1 /* 2 * Author: Tatu Ylonen <ylo@cs.hut.fi> 3 * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland 4 * All rights reserved 5 * This file contains functions for reading and writing identity files, and 6 * for reading the passphrase from the user. 7 * 8 * As far as I am concerned, the code I have written for this software 9 * can be used freely for any purpose. Any derived versions of this 10 * software must be clearly marked as such, and if the derived work is 11 * incompatible with the protocol description in the RFC file, it must be 12 * called by a name other than "ssh" or "Secure Shell". 13 * 14 * 15 * Copyright (c) 2000 Markus Friedl. All rights reserved. 16 * 17 * Redistribution and use in source and binary forms, with or without 18 * modification, are permitted provided that the following conditions 19 * are met: 20 * 1. Redistributions of source code must retain the above copyright 21 * notice, this list of conditions and the following disclaimer. 22 * 2. Redistributions in binary form must reproduce the above copyright 23 * notice, this list of conditions and the following disclaimer in the 24 * documentation and/or other materials provided with the distribution. 25 * 26 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 27 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 28 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 29 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 30 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 31 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 32 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 33 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 34 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 35 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 36 */ 37 38 #include "includes.h" 39 RCSID("$OpenBSD: authfile.c,v 1.57 2004/06/21 17:36:31 avsm Exp $"); 40 41 #include <openssl/err.h> 42 #include <openssl/evp.h> 43 #include <openssl/pem.h> 44 45 #include "cipher.h" 46 #include "xmalloc.h" 47 #include "buffer.h" 48 #include "bufaux.h" 49 #include "key.h" 50 #include "ssh.h" 51 #include "log.h" 52 #include "authfile.h" 53 #include "rsa.h" 54 55 /* Version identification string for SSH v1 identity files. */ 56 static const char authfile_id_string[] = 57 "SSH PRIVATE KEY FILE FORMAT 1.1\n"; 58 59 /* 60 * Saves the authentication (private) key in a file, encrypting it with 61 * passphrase. The identification of the file (lowest 64 bits of n) will 62 * precede the key to provide identification of the key without needing a 63 * passphrase. 64 */ 65 66 static int 67 key_save_private_rsa1(Key *key, const char *filename, const char *passphrase, 68 const char *comment) 69 { 70 Buffer buffer, encrypted; 71 u_char buf[100], *cp; 72 int fd, i, cipher_num; 73 CipherContext ciphercontext; 74 Cipher *cipher; 75 u_int32_t rnd; 76 77 /* 78 * If the passphrase is empty, use SSH_CIPHER_NONE to ease converting 79 * to another cipher; otherwise use SSH_AUTHFILE_CIPHER. 80 */ 81 cipher_num = (strcmp(passphrase, "") == 0) ? 82 SSH_CIPHER_NONE : SSH_AUTHFILE_CIPHER; 83 if ((cipher = cipher_by_number(cipher_num)) == NULL) 84 fatal("save_private_key_rsa: bad cipher"); 85 86 /* This buffer is used to built the secret part of the private key. */ 87 buffer_init(&buffer); 88 89 /* Put checkbytes for checking passphrase validity. */ 90 rnd = arc4random(); 91 buf[0] = rnd & 0xff; 92 buf[1] = (rnd >> 8) & 0xff; 93 buf[2] = buf[0]; 94 buf[3] = buf[1]; 95 buffer_append(&buffer, buf, 4); 96 97 /* 98 * Store the private key (n and e will not be stored because they 99 * will be stored in plain text, and storing them also in encrypted 100 * format would just give known plaintext). 101 */ 102 buffer_put_bignum(&buffer, key->rsa->d); 103 buffer_put_bignum(&buffer, key->rsa->iqmp); 104 buffer_put_bignum(&buffer, key->rsa->q); /* reverse from SSL p */ 105 buffer_put_bignum(&buffer, key->rsa->p); /* reverse from SSL q */ 106 107 /* Pad the part to be encrypted until its size is a multiple of 8. */ 108 while (buffer_len(&buffer) % 8 != 0) 109 buffer_put_char(&buffer, 0); 110 111 /* This buffer will be used to contain the data in the file. */ 112 buffer_init(&encrypted); 113 114 /* First store keyfile id string. */ 115 for (i = 0; authfile_id_string[i]; i++) 116 buffer_put_char(&encrypted, authfile_id_string[i]); 117 buffer_put_char(&encrypted, 0); 118 119 /* Store cipher type. */ 120 buffer_put_char(&encrypted, cipher_num); 121 buffer_put_int(&encrypted, 0); /* For future extension */ 122 123 /* Store public key. This will be in plain text. */ 124 buffer_put_int(&encrypted, BN_num_bits(key->rsa->n)); 125 buffer_put_bignum(&encrypted, key->rsa->n); 126 buffer_put_bignum(&encrypted, key->rsa->e); 127 buffer_put_cstring(&encrypted, comment); 128 129 /* Allocate space for the private part of the key in the buffer. */ 130 cp = buffer_append_space(&encrypted, buffer_len(&buffer)); 131 132 cipher_set_key_string(&ciphercontext, cipher, passphrase, 133 CIPHER_ENCRYPT); 134 cipher_crypt(&ciphercontext, cp, 135 buffer_ptr(&buffer), buffer_len(&buffer)); 136 cipher_cleanup(&ciphercontext); 137 memset(&ciphercontext, 0, sizeof(ciphercontext)); 138 139 /* Destroy temporary data. */ 140 memset(buf, 0, sizeof(buf)); 141 buffer_free(&buffer); 142 143 fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600); 144 if (fd < 0) { 145 error("open %s failed: %s.", filename, strerror(errno)); 146 buffer_free(&encrypted); 147 return 0; 148 } 149 if (write(fd, buffer_ptr(&encrypted), buffer_len(&encrypted)) != 150 buffer_len(&encrypted)) { 151 error("write to key file %s failed: %s", filename, 152 strerror(errno)); 153 buffer_free(&encrypted); 154 close(fd); 155 unlink(filename); 156 return 0; 157 } 158 close(fd); 159 buffer_free(&encrypted); 160 return 1; 161 } 162 163 /* save SSH v2 key in OpenSSL PEM format */ 164 static int 165 key_save_private_pem(Key *key, const char *filename, const char *_passphrase, 166 const char *comment) 167 { 168 FILE *fp; 169 int fd; 170 int success = 0; 171 int len = strlen(_passphrase); 172 u_char *passphrase = (len > 0) ? (u_char *)_passphrase : NULL; 173 const EVP_CIPHER *cipher = (len > 0) ? EVP_des_ede3_cbc() : NULL; 174 175 if (len > 0 && len <= 4) { 176 error("passphrase too short: have %d bytes, need > 4", len); 177 return 0; 178 } 179 fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600); 180 if (fd < 0) { 181 error("open %s failed: %s.", filename, strerror(errno)); 182 return 0; 183 } 184 fp = fdopen(fd, "w"); 185 if (fp == NULL ) { 186 error("fdopen %s failed: %s.", filename, strerror(errno)); 187 close(fd); 188 return 0; 189 } 190 switch (key->type) { 191 case KEY_DSA: 192 success = PEM_write_DSAPrivateKey(fp, key->dsa, 193 cipher, passphrase, len, NULL, NULL); 194 break; 195 case KEY_RSA: 196 success = PEM_write_RSAPrivateKey(fp, key->rsa, 197 cipher, passphrase, len, NULL, NULL); 198 break; 199 } 200 fclose(fp); 201 return success; 202 } 203 204 int 205 key_save_private(Key *key, const char *filename, const char *passphrase, 206 const char *comment) 207 { 208 switch (key->type) { 209 case KEY_RSA1: 210 return key_save_private_rsa1(key, filename, passphrase, 211 comment); 212 break; 213 case KEY_DSA: 214 case KEY_RSA: 215 return key_save_private_pem(key, filename, passphrase, 216 comment); 217 break; 218 default: 219 break; 220 } 221 error("key_save_private: cannot save key type %d", key->type); 222 return 0; 223 } 224 225 /* 226 * Loads the public part of the ssh v1 key file. Returns NULL if an error was 227 * encountered (the file does not exist or is not readable), and the key 228 * otherwise. 229 */ 230 231 static Key * 232 key_load_public_rsa1(int fd, const char *filename, char **commentp) 233 { 234 Buffer buffer; 235 Key *pub; 236 struct stat st; 237 char *cp; 238 int i; 239 size_t len; 240 241 if (fstat(fd, &st) < 0) { 242 error("fstat for key file %.200s failed: %.100s", 243 filename, strerror(errno)); 244 return NULL; 245 } 246 if (st.st_size > 1*1024*1024) 247 close(fd); 248 len = (size_t)st.st_size; /* truncated */ 249 250 buffer_init(&buffer); 251 cp = buffer_append_space(&buffer, len); 252 253 if (read(fd, cp, (size_t) len) != (size_t) len) { 254 debug("Read from key file %.200s failed: %.100s", filename, 255 strerror(errno)); 256 buffer_free(&buffer); 257 return NULL; 258 } 259 260 /* Check that it is at least big enough to contain the ID string. */ 261 if (len < sizeof(authfile_id_string)) { 262 debug3("Not a RSA1 key file %.200s.", filename); 263 buffer_free(&buffer); 264 return NULL; 265 } 266 /* 267 * Make sure it begins with the id string. Consume the id string 268 * from the buffer. 269 */ 270 for (i = 0; i < sizeof(authfile_id_string); i++) 271 if (buffer_get_char(&buffer) != authfile_id_string[i]) { 272 debug3("Not a RSA1 key file %.200s.", filename); 273 buffer_free(&buffer); 274 return NULL; 275 } 276 /* Skip cipher type and reserved data. */ 277 (void) buffer_get_char(&buffer); /* cipher type */ 278 (void) buffer_get_int(&buffer); /* reserved */ 279 280 /* Read the public key from the buffer. */ 281 (void) buffer_get_int(&buffer); 282 pub = key_new(KEY_RSA1); 283 buffer_get_bignum(&buffer, pub->rsa->n); 284 buffer_get_bignum(&buffer, pub->rsa->e); 285 if (commentp) 286 *commentp = buffer_get_string(&buffer, NULL); 287 /* The encrypted private part is not parsed by this function. */ 288 289 buffer_free(&buffer); 290 return pub; 291 } 292 293 /* load public key from private-key file, works only for SSH v1 */ 294 Key * 295 key_load_public_type(int type, const char *filename, char **commentp) 296 { 297 Key *pub; 298 int fd; 299 300 if (type == KEY_RSA1) { 301 fd = open(filename, O_RDONLY); 302 if (fd < 0) 303 return NULL; 304 pub = key_load_public_rsa1(fd, filename, commentp); 305 close(fd); 306 return pub; 307 } 308 return NULL; 309 } 310 311 /* 312 * Loads the private key from the file. Returns 0 if an error is encountered 313 * (file does not exist or is not readable, or passphrase is bad). This 314 * initializes the private key. 315 * Assumes we are called under uid of the owner of the file. 316 */ 317 318 static Key * 319 key_load_private_rsa1(int fd, const char *filename, const char *passphrase, 320 char **commentp) 321 { 322 int i, check1, check2, cipher_type; 323 size_t len; 324 Buffer buffer, decrypted; 325 u_char *cp; 326 CipherContext ciphercontext; 327 Cipher *cipher; 328 Key *prv = NULL; 329 struct stat st; 330 331 if (fstat(fd, &st) < 0) { 332 error("fstat for key file %.200s failed: %.100s", 333 filename, strerror(errno)); 334 close(fd); 335 return NULL; 336 } 337 if (st.st_size > 1*1024*1024) { 338 close(fd); 339 return (NULL); 340 } 341 len = (size_t)st.st_size; /* truncated */ 342 343 buffer_init(&buffer); 344 cp = buffer_append_space(&buffer, len); 345 346 if (read(fd, cp, (size_t) len) != (size_t) len) { 347 debug("Read from key file %.200s failed: %.100s", filename, 348 strerror(errno)); 349 buffer_free(&buffer); 350 close(fd); 351 return NULL; 352 } 353 354 /* Check that it is at least big enough to contain the ID string. */ 355 if (len < sizeof(authfile_id_string)) { 356 debug3("Not a RSA1 key file %.200s.", filename); 357 buffer_free(&buffer); 358 close(fd); 359 return NULL; 360 } 361 /* 362 * Make sure it begins with the id string. Consume the id string 363 * from the buffer. 364 */ 365 for (i = 0; i < sizeof(authfile_id_string); i++) 366 if (buffer_get_char(&buffer) != authfile_id_string[i]) { 367 debug3("Not a RSA1 key file %.200s.", filename); 368 buffer_free(&buffer); 369 close(fd); 370 return NULL; 371 } 372 373 /* Read cipher type. */ 374 cipher_type = buffer_get_char(&buffer); 375 (void) buffer_get_int(&buffer); /* Reserved data. */ 376 377 /* Read the public key from the buffer. */ 378 (void) buffer_get_int(&buffer); 379 prv = key_new_private(KEY_RSA1); 380 381 buffer_get_bignum(&buffer, prv->rsa->n); 382 buffer_get_bignum(&buffer, prv->rsa->e); 383 if (commentp) 384 *commentp = buffer_get_string(&buffer, NULL); 385 else 386 xfree(buffer_get_string(&buffer, NULL)); 387 388 /* Check that it is a supported cipher. */ 389 cipher = cipher_by_number(cipher_type); 390 if (cipher == NULL) { 391 debug("Unsupported cipher %d used in key file %.200s.", 392 cipher_type, filename); 393 buffer_free(&buffer); 394 goto fail; 395 } 396 /* Initialize space for decrypted data. */ 397 buffer_init(&decrypted); 398 cp = buffer_append_space(&decrypted, buffer_len(&buffer)); 399 400 /* Rest of the buffer is encrypted. Decrypt it using the passphrase. */ 401 cipher_set_key_string(&ciphercontext, cipher, passphrase, 402 CIPHER_DECRYPT); 403 cipher_crypt(&ciphercontext, cp, 404 buffer_ptr(&buffer), buffer_len(&buffer)); 405 cipher_cleanup(&ciphercontext); 406 memset(&ciphercontext, 0, sizeof(ciphercontext)); 407 buffer_free(&buffer); 408 409 check1 = buffer_get_char(&decrypted); 410 check2 = buffer_get_char(&decrypted); 411 if (check1 != buffer_get_char(&decrypted) || 412 check2 != buffer_get_char(&decrypted)) { 413 if (strcmp(passphrase, "") != 0) 414 debug("Bad passphrase supplied for key file %.200s.", 415 filename); 416 /* Bad passphrase. */ 417 buffer_free(&decrypted); 418 goto fail; 419 } 420 /* Read the rest of the private key. */ 421 buffer_get_bignum(&decrypted, prv->rsa->d); 422 buffer_get_bignum(&decrypted, prv->rsa->iqmp); /* u */ 423 /* in SSL and SSH v1 p and q are exchanged */ 424 buffer_get_bignum(&decrypted, prv->rsa->q); /* p */ 425 buffer_get_bignum(&decrypted, prv->rsa->p); /* q */ 426 427 /* calculate p-1 and q-1 */ 428 rsa_generate_additional_parameters(prv->rsa); 429 430 buffer_free(&decrypted); 431 432 /* enable blinding */ 433 if (RSA_blinding_on(prv->rsa, NULL) != 1) { 434 error("key_load_private_rsa1: RSA_blinding_on failed"); 435 goto fail; 436 } 437 close(fd); 438 return prv; 439 440 fail: 441 if (commentp) 442 xfree(*commentp); 443 close(fd); 444 key_free(prv); 445 return NULL; 446 } 447 448 Key * 449 key_load_private_pem(int fd, int type, const char *passphrase, 450 char **commentp) 451 { 452 FILE *fp; 453 EVP_PKEY *pk = NULL; 454 Key *prv = NULL; 455 char *name = "<no key>"; 456 457 fp = fdopen(fd, "r"); 458 if (fp == NULL) { 459 error("fdopen failed: %s", strerror(errno)); 460 close(fd); 461 return NULL; 462 } 463 pk = PEM_read_PrivateKey(fp, NULL, NULL, (char *)passphrase); 464 if (pk == NULL) { 465 debug("PEM_read_PrivateKey failed"); 466 (void)ERR_get_error(); 467 } else if (pk->type == EVP_PKEY_RSA && 468 (type == KEY_UNSPEC||type==KEY_RSA)) { 469 prv = key_new(KEY_UNSPEC); 470 prv->rsa = EVP_PKEY_get1_RSA(pk); 471 prv->type = KEY_RSA; 472 name = "rsa w/o comment"; 473 #ifdef DEBUG_PK 474 RSA_print_fp(stderr, prv->rsa, 8); 475 #endif 476 if (RSA_blinding_on(prv->rsa, NULL) != 1) { 477 error("key_load_private_pem: RSA_blinding_on failed"); 478 key_free(prv); 479 prv = NULL; 480 } 481 } else if (pk->type == EVP_PKEY_DSA && 482 (type == KEY_UNSPEC||type==KEY_DSA)) { 483 prv = key_new(KEY_UNSPEC); 484 prv->dsa = EVP_PKEY_get1_DSA(pk); 485 prv->type = KEY_DSA; 486 name = "dsa w/o comment"; 487 #ifdef DEBUG_PK 488 DSA_print_fp(stderr, prv->dsa, 8); 489 #endif 490 } else { 491 error("PEM_read_PrivateKey: mismatch or " 492 "unknown EVP_PKEY save_type %d", pk->save_type); 493 } 494 fclose(fp); 495 if (pk != NULL) 496 EVP_PKEY_free(pk); 497 if (prv != NULL && commentp) 498 *commentp = xstrdup(name); 499 debug("read PEM private key done: type %s", 500 prv ? key_type(prv) : "<unknown>"); 501 return prv; 502 } 503 504 static int 505 key_perm_ok(int fd, const char *filename) 506 { 507 struct stat st; 508 509 if (fstat(fd, &st) < 0) 510 return 0; 511 /* 512 * if a key owned by the user is accessed, then we check the 513 * permissions of the file. if the key owned by a different user, 514 * then we don't care. 515 */ 516 #ifdef HAVE_CYGWIN 517 if (check_ntsec(filename)) 518 #endif 519 if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0) { 520 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 521 error("@ WARNING: UNPROTECTED PRIVATE KEY FILE! @"); 522 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 523 error("Permissions 0%3.3o for '%s' are too open.", 524 (u_int)st.st_mode & 0777, filename); 525 error("It is recommended that your private key files are NOT accessible by others."); 526 error("This private key will be ignored."); 527 return 0; 528 } 529 return 1; 530 } 531 532 Key * 533 key_load_private_type(int type, const char *filename, const char *passphrase, 534 char **commentp) 535 { 536 int fd; 537 538 fd = open(filename, O_RDONLY); 539 if (fd < 0) 540 return NULL; 541 if (!key_perm_ok(fd, filename)) { 542 error("bad permissions: ignore key: %s", filename); 543 close(fd); 544 return NULL; 545 } 546 switch (type) { 547 case KEY_RSA1: 548 return key_load_private_rsa1(fd, filename, passphrase, 549 commentp); 550 /* closes fd */ 551 break; 552 case KEY_DSA: 553 case KEY_RSA: 554 case KEY_UNSPEC: 555 return key_load_private_pem(fd, type, passphrase, commentp); 556 /* closes fd */ 557 break; 558 default: 559 close(fd); 560 break; 561 } 562 return NULL; 563 } 564 565 Key * 566 key_load_private(const char *filename, const char *passphrase, 567 char **commentp) 568 { 569 Key *pub, *prv; 570 int fd; 571 572 fd = open(filename, O_RDONLY); 573 if (fd < 0) 574 return NULL; 575 if (!key_perm_ok(fd, filename)) { 576 error("bad permissions: ignore key: %s", filename); 577 close(fd); 578 return NULL; 579 } 580 pub = key_load_public_rsa1(fd, filename, commentp); 581 lseek(fd, (off_t) 0, SEEK_SET); /* rewind */ 582 if (pub == NULL) { 583 /* closes fd */ 584 prv = key_load_private_pem(fd, KEY_UNSPEC, passphrase, NULL); 585 /* use the filename as a comment for PEM */ 586 if (commentp && prv) 587 *commentp = xstrdup(filename); 588 } else { 589 /* it's a SSH v1 key if the public key part is readable */ 590 key_free(pub); 591 /* closes fd */ 592 prv = key_load_private_rsa1(fd, filename, passphrase, NULL); 593 } 594 return prv; 595 } 596 597 static int 598 key_try_load_public(Key *k, const char *filename, char **commentp) 599 { 600 FILE *f; 601 char line[4096]; 602 char *cp; 603 604 f = fopen(filename, "r"); 605 if (f != NULL) { 606 while (fgets(line, sizeof(line), f)) { 607 line[sizeof(line)-1] = '\0'; 608 cp = line; 609 switch (*cp) { 610 case '#': 611 case '\n': 612 case '\0': 613 continue; 614 } 615 /* Skip leading whitespace. */ 616 for (; *cp && (*cp == ' ' || *cp == '\t'); cp++) 617 ; 618 if (*cp) { 619 if (key_read(k, &cp) == 1) { 620 if (commentp) 621 *commentp=xstrdup(filename); 622 fclose(f); 623 return 1; 624 } 625 } 626 } 627 fclose(f); 628 } 629 return 0; 630 } 631 632 /* load public key from ssh v1 private or any pubkey file */ 633 Key * 634 key_load_public(const char *filename, char **commentp) 635 { 636 Key *pub; 637 char file[MAXPATHLEN]; 638 639 /* try rsa1 private key */ 640 pub = key_load_public_type(KEY_RSA1, filename, commentp); 641 if (pub != NULL) 642 return pub; 643 644 /* try rsa1 public key */ 645 pub = key_new(KEY_RSA1); 646 if (key_try_load_public(pub, filename, commentp) == 1) 647 return pub; 648 key_free(pub); 649 650 /* try ssh2 public key */ 651 pub = key_new(KEY_UNSPEC); 652 if (key_try_load_public(pub, filename, commentp) == 1) 653 return pub; 654 if ((strlcpy(file, filename, sizeof file) < sizeof(file)) && 655 (strlcat(file, ".pub", sizeof file) < sizeof(file)) && 656 (key_try_load_public(pub, file, commentp) == 1)) 657 return pub; 658 key_free(pub); 659 return NULL; 660 } 661