1 /* $OpenBSD: authfile.c,v 1.76 2006/08/03 03:34:41 deraadt Exp $ */ 2 /* 3 * Author: Tatu Ylonen <ylo@cs.hut.fi> 4 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 5 * All rights reserved 6 * This file contains functions for reading and writing identity files, and 7 * for reading the passphrase from the user. 8 * 9 * As far as I am concerned, the code I have written for this software 10 * can be used freely for any purpose. Any derived versions of this 11 * software must be clearly marked as such, and if the derived work is 12 * incompatible with the protocol description in the RFC file, it must be 13 * called by a name other than "ssh" or "Secure Shell". 14 * 15 * 16 * Copyright (c) 2000 Markus Friedl. All rights reserved. 17 * 18 * Redistribution and use in source and binary forms, with or without 19 * modification, are permitted provided that the following conditions 20 * are met: 21 * 1. Redistributions of source code must retain the above copyright 22 * notice, this list of conditions and the following disclaimer. 23 * 2. Redistributions in binary form must reproduce the above copyright 24 * notice, this list of conditions and the following disclaimer in the 25 * documentation and/or other materials provided with the distribution. 26 * 27 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 28 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 29 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 30 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 31 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 32 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 33 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 34 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 35 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 36 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 37 */ 38 39 #include "includes.h" 40 41 #include <sys/types.h> 42 #include <sys/stat.h> 43 #include <sys/param.h> 44 #include <sys/uio.h> 45 46 #include <openssl/err.h> 47 #include <openssl/evp.h> 48 #include <openssl/pem.h> 49 50 #include <errno.h> 51 #include <fcntl.h> 52 #include <stdarg.h> 53 #include <stdio.h> 54 #include <stdlib.h> 55 #include <string.h> 56 #include <unistd.h> 57 58 #include "xmalloc.h" 59 #include "cipher.h" 60 #include "buffer.h" 61 #include "key.h" 62 #include "ssh.h" 63 #include "log.h" 64 #include "authfile.h" 65 #include "rsa.h" 66 #include "misc.h" 67 #include "atomicio.h" 68 69 /* Version identification string for SSH v1 identity files. */ 70 static const char authfile_id_string[] = 71 "SSH PRIVATE KEY FILE FORMAT 1.1\n"; 72 73 /* 74 * Saves the authentication (private) key in a file, encrypting it with 75 * passphrase. The identification of the file (lowest 64 bits of n) will 76 * precede the key to provide identification of the key without needing a 77 * passphrase. 78 */ 79 80 static int 81 key_save_private_rsa1(Key *key, const char *filename, const char *passphrase, 82 const char *comment) 83 { 84 Buffer buffer, encrypted; 85 u_char buf[100], *cp; 86 int fd, i, cipher_num; 87 CipherContext ciphercontext; 88 Cipher *cipher; 89 u_int32_t rnd; 90 91 /* 92 * If the passphrase is empty, use SSH_CIPHER_NONE to ease converting 93 * to another cipher; otherwise use SSH_AUTHFILE_CIPHER. 94 */ 95 cipher_num = (strcmp(passphrase, "") == 0) ? 96 SSH_CIPHER_NONE : SSH_AUTHFILE_CIPHER; 97 if ((cipher = cipher_by_number(cipher_num)) == NULL) 98 fatal("save_private_key_rsa: bad cipher"); 99 100 /* This buffer is used to built the secret part of the private key. */ 101 buffer_init(&buffer); 102 103 /* Put checkbytes for checking passphrase validity. */ 104 rnd = arc4random(); 105 buf[0] = rnd & 0xff; 106 buf[1] = (rnd >> 8) & 0xff; 107 buf[2] = buf[0]; 108 buf[3] = buf[1]; 109 buffer_append(&buffer, buf, 4); 110 111 /* 112 * Store the private key (n and e will not be stored because they 113 * will be stored in plain text, and storing them also in encrypted 114 * format would just give known plaintext). 115 */ 116 buffer_put_bignum(&buffer, key->rsa->d); 117 buffer_put_bignum(&buffer, key->rsa->iqmp); 118 buffer_put_bignum(&buffer, key->rsa->q); /* reverse from SSL p */ 119 buffer_put_bignum(&buffer, key->rsa->p); /* reverse from SSL q */ 120 121 /* Pad the part to be encrypted until its size is a multiple of 8. */ 122 while (buffer_len(&buffer) % 8 != 0) 123 buffer_put_char(&buffer, 0); 124 125 /* This buffer will be used to contain the data in the file. */ 126 buffer_init(&encrypted); 127 128 /* First store keyfile id string. */ 129 for (i = 0; authfile_id_string[i]; i++) 130 buffer_put_char(&encrypted, authfile_id_string[i]); 131 buffer_put_char(&encrypted, 0); 132 133 /* Store cipher type. */ 134 buffer_put_char(&encrypted, cipher_num); 135 buffer_put_int(&encrypted, 0); /* For future extension */ 136 137 /* Store public key. This will be in plain text. */ 138 buffer_put_int(&encrypted, BN_num_bits(key->rsa->n)); 139 buffer_put_bignum(&encrypted, key->rsa->n); 140 buffer_put_bignum(&encrypted, key->rsa->e); 141 buffer_put_cstring(&encrypted, comment); 142 143 /* Allocate space for the private part of the key in the buffer. */ 144 cp = buffer_append_space(&encrypted, buffer_len(&buffer)); 145 146 cipher_set_key_string(&ciphercontext, cipher, passphrase, 147 CIPHER_ENCRYPT); 148 cipher_crypt(&ciphercontext, cp, 149 buffer_ptr(&buffer), buffer_len(&buffer)); 150 cipher_cleanup(&ciphercontext); 151 memset(&ciphercontext, 0, sizeof(ciphercontext)); 152 153 /* Destroy temporary data. */ 154 memset(buf, 0, sizeof(buf)); 155 buffer_free(&buffer); 156 157 fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600); 158 if (fd < 0) { 159 error("open %s failed: %s.", filename, strerror(errno)); 160 buffer_free(&encrypted); 161 return 0; 162 } 163 if (atomicio(vwrite, fd, buffer_ptr(&encrypted), 164 buffer_len(&encrypted)) != buffer_len(&encrypted)) { 165 error("write to key file %s failed: %s", filename, 166 strerror(errno)); 167 buffer_free(&encrypted); 168 close(fd); 169 unlink(filename); 170 return 0; 171 } 172 close(fd); 173 buffer_free(&encrypted); 174 return 1; 175 } 176 177 /* save SSH v2 key in OpenSSL PEM format */ 178 static int 179 key_save_private_pem(Key *key, const char *filename, const char *_passphrase, 180 const char *comment) 181 { 182 FILE *fp; 183 int fd; 184 int success = 0; 185 int len = strlen(_passphrase); 186 u_char *passphrase = (len > 0) ? (u_char *)_passphrase : NULL; 187 const EVP_CIPHER *cipher = (len > 0) ? EVP_des_ede3_cbc() : NULL; 188 189 if (len > 0 && len <= 4) { 190 error("passphrase too short: have %d bytes, need > 4", len); 191 return 0; 192 } 193 fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600); 194 if (fd < 0) { 195 error("open %s failed: %s.", filename, strerror(errno)); 196 return 0; 197 } 198 fp = fdopen(fd, "w"); 199 if (fp == NULL) { 200 error("fdopen %s failed: %s.", filename, strerror(errno)); 201 close(fd); 202 return 0; 203 } 204 switch (key->type) { 205 case KEY_DSA: 206 success = PEM_write_DSAPrivateKey(fp, key->dsa, 207 cipher, passphrase, len, NULL, NULL); 208 break; 209 case KEY_RSA: 210 success = PEM_write_RSAPrivateKey(fp, key->rsa, 211 cipher, passphrase, len, NULL, NULL); 212 break; 213 } 214 fclose(fp); 215 return success; 216 } 217 218 int 219 key_save_private(Key *key, const char *filename, const char *passphrase, 220 const char *comment) 221 { 222 switch (key->type) { 223 case KEY_RSA1: 224 return key_save_private_rsa1(key, filename, passphrase, 225 comment); 226 case KEY_DSA: 227 case KEY_RSA: 228 return key_save_private_pem(key, filename, passphrase, 229 comment); 230 default: 231 break; 232 } 233 error("key_save_private: cannot save key type %d", key->type); 234 return 0; 235 } 236 237 /* 238 * Loads the public part of the ssh v1 key file. Returns NULL if an error was 239 * encountered (the file does not exist or is not readable), and the key 240 * otherwise. 241 */ 242 243 static Key * 244 key_load_public_rsa1(int fd, const char *filename, char **commentp) 245 { 246 Buffer buffer; 247 Key *pub; 248 struct stat st; 249 char *cp; 250 u_int i; 251 size_t len; 252 253 if (fstat(fd, &st) < 0) { 254 error("fstat for key file %.200s failed: %.100s", 255 filename, strerror(errno)); 256 return NULL; 257 } 258 if (st.st_size > 1*1024*1024) { 259 error("key file %.200s too large", filename); 260 return NULL; 261 } 262 len = (size_t)st.st_size; /* truncated */ 263 264 buffer_init(&buffer); 265 cp = buffer_append_space(&buffer, len); 266 267 if (atomicio(read, fd, cp, len) != len) { 268 debug("Read from key file %.200s failed: %.100s", filename, 269 strerror(errno)); 270 buffer_free(&buffer); 271 return NULL; 272 } 273 274 /* Check that it is at least big enough to contain the ID string. */ 275 if (len < sizeof(authfile_id_string)) { 276 debug3("Not a RSA1 key file %.200s.", filename); 277 buffer_free(&buffer); 278 return NULL; 279 } 280 /* 281 * Make sure it begins with the id string. Consume the id string 282 * from the buffer. 283 */ 284 for (i = 0; i < sizeof(authfile_id_string); i++) 285 if (buffer_get_char(&buffer) != authfile_id_string[i]) { 286 debug3("Not a RSA1 key file %.200s.", filename); 287 buffer_free(&buffer); 288 return NULL; 289 } 290 /* Skip cipher type and reserved data. */ 291 (void) buffer_get_char(&buffer); /* cipher type */ 292 (void) buffer_get_int(&buffer); /* reserved */ 293 294 /* Read the public key from the buffer. */ 295 (void) buffer_get_int(&buffer); 296 pub = key_new(KEY_RSA1); 297 buffer_get_bignum(&buffer, pub->rsa->n); 298 buffer_get_bignum(&buffer, pub->rsa->e); 299 if (commentp) 300 *commentp = buffer_get_string(&buffer, NULL); 301 /* The encrypted private part is not parsed by this function. */ 302 303 buffer_free(&buffer); 304 return pub; 305 } 306 307 /* load public key from private-key file, works only for SSH v1 */ 308 Key * 309 key_load_public_type(int type, const char *filename, char **commentp) 310 { 311 Key *pub; 312 int fd; 313 314 if (type == KEY_RSA1) { 315 fd = open(filename, O_RDONLY); 316 if (fd < 0) 317 return NULL; 318 pub = key_load_public_rsa1(fd, filename, commentp); 319 close(fd); 320 return pub; 321 } 322 return NULL; 323 } 324 325 /* 326 * Loads the private key from the file. Returns 0 if an error is encountered 327 * (file does not exist or is not readable, or passphrase is bad). This 328 * initializes the private key. 329 * Assumes we are called under uid of the owner of the file. 330 */ 331 332 static Key * 333 key_load_private_rsa1(int fd, const char *filename, const char *passphrase, 334 char **commentp) 335 { 336 u_int i; 337 int check1, check2, cipher_type; 338 size_t len; 339 Buffer buffer, decrypted; 340 u_char *cp; 341 CipherContext ciphercontext; 342 Cipher *cipher; 343 Key *prv = NULL; 344 struct stat st; 345 346 if (fstat(fd, &st) < 0) { 347 error("fstat for key file %.200s failed: %.100s", 348 filename, strerror(errno)); 349 close(fd); 350 return NULL; 351 } 352 if (st.st_size > 1*1024*1024) { 353 error("key file %.200s too large", filename); 354 close(fd); 355 return (NULL); 356 } 357 len = (size_t)st.st_size; /* truncated */ 358 359 buffer_init(&buffer); 360 cp = buffer_append_space(&buffer, len); 361 362 if (atomicio(read, fd, cp, len) != len) { 363 debug("Read from key file %.200s failed: %.100s", filename, 364 strerror(errno)); 365 buffer_free(&buffer); 366 close(fd); 367 return NULL; 368 } 369 370 /* Check that it is at least big enough to contain the ID string. */ 371 if (len < sizeof(authfile_id_string)) { 372 debug3("Not a RSA1 key file %.200s.", filename); 373 buffer_free(&buffer); 374 close(fd); 375 return NULL; 376 } 377 /* 378 * Make sure it begins with the id string. Consume the id string 379 * from the buffer. 380 */ 381 for (i = 0; i < sizeof(authfile_id_string); i++) 382 if (buffer_get_char(&buffer) != authfile_id_string[i]) { 383 debug3("Not a RSA1 key file %.200s.", filename); 384 buffer_free(&buffer); 385 close(fd); 386 return NULL; 387 } 388 389 /* Read cipher type. */ 390 cipher_type = buffer_get_char(&buffer); 391 (void) buffer_get_int(&buffer); /* Reserved data. */ 392 393 /* Read the public key from the buffer. */ 394 (void) buffer_get_int(&buffer); 395 prv = key_new_private(KEY_RSA1); 396 397 buffer_get_bignum(&buffer, prv->rsa->n); 398 buffer_get_bignum(&buffer, prv->rsa->e); 399 if (commentp) 400 *commentp = buffer_get_string(&buffer, NULL); 401 else 402 xfree(buffer_get_string(&buffer, NULL)); 403 404 /* Check that it is a supported cipher. */ 405 cipher = cipher_by_number(cipher_type); 406 if (cipher == NULL) { 407 debug("Unsupported cipher %d used in key file %.200s.", 408 cipher_type, filename); 409 buffer_free(&buffer); 410 goto fail; 411 } 412 /* Initialize space for decrypted data. */ 413 buffer_init(&decrypted); 414 cp = buffer_append_space(&decrypted, buffer_len(&buffer)); 415 416 /* Rest of the buffer is encrypted. Decrypt it using the passphrase. */ 417 cipher_set_key_string(&ciphercontext, cipher, passphrase, 418 CIPHER_DECRYPT); 419 cipher_crypt(&ciphercontext, cp, 420 buffer_ptr(&buffer), buffer_len(&buffer)); 421 cipher_cleanup(&ciphercontext); 422 memset(&ciphercontext, 0, sizeof(ciphercontext)); 423 buffer_free(&buffer); 424 425 check1 = buffer_get_char(&decrypted); 426 check2 = buffer_get_char(&decrypted); 427 if (check1 != buffer_get_char(&decrypted) || 428 check2 != buffer_get_char(&decrypted)) { 429 if (strcmp(passphrase, "") != 0) 430 debug("Bad passphrase supplied for key file %.200s.", 431 filename); 432 /* Bad passphrase. */ 433 buffer_free(&decrypted); 434 goto fail; 435 } 436 /* Read the rest of the private key. */ 437 buffer_get_bignum(&decrypted, prv->rsa->d); 438 buffer_get_bignum(&decrypted, prv->rsa->iqmp); /* u */ 439 /* in SSL and SSH v1 p and q are exchanged */ 440 buffer_get_bignum(&decrypted, prv->rsa->q); /* p */ 441 buffer_get_bignum(&decrypted, prv->rsa->p); /* q */ 442 443 /* calculate p-1 and q-1 */ 444 rsa_generate_additional_parameters(prv->rsa); 445 446 buffer_free(&decrypted); 447 448 /* enable blinding */ 449 if (RSA_blinding_on(prv->rsa, NULL) != 1) { 450 error("key_load_private_rsa1: RSA_blinding_on failed"); 451 goto fail; 452 } 453 close(fd); 454 return prv; 455 456 fail: 457 if (commentp) 458 xfree(*commentp); 459 close(fd); 460 key_free(prv); 461 return NULL; 462 } 463 464 Key * 465 key_load_private_pem(int fd, int type, const char *passphrase, 466 char **commentp) 467 { 468 FILE *fp; 469 EVP_PKEY *pk = NULL; 470 Key *prv = NULL; 471 char *name = "<no key>"; 472 473 fp = fdopen(fd, "r"); 474 if (fp == NULL) { 475 error("fdopen failed: %s", strerror(errno)); 476 close(fd); 477 return NULL; 478 } 479 pk = PEM_read_PrivateKey(fp, NULL, NULL, (char *)passphrase); 480 if (pk == NULL) { 481 debug("PEM_read_PrivateKey failed"); 482 (void)ERR_get_error(); 483 } else if (pk->type == EVP_PKEY_RSA && 484 (type == KEY_UNSPEC||type==KEY_RSA)) { 485 prv = key_new(KEY_UNSPEC); 486 prv->rsa = EVP_PKEY_get1_RSA(pk); 487 prv->type = KEY_RSA; 488 name = "rsa w/o comment"; 489 #ifdef DEBUG_PK 490 RSA_print_fp(stderr, prv->rsa, 8); 491 #endif 492 if (RSA_blinding_on(prv->rsa, NULL) != 1) { 493 error("key_load_private_pem: RSA_blinding_on failed"); 494 key_free(prv); 495 prv = NULL; 496 } 497 } else if (pk->type == EVP_PKEY_DSA && 498 (type == KEY_UNSPEC||type==KEY_DSA)) { 499 prv = key_new(KEY_UNSPEC); 500 prv->dsa = EVP_PKEY_get1_DSA(pk); 501 prv->type = KEY_DSA; 502 name = "dsa w/o comment"; 503 #ifdef DEBUG_PK 504 DSA_print_fp(stderr, prv->dsa, 8); 505 #endif 506 } else { 507 error("PEM_read_PrivateKey: mismatch or " 508 "unknown EVP_PKEY save_type %d", pk->save_type); 509 } 510 fclose(fp); 511 if (pk != NULL) 512 EVP_PKEY_free(pk); 513 if (prv != NULL && commentp) 514 *commentp = xstrdup(name); 515 debug("read PEM private key done: type %s", 516 prv ? key_type(prv) : "<unknown>"); 517 return prv; 518 } 519 520 int 521 key_perm_ok(int fd, const char *filename) 522 { 523 struct stat st; 524 525 if (fstat(fd, &st) < 0) 526 return 0; 527 /* 528 * if a key owned by the user is accessed, then we check the 529 * permissions of the file. if the key owned by a different user, 530 * then we don't care. 531 */ 532 #ifdef HAVE_CYGWIN 533 if (check_ntsec(filename)) 534 #endif 535 if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0) { 536 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 537 error("@ WARNING: UNPROTECTED PRIVATE KEY FILE! @"); 538 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 539 error("Permissions 0%3.3o for '%s' are too open.", 540 (u_int)st.st_mode & 0777, filename); 541 error("It is recommended that your private key files are NOT accessible by others."); 542 error("This private key will be ignored."); 543 return 0; 544 } 545 return 1; 546 } 547 548 Key * 549 key_load_private_type(int type, const char *filename, const char *passphrase, 550 char **commentp, int *perm_ok) 551 { 552 int fd; 553 554 fd = open(filename, O_RDONLY); 555 if (fd < 0) 556 return NULL; 557 if (!key_perm_ok(fd, filename)) { 558 if (perm_ok != NULL) 559 *perm_ok = 0; 560 error("bad permissions: ignore key: %s", filename); 561 close(fd); 562 return NULL; 563 } 564 if (perm_ok != NULL) 565 *perm_ok = 1; 566 switch (type) { 567 case KEY_RSA1: 568 return key_load_private_rsa1(fd, filename, passphrase, 569 commentp); 570 /* closes fd */ 571 case KEY_DSA: 572 case KEY_RSA: 573 case KEY_UNSPEC: 574 return key_load_private_pem(fd, type, passphrase, commentp); 575 /* closes fd */ 576 default: 577 close(fd); 578 break; 579 } 580 return NULL; 581 } 582 583 Key * 584 key_load_private(const char *filename, const char *passphrase, 585 char **commentp) 586 { 587 Key *pub, *prv; 588 int fd; 589 590 fd = open(filename, O_RDONLY); 591 if (fd < 0) 592 return NULL; 593 if (!key_perm_ok(fd, filename)) { 594 error("bad permissions: ignore key: %s", filename); 595 close(fd); 596 return NULL; 597 } 598 pub = key_load_public_rsa1(fd, filename, commentp); 599 lseek(fd, (off_t) 0, SEEK_SET); /* rewind */ 600 if (pub == NULL) { 601 /* closes fd */ 602 prv = key_load_private_pem(fd, KEY_UNSPEC, passphrase, NULL); 603 /* use the filename as a comment for PEM */ 604 if (commentp && prv) 605 *commentp = xstrdup(filename); 606 } else { 607 /* it's a SSH v1 key if the public key part is readable */ 608 key_free(pub); 609 /* closes fd */ 610 prv = key_load_private_rsa1(fd, filename, passphrase, NULL); 611 } 612 return prv; 613 } 614 615 static int 616 key_try_load_public(Key *k, const char *filename, char **commentp) 617 { 618 FILE *f; 619 char line[SSH_MAX_PUBKEY_BYTES]; 620 char *cp; 621 u_long linenum = 0; 622 623 f = fopen(filename, "r"); 624 if (f != NULL) { 625 while (read_keyfile_line(f, filename, line, sizeof(line), 626 &linenum) != -1) { 627 cp = line; 628 switch (*cp) { 629 case '#': 630 case '\n': 631 case '\0': 632 continue; 633 } 634 /* Skip leading whitespace. */ 635 for (; *cp && (*cp == ' ' || *cp == '\t'); cp++) 636 ; 637 if (*cp) { 638 if (key_read(k, &cp) == 1) { 639 if (commentp) 640 *commentp=xstrdup(filename); 641 fclose(f); 642 return 1; 643 } 644 } 645 } 646 fclose(f); 647 } 648 return 0; 649 } 650 651 /* load public key from ssh v1 private or any pubkey file */ 652 Key * 653 key_load_public(const char *filename, char **commentp) 654 { 655 Key *pub; 656 char file[MAXPATHLEN]; 657 658 /* try rsa1 private key */ 659 pub = key_load_public_type(KEY_RSA1, filename, commentp); 660 if (pub != NULL) 661 return pub; 662 663 /* try rsa1 public key */ 664 pub = key_new(KEY_RSA1); 665 if (key_try_load_public(pub, filename, commentp) == 1) 666 return pub; 667 key_free(pub); 668 669 /* try ssh2 public key */ 670 pub = key_new(KEY_UNSPEC); 671 if (key_try_load_public(pub, filename, commentp) == 1) 672 return pub; 673 if ((strlcpy(file, filename, sizeof file) < sizeof(file)) && 674 (strlcat(file, ".pub", sizeof file) < sizeof(file)) && 675 (key_try_load_public(pub, file, commentp) == 1)) 676 return pub; 677 key_free(pub); 678 return NULL; 679 } 680