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 1.55 2003/09/18 07:56:05 markus 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 rand; 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 rand = arc4random(); 91 buf[0] = rand & 0xff; 92 buf[1] = (rand >> 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 off_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 len = st.st_size; 247 248 buffer_init(&buffer); 249 cp = buffer_append_space(&buffer, len); 250 251 if (read(fd, cp, (size_t) len) != (size_t) len) { 252 debug("Read from key file %.200s failed: %.100s", filename, 253 strerror(errno)); 254 buffer_free(&buffer); 255 return NULL; 256 } 257 258 /* Check that it is at least big enough to contain the ID string. */ 259 if (len < sizeof(authfile_id_string)) { 260 debug3("Not a RSA1 key file %.200s.", filename); 261 buffer_free(&buffer); 262 return NULL; 263 } 264 /* 265 * Make sure it begins with the id string. Consume the id string 266 * from the buffer. 267 */ 268 for (i = 0; i < sizeof(authfile_id_string); i++) 269 if (buffer_get_char(&buffer) != authfile_id_string[i]) { 270 debug3("Not a RSA1 key file %.200s.", filename); 271 buffer_free(&buffer); 272 return NULL; 273 } 274 /* Skip cipher type and reserved data. */ 275 (void) buffer_get_char(&buffer); /* cipher type */ 276 (void) buffer_get_int(&buffer); /* reserved */ 277 278 /* Read the public key from the buffer. */ 279 (void) buffer_get_int(&buffer); 280 pub = key_new(KEY_RSA1); 281 buffer_get_bignum(&buffer, pub->rsa->n); 282 buffer_get_bignum(&buffer, pub->rsa->e); 283 if (commentp) 284 *commentp = buffer_get_string(&buffer, NULL); 285 /* The encrypted private part is not parsed by this function. */ 286 287 buffer_free(&buffer); 288 return pub; 289 } 290 291 /* load public key from private-key file, works only for SSH v1 */ 292 Key * 293 key_load_public_type(int type, const char *filename, char **commentp) 294 { 295 Key *pub; 296 int fd; 297 298 if (type == KEY_RSA1) { 299 fd = open(filename, O_RDONLY); 300 if (fd < 0) 301 return NULL; 302 pub = key_load_public_rsa1(fd, filename, commentp); 303 close(fd); 304 return pub; 305 } 306 return NULL; 307 } 308 309 /* 310 * Loads the private key from the file. Returns 0 if an error is encountered 311 * (file does not exist or is not readable, or passphrase is bad). This 312 * initializes the private key. 313 * Assumes we are called under uid of the owner of the file. 314 */ 315 316 static Key * 317 key_load_private_rsa1(int fd, const char *filename, const char *passphrase, 318 char **commentp) 319 { 320 int i, check1, check2, cipher_type; 321 off_t len; 322 Buffer buffer, decrypted; 323 u_char *cp; 324 CipherContext ciphercontext; 325 Cipher *cipher; 326 Key *prv = NULL; 327 struct stat st; 328 329 if (fstat(fd, &st) < 0) { 330 error("fstat for key file %.200s failed: %.100s", 331 filename, strerror(errno)); 332 close(fd); 333 return NULL; 334 } 335 len = st.st_size; 336 337 buffer_init(&buffer); 338 cp = buffer_append_space(&buffer, len); 339 340 if (read(fd, cp, (size_t) len) != (size_t) len) { 341 debug("Read from key file %.200s failed: %.100s", filename, 342 strerror(errno)); 343 buffer_free(&buffer); 344 close(fd); 345 return NULL; 346 } 347 348 /* Check that it is at least big enough to contain the ID string. */ 349 if (len < sizeof(authfile_id_string)) { 350 debug3("Not a RSA1 key file %.200s.", filename); 351 buffer_free(&buffer); 352 close(fd); 353 return NULL; 354 } 355 /* 356 * Make sure it begins with the id string. Consume the id string 357 * from the buffer. 358 */ 359 for (i = 0; i < sizeof(authfile_id_string); i++) 360 if (buffer_get_char(&buffer) != authfile_id_string[i]) { 361 debug3("Not a RSA1 key file %.200s.", filename); 362 buffer_free(&buffer); 363 close(fd); 364 return NULL; 365 } 366 367 /* Read cipher type. */ 368 cipher_type = buffer_get_char(&buffer); 369 (void) buffer_get_int(&buffer); /* Reserved data. */ 370 371 /* Read the public key from the buffer. */ 372 (void) buffer_get_int(&buffer); 373 prv = key_new_private(KEY_RSA1); 374 375 buffer_get_bignum(&buffer, prv->rsa->n); 376 buffer_get_bignum(&buffer, prv->rsa->e); 377 if (commentp) 378 *commentp = buffer_get_string(&buffer, NULL); 379 else 380 xfree(buffer_get_string(&buffer, NULL)); 381 382 /* Check that it is a supported cipher. */ 383 cipher = cipher_by_number(cipher_type); 384 if (cipher == NULL) { 385 debug("Unsupported cipher %d used in key file %.200s.", 386 cipher_type, filename); 387 buffer_free(&buffer); 388 goto fail; 389 } 390 /* Initialize space for decrypted data. */ 391 buffer_init(&decrypted); 392 cp = buffer_append_space(&decrypted, buffer_len(&buffer)); 393 394 /* Rest of the buffer is encrypted. Decrypt it using the passphrase. */ 395 cipher_set_key_string(&ciphercontext, cipher, passphrase, 396 CIPHER_DECRYPT); 397 cipher_crypt(&ciphercontext, cp, 398 buffer_ptr(&buffer), buffer_len(&buffer)); 399 cipher_cleanup(&ciphercontext); 400 memset(&ciphercontext, 0, sizeof(ciphercontext)); 401 buffer_free(&buffer); 402 403 check1 = buffer_get_char(&decrypted); 404 check2 = buffer_get_char(&decrypted); 405 if (check1 != buffer_get_char(&decrypted) || 406 check2 != buffer_get_char(&decrypted)) { 407 if (strcmp(passphrase, "") != 0) 408 debug("Bad passphrase supplied for key file %.200s.", 409 filename); 410 /* Bad passphrase. */ 411 buffer_free(&decrypted); 412 goto fail; 413 } 414 /* Read the rest of the private key. */ 415 buffer_get_bignum(&decrypted, prv->rsa->d); 416 buffer_get_bignum(&decrypted, prv->rsa->iqmp); /* u */ 417 /* in SSL and SSH v1 p and q are exchanged */ 418 buffer_get_bignum(&decrypted, prv->rsa->q); /* p */ 419 buffer_get_bignum(&decrypted, prv->rsa->p); /* q */ 420 421 /* calculate p-1 and q-1 */ 422 rsa_generate_additional_parameters(prv->rsa); 423 424 buffer_free(&decrypted); 425 426 /* enable blinding */ 427 if (RSA_blinding_on(prv->rsa, NULL) != 1) { 428 error("key_load_private_rsa1: RSA_blinding_on failed"); 429 goto fail; 430 } 431 close(fd); 432 return prv; 433 434 fail: 435 if (commentp) 436 xfree(*commentp); 437 close(fd); 438 key_free(prv); 439 return NULL; 440 } 441 442 Key * 443 key_load_private_pem(int fd, int type, const char *passphrase, 444 char **commentp) 445 { 446 FILE *fp; 447 EVP_PKEY *pk = NULL; 448 Key *prv = NULL; 449 char *name = "<no key>"; 450 451 fp = fdopen(fd, "r"); 452 if (fp == NULL) { 453 error("fdopen failed: %s", strerror(errno)); 454 close(fd); 455 return NULL; 456 } 457 pk = PEM_read_PrivateKey(fp, NULL, NULL, (char *)passphrase); 458 if (pk == NULL) { 459 debug("PEM_read_PrivateKey failed"); 460 (void)ERR_get_error(); 461 } else if (pk->type == EVP_PKEY_RSA && 462 (type == KEY_UNSPEC||type==KEY_RSA)) { 463 prv = key_new(KEY_UNSPEC); 464 prv->rsa = EVP_PKEY_get1_RSA(pk); 465 prv->type = KEY_RSA; 466 name = "rsa w/o comment"; 467 #ifdef DEBUG_PK 468 RSA_print_fp(stderr, prv->rsa, 8); 469 #endif 470 if (RSA_blinding_on(prv->rsa, NULL) != 1) { 471 error("key_load_private_pem: RSA_blinding_on failed"); 472 key_free(prv); 473 prv = NULL; 474 } 475 } else if (pk->type == EVP_PKEY_DSA && 476 (type == KEY_UNSPEC||type==KEY_DSA)) { 477 prv = key_new(KEY_UNSPEC); 478 prv->dsa = EVP_PKEY_get1_DSA(pk); 479 prv->type = KEY_DSA; 480 name = "dsa w/o comment"; 481 #ifdef DEBUG_PK 482 DSA_print_fp(stderr, prv->dsa, 8); 483 #endif 484 } else { 485 error("PEM_read_PrivateKey: mismatch or " 486 "unknown EVP_PKEY save_type %d", pk->save_type); 487 } 488 fclose(fp); 489 if (pk != NULL) 490 EVP_PKEY_free(pk); 491 if (prv != NULL && commentp) 492 *commentp = xstrdup(name); 493 debug("read PEM private key done: type %s", 494 prv ? key_type(prv) : "<unknown>"); 495 return prv; 496 } 497 498 static int 499 key_perm_ok(int fd, const char *filename) 500 { 501 struct stat st; 502 503 if (fstat(fd, &st) < 0) 504 return 0; 505 /* 506 * if a key owned by the user is accessed, then we check the 507 * permissions of the file. if the key owned by a different user, 508 * then we don't care. 509 */ 510 #ifdef HAVE_CYGWIN 511 if (check_ntsec(filename)) 512 #endif 513 if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0) { 514 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 515 error("@ WARNING: UNPROTECTED PRIVATE KEY FILE! @"); 516 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 517 error("Permissions 0%3.3o for '%s' are too open.", 518 (u_int)st.st_mode & 0777, filename); 519 error("It is recommended that your private key files are NOT accessible by others."); 520 error("This private key will be ignored."); 521 return 0; 522 } 523 return 1; 524 } 525 526 Key * 527 key_load_private_type(int type, const char *filename, const char *passphrase, 528 char **commentp) 529 { 530 int fd; 531 532 fd = open(filename, O_RDONLY); 533 if (fd < 0) 534 return NULL; 535 if (!key_perm_ok(fd, filename)) { 536 error("bad permissions: ignore key: %s", filename); 537 close(fd); 538 return NULL; 539 } 540 switch (type) { 541 case KEY_RSA1: 542 return key_load_private_rsa1(fd, filename, passphrase, 543 commentp); 544 /* closes fd */ 545 break; 546 case KEY_DSA: 547 case KEY_RSA: 548 case KEY_UNSPEC: 549 return key_load_private_pem(fd, type, passphrase, commentp); 550 /* closes fd */ 551 break; 552 default: 553 close(fd); 554 break; 555 } 556 return NULL; 557 } 558 559 Key * 560 key_load_private(const char *filename, const char *passphrase, 561 char **commentp) 562 { 563 Key *pub, *prv; 564 int fd; 565 566 fd = open(filename, O_RDONLY); 567 if (fd < 0) 568 return NULL; 569 if (!key_perm_ok(fd, filename)) { 570 error("bad permissions: ignore key: %s", filename); 571 close(fd); 572 return NULL; 573 } 574 pub = key_load_public_rsa1(fd, filename, commentp); 575 lseek(fd, (off_t) 0, SEEK_SET); /* rewind */ 576 if (pub == NULL) { 577 /* closes fd */ 578 prv = key_load_private_pem(fd, KEY_UNSPEC, passphrase, NULL); 579 /* use the filename as a comment for PEM */ 580 if (commentp && prv) 581 *commentp = xstrdup(filename); 582 } else { 583 /* it's a SSH v1 key if the public key part is readable */ 584 key_free(pub); 585 /* closes fd */ 586 prv = key_load_private_rsa1(fd, filename, passphrase, NULL); 587 } 588 return prv; 589 } 590 591 static int 592 key_try_load_public(Key *k, const char *filename, char **commentp) 593 { 594 FILE *f; 595 char line[4096]; 596 char *cp; 597 598 f = fopen(filename, "r"); 599 if (f != NULL) { 600 while (fgets(line, sizeof(line), f)) { 601 line[sizeof(line)-1] = '\0'; 602 cp = line; 603 switch (*cp) { 604 case '#': 605 case '\n': 606 case '\0': 607 continue; 608 } 609 /* Skip leading whitespace. */ 610 for (; *cp && (*cp == ' ' || *cp == '\t'); cp++) 611 ; 612 if (*cp) { 613 if (key_read(k, &cp) == 1) { 614 if (commentp) 615 *commentp=xstrdup(filename); 616 fclose(f); 617 return 1; 618 } 619 } 620 } 621 fclose(f); 622 } 623 return 0; 624 } 625 626 /* load public key from ssh v1 private or any pubkey file */ 627 Key * 628 key_load_public(const char *filename, char **commentp) 629 { 630 Key *pub; 631 char file[MAXPATHLEN]; 632 633 /* try rsa1 private key */ 634 pub = key_load_public_type(KEY_RSA1, filename, commentp); 635 if (pub != NULL) 636 return pub; 637 638 /* try rsa1 public key */ 639 pub = key_new(KEY_RSA1); 640 if (key_try_load_public(pub, filename, commentp) == 1) 641 return pub; 642 key_free(pub); 643 644 /* try ssh2 public key */ 645 pub = key_new(KEY_UNSPEC); 646 if (key_try_load_public(pub, filename, commentp) == 1) 647 return pub; 648 if ((strlcpy(file, filename, sizeof file) < sizeof(file)) && 649 (strlcat(file, ".pub", sizeof file) < sizeof(file)) && 650 (key_try_load_public(pub, file, commentp) == 1)) 651 return pub; 652 key_free(pub); 653 return NULL; 654 } 655