crypto/openssh/authfile.c

   1 /* $OpenBSD: authfile.c,v 1.127 2017/07/01 13:50:45 djm Exp $ */
   2 /*
   3  * Copyright (c) 2000, 2013 Markus Friedl.  All rights reserved.
   4  *
   5  * Redistribution and use in source and binary forms, with or without
   6  * modification, are permitted provided that the following conditions
   7  * are met:
   8  * 1. Redistributions of source code must retain the above copyright
   9  *    notice, this list of conditions and the following disclaimer.
  10  * 2. Redistributions in binary form must reproduce the above copyright
  11  *    notice, this list of conditions and the following disclaimer in the
  12  *    documentation and/or other materials provided with the distribution.
  13  *
  14  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  15  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  16  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  17  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  18  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  19  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  20  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  21  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  22  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  23  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  24  */
  25
  26 #include "includes.h"
  27
  28 #include <sys/types.h>
  29 #include <sys/stat.h>
  30 #include <sys/uio.h>
  31
  32 #include <errno.h>
  33 #include <fcntl.h>
  34 #include <stdio.h>
  35 #include <stdarg.h>
  36 #include <stdlib.h>
  37 #include <string.h>
  38 #include <unistd.h>
  39 #include <limits.h>
  40
  41 #include "cipher.h"
  42 #include "ssh.h"
  43 #include "log.h"
  44 #include "authfile.h"
  45 #include "misc.h"
  46 #include "atomicio.h"
  47 #include "sshkey.h"
  48 #include "sshbuf.h"
  49 #include "ssherr.h"
  50 #include "krl.h"
  51
  52 #define MAX_KEY_FILE_SIZE       (1024 * 1024)
  53
  54 /* Save a key blob to a file */
  55 static int
  56 sshkey_save_private_blob(struct sshbuf *keybuf, const char *filename)
  57 {
  58         int fd, oerrno;
  59
  60         if ((fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600)) < 0)
  61                 return SSH_ERR_SYSTEM_ERROR;
  62         if (atomicio(vwrite, fd, (u_char *)sshbuf_ptr(keybuf),
  63             sshbuf_len(keybuf)) != sshbuf_len(keybuf)) {
  64                 oerrno = errno;
  65                 close(fd);
  66                 unlink(filename);
  67                 errno = oerrno;
  68                 return SSH_ERR_SYSTEM_ERROR;
  69         }
  70         close(fd);
  71         return 0;
  72 }
  73
  74 int
  75 sshkey_save_private(struct sshkey *key, const char *filename,
  76     const char *passphrase, const char *comment,
  77     int force_new_format, const char *new_format_cipher, int new_format_rounds)
  78 {
  79         struct sshbuf *keyblob = NULL;
  80         int r;
  81
  82         if ((keyblob = sshbuf_new()) == NULL)
  83                 return SSH_ERR_ALLOC_FAIL;
  84         if ((r = sshkey_private_to_fileblob(key, keyblob, passphrase, comment,
  85             force_new_format, new_format_cipher, new_format_rounds)) != 0)
  86                 goto out;
  87         if ((r = sshkey_save_private_blob(keyblob, filename)) != 0)
  88                 goto out;
  89         r = 0;
  90  out:
  91         sshbuf_free(keyblob);
  92         return r;
  93 }
  94
  95 /* Load a key from a fd into a buffer */
  96 int
  97 sshkey_load_file(int fd, struct sshbuf *blob)
  98 {
  99         u_char buf[1024];
 100         size_t len;
 101         struct stat st;
 102         int r;
 103
 104         if (fstat(fd, &st) < 0)
 105                 return SSH_ERR_SYSTEM_ERROR;
 106         if ((st.st_mode & (S_IFSOCK|S_IFCHR|S_IFIFO)) == 0 &&
 107             st.st_size > MAX_KEY_FILE_SIZE)
 108                 return SSH_ERR_INVALID_FORMAT;
 109         for (;;) {
 110                 if ((len = atomicio(read, fd, buf, sizeof(buf))) == 0) {
 111                         if (errno == EPIPE)
 112                                 break;
 113                         r = SSH_ERR_SYSTEM_ERROR;
 114                         goto out;
 115                 }
 116                 if ((r = sshbuf_put(blob, buf, len)) != 0)
 117                         goto out;
 118                 if (sshbuf_len(blob) > MAX_KEY_FILE_SIZE) {
 119                         r = SSH_ERR_INVALID_FORMAT;
 120                         goto out;
 121                 }
 122         }
 123         if ((st.st_mode & (S_IFSOCK|S_IFCHR|S_IFIFO)) == 0 &&
 124             st.st_size != (off_t)sshbuf_len(blob)) {
 125                 r = SSH_ERR_FILE_CHANGED;
 126                 goto out;
 127         }
 128         r = 0;
 129
 130  out:
 131         explicit_bzero(buf, sizeof(buf));
 132         if (r != 0)
 133                 sshbuf_reset(blob);
 134         return r;
 135 }
 136
 137
 138 /* XXX remove error() calls from here? */
 139 int
 140 sshkey_perm_ok(int fd, const char *filename)
 141 {
 142         struct stat st;
 143
 144         if (fstat(fd, &st) < 0)
 145                 return SSH_ERR_SYSTEM_ERROR;
 146         /*
 147          * if a key owned by the user is accessed, then we check the
 148          * permissions of the file. if the key owned by a different user,
 149          * then we don't care.
 150          */
 151 #ifdef HAVE_CYGWIN
 152         if (check_ntsec(filename))
 153 #endif
 154         if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0) {
 155                 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
 156                 error("@         WARNING: UNPROTECTED PRIVATE KEY FILE!          @");
 157                 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
 158                 error("Permissions 0%3.3o for '%s' are too open.",
 159                     (u_int)st.st_mode & 0777, filename);
 160                 error("It is required that your private key files are NOT accessible by others.");
 161                 error("This private key will be ignored.");
 162                 return SSH_ERR_KEY_BAD_PERMISSIONS;
 163         }
 164         return 0;
 165 }
 166
 167 /* XXX kill perm_ok now that we have SSH_ERR_KEY_BAD_PERMISSIONS? */
 168 int
 169 sshkey_load_private_type(int type, const char *filename, const char *passphrase,
 170     struct sshkey **keyp, char **commentp, int *perm_ok)
 171 {
 172         int fd, r;
 173
 174         if (keyp != NULL)
 175                 *keyp = NULL;
 176         if (commentp != NULL)
 177                 *commentp = NULL;
 178
 179         if ((fd = open(filename, O_RDONLY)) < 0) {
 180                 if (perm_ok != NULL)
 181                         *perm_ok = 0;
 182                 return SSH_ERR_SYSTEM_ERROR;
 183         }
 184         if (sshkey_perm_ok(fd, filename) != 0) {
 185                 if (perm_ok != NULL)
 186                         *perm_ok = 0;
 187                 r = SSH_ERR_KEY_BAD_PERMISSIONS;
 188                 goto out;
 189         }
 190         if (perm_ok != NULL)
 191                 *perm_ok = 1;
 192
 193         r = sshkey_load_private_type_fd(fd, type, passphrase, keyp, commentp);
 194  out:
 195         close(fd);
 196         return r;
 197 }
 198
 199 int
 200 sshkey_load_private_type_fd(int fd, int type, const char *passphrase,
 201     struct sshkey **keyp, char **commentp)
 202 {
 203         struct sshbuf *buffer = NULL;
 204         int r;
 205
 206         if (keyp != NULL)
 207                 *keyp = NULL;
 208         if ((buffer = sshbuf_new()) == NULL) {
 209                 r = SSH_ERR_ALLOC_FAIL;
 210                 goto out;
 211         }
 212         if ((r = sshkey_load_file(fd, buffer)) != 0 ||
 213             (r = sshkey_parse_private_fileblob_type(buffer, type,
 214             passphrase, keyp, commentp)) != 0)
 215                 goto out;
 216
 217         /* success */
 218         r = 0;
 219  out:
 220         sshbuf_free(buffer);
 221         return r;
 222 }
 223
 224 /* XXX this is almost identical to sshkey_load_private_type() */
 225 int
 226 sshkey_load_private(const char *filename, const char *passphrase,
 227     struct sshkey **keyp, char **commentp)
 228 {
 229         struct sshbuf *buffer = NULL;
 230         int r, fd;
 231
 232         if (keyp != NULL)
 233                 *keyp = NULL;
 234         if (commentp != NULL)
 235                 *commentp = NULL;
 236
 237         if ((fd = open(filename, O_RDONLY)) < 0)
 238                 return SSH_ERR_SYSTEM_ERROR;
 239         if (sshkey_perm_ok(fd, filename) != 0) {
 240                 r = SSH_ERR_KEY_BAD_PERMISSIONS;
 241                 goto out;
 242         }
 243
 244         if ((buffer = sshbuf_new()) == NULL) {
 245                 r = SSH_ERR_ALLOC_FAIL;
 246                 goto out;
 247         }
 248         if ((r = sshkey_load_file(fd, buffer)) != 0 ||
 249             (r = sshkey_parse_private_fileblob(buffer, passphrase, keyp,
 250             commentp)) != 0)
 251                 goto out;
 252         r = 0;
 253  out:
 254         close(fd);
 255         sshbuf_free(buffer);
 256         return r;
 257 }
 258
 259 static int
 260 sshkey_try_load_public(struct sshkey *k, const char *filename, char **commentp)
 261 {
 262         FILE *f;
 263         char line[SSH_MAX_PUBKEY_BYTES];
 264         char *cp;
 265         u_long linenum = 0;
 266         int r;
 267
 268         if (commentp != NULL)
 269                 *commentp = NULL;
 270         if ((f = fopen(filename, "r")) == NULL)
 271                 return SSH_ERR_SYSTEM_ERROR;
 272         while (read_keyfile_line(f, filename, line, sizeof(line),
 273                     &linenum) != -1) {
 274                 cp = line;
 275                 switch (*cp) {
 276                 case '#':
 277                 case '\n':
 278                 case '\0':
 279                         continue;
 280                 }
 281                 /* Abort loading if this looks like a private key */
 282                 if (strncmp(cp, "-----BEGIN", 10) == 0 ||
 283                     strcmp(cp, "SSH PRIVATE KEY FILE") == 0)
 284                         break;
 285                 /* Skip leading whitespace. */
 286                 for (; *cp && (*cp == ' ' || *cp == '\t'); cp++)
 287                         ;
 288                 if (*cp) {
 289                         if ((r = sshkey_read(k, &cp)) == 0) {
 290                                 cp[strcspn(cp, "\r\n")] = '\0';
 291                                 if (commentp) {
 292                                         *commentp = strdup(*cp ?
 293                                             cp : filename);
 294                                         if (*commentp == NULL)
 295                                                 r = SSH_ERR_ALLOC_FAIL;
 296                                 }
 297                                 fclose(f);
 298                                 return r;
 299                         }
 300                 }
 301         }
 302         fclose(f);
 303         return SSH_ERR_INVALID_FORMAT;
 304 }
 305
 306 /* load public key from any pubkey file */
 307 int
 308 sshkey_load_public(const char *filename, struct sshkey **keyp, char **commentp)
 309 {
 310         struct sshkey *pub = NULL;
 311         char *file = NULL;
 312         int r;
 313
 314         if (keyp != NULL)
 315                 *keyp = NULL;
 316         if (commentp != NULL)
 317                 *commentp = NULL;
 318
 319         if ((pub = sshkey_new(KEY_UNSPEC)) == NULL)
 320                 return SSH_ERR_ALLOC_FAIL;
 321         if ((r = sshkey_try_load_public(pub, filename, commentp)) == 0) {
 322                 if (keyp != NULL) {
 323                         *keyp = pub;
 324                         pub = NULL;
 325                 }
 326                 r = 0;
 327                 goto out;
 328         }
 329         sshkey_free(pub);
 330
 331         /* try .pub suffix */
 332         if (asprintf(&file, "%s.pub", filename) == -1)
 333                 return SSH_ERR_ALLOC_FAIL;
 334         if ((pub = sshkey_new(KEY_UNSPEC)) == NULL) {
 335                 r = SSH_ERR_ALLOC_FAIL;
 336                 goto out;
 337         }
 338         if ((r = sshkey_try_load_public(pub, file, commentp)) == 0) {
 339                 if (keyp != NULL) {
 340                         *keyp = pub;
 341                         pub = NULL;
 342                 }
 343                 r = 0;
 344         }
 345  out:
 346         free(file);
 347         sshkey_free(pub);
 348         return r;
 349 }
 350
 351 /* Load the certificate associated with the named private key */
 352 int
 353 sshkey_load_cert(const char *filename, struct sshkey **keyp)
 354 {
 355         struct sshkey *pub = NULL;
 356         char *file = NULL;
 357         int r = SSH_ERR_INTERNAL_ERROR;
 358
 359         if (keyp != NULL)
 360                 *keyp = NULL;
 361
 362         if (asprintf(&file, "%s-cert.pub", filename) == -1)
 363                 return SSH_ERR_ALLOC_FAIL;
 364
 365         if ((pub = sshkey_new(KEY_UNSPEC)) == NULL) {
 366                 goto out;
 367         }
 368         if ((r = sshkey_try_load_public(pub, file, NULL)) != 0)
 369                 goto out;
 370         /* success */
 371         if (keyp != NULL) {
 372                 *keyp = pub;
 373                 pub = NULL;
 374         }
 375         r = 0;
 376  out:
 377         free(file);
 378         sshkey_free(pub);
 379         return r;
 380 }
 381
 382 /* Load private key and certificate */
 383 int
 384 sshkey_load_private_cert(int type, const char *filename, const char *passphrase,
 385     struct sshkey **keyp, int *perm_ok)
 386 {
 387         struct sshkey *key = NULL, *cert = NULL;
 388         int r;
 389
 390         if (keyp != NULL)
 391                 *keyp = NULL;
 392
 393         switch (type) {
 394 #ifdef WITH_OPENSSL
 395         case KEY_RSA:
 396         case KEY_DSA:
 397         case KEY_ECDSA:
 398 #endif /* WITH_OPENSSL */
 399         case KEY_ED25519:
 400         case KEY_UNSPEC:
 401                 break;
 402         default:
 403                 return SSH_ERR_KEY_TYPE_UNKNOWN;
 404         }
 405
 406         if ((r = sshkey_load_private_type(type, filename,
 407             passphrase, &key, NULL, perm_ok)) != 0 ||
 408             (r = sshkey_load_cert(filename, &cert)) != 0)
 409                 goto out;
 410
 411         /* Make sure the private key matches the certificate */
 412         if (sshkey_equal_public(key, cert) == 0) {
 413                 r = SSH_ERR_KEY_CERT_MISMATCH;
 414                 goto out;
 415         }
 416
 417         if ((r = sshkey_to_certified(key)) != 0 ||
 418             (r = sshkey_cert_copy(cert, key)) != 0)
 419                 goto out;
 420         r = 0;
 421         if (keyp != NULL) {
 422                 *keyp = key;
 423                 key = NULL;
 424         }
 425  out:
 426         sshkey_free(key);
 427         sshkey_free(cert);
 428         return r;
 429 }
 430
 431 /*
 432  * Returns success if the specified "key" is listed in the file "filename",
 433  * SSH_ERR_KEY_NOT_FOUND: if the key is not listed or another error.
 434  * If "strict_type" is set then the key type must match exactly,
 435  * otherwise a comparison that ignores certficiate data is performed.
 436  * If "check_ca" is set and "key" is a certificate, then its CA key is
 437  * also checked and sshkey_in_file() will return success if either is found.
 438  */
 439 int
 440 sshkey_in_file(struct sshkey *key, const char *filename, int strict_type,
 441     int check_ca)
 442 {
 443         FILE *f;
 444         char line[SSH_MAX_PUBKEY_BYTES];
 445         char *cp;
 446         u_long linenum = 0;
 447         int r = 0;
 448         struct sshkey *pub = NULL;
 449         int (*sshkey_compare)(const struct sshkey *, const struct sshkey *) =
 450             strict_type ?  sshkey_equal : sshkey_equal_public;
 451
 452         if ((f = fopen(filename, "r")) == NULL)
 453                 return SSH_ERR_SYSTEM_ERROR;
 454
 455         while (read_keyfile_line(f, filename, line, sizeof(line),
 456             &linenum) != -1) {
 457                 cp = line;
 458
 459                 /* Skip leading whitespace. */
 460                 for (; *cp && (*cp == ' ' || *cp == '\t'); cp++)
 461                         ;
 462
 463                 /* Skip comments and empty lines */
 464                 switch (*cp) {
 465                 case '#':
 466                 case '\n':
 467                 case '\0':
 468                         continue;
 469                 }
 470
 471                 if ((pub = sshkey_new(KEY_UNSPEC)) == NULL) {
 472                         r = SSH_ERR_ALLOC_FAIL;
 473                         goto out;
 474                 }
 475                 if ((r = sshkey_read(pub, &cp)) != 0)
 476                         goto out;
 477                 if (sshkey_compare(key, pub) ||
 478                     (check_ca && sshkey_is_cert(key) &&
 479                     sshkey_compare(key->cert->signature_key, pub))) {
 480                         r = 0;
 481                         goto out;
 482                 }
 483                 sshkey_free(pub);
 484                 pub = NULL;
 485         }
 486         r = SSH_ERR_KEY_NOT_FOUND;
 487  out:
 488         sshkey_free(pub);
 489         fclose(f);
 490         return r;
 491 }
 492
 493 /*
 494  * Checks whether the specified key is revoked, returning 0 if not,
 495  * SSH_ERR_KEY_REVOKED if it is or another error code if something
 496  * unexpected happened.
 497  * This will check both the key and, if it is a certificate, its CA key too.
 498  * "revoked_keys_file" may be a KRL or a one-per-line list of public keys.
 499  */
 500 int
 501 sshkey_check_revoked(struct sshkey *key, const char *revoked_keys_file)
 502 {
 503         int r;
 504
 505         r = ssh_krl_file_contains_key(revoked_keys_file, key);
 506         /* If this was not a KRL to begin with then continue below */
 507         if (r != SSH_ERR_KRL_BAD_MAGIC)
 508                 return r;
 509
 510         /*
 511          * If the file is not a KRL or we can't handle KRLs then attempt to
 512          * parse the file as a flat list of keys.
 513          */
 514         switch ((r = sshkey_in_file(key, revoked_keys_file, 0, 1))) {
 515         case 0:
 516                 /* Key found => revoked */
 517                 return SSH_ERR_KEY_REVOKED;
 518         case SSH_ERR_KEY_NOT_FOUND:
 519                 /* Key not found => not revoked */
 520                 return 0;
 521         default:
 522                 /* Some other error occurred */
 523                 return r;
 524         }
 525 }
 526