mft.c revision 1.37
1/* $OpenBSD: mft.c,v 1.37 2021/09/08 16:37:20 claudio Exp $ */ 2/* 3 * Copyright (c) 2019 Kristaps Dzonsons <kristaps@bsd.lv> 4 * 5 * Permission to use, copy, modify, and distribute this software for any 6 * purpose with or without fee is hereby granted, provided that the above 7 * copyright notice and this permission notice appear in all copies. 8 * 9 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 10 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 11 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 12 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 13 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 14 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 15 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 16 */ 17 18#include <assert.h> 19#include <err.h> 20#include <limits.h> 21#include <stdarg.h> 22#include <stdint.h> 23#include <fcntl.h> 24#include <stdlib.h> 25#include <string.h> 26#include <unistd.h> 27 28#include <openssl/bn.h> 29#include <openssl/asn1.h> 30#include <openssl/sha.h> 31#include <openssl/x509.h> 32 33#include "extern.h" 34 35/* 36 * Parse results and data of the manifest file. 37 */ 38struct parse { 39 const char *fn; /* manifest file name */ 40 struct mft *res; /* result object */ 41}; 42 43static const char * 44gentime2str(const ASN1_GENERALIZEDTIME *time) 45{ 46 static char buf[64]; 47 BIO *mem; 48 49 if ((mem = BIO_new(BIO_s_mem())) == NULL) 50 cryptoerrx("BIO_new"); 51 if (!ASN1_GENERALIZEDTIME_print(mem, time)) 52 cryptoerrx("ASN1_GENERALIZEDTIME_print"); 53 if (BIO_gets(mem, buf, sizeof(buf)) < 0) 54 cryptoerrx("BIO_gets"); 55 56 BIO_free(mem); 57 return buf; 58} 59 60/* 61 * Convert an ASN1_GENERALIZEDTIME to a struct tm. 62 * Returns 1 on success, 0 on failure. 63 */ 64static int 65generalizedtime_to_tm(const ASN1_GENERALIZEDTIME *gtime, struct tm *tm) 66{ 67 const char *data; 68 size_t len; 69 70 data = ASN1_STRING_get0_data(gtime); 71 len = ASN1_STRING_length(gtime); 72 73 memset(tm, 0, sizeof(*tm)); 74 return ASN1_time_parse(data, len, tm, V_ASN1_GENERALIZEDTIME) == 75 V_ASN1_GENERALIZEDTIME; 76} 77 78/* 79 * Validate and verify the time validity of the mft. 80 * Returns 1 if all is good, 0 if mft is stale, any other case -1. 81 */ 82static int 83check_validity(const ASN1_GENERALIZEDTIME *from, 84 const ASN1_GENERALIZEDTIME *until, const char *fn) 85{ 86 time_t now = time(NULL); 87 struct tm tm_from, tm_until, tm_now; 88 89 if (gmtime_r(&now, &tm_now) == NULL) { 90 warnx("%s: could not get current time", fn); 91 return -1; 92 } 93 94 if (!generalizedtime_to_tm(from, &tm_from)) { 95 warnx("%s: embedded from time format invalid", fn); 96 return -1; 97 } 98 if (!generalizedtime_to_tm(until, &tm_until)) { 99 warnx("%s: embedded until time format invalid", fn); 100 return -1; 101 } 102 103 /* check that until is not before from */ 104 if (ASN1_time_tm_cmp(&tm_until, &tm_from) < 0) { 105 warnx("%s: bad update interval", fn); 106 return -1; 107 } 108 /* check that now is not before from */ 109 if (ASN1_time_tm_cmp(&tm_from, &tm_now) > 0) { 110 warnx("%s: mft not yet valid %s", fn, gentime2str(from)); 111 return -1; 112 } 113 /* check that now is not after until */ 114 if (ASN1_time_tm_cmp(&tm_until, &tm_now) < 0) { 115 warnx("%s: mft expired on %s", fn, gentime2str(until)); 116 return 0; 117 } 118 119 return 1; 120} 121 122/* 123 * Parse an individual "FileAndHash", RFC 6486, sec. 4.2. 124 * Return zero on failure, non-zero on success. 125 */ 126static int 127mft_parse_filehash(struct parse *p, const ASN1_OCTET_STRING *os) 128{ 129 ASN1_SEQUENCE_ANY *seq; 130 const ASN1_TYPE *file, *hash; 131 char *fn = NULL; 132 const unsigned char *d = os->data; 133 size_t dsz = os->length; 134 int rc = 0; 135 struct mftfile *fent; 136 137 if ((seq = d2i_ASN1_SEQUENCE_ANY(NULL, &d, dsz)) == NULL) { 138 cryptowarnx("%s: RFC 6486 section 4.2.1: FileAndHash: " 139 "failed ASN.1 sequence parse", p->fn); 140 goto out; 141 } else if (sk_ASN1_TYPE_num(seq) != 2) { 142 warnx("%s: RFC 6486 section 4.2.1: FileAndHash: " 143 "want 2 elements, have %d", p->fn, 144 sk_ASN1_TYPE_num(seq)); 145 goto out; 146 } 147 148 /* First is the filename itself. */ 149 150 file = sk_ASN1_TYPE_value(seq, 0); 151 if (file->type != V_ASN1_IA5STRING) { 152 warnx("%s: RFC 6486 section 4.2.1: FileAndHash: " 153 "want ASN.1 IA5 string, have %s (NID %d)", 154 p->fn, ASN1_tag2str(file->type), file->type); 155 goto out; 156 } 157 fn = strndup((const char *)file->value.ia5string->data, 158 file->value.ia5string->length); 159 if (fn == NULL) 160 err(1, NULL); 161 162 /* 163 * Make sure we're just a pathname and either an ROA or CER. 164 * I don't think that the RFC specifically mentions this, but 165 * it's in practical use and would really screw things up 166 * (arbitrary filenames) otherwise. 167 */ 168 169 if (strchr(fn, '/') != NULL) { 170 warnx("%s: path components disallowed in filename: %s", 171 p->fn, fn); 172 goto out; 173 } else if (strlen(fn) <= 4) { 174 warnx("%s: filename must be large enough for suffix part: %s", 175 p->fn, fn); 176 goto out; 177 } 178 179 /* Now hash value. */ 180 181 hash = sk_ASN1_TYPE_value(seq, 1); 182 if (hash->type != V_ASN1_BIT_STRING) { 183 warnx("%s: RFC 6486 section 4.2.1: FileAndHash: " 184 "want ASN.1 bit string, have %s (NID %d)", 185 p->fn, ASN1_tag2str(hash->type), hash->type); 186 goto out; 187 } 188 189 if (hash->value.bit_string->length != SHA256_DIGEST_LENGTH) { 190 warnx("%s: RFC 6486 section 4.2.1: hash: " 191 "invalid SHA256 length, have %d", 192 p->fn, hash->value.bit_string->length); 193 goto out; 194 } 195 196 /* Insert the filename and hash value. */ 197 fent = &p->res->files[p->res->filesz++]; 198 199 fent->file = fn; 200 fn = NULL; 201 memcpy(fent->hash, hash->value.bit_string->data, SHA256_DIGEST_LENGTH); 202 203 rc = 1; 204out: 205 free(fn); 206 sk_ASN1_TYPE_pop_free(seq, ASN1_TYPE_free); 207 return rc; 208} 209 210/* 211 * Parse the "FileAndHash" sequence, RFC 6486, sec. 4.2. 212 * Return zero on failure, non-zero on success. 213 */ 214static int 215mft_parse_flist(struct parse *p, const ASN1_OCTET_STRING *os) 216{ 217 ASN1_SEQUENCE_ANY *seq; 218 const ASN1_TYPE *t; 219 const unsigned char *d = os->data; 220 size_t dsz = os->length; 221 int i, rc = 0; 222 223 if ((seq = d2i_ASN1_SEQUENCE_ANY(NULL, &d, dsz)) == NULL) { 224 cryptowarnx("%s: RFC 6486 section 4.2: fileList: " 225 "failed ASN.1 sequence parse", p->fn); 226 goto out; 227 } 228 229 p->res->files = calloc(sk_ASN1_TYPE_num(seq), sizeof(struct mftfile)); 230 if (p->res->files == NULL) 231 err(1, NULL); 232 233 for (i = 0; i < sk_ASN1_TYPE_num(seq); i++) { 234 t = sk_ASN1_TYPE_value(seq, i); 235 if (t->type != V_ASN1_SEQUENCE) { 236 warnx("%s: RFC 6486 section 4.2: fileList: " 237 "want ASN.1 sequence, have %s (NID %d)", 238 p->fn, ASN1_tag2str(t->type), t->type); 239 goto out; 240 } else if (!mft_parse_filehash(p, t->value.octet_string)) 241 goto out; 242 } 243 244 rc = 1; 245out: 246 sk_ASN1_TYPE_pop_free(seq, ASN1_TYPE_free); 247 return rc; 248} 249 250/* 251 * Handle the eContent of the manifest object, RFC 6486 sec. 4.2. 252 * Returns <0 on failure, 0 on stale, >0 on success. 253 */ 254static int 255mft_parse_econtent(const unsigned char *d, size_t dsz, struct parse *p) 256{ 257 ASN1_SEQUENCE_ANY *seq; 258 const ASN1_TYPE *t; 259 const ASN1_GENERALIZEDTIME *from, *until; 260 long mft_version; 261 BIGNUM *mft_seqnum = NULL; 262 int i = 0, rc = -1; 263 264 if ((seq = d2i_ASN1_SEQUENCE_ANY(NULL, &d, dsz)) == NULL) { 265 cryptowarnx("%s: RFC 6486 section 4.2: Manifest: " 266 "failed ASN.1 sequence parse", p->fn); 267 goto out; 268 } 269 270 /* Test if the optional profile version field is present. */ 271 if (sk_ASN1_TYPE_num(seq) != 5 && 272 sk_ASN1_TYPE_num(seq) != 6) { 273 warnx("%s: RFC 6486 section 4.2: Manifest: " 274 "want 5 or 6 elements, have %d", p->fn, 275 sk_ASN1_TYPE_num(seq)); 276 goto out; 277 } 278 279 /* Parse the optional version field */ 280 if (sk_ASN1_TYPE_num(seq) == 6) { 281 t = sk_ASN1_TYPE_value(seq, i++); 282 d = t->value.asn1_string->data; 283 dsz = t->value.asn1_string->length; 284 285 if (cms_econtent_version(p->fn, &d, dsz, &mft_version) == -1) 286 goto out; 287 288 switch (mft_version) { 289 case 0: 290 warnx("%s: incorrect encoding for version 0", p->fn); 291 goto out; 292 default: 293 warnx("%s: version %ld not supported (yet)", p->fn, 294 mft_version); 295 goto out; 296 } 297 } 298 299 /* Now the manifest sequence number. */ 300 301 t = sk_ASN1_TYPE_value(seq, i++); 302 if (t->type != V_ASN1_INTEGER) { 303 warnx("%s: RFC 6486 section 4.2.1: manifestNumber: " 304 "want ASN.1 integer, have %s (NID %d)", 305 p->fn, ASN1_tag2str(t->type), t->type); 306 goto out; 307 } 308 309 mft_seqnum = ASN1_INTEGER_to_BN(t->value.integer, NULL); 310 if (mft_seqnum == NULL) { 311 warnx("%s: ASN1_INTEGER_to_BN error", p->fn); 312 goto out; 313 } 314 315 if (BN_is_negative(mft_seqnum)) { 316 warnx("%s: RFC 6486 section 4.2.1: manifestNumber: " 317 "want positive integer, have negative.", p->fn); 318 goto out; 319 } 320 321 if (BN_num_bytes(mft_seqnum) > 20) { 322 warnx("%s: RFC 6486 section 4.2.1: manifestNumber: " 323 "want 20 or less than octets, have more.", p->fn); 324 goto out; 325 } 326 327 p->res->seqnum = BN_bn2hex(mft_seqnum); 328 if (p->res->seqnum == NULL) { 329 warnx("%s: BN_bn2hex error", p->fn); 330 goto out; 331 } 332 333 /* 334 * Timestamps: this and next update time. 335 * Validate that the current date falls into this interval. 336 * This is required by section 4.4, (3). 337 * If we're after the given date, then the MFT is stale. 338 * This is made super complicated because it uses OpenSSL's 339 * ASN1_GENERALIZEDTIME instead of ASN1_TIME, which we could 340 * compare against the current time trivially. 341 */ 342 343 t = sk_ASN1_TYPE_value(seq, i++); 344 if (t->type != V_ASN1_GENERALIZEDTIME) { 345 warnx("%s: RFC 6486 section 4.2.1: thisUpdate: " 346 "want ASN.1 generalised time, have %s (NID %d)", 347 p->fn, ASN1_tag2str(t->type), t->type); 348 goto out; 349 } 350 from = t->value.generalizedtime; 351 352 t = sk_ASN1_TYPE_value(seq, i++); 353 if (t->type != V_ASN1_GENERALIZEDTIME) { 354 warnx("%s: RFC 6486 section 4.2.1: nextUpdate: " 355 "want ASN.1 generalised time, have %s (NID %d)", 356 p->fn, ASN1_tag2str(t->type), t->type); 357 goto out; 358 } 359 until = t->value.generalizedtime; 360 361 rc = check_validity(from, until, p->fn); 362 if (rc != 1) 363 goto out; 364 365 /* The mft is valid. Reset rc so later 'goto out' return failure. */ 366 rc = -1; 367 368 /* File list algorithm. */ 369 370 t = sk_ASN1_TYPE_value(seq, i++); 371 if (t->type != V_ASN1_OBJECT) { 372 warnx("%s: RFC 6486 section 4.2.1: fileHashAlg: " 373 "want ASN.1 object time, have %s (NID %d)", 374 p->fn, ASN1_tag2str(t->type), t->type); 375 goto out; 376 } else if (OBJ_obj2nid(t->value.object) != NID_sha256) { 377 warnx("%s: RFC 6486 section 4.2.1: fileHashAlg: " 378 "want SHA256 object, have %s (NID %d)", p->fn, 379 ASN1_tag2str(OBJ_obj2nid(t->value.object)), 380 OBJ_obj2nid(t->value.object)); 381 goto out; 382 } 383 384 /* Now the sequence. */ 385 386 t = sk_ASN1_TYPE_value(seq, i++); 387 if (t->type != V_ASN1_SEQUENCE) { 388 warnx("%s: RFC 6486 section 4.2.1: fileList: " 389 "want ASN.1 sequence, have %s (NID %d)", 390 p->fn, ASN1_tag2str(t->type), t->type); 391 goto out; 392 } else if (!mft_parse_flist(p, t->value.octet_string)) 393 goto out; 394 395 rc = 1; 396out: 397 sk_ASN1_TYPE_pop_free(seq, ASN1_TYPE_free); 398 BN_free(mft_seqnum); 399 return rc; 400} 401 402/* 403 * Parse the objects that have been published in the manifest. 404 * This conforms to RFC 6486. 405 * Note that if the MFT is stale, all referenced objects are stripped 406 * from the parsed content. 407 * The MFT content is otherwise returned. 408 */ 409struct mft * 410mft_parse(X509 **x509, const char *fn) 411{ 412 struct parse p; 413 int c, rc = 0; 414 size_t i, cmsz; 415 unsigned char *cms; 416 417 memset(&p, 0, sizeof(struct parse)); 418 p.fn = fn; 419 420 cms = cms_parse_validate(x509, fn, "1.2.840.113549.1.9.16.1.26", 421 &cmsz); 422 if (cms == NULL) 423 return NULL; 424 assert(*x509 != NULL); 425 426 if ((p.res = calloc(1, sizeof(struct mft))) == NULL) 427 err(1, NULL); 428 if ((p.res->file = strdup(fn)) == NULL) 429 err(1, NULL); 430 431 p.res->aia = x509_get_aia(*x509, fn); 432 p.res->aki = x509_get_aki(*x509, 0, fn); 433 p.res->ski = x509_get_ski(*x509, fn); 434 if (p.res->aia == NULL || p.res->aki == NULL || p.res->ski == NULL) { 435 warnx("%s: RFC 6487 section 4.8: " 436 "missing AIA, AKI or SKI X509 extension", fn); 437 goto out; 438 } 439 440 /* 441 * If we're stale, then remove all of the files that the MFT 442 * references as well as marking it as stale. 443 */ 444 445 if ((c = mft_parse_econtent(cms, cmsz, &p)) == 0) { 446 /* 447 * FIXME: it should suffice to just mark this as stale 448 * and have the logic around mft_read() simply ignore 449 * the contents of stale entries, just like it does for 450 * invalid ROAs or certificates. 451 */ 452 453 p.res->stale = 1; 454 if (p.res->files != NULL) 455 for (i = 0; i < p.res->filesz; i++) 456 free(p.res->files[i].file); 457 free(p.res->files); 458 p.res->filesz = 0; 459 p.res->files = NULL; 460 } else if (c == -1) 461 goto out; 462 463 rc = 1; 464out: 465 if (rc == 0) { 466 mft_free(p.res); 467 p.res = NULL; 468 X509_free(*x509); 469 *x509 = NULL; 470 } 471 free(cms); 472 return p.res; 473} 474 475/* 476 * Check all files and their hashes in a MFT structure. 477 * Return zero on failure, non-zero on success. 478 */ 479int 480mft_check(const char *fn, struct mft *p) 481{ 482 size_t i; 483 int rc = 1; 484 char *cp, *path = NULL; 485 486 /* Check hash of file now, but first build path for it */ 487 cp = strrchr(fn, '/'); 488 assert(cp != NULL); 489 assert(cp - fn < INT_MAX); 490 491 for (i = 0; i < p->filesz; i++) { 492 const struct mftfile *m = &p->files[i]; 493 if (asprintf(&path, "%.*s/%s", (int)(cp - fn), fn, 494 m->file) == -1) 495 err(1, NULL); 496 if (!valid_filehash(path, m->hash, sizeof(m->hash))) { 497 warnx("%s: bad message digest for %s", fn, m->file); 498 rc = 0; 499 } 500 free(path); 501 } 502 503 return rc; 504} 505 506/* 507 * Free an MFT pointer. 508 * Safe to call with NULL. 509 */ 510void 511mft_free(struct mft *p) 512{ 513 size_t i; 514 515 if (p == NULL) 516 return; 517 518 if (p->files != NULL) 519 for (i = 0; i < p->filesz; i++) 520 free(p->files[i].file); 521 522 free(p->aia); 523 free(p->aki); 524 free(p->ski); 525 free(p->file); 526 free(p->files); 527 free(p->seqnum); 528 free(p); 529} 530 531/* 532 * Serialise MFT parsed content into the given buffer. 533 * See mft_read() for the other side of the pipe. 534 */ 535void 536mft_buffer(struct ibuf *b, const struct mft *p) 537{ 538 size_t i; 539 540 io_simple_buffer(b, &p->stale, sizeof(int)); 541 io_str_buffer(b, p->file); 542 io_simple_buffer(b, &p->filesz, sizeof(size_t)); 543 544 for (i = 0; i < p->filesz; i++) { 545 io_str_buffer(b, p->files[i].file); 546 io_simple_buffer(b, p->files[i].hash, SHA256_DIGEST_LENGTH); 547 } 548 549 io_str_buffer(b, p->aia); 550 io_str_buffer(b, p->aki); 551 io_str_buffer(b, p->ski); 552} 553 554/* 555 * Read an MFT structure from the file descriptor. 556 * Result must be passed to mft_free(). 557 */ 558struct mft * 559mft_read(int fd) 560{ 561 struct mft *p = NULL; 562 size_t i; 563 564 if ((p = calloc(1, sizeof(struct mft))) == NULL) 565 err(1, NULL); 566 567 io_simple_read(fd, &p->stale, sizeof(int)); 568 io_str_read(fd, &p->file); 569 assert(p->file); 570 io_simple_read(fd, &p->filesz, sizeof(size_t)); 571 572 if ((p->files = calloc(p->filesz, sizeof(struct mftfile))) == NULL) 573 err(1, NULL); 574 575 for (i = 0; i < p->filesz; i++) { 576 io_str_read(fd, &p->files[i].file); 577 io_simple_read(fd, p->files[i].hash, SHA256_DIGEST_LENGTH); 578 } 579 580 io_str_read(fd, &p->aia); 581 io_str_read(fd, &p->aki); 582 io_str_read(fd, &p->ski); 583 assert(p->aia && p->aki && p->ski); 584 585 return p; 586} 587