1 /* $OpenBSD: sshsig.c,v 1.30 2022/08/19 03:06:30 djm Exp $ */ 2 /* 3 * Copyright (c) 2019 Google LLC 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 "includes.h" 19 20 #include <stdio.h> 21 #include <stdlib.h> 22 #include <stdarg.h> 23 #include <errno.h> 24 #include <string.h> 25 #include <unistd.h> 26 27 #include "authfd.h" 28 #include "authfile.h" 29 #include "log.h" 30 #include "misc.h" 31 #include "sshbuf.h" 32 #include "sshsig.h" 33 #include "ssherr.h" 34 #include "sshkey.h" 35 #include "match.h" 36 #include "digest.h" 37 38 #define SIG_VERSION 0x01 39 #define MAGIC_PREAMBLE "SSHSIG" 40 #define MAGIC_PREAMBLE_LEN (sizeof(MAGIC_PREAMBLE) - 1) 41 #define BEGIN_SIGNATURE "-----BEGIN SSH SIGNATURE-----\n" 42 #define END_SIGNATURE "-----END SSH SIGNATURE-----" 43 #define RSA_SIGN_ALG "rsa-sha2-512" /* XXX maybe make configurable */ 44 #define RSA_SIGN_ALLOWED "rsa-sha2-512,rsa-sha2-256" 45 #define HASHALG_DEFAULT "sha512" /* XXX maybe make configurable */ 46 #define HASHALG_ALLOWED "sha256,sha512" 47 48 int 49 sshsig_armor(const struct sshbuf *blob, struct sshbuf **out) 50 { 51 struct sshbuf *buf = NULL; 52 int r = SSH_ERR_INTERNAL_ERROR; 53 54 *out = NULL; 55 56 if ((buf = sshbuf_new()) == NULL) { 57 error_f("sshbuf_new failed"); 58 r = SSH_ERR_ALLOC_FAIL; 59 goto out; 60 } 61 62 if ((r = sshbuf_put(buf, BEGIN_SIGNATURE, 63 sizeof(BEGIN_SIGNATURE)-1)) != 0) { 64 error_fr(r, "sshbuf_putf"); 65 goto out; 66 } 67 68 if ((r = sshbuf_dtob64(blob, buf, 1)) != 0) { 69 error_fr(r, "base64 encode signature"); 70 goto out; 71 } 72 73 if ((r = sshbuf_put(buf, END_SIGNATURE, 74 sizeof(END_SIGNATURE)-1)) != 0 || 75 (r = sshbuf_put_u8(buf, '\n')) != 0) { 76 error_fr(r, "sshbuf_put"); 77 goto out; 78 } 79 /* success */ 80 *out = buf; 81 buf = NULL; /* transferred */ 82 r = 0; 83 out: 84 sshbuf_free(buf); 85 return r; 86 } 87 88 int 89 sshsig_dearmor(struct sshbuf *sig, struct sshbuf **out) 90 { 91 int r; 92 size_t eoffset = 0; 93 struct sshbuf *buf = NULL; 94 struct sshbuf *sbuf = NULL; 95 char *b64 = NULL; 96 97 if ((sbuf = sshbuf_fromb(sig)) == NULL) { 98 error_f("sshbuf_fromb failed"); 99 return SSH_ERR_ALLOC_FAIL; 100 } 101 102 if ((r = sshbuf_cmp(sbuf, 0, 103 BEGIN_SIGNATURE, sizeof(BEGIN_SIGNATURE)-1)) != 0) { 104 error("Couldn't parse signature: missing header"); 105 goto done; 106 } 107 108 if ((r = sshbuf_consume(sbuf, sizeof(BEGIN_SIGNATURE)-1)) != 0) { 109 error_fr(r, "consume"); 110 goto done; 111 } 112 113 if ((r = sshbuf_find(sbuf, 0, "\n" END_SIGNATURE, 114 sizeof("\n" END_SIGNATURE)-1, &eoffset)) != 0) { 115 error("Couldn't parse signature: missing footer"); 116 goto done; 117 } 118 119 if ((r = sshbuf_consume_end(sbuf, sshbuf_len(sbuf)-eoffset)) != 0) { 120 error_fr(r, "consume"); 121 goto done; 122 } 123 124 if ((b64 = sshbuf_dup_string(sbuf)) == NULL) { 125 error_f("sshbuf_dup_string failed"); 126 r = SSH_ERR_ALLOC_FAIL; 127 goto done; 128 } 129 130 if ((buf = sshbuf_new()) == NULL) { 131 error_f("sshbuf_new() failed"); 132 r = SSH_ERR_ALLOC_FAIL; 133 goto done; 134 } 135 136 if ((r = sshbuf_b64tod(buf, b64)) != 0) { 137 error_fr(r, "decode base64"); 138 goto done; 139 } 140 141 /* success */ 142 *out = buf; 143 r = 0; 144 buf = NULL; /* transferred */ 145 done: 146 sshbuf_free(buf); 147 sshbuf_free(sbuf); 148 free(b64); 149 return r; 150 } 151 152 static int 153 sshsig_wrap_sign(struct sshkey *key, const char *hashalg, 154 const char *sk_provider, const char *sk_pin, const struct sshbuf *h_message, 155 const char *sig_namespace, struct sshbuf **out, 156 sshsig_signer *signer, void *signer_ctx) 157 { 158 int r; 159 size_t slen = 0; 160 u_char *sig = NULL; 161 struct sshbuf *blob = NULL; 162 struct sshbuf *tosign = NULL; 163 const char *sign_alg = NULL; 164 165 if ((tosign = sshbuf_new()) == NULL || 166 (blob = sshbuf_new()) == NULL) { 167 error_f("sshbuf_new failed"); 168 r = SSH_ERR_ALLOC_FAIL; 169 goto done; 170 } 171 172 if ((r = sshbuf_put(tosign, MAGIC_PREAMBLE, MAGIC_PREAMBLE_LEN)) != 0 || 173 (r = sshbuf_put_cstring(tosign, sig_namespace)) != 0 || 174 (r = sshbuf_put_string(tosign, NULL, 0)) != 0 || /* reserved */ 175 (r = sshbuf_put_cstring(tosign, hashalg)) != 0 || 176 (r = sshbuf_put_stringb(tosign, h_message)) != 0) { 177 error_fr(r, "assemble message to sign"); 178 goto done; 179 } 180 181 /* If using RSA keys then default to a good signature algorithm */ 182 if (sshkey_type_plain(key->type) == KEY_RSA) 183 sign_alg = RSA_SIGN_ALG; 184 185 if (signer != NULL) { 186 if ((r = signer(key, &sig, &slen, 187 sshbuf_ptr(tosign), sshbuf_len(tosign), 188 sign_alg, sk_provider, sk_pin, 0, signer_ctx)) != 0) { 189 error_r(r, "Couldn't sign message (signer)"); 190 goto done; 191 } 192 } else { 193 if ((r = sshkey_sign(key, &sig, &slen, 194 sshbuf_ptr(tosign), sshbuf_len(tosign), 195 sign_alg, sk_provider, sk_pin, 0)) != 0) { 196 error_r(r, "Couldn't sign message"); 197 goto done; 198 } 199 } 200 201 if ((r = sshbuf_put(blob, MAGIC_PREAMBLE, MAGIC_PREAMBLE_LEN)) != 0 || 202 (r = sshbuf_put_u32(blob, SIG_VERSION)) != 0 || 203 (r = sshkey_puts(key, blob)) != 0 || 204 (r = sshbuf_put_cstring(blob, sig_namespace)) != 0 || 205 (r = sshbuf_put_string(blob, NULL, 0)) != 0 || /* reserved */ 206 (r = sshbuf_put_cstring(blob, hashalg)) != 0 || 207 (r = sshbuf_put_string(blob, sig, slen)) != 0) { 208 error_fr(r, "assemble signature object"); 209 goto done; 210 } 211 212 if (out != NULL) { 213 *out = blob; 214 blob = NULL; 215 } 216 r = 0; 217 done: 218 free(sig); 219 sshbuf_free(blob); 220 sshbuf_free(tosign); 221 return r; 222 } 223 224 /* Check preamble and version. */ 225 static int 226 sshsig_parse_preamble(struct sshbuf *buf) 227 { 228 int r = SSH_ERR_INTERNAL_ERROR; 229 uint32_t sversion; 230 231 if ((r = sshbuf_cmp(buf, 0, MAGIC_PREAMBLE, MAGIC_PREAMBLE_LEN)) != 0 || 232 (r = sshbuf_consume(buf, (sizeof(MAGIC_PREAMBLE)-1))) != 0 || 233 (r = sshbuf_get_u32(buf, &sversion)) != 0) { 234 error("Couldn't verify signature: invalid format"); 235 return r; 236 } 237 238 if (sversion > SIG_VERSION) { 239 error("Signature version %lu is larger than supported " 240 "version %u", (unsigned long)sversion, SIG_VERSION); 241 return SSH_ERR_INVALID_FORMAT; 242 } 243 return 0; 244 } 245 246 static int 247 sshsig_check_hashalg(const char *hashalg) 248 { 249 if (hashalg == NULL || 250 match_pattern_list(hashalg, HASHALG_ALLOWED, 0) == 1) 251 return 0; 252 error_f("unsupported hash algorithm \"%.100s\"", hashalg); 253 return SSH_ERR_SIGN_ALG_UNSUPPORTED; 254 } 255 256 static int 257 sshsig_peek_hashalg(struct sshbuf *signature, char **hashalgp) 258 { 259 struct sshbuf *buf = NULL; 260 char *hashalg = NULL; 261 int r = SSH_ERR_INTERNAL_ERROR; 262 263 if (hashalgp != NULL) 264 *hashalgp = NULL; 265 if ((buf = sshbuf_fromb(signature)) == NULL) 266 return SSH_ERR_ALLOC_FAIL; 267 if ((r = sshsig_parse_preamble(buf)) != 0) 268 goto done; 269 if ((r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0 || 270 (r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0 || 271 (r = sshbuf_get_string(buf, NULL, NULL)) != 0 || 272 (r = sshbuf_get_cstring(buf, &hashalg, NULL)) != 0 || 273 (r = sshbuf_get_string_direct(buf, NULL, NULL)) != 0) { 274 error_fr(r, "parse signature object"); 275 goto done; 276 } 277 278 /* success */ 279 r = 0; 280 *hashalgp = hashalg; 281 hashalg = NULL; 282 done: 283 free(hashalg); 284 sshbuf_free(buf); 285 return r; 286 } 287 288 static int 289 sshsig_wrap_verify(struct sshbuf *signature, const char *hashalg, 290 const struct sshbuf *h_message, const char *expect_namespace, 291 struct sshkey **sign_keyp, struct sshkey_sig_details **sig_details) 292 { 293 int r = SSH_ERR_INTERNAL_ERROR; 294 struct sshbuf *buf = NULL, *toverify = NULL; 295 struct sshkey *key = NULL; 296 const u_char *sig; 297 char *got_namespace = NULL, *sigtype = NULL, *sig_hashalg = NULL; 298 size_t siglen; 299 300 debug_f("verify message length %zu", sshbuf_len(h_message)); 301 if (sig_details != NULL) 302 *sig_details = NULL; 303 if (sign_keyp != NULL) 304 *sign_keyp = NULL; 305 306 if ((toverify = sshbuf_new()) == NULL) { 307 error_f("sshbuf_new failed"); 308 r = SSH_ERR_ALLOC_FAIL; 309 goto done; 310 } 311 if ((r = sshbuf_put(toverify, MAGIC_PREAMBLE, 312 MAGIC_PREAMBLE_LEN)) != 0 || 313 (r = sshbuf_put_cstring(toverify, expect_namespace)) != 0 || 314 (r = sshbuf_put_string(toverify, NULL, 0)) != 0 || /* reserved */ 315 (r = sshbuf_put_cstring(toverify, hashalg)) != 0 || 316 (r = sshbuf_put_stringb(toverify, h_message)) != 0) { 317 error_fr(r, "assemble message to verify"); 318 goto done; 319 } 320 321 if ((r = sshsig_parse_preamble(signature)) != 0) 322 goto done; 323 324 if ((r = sshkey_froms(signature, &key)) != 0 || 325 (r = sshbuf_get_cstring(signature, &got_namespace, NULL)) != 0 || 326 (r = sshbuf_get_string(signature, NULL, NULL)) != 0 || 327 (r = sshbuf_get_cstring(signature, &sig_hashalg, NULL)) != 0 || 328 (r = sshbuf_get_string_direct(signature, &sig, &siglen)) != 0) { 329 error_fr(r, "parse signature object"); 330 goto done; 331 } 332 333 if (sshbuf_len(signature) != 0) { 334 error("Signature contains trailing data"); 335 r = SSH_ERR_INVALID_FORMAT; 336 goto done; 337 } 338 339 if (strcmp(expect_namespace, got_namespace) != 0) { 340 error("Couldn't verify signature: namespace does not match"); 341 debug_f("expected namespace \"%s\" received \"%s\"", 342 expect_namespace, got_namespace); 343 r = SSH_ERR_SIGNATURE_INVALID; 344 goto done; 345 } 346 if (strcmp(hashalg, sig_hashalg) != 0) { 347 error("Couldn't verify signature: hash algorithm mismatch"); 348 debug_f("expected algorithm \"%s\" received \"%s\"", 349 hashalg, sig_hashalg); 350 r = SSH_ERR_SIGNATURE_INVALID; 351 goto done; 352 } 353 /* Ensure that RSA keys use an acceptable signature algorithm */ 354 if (sshkey_type_plain(key->type) == KEY_RSA) { 355 if ((r = sshkey_get_sigtype(sig, siglen, &sigtype)) != 0) { 356 error_r(r, "Couldn't verify signature: unable to get " 357 "signature type"); 358 goto done; 359 } 360 if (match_pattern_list(sigtype, RSA_SIGN_ALLOWED, 0) != 1) { 361 error("Couldn't verify signature: unsupported RSA " 362 "signature algorithm %s", sigtype); 363 r = SSH_ERR_SIGN_ALG_UNSUPPORTED; 364 goto done; 365 } 366 } 367 if ((r = sshkey_verify(key, sig, siglen, sshbuf_ptr(toverify), 368 sshbuf_len(toverify), NULL, 0, sig_details)) != 0) { 369 error_r(r, "Signature verification failed"); 370 goto done; 371 } 372 373 /* success */ 374 r = 0; 375 if (sign_keyp != NULL) { 376 *sign_keyp = key; 377 key = NULL; /* transferred */ 378 } 379 done: 380 free(got_namespace); 381 free(sigtype); 382 free(sig_hashalg); 383 sshbuf_free(buf); 384 sshbuf_free(toverify); 385 sshkey_free(key); 386 return r; 387 } 388 389 static int 390 hash_buffer(const struct sshbuf *m, const char *hashalg, struct sshbuf **bp) 391 { 392 char *hex, hash[SSH_DIGEST_MAX_LENGTH]; 393 int alg, r = SSH_ERR_INTERNAL_ERROR; 394 struct sshbuf *b = NULL; 395 396 *bp = NULL; 397 memset(hash, 0, sizeof(hash)); 398 399 if ((r = sshsig_check_hashalg(hashalg)) != 0) 400 return r; 401 if ((alg = ssh_digest_alg_by_name(hashalg)) == -1) { 402 error_f("can't look up hash algorithm %s", hashalg); 403 return SSH_ERR_INTERNAL_ERROR; 404 } 405 if ((r = ssh_digest_buffer(alg, m, hash, sizeof(hash))) != 0) { 406 error_fr(r, "ssh_digest_buffer"); 407 return r; 408 } 409 if ((hex = tohex(hash, ssh_digest_bytes(alg))) != NULL) { 410 debug3_f("final hash: %s", hex); 411 freezero(hex, strlen(hex)); 412 } 413 if ((b = sshbuf_new()) == NULL) { 414 r = SSH_ERR_ALLOC_FAIL; 415 goto out; 416 } 417 if ((r = sshbuf_put(b, hash, ssh_digest_bytes(alg))) != 0) { 418 error_fr(r, "sshbuf_put"); 419 goto out; 420 } 421 *bp = b; 422 b = NULL; /* transferred */ 423 /* success */ 424 r = 0; 425 out: 426 sshbuf_free(b); 427 explicit_bzero(hash, sizeof(hash)); 428 return r; 429 } 430 431 int 432 sshsig_signb(struct sshkey *key, const char *hashalg, 433 const char *sk_provider, const char *sk_pin, 434 const struct sshbuf *message, const char *sig_namespace, 435 struct sshbuf **out, sshsig_signer *signer, void *signer_ctx) 436 { 437 struct sshbuf *b = NULL; 438 int r = SSH_ERR_INTERNAL_ERROR; 439 440 if (hashalg == NULL) 441 hashalg = HASHALG_DEFAULT; 442 if (out != NULL) 443 *out = NULL; 444 if ((r = hash_buffer(message, hashalg, &b)) != 0) { 445 error_fr(r, "hash buffer"); 446 goto out; 447 } 448 if ((r = sshsig_wrap_sign(key, hashalg, sk_provider, sk_pin, b, 449 sig_namespace, out, signer, signer_ctx)) != 0) 450 goto out; 451 /* success */ 452 r = 0; 453 out: 454 sshbuf_free(b); 455 return r; 456 } 457 458 int 459 sshsig_verifyb(struct sshbuf *signature, const struct sshbuf *message, 460 const char *expect_namespace, struct sshkey **sign_keyp, 461 struct sshkey_sig_details **sig_details) 462 { 463 struct sshbuf *b = NULL; 464 int r = SSH_ERR_INTERNAL_ERROR; 465 char *hashalg = NULL; 466 467 if (sig_details != NULL) 468 *sig_details = NULL; 469 if (sign_keyp != NULL) 470 *sign_keyp = NULL; 471 if ((r = sshsig_peek_hashalg(signature, &hashalg)) != 0) 472 return r; 473 debug_f("signature made with hash \"%s\"", hashalg); 474 if ((r = hash_buffer(message, hashalg, &b)) != 0) { 475 error_fr(r, "hash buffer"); 476 goto out; 477 } 478 if ((r = sshsig_wrap_verify(signature, hashalg, b, expect_namespace, 479 sign_keyp, sig_details)) != 0) 480 goto out; 481 /* success */ 482 r = 0; 483 out: 484 sshbuf_free(b); 485 free(hashalg); 486 return r; 487 } 488 489 static int 490 hash_file(int fd, const char *hashalg, struct sshbuf **bp) 491 { 492 char *hex, rbuf[8192], hash[SSH_DIGEST_MAX_LENGTH]; 493 ssize_t n, total = 0; 494 struct ssh_digest_ctx *ctx = NULL; 495 int alg, oerrno, r = SSH_ERR_INTERNAL_ERROR; 496 struct sshbuf *b = NULL; 497 498 *bp = NULL; 499 memset(hash, 0, sizeof(hash)); 500 501 if ((r = sshsig_check_hashalg(hashalg)) != 0) 502 return r; 503 if ((alg = ssh_digest_alg_by_name(hashalg)) == -1) { 504 error_f("can't look up hash algorithm %s", hashalg); 505 return SSH_ERR_INTERNAL_ERROR; 506 } 507 if ((ctx = ssh_digest_start(alg)) == NULL) { 508 error_f("ssh_digest_start failed"); 509 return SSH_ERR_INTERNAL_ERROR; 510 } 511 for (;;) { 512 if ((n = read(fd, rbuf, sizeof(rbuf))) == -1) { 513 if (errno == EINTR || errno == EAGAIN) 514 continue; 515 oerrno = errno; 516 error_f("read: %s", strerror(errno)); 517 errno = oerrno; 518 r = SSH_ERR_SYSTEM_ERROR; 519 goto out; 520 } else if (n == 0) { 521 debug2_f("hashed %zu bytes", total); 522 break; /* EOF */ 523 } 524 total += (size_t)n; 525 if ((r = ssh_digest_update(ctx, rbuf, (size_t)n)) != 0) { 526 error_fr(r, "ssh_digest_update"); 527 goto out; 528 } 529 } 530 if ((r = ssh_digest_final(ctx, hash, sizeof(hash))) != 0) { 531 error_fr(r, "ssh_digest_final"); 532 goto out; 533 } 534 if ((hex = tohex(hash, ssh_digest_bytes(alg))) != NULL) { 535 debug3_f("final hash: %s", hex); 536 freezero(hex, strlen(hex)); 537 } 538 if ((b = sshbuf_new()) == NULL) { 539 r = SSH_ERR_ALLOC_FAIL; 540 goto out; 541 } 542 if ((r = sshbuf_put(b, hash, ssh_digest_bytes(alg))) != 0) { 543 error_fr(r, "sshbuf_put"); 544 goto out; 545 } 546 *bp = b; 547 b = NULL; /* transferred */ 548 /* success */ 549 r = 0; 550 out: 551 oerrno = errno; 552 sshbuf_free(b); 553 ssh_digest_free(ctx); 554 explicit_bzero(hash, sizeof(hash)); 555 errno = oerrno; 556 return r; 557 } 558 559 int 560 sshsig_sign_fd(struct sshkey *key, const char *hashalg, 561 const char *sk_provider, const char *sk_pin, 562 int fd, const char *sig_namespace, struct sshbuf **out, 563 sshsig_signer *signer, void *signer_ctx) 564 { 565 struct sshbuf *b = NULL; 566 int r = SSH_ERR_INTERNAL_ERROR; 567 568 if (hashalg == NULL) 569 hashalg = HASHALG_DEFAULT; 570 if (out != NULL) 571 *out = NULL; 572 if ((r = hash_file(fd, hashalg, &b)) != 0) { 573 error_fr(r, "hash_file"); 574 return r; 575 } 576 if ((r = sshsig_wrap_sign(key, hashalg, sk_provider, sk_pin, b, 577 sig_namespace, out, signer, signer_ctx)) != 0) 578 goto out; 579 /* success */ 580 r = 0; 581 out: 582 sshbuf_free(b); 583 return r; 584 } 585 586 int 587 sshsig_verify_fd(struct sshbuf *signature, int fd, 588 const char *expect_namespace, struct sshkey **sign_keyp, 589 struct sshkey_sig_details **sig_details) 590 { 591 struct sshbuf *b = NULL; 592 int r = SSH_ERR_INTERNAL_ERROR; 593 char *hashalg = NULL; 594 595 if (sig_details != NULL) 596 *sig_details = NULL; 597 if (sign_keyp != NULL) 598 *sign_keyp = NULL; 599 if ((r = sshsig_peek_hashalg(signature, &hashalg)) != 0) 600 return r; 601 debug_f("signature made with hash \"%s\"", hashalg); 602 if ((r = hash_file(fd, hashalg, &b)) != 0) { 603 error_fr(r, "hash_file"); 604 goto out; 605 } 606 if ((r = sshsig_wrap_verify(signature, hashalg, b, expect_namespace, 607 sign_keyp, sig_details)) != 0) 608 goto out; 609 /* success */ 610 r = 0; 611 out: 612 sshbuf_free(b); 613 free(hashalg); 614 return r; 615 } 616 617 struct sshsigopt { 618 int ca; 619 char *namespaces; 620 uint64_t valid_after, valid_before; 621 }; 622 623 struct sshsigopt * 624 sshsigopt_parse(const char *opts, const char *path, u_long linenum, 625 const char **errstrp) 626 { 627 struct sshsigopt *ret; 628 int r; 629 char *opt; 630 const char *errstr = NULL; 631 632 if ((ret = calloc(1, sizeof(*ret))) == NULL) 633 return NULL; 634 if (opts == NULL || *opts == '\0') 635 return ret; /* Empty options yields empty options :) */ 636 637 while (*opts && *opts != ' ' && *opts != '\t') { 638 /* flag options */ 639 if ((r = opt_flag("cert-authority", 0, &opts)) != -1) { 640 ret->ca = 1; 641 } else if (opt_match(&opts, "namespaces")) { 642 if (ret->namespaces != NULL) { 643 errstr = "multiple \"namespaces\" clauses"; 644 goto fail; 645 } 646 ret->namespaces = opt_dequote(&opts, &errstr); 647 if (ret->namespaces == NULL) 648 goto fail; 649 } else if (opt_match(&opts, "valid-after")) { 650 if (ret->valid_after != 0) { 651 errstr = "multiple \"valid-after\" clauses"; 652 goto fail; 653 } 654 if ((opt = opt_dequote(&opts, &errstr)) == NULL) 655 goto fail; 656 if (parse_absolute_time(opt, &ret->valid_after) != 0 || 657 ret->valid_after == 0) { 658 free(opt); 659 errstr = "invalid \"valid-after\" time"; 660 goto fail; 661 } 662 free(opt); 663 } else if (opt_match(&opts, "valid-before")) { 664 if (ret->valid_before != 0) { 665 errstr = "multiple \"valid-before\" clauses"; 666 goto fail; 667 } 668 if ((opt = opt_dequote(&opts, &errstr)) == NULL) 669 goto fail; 670 if (parse_absolute_time(opt, &ret->valid_before) != 0 || 671 ret->valid_before == 0) { 672 free(opt); 673 errstr = "invalid \"valid-before\" time"; 674 goto fail; 675 } 676 free(opt); 677 } 678 /* 679 * Skip the comma, and move to the next option 680 * (or break out if there are no more). 681 */ 682 if (*opts == '\0' || *opts == ' ' || *opts == '\t') 683 break; /* End of options. */ 684 /* Anything other than a comma is an unknown option */ 685 if (*opts != ',') { 686 errstr = "unknown key option"; 687 goto fail; 688 } 689 opts++; 690 if (*opts == '\0') { 691 errstr = "unexpected end-of-options"; 692 goto fail; 693 } 694 } 695 /* final consistency check */ 696 if (ret->valid_after != 0 && ret->valid_before != 0 && 697 ret->valid_before <= ret->valid_after) { 698 errstr = "\"valid-before\" time is before \"valid-after\""; 699 goto fail; 700 } 701 /* success */ 702 return ret; 703 fail: 704 if (errstrp != NULL) 705 *errstrp = errstr; 706 sshsigopt_free(ret); 707 return NULL; 708 } 709 710 void 711 sshsigopt_free(struct sshsigopt *opts) 712 { 713 if (opts == NULL) 714 return; 715 free(opts->namespaces); 716 free(opts); 717 } 718 719 static int 720 parse_principals_key_and_options(const char *path, u_long linenum, char *line, 721 const char *required_principal, char **principalsp, struct sshkey **keyp, 722 struct sshsigopt **sigoptsp) 723 { 724 char *opts = NULL, *tmp, *cp, *principals = NULL; 725 const char *reason = NULL; 726 struct sshsigopt *sigopts = NULL; 727 struct sshkey *key = NULL; 728 int r = SSH_ERR_INTERNAL_ERROR; 729 730 if (principalsp != NULL) 731 *principalsp = NULL; 732 if (sigoptsp != NULL) 733 *sigoptsp = NULL; 734 if (keyp != NULL) 735 *keyp = NULL; 736 737 cp = line; 738 cp = cp + strspn(cp, " \t"); /* skip leading whitespace */ 739 if (*cp == '#' || *cp == '\0') 740 return SSH_ERR_KEY_NOT_FOUND; /* blank or all-comment line */ 741 742 /* format: identity[,identity...] [option[,option...]] key */ 743 if ((tmp = strdelimw(&cp)) == NULL || cp == NULL) { 744 error("%s:%lu: invalid line", path, linenum); 745 r = SSH_ERR_INVALID_FORMAT; 746 goto out; 747 } 748 if ((principals = strdup(tmp)) == NULL) { 749 error_f("strdup failed"); 750 r = SSH_ERR_ALLOC_FAIL; 751 goto out; 752 } 753 /* 754 * Bail out early if we're looking for a particular principal and this 755 * line does not list it. 756 */ 757 if (required_principal != NULL) { 758 if (match_pattern_list(required_principal, 759 principals, 0) != 1) { 760 /* principal didn't match */ 761 r = SSH_ERR_KEY_NOT_FOUND; 762 goto out; 763 } 764 debug_f("%s:%lu: matched principal \"%s\"", 765 path, linenum, required_principal); 766 } 767 768 if ((key = sshkey_new(KEY_UNSPEC)) == NULL) { 769 error_f("sshkey_new failed"); 770 r = SSH_ERR_ALLOC_FAIL; 771 goto out; 772 } 773 if (sshkey_read(key, &cp) != 0) { 774 /* no key? Check for options */ 775 opts = cp; 776 if (sshkey_advance_past_options(&cp) != 0) { 777 error("%s:%lu: invalid options", path, linenum); 778 r = SSH_ERR_INVALID_FORMAT; 779 goto out; 780 } 781 if (cp == NULL || *cp == '\0') { 782 error("%s:%lu: missing key", path, linenum); 783 r = SSH_ERR_INVALID_FORMAT; 784 goto out; 785 } 786 *cp++ = '\0'; 787 skip_space(&cp); 788 if (sshkey_read(key, &cp) != 0) { 789 error("%s:%lu: invalid key", path, linenum); 790 r = SSH_ERR_INVALID_FORMAT; 791 goto out; 792 } 793 } 794 debug3("%s:%lu: options %s", path, linenum, opts == NULL ? "" : opts); 795 if ((sigopts = sshsigopt_parse(opts, path, linenum, &reason)) == NULL) { 796 error("%s:%lu: bad options: %s", path, linenum, reason); 797 r = SSH_ERR_INVALID_FORMAT; 798 goto out; 799 } 800 /* success */ 801 if (principalsp != NULL) { 802 *principalsp = principals; 803 principals = NULL; /* transferred */ 804 } 805 if (sigoptsp != NULL) { 806 *sigoptsp = sigopts; 807 sigopts = NULL; /* transferred */ 808 } 809 if (keyp != NULL) { 810 *keyp = key; 811 key = NULL; /* transferred */ 812 } 813 r = 0; 814 out: 815 free(principals); 816 sshsigopt_free(sigopts); 817 sshkey_free(key); 818 return r; 819 } 820 821 static int 822 cert_filter_principals(const char *path, u_long linenum, 823 char **principalsp, const struct sshkey *cert, uint64_t verify_time) 824 { 825 char *cp, *oprincipals, *principals; 826 const char *reason; 827 struct sshbuf *nprincipals; 828 int r = SSH_ERR_INTERNAL_ERROR, success = 0; 829 u_int i; 830 831 oprincipals = principals = *principalsp; 832 *principalsp = NULL; 833 834 if ((nprincipals = sshbuf_new()) == NULL) { 835 r = SSH_ERR_ALLOC_FAIL; 836 goto out; 837 } 838 839 while ((cp = strsep(&principals, ",")) != NULL && *cp != '\0') { 840 /* Check certificate validity */ 841 if ((r = sshkey_cert_check_authority(cert, 0, 1, 0, 842 verify_time, NULL, &reason)) != 0) { 843 debug("%s:%lu: principal \"%s\" not authorized: %s", 844 path, linenum, cp, reason); 845 continue; 846 } 847 /* Return all matching principal names from the cert */ 848 for (i = 0; i < cert->cert->nprincipals; i++) { 849 if (match_pattern(cert->cert->principals[i], cp)) { 850 if ((r = sshbuf_putf(nprincipals, "%s%s", 851 sshbuf_len(nprincipals) != 0 ? "," : "", 852 cert->cert->principals[i])) != 0) { 853 error_f("buffer error"); 854 goto out; 855 } 856 } 857 } 858 } 859 if (sshbuf_len(nprincipals) == 0) { 860 error("%s:%lu: no valid principals found", path, linenum); 861 r = SSH_ERR_KEY_CERT_INVALID; 862 goto out; 863 } 864 if ((principals = sshbuf_dup_string(nprincipals)) == NULL) { 865 error_f("buffer error"); 866 goto out; 867 } 868 /* success */ 869 success = 1; 870 *principalsp = principals; 871 out: 872 sshbuf_free(nprincipals); 873 free(oprincipals); 874 return success ? 0 : r; 875 } 876 877 static int 878 check_allowed_keys_line(const char *path, u_long linenum, char *line, 879 const struct sshkey *sign_key, const char *principal, 880 const char *sig_namespace, uint64_t verify_time, char **principalsp) 881 { 882 struct sshkey *found_key = NULL; 883 char *principals = NULL; 884 int r, success = 0; 885 const char *reason = NULL; 886 struct sshsigopt *sigopts = NULL; 887 char tvalid[64], tverify[64]; 888 889 if (principalsp != NULL) 890 *principalsp = NULL; 891 892 /* Parse the line */ 893 if ((r = parse_principals_key_and_options(path, linenum, line, 894 principal, &principals, &found_key, &sigopts)) != 0) { 895 /* error already logged */ 896 goto done; 897 } 898 899 if (!sigopts->ca && sshkey_equal(found_key, sign_key)) { 900 /* Exact match of key */ 901 debug("%s:%lu: matched key", path, linenum); 902 } else if (sigopts->ca && sshkey_is_cert(sign_key) && 903 sshkey_equal_public(sign_key->cert->signature_key, found_key)) { 904 if (principal) { 905 /* Match certificate CA key with specified principal */ 906 if ((r = sshkey_cert_check_authority(sign_key, 0, 1, 0, 907 verify_time, principal, &reason)) != 0) { 908 error("%s:%lu: certificate not authorized: %s", 909 path, linenum, reason); 910 goto done; 911 } 912 debug("%s:%lu: matched certificate CA key", 913 path, linenum); 914 } else { 915 /* No principal specified - find all matching ones */ 916 if ((r = cert_filter_principals(path, linenum, 917 &principals, sign_key, verify_time)) != 0) { 918 /* error already displayed */ 919 debug_r(r, "%s:%lu: cert_filter_principals", 920 path, linenum); 921 goto done; 922 } 923 debug("%s:%lu: matched certificate CA key", 924 path, linenum); 925 } 926 } else { 927 /* Didn't match key */ 928 goto done; 929 } 930 931 /* Check whether options preclude the use of this key */ 932 if (sigopts->namespaces != NULL && sig_namespace != NULL && 933 match_pattern_list(sig_namespace, sigopts->namespaces, 0) != 1) { 934 error("%s:%lu: key is not permitted for use in signature " 935 "namespace \"%s\"", path, linenum, sig_namespace); 936 goto done; 937 } 938 939 /* check key time validity */ 940 format_absolute_time((uint64_t)verify_time, tverify, sizeof(tverify)); 941 if (sigopts->valid_after != 0 && 942 (uint64_t)verify_time < sigopts->valid_after) { 943 format_absolute_time(sigopts->valid_after, 944 tvalid, sizeof(tvalid)); 945 error("%s:%lu: key is not yet valid: " 946 "verify time %s < valid-after %s", path, linenum, 947 tverify, tvalid); 948 goto done; 949 } 950 if (sigopts->valid_before != 0 && 951 (uint64_t)verify_time > sigopts->valid_before) { 952 format_absolute_time(sigopts->valid_before, 953 tvalid, sizeof(tvalid)); 954 error("%s:%lu: key has expired: " 955 "verify time %s > valid-before %s", path, linenum, 956 tverify, tvalid); 957 goto done; 958 } 959 success = 1; 960 961 done: 962 if (success && principalsp != NULL) { 963 *principalsp = principals; 964 principals = NULL; /* transferred */ 965 } 966 free(principals); 967 sshkey_free(found_key); 968 sshsigopt_free(sigopts); 969 return success ? 0 : SSH_ERR_KEY_NOT_FOUND; 970 } 971 972 int 973 sshsig_check_allowed_keys(const char *path, const struct sshkey *sign_key, 974 const char *principal, const char *sig_namespace, uint64_t verify_time) 975 { 976 FILE *f = NULL; 977 char *line = NULL; 978 size_t linesize = 0; 979 u_long linenum = 0; 980 int r = SSH_ERR_INTERNAL_ERROR, oerrno; 981 982 /* Check key and principal against file */ 983 if ((f = fopen(path, "r")) == NULL) { 984 oerrno = errno; 985 error("Unable to open allowed keys file \"%s\": %s", 986 path, strerror(errno)); 987 errno = oerrno; 988 return SSH_ERR_SYSTEM_ERROR; 989 } 990 991 while (getline(&line, &linesize, f) != -1) { 992 linenum++; 993 r = check_allowed_keys_line(path, linenum, line, sign_key, 994 principal, sig_namespace, verify_time, NULL); 995 free(line); 996 line = NULL; 997 linesize = 0; 998 if (r == SSH_ERR_KEY_NOT_FOUND) 999 continue; 1000 else if (r == 0) { 1001 /* success */ 1002 fclose(f); 1003 return 0; 1004 } else 1005 break; 1006 } 1007 /* Either we hit an error parsing or we simply didn't find the key */ 1008 fclose(f); 1009 free(line); 1010 return r == 0 ? SSH_ERR_KEY_NOT_FOUND : r; 1011 } 1012 1013 int 1014 sshsig_find_principals(const char *path, const struct sshkey *sign_key, 1015 uint64_t verify_time, char **principals) 1016 { 1017 FILE *f = NULL; 1018 char *line = NULL; 1019 size_t linesize = 0; 1020 u_long linenum = 0; 1021 int r = SSH_ERR_INTERNAL_ERROR, oerrno; 1022 1023 if ((f = fopen(path, "r")) == NULL) { 1024 oerrno = errno; 1025 error("Unable to open allowed keys file \"%s\": %s", 1026 path, strerror(errno)); 1027 errno = oerrno; 1028 return SSH_ERR_SYSTEM_ERROR; 1029 } 1030 1031 r = SSH_ERR_KEY_NOT_FOUND; 1032 while (getline(&line, &linesize, f) != -1) { 1033 linenum++; 1034 r = check_allowed_keys_line(path, linenum, line, 1035 sign_key, NULL, NULL, verify_time, principals); 1036 free(line); 1037 line = NULL; 1038 linesize = 0; 1039 if (r == SSH_ERR_KEY_NOT_FOUND) 1040 continue; 1041 else if (r == 0) { 1042 /* success */ 1043 fclose(f); 1044 return 0; 1045 } else 1046 break; 1047 } 1048 free(line); 1049 /* Either we hit an error parsing or we simply didn't find the key */ 1050 if (ferror(f) != 0) { 1051 oerrno = errno; 1052 fclose(f); 1053 error("Unable to read allowed keys file \"%s\": %s", 1054 path, strerror(errno)); 1055 errno = oerrno; 1056 return SSH_ERR_SYSTEM_ERROR; 1057 } 1058 fclose(f); 1059 return r == 0 ? SSH_ERR_KEY_NOT_FOUND : r; 1060 } 1061 1062 int 1063 sshsig_match_principals(const char *path, const char *principal, 1064 char ***principalsp, size_t *nprincipalsp) 1065 { 1066 FILE *f = NULL; 1067 char *found, *line = NULL, **principals = NULL, **tmp; 1068 size_t i, nprincipals = 0, linesize = 0; 1069 u_long linenum = 0; 1070 int oerrno = 0, r, ret = 0; 1071 1072 if (principalsp != NULL) 1073 *principalsp = NULL; 1074 if (nprincipalsp != NULL) 1075 *nprincipalsp = 0; 1076 1077 /* Check key and principal against file */ 1078 if ((f = fopen(path, "r")) == NULL) { 1079 oerrno = errno; 1080 error("Unable to open allowed keys file \"%s\": %s", 1081 path, strerror(errno)); 1082 errno = oerrno; 1083 return SSH_ERR_SYSTEM_ERROR; 1084 } 1085 1086 while (getline(&line, &linesize, f) != -1) { 1087 linenum++; 1088 /* Parse the line */ 1089 if ((r = parse_principals_key_and_options(path, linenum, line, 1090 principal, &found, NULL, NULL)) != 0) { 1091 if (r == SSH_ERR_KEY_NOT_FOUND) 1092 continue; 1093 ret = r; 1094 oerrno = errno; 1095 break; /* unexpected error */ 1096 } 1097 if ((tmp = recallocarray(principals, nprincipals, 1098 nprincipals + 1, sizeof(*principals))) == NULL) { 1099 ret = SSH_ERR_ALLOC_FAIL; 1100 free(found); 1101 break; 1102 } 1103 principals = tmp; 1104 principals[nprincipals++] = found; /* transferred */ 1105 free(line); 1106 line = NULL; 1107 linesize = 0; 1108 } 1109 fclose(f); 1110 1111 if (ret == 0) { 1112 if (nprincipals == 0) 1113 ret = SSH_ERR_KEY_NOT_FOUND; 1114 if (principalsp != NULL) { 1115 *principalsp = principals; 1116 principals = NULL; /* transferred */ 1117 } 1118 if (nprincipalsp != 0) { 1119 *nprincipalsp = nprincipals; 1120 nprincipals = 0; 1121 } 1122 } 1123 1124 for (i = 0; i < nprincipals; i++) 1125 free(principals[i]); 1126 free(principals); 1127 1128 errno = oerrno; 1129 return ret; 1130 } 1131 1132 int 1133 sshsig_get_pubkey(struct sshbuf *signature, struct sshkey **pubkey) 1134 { 1135 struct sshkey *pk = NULL; 1136 int r = SSH_ERR_SIGNATURE_INVALID; 1137 1138 if (pubkey == NULL) 1139 return SSH_ERR_INTERNAL_ERROR; 1140 if ((r = sshsig_parse_preamble(signature)) != 0) 1141 return r; 1142 if ((r = sshkey_froms(signature, &pk)) != 0) 1143 return r; 1144 1145 *pubkey = pk; 1146 pk = NULL; 1147 return 0; 1148 } 1149