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 1.54 2003/05/24 09:30:39 djm 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 return 0; 147 } 148 if (write(fd, buffer_ptr(&encrypted), buffer_len(&encrypted)) != 149 buffer_len(&encrypted)) { 150 error("write to key file %s failed: %s", filename, 151 strerror(errno)); 152 buffer_free(&encrypted); 153 close(fd); 154 unlink(filename); 155 return 0; 156 } 157 close(fd); 158 buffer_free(&encrypted); 159 return 1; 160 } 161 162 /* save SSH v2 key in OpenSSL PEM format */ 163 static int 164 key_save_private_pem(Key *key, const char *filename, const char *_passphrase, 165 const char *comment) 166 { 167 FILE *fp; 168 int fd; 169 int success = 0; 170 int len = strlen(_passphrase); 171 u_char *passphrase = (len > 0) ? (u_char *)_passphrase : NULL; 172 const EVP_CIPHER *cipher = (len > 0) ? EVP_des_ede3_cbc() : NULL; 173 174 if (len > 0 && len <= 4) { 175 error("passphrase too short: have %d bytes, need > 4", len); 176 return 0; 177 } 178 fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600); 179 if (fd < 0) { 180 error("open %s failed: %s.", filename, strerror(errno)); 181 return 0; 182 } 183 fp = fdopen(fd, "w"); 184 if (fp == NULL ) { 185 error("fdopen %s failed: %s.", filename, strerror(errno)); 186 close(fd); 187 return 0; 188 } 189 switch (key->type) { 190 case KEY_DSA: 191 success = PEM_write_DSAPrivateKey(fp, key->dsa, 192 cipher, passphrase, len, NULL, NULL); 193 break; 194 case KEY_RSA: 195 success = PEM_write_RSAPrivateKey(fp, key->rsa, 196 cipher, passphrase, len, NULL, NULL); 197 break; 198 } 199 fclose(fp); 200 return success; 201 } 202 203 int 204 key_save_private(Key *key, const char *filename, const char *passphrase, 205 const char *comment) 206 { 207 switch (key->type) { 208 case KEY_RSA1: 209 return key_save_private_rsa1(key, filename, passphrase, 210 comment); 211 break; 212 case KEY_DSA: 213 case KEY_RSA: 214 return key_save_private_pem(key, filename, passphrase, 215 comment); 216 break; 217 default: 218 break; 219 } 220 error("key_save_private: cannot save key type %d", key->type); 221 return 0; 222 } 223 224 /* 225 * Loads the public part of the ssh v1 key file. Returns NULL if an error was 226 * encountered (the file does not exist or is not readable), and the key 227 * otherwise. 228 */ 229 230 static Key * 231 key_load_public_rsa1(int fd, const char *filename, char **commentp) 232 { 233 Buffer buffer; 234 Key *pub; 235 struct stat st; 236 char *cp; 237 int i; 238 off_t len; 239 240 if (fstat(fd, &st) < 0) { 241 error("fstat for key file %.200s failed: %.100s", 242 filename, strerror(errno)); 243 return NULL; 244 } 245 len = st.st_size; 246 247 buffer_init(&buffer); 248 cp = buffer_append_space(&buffer, len); 249 250 if (read(fd, cp, (size_t) len) != (size_t) len) { 251 debug("Read from key file %.200s failed: %.100s", filename, 252 strerror(errno)); 253 buffer_free(&buffer); 254 return NULL; 255 } 256 257 /* Check that it is at least big enough to contain the ID string. */ 258 if (len < sizeof(authfile_id_string)) { 259 debug3("Not a RSA1 key file %.200s.", filename); 260 buffer_free(&buffer); 261 return NULL; 262 } 263 /* 264 * Make sure it begins with the id string. Consume the id string 265 * from the buffer. 266 */ 267 for (i = 0; i < sizeof(authfile_id_string); i++) 268 if (buffer_get_char(&buffer) != authfile_id_string[i]) { 269 debug3("Not a RSA1 key file %.200s.", filename); 270 buffer_free(&buffer); 271 return NULL; 272 } 273 /* Skip cipher type and reserved data. */ 274 (void) buffer_get_char(&buffer); /* cipher type */ 275 (void) buffer_get_int(&buffer); /* reserved */ 276 277 /* Read the public key from the buffer. */ 278 (void) buffer_get_int(&buffer); 279 pub = key_new(KEY_RSA1); 280 buffer_get_bignum(&buffer, pub->rsa->n); 281 buffer_get_bignum(&buffer, pub->rsa->e); 282 if (commentp) 283 *commentp = buffer_get_string(&buffer, NULL); 284 /* The encrypted private part is not parsed by this function. */ 285 286 buffer_free(&buffer); 287 return pub; 288 } 289 290 /* load public key from private-key file, works only for SSH v1 */ 291 Key * 292 key_load_public_type(int type, const char *filename, char **commentp) 293 { 294 Key *pub; 295 int fd; 296 297 if (type == KEY_RSA1) { 298 fd = open(filename, O_RDONLY); 299 if (fd < 0) 300 return NULL; 301 pub = key_load_public_rsa1(fd, filename, commentp); 302 close(fd); 303 return pub; 304 } 305 return NULL; 306 } 307 308 /* 309 * Loads the private key from the file. Returns 0 if an error is encountered 310 * (file does not exist or is not readable, or passphrase is bad). This 311 * initializes the private key. 312 * Assumes we are called under uid of the owner of the file. 313 */ 314 315 static Key * 316 key_load_private_rsa1(int fd, const char *filename, const char *passphrase, 317 char **commentp) 318 { 319 int i, check1, check2, cipher_type; 320 off_t len; 321 Buffer buffer, decrypted; 322 u_char *cp; 323 CipherContext ciphercontext; 324 Cipher *cipher; 325 Key *prv = NULL; 326 struct stat st; 327 328 if (fstat(fd, &st) < 0) { 329 error("fstat for key file %.200s failed: %.100s", 330 filename, strerror(errno)); 331 close(fd); 332 return NULL; 333 } 334 len = st.st_size; 335 336 buffer_init(&buffer); 337 cp = buffer_append_space(&buffer, len); 338 339 if (read(fd, cp, (size_t) len) != (size_t) len) { 340 debug("Read from key file %.200s failed: %.100s", filename, 341 strerror(errno)); 342 buffer_free(&buffer); 343 close(fd); 344 return NULL; 345 } 346 347 /* Check that it is at least big enough to contain the ID string. */ 348 if (len < sizeof(authfile_id_string)) { 349 debug3("Not a RSA1 key file %.200s.", filename); 350 buffer_free(&buffer); 351 close(fd); 352 return NULL; 353 } 354 /* 355 * Make sure it begins with the id string. Consume the id string 356 * from the buffer. 357 */ 358 for (i = 0; i < sizeof(authfile_id_string); i++) 359 if (buffer_get_char(&buffer) != authfile_id_string[i]) { 360 debug3("Not a RSA1 key file %.200s.", filename); 361 buffer_free(&buffer); 362 close(fd); 363 return NULL; 364 } 365 366 /* Read cipher type. */ 367 cipher_type = buffer_get_char(&buffer); 368 (void) buffer_get_int(&buffer); /* Reserved data. */ 369 370 /* Read the public key from the buffer. */ 371 (void) buffer_get_int(&buffer); 372 prv = key_new_private(KEY_RSA1); 373 374 buffer_get_bignum(&buffer, prv->rsa->n); 375 buffer_get_bignum(&buffer, prv->rsa->e); 376 if (commentp) 377 *commentp = buffer_get_string(&buffer, NULL); 378 else 379 xfree(buffer_get_string(&buffer, NULL)); 380 381 /* Check that it is a supported cipher. */ 382 cipher = cipher_by_number(cipher_type); 383 if (cipher == NULL) { 384 debug("Unsupported cipher %d used in key file %.200s.", 385 cipher_type, filename); 386 buffer_free(&buffer); 387 goto fail; 388 } 389 /* Initialize space for decrypted data. */ 390 buffer_init(&decrypted); 391 cp = buffer_append_space(&decrypted, buffer_len(&buffer)); 392 393 /* Rest of the buffer is encrypted. Decrypt it using the passphrase. */ 394 cipher_set_key_string(&ciphercontext, cipher, passphrase, 395 CIPHER_DECRYPT); 396 cipher_crypt(&ciphercontext, cp, 397 buffer_ptr(&buffer), buffer_len(&buffer)); 398 cipher_cleanup(&ciphercontext); 399 memset(&ciphercontext, 0, sizeof(ciphercontext)); 400 buffer_free(&buffer); 401 402 check1 = buffer_get_char(&decrypted); 403 check2 = buffer_get_char(&decrypted); 404 if (check1 != buffer_get_char(&decrypted) || 405 check2 != buffer_get_char(&decrypted)) { 406 if (strcmp(passphrase, "") != 0) 407 debug("Bad passphrase supplied for key file %.200s.", 408 filename); 409 /* Bad passphrase. */ 410 buffer_free(&decrypted); 411 goto fail; 412 } 413 /* Read the rest of the private key. */ 414 buffer_get_bignum(&decrypted, prv->rsa->d); 415 buffer_get_bignum(&decrypted, prv->rsa->iqmp); /* u */ 416 /* in SSL and SSH v1 p and q are exchanged */ 417 buffer_get_bignum(&decrypted, prv->rsa->q); /* p */ 418 buffer_get_bignum(&decrypted, prv->rsa->p); /* q */ 419 420 /* calculate p-1 and q-1 */ 421 rsa_generate_additional_parameters(prv->rsa); 422 423 buffer_free(&decrypted); 424 425 /* enable blinding */ 426 if (RSA_blinding_on(prv->rsa, NULL) != 1) { 427 error("key_load_private_rsa1: RSA_blinding_on failed"); 428 goto fail; 429 } 430 close(fd); 431 return prv; 432 433 fail: 434 if (commentp) 435 xfree(*commentp); 436 close(fd); 437 key_free(prv); 438 return NULL; 439 } 440 441 Key * 442 key_load_private_pem(int fd, int type, const char *passphrase, 443 char **commentp) 444 { 445 FILE *fp; 446 EVP_PKEY *pk = NULL; 447 Key *prv = NULL; 448 char *name = "<no key>"; 449 450 fp = fdopen(fd, "r"); 451 if (fp == NULL) { 452 error("fdopen failed: %s", strerror(errno)); 453 close(fd); 454 return NULL; 455 } 456 pk = PEM_read_PrivateKey(fp, NULL, NULL, (char *)passphrase); 457 if (pk == NULL) { 458 debug("PEM_read_PrivateKey failed"); 459 (void)ERR_get_error(); 460 } else if (pk->type == EVP_PKEY_RSA && 461 (type == KEY_UNSPEC||type==KEY_RSA)) { 462 prv = key_new(KEY_UNSPEC); 463 prv->rsa = EVP_PKEY_get1_RSA(pk); 464 prv->type = KEY_RSA; 465 name = "rsa w/o comment"; 466 #ifdef DEBUG_PK 467 RSA_print_fp(stderr, prv->rsa, 8); 468 #endif 469 if (RSA_blinding_on(prv->rsa, NULL) != 1) { 470 error("key_load_private_pem: RSA_blinding_on failed"); 471 key_free(prv); 472 prv = NULL; 473 } 474 } else if (pk->type == EVP_PKEY_DSA && 475 (type == KEY_UNSPEC||type==KEY_DSA)) { 476 prv = key_new(KEY_UNSPEC); 477 prv->dsa = EVP_PKEY_get1_DSA(pk); 478 prv->type = KEY_DSA; 479 name = "dsa w/o comment"; 480 #ifdef DEBUG_PK 481 DSA_print_fp(stderr, prv->dsa, 8); 482 #endif 483 } else { 484 error("PEM_read_PrivateKey: mismatch or " 485 "unknown EVP_PKEY save_type %d", pk->save_type); 486 } 487 fclose(fp); 488 if (pk != NULL) 489 EVP_PKEY_free(pk); 490 if (prv != NULL && commentp) 491 *commentp = xstrdup(name); 492 debug("read PEM private key done: type %s", 493 prv ? key_type(prv) : "<unknown>"); 494 return prv; 495 } 496 497 static int 498 key_perm_ok(int fd, const char *filename) 499 { 500 struct stat st; 501 502 if (fstat(fd, &st) < 0) 503 return 0; 504 /* 505 * if a key owned by the user is accessed, then we check the 506 * permissions of the file. if the key owned by a different user, 507 * then we don't care. 508 */ 509 if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0) { 510 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 511 error("@ WARNING: UNPROTECTED PRIVATE KEY FILE! @"); 512 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 513 error("Permissions 0%3.3o for '%s' are too open.", 514 (u_int)st.st_mode & 0777, filename); 515 error("It is recommended that your private key files are NOT accessible by others."); 516 error("This private key will be ignored."); 517 return 0; 518 } 519 return 1; 520 } 521 522 Key * 523 key_load_private_type(int type, const char *filename, const char *passphrase, 524 char **commentp) 525 { 526 int fd; 527 528 fd = open(filename, O_RDONLY); 529 if (fd < 0) 530 return NULL; 531 if (!key_perm_ok(fd, filename)) { 532 error("bad permissions: ignore key: %s", filename); 533 close(fd); 534 return NULL; 535 } 536 switch (type) { 537 case KEY_RSA1: 538 return key_load_private_rsa1(fd, filename, passphrase, 539 commentp); 540 /* closes fd */ 541 break; 542 case KEY_DSA: 543 case KEY_RSA: 544 case KEY_UNSPEC: 545 return key_load_private_pem(fd, type, passphrase, commentp); 546 /* closes fd */ 547 break; 548 default: 549 close(fd); 550 break; 551 } 552 return NULL; 553 } 554 555 Key * 556 key_load_private(const char *filename, const char *passphrase, 557 char **commentp) 558 { 559 Key *pub, *prv; 560 int fd; 561 562 fd = open(filename, O_RDONLY); 563 if (fd < 0) 564 return NULL; 565 if (!key_perm_ok(fd, filename)) { 566 error("bad permissions: ignore key: %s", filename); 567 close(fd); 568 return NULL; 569 } 570 pub = key_load_public_rsa1(fd, filename, commentp); 571 lseek(fd, (off_t) 0, SEEK_SET); /* rewind */ 572 if (pub == NULL) { 573 /* closes fd */ 574 prv = key_load_private_pem(fd, KEY_UNSPEC, passphrase, NULL); 575 /* use the filename as a comment for PEM */ 576 if (commentp && prv) 577 *commentp = xstrdup(filename); 578 } else { 579 /* it's a SSH v1 key if the public key part is readable */ 580 key_free(pub); 581 /* closes fd */ 582 prv = key_load_private_rsa1(fd, filename, passphrase, NULL); 583 } 584 return prv; 585 } 586 587 static int 588 key_try_load_public(Key *k, const char *filename, char **commentp) 589 { 590 FILE *f; 591 char line[4096]; 592 char *cp; 593 594 f = fopen(filename, "r"); 595 if (f != NULL) { 596 while (fgets(line, sizeof(line), f)) { 597 line[sizeof(line)-1] = '\0'; 598 cp = line; 599 switch (*cp) { 600 case '#': 601 case '\n': 602 case '\0': 603 continue; 604 } 605 /* Skip leading whitespace. */ 606 for (; *cp && (*cp == ' ' || *cp == '\t'); cp++) 607 ; 608 if (*cp) { 609 if (key_read(k, &cp) == 1) { 610 if (commentp) 611 *commentp=xstrdup(filename); 612 fclose(f); 613 return 1; 614 } 615 } 616 } 617 fclose(f); 618 } 619 return 0; 620 } 621 622 /* load public key from ssh v1 private or any pubkey file */ 623 Key * 624 key_load_public(const char *filename, char **commentp) 625 { 626 Key *pub; 627 char file[MAXPATHLEN]; 628 629 /* try rsa1 private key */ 630 pub = key_load_public_type(KEY_RSA1, filename, commentp); 631 if (pub != NULL) 632 return pub; 633 634 /* try rsa1 public key */ 635 pub = key_new(KEY_RSA1); 636 if (key_try_load_public(pub, filename, commentp) == 1) 637 return pub; 638 key_free(pub); 639 640 /* try ssh2 public key */ 641 pub = key_new(KEY_UNSPEC); 642 if (key_try_load_public(pub, filename, commentp) == 1) 643 return pub; 644 if ((strlcpy(file, filename, sizeof file) < sizeof(file)) && 645 (strlcat(file, ".pub", sizeof file) < sizeof(file)) && 646 (key_try_load_public(pub, file, commentp) == 1)) 647 return pub; 648 key_free(pub); 649 return NULL; 650 } 651