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 1.45 2001/12/29 21:56:01 stevesk 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; 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 if (strcmp(passphrase, "") == 0) 82 cipher = cipher_by_number(SSH_CIPHER_NONE); 83 else 84 cipher = cipher_by_number(SSH_AUTHFILE_CIPHER); 85 if (cipher == 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->number); 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(&ciphercontext, cp, 136 buffer_ptr(&buffer), buffer_len(&buffer)); 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 char *passphrase = (len > 0) ? (char *)_passphrase : NULL; 172 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 char *cp; 236 int i; 237 off_t len; 238 239 len = lseek(fd, (off_t) 0, SEEK_END); 240 lseek(fd, (off_t) 0, SEEK_SET); 241 242 buffer_init(&buffer); 243 cp = buffer_append_space(&buffer, len); 244 245 if (read(fd, cp, (size_t) len) != (size_t) len) { 246 debug("Read from key file %.200s failed: %.100s", filename, 247 strerror(errno)); 248 buffer_free(&buffer); 249 return NULL; 250 } 251 252 /* Check that it is at least big enough to contain the ID string. */ 253 if (len < sizeof(authfile_id_string)) { 254 debug3("Not a RSA1 key file %.200s.", filename); 255 buffer_free(&buffer); 256 return NULL; 257 } 258 /* 259 * Make sure it begins with the id string. Consume the id string 260 * from the buffer. 261 */ 262 for (i = 0; i < sizeof(authfile_id_string); i++) 263 if (buffer_get_char(&buffer) != authfile_id_string[i]) { 264 debug3("Not a RSA1 key file %.200s.", filename); 265 buffer_free(&buffer); 266 return NULL; 267 } 268 /* Skip cipher type and reserved data. */ 269 (void) buffer_get_char(&buffer); /* cipher type */ 270 (void) buffer_get_int(&buffer); /* reserved */ 271 272 /* Read the public key from the buffer. */ 273 buffer_get_int(&buffer); 274 pub = key_new(KEY_RSA1); 275 buffer_get_bignum(&buffer, pub->rsa->n); 276 buffer_get_bignum(&buffer, pub->rsa->e); 277 if (commentp) 278 *commentp = buffer_get_string(&buffer, NULL); 279 /* The encrypted private part is not parsed by this function. */ 280 281 buffer_free(&buffer); 282 return pub; 283 } 284 285 /* load public key from private-key file, works only for SSH v1 */ 286 Key * 287 key_load_public_type(int type, const char *filename, char **commentp) 288 { 289 Key *pub; 290 int fd; 291 292 if (type == KEY_RSA1) { 293 fd = open(filename, O_RDONLY); 294 if (fd < 0) 295 return NULL; 296 pub = key_load_public_rsa1(fd, filename, commentp); 297 close(fd); 298 return pub; 299 } 300 return NULL; 301 } 302 303 /* 304 * Loads the private key from the file. Returns 0 if an error is encountered 305 * (file does not exist or is not readable, or passphrase is bad). This 306 * initializes the private key. 307 * Assumes we are called under uid of the owner of the file. 308 */ 309 310 static Key * 311 key_load_private_rsa1(int fd, const char *filename, const char *passphrase, 312 char **commentp) 313 { 314 int i, check1, check2, cipher_type; 315 off_t len; 316 Buffer buffer, decrypted; 317 u_char *cp; 318 CipherContext ciphercontext; 319 Cipher *cipher; 320 Key *prv = NULL; 321 322 len = lseek(fd, (off_t) 0, SEEK_END); 323 lseek(fd, (off_t) 0, SEEK_SET); 324 325 buffer_init(&buffer); 326 cp = buffer_append_space(&buffer, len); 327 328 if (read(fd, cp, (size_t) len) != (size_t) len) { 329 debug("Read from key file %.200s failed: %.100s", filename, 330 strerror(errno)); 331 buffer_free(&buffer); 332 close(fd); 333 return NULL; 334 } 335 336 /* Check that it is at least big enough to contain the ID string. */ 337 if (len < sizeof(authfile_id_string)) { 338 debug3("Not a RSA1 key file %.200s.", filename); 339 buffer_free(&buffer); 340 close(fd); 341 return NULL; 342 } 343 /* 344 * Make sure it begins with the id string. Consume the id string 345 * from the buffer. 346 */ 347 for (i = 0; i < sizeof(authfile_id_string); i++) 348 if (buffer_get_char(&buffer) != authfile_id_string[i]) { 349 debug3("Not a RSA1 key file %.200s.", filename); 350 buffer_free(&buffer); 351 close(fd); 352 return NULL; 353 } 354 355 /* Read cipher type. */ 356 cipher_type = buffer_get_char(&buffer); 357 (void) buffer_get_int(&buffer); /* Reserved data. */ 358 359 /* Read the public key from the buffer. */ 360 buffer_get_int(&buffer); 361 prv = key_new_private(KEY_RSA1); 362 363 buffer_get_bignum(&buffer, prv->rsa->n); 364 buffer_get_bignum(&buffer, prv->rsa->e); 365 if (commentp) 366 *commentp = buffer_get_string(&buffer, NULL); 367 else 368 xfree(buffer_get_string(&buffer, NULL)); 369 370 /* Check that it is a supported cipher. */ 371 cipher = cipher_by_number(cipher_type); 372 if (cipher == NULL) { 373 debug("Unsupported cipher %d used in key file %.200s.", 374 cipher_type, filename); 375 buffer_free(&buffer); 376 goto fail; 377 } 378 /* Initialize space for decrypted data. */ 379 buffer_init(&decrypted); 380 cp = buffer_append_space(&decrypted, buffer_len(&buffer)); 381 382 /* Rest of the buffer is encrypted. Decrypt it using the passphrase. */ 383 cipher_set_key_string(&ciphercontext, cipher, passphrase); 384 cipher_decrypt(&ciphercontext, cp, 385 buffer_ptr(&buffer), buffer_len(&buffer)); 386 memset(&ciphercontext, 0, sizeof(ciphercontext)); 387 buffer_free(&buffer); 388 389 check1 = buffer_get_char(&decrypted); 390 check2 = buffer_get_char(&decrypted); 391 if (check1 != buffer_get_char(&decrypted) || 392 check2 != buffer_get_char(&decrypted)) { 393 if (strcmp(passphrase, "") != 0) 394 debug("Bad passphrase supplied for key file %.200s.", 395 filename); 396 /* Bad passphrase. */ 397 buffer_free(&decrypted); 398 goto fail; 399 } 400 /* Read the rest of the private key. */ 401 buffer_get_bignum(&decrypted, prv->rsa->d); 402 buffer_get_bignum(&decrypted, prv->rsa->iqmp); /* u */ 403 /* in SSL and SSH v1 p and q are exchanged */ 404 buffer_get_bignum(&decrypted, prv->rsa->q); /* p */ 405 buffer_get_bignum(&decrypted, prv->rsa->p); /* q */ 406 407 /* calculate p-1 and q-1 */ 408 rsa_generate_additional_parameters(prv->rsa); 409 410 buffer_free(&decrypted); 411 close(fd); 412 return prv; 413 414 fail: 415 if (commentp) 416 xfree(*commentp); 417 close(fd); 418 key_free(prv); 419 return NULL; 420 } 421 422 static Key * 423 key_load_private_pem(int fd, int type, const char *passphrase, 424 char **commentp) 425 { 426 FILE *fp; 427 EVP_PKEY *pk = NULL; 428 Key *prv = NULL; 429 char *name = "<no key>"; 430 431 fp = fdopen(fd, "r"); 432 if (fp == NULL) { 433 error("fdopen failed: %s", strerror(errno)); 434 close(fd); 435 return NULL; 436 } 437 pk = PEM_read_PrivateKey(fp, NULL, NULL, (char *)passphrase); 438 if (pk == NULL) { 439 debug("PEM_read_PrivateKey failed"); 440 (void)ERR_get_error(); 441 } else if (pk->type == EVP_PKEY_RSA && 442 (type == KEY_UNSPEC||type==KEY_RSA)) { 443 prv = key_new(KEY_UNSPEC); 444 prv->rsa = EVP_PKEY_get1_RSA(pk); 445 prv->type = KEY_RSA; 446 name = "rsa w/o comment"; 447 #ifdef DEBUG_PK 448 RSA_print_fp(stderr, prv->rsa, 8); 449 #endif 450 } else if (pk->type == EVP_PKEY_DSA && 451 (type == KEY_UNSPEC||type==KEY_DSA)) { 452 prv = key_new(KEY_UNSPEC); 453 prv->dsa = EVP_PKEY_get1_DSA(pk); 454 prv->type = KEY_DSA; 455 name = "dsa w/o comment"; 456 #ifdef DEBUG_PK 457 DSA_print_fp(stderr, prv->dsa, 8); 458 #endif 459 } else { 460 error("PEM_read_PrivateKey: mismatch or " 461 "unknown EVP_PKEY save_type %d", pk->save_type); 462 } 463 fclose(fp); 464 if (pk != NULL) 465 EVP_PKEY_free(pk); 466 if (prv != NULL && commentp) 467 *commentp = xstrdup(name); 468 debug("read PEM private key done: type %s", 469 prv ? key_type(prv) : "<unknown>"); 470 return prv; 471 } 472 473 static int 474 key_perm_ok(int fd, const char *filename) 475 { 476 struct stat st; 477 478 if (fstat(fd, &st) < 0) 479 return 0; 480 /* 481 * if a key owned by the user is accessed, then we check the 482 * permissions of the file. if the key owned by a different user, 483 * then we don't care. 484 */ 485 if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0) { 486 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 487 error("@ WARNING: UNPROTECTED PRIVATE KEY FILE! @"); 488 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 489 error("Permissions 0%3.3o for '%s' are too open.", 490 st.st_mode & 0777, filename); 491 error("It is recommended that your private key files are NOT accessible by others."); 492 error("This private key will be ignored."); 493 return 0; 494 } 495 return 1; 496 } 497 498 Key * 499 key_load_private_type(int type, const char *filename, const char *passphrase, 500 char **commentp) 501 { 502 int fd; 503 504 fd = open(filename, O_RDONLY); 505 if (fd < 0) 506 return NULL; 507 if (!key_perm_ok(fd, filename)) { 508 error("bad permissions: ignore key: %s", filename); 509 close(fd); 510 return NULL; 511 } 512 switch (type) { 513 case KEY_RSA1: 514 return key_load_private_rsa1(fd, filename, passphrase, 515 commentp); 516 /* closes fd */ 517 break; 518 case KEY_DSA: 519 case KEY_RSA: 520 case KEY_UNSPEC: 521 return key_load_private_pem(fd, type, passphrase, commentp); 522 /* closes fd */ 523 break; 524 default: 525 close(fd); 526 break; 527 } 528 return NULL; 529 } 530 531 Key * 532 key_load_private(const char *filename, const char *passphrase, 533 char **commentp) 534 { 535 Key *pub, *prv; 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 pub = key_load_public_rsa1(fd, filename, commentp); 547 lseek(fd, (off_t) 0, SEEK_SET); /* rewind */ 548 if (pub == NULL) { 549 /* closes fd */ 550 prv = key_load_private_pem(fd, KEY_UNSPEC, passphrase, NULL); 551 /* use the filename as a comment for PEM */ 552 if (commentp && prv) 553 *commentp = xstrdup(filename); 554 } else { 555 /* it's a SSH v1 key if the public key part is readable */ 556 key_free(pub); 557 /* closes fd */ 558 prv = key_load_private_rsa1(fd, filename, passphrase, NULL); 559 } 560 return prv; 561 } 562 563 static int 564 key_try_load_public(Key *k, const char *filename, char **commentp) 565 { 566 FILE *f; 567 char line[4096]; 568 char *cp; 569 570 f = fopen(filename, "r"); 571 if (f != NULL) { 572 while (fgets(line, sizeof(line), f)) { 573 line[sizeof(line)-1] = '\0'; 574 cp = line; 575 switch (*cp) { 576 case '#': 577 case '\n': 578 case '\0': 579 continue; 580 } 581 /* Skip leading whitespace. */ 582 for (; *cp && (*cp == ' ' || *cp == '\t'); cp++) 583 ; 584 if (*cp) { 585 if (key_read(k, &cp) == 1) { 586 if (commentp) 587 *commentp=xstrdup(filename); 588 fclose(f); 589 return 1; 590 } 591 } 592 } 593 fclose(f); 594 } 595 return 0; 596 } 597 598 /* load public key from ssh v1 private or any pubkey file */ 599 Key * 600 key_load_public(const char *filename, char **commentp) 601 { 602 Key *pub; 603 char file[MAXPATHLEN]; 604 605 pub = key_load_public_type(KEY_RSA1, filename, commentp); 606 if (pub != NULL) 607 return pub; 608 pub = key_new(KEY_UNSPEC); 609 if (key_try_load_public(pub, filename, commentp) == 1) 610 return pub; 611 if ((strlcpy(file, filename, sizeof file) < sizeof(file)) && 612 (strlcat(file, ".pub", sizeof file) < sizeof(file)) && 613 (key_try_load_public(pub, file, commentp) == 1)) 614 return pub; 615 key_free(pub); 616 return NULL; 617 } 618