crypto/openssh/authfile.c

   1 /* $OpenBSD: authfile.c,v 1.76 2006/08/03 03:34:41 deraadt Exp $ */
   2 /*
   3  * Author: Tatu Ylonen <ylo@cs.hut.fi>
   4  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
   5  *                    All rights reserved
   6  * This file contains functions for reading and writing identity files, and
   7  * for reading the passphrase from the user.
   8  *
   9  * As far as I am concerned, the code I have written for this software
  10  * can be used freely for any purpose.  Any derived versions of this
  11  * software must be clearly marked as such, and if the derived work is
  12  * incompatible with the protocol description in the RFC file, it must be
  13  * called by a name other than "ssh" or "Secure Shell".
  14  *
  15  *
  16  * Copyright (c) 2000 Markus Friedl.  All rights reserved.
  17  *
  18  * Redistribution and use in source and binary forms, with or without
  19  * modification, are permitted provided that the following conditions
  20  * are met:
  21  * 1. Redistributions of source code must retain the above copyright
  22  *    notice, this list of conditions and the following disclaimer.
  23  * 2. Redistributions in binary form must reproduce the above copyright
  24  *    notice, this list of conditions and the following disclaimer in the
  25  *    documentation and/or other materials provided with the distribution.
  26  *
  27  * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
  28  * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  29  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
  30  * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
  31  * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
  32  * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
  33  * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
  34  * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  35  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
  36  * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  37  */
  38
  39 #include "includes.h"
  40
  41 #include <sys/types.h>
  42 #include <sys/stat.h>
  43 #include <sys/param.h>
  44 #include <sys/uio.h>
  45
  46 #include <openssl/err.h>
  47 #include <openssl/evp.h>
  48 #include <openssl/pem.h>
  49
  50 #include <errno.h>
  51 #include <fcntl.h>
  52 #include <stdarg.h>
  53 #include <stdio.h>
  54 #include <stdlib.h>
  55 #include <string.h>
  56 #include <unistd.h>
  57
  58 #include "xmalloc.h"
  59 #include "cipher.h"
  60 #include "buffer.h"
  61 #include "key.h"
  62 #include "ssh.h"
  63 #include "log.h"
  64 #include "authfile.h"
  65 #include "rsa.h"
  66 #include "misc.h"
  67 #include "atomicio.h"
  68 #include "pathnames.h"
  69
  70 /* Version identification string for SSH v1 identity files. */
  71 static const char authfile_id_string[] =
  72     "SSH PRIVATE KEY FILE FORMAT 1.1\n";
  73
  74 /*
  75  * Saves the authentication (private) key in a file, encrypting it with
  76  * passphrase.  The identification of the file (lowest 64 bits of n) will
  77  * precede the key to provide identification of the key without needing a
  78  * passphrase.
  79  */
  80
  81 static int
  82 key_save_private_rsa1(Key *key, const char *filename, const char *passphrase,
  83     const char *comment)
  84 {
  85         Buffer buffer, encrypted;
  86         u_char buf[100], *cp;
  87         int fd, i, cipher_num;
  88         CipherContext ciphercontext;
  89         Cipher *cipher;
  90         u_int32_t rnd;
  91
  92         /*
  93          * If the passphrase is empty, use SSH_CIPHER_NONE to ease converting
  94          * to another cipher; otherwise use SSH_AUTHFILE_CIPHER.
  95          */
  96         cipher_num = (strcmp(passphrase, "") == 0) ?
  97             SSH_CIPHER_NONE : SSH_AUTHFILE_CIPHER;
  98         if ((cipher = cipher_by_number(cipher_num)) == NULL)
  99                 fatal("save_private_key_rsa: bad cipher");
 100
 101         /* This buffer is used to built the secret part of the private key. */
 102         buffer_init(&buffer);
 103
 104         /* Put checkbytes for checking passphrase validity. */
 105         rnd = arc4random();
 106         buf[0] = rnd & 0xff;
 107         buf[1] = (rnd >> 8) & 0xff;
 108         buf[2] = buf[0];
 109         buf[3] = buf[1];
 110         buffer_append(&buffer, buf, 4);
 111
 112         /*
 113          * Store the private key (n and e will not be stored because they
 114          * will be stored in plain text, and storing them also in encrypted
 115          * format would just give known plaintext).
 116          */
 117         buffer_put_bignum(&buffer, key->rsa->d);
 118         buffer_put_bignum(&buffer, key->rsa->iqmp);
 119         buffer_put_bignum(&buffer, key->rsa->q);        /* reverse from SSL p */
 120         buffer_put_bignum(&buffer, key->rsa->p);        /* reverse from SSL q */
 121
 122         /* Pad the part to be encrypted until its size is a multiple of 8. */
 123         while (buffer_len(&buffer) % 8 != 0)
 124                 buffer_put_char(&buffer, 0);
 125
 126         /* This buffer will be used to contain the data in the file. */
 127         buffer_init(&encrypted);
 128
 129         /* First store keyfile id string. */
 130         for (i = 0; authfile_id_string[i]; i++)
 131                 buffer_put_char(&encrypted, authfile_id_string[i]);
 132         buffer_put_char(&encrypted, 0);
 133
 134         /* Store cipher type. */
 135         buffer_put_char(&encrypted, cipher_num);
 136         buffer_put_int(&encrypted, 0);  /* For future extension */
 137
 138         /* Store public key.  This will be in plain text. */
 139         buffer_put_int(&encrypted, BN_num_bits(key->rsa->n));
 140         buffer_put_bignum(&encrypted, key->rsa->n);
 141         buffer_put_bignum(&encrypted, key->rsa->e);
 142         buffer_put_cstring(&encrypted, comment);
 143
 144         /* Allocate space for the private part of the key in the buffer. */
 145         cp = buffer_append_space(&encrypted, buffer_len(&buffer));
 146
 147         cipher_set_key_string(&ciphercontext, cipher, passphrase,
 148             CIPHER_ENCRYPT);
 149         cipher_crypt(&ciphercontext, cp,
 150             buffer_ptr(&buffer), buffer_len(&buffer));
 151         cipher_cleanup(&ciphercontext);
 152         memset(&ciphercontext, 0, sizeof(ciphercontext));
 153
 154         /* Destroy temporary data. */
 155         memset(buf, 0, sizeof(buf));
 156         buffer_free(&buffer);
 157
 158         fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600);
 159         if (fd < 0) {
 160                 error("open %s failed: %s.", filename, strerror(errno));
 161                 buffer_free(&encrypted);
 162                 return 0;
 163         }
 164         if (atomicio(vwrite, fd, buffer_ptr(&encrypted),
 165             buffer_len(&encrypted)) != buffer_len(&encrypted)) {
 166                 error("write to key file %s failed: %s", filename,
 167                     strerror(errno));
 168                 buffer_free(&encrypted);
 169                 close(fd);
 170                 unlink(filename);
 171                 return 0;
 172         }
 173         close(fd);
 174         buffer_free(&encrypted);
 175         return 1;
 176 }
 177
 178 /* save SSH v2 key in OpenSSL PEM format */
 179 static int
 180 key_save_private_pem(Key *key, const char *filename, const char *_passphrase,
 181     const char *comment)
 182 {
 183         FILE *fp;
 184         int fd;
 185         int success = 0;
 186         int len = strlen(_passphrase);
 187         u_char *passphrase = (len > 0) ? (u_char *)_passphrase : NULL;
 188         const EVP_CIPHER *cipher = (len > 0) ? EVP_des_ede3_cbc() : NULL;
 189
 190         if (len > 0 && len <= 4) {
 191                 error("passphrase too short: have %d bytes, need > 4", len);
 192                 return 0;
 193         }
 194         fd = open(filename, O_WRONLY | O_CREAT | O_TRUNC, 0600);
 195         if (fd < 0) {
 196                 error("open %s failed: %s.", filename, strerror(errno));
 197                 return 0;
 198         }
 199         fp = fdopen(fd, "w");
 200         if (fp == NULL) {
 201                 error("fdopen %s failed: %s.", filename, strerror(errno));
 202                 close(fd);
 203                 return 0;
 204         }
 205         switch (key->type) {
 206         case KEY_DSA:
 207                 success = PEM_write_DSAPrivateKey(fp, key->dsa,
 208                     cipher, passphrase, len, NULL, NULL);
 209                 break;
 210         case KEY_RSA:
 211                 success = PEM_write_RSAPrivateKey(fp, key->rsa,
 212                     cipher, passphrase, len, NULL, NULL);
 213                 break;
 214         }
 215         fclose(fp);
 216         return success;
 217 }
 218
 219 int
 220 key_save_private(Key *key, const char *filename, const char *passphrase,
 221     const char *comment)
 222 {
 223         switch (key->type) {
 224         case KEY_RSA1:
 225                 return key_save_private_rsa1(key, filename, passphrase,
 226                     comment);
 227         case KEY_DSA:
 228         case KEY_RSA:
 229                 return key_save_private_pem(key, filename, passphrase,
 230                     comment);
 231         default:
 232                 break;
 233         }
 234         error("key_save_private: cannot save key type %d", key->type);
 235         return 0;
 236 }
 237
 238 /*
 239  * Loads the public part of the ssh v1 key file.  Returns NULL if an error was
 240  * encountered (the file does not exist or is not readable), and the key
 241  * otherwise.
 242  */
 243
 244 static Key *
 245 key_load_public_rsa1(int fd, const char *filename, char **commentp)
 246 {
 247         Buffer buffer;
 248         Key *pub;
 249         struct stat st;
 250         char *cp;
 251         u_int i;
 252         size_t len;
 253
 254         if (fstat(fd, &st) < 0) {
 255                 error("fstat for key file %.200s failed: %.100s",
 256                     filename, strerror(errno));
 257                 return NULL;
 258         }
 259         if (st.st_size > 1*1024*1024) {
 260                 error("key file %.200s too large", filename);
 261                 return NULL;
 262         }
 263         len = (size_t)st.st_size;               /* truncated */
 264
 265         buffer_init(&buffer);
 266         cp = buffer_append_space(&buffer, len);
 267
 268         if (atomicio(read, fd, cp, len) != len) {
 269                 debug("Read from key file %.200s failed: %.100s", filename,
 270                     strerror(errno));
 271                 buffer_free(&buffer);
 272                 return NULL;
 273         }
 274
 275         /* Check that it is at least big enough to contain the ID string. */
 276         if (len < sizeof(authfile_id_string)) {
 277                 debug3("Not a RSA1 key file %.200s.", filename);
 278                 buffer_free(&buffer);
 279                 return NULL;
 280         }
 281         /*
 282          * Make sure it begins with the id string.  Consume the id string
 283          * from the buffer.
 284          */
 285         for (i = 0; i < sizeof(authfile_id_string); i++)
 286                 if (buffer_get_char(&buffer) != authfile_id_string[i]) {
 287                         debug3("Not a RSA1 key file %.200s.", filename);
 288                         buffer_free(&buffer);
 289                         return NULL;
 290                 }
 291         /* Skip cipher type and reserved data. */
 292         (void) buffer_get_char(&buffer);        /* cipher type */
 293         (void) buffer_get_int(&buffer);         /* reserved */
 294
 295         /* Read the public key from the buffer. */
 296         (void) buffer_get_int(&buffer);
 297         pub = key_new(KEY_RSA1);
 298         buffer_get_bignum(&buffer, pub->rsa->n);
 299         buffer_get_bignum(&buffer, pub->rsa->e);
 300         if (commentp)
 301                 *commentp = buffer_get_string(&buffer, NULL);
 302         /* The encrypted private part is not parsed by this function. */
 303
 304         buffer_free(&buffer);
 305         return pub;
 306 }
 307
 308 /* load public key from private-key file, works only for SSH v1 */
 309 Key *
 310 key_load_public_type(int type, const char *filename, char **commentp)
 311 {
 312         Key *pub;
 313         int fd;
 314
 315         if (type == KEY_RSA1) {
 316                 fd = open(filename, O_RDONLY);
 317                 if (fd < 0)
 318                         return NULL;
 319                 pub = key_load_public_rsa1(fd, filename, commentp);
 320                 close(fd);
 321                 return pub;
 322         }
 323         return NULL;
 324 }
 325
 326 /*
 327  * Loads the private key from the file.  Returns 0 if an error is encountered
 328  * (file does not exist or is not readable, or passphrase is bad). This
 329  * initializes the private key.
 330  * Assumes we are called under uid of the owner of the file.
 331  */
 332
 333 static Key *
 334 key_load_private_rsa1(int fd, const char *filename, const char *passphrase,
 335     char **commentp)
 336 {
 337         u_int i;
 338         int check1, check2, cipher_type;
 339         size_t len;
 340         Buffer buffer, decrypted;
 341         u_char *cp;
 342         CipherContext ciphercontext;
 343         Cipher *cipher;
 344         Key *prv = NULL;
 345         struct stat st;
 346
 347         if (fstat(fd, &st) < 0) {
 348                 error("fstat for key file %.200s failed: %.100s",
 349                     filename, strerror(errno));
 350                 close(fd);
 351                 return NULL;
 352         }
 353         if (st.st_size > 1*1024*1024) {
 354                 error("key file %.200s too large", filename);
 355                 close(fd);
 356                 return (NULL);
 357         }
 358         len = (size_t)st.st_size;               /* truncated */
 359
 360         buffer_init(&buffer);
 361         cp = buffer_append_space(&buffer, len);
 362
 363         if (atomicio(read, fd, cp, len) != len) {
 364                 debug("Read from key file %.200s failed: %.100s", filename,
 365                     strerror(errno));
 366                 buffer_free(&buffer);
 367                 close(fd);
 368                 return NULL;
 369         }
 370
 371         /* Check that it is at least big enough to contain the ID string. */
 372         if (len < sizeof(authfile_id_string)) {
 373                 debug3("Not a RSA1 key file %.200s.", filename);
 374                 buffer_free(&buffer);
 375                 close(fd);
 376                 return NULL;
 377         }
 378         /*
 379          * Make sure it begins with the id string.  Consume the id string
 380          * from the buffer.
 381          */
 382         for (i = 0; i < sizeof(authfile_id_string); i++)
 383                 if (buffer_get_char(&buffer) != authfile_id_string[i]) {
 384                         debug3("Not a RSA1 key file %.200s.", filename);
 385                         buffer_free(&buffer);
 386                         close(fd);
 387                         return NULL;
 388                 }
 389
 390         /* Read cipher type. */
 391         cipher_type = buffer_get_char(&buffer);
 392         (void) buffer_get_int(&buffer); /* Reserved data. */
 393
 394         /* Read the public key from the buffer. */
 395         (void) buffer_get_int(&buffer);
 396         prv = key_new_private(KEY_RSA1);
 397
 398         buffer_get_bignum(&buffer, prv->rsa->n);
 399         buffer_get_bignum(&buffer, prv->rsa->e);
 400         if (commentp)
 401                 *commentp = buffer_get_string(&buffer, NULL);
 402         else
 403                 xfree(buffer_get_string(&buffer, NULL));
 404
 405         /* Check that it is a supported cipher. */
 406         cipher = cipher_by_number(cipher_type);
 407         if (cipher == NULL) {
 408                 debug("Unsupported cipher %d used in key file %.200s.",
 409                     cipher_type, filename);
 410                 buffer_free(&buffer);
 411                 goto fail;
 412         }
 413         /* Initialize space for decrypted data. */
 414         buffer_init(&decrypted);
 415         cp = buffer_append_space(&decrypted, buffer_len(&buffer));
 416
 417         /* Rest of the buffer is encrypted.  Decrypt it using the passphrase. */
 418         cipher_set_key_string(&ciphercontext, cipher, passphrase,
 419             CIPHER_DECRYPT);
 420         cipher_crypt(&ciphercontext, cp,
 421             buffer_ptr(&buffer), buffer_len(&buffer));
 422         cipher_cleanup(&ciphercontext);
 423         memset(&ciphercontext, 0, sizeof(ciphercontext));
 424         buffer_free(&buffer);
 425
 426         check1 = buffer_get_char(&decrypted);
 427         check2 = buffer_get_char(&decrypted);
 428         if (check1 != buffer_get_char(&decrypted) ||
 429             check2 != buffer_get_char(&decrypted)) {
 430                 if (strcmp(passphrase, "") != 0)
 431                         debug("Bad passphrase supplied for key file %.200s.",
 432                             filename);
 433                 /* Bad passphrase. */
 434                 buffer_free(&decrypted);
 435                 goto fail;
 436         }
 437         /* Read the rest of the private key. */
 438         buffer_get_bignum(&decrypted, prv->rsa->d);
 439         buffer_get_bignum(&decrypted, prv->rsa->iqmp);          /* u */
 440         /* in SSL and SSH v1 p and q are exchanged */
 441         buffer_get_bignum(&decrypted, prv->rsa->q);             /* p */
 442         buffer_get_bignum(&decrypted, prv->rsa->p);             /* q */
 443
 444         /* calculate p-1 and q-1 */
 445         rsa_generate_additional_parameters(prv->rsa);
 446
 447         buffer_free(&decrypted);
 448
 449         /* enable blinding */
 450         if (RSA_blinding_on(prv->rsa, NULL) != 1) {
 451                 error("key_load_private_rsa1: RSA_blinding_on failed");
 452                 goto fail;
 453         }
 454         close(fd);
 455         return prv;
 456
 457 fail:
 458         if (commentp)
 459                 xfree(*commentp);
 460         close(fd);
 461         key_free(prv);
 462         return NULL;
 463 }
 464
 465 Key *
 466 key_load_private_pem(int fd, int type, const char *passphrase,
 467     char **commentp)
 468 {
 469         FILE *fp;
 470         EVP_PKEY *pk = NULL;
 471         Key *prv = NULL;
 472         char *name = "<no key>";
 473
 474         fp = fdopen(fd, "r");
 475         if (fp == NULL) {
 476                 error("fdopen failed: %s", strerror(errno));
 477                 close(fd);
 478                 return NULL;
 479         }
 480         pk = PEM_read_PrivateKey(fp, NULL, NULL, (char *)passphrase);
 481         if (pk == NULL) {
 482                 debug("PEM_read_PrivateKey failed");
 483                 (void)ERR_get_error();
 484         } else if (pk->type == EVP_PKEY_RSA &&
 485             (type == KEY_UNSPEC||type==KEY_RSA)) {
 486                 prv = key_new(KEY_UNSPEC);
 487                 prv->rsa = EVP_PKEY_get1_RSA(pk);
 488                 prv->type = KEY_RSA;
 489                 name = "rsa w/o comment";
 490 #ifdef DEBUG_PK
 491                 RSA_print_fp(stderr, prv->rsa, 8);
 492 #endif
 493                 if (RSA_blinding_on(prv->rsa, NULL) != 1) {
 494                         error("key_load_private_pem: RSA_blinding_on failed");
 495                         key_free(prv);
 496                         prv = NULL;
 497                 }
 498         } else if (pk->type == EVP_PKEY_DSA &&
 499             (type == KEY_UNSPEC||type==KEY_DSA)) {
 500                 prv = key_new(KEY_UNSPEC);
 501                 prv->dsa = EVP_PKEY_get1_DSA(pk);
 502                 prv->type = KEY_DSA;
 503                 name = "dsa w/o comment";
 504 #ifdef DEBUG_PK
 505                 DSA_print_fp(stderr, prv->dsa, 8);
 506 #endif
 507         } else {
 508                 error("PEM_read_PrivateKey: mismatch or "
 509                     "unknown EVP_PKEY save_type %d", pk->save_type);
 510         }
 511         fclose(fp);
 512         if (pk != NULL)
 513                 EVP_PKEY_free(pk);
 514         if (prv != NULL && commentp)
 515                 *commentp = xstrdup(name);
 516         debug("read PEM private key done: type %s",
 517             prv ? key_type(prv) : "<unknown>");
 518         return prv;
 519 }
 520
 521 int
 522 key_perm_ok(int fd, const char *filename)
 523 {
 524         struct stat st;
 525
 526         if (fstat(fd, &st) < 0)
 527                 return 0;
 528         /*
 529          * if a key owned by the user is accessed, then we check the
 530          * permissions of the file. if the key owned by a different user,
 531          * then we don't care.
 532          */
 533 #ifdef HAVE_CYGWIN
 534         if (check_ntsec(filename))
 535 #endif
 536         if ((st.st_uid == getuid()) && (st.st_mode & 077) != 0) {
 537                 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
 538                 error("@         WARNING: UNPROTECTED PRIVATE KEY FILE!          @");
 539                 error("@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@");
 540                 error("Permissions 0%3.3o for '%s' are too open.",
 541                     (u_int)st.st_mode & 0777, filename);
 542                 error("It is recommended that your private key files are NOT accessible by others.");
 543                 error("This private key will be ignored.");
 544                 return 0;
 545         }
 546         return 1;
 547 }
 548
 549 Key *
 550 key_load_private_type(int type, const char *filename, const char *passphrase,
 551     char **commentp, int *perm_ok)
 552 {
 553         int fd;
 554
 555         fd = open(filename, O_RDONLY);
 556         if (fd < 0)
 557                 return NULL;
 558         if (!key_perm_ok(fd, filename)) {
 559                 if (perm_ok != NULL)
 560                         *perm_ok = 0;
 561                 error("bad permissions: ignore key: %s", filename);
 562                 close(fd);
 563                 return NULL;
 564         }
 565         if (perm_ok != NULL)
 566                 *perm_ok = 1;
 567         switch (type) {
 568         case KEY_RSA1:
 569                 return key_load_private_rsa1(fd, filename, passphrase,
 570                     commentp);
 571                 /* closes fd */
 572         case KEY_DSA:
 573         case KEY_RSA:
 574         case KEY_UNSPEC:
 575                 return key_load_private_pem(fd, type, passphrase, commentp);
 576                 /* closes fd */
 577         default:
 578                 close(fd);
 579                 break;
 580         }
 581         return NULL;
 582 }
 583
 584 Key *
 585 key_load_private(const char *filename, const char *passphrase,
 586     char **commentp)
 587 {
 588         Key *pub, *prv;
 589         int fd;
 590
 591         fd = open(filename, O_RDONLY);
 592         if (fd < 0)
 593                 return NULL;
 594         if (!key_perm_ok(fd, filename)) {
 595                 error("bad permissions: ignore key: %s", filename);
 596                 close(fd);
 597                 return NULL;
 598         }
 599         pub = key_load_public_rsa1(fd, filename, commentp);
 600         lseek(fd, (off_t) 0, SEEK_SET);         /* rewind */
 601         if (pub == NULL) {
 602                 /* closes fd */
 603                 prv = key_load_private_pem(fd, KEY_UNSPEC, passphrase, NULL);
 604                 /* use the filename as a comment for PEM */
 605                 if (commentp && prv)
 606                         *commentp = xstrdup(filename);
 607         } else {
 608                 /* it's a SSH v1 key if the public key part is readable */
 609                 key_free(pub);
 610                 /* closes fd */
 611                 prv = key_load_private_rsa1(fd, filename, passphrase, NULL);
 612         }
 613         return prv;
 614 }
 615
 616 static int
 617 key_try_load_public(Key *k, const char *filename, char **commentp)
 618 {
 619         FILE *f;
 620         char line[SSH_MAX_PUBKEY_BYTES];
 621         char *cp;
 622         u_long linenum = 0;
 623
 624         f = fopen(filename, "r");
 625         if (f != NULL) {
 626                 while (read_keyfile_line(f, filename, line, sizeof(line),
 627                             &linenum) != -1) {
 628                         cp = line;
 629                         switch (*cp) {
 630                         case '#':
 631                         case '\n':
 632                         case '\0':
 633                                 continue;
 634                         }
 635                         /* Skip leading whitespace. */
 636                         for (; *cp && (*cp == ' ' || *cp == '\t'); cp++)
 637                                 ;
 638                         if (*cp) {
 639                                 if (key_read(k, &cp) == 1) {
 640                                         if (commentp)
 641                                                 *commentp=xstrdup(filename);
 642                                         fclose(f);
 643                                         return 1;
 644                                 }
 645                         }
 646                 }
 647                 fclose(f);
 648         }
 649         return 0;
 650 }
 651
 652 /* load public key from ssh v1 private or any pubkey file */
 653 Key *
 654 key_load_public(const char *filename, char **commentp)
 655 {
 656         Key *pub;
 657         char file[MAXPATHLEN];
 658
 659         /* try rsa1 private key */
 660         pub = key_load_public_type(KEY_RSA1, filename, commentp);
 661         if (pub != NULL)
 662                 return pub;
 663
 664         /* try rsa1 public key */
 665         pub = key_new(KEY_RSA1);
 666         if (key_try_load_public(pub, filename, commentp) == 1)
 667                 return pub;
 668         key_free(pub);
 669
 670         /* try ssh2 public key */
 671         pub = key_new(KEY_UNSPEC);
 672         if (key_try_load_public(pub, filename, commentp) == 1)
 673                 return pub;
 674         if ((strlcpy(file, filename, sizeof file) < sizeof(file)) &&
 675             (strlcat(file, ".pub", sizeof file) < sizeof(file)) &&
 676             (key_try_load_public(pub, file, commentp) == 1))
 677                 return pub;
 678         key_free(pub);
 679         return NULL;
 680 }
 681
 682 char *
 683 blacklist_filename(const Key *key)
 684 {
 685         char *name;
 686
 687         xasprintf(&name, "%s.%s-%u",
 688             _PATH_BLACKLIST, key_type(key), key_size(key));
 689         return name;
 690 }
 691
 692 /* Scan a blacklist of known-vulnerable keys. */
 693 int
 694 blacklisted_key(const Key *key)
 695 {
 696         char *blacklist_file;
 697         int fd = -1;
 698         char *dgst_hex = NULL;
 699         char *dgst_packed = NULL, *p;
 700         int i;
 701         size_t line_len;
 702         struct stat st;
 703         char buf[256];
 704         off_t start, lower, upper;
 705         int ret = 0;
 706
 707         blacklist_file = blacklist_filename(key);
 708         debug("Checking blacklist file %s", blacklist_file);
 709         fd = open(blacklist_file, O_RDONLY);
 710         if (fd < 0)
 711                 goto out;
 712
 713         dgst_hex = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
 714         /* Remove all colons */
 715         dgst_packed = xcalloc(1, strlen(dgst_hex) + 1);
 716         for (i = 0, p = dgst_packed; dgst_hex[i]; i++)
 717                 if (dgst_hex[i] != ':')
 718                         *p++ = dgst_hex[i];
 719         /* Only compare least-significant 80 bits (to keep the blacklist
 720          * size down)
 721          */
 722         line_len = strlen(dgst_packed + 12);
 723         if (line_len > 32)
 724                 goto out;
 725
 726         /* Skip leading comments */
 727         start = 0;
 728         for (;;) {
 729                 ssize_t r;
 730                 char *newline;
 731
 732                 r = atomicio(read, fd, buf, 256);
 733                 if (r <= 0)
 734                         goto out;
 735                 if (buf[0] != '#')
 736                         break;
 737
 738                 newline = memchr(buf, '\n', 256);
 739                 if (!newline)
 740                         goto out;
 741                 start += newline + 1 - buf;
 742                 if (lseek(fd, start, SEEK_SET) < 0)
 743                         goto out;
 744         }
 745
 746         /* Initialise binary search record numbers */
 747         if (fstat(fd, &st) < 0)
 748                 goto out;
 749         lower = 0;
 750         upper = (st.st_size - start) / (line_len + 1);
 751
 752         while (lower != upper) {
 753                 off_t cur;
 754                 char buf[32];
 755                 int cmp;
 756
 757                 cur = lower + (upper - lower) / 2;
 758
 759                 /* Read this line and compare to digest; this is
 760                  * overflow-safe since cur < max(off_t) / (line_len + 1) */
 761                 if (lseek(fd, start + cur * (line_len + 1), SEEK_SET) < 0)
 762                         break;
 763                 if (atomicio(read, fd, buf, line_len) != line_len)
 764                         break;
 765                 cmp = memcmp(buf, dgst_packed + 12, line_len);
 766                 if (cmp < 0) {
 767                         if (cur == lower)
 768                                 break;
 769                         lower = cur;
 770                 } else if (cmp > 0) {
 771                         if (cur == upper)
 772                                 break;
 773                         upper = cur;
 774                 } else {
 775                         debug("Found %s in blacklist", dgst_hex);
 776                         ret = 1;
 777                         break;
 778                 }
 779         }
 780
 781 out:
 782         if (dgst_packed)
 783                 xfree(dgst_packed);
 784         if (dgst_hex)
 785                 xfree(dgst_hex);
 786         if (fd >= 0)
 787                 close(fd);
 788         xfree(blacklist_file);
 789         return ret;
 790 }