1 /* 2 * Copyright (c) 2012 Damien Miller <djm@mindrot.org> 3 * 4 * Permission to use, copy, modify, and distribute this software for any 5 * purpose with or without fee is hereby granted, provided that the above 6 * copyright notice and this permission notice appear in all copies. 7 * 8 * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES 9 * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF 10 * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR 11 * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES 12 * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN 13 * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF 14 * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. 15 */ 16 17 /* $OpenBSD: krl.c,v 1.10 2013/02/19 02:12:47 dtucker Exp $ */ 18 19 #include "includes.h" 20 21 #include <sys/types.h> 22 #include <sys/param.h> 23 #include <openbsd-compat/sys-tree.h> 24 #include <openbsd-compat/sys-queue.h> 25 26 #include <errno.h> 27 #include <fcntl.h> 28 #include <limits.h> 29 #include <string.h> 30 #include <time.h> 31 #include <unistd.h> 32 33 #include "buffer.h" 34 #include "key.h" 35 #include "authfile.h" 36 #include "misc.h" 37 #include "log.h" 38 #include "xmalloc.h" 39 40 #include "krl.h" 41 42 /* #define DEBUG_KRL */ 43 #ifdef DEBUG_KRL 44 # define KRL_DBG(x) debug3 x 45 #else 46 # define KRL_DBG(x) 47 #endif 48 49 /* 50 * Trees of revoked serial numbers, key IDs and keys. This allows 51 * quick searching, querying and producing lists in canonical order. 52 */ 53 54 /* Tree of serial numbers. XXX make smarter: really need a real sparse bitmap */ 55 struct revoked_serial { 56 u_int64_t lo, hi; 57 RB_ENTRY(revoked_serial) tree_entry; 58 }; 59 static int serial_cmp(struct revoked_serial *a, struct revoked_serial *b); 60 RB_HEAD(revoked_serial_tree, revoked_serial); 61 RB_GENERATE_STATIC(revoked_serial_tree, revoked_serial, tree_entry, serial_cmp); 62 63 /* Tree of key IDs */ 64 struct revoked_key_id { 65 char *key_id; 66 RB_ENTRY(revoked_key_id) tree_entry; 67 }; 68 static int key_id_cmp(struct revoked_key_id *a, struct revoked_key_id *b); 69 RB_HEAD(revoked_key_id_tree, revoked_key_id); 70 RB_GENERATE_STATIC(revoked_key_id_tree, revoked_key_id, tree_entry, key_id_cmp); 71 72 /* Tree of blobs (used for keys and fingerprints) */ 73 struct revoked_blob { 74 u_char *blob; 75 u_int len; 76 RB_ENTRY(revoked_blob) tree_entry; 77 }; 78 static int blob_cmp(struct revoked_blob *a, struct revoked_blob *b); 79 RB_HEAD(revoked_blob_tree, revoked_blob); 80 RB_GENERATE_STATIC(revoked_blob_tree, revoked_blob, tree_entry, blob_cmp); 81 82 /* Tracks revoked certs for a single CA */ 83 struct revoked_certs { 84 Key *ca_key; 85 struct revoked_serial_tree revoked_serials; 86 struct revoked_key_id_tree revoked_key_ids; 87 TAILQ_ENTRY(revoked_certs) entry; 88 }; 89 TAILQ_HEAD(revoked_certs_list, revoked_certs); 90 91 struct ssh_krl { 92 u_int64_t krl_version; 93 u_int64_t generated_date; 94 u_int64_t flags; 95 char *comment; 96 struct revoked_blob_tree revoked_keys; 97 struct revoked_blob_tree revoked_sha1s; 98 struct revoked_certs_list revoked_certs; 99 }; 100 101 /* Return equal if a and b overlap */ 102 static int 103 serial_cmp(struct revoked_serial *a, struct revoked_serial *b) 104 { 105 if (a->hi >= b->lo && a->lo <= b->hi) 106 return 0; 107 return a->lo < b->lo ? -1 : 1; 108 } 109 110 static int 111 key_id_cmp(struct revoked_key_id *a, struct revoked_key_id *b) 112 { 113 return strcmp(a->key_id, b->key_id); 114 } 115 116 static int 117 blob_cmp(struct revoked_blob *a, struct revoked_blob *b) 118 { 119 int r; 120 121 if (a->len != b->len) { 122 if ((r = memcmp(a->blob, b->blob, MIN(a->len, b->len))) != 0) 123 return r; 124 return a->len > b->len ? 1 : -1; 125 } else 126 return memcmp(a->blob, b->blob, a->len); 127 } 128 129 struct ssh_krl * 130 ssh_krl_init(void) 131 { 132 struct ssh_krl *krl; 133 134 if ((krl = calloc(1, sizeof(*krl))) == NULL) 135 return NULL; 136 RB_INIT(&krl->revoked_keys); 137 RB_INIT(&krl->revoked_sha1s); 138 TAILQ_INIT(&krl->revoked_certs); 139 return krl; 140 } 141 142 static void 143 revoked_certs_free(struct revoked_certs *rc) 144 { 145 struct revoked_serial *rs, *trs; 146 struct revoked_key_id *rki, *trki; 147 148 RB_FOREACH_SAFE(rs, revoked_serial_tree, &rc->revoked_serials, trs) { 149 RB_REMOVE(revoked_serial_tree, &rc->revoked_serials, rs); 150 free(rs); 151 } 152 RB_FOREACH_SAFE(rki, revoked_key_id_tree, &rc->revoked_key_ids, trki) { 153 RB_REMOVE(revoked_key_id_tree, &rc->revoked_key_ids, rki); 154 free(rki->key_id); 155 free(rki); 156 } 157 if (rc->ca_key != NULL) 158 key_free(rc->ca_key); 159 } 160 161 void 162 ssh_krl_free(struct ssh_krl *krl) 163 { 164 struct revoked_blob *rb, *trb; 165 struct revoked_certs *rc, *trc; 166 167 if (krl == NULL) 168 return; 169 170 free(krl->comment); 171 RB_FOREACH_SAFE(rb, revoked_blob_tree, &krl->revoked_keys, trb) { 172 RB_REMOVE(revoked_blob_tree, &krl->revoked_keys, rb); 173 free(rb->blob); 174 free(rb); 175 } 176 RB_FOREACH_SAFE(rb, revoked_blob_tree, &krl->revoked_sha1s, trb) { 177 RB_REMOVE(revoked_blob_tree, &krl->revoked_sha1s, rb); 178 free(rb->blob); 179 free(rb); 180 } 181 TAILQ_FOREACH_SAFE(rc, &krl->revoked_certs, entry, trc) { 182 TAILQ_REMOVE(&krl->revoked_certs, rc, entry); 183 revoked_certs_free(rc); 184 } 185 } 186 187 void 188 ssh_krl_set_version(struct ssh_krl *krl, u_int64_t version) 189 { 190 krl->krl_version = version; 191 } 192 193 void 194 ssh_krl_set_comment(struct ssh_krl *krl, const char *comment) 195 { 196 free(krl->comment); 197 if ((krl->comment = strdup(comment)) == NULL) 198 fatal("%s: strdup", __func__); 199 } 200 201 /* 202 * Find the revoked_certs struct for a CA key. If allow_create is set then 203 * create a new one in the tree if one did not exist already. 204 */ 205 static int 206 revoked_certs_for_ca_key(struct ssh_krl *krl, const Key *ca_key, 207 struct revoked_certs **rcp, int allow_create) 208 { 209 struct revoked_certs *rc; 210 211 *rcp = NULL; 212 TAILQ_FOREACH(rc, &krl->revoked_certs, entry) { 213 if (key_equal(rc->ca_key, ca_key)) { 214 *rcp = rc; 215 return 0; 216 } 217 } 218 if (!allow_create) 219 return 0; 220 /* If this CA doesn't exist in the list then add it now */ 221 if ((rc = calloc(1, sizeof(*rc))) == NULL) 222 return -1; 223 if ((rc->ca_key = key_from_private(ca_key)) == NULL) { 224 free(rc); 225 return -1; 226 } 227 RB_INIT(&rc->revoked_serials); 228 RB_INIT(&rc->revoked_key_ids); 229 TAILQ_INSERT_TAIL(&krl->revoked_certs, rc, entry); 230 debug3("%s: new CA %s", __func__, key_type(ca_key)); 231 *rcp = rc; 232 return 0; 233 } 234 235 static int 236 insert_serial_range(struct revoked_serial_tree *rt, u_int64_t lo, u_int64_t hi) 237 { 238 struct revoked_serial rs, *ers, *crs, *irs; 239 240 KRL_DBG(("%s: insert %llu:%llu", __func__, lo, hi)); 241 bzero(&rs, sizeof(rs)); 242 rs.lo = lo; 243 rs.hi = hi; 244 ers = RB_NFIND(revoked_serial_tree, rt, &rs); 245 if (ers == NULL || serial_cmp(ers, &rs) != 0) { 246 /* No entry matches. Just insert */ 247 if ((irs = malloc(sizeof(rs))) == NULL) 248 return -1; 249 memcpy(irs, &rs, sizeof(*irs)); 250 ers = RB_INSERT(revoked_serial_tree, rt, irs); 251 if (ers != NULL) { 252 KRL_DBG(("%s: bad: ers != NULL", __func__)); 253 /* Shouldn't happen */ 254 free(irs); 255 return -1; 256 } 257 ers = irs; 258 } else { 259 KRL_DBG(("%s: overlap found %llu:%llu", __func__, 260 ers->lo, ers->hi)); 261 /* 262 * The inserted entry overlaps an existing one. Grow the 263 * existing entry. 264 */ 265 if (ers->lo > lo) 266 ers->lo = lo; 267 if (ers->hi < hi) 268 ers->hi = hi; 269 } 270 /* 271 * The inserted or revised range might overlap or abut adjacent ones; 272 * coalesce as necessary. 273 */ 274 275 /* Check predecessors */ 276 while ((crs = RB_PREV(revoked_serial_tree, rt, ers)) != NULL) { 277 KRL_DBG(("%s: pred %llu:%llu", __func__, crs->lo, crs->hi)); 278 if (ers->lo != 0 && crs->hi < ers->lo - 1) 279 break; 280 /* This entry overlaps. */ 281 if (crs->lo < ers->lo) { 282 ers->lo = crs->lo; 283 KRL_DBG(("%s: pred extend %llu:%llu", __func__, 284 ers->lo, ers->hi)); 285 } 286 RB_REMOVE(revoked_serial_tree, rt, crs); 287 free(crs); 288 } 289 /* Check successors */ 290 while ((crs = RB_NEXT(revoked_serial_tree, rt, ers)) != NULL) { 291 KRL_DBG(("%s: succ %llu:%llu", __func__, crs->lo, crs->hi)); 292 if (ers->hi != (u_int64_t)-1 && crs->lo > ers->hi + 1) 293 break; 294 /* This entry overlaps. */ 295 if (crs->hi > ers->hi) { 296 ers->hi = crs->hi; 297 KRL_DBG(("%s: succ extend %llu:%llu", __func__, 298 ers->lo, ers->hi)); 299 } 300 RB_REMOVE(revoked_serial_tree, rt, crs); 301 free(crs); 302 } 303 KRL_DBG(("%s: done, final %llu:%llu", __func__, ers->lo, ers->hi)); 304 return 0; 305 } 306 307 int 308 ssh_krl_revoke_cert_by_serial(struct ssh_krl *krl, const Key *ca_key, 309 u_int64_t serial) 310 { 311 return ssh_krl_revoke_cert_by_serial_range(krl, ca_key, serial, serial); 312 } 313 314 int 315 ssh_krl_revoke_cert_by_serial_range(struct ssh_krl *krl, const Key *ca_key, 316 u_int64_t lo, u_int64_t hi) 317 { 318 struct revoked_certs *rc; 319 320 if (lo > hi || lo == 0) 321 return -1; 322 if (revoked_certs_for_ca_key(krl, ca_key, &rc, 1) != 0) 323 return -1; 324 return insert_serial_range(&rc->revoked_serials, lo, hi); 325 } 326 327 int 328 ssh_krl_revoke_cert_by_key_id(struct ssh_krl *krl, const Key *ca_key, 329 const char *key_id) 330 { 331 struct revoked_key_id *rki, *erki; 332 struct revoked_certs *rc; 333 334 if (revoked_certs_for_ca_key(krl, ca_key, &rc, 1) != 0) 335 return -1; 336 337 debug3("%s: revoke %s", __func__, key_id); 338 if ((rki = calloc(1, sizeof(*rki))) == NULL || 339 (rki->key_id = strdup(key_id)) == NULL) { 340 free(rki); 341 fatal("%s: strdup", __func__); 342 } 343 erki = RB_INSERT(revoked_key_id_tree, &rc->revoked_key_ids, rki); 344 if (erki != NULL) { 345 free(rki->key_id); 346 free(rki); 347 } 348 return 0; 349 } 350 351 /* Convert "key" to a public key blob without any certificate information */ 352 static int 353 plain_key_blob(const Key *key, u_char **blob, u_int *blen) 354 { 355 Key *kcopy; 356 int r; 357 358 if ((kcopy = key_from_private(key)) == NULL) 359 return -1; 360 if (key_is_cert(kcopy)) { 361 if (key_drop_cert(kcopy) != 0) { 362 error("%s: key_drop_cert", __func__); 363 key_free(kcopy); 364 return -1; 365 } 366 } 367 r = key_to_blob(kcopy, blob, blen); 368 free(kcopy); 369 return r == 0 ? -1 : 0; 370 } 371 372 /* Revoke a key blob. Ownership of blob is transferred to the tree */ 373 static int 374 revoke_blob(struct revoked_blob_tree *rbt, u_char *blob, u_int len) 375 { 376 struct revoked_blob *rb, *erb; 377 378 if ((rb = calloc(1, sizeof(*rb))) == NULL) 379 return -1; 380 rb->blob = blob; 381 rb->len = len; 382 erb = RB_INSERT(revoked_blob_tree, rbt, rb); 383 if (erb != NULL) { 384 free(rb->blob); 385 free(rb); 386 } 387 return 0; 388 } 389 390 int 391 ssh_krl_revoke_key_explicit(struct ssh_krl *krl, const Key *key) 392 { 393 u_char *blob; 394 u_int len; 395 396 debug3("%s: revoke type %s", __func__, key_type(key)); 397 if (plain_key_blob(key, &blob, &len) != 0) 398 return -1; 399 return revoke_blob(&krl->revoked_keys, blob, len); 400 } 401 402 int 403 ssh_krl_revoke_key_sha1(struct ssh_krl *krl, const Key *key) 404 { 405 u_char *blob; 406 u_int len; 407 408 debug3("%s: revoke type %s by sha1", __func__, key_type(key)); 409 if ((blob = key_fingerprint_raw(key, SSH_FP_SHA1, &len)) == NULL) 410 return -1; 411 return revoke_blob(&krl->revoked_sha1s, blob, len); 412 } 413 414 int 415 ssh_krl_revoke_key(struct ssh_krl *krl, const Key *key) 416 { 417 if (!key_is_cert(key)) 418 return ssh_krl_revoke_key_sha1(krl, key); 419 420 if (key_cert_is_legacy(key) || key->cert->serial == 0) { 421 return ssh_krl_revoke_cert_by_key_id(krl, 422 key->cert->signature_key, 423 key->cert->key_id); 424 } else { 425 return ssh_krl_revoke_cert_by_serial(krl, 426 key->cert->signature_key, 427 key->cert->serial); 428 } 429 } 430 431 /* 432 * Select a copact next section type to emit in a KRL based on the 433 * current section type, the run length of contiguous revoked serial 434 * numbers and the gaps from the last and to the next revoked serial. 435 * Applies a mostly-accurate bit cost model to select the section type 436 * that will minimise the size of the resultant KRL. 437 */ 438 static int 439 choose_next_state(int current_state, u_int64_t contig, int final, 440 u_int64_t last_gap, u_int64_t next_gap, int *force_new_section) 441 { 442 int new_state; 443 u_int64_t cost, cost_list, cost_range, cost_bitmap, cost_bitmap_restart; 444 445 /* 446 * Avoid unsigned overflows. 447 * The limits are high enough to avoid confusing the calculations. 448 */ 449 contig = MIN(contig, 1ULL<<31); 450 last_gap = MIN(last_gap, 1ULL<<31); 451 next_gap = MIN(next_gap, 1ULL<<31); 452 453 /* 454 * Calculate the cost to switch from the current state to candidates. 455 * NB. range sections only ever contain a single range, so their 456 * switching cost is independent of the current_state. 457 */ 458 cost_list = cost_bitmap = cost_bitmap_restart = 0; 459 cost_range = 8; 460 switch (current_state) { 461 case KRL_SECTION_CERT_SERIAL_LIST: 462 cost_bitmap_restart = cost_bitmap = 8 + 64; 463 break; 464 case KRL_SECTION_CERT_SERIAL_BITMAP: 465 cost_list = 8; 466 cost_bitmap_restart = 8 + 64; 467 break; 468 case KRL_SECTION_CERT_SERIAL_RANGE: 469 case 0: 470 cost_bitmap_restart = cost_bitmap = 8 + 64; 471 cost_list = 8; 472 } 473 474 /* Estimate base cost in bits of each section type */ 475 cost_list += 64 * contig + (final ? 0 : 8+64); 476 cost_range += (2 * 64) + (final ? 0 : 8+64); 477 cost_bitmap += last_gap + contig + (final ? 0 : MIN(next_gap, 8+64)); 478 cost_bitmap_restart += contig + (final ? 0 : MIN(next_gap, 8+64)); 479 480 /* Convert to byte costs for actual comparison */ 481 cost_list = (cost_list + 7) / 8; 482 cost_bitmap = (cost_bitmap + 7) / 8; 483 cost_bitmap_restart = (cost_bitmap_restart + 7) / 8; 484 cost_range = (cost_range + 7) / 8; 485 486 /* Now pick the best choice */ 487 *force_new_section = 0; 488 new_state = KRL_SECTION_CERT_SERIAL_BITMAP; 489 cost = cost_bitmap; 490 if (cost_range < cost) { 491 new_state = KRL_SECTION_CERT_SERIAL_RANGE; 492 cost = cost_range; 493 } 494 if (cost_list < cost) { 495 new_state = KRL_SECTION_CERT_SERIAL_LIST; 496 cost = cost_list; 497 } 498 if (cost_bitmap_restart < cost) { 499 new_state = KRL_SECTION_CERT_SERIAL_BITMAP; 500 *force_new_section = 1; 501 cost = cost_bitmap_restart; 502 } 503 debug3("%s: contig %llu last_gap %llu next_gap %llu final %d, costs:" 504 "list %llu range %llu bitmap %llu new bitmap %llu, " 505 "selected 0x%02x%s", __func__, (unsigned long long)contig, 506 (unsigned long long)last_gap, (unsigned long long)next_gap, final, 507 (unsigned long long)cost_list, (unsigned long long)cost_range, 508 (unsigned long long)cost_bitmap, 509 (unsigned long long)cost_bitmap_restart, new_state, 510 *force_new_section ? " restart" : ""); 511 return new_state; 512 } 513 514 /* Generate a KRL_SECTION_CERTIFICATES KRL section */ 515 static int 516 revoked_certs_generate(struct revoked_certs *rc, Buffer *buf) 517 { 518 int final, force_new_sect, r = -1; 519 u_int64_t i, contig, gap, last = 0, bitmap_start = 0; 520 struct revoked_serial *rs, *nrs; 521 struct revoked_key_id *rki; 522 int next_state, state = 0; 523 Buffer sect; 524 u_char *kblob = NULL; 525 u_int klen; 526 BIGNUM *bitmap = NULL; 527 528 /* Prepare CA scope key blob if we have one supplied */ 529 if (key_to_blob(rc->ca_key, &kblob, &klen) == 0) 530 return -1; 531 532 buffer_init(§); 533 534 /* Store the header */ 535 buffer_put_string(buf, kblob, klen); 536 buffer_put_string(buf, NULL, 0); /* Reserved */ 537 538 free(kblob); 539 540 /* Store the revoked serials. */ 541 for (rs = RB_MIN(revoked_serial_tree, &rc->revoked_serials); 542 rs != NULL; 543 rs = RB_NEXT(revoked_serial_tree, &rc->revoked_serials, rs)) { 544 debug3("%s: serial %llu:%llu state 0x%02x", __func__, 545 (unsigned long long)rs->lo, (unsigned long long)rs->hi, 546 state); 547 548 /* Check contiguous length and gap to next section (if any) */ 549 nrs = RB_NEXT(revoked_serial_tree, &rc->revoked_serials, rs); 550 final = nrs == NULL; 551 gap = nrs == NULL ? 0 : nrs->lo - rs->hi; 552 contig = 1 + (rs->hi - rs->lo); 553 554 /* Choose next state based on these */ 555 next_state = choose_next_state(state, contig, final, 556 state == 0 ? 0 : rs->lo - last, gap, &force_new_sect); 557 558 /* 559 * If the current section is a range section or has a different 560 * type to the next section, then finish it off now. 561 */ 562 if (state != 0 && (force_new_sect || next_state != state || 563 state == KRL_SECTION_CERT_SERIAL_RANGE)) { 564 debug3("%s: finish state 0x%02x", __func__, state); 565 switch (state) { 566 case KRL_SECTION_CERT_SERIAL_LIST: 567 case KRL_SECTION_CERT_SERIAL_RANGE: 568 break; 569 case KRL_SECTION_CERT_SERIAL_BITMAP: 570 buffer_put_bignum2(§, bitmap); 571 BN_free(bitmap); 572 bitmap = NULL; 573 break; 574 } 575 buffer_put_char(buf, state); 576 buffer_put_string(buf, 577 buffer_ptr(§), buffer_len(§)); 578 } 579 580 /* If we are starting a new section then prepare it now */ 581 if (next_state != state || force_new_sect) { 582 debug3("%s: start state 0x%02x", __func__, next_state); 583 state = next_state; 584 buffer_clear(§); 585 switch (state) { 586 case KRL_SECTION_CERT_SERIAL_LIST: 587 case KRL_SECTION_CERT_SERIAL_RANGE: 588 break; 589 case KRL_SECTION_CERT_SERIAL_BITMAP: 590 if ((bitmap = BN_new()) == NULL) 591 goto out; 592 bitmap_start = rs->lo; 593 buffer_put_int64(§, bitmap_start); 594 break; 595 } 596 } 597 598 /* Perform section-specific processing */ 599 switch (state) { 600 case KRL_SECTION_CERT_SERIAL_LIST: 601 for (i = 0; i < contig; i++) 602 buffer_put_int64(§, rs->lo + i); 603 break; 604 case KRL_SECTION_CERT_SERIAL_RANGE: 605 buffer_put_int64(§, rs->lo); 606 buffer_put_int64(§, rs->hi); 607 break; 608 case KRL_SECTION_CERT_SERIAL_BITMAP: 609 if (rs->lo - bitmap_start > INT_MAX) { 610 error("%s: insane bitmap gap", __func__); 611 goto out; 612 } 613 for (i = 0; i < contig; i++) { 614 if (BN_set_bit(bitmap, 615 rs->lo + i - bitmap_start) != 1) 616 goto out; 617 } 618 break; 619 } 620 last = rs->hi; 621 } 622 /* Flush the remaining section, if any */ 623 if (state != 0) { 624 debug3("%s: serial final flush for state 0x%02x", 625 __func__, state); 626 switch (state) { 627 case KRL_SECTION_CERT_SERIAL_LIST: 628 case KRL_SECTION_CERT_SERIAL_RANGE: 629 break; 630 case KRL_SECTION_CERT_SERIAL_BITMAP: 631 buffer_put_bignum2(§, bitmap); 632 BN_free(bitmap); 633 bitmap = NULL; 634 break; 635 } 636 buffer_put_char(buf, state); 637 buffer_put_string(buf, 638 buffer_ptr(§), buffer_len(§)); 639 } 640 debug3("%s: serial done ", __func__); 641 642 /* Now output a section for any revocations by key ID */ 643 buffer_clear(§); 644 RB_FOREACH(rki, revoked_key_id_tree, &rc->revoked_key_ids) { 645 debug3("%s: key ID %s", __func__, rki->key_id); 646 buffer_put_cstring(§, rki->key_id); 647 } 648 if (buffer_len(§) != 0) { 649 buffer_put_char(buf, KRL_SECTION_CERT_KEY_ID); 650 buffer_put_string(buf, buffer_ptr(§), 651 buffer_len(§)); 652 } 653 r = 0; 654 out: 655 if (bitmap != NULL) 656 BN_free(bitmap); 657 buffer_free(§); 658 return r; 659 } 660 661 int 662 ssh_krl_to_blob(struct ssh_krl *krl, Buffer *buf, const Key **sign_keys, 663 u_int nsign_keys) 664 { 665 int r = -1; 666 struct revoked_certs *rc; 667 struct revoked_blob *rb; 668 Buffer sect; 669 u_char *kblob = NULL, *sblob = NULL; 670 u_int klen, slen, i; 671 672 if (krl->generated_date == 0) 673 krl->generated_date = time(NULL); 674 675 buffer_init(§); 676 677 /* Store the header */ 678 buffer_append(buf, KRL_MAGIC, sizeof(KRL_MAGIC) - 1); 679 buffer_put_int(buf, KRL_FORMAT_VERSION); 680 buffer_put_int64(buf, krl->krl_version); 681 buffer_put_int64(buf, krl->generated_date); 682 buffer_put_int64(buf, krl->flags); 683 buffer_put_string(buf, NULL, 0); 684 buffer_put_cstring(buf, krl->comment ? krl->comment : ""); 685 686 /* Store sections for revoked certificates */ 687 TAILQ_FOREACH(rc, &krl->revoked_certs, entry) { 688 if (revoked_certs_generate(rc, §) != 0) 689 goto out; 690 buffer_put_char(buf, KRL_SECTION_CERTIFICATES); 691 buffer_put_string(buf, buffer_ptr(§), 692 buffer_len(§)); 693 } 694 695 /* Finally, output sections for revocations by public key/hash */ 696 buffer_clear(§); 697 RB_FOREACH(rb, revoked_blob_tree, &krl->revoked_keys) { 698 debug3("%s: key len %u ", __func__, rb->len); 699 buffer_put_string(§, rb->blob, rb->len); 700 } 701 if (buffer_len(§) != 0) { 702 buffer_put_char(buf, KRL_SECTION_EXPLICIT_KEY); 703 buffer_put_string(buf, buffer_ptr(§), 704 buffer_len(§)); 705 } 706 buffer_clear(§); 707 RB_FOREACH(rb, revoked_blob_tree, &krl->revoked_sha1s) { 708 debug3("%s: hash len %u ", __func__, rb->len); 709 buffer_put_string(§, rb->blob, rb->len); 710 } 711 if (buffer_len(§) != 0) { 712 buffer_put_char(buf, KRL_SECTION_FINGERPRINT_SHA1); 713 buffer_put_string(buf, buffer_ptr(§), 714 buffer_len(§)); 715 } 716 717 for (i = 0; i < nsign_keys; i++) { 718 if (key_to_blob(sign_keys[i], &kblob, &klen) == 0) 719 goto out; 720 721 debug3("%s: signature key len %u", __func__, klen); 722 buffer_put_char(buf, KRL_SECTION_SIGNATURE); 723 buffer_put_string(buf, kblob, klen); 724 725 if (key_sign(sign_keys[i], &sblob, &slen, 726 buffer_ptr(buf), buffer_len(buf)) == -1) 727 goto out; 728 debug3("%s: signature sig len %u", __func__, slen); 729 buffer_put_string(buf, sblob, slen); 730 } 731 732 r = 0; 733 out: 734 free(kblob); 735 free(sblob); 736 buffer_free(§); 737 return r; 738 } 739 740 static void 741 format_timestamp(u_int64_t timestamp, char *ts, size_t nts) 742 { 743 time_t t; 744 struct tm *tm; 745 746 t = timestamp; 747 tm = localtime(&t); 748 *ts = '\0'; 749 strftime(ts, nts, "%Y%m%dT%H%M%S", tm); 750 } 751 752 static int 753 parse_revoked_certs(Buffer *buf, struct ssh_krl *krl) 754 { 755 int ret = -1, nbits; 756 u_char type, *blob; 757 u_int blen; 758 Buffer subsect; 759 u_int64_t serial, serial_lo, serial_hi; 760 BIGNUM *bitmap = NULL; 761 char *key_id = NULL; 762 Key *ca_key = NULL; 763 764 buffer_init(&subsect); 765 766 if ((blob = buffer_get_string_ptr_ret(buf, &blen)) == NULL || 767 buffer_get_string_ptr_ret(buf, NULL) == NULL) { /* reserved */ 768 error("%s: buffer error", __func__); 769 goto out; 770 } 771 if ((ca_key = key_from_blob(blob, blen)) == NULL) 772 goto out; 773 774 while (buffer_len(buf) > 0) { 775 if (buffer_get_char_ret(&type, buf) != 0 || 776 (blob = buffer_get_string_ptr_ret(buf, &blen)) == NULL) { 777 error("%s: buffer error", __func__); 778 goto out; 779 } 780 buffer_clear(&subsect); 781 buffer_append(&subsect, blob, blen); 782 debug3("%s: subsection type 0x%02x", __func__, type); 783 /* buffer_dump(&subsect); */ 784 785 switch (type) { 786 case KRL_SECTION_CERT_SERIAL_LIST: 787 while (buffer_len(&subsect) > 0) { 788 if (buffer_get_int64_ret(&serial, 789 &subsect) != 0) { 790 error("%s: buffer error", __func__); 791 goto out; 792 } 793 if (ssh_krl_revoke_cert_by_serial(krl, ca_key, 794 serial) != 0) { 795 error("%s: update failed", __func__); 796 goto out; 797 } 798 } 799 break; 800 case KRL_SECTION_CERT_SERIAL_RANGE: 801 if (buffer_get_int64_ret(&serial_lo, &subsect) != 0 || 802 buffer_get_int64_ret(&serial_hi, &subsect) != 0) { 803 error("%s: buffer error", __func__); 804 goto out; 805 } 806 if (ssh_krl_revoke_cert_by_serial_range(krl, ca_key, 807 serial_lo, serial_hi) != 0) { 808 error("%s: update failed", __func__); 809 goto out; 810 } 811 break; 812 case KRL_SECTION_CERT_SERIAL_BITMAP: 813 if ((bitmap = BN_new()) == NULL) { 814 error("%s: BN_new", __func__); 815 goto out; 816 } 817 if (buffer_get_int64_ret(&serial_lo, &subsect) != 0 || 818 buffer_get_bignum2_ret(&subsect, bitmap) != 0) { 819 error("%s: buffer error", __func__); 820 goto out; 821 } 822 if ((nbits = BN_num_bits(bitmap)) < 0) { 823 error("%s: bitmap bits < 0", __func__); 824 goto out; 825 } 826 for (serial = 0; serial < (u_int)nbits; serial++) { 827 if (serial > 0 && serial_lo + serial == 0) { 828 error("%s: bitmap wraps u64", __func__); 829 goto out; 830 } 831 if (!BN_is_bit_set(bitmap, serial)) 832 continue; 833 if (ssh_krl_revoke_cert_by_serial(krl, ca_key, 834 serial_lo + serial) != 0) { 835 error("%s: update failed", __func__); 836 goto out; 837 } 838 } 839 BN_free(bitmap); 840 bitmap = NULL; 841 break; 842 case KRL_SECTION_CERT_KEY_ID: 843 while (buffer_len(&subsect) > 0) { 844 if ((key_id = buffer_get_cstring_ret(&subsect, 845 NULL)) == NULL) { 846 error("%s: buffer error", __func__); 847 goto out; 848 } 849 if (ssh_krl_revoke_cert_by_key_id(krl, ca_key, 850 key_id) != 0) { 851 error("%s: update failed", __func__); 852 goto out; 853 } 854 free(key_id); 855 key_id = NULL; 856 } 857 break; 858 default: 859 error("Unsupported KRL certificate section %u", type); 860 goto out; 861 } 862 if (buffer_len(&subsect) > 0) { 863 error("KRL certificate section contains unparsed data"); 864 goto out; 865 } 866 } 867 868 ret = 0; 869 out: 870 if (ca_key != NULL) 871 key_free(ca_key); 872 if (bitmap != NULL) 873 BN_free(bitmap); 874 free(key_id); 875 buffer_free(&subsect); 876 return ret; 877 } 878 879 880 /* Attempt to parse a KRL, checking its signature (if any) with sign_ca_keys. */ 881 int 882 ssh_krl_from_blob(Buffer *buf, struct ssh_krl **krlp, 883 const Key **sign_ca_keys, u_int nsign_ca_keys) 884 { 885 Buffer copy, sect; 886 struct ssh_krl *krl; 887 char timestamp[64]; 888 int ret = -1, r, sig_seen; 889 Key *key = NULL, **ca_used = NULL; 890 u_char type, *blob; 891 u_int i, j, sig_off, sects_off, blen, format_version, nca_used = 0; 892 893 *krlp = NULL; 894 if (buffer_len(buf) < sizeof(KRL_MAGIC) - 1 || 895 memcmp(buffer_ptr(buf), KRL_MAGIC, sizeof(KRL_MAGIC) - 1) != 0) { 896 debug3("%s: not a KRL", __func__); 897 /* 898 * Return success but a NULL *krlp here to signal that the 899 * file might be a simple list of keys. 900 */ 901 return 0; 902 } 903 904 /* Take a copy of the KRL buffer so we can verify its signature later */ 905 buffer_init(©); 906 buffer_append(©, buffer_ptr(buf), buffer_len(buf)); 907 908 buffer_init(§); 909 buffer_consume(©, sizeof(KRL_MAGIC) - 1); 910 911 if ((krl = ssh_krl_init()) == NULL) { 912 error("%s: alloc failed", __func__); 913 goto out; 914 } 915 916 if (buffer_get_int_ret(&format_version, ©) != 0) { 917 error("%s: KRL truncated", __func__); 918 goto out; 919 } 920 if (format_version != KRL_FORMAT_VERSION) { 921 error("%s: KRL unsupported format version %u", 922 __func__, format_version); 923 goto out; 924 } 925 if (buffer_get_int64_ret(&krl->krl_version, ©) != 0 || 926 buffer_get_int64_ret(&krl->generated_date, ©) != 0 || 927 buffer_get_int64_ret(&krl->flags, ©) != 0 || 928 buffer_get_string_ptr_ret(©, NULL) == NULL || /* reserved */ 929 (krl->comment = buffer_get_cstring_ret(©, NULL)) == NULL) { 930 error("%s: buffer error", __func__); 931 goto out; 932 } 933 934 format_timestamp(krl->generated_date, timestamp, sizeof(timestamp)); 935 debug("KRL version %llu generated at %s%s%s", 936 (unsigned long long)krl->krl_version, timestamp, 937 *krl->comment ? ": " : "", krl->comment); 938 939 /* 940 * 1st pass: verify signatures, if any. This is done to avoid 941 * detailed parsing of data whose provenance is unverified. 942 */ 943 sig_seen = 0; 944 sects_off = buffer_len(buf) - buffer_len(©); 945 while (buffer_len(©) > 0) { 946 if (buffer_get_char_ret(&type, ©) != 0 || 947 (blob = buffer_get_string_ptr_ret(©, &blen)) == NULL) { 948 error("%s: buffer error", __func__); 949 goto out; 950 } 951 debug3("%s: first pass, section 0x%02x", __func__, type); 952 if (type != KRL_SECTION_SIGNATURE) { 953 if (sig_seen) { 954 error("KRL contains non-signature section " 955 "after signature"); 956 goto out; 957 } 958 /* Not interested for now. */ 959 continue; 960 } 961 sig_seen = 1; 962 /* First string component is the signing key */ 963 if ((key = key_from_blob(blob, blen)) == NULL) { 964 error("%s: invalid signature key", __func__); 965 goto out; 966 } 967 sig_off = buffer_len(buf) - buffer_len(©); 968 /* Second string component is the signature itself */ 969 if ((blob = buffer_get_string_ptr_ret(©, &blen)) == NULL) { 970 error("%s: buffer error", __func__); 971 goto out; 972 } 973 /* Check signature over entire KRL up to this point */ 974 if (key_verify(key, blob, blen, 975 buffer_ptr(buf), buffer_len(buf) - sig_off) == -1) { 976 error("bad signaure on KRL"); 977 goto out; 978 } 979 /* Check if this key has already signed this KRL */ 980 for (i = 0; i < nca_used; i++) { 981 if (key_equal(ca_used[i], key)) { 982 error("KRL signed more than once with " 983 "the same key"); 984 goto out; 985 } 986 } 987 /* Record keys used to sign the KRL */ 988 ca_used = xrealloc(ca_used, nca_used + 1, sizeof(*ca_used)); 989 ca_used[nca_used++] = key; 990 key = NULL; 991 break; 992 } 993 994 /* 995 * 2nd pass: parse and load the KRL, skipping the header to the point 996 * where the section start. 997 */ 998 buffer_append(©, (u_char*)buffer_ptr(buf) + sects_off, 999 buffer_len(buf) - sects_off); 1000 while (buffer_len(©) > 0) { 1001 if (buffer_get_char_ret(&type, ©) != 0 || 1002 (blob = buffer_get_string_ptr_ret(©, &blen)) == NULL) { 1003 error("%s: buffer error", __func__); 1004 goto out; 1005 } 1006 debug3("%s: second pass, section 0x%02x", __func__, type); 1007 buffer_clear(§); 1008 buffer_append(§, blob, blen); 1009 1010 switch (type) { 1011 case KRL_SECTION_CERTIFICATES: 1012 if ((r = parse_revoked_certs(§, krl)) != 0) 1013 goto out; 1014 break; 1015 case KRL_SECTION_EXPLICIT_KEY: 1016 case KRL_SECTION_FINGERPRINT_SHA1: 1017 while (buffer_len(§) > 0) { 1018 if ((blob = buffer_get_string_ret(§, 1019 &blen)) == NULL) { 1020 error("%s: buffer error", __func__); 1021 goto out; 1022 } 1023 if (type == KRL_SECTION_FINGERPRINT_SHA1 && 1024 blen != 20) { 1025 error("%s: bad SHA1 length", __func__); 1026 goto out; 1027 } 1028 if (revoke_blob( 1029 type == KRL_SECTION_EXPLICIT_KEY ? 1030 &krl->revoked_keys : &krl->revoked_sha1s, 1031 blob, blen) != 0) 1032 goto out; /* revoke_blob frees blob */ 1033 } 1034 break; 1035 case KRL_SECTION_SIGNATURE: 1036 /* Handled above, but still need to stay in synch */ 1037 buffer_clear(§); 1038 if ((blob = buffer_get_string_ptr_ret(©, 1039 &blen)) == NULL) { 1040 error("%s: buffer error", __func__); 1041 goto out; 1042 } 1043 break; 1044 default: 1045 error("Unsupported KRL section %u", type); 1046 goto out; 1047 } 1048 if (buffer_len(§) > 0) { 1049 error("KRL section contains unparsed data"); 1050 goto out; 1051 } 1052 } 1053 1054 /* Check that the key(s) used to sign the KRL weren't revoked */ 1055 sig_seen = 0; 1056 for (i = 0; i < nca_used; i++) { 1057 if (ssh_krl_check_key(krl, ca_used[i]) == 0) 1058 sig_seen = 1; 1059 else { 1060 key_free(ca_used[i]); 1061 ca_used[i] = NULL; 1062 } 1063 } 1064 if (nca_used && !sig_seen) { 1065 error("All keys used to sign KRL were revoked"); 1066 goto out; 1067 } 1068 1069 /* If we have CA keys, then verify that one was used to sign the KRL */ 1070 if (sig_seen && nsign_ca_keys != 0) { 1071 sig_seen = 0; 1072 for (i = 0; !sig_seen && i < nsign_ca_keys; i++) { 1073 for (j = 0; j < nca_used; j++) { 1074 if (ca_used[j] == NULL) 1075 continue; 1076 if (key_equal(ca_used[j], sign_ca_keys[i])) { 1077 sig_seen = 1; 1078 break; 1079 } 1080 } 1081 } 1082 if (!sig_seen) { 1083 error("KRL not signed with any trusted key"); 1084 goto out; 1085 } 1086 } 1087 1088 *krlp = krl; 1089 ret = 0; 1090 out: 1091 if (ret != 0) 1092 ssh_krl_free(krl); 1093 for (i = 0; i < nca_used; i++) { 1094 if (ca_used[i] != NULL) 1095 key_free(ca_used[i]); 1096 } 1097 free(ca_used); 1098 if (key != NULL) 1099 key_free(key); 1100 buffer_free(©); 1101 buffer_free(§); 1102 return ret; 1103 } 1104 1105 /* Checks whether a given key/cert is revoked. Does not check its CA */ 1106 static int 1107 is_key_revoked(struct ssh_krl *krl, const Key *key) 1108 { 1109 struct revoked_blob rb, *erb; 1110 struct revoked_serial rs, *ers; 1111 struct revoked_key_id rki, *erki; 1112 struct revoked_certs *rc; 1113 1114 /* Check explicitly revoked hashes first */ 1115 bzero(&rb, sizeof(rb)); 1116 if ((rb.blob = key_fingerprint_raw(key, SSH_FP_SHA1, &rb.len)) == NULL) 1117 return -1; 1118 erb = RB_FIND(revoked_blob_tree, &krl->revoked_sha1s, &rb); 1119 free(rb.blob); 1120 if (erb != NULL) { 1121 debug("%s: revoked by key SHA1", __func__); 1122 return -1; 1123 } 1124 1125 /* Next, explicit keys */ 1126 bzero(&rb, sizeof(rb)); 1127 if (plain_key_blob(key, &rb.blob, &rb.len) != 0) 1128 return -1; 1129 erb = RB_FIND(revoked_blob_tree, &krl->revoked_keys, &rb); 1130 free(rb.blob); 1131 if (erb != NULL) { 1132 debug("%s: revoked by explicit key", __func__); 1133 return -1; 1134 } 1135 1136 if (!key_is_cert(key)) 1137 return 0; 1138 1139 /* Check cert revocation */ 1140 if (revoked_certs_for_ca_key(krl, key->cert->signature_key, 1141 &rc, 0) != 0) 1142 return -1; 1143 if (rc == NULL) 1144 return 0; /* No entry for this CA */ 1145 1146 /* Check revocation by cert key ID */ 1147 bzero(&rki, sizeof(rki)); 1148 rki.key_id = key->cert->key_id; 1149 erki = RB_FIND(revoked_key_id_tree, &rc->revoked_key_ids, &rki); 1150 if (erki != NULL) { 1151 debug("%s: revoked by key ID", __func__); 1152 return -1; 1153 } 1154 1155 /* 1156 * Legacy cert formats lack serial numbers. Zero serials numbers 1157 * are ignored (it's the default when the CA doesn't specify one). 1158 */ 1159 if (key_cert_is_legacy(key) || key->cert->serial == 0) 1160 return 0; 1161 1162 bzero(&rs, sizeof(rs)); 1163 rs.lo = rs.hi = key->cert->serial; 1164 ers = RB_FIND(revoked_serial_tree, &rc->revoked_serials, &rs); 1165 if (ers != NULL) { 1166 KRL_DBG(("%s: %llu matched %llu:%llu", __func__, 1167 key->cert->serial, ers->lo, ers->hi)); 1168 debug("%s: revoked by serial", __func__); 1169 return -1; 1170 } 1171 KRL_DBG(("%s: %llu no match", __func__, key->cert->serial)); 1172 1173 return 0; 1174 } 1175 1176 int 1177 ssh_krl_check_key(struct ssh_krl *krl, const Key *key) 1178 { 1179 int r; 1180 1181 debug2("%s: checking key", __func__); 1182 if ((r = is_key_revoked(krl, key)) != 0) 1183 return r; 1184 if (key_is_cert(key)) { 1185 debug2("%s: checking CA key", __func__); 1186 if ((r = is_key_revoked(krl, key->cert->signature_key)) != 0) 1187 return r; 1188 } 1189 debug3("%s: key okay", __func__); 1190 return 0; 1191 } 1192 1193 /* Returns 0 on success, -1 on error or key revoked, -2 if path is not a KRL */ 1194 int 1195 ssh_krl_file_contains_key(const char *path, const Key *key) 1196 { 1197 Buffer krlbuf; 1198 struct ssh_krl *krl; 1199 int revoked, fd; 1200 1201 if (path == NULL) 1202 return 0; 1203 1204 if ((fd = open(path, O_RDONLY)) == -1) { 1205 error("open %s: %s", path, strerror(errno)); 1206 error("Revoked keys file not accessible - refusing public key " 1207 "authentication"); 1208 return -1; 1209 } 1210 buffer_init(&krlbuf); 1211 if (!key_load_file(fd, path, &krlbuf)) { 1212 close(fd); 1213 buffer_free(&krlbuf); 1214 error("Revoked keys file not readable - refusing public key " 1215 "authentication"); 1216 return -1; 1217 } 1218 close(fd); 1219 if (ssh_krl_from_blob(&krlbuf, &krl, NULL, 0) != 0) { 1220 buffer_free(&krlbuf); 1221 error("Invalid KRL, refusing public key " 1222 "authentication"); 1223 return -1; 1224 } 1225 buffer_free(&krlbuf); 1226 if (krl == NULL) { 1227 debug3("%s: %s is not a KRL file", __func__, path); 1228 return -2; 1229 } 1230 debug2("%s: checking KRL %s", __func__, path); 1231 revoked = ssh_krl_check_key(krl, key) != 0; 1232 ssh_krl_free(krl); 1233 return revoked ? -1 : 0; 1234 } 1235