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 1.37 2001/06/23 15:12:17 itojun 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 54 /* Version identification string for SSH v1 identity files. */ 55 static const char authfile_id_string[] = 56 "SSH PRIVATE KEY FILE FORMAT 1.1\n"; 57 58 /* 59 * Saves the authentication (private) key in a file, encrypting it with 60 * passphrase. The identification of the file (lowest 64 bits of n) will 61 * precede the key to provide identification of the key without needing a 62 * passphrase. 63 */ 64 65 static int 66 key_save_private_rsa1(Key *key, const char *filename, const char *passphrase, 67 const char *comment) 68 { 69 Buffer buffer, encrypted; 70 char buf[100], *cp; 71 int fd, i; 72 CipherContext ciphercontext; 73 Cipher *cipher; 74 u_int32_t rand; 75 76 /* 77 * If the passphrase is empty, use SSH_CIPHER_NONE to ease converting 78 * to another cipher; otherwise use SSH_AUTHFILE_CIPHER. 79 */ 80 if (strcmp(passphrase, "") == 0) 81 cipher = cipher_by_number(SSH_CIPHER_NONE); 82 else 83 cipher = cipher_by_number(SSH_AUTHFILE_CIPHER); 84 if (cipher == NULL) 85 fatal("save_private_key_rsa: bad cipher"); 86 87 /* This buffer is used to built the secret part of the private key. */ 88 buffer_init(&buffer); 89 90 /* Put checkbytes for checking passphrase validity. */ 91 rand = arc4random(); 92 buf[0] = rand & 0xff; 93 buf[1] = (rand >> 8) & 0xff; 94 buf[2] = buf[0]; 95 buf[3] = buf[1]; 96 buffer_append(&buffer, buf, 4); 97 98 /* 99 * Store the private key (n and e will not be stored because they 100 * will be stored in plain text, and storing them also in encrypted 101 * format would just give known plaintext). 102 */ 103 buffer_put_bignum(&buffer, key->rsa->d); 104 buffer_put_bignum(&buffer, key->rsa->iqmp); 105 buffer_put_bignum(&buffer, key->rsa->q); /* reverse from SSL p */ 106 buffer_put_bignum(&buffer, key->rsa->p); /* reverse from SSL q */ 107 108 /* Pad the part to be encrypted until its size is a multiple of 8. */ 109 while (buffer_len(&buffer) % 8 != 0) 110 buffer_put_char(&buffer, 0); 111 112 /* This buffer will be used to contain the data in the file. */ 113 buffer_init(&encrypted); 114 115 /* First store keyfile id string. */ 116 for (i = 0; authfile_id_string[i]; i++) 117 buffer_put_char(&encrypted, authfile_id_string[i]); 118 buffer_put_char(&encrypted, 0); 119 120 /* Store cipher type. */ 121 buffer_put_char(&encrypted, cipher->number); 122 buffer_put_int(&encrypted, 0); /* For future extension */ 123 124 /* Store public key. This will be in plain text. */ 125 buffer_put_int(&encrypted, BN_num_bits(key->rsa->n)); 126 buffer_put_bignum(&encrypted, key->rsa->n); 127 buffer_put_bignum(&encrypted, key->rsa->e); 128 buffer_put_cstring(&encrypted, comment); 129 130 /* Allocate space for the private part of the key in the buffer. */ 131 buffer_append_space(&encrypted, &cp, buffer_len(&buffer)); 132 133 cipher_set_key_string(&ciphercontext, cipher, passphrase); 134 cipher_encrypt(&ciphercontext, (u_char *) cp, 135 (u_char *) buffer_ptr(&buffer), buffer_len(&buffer)); 136 memset(&ciphercontext, 0, sizeof(ciphercontext)); 137 138 /* Destroy temporary data. */ 139 memset(buf, 0, sizeof(buf)); 140 buffer_free(&buffer); 141 142 fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600); 143 if (fd < 0) { 144 error("open %s failed: %s.", filename, strerror(errno)); 145 return 0; 146 } 147 if (write(fd, buffer_ptr(&encrypted), buffer_len(&encrypted)) != 148 buffer_len(&encrypted)) { 149 error("write to key file %s failed: %s", filename, 150 strerror(errno)); 151 buffer_free(&encrypted); 152 close(fd); 153 unlink(filename); 154 return 0; 155 } 156 close(fd); 157 buffer_free(&encrypted); 158 return 1; 159 } 160 161 /* save SSH v2 key in OpenSSL PEM format */ 162 static int 163 key_save_private_pem(Key *key, const char *filename, const char *_passphrase, 164 const char *comment) 165 { 166 FILE *fp; 167 int fd; 168 int success = 0; 169 int len = strlen(_passphrase); 170 char *passphrase = (len > 0) ? (char *)_passphrase : NULL; 171 EVP_CIPHER *cipher = (len > 0) ? EVP_des_ede3_cbc() : NULL; 172 173 if (len > 0 && len <= 4) { 174 error("passphrase too short: have %d bytes, need > 4", len); 175 return 0; 176 } 177 fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600); 178 if (fd < 0) { 179 error("open %s failed: %s.", filename, strerror(errno)); 180 return 0; 181 } 182 fp = fdopen(fd, "w"); 183 if (fp == NULL ) { 184 error("fdopen %s failed: %s.", filename, strerror(errno)); 185 close(fd); 186 return 0; 187 } 188 switch (key->type) { 189 case KEY_DSA: 190 success = PEM_write_DSAPrivateKey(fp, key->dsa, 191 cipher, passphrase, len, NULL, NULL); 192 break; 193 case KEY_RSA: 194 success = PEM_write_RSAPrivateKey(fp, key->rsa, 195 cipher, passphrase, len, NULL, NULL); 196 break; 197 } 198 fclose(fp); 199 return success; 200 } 201 202 int 203 key_save_private(Key *key, const char *filename, const char *passphrase, 204 const char *comment) 205 { 206 switch (key->type) { 207 case KEY_RSA1: 208 return key_save_private_rsa1(key, filename, passphrase, 209 comment); 210 break; 211 case KEY_DSA: 212 case KEY_RSA: 213 return key_save_private_pem(key, filename, passphrase, 214 comment); 215 break; 216 default: 217 break; 218 } 219 error("key_save_private: cannot save key type %d", key->type); 220 return 0; 221 } 222 223 /* 224 * Loads the public part of the ssh v1 key file. Returns NULL if an error was 225 * encountered (the file does not exist or is not readable), and the key 226 * otherwise. 227 */ 228 229 static Key * 230 key_load_public_rsa1(int fd, const char *filename, char **commentp) 231 { 232 Buffer buffer; 233 Key *pub; 234 char *cp; 235 int i; 236 off_t len; 237 238 len = lseek(fd, (off_t) 0, SEEK_END); 239 lseek(fd, (off_t) 0, SEEK_SET); 240 241 buffer_init(&buffer); 242 buffer_append_space(&buffer, &cp, len); 243 244 if (read(fd, cp, (size_t) len) != (size_t) len) { 245 debug("Read from key file %.200s failed: %.100s", filename, 246 strerror(errno)); 247 buffer_free(&buffer); 248 return NULL; 249 } 250 251 /* Check that it is at least big enough to contain the ID string. */ 252 if (len < sizeof(authfile_id_string)) { 253 debug3("No RSA1 key file %.200s.", filename); 254 buffer_free(&buffer); 255 return NULL; 256 } 257 /* 258 * Make sure it begins with the id string. Consume the id string 259 * from the buffer. 260 */ 261 for (i = 0; i < sizeof(authfile_id_string); i++) 262 if (buffer_get_char(&buffer) != authfile_id_string[i]) { 263 debug3("No RSA1 key file %.200s.", filename); 264 buffer_free(&buffer); 265 return NULL; 266 } 267 /* Skip cipher type and reserved data. */ 268 (void) buffer_get_char(&buffer); /* cipher type */ 269 (void) buffer_get_int(&buffer); /* reserved */ 270 271 /* Read the public key from the buffer. */ 272 buffer_get_int(&buffer); 273 pub = key_new(KEY_RSA1); 274 buffer_get_bignum(&buffer, pub->rsa->n); 275 buffer_get_bignum(&buffer, pub->rsa->e); 276 if (commentp) 277 *commentp = buffer_get_string(&buffer, NULL); 278 /* The encrypted private part is not parsed by this function. */ 279 280 buffer_free(&buffer); 281 return pub; 282 } 283 284 /* load public key from private-key file, works only for SSH v1 */ 285 Key * 286 key_load_public_type(int type, const char *filename, char **commentp) 287 { 288 Key *pub; 289 int fd; 290 291 if (type == KEY_RSA1) { 292 fd = open(filename, O_RDONLY); 293 if (fd < 0) 294 return NULL; 295 pub = key_load_public_rsa1(fd, filename, commentp); 296 close(fd); 297 return pub; 298 } 299 return NULL; 300 } 301 302 /* 303 * Loads the private key from the file. Returns 0 if an error is encountered 304 * (file does not exist or is not readable, or passphrase is bad). This 305 * initializes the private key. 306 * Assumes we are called under uid of the owner of the file. 307 */ 308 309 static Key * 310 key_load_private_rsa1(int fd, const char *filename, const char *passphrase, 311 char **commentp) 312 { 313 int i, check1, check2, cipher_type; 314 off_t len; 315 Buffer buffer, decrypted; 316 char *cp; 317 CipherContext ciphercontext; 318 Cipher *cipher; 319 BN_CTX *ctx; 320 BIGNUM *aux; 321 Key *prv = NULL; 322 323 len = lseek(fd, (off_t) 0, SEEK_END); 324 lseek(fd, (off_t) 0, SEEK_SET); 325 326 buffer_init(&buffer); 327 buffer_append_space(&buffer, &cp, len); 328 329 if (read(fd, cp, (size_t) len) != (size_t) len) { 330 debug("Read from key file %.200s failed: %.100s", filename, 331 strerror(errno)); 332 buffer_free(&buffer); 333 close(fd); 334 return NULL; 335 } 336 337 /* Check that it is at least big enough to contain the ID string. */ 338 if (len < sizeof(authfile_id_string)) { 339 debug3("No RSA1 key file %.200s.", filename); 340 buffer_free(&buffer); 341 close(fd); 342 return NULL; 343 } 344 /* 345 * Make sure it begins with the id string. Consume the id string 346 * from the buffer. 347 */ 348 for (i = 0; i < sizeof(authfile_id_string); i++) 349 if (buffer_get_char(&buffer) != authfile_id_string[i]) { 350 debug3("No RSA1 key file %.200s.", filename); 351 buffer_free(&buffer); 352 close(fd); 353 return NULL; 354 } 355 356 /* Read cipher type. */ 357 cipher_type = buffer_get_char(&buffer); 358 (void) buffer_get_int(&buffer); /* Reserved data. */ 359 360 /* Read the public key from the buffer. */ 361 buffer_get_int(&buffer); 362 prv = key_new_private(KEY_RSA1); 363 364 buffer_get_bignum(&buffer, prv->rsa->n); 365 buffer_get_bignum(&buffer, prv->rsa->e); 366 if (commentp) 367 *commentp = buffer_get_string(&buffer, NULL); 368 else 369 xfree(buffer_get_string(&buffer, NULL)); 370 371 /* Check that it is a supported cipher. */ 372 cipher = cipher_by_number(cipher_type); 373 if (cipher == NULL) { 374 debug("Unsupported cipher %d used in key file %.200s.", 375 cipher_type, filename); 376 buffer_free(&buffer); 377 goto fail; 378 } 379 /* Initialize space for decrypted data. */ 380 buffer_init(&decrypted); 381 buffer_append_space(&decrypted, &cp, buffer_len(&buffer)); 382 383 /* Rest of the buffer is encrypted. Decrypt it using the passphrase. */ 384 cipher_set_key_string(&ciphercontext, cipher, passphrase); 385 cipher_decrypt(&ciphercontext, (u_char *) cp, 386 (u_char *) buffer_ptr(&buffer), buffer_len(&buffer)); 387 memset(&ciphercontext, 0, sizeof(ciphercontext)); 388 buffer_free(&buffer); 389 390 check1 = buffer_get_char(&decrypted); 391 check2 = buffer_get_char(&decrypted); 392 if (check1 != buffer_get_char(&decrypted) || 393 check2 != buffer_get_char(&decrypted)) { 394 if (strcmp(passphrase, "") != 0) 395 debug("Bad passphrase supplied for key file %.200s.", 396 filename); 397 /* Bad passphrase. */ 398 buffer_free(&decrypted); 399 goto fail; 400 } 401 /* Read the rest of the private key. */ 402 buffer_get_bignum(&decrypted, prv->rsa->d); 403 buffer_get_bignum(&decrypted, prv->rsa->iqmp); /* u */ 404 /* in SSL and SSH v1 p and q are exchanged */ 405 buffer_get_bignum(&decrypted, prv->rsa->q); /* p */ 406 buffer_get_bignum(&decrypted, prv->rsa->p); /* q */ 407 408 /* calculate p-1 and q-1 */ 409 ctx = BN_CTX_new(); 410 aux = BN_new(); 411 412 BN_sub(aux, prv->rsa->q, BN_value_one()); 413 BN_mod(prv->rsa->dmq1, prv->rsa->d, aux, ctx); 414 415 BN_sub(aux, prv->rsa->p, BN_value_one()); 416 BN_mod(prv->rsa->dmp1, prv->rsa->d, aux, ctx); 417 418 BN_clear_free(aux); 419 BN_CTX_free(ctx); 420 421 buffer_free(&decrypted); 422 close(fd); 423 return prv; 424 425 fail: 426 if (commentp) 427 xfree(*commentp); 428 close(fd); 429 key_free(prv); 430 return NULL; 431 } 432 433 static Key * 434 key_load_private_pem(int fd, int type, const char *passphrase, 435 char **commentp) 436 { 437 FILE *fp; 438 EVP_PKEY *pk = NULL; 439 Key *prv = NULL; 440 char *name = "<no key>"; 441 442 fp = fdopen(fd, "r"); 443 if (fp == NULL) { 444 error("fdopen failed: %s", strerror(errno)); 445 close(fd); 446 return NULL; 447 } 448 pk = PEM_read_PrivateKey(fp, NULL, NULL, (char *)passphrase); 449 if (pk == NULL) { 450 debug("PEM_read_PrivateKey failed"); 451 (void)ERR_get_error(); 452 } else if (pk->type == EVP_PKEY_RSA && 453 (type == KEY_UNSPEC||type==KEY_RSA)) { 454 prv = key_new(KEY_UNSPEC); 455 prv->rsa = EVP_PKEY_get1_RSA(pk); 456 prv->type = KEY_RSA; 457 name = "rsa w/o comment"; 458 #ifdef DEBUG_PK 459 RSA_print_fp(stderr, prv->rsa, 8); 460 #endif 461 } else if (pk->type == EVP_PKEY_DSA && 462 (type == KEY_UNSPEC||type==KEY_DSA)) { 463 prv = key_new(KEY_UNSPEC); 464 prv->dsa = EVP_PKEY_get1_DSA(pk); 465 prv->type = KEY_DSA; 466 name = "dsa w/o comment"; 467 #ifdef DEBUG_PK 468 DSA_print_fp(stderr, prv->dsa, 8); 469 #endif 470 } else { 471 error("PEM_read_PrivateKey: mismatch or " 472 "unknown EVP_PKEY save_type %d", pk->save_type); 473 } 474 fclose(fp); 475 if (pk != NULL) 476 EVP_PKEY_free(pk); 477 if (prv != NULL && commentp) 478 *commentp = xstrdup(name); 479 debug("read PEM private key done: type %s", 480 prv ? key_type(prv) : "<unknown>"); 481 return prv; 482 } 483 484 static int 485 key_perm_ok(int fd, const char *filename) 486 { 487 struct stat st; 488 489 /* check owner and modes */ 490 if (fstat(fd, &st) < 0 || 491 (st.st_uid != 0 && getuid() != 0 && st.st_uid != getuid()) || 492 (st.st_mode & 077) != 0) { 493 close(fd); 494 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 495 error("@ WARNING: UNPROTECTED PRIVATE KEY FILE! @"); 496 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 497 error("Bad ownership or mode(0%3.3o) for '%s'.", 498 st.st_mode & 0777, filename); 499 error("It is recommended that your private key files are NOT accessible by others."); 500 error("This private key will be ignored."); 501 return 0; 502 } 503 return 1; 504 } 505 506 Key * 507 key_load_private_type(int type, const char *filename, const char *passphrase, 508 char **commentp) 509 { 510 int fd; 511 512 fd = open(filename, O_RDONLY); 513 if (fd < 0) 514 return NULL; 515 if (!key_perm_ok(fd, filename)) { 516 error("bad permissions: ignore key: %s", filename); 517 close(fd); 518 return NULL; 519 } 520 switch (type) { 521 case KEY_RSA1: 522 return key_load_private_rsa1(fd, filename, passphrase, 523 commentp); 524 /* closes fd */ 525 break; 526 case KEY_DSA: 527 case KEY_RSA: 528 case KEY_UNSPEC: 529 return key_load_private_pem(fd, type, passphrase, commentp); 530 /* closes fd */ 531 break; 532 default: 533 close(fd); 534 break; 535 } 536 return NULL; 537 } 538 539 Key * 540 key_load_private(const char *filename, const char *passphrase, 541 char **commentp) 542 { 543 Key *pub, *prv; 544 int fd; 545 546 fd = open(filename, O_RDONLY); 547 if (fd < 0) 548 return NULL; 549 if (!key_perm_ok(fd, filename)) { 550 error("bad permissions: ignore key: %s", filename); 551 close(fd); 552 return NULL; 553 } 554 pub = key_load_public_rsa1(fd, filename, commentp); 555 lseek(fd, (off_t) 0, SEEK_SET); /* rewind */ 556 if (pub == NULL) { 557 /* closes fd */ 558 prv = key_load_private_pem(fd, KEY_UNSPEC, passphrase, NULL); 559 /* use the filename as a comment for PEM */ 560 if (commentp && prv) 561 *commentp = xstrdup(filename); 562 } else { 563 /* it's a SSH v1 key if the public key part is readable */ 564 key_free(pub); 565 /* closes fd */ 566 prv = key_load_private_rsa1(fd, filename, passphrase, NULL); 567 } 568 return prv; 569 } 570 571 static int 572 key_try_load_public(Key *k, const char *filename, char **commentp) 573 { 574 FILE *f; 575 char line[4096]; 576 char *cp; 577 578 f = fopen(filename, "r"); 579 if (f != NULL) { 580 while (fgets(line, sizeof(line), f)) { 581 line[sizeof(line)-1] = '\0'; 582 cp = line; 583 switch(*cp){ 584 case '#': 585 case '\n': 586 case '\0': 587 continue; 588 } 589 /* Skip leading whitespace. */ 590 for (; *cp && (*cp == ' ' || *cp == '\t'); cp++) 591 ; 592 if (*cp) { 593 if (key_read(k, &cp) == 1) { 594 if (commentp) 595 *commentp=xstrdup(filename); 596 fclose(f); 597 return 1; 598 } 599 } 600 } 601 fclose(f); 602 } 603 return 0; 604 } 605 606 /* load public key from ssh v1 private or any pubkey file */ 607 Key * 608 key_load_public(const char *filename, char **commentp) 609 { 610 Key *pub; 611 char file[MAXPATHLEN]; 612 613 pub = key_load_public_type(KEY_RSA1, filename, commentp); 614 if (pub != NULL) 615 return pub; 616 pub = key_new(KEY_UNSPEC); 617 if (key_try_load_public(pub, filename, commentp) == 1) 618 return pub; 619 if ((strlcpy(file, filename, sizeof file) < sizeof(file)) && 620 (strlcat(file, ".pub", sizeof file) < sizeof(file)) && 621 (key_try_load_public(pub, file, commentp) == 1)) 622 return pub; 623 key_free(pub); 624 return NULL; 625 } 626