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 1.32 2001/04/18 23:44:51 markus Exp $"); 40 RCSID("$FreeBSD$"); 41 42 #include <openssl/err.h> 43 #include <openssl/evp.h> 44 #include <openssl/pem.h> 45 46 #include "cipher.h" 47 #include "xmalloc.h" 48 #include "buffer.h" 49 #include "bufaux.h" 50 #include "key.h" 51 #include "ssh.h" 52 #include "log.h" 53 #include "authfile.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 int 67 key_save_private_rsa1(Key *key, const char *filename, const char *passphrase, 68 const char *comment) 69 { 70 Buffer buffer, encrypted; 71 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_string(&encrypted, comment, strlen(comment)); 130 131 /* Allocate space for the private part of the key in the buffer. */ 132 buffer_append_space(&encrypted, &cp, buffer_len(&buffer)); 133 134 cipher_set_key_string(&ciphercontext, cipher, passphrase); 135 cipher_encrypt(&ciphercontext, (u_char *) cp, 136 (u_char *) 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 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 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 buffer_append_space(&buffer, &cp, 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("No 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("No 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 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 char *cp; 318 CipherContext ciphercontext; 319 Cipher *cipher; 320 BN_CTX *ctx; 321 BIGNUM *aux; 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 buffer_append_space(&buffer, &cp, 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("No 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("No 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 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 buffer_append_space(&decrypted, &cp, 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(&ciphercontext, (u_char *) cp, 387 (u_char *) buffer_ptr(&buffer), buffer_len(&buffer)); 388 memset(&ciphercontext, 0, sizeof(ciphercontext)); 389 buffer_free(&buffer); 390 391 check1 = buffer_get_char(&decrypted); 392 check2 = buffer_get_char(&decrypted); 393 if (check1 != buffer_get_char(&decrypted) || 394 check2 != buffer_get_char(&decrypted)) { 395 if (strcmp(passphrase, "") != 0) 396 debug("Bad passphrase supplied for key file %.200s.", 397 filename); 398 /* Bad passphrase. */ 399 buffer_free(&decrypted); 400 goto fail; 401 } 402 /* Read the rest of the private key. */ 403 buffer_get_bignum(&decrypted, prv->rsa->d); 404 buffer_get_bignum(&decrypted, prv->rsa->iqmp); /* u */ 405 /* in SSL and SSH v1 p and q are exchanged */ 406 buffer_get_bignum(&decrypted, prv->rsa->q); /* p */ 407 buffer_get_bignum(&decrypted, prv->rsa->p); /* q */ 408 409 /* calculate p-1 and q-1 */ 410 ctx = BN_CTX_new(); 411 aux = BN_new(); 412 413 BN_sub(aux, prv->rsa->q, BN_value_one()); 414 BN_mod(prv->rsa->dmq1, prv->rsa->d, aux, ctx); 415 416 BN_sub(aux, prv->rsa->p, BN_value_one()); 417 BN_mod(prv->rsa->dmp1, prv->rsa->d, aux, ctx); 418 419 BN_clear_free(aux); 420 BN_CTX_free(ctx); 421 422 buffer_free(&decrypted); 423 close(fd); 424 return prv; 425 426 fail: 427 if (commentp) 428 xfree(*commentp); 429 close(fd); 430 key_free(prv); 431 return NULL; 432 } 433 434 Key * 435 key_load_private_pem(int fd, int type, const char *passphrase, 436 char **commentp) 437 { 438 FILE *fp; 439 EVP_PKEY *pk = NULL; 440 Key *prv = NULL; 441 char *name = "<no key>"; 442 443 fp = fdopen(fd, "r"); 444 if (fp == NULL) { 445 error("fdopen failed: %s", strerror(errno)); 446 close(fd); 447 return NULL; 448 } 449 pk = PEM_read_PrivateKey(fp, NULL, NULL, (char *)passphrase); 450 if (pk == NULL) { 451 debug("PEM_read_PrivateKey failed"); 452 (void)ERR_get_error(); 453 } else if (pk->type == EVP_PKEY_RSA && 454 (type == KEY_UNSPEC||type==KEY_RSA)) { 455 prv = key_new(KEY_UNSPEC); 456 prv->rsa = EVP_PKEY_get1_RSA(pk); 457 prv->type = KEY_RSA; 458 name = "rsa w/o comment"; 459 #ifdef DEBUG_PK 460 RSA_print_fp(stderr, prv->rsa, 8); 461 #endif 462 } else if (pk->type == EVP_PKEY_DSA && 463 (type == KEY_UNSPEC||type==KEY_DSA)) { 464 prv = key_new(KEY_UNSPEC); 465 prv->dsa = EVP_PKEY_get1_DSA(pk); 466 prv->type = KEY_DSA; 467 name = "dsa w/o comment"; 468 #ifdef DEBUG_PK 469 DSA_print_fp(stderr, prv->dsa, 8); 470 #endif 471 } else { 472 error("PEM_read_PrivateKey: mismatch or " 473 "unknown EVP_PKEY save_type %d", pk->save_type); 474 } 475 fclose(fp); 476 if (pk != NULL) 477 EVP_PKEY_free(pk); 478 if (prv != NULL && commentp) 479 *commentp = xstrdup(name); 480 debug("read PEM private key done: type %s", 481 prv ? key_type(prv) : "<unknown>"); 482 return prv; 483 } 484 485 int 486 key_perm_ok(int fd, const char *filename) 487 { 488 struct stat st; 489 490 /* check owner and modes */ 491 if (fstat(fd, &st) < 0 || 492 (st.st_uid != 0 && getuid() != 0 && st.st_uid != getuid()) || 493 (st.st_mode & 077) != 0) { 494 close(fd); 495 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 496 error("@ WARNING: UNPROTECTED PRIVATE KEY FILE! @"); 497 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@"); 498 error("Bad ownership or mode(0%3.3o) for '%s'.", 499 st.st_mode & 0777, filename); 500 error("It is recommended that your private key files are NOT accessible by others."); 501 error("This private key will be ignored."); 502 return 0; 503 } 504 return 1; 505 } 506 507 Key * 508 key_load_private_type(int type, const char *filename, const char *passphrase, 509 char **commentp) 510 { 511 int fd; 512 513 fd = open(filename, O_RDONLY); 514 if (fd < 0) 515 return NULL; 516 if (!key_perm_ok(fd, filename)) { 517 error("bad permissions: ignore key: %s", filename); 518 close(fd); 519 return NULL; 520 } 521 switch (type) { 522 case KEY_RSA1: 523 return key_load_private_rsa1(fd, filename, passphrase, 524 commentp); 525 /* closes fd */ 526 break; 527 case KEY_DSA: 528 case KEY_RSA: 529 case KEY_UNSPEC: 530 return key_load_private_pem(fd, type, passphrase, commentp); 531 /* closes fd */ 532 break; 533 default: 534 close(fd); 535 break; 536 } 537 return NULL; 538 } 539 540 Key * 541 key_load_private(const char *filename, const char *passphrase, 542 char **commentp) 543 { 544 Key *pub; 545 int fd; 546 547 fd = open(filename, O_RDONLY); 548 if (fd < 0) 549 return NULL; 550 if (!key_perm_ok(fd, filename)) { 551 error("bad permissions: ignore key: %s", filename); 552 close(fd); 553 return NULL; 554 } 555 pub = key_load_public_rsa1(fd, filename, commentp); 556 lseek(fd, (off_t) 0, SEEK_SET); /* rewind */ 557 if (pub == NULL) { 558 /* closes fd */ 559 return key_load_private_pem(fd, KEY_UNSPEC, passphrase, commentp); 560 } else { 561 /* it's a SSH v1 key if the public key part is readable */ 562 key_free(pub); 563 /* closes fd */ 564 return key_load_private_rsa1(fd, filename, passphrase, NULL); 565 } 566 } 567 568 int 569 key_try_load_public(Key *k, const char *filename, char **commentp) 570 { 571 FILE *f; 572 char line[4096]; 573 char *cp; 574 575 f = fopen(filename, "r"); 576 if (f != NULL) { 577 while (fgets(line, sizeof(line), f)) { 578 line[sizeof(line)-1] = '\0'; 579 cp = line; 580 switch(*cp){ 581 case '#': 582 case '\n': 583 case '\0': 584 continue; 585 } 586 /* Skip leading whitespace. */ 587 for (; *cp && (*cp == ' ' || *cp == '\t'); cp++) 588 ; 589 if (*cp) { 590 if (key_read(k, &cp) == 1) { 591 if (commentp) 592 *commentp=xstrdup(filename); 593 fclose(f); 594 return 1; 595 } 596 } 597 } 598 fclose(f); 599 } 600 return 0; 601 } 602 603 /* load public key from ssh v1 private or any pubkey file */ 604 Key * 605 key_load_public(const char *filename, char **commentp) 606 { 607 Key *pub; 608 char file[MAXPATHLEN]; 609 610 pub = key_load_public_type(KEY_RSA1, filename, commentp); 611 if (pub != NULL) 612 return pub; 613 pub = key_new(KEY_UNSPEC); 614 if (key_try_load_public(pub, filename, commentp) == 1) 615 return pub; 616 if ((strlcpy(file, filename, sizeof file) < sizeof(file)) && 617 (strlcat(file, ".pub", sizeof file) < sizeof(file)) && 618 (key_try_load_public(pub, file, commentp) == 1)) 619 return pub; 620 key_free(pub); 621 return NULL; 622 } 623