> 16 #include <linux/err.h> 17 #include <linux/oid_registry.h> 18 #include <crypto/public_key.h> 19 #include "x509_parser.h" 20 #include "x509-asn1.h" 21 #include "x509_akid-asn1.h" 22 23 struct x509_parse_context { 24 struct x509_certificate *cert; /* Certificate being constructed */ 25 unsigned long data; /* Start of data */ 26 const void *cert_start; /* Start of cert content */ 27 const void *key; /* Key data */ 28 size_t key_size; /* Size of key data */ 29 enum OID last_oid; /* Last OID encountered */ 30 enum OID algo_oid; /* Algorithm OID */ 31 unsigned char nr_mpi; /* Number of MPIs stored */ 32 u8 o_size; /* Size of organizationName (O) */ 33 u8 cn_size; /* Size of commonName (CN) */ 34 u8 email_size; /* Size of emailAddress */ 35 u16 o_offset; /* Offset of organizationName (O) */ 36 u16 cn_offset; /* Offset of commonName (CN) */ 37 u16 email_offset; /* Offset of emailAddress */ 38 unsigned raw_akid_size; 39 const void *raw_akid; /* Raw authorityKeyId in ASN.1 */ 40 const void *akid_raw_issuer; /* Raw directoryName in authorityKeyId */ 41 unsigned akid_raw_issuer_size; 42 }; 43 44 /* 45 * Free an X.509 certificate 46 */ 47 void x509_free_certificate(struct x509_certificate *cert) 48 { 49 if (cert) { 50 public_key_destroy(cert->pub); 51 kfree(cert->issuer); 52 kfree(cert->subject); 53 kfree(cert->id); 54 kfree(cert->skid); 55 kfree(cert->akid_id); 56 kfree(cert->akid_skid); 57 kfree(cert->sig.digest); 58 kfree(cert->sig.s); 59 kfree(cert); 60 } 61 } 62 EXPORT_SYMBOL_GPL(x509_free_certificate); 63 64 /* 65 * Parse an X.509 certificate 66 */ 67 struct x509_certificate *x509_cert_parse(const void *data, size_t datalen) 68 { 69 struct x509_certificate *cert; 70 struct x509_parse_context *ctx; 71 struct asymmetric_key_id *kid; 72 long ret; 73 74 ret = -ENOMEM; 75 cert = kzalloc(sizeof(struct x509_certificate), GFP_KERNEL); 76 if (!cert) 77 goto error_no_cert; 78 cert->pub = kzalloc(sizeof(struct public_key), GFP_KERNEL); 79 if (!cert->pub) 80 goto error_no_ctx; 81 ctx = kzalloc(sizeof(struct x509_parse_context), GFP_KERNEL); 82 if (!ctx) 83 goto error_no_ctx; 84 85 ctx->cert = cert; 86 ctx->data = (unsigned long)data; 87 88 /* Attempt to decode the certificate */ 89 ret = asn1_ber_decoder(&x509_decoder, ctx, data, datalen); 90 if (ret < 0) 91 goto error_decode; 92 93 /* Decode the AuthorityKeyIdentifier */ 94 if (ctx->raw_akid) { 95 pr_devel("AKID: %u %*phN\n", 96 ctx->raw_akid_size, ctx->raw_akid_size, ctx->raw_akid); 97 ret = asn1_ber_decoder(&x509_akid_decoder, ctx, 98 ctx->raw_akid, ctx->raw_akid_size); 99 if (ret < 0) { 100 pr_warn("Couldn't decode AuthKeyIdentifier\n"); 101 goto error_decode; 102 } 103 } 104 105 cert->pub->key = kmemdup(ctx->key, ctx->key_size, GFP_KERNEL); 106 if (!cert->pub->key) 107 goto error_decode; 108 109 cert->pub->keylen = ctx->key_size; 110 111 /* Generate cert issuer + serial number key ID */ 112 kid = asymmetric_key_generate_id(cert->raw_serial, 113 cert->raw_serial_size, 114 cert->raw_issuer, 115 cert->raw_issuer_size); 116 if (IS_ERR(kid)) { 117 ret = PTR_ERR(kid); 118 goto error_decode; 119 } 120 cert->id = kid; 121 122 kfree(ctx); 123 return cert; 124 125 error_decode: 126 kfree(cert->pub->key); 127 kfree(ctx); 128 error_no_ctx: 129 x509_free_certificate(cert); 130 error_no_cert: 131 return ERR_PTR(ret); 132 } 133 EXPORT_SYMBOL_GPL(x509_cert_parse); 134 135 /* 136 * Note an OID when we find one for later processing when we know how 137 * to interpret it. 138 */ 139 int x509_note_OID(void *context, size_t hdrlen, 140 unsigned char tag, 141 const void *value, size_t vlen) 142 { 143 struct x509_parse_context *ctx = context; 144 145 ctx->last_oid = look_up_OID(value, vlen); 146 if (ctx->last_oid == OID__NR) { 147 char buffer[50]; 148 sprint_oid(value, vlen, buffer, sizeof(buffer)); 149 pr_debug("Unknown OID: [%lu] %s\n", 150 (unsigned long)value - ctx->data, buffer); 151 } 152 return 0; 153 } 154 155 /* 156 * Save the position of the TBS data so that we can check the signature over it 157 * later. 158 */ 159 int x509_note_tbs_certificate(void *context, size_t hdrlen, 160 unsigned char tag, 161 const void *value, size_t vlen) 162 { 163 struct x509_parse_context *ctx = context; 164 165 pr_debug("x509_note_tbs_certificate(,%zu,%02x,%ld,%zu)!\n", 166 hdrlen, tag, (unsigned long)value - ctx->data, vlen); 167 168 ctx->cert->tbs = value - hdrlen; 169 ctx->cert->tbs_size = vlen + hdrlen; 170 return 0; 171 } 172 173 /* 174 * Record the public key algorithm 175 */ 176 int x509_note_pkey_algo(void *context, size_t hdrlen, 177 unsigned char tag, 178 const void *value, size_t vlen) 179 { 180 struct x509_parse_context *ctx = context; 181 182 pr_debug("PubKey Algo: %u\n", ctx->last_oid); 183 184 switch (ctx->last_oid) { 185 case OID_md2WithRSAEncryption: 186 case OID_md3WithRSAEncryption: 187 default: 188 return -ENOPKG; /* Unsupported combination */ 189 190 case OID_md4WithRSAEncryption: 191 ctx->cert->sig.hash_algo = "md4"; 192 ctx->cert->sig.pkey_algo = "rsa"; 193 break; 194 195 case OID_sha1WithRSAEncryption: 196 ctx->cert->sig.hash_algo = "sha1"; 197 ctx->cert->sig.pkey_algo = "rsa"; 198 break; 199 200 case OID_sha256WithRSAEncryption: 201 ctx->cert->sig.hash_algo = "sha256"; 202 ctx->cert->sig.pkey_algo = "rsa"; 203 break; 204 205 case OID_sha384WithRSAEncryption: 206 ctx->cert->sig.hash_algo = "sha384"; 207 ctx->cert->sig.pkey_algo = "rsa"; 208 break; 209 210 case OID_sha512WithRSAEncryption: 211 ctx->cert->sig.hash_algo = "sha512"; 212 ctx->cert->sig.pkey_algo = "rsa"; 213 break; 214 215 case OID_sha224WithRSAEncryption: 216 ctx->cert->sig.hash_algo = "sha224"; 217 ctx->cert->sig.pkey_algo = "rsa"; 218 break; 219 } 220 221 ctx->algo_oid = ctx->last_oid; 222 return 0; 223 } 224 225 /* 226 * Note the whereabouts and type of the signature. 227 */ 228 int x509_note_signature(void *context, size_t hdrlen, 229 unsigned char tag, 230 const void *value, size_t vlen) 231 { 232 struct x509_parse_context *ctx = context; 233 234 pr_debug("Signature type: %u size %zu\n", ctx->last_oid, vlen); 235 236 if (ctx->last_oid != ctx->algo_oid) { 237 pr_warn("Got cert with pkey (%u) and sig (%u) algorithm OIDs\n", 238 ctx->algo_oid, ctx->last_oid); 239 return -EINVAL; 240 } 241 242 ctx->cert->raw_sig = value; 243 ctx->cert->raw_sig_size = vlen; 244 return 0; 245 } 246 247 /* 248 * Note the certificate serial number 249 */ 250 int x509_note_serial(void *context, size_t hdrlen, 251 unsigned char tag, 252 const void *value, size_t vlen) 253 { 254 struct x509_parse_context *ctx = context; 255 ctx->cert->raw_serial = value; 256 ctx->cert->raw_serial_size = vlen; 257 return 0; 258 } 259 260 /* 261 * Note some of the name segments from which we'll fabricate a name. 262 */ 263 int x509_extract_name_segment(void *context, size_t hdrlen, 264 unsigned char tag, 265 const void *value, size_t vlen) 266 { 267 struct x509_parse_context *ctx = context; 268 269 switch (ctx->last_oid) { 270 case OID_commonName: 271 ctx->cn_size = vlen; 272 ctx->cn_offset = (unsigned long)value - ctx->data; 273 break; 274 case OID_organizationName: 275 ctx->o_size = vlen; 276 ctx->o_offset = (unsigned long)value - ctx->data; 277 break; 278 case OID_email_address: 279 ctx->email_size = vlen; 280 ctx->email_offset = (unsigned long)value - ctx->data; 281 break; 282 default: 283 break; 284 } 285 286 return 0; 287 } 288 289 /* 290 * Fabricate and save the issuer and subject names 291 */ 292 static int x509_fabricate_name(struct x509_parse_context *ctx, size_t hdrlen, 293 unsigned char tag, 294 char **_name, size_t vlen) 295 { 296 const void *name, *data = (const void *)ctx->data; 297 size_t namesize; 298 char *buffer; 299 300 if (*_name) 301 return -EINVAL; 302 303 /* Empty name string if no material */ 304 if (!ctx->cn_size && !ctx->o_size && !ctx->email_size) { 305 buffer = kmalloc(1, GFP_KERNEL); 306 if (!buffer) 307 return -ENOMEM; 308 buffer[0] = 0; 309 goto done; 310 } 311 312 if (ctx->cn_size && ctx->o_size) { 313 /* Consider combining O and CN, but use only the CN if it is 314 * prefixed by the O, or a significant portion thereof. 315 */ 316 namesize = ctx->cn_size; 317 name = data + ctx->cn_offset; 318 if (ctx->cn_size >= ctx->o_size && 319 memcmp(data + ctx->cn_offset, data + ctx->o_offset, 320 ctx->o_size) == 0) 321 goto single_component; 322 if (ctx->cn_size >= 7 && 323 ctx->o_size >= 7 && 324 memcmp(data + ctx->cn_offset, data + ctx->o_offset, 7) == 0) 325 goto single_component; 326 327 buffer = kmalloc(ctx->o_size + 2 + ctx->cn_size + 1, 328 GFP_KERNEL); 329 if (!buffer) 330 return -ENOMEM; 331 332 memcpy(buffer, 333 data + ctx->o_offset, ctx->o_size); 334 buffer[ctx->o_size + 0] = ':'; 335 buffer[ctx->o_size + 1] = ' '; 336 memcpy(buffer + ctx->o_size + 2, 337 data + ctx->cn_offset, ctx->cn_size); 338 buffer[ctx->o_size + 2 + ctx->cn_size] = 0; 339 goto done; 340 341 } else if (ctx->cn_size) { 342 namesize = ctx->cn_size; 343 name = data + ctx->cn_offset; 344 } else if (ctx->o_size) { 345 namesize = ctx->o_size; 346 name = data + ctx->o_offset; 347 } else { 348 namesize = ctx->email_size; 349 name = data + ctx->email_offset; 350 } 351 352 single_component: 353 buffer = kmalloc(namesize + 1, GFP_KERNEL); 354 if (!buffer) 355 return -ENOMEM; 356 memcpy(buffer, name, namesize); 357 buffer[namesize] = 0; 358 359 done: 360 *_name = buffer; 361 ctx->cn_size = 0; 362 ctx->o_size = 0; 363 ctx->email_size = 0; 364 return 0; 365 } 366 367 int x509_note_issuer(void *context, size_t hdrlen, 368 unsigned char tag, 369 const void *value, size_t vlen) 370 { 371 struct x509_parse_context *ctx = context; 372 ctx->cert->raw_issuer = value; 373 ctx->cert->raw_issuer_size = vlen; 374 return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->issuer, vlen); 375 } 376 377 int x509_note_subject(void *context, size_t hdrlen, 378 unsigned char tag, 379 const void *value, size_t vlen) 380 { 381 struct x509_parse_context *ctx = context; 382 ctx->cert->raw_subject = value; 383 ctx->cert->raw_subject_size = vlen; 384 return x509_fabricate_name(ctx, hdrlen, tag, &ctx->cert->subject, vlen); 385 } 386 387 /* 388 * Extract the data for the public key algorithm 389 */ 390 int x509_extract_key_data(void *context, size_t hdrlen, 391 unsigned char tag, 392 const void *value, size_t vlen) 393 { 394 struct x509_parse_context *ctx = context; 395 396 if (ctx->last_oid != OID_rsaEncryption) 397 return -ENOPKG; 398 399 ctx->cert->pub->pkey_algo = "rsa"; 400 401 /* Discard the BIT STRING metadata */ 402 ctx->key = value + 1; 403 ctx->key_size = vlen - 1; 404 return 0; 405 } 406 407 /* The keyIdentifier in AuthorityKeyIdentifier SEQUENCE is tag(CONT,PRIM,0) */ 408 #define SEQ_TAG_KEYID (ASN1_CONT << 6) 409 410 /* 411 * Process certificate extensions that are used to qualify the certificate. 412 */ 413 int x509_process_extension(void *context, size_t hdrlen, 414 unsigned char tag, 415 const void *value, size_t vlen) 416 { 417 struct x509_parse_context *ctx = context; 418 struct asymmetric_key_id *kid; 419 const unsigned char *v = value; 420 421 pr_debug("Extension: %u\n", ctx->last_oid); 422 423 if (ctx->last_oid == OID_subjectKeyIdentifier) { 424 /* Get hold of the key fingerprint */ 425 if (ctx->cert->skid || vlen < 3) 426 return -EBADMSG; 427 if (v[0] != ASN1_OTS || v[1] != vlen - 2) 428 return -EBADMSG; 429 v += 2; 430 vlen -= 2; 431 432 ctx->cert->raw_skid_size = vlen; 433 ctx->cert->raw_skid = v; 434 kid = asymmetric_key_generate_id(v, vlen, "", 0); 435 if (IS_ERR(kid)) 436 return PTR_ERR(kid); 437 ctx->cert->skid = kid; 438 pr_debug("subjkeyid %*phN\n", kid->len, kid->data); 439 return 0; 440 } 441 442 if (ctx->last_oid == OID_authorityKeyIdentifier) { 443 /* Get hold of the CA key fingerprint */ 444 ctx->raw_akid = v; 445 ctx->raw_akid_size = vlen; 446 return 0; 447 } 448 449 return 0; 450 } 451 452 /** 453 * x509_decode_time - Decode an X.509 time ASN.1 object 454 * @_t: The time to fill in 455 * @hdrlen: The length of the object header 456 * @tag: The object tag 457 * @value: The object value 458 * @vlen: The size of the object value 459 * 460 * Decode an ASN.1 universal time or generalised time field into a struct the 461 * kernel can handle and check it for validity. The time is decoded thus: 462 * 463 * [RFC5280 §4.1.2.5] 464 * CAs conforming to this profile MUST always encode certificate validity 465 * dates through the year 2049 as UTCTime; certificate validity dates in 466 * 2050 or later MUST be encoded as GeneralizedTime. Conforming 467 * applications MUST be able to process validity dates that are encoded in 468 * either UTCTime or GeneralizedTime. 469 */ 470 int x509_decode_time(time64_t *_t, size_t hdrlen, 471 unsigned char tag, 472 const unsigned char *value, size_t vlen) 473 { 474 static const unsigned char month_lengths[] = { 31, 28, 31, 30, 31, 30, 475 31, 31, 30, 31, 30, 31 }; 476 const unsigned char *p = value; 477 unsigned year, mon, day, hour, min, sec, mon_len; 478 479 #define dec2bin(X) ({ unsigned char x = (X) - '0'; if (x > 9) goto invalid_time; x; }) 480 #define DD2bin(P) ({ unsigned x = dec2bin(P[0]) * 10 + dec2bin(P[1]); P += 2; x; }) 481 482 if (tag == ASN1_UNITIM) { 483 /* UTCTime: YYMMDDHHMMSSZ */ 484 if (vlen != 13) 485 goto unsupported_time; 486 year = DD2bin(p); 487 if (year >= 50) 488 year += 1900; 489 else 490 year += 2000; 491 } else if (tag == ASN1_GENTIM) { 492 /* GenTime: YYYYMMDDHHMMSSZ */ 493 if (vlen != 15) 494 goto unsupported_time; 495 year = DD2bin(p) * 100 + DD2bin(p); 496 if (year >= 1950 && year <= 2049) 497 goto invalid_time; 498 } else { 499 goto unsupported_time; 500 } 501 502 mon = DD2bin(p); 503 day = DD2bin(p); 504 hour = DD2bin(p); 505 min = DD2bin(p); 506 sec = DD2bin(p); 507 508 if (*p != 'Z') 509 goto unsupported_time; 510 511 if (year < 1970 || 512 mon < 1 || mon > 12) 513 goto invalid_time; 514 515 mon_len = month_lengths[mon - 1]; 516 if (mon == 2) { 517 if (year % 4 == 0) { 518 mon_len = 29; 519 if (year % 100 == 0) { 520 mon_len = 28; 521 if (year % 400 == 0) 522 mon_len = 29; 523 } 524 } 525 } 526 527 if (day < 1 || day > mon_len || 528 hour > 24 || /* ISO 8601 permits 24:00:00 as midnight tomorrow */ 529 min > 59 || 530 sec > 60) /* ISO 8601 permits leap seconds [X.680 46.3] */ 531 goto invalid_time; 532 533 *_t = mktime64(year, mon, day, hour, min, sec); 534 return 0; 535 536 unsupported_time: 537 pr_debug("Got unsupported time [tag %02x]: '%*phN'\n", 538 tag, (int)vlen, value); 539 return -EBADMSG; 540 invalid_time: 541 pr_debug("Got invalid time [tag %02x]: '%*phN'\n", 542 tag, (int)vlen, value); 543 return -EBADMSG; 544 } 545 EXPORT_SYMBOL_GPL(x509_decode_time); 546 547 int x509_note_not_before(void *context, size_t hdrlen, 548 unsigned char tag, 549 const void *value, size_t vlen) 550 { 551 struct x509_parse_context *ctx = context; 552 return x509_decode_time(&ctx->cert->valid_from, hdrlen, tag, value, vlen); 553 } 554 555 int x509_note_not_after(void *context, size_t hdrlen, 556 unsigned char tag, 557 const void *value, size_t vlen) 558 { 559 struct x509_parse_context *ctx = context; 560 return x509_decode_time(&ctx->cert->valid_to, hdrlen, tag, value, vlen); 561 } 562 563 /* 564 * Note a key identifier-based AuthorityKeyIdentifier 565 */ 566 int x509_akid_note_kid(void *context, size_t hdrlen, 567 unsigned char tag, 568 const void *value, size_t vlen) 569 { 570 struct x509_parse_context *ctx = context; 571 struct asymmetric_key_id *kid; 572 573 pr_debug("AKID: keyid: %*phN\n", (int)vlen, value); 574 575 if (ctx->cert->akid_skid) 576 return 0; 577 578 kid = asymmetric_key_generate_id(value, vlen, "", 0); 579 if (IS_ERR(kid)) 580 return PTR_ERR(kid); 581 pr_debug("authkeyid %*phN\n", kid->len, kid->data); 582 ctx->cert->akid_skid = kid; 583 return 0; 584 } 585 586 /* 587 * Note a directoryName in an AuthorityKeyIdentifier 588 */ 589 int x509_akid_note_name(void *context, size_t hdrlen, 590 unsigned char tag, 591 const void *value, size_t vlen) 592 { 593 struct x509_parse_context *ctx = context; 594 595 pr_debug("AKID: name: %*phN\n", (int)vlen, value); 596 597 ctx->akid_raw_issuer = value; 598 ctx->akid_raw_issuer_size = vlen; 599 return 0; 600 } 601 602 /* 603 * Note a serial number in an AuthorityKeyIdentifier 604 */ 605 int x509_akid_note_serial(void *context, size_t hdrlen, 606 unsigned char tag, 607 const void *value, size_t vlen) 608 { 609 struct x509_parse_context *ctx = context; 610 struct asymmetric_key_id *kid; 611 612 pr_debug("AKID: serial: %*phN\n", (int)vlen, value); 613 614 if (!ctx->akid_raw_issuer || ctx->cert->akid_id) 615 return 0; 616 617 kid = asymmetric_key_generate_id(value, 618 vlen, 619 ctx->akid_raw_issuer, 620 ctx->akid_raw_issuer_size); 621 if (IS_ERR(kid)) 622 return PTR_ERR(kid); 623 624 pr_debug("authkeyid %*phN\n", kid->len, kid->data); 625 ctx->cert->akid_id = kid; 626 return 0; 627 } 628