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 1.50 2002/06/24 14:55:38 markus Exp $"); 40 41 #pragma ident "%Z%%M% %I% %E% SMI" 42 43 #include <openssl/err.h> 44 #include <openssl/evp.h> 45 #include <openssl/pem.h> 46 47 #include "cipher.h" 48 #include "xmalloc.h" 49 #include "buffer.h" 50 #include "bufaux.h" 51 #include "key.h" 52 #include "ssh.h" 53 #include "log.h" 54 #include "authfile.h" 55 #include "rsa.h" 56 57 /* Version identification string for SSH v1 identity files. */ 58 static const char authfile_id_string[] = 59 "SSH PRIVATE KEY FILE FORMAT 1.1\n"; 60 61 /* 62 * Saves the authentication (private) key in a file, encrypting it with 63 * passphrase. The identification of the file (lowest 64 bits of n) will 64 * precede the key to provide identification of the key without needing a 65 * passphrase. 66 */ 67 68 static int 69 key_save_private_rsa1(Key *key, const char *filename, const char *passphrase, 70 const char *comment) 71 { 72 Buffer buffer, encrypted; 73 u_char buf[100], *cp; 74 int fd, i, cipher_num; 75 CipherContext ciphercontext; 76 Cipher *cipher; 77 u_int32_t rand; 78 79 /* 80 * If the passphrase is empty, use SSH_CIPHER_NONE to ease converting 81 * to another cipher; otherwise use SSH_AUTHFILE_CIPHER. 82 */ 83 cipher_num = (strcmp(passphrase, "") == 0) ? 84 SSH_CIPHER_NONE : SSH_AUTHFILE_CIPHER; 85 if ((cipher = cipher_by_number(cipher_num)) == NULL) 86 fatal("save_private_key_rsa: bad cipher"); 87 88 /* This buffer is used to built the secret part of the private key. */ 89 buffer_init(&buffer); 90 91 /* Put checkbytes for checking passphrase validity. */ 92 rand = arc4random(); 93 buf[0] = rand & 0xff; 94 buf[1] = (rand >> 8) & 0xff; 95 buf[2] = buf[0]; 96 buf[3] = buf[1]; 97 buffer_append(&buffer, buf, 4); 98 99 /* 100 * Store the private key (n and e will not be stored because they 101 * will be stored in plain text, and storing them also in encrypted 102 * format would just give known plaintext). 103 */ 104 buffer_put_bignum(&buffer, key->rsa->d); 105 buffer_put_bignum(&buffer, key->rsa->iqmp); 106 buffer_put_bignum(&buffer, key->rsa->q); /* reverse from SSL p */ 107 buffer_put_bignum(&buffer, key->rsa->p); /* reverse from SSL q */ 108 109 /* Pad the part to be encrypted until its size is a multiple of 8. */ 110 while (buffer_len(&buffer) % 8 != 0) 111 buffer_put_char(&buffer, 0); 112 113 /* This buffer will be used to contain the data in the file. */ 114 buffer_init(&encrypted); 115 116 /* First store keyfile id string. */ 117 for (i = 0; authfile_id_string[i]; i++) 118 buffer_put_char(&encrypted, authfile_id_string[i]); 119 buffer_put_char(&encrypted, 0); 120 121 /* Store cipher type. */ 122 buffer_put_char(&encrypted, cipher_num); 123 buffer_put_int(&encrypted, 0); /* For future extension */ 124 125 /* Store public key. This will be in plain text. */ 126 buffer_put_int(&encrypted, BN_num_bits(key->rsa->n)); 127 buffer_put_bignum(&encrypted, key->rsa->n); 128 buffer_put_bignum(&encrypted, key->rsa->e); 129 buffer_put_cstring(&encrypted, comment); 130 131 /* Allocate space for the private part of the key in the buffer. */ 132 cp = buffer_append_space(&encrypted, buffer_len(&buffer)); 133 134 cipher_set_key_string(&ciphercontext, cipher, passphrase, 135 CIPHER_ENCRYPT); 136 cipher_crypt(&ciphercontext, cp, 137 buffer_ptr(&buffer), buffer_len(&buffer)); 138 cipher_cleanup(&ciphercontext); 139 memset(&ciphercontext, 0, sizeof(ciphercontext)); 140 141 /* Destroy temporary data. */ 142 memset(buf, 0, sizeof(buf)); 143 buffer_free(&buffer); 144 145 fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600); 146 if (fd < 0) { 147 error("open %s failed: %s.", filename, strerror(errno)); 148 return 0; 149 } 150 if (write(fd, buffer_ptr(&encrypted), buffer_len(&encrypted)) != 151 buffer_len(&encrypted)) { 152 error("write to key file %s failed: %s", filename, 153 strerror(errno)); 154 buffer_free(&encrypted); 155 close(fd); 156 unlink(filename); 157 return 0; 158 } 159 close(fd); 160 buffer_free(&encrypted); 161 return 1; 162 } 163 164 /* save SSH v2 key in OpenSSL PEM format */ 165 static int 166 key_save_private_pem(Key *key, const char *filename, const char *_passphrase, 167 const char *comment) 168 { 169 FILE *fp; 170 int fd; 171 int success = 0; 172 int len = strlen(_passphrase); 173 u_char *passphrase = (len > 0) ? (u_char *)_passphrase : NULL; 174 const EVP_CIPHER *cipher = (len > 0) ? EVP_des_ede3_cbc() : NULL; 175 176 if (len > 0 && len <= 4) { 177 error("passphrase too short: have %d bytes, need > 4", len); 178 return 0; 179 } 180 fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600); 181 if (fd < 0) { 182 error("open %s failed: %s.", filename, strerror(errno)); 183 return 0; 184 } 185 fp = fdopen(fd, "w"); 186 if (fp == NULL ) { 187 error("fdopen %s failed: %s.", filename, strerror(errno)); 188 close(fd); 189 return 0; 190 } 191 switch (key->type) { 192 case KEY_DSA: 193 success = PEM_write_DSAPrivateKey(fp, key->dsa, 194 cipher, passphrase, len, NULL, NULL); 195 break; 196 case KEY_RSA: 197 success = PEM_write_RSAPrivateKey(fp, key->rsa, 198 cipher, passphrase, len, NULL, NULL); 199 break; 200 } 201 fclose(fp); 202 return success; 203 } 204 205 int 206 key_save_private(Key *key, const char *filename, const char *passphrase, 207 const char *comment) 208 { 209 switch (key->type) { 210 case KEY_RSA1: 211 return key_save_private_rsa1(key, filename, passphrase, 212 comment); 213 break; 214 case KEY_DSA: 215 case KEY_RSA: 216 return key_save_private_pem(key, filename, passphrase, 217 comment); 218 break; 219 default: 220 break; 221 } 222 error("key_save_private: cannot save key type %d", key->type); 223 return 0; 224 } 225 226 /* 227 * Loads the public part of the ssh v1 key file. Returns NULL if an error was 228 * encountered (the file does not exist or is not readable), and the key 229 * otherwise. 230 */ 231 232 static Key * 233 key_load_public_rsa1(int fd, const char *filename, char **commentp) 234 { 235 Buffer buffer; 236 Key *pub; 237 char *cp; 238 int i; 239 off_t len; 240 241 len = lseek(fd, (off_t) 0, SEEK_END); 242 lseek(fd, (off_t) 0, SEEK_SET); 243 244 buffer_init(&buffer); 245 cp = buffer_append_space(&buffer, len); 246 247 if (read(fd, cp, (size_t) len) != (size_t) len) { 248 debug("Read from key file %.200s failed: %.100s", filename, 249 strerror(errno)); 250 buffer_free(&buffer); 251 return NULL; 252 } 253 254 /* Check that it is at least big enough to contain the ID string. */ 255 if (len < sizeof(authfile_id_string)) { 256 debug3("Not a RSA1 key file %.200s.", filename); 257 buffer_free(&buffer); 258 return NULL; 259 } 260 /* 261 * Make sure it begins with the id string. Consume the id string 262 * from the buffer. 263 */ 264 for (i = 0; i < sizeof(authfile_id_string); i++) 265 if (buffer_get_char(&buffer) != authfile_id_string[i]) { 266 debug3("Not a RSA1 key file %.200s.", filename); 267 buffer_free(&buffer); 268 return NULL; 269 } 270 /* Skip cipher type and reserved data. */ 271 (void) buffer_get_char(&buffer); /* cipher type */ 272 (void) buffer_get_int(&buffer); /* reserved */ 273 274 /* Read the public key from the buffer. */ 275 (void) buffer_get_int(&buffer); 276 pub = key_new(KEY_RSA1); 277 buffer_get_bignum(&buffer, pub->rsa->n); 278 buffer_get_bignum(&buffer, pub->rsa->e); 279 if (commentp) 280 *commentp = buffer_get_string(&buffer, NULL); 281 /* The encrypted private part is not parsed by this function. */ 282 283 buffer_free(&buffer); 284 return pub; 285 } 286 287 /* load public key from private-key file, works only for SSH v1 */ 288 Key * 289 key_load_public_type(int type, const char *filename, char **commentp) 290 { 291 Key *pub; 292 int fd; 293 294 if (type == KEY_RSA1) { 295 fd = open(filename, O_RDONLY); 296 if (fd < 0) 297 return NULL; 298 pub = key_load_public_rsa1(fd, filename, commentp); 299 close(fd); 300 return pub; 301 } 302 return NULL; 303 } 304 305 /* 306 * Loads the private key from the file. Returns 0 if an error is encountered 307 * (file does not exist or is not readable, or passphrase is bad). This 308 * initializes the private key. 309 * Assumes we are called under uid of the owner of the file. 310 */ 311 312 static Key * 313 key_load_private_rsa1(int fd, const char *filename, const char *passphrase, 314 char **commentp) 315 { 316 int i, check1, check2, cipher_type; 317 off_t len; 318 Buffer buffer, decrypted; 319 u_char *cp; 320 CipherContext ciphercontext; 321 Cipher *cipher; 322 Key *prv = NULL; 323 324 len = lseek(fd, (off_t) 0, SEEK_END); 325 lseek(fd, (off_t) 0, SEEK_SET); 326 327 buffer_init(&buffer); 328 cp = buffer_append_space(&buffer, len); 329 330 if (read(fd, cp, (size_t) len) != (size_t) len) { 331 debug("Read from key file %.200s failed: %.100s", filename, 332 strerror(errno)); 333 buffer_free(&buffer); 334 close(fd); 335 return NULL; 336 } 337 338 /* Check that it is at least big enough to contain the ID string. */ 339 if (len < sizeof(authfile_id_string)) { 340 debug3("Not a RSA1 key file %.200s.", filename); 341 buffer_free(&buffer); 342 close(fd); 343 return NULL; 344 } 345 /* 346 * Make sure it begins with the id string. Consume the id string 347 * from the buffer. 348 */ 349 for (i = 0; i < sizeof(authfile_id_string); i++) 350 if (buffer_get_char(&buffer) != authfile_id_string[i]) { 351 debug3("Not a RSA1 key file %.200s.", filename); 352 buffer_free(&buffer); 353 close(fd); 354 return NULL; 355 } 356 357 /* Read cipher type. */ 358 cipher_type = buffer_get_char(&buffer); 359 (void) buffer_get_int(&buffer); /* Reserved data. */ 360 361 /* Read the public key from the buffer. */ 362 (void) buffer_get_int(&buffer); 363 prv = key_new_private(KEY_RSA1); 364 365 buffer_get_bignum(&buffer, prv->rsa->n); 366 buffer_get_bignum(&buffer, prv->rsa->e); 367 if (commentp) 368 *commentp = buffer_get_string(&buffer, NULL); 369 else 370 xfree(buffer_get_string(&buffer, NULL)); 371 372 /* Check that it is a supported cipher. */ 373 cipher = cipher_by_number(cipher_type); 374 if (cipher == NULL) { 375 debug("Unsupported cipher %d used in key file %.200s.", 376 cipher_type, filename); 377 buffer_free(&buffer); 378 goto fail; 379 } 380 /* Initialize space for decrypted data. */ 381 buffer_init(&decrypted); 382 cp = buffer_append_space(&decrypted, buffer_len(&buffer)); 383 384 /* Rest of the buffer is encrypted. Decrypt it using the passphrase. */ 385 cipher_set_key_string(&ciphercontext, cipher, passphrase, 386 CIPHER_DECRYPT); 387 cipher_crypt(&ciphercontext, cp, 388 buffer_ptr(&buffer), buffer_len(&buffer)); 389 cipher_cleanup(&ciphercontext); 390 memset(&ciphercontext, 0, sizeof(ciphercontext)); 391 buffer_free(&buffer); 392 393 check1 = buffer_get_char(&decrypted); 394 check2 = buffer_get_char(&decrypted); 395 if (check1 != buffer_get_char(&decrypted) || 396 check2 != buffer_get_char(&decrypted)) { 397 if (strcmp(passphrase, "") != 0) 398 debug("Bad passphrase supplied for key file %.200s.", 399 filename); 400 /* Bad passphrase. */ 401 buffer_free(&decrypted); 402 goto fail; 403 } 404 /* Read the rest of the private key. */ 405 buffer_get_bignum(&decrypted, prv->rsa->d); 406 buffer_get_bignum(&decrypted, prv->rsa->iqmp); /* u */ 407 /* in SSL and SSH v1 p and q are exchanged */ 408 buffer_get_bignum(&decrypted, prv->rsa->q); /* p */ 409 buffer_get_bignum(&decrypted, prv->rsa->p); /* q */ 410 411 /* calculate p-1 and q-1 */ 412 rsa_generate_additional_parameters(prv->rsa); 413 414 buffer_free(&decrypted); 415 close(fd); 416 return prv; 417 418 fail: 419 if (commentp) 420 xfree(*commentp); 421 close(fd); 422 key_free(prv); 423 return NULL; 424 } 425 426 Key * 427 key_load_private_pem(int fd, int type, const char *passphrase, 428 char **commentp) 429 { 430 FILE *fp; 431 EVP_PKEY *pk = NULL; 432 Key *prv = NULL; 433 char *name = "<no key>"; 434 435 fp = fdopen(fd, "r"); 436 if (fp == NULL) { 437 error("fdopen failed: %s", strerror(errno)); 438 close(fd); 439 return NULL; 440 } 441 pk = PEM_read_PrivateKey(fp, NULL, NULL, (char *)passphrase); 442 if (pk == NULL) { 443 debug("PEM_read_PrivateKey failed"); 444 (void)ERR_get_error(); 445 } else if (pk->type == EVP_PKEY_RSA && 446 (type == KEY_UNSPEC||type==KEY_RSA)) { 447 prv = key_new(KEY_UNSPEC); 448 prv->rsa = EVP_PKEY_get1_RSA(pk); 449 prv->type = KEY_RSA; 450 name = "rsa w/o comment"; 451 #ifdef DEBUG_PK 452 RSA_print_fp(stderr, prv->rsa, 8); 453 #endif 454 } else if (pk->type == EVP_PKEY_DSA && 455 (type == KEY_UNSPEC||type==KEY_DSA)) { 456 prv = key_new(KEY_UNSPEC); 457 prv->dsa = EVP_PKEY_get1_DSA(pk); 458 prv->type = KEY_DSA; 459 name = "dsa w/o comment"; 460 #ifdef DEBUG_PK 461 DSA_print_fp(stderr, prv->dsa, 8); 462 #endif 463 } else { 464 error("PEM_read_PrivateKey: mismatch or " 465 "unknown EVP_PKEY save_type %d", pk->save_type); 466 } 467 fclose(fp); 468 if (pk != NULL) 469 EVP_PKEY_free(pk); 470 if (prv != NULL && commentp) 471 *commentp = xstrdup(name); 472 debug("read PEM private key done: type %s", 473 prv ? key_type(prv) : "<unknown>"); 474 return prv; 475 } 476 477 static int 478 key_perm_ok(int fd, const char *filename) 479 { 480 struct stat st; 481 482 if (fstat(fd, &st) < 0) 483 return 0; 484 /* 485 * if a key owned by the user is accessed, then we check the 486 * permissions of the file. if the key owned by a different user, 487 * then we don't care. 488 */ 489 #ifdef HAVE_CYGWIN 490 if (check_ntsec(filename)) 491 #endif 492 if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0) { 493 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 494 error("@ WARNING: UNPROTECTED PRIVATE KEY FILE! @"); 495 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 496 error("Permissions 0%3.3o for '%s' are too open.", 497 (int)(st.st_mode & 0777), filename); 498 error("It is recommended that your private key files are NOT accessible by others."); 499 error("This private key will be ignored."); 500 return 0; 501 } 502 return 1; 503 } 504 505 Key * 506 key_load_private_type(int type, const char *filename, const char *passphrase, 507 char **commentp) 508 { 509 int fd; 510 511 fd = open(filename, O_RDONLY); 512 if (fd < 0) 513 return NULL; 514 if (!key_perm_ok(fd, filename)) { 515 error("bad permissions: ignore key: %s", filename); 516 close(fd); 517 return NULL; 518 } 519 switch (type) { 520 case KEY_RSA1: 521 return key_load_private_rsa1(fd, filename, passphrase, 522 commentp); 523 /* closes fd */ 524 break; 525 case KEY_DSA: 526 case KEY_RSA: 527 case KEY_UNSPEC: 528 return key_load_private_pem(fd, type, passphrase, commentp); 529 /* closes fd */ 530 break; 531 default: 532 close(fd); 533 break; 534 } 535 return NULL; 536 } 537 538 Key * 539 key_load_private(const char *filename, const char *passphrase, 540 char **commentp) 541 { 542 Key *pub, *prv; 543 int fd; 544 545 fd = open(filename, O_RDONLY); 546 if (fd < 0) 547 return NULL; 548 if (!key_perm_ok(fd, filename)) { 549 error("bad permissions: ignore key: %s", filename); 550 close(fd); 551 return NULL; 552 } 553 pub = key_load_public_rsa1(fd, filename, commentp); 554 lseek(fd, (off_t) 0, SEEK_SET); /* rewind */ 555 if (pub == NULL) { 556 /* closes fd */ 557 prv = key_load_private_pem(fd, KEY_UNSPEC, passphrase, NULL); 558 /* use the filename as a comment for PEM */ 559 if (commentp && prv) 560 *commentp = xstrdup(filename); 561 } else { 562 /* it's a SSH v1 key if the public key part is readable */ 563 key_free(pub); 564 /* closes fd */ 565 prv = key_load_private_rsa1(fd, filename, passphrase, NULL); 566 } 567 return prv; 568 } 569 570 static int 571 key_try_load_public(Key *k, const char *filename, char **commentp) 572 { 573 FILE *f; 574 char line[4096]; 575 char *cp; 576 577 f = fopen(filename, "r"); 578 if (f != NULL) { 579 while (fgets(line, sizeof(line), f)) { 580 line[sizeof(line)-1] = '\0'; 581 cp = line; 582 switch (*cp) { 583 case '#': 584 case '\n': 585 case '\0': 586 continue; 587 } 588 /* Skip leading whitespace. */ 589 for (; *cp && (*cp == ' ' || *cp == '\t'); cp++) 590 ; 591 if (*cp) { 592 if (key_read(k, &cp) == 1) { 593 if (commentp) 594 *commentp=xstrdup(filename); 595 fclose(f); 596 return 1; 597 } 598 } 599 } 600 fclose(f); 601 } 602 return 0; 603 } 604 605 /* load public key from ssh v1 private or any pubkey file */ 606 Key * 607 key_load_public(const char *filename, char **commentp) 608 { 609 Key *pub; 610 char file[MAXPATHLEN]; 611 612 pub = key_load_public_type(KEY_RSA1, filename, commentp); 613 if (pub != NULL) 614 return pub; 615 pub = key_new(KEY_UNSPEC); 616 if (key_try_load_public(pub, filename, commentp) == 1) 617 return pub; 618 if ((strlcpy(file, filename, sizeof file) < sizeof(file)) && 619 (strlcat(file, ".pub", sizeof file) < sizeof(file)) && 620 (key_try_load_public(pub, file, commentp) == 1)) 621 return pub; 622 key_free(pub); 623 return NULL; 624 } 625