1 /* $OpenBSD: hostfile.c,v 1.45 2006/08/03 03:34:42 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 * Functions for manipulating the known hosts files. 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) 1999, 2000 Markus Friedl. All rights reserved. 16 * Copyright (c) 1999 Niels Provos. 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 43 #include <netinet/in.h> 44 45 #include <openssl/hmac.h> 46 #include <openssl/sha.h> 47 48 #include <resolv.h> 49 #include <stdarg.h> 50 #include <stdio.h> 51 #include <stdlib.h> 52 #include <string.h> 53 54 #include "xmalloc.h" 55 #include "match.h" 56 #include "key.h" 57 #include "hostfile.h" 58 #include "log.h" 59 60 static int 61 extract_salt(const char *s, u_int l, char *salt, size_t salt_len) 62 { 63 char *p, *b64salt; 64 u_int b64len; 65 int ret; 66 67 if (l < sizeof(HASH_MAGIC) - 1) { 68 debug2("extract_salt: string too short"); 69 return (-1); 70 } 71 if (strncmp(s, HASH_MAGIC, sizeof(HASH_MAGIC) - 1) != 0) { 72 debug2("extract_salt: invalid magic identifier"); 73 return (-1); 74 } 75 s += sizeof(HASH_MAGIC) - 1; 76 l -= sizeof(HASH_MAGIC) - 1; 77 if ((p = memchr(s, HASH_DELIM, l)) == NULL) { 78 debug2("extract_salt: missing salt termination character"); 79 return (-1); 80 } 81 82 b64len = p - s; 83 /* Sanity check */ 84 if (b64len == 0 || b64len > 1024) { 85 debug2("extract_salt: bad encoded salt length %u", b64len); 86 return (-1); 87 } 88 b64salt = xmalloc(1 + b64len); 89 memcpy(b64salt, s, b64len); 90 b64salt[b64len] = '\0'; 91 92 ret = __b64_pton(b64salt, salt, salt_len); 93 xfree(b64salt); 94 if (ret == -1) { 95 debug2("extract_salt: salt decode error"); 96 return (-1); 97 } 98 if (ret != SHA_DIGEST_LENGTH) { 99 debug2("extract_salt: expected salt len %d, got %d", 100 SHA_DIGEST_LENGTH, ret); 101 return (-1); 102 } 103 104 return (0); 105 } 106 107 char * 108 host_hash(const char *host, const char *name_from_hostfile, u_int src_len) 109 { 110 const EVP_MD *md = EVP_sha1(); 111 HMAC_CTX mac_ctx; 112 char salt[256], result[256], uu_salt[512], uu_result[512]; 113 static char encoded[1024]; 114 u_int i, len; 115 116 len = EVP_MD_size(md); 117 118 if (name_from_hostfile == NULL) { 119 /* Create new salt */ 120 for (i = 0; i < len; i++) 121 salt[i] = arc4random(); 122 } else { 123 /* Extract salt from known host entry */ 124 if (extract_salt(name_from_hostfile, src_len, salt, 125 sizeof(salt)) == -1) 126 return (NULL); 127 } 128 129 HMAC_Init(&mac_ctx, salt, len, md); 130 HMAC_Update(&mac_ctx, host, strlen(host)); 131 HMAC_Final(&mac_ctx, result, NULL); 132 HMAC_cleanup(&mac_ctx); 133 134 if (__b64_ntop(salt, len, uu_salt, sizeof(uu_salt)) == -1 || 135 __b64_ntop(result, len, uu_result, sizeof(uu_result)) == -1) 136 fatal("host_hash: __b64_ntop failed"); 137 138 snprintf(encoded, sizeof(encoded), "%s%s%c%s", HASH_MAGIC, uu_salt, 139 HASH_DELIM, uu_result); 140 141 return (encoded); 142 } 143 144 /* 145 * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the 146 * pointer over the key. Skips any whitespace at the beginning and at end. 147 */ 148 149 int 150 hostfile_read_key(char **cpp, u_int *bitsp, Key *ret) 151 { 152 char *cp; 153 154 /* Skip leading whitespace. */ 155 for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++) 156 ; 157 158 if (key_read(ret, &cp) != 1) 159 return 0; 160 161 /* Skip trailing whitespace. */ 162 for (; *cp == ' ' || *cp == '\t'; cp++) 163 ; 164 165 /* Return results. */ 166 *cpp = cp; 167 *bitsp = key_size(ret); 168 return 1; 169 } 170 171 static int 172 hostfile_check_key(int bits, const Key *key, const char *host, const char *filename, int linenum) 173 { 174 if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL) 175 return 1; 176 if (bits != BN_num_bits(key->rsa->n)) { 177 logit("Warning: %s, line %d: keysize mismatch for host %s: " 178 "actual %d vs. announced %d.", 179 filename, linenum, host, BN_num_bits(key->rsa->n), bits); 180 logit("Warning: replace %d with %d in %s, line %d.", 181 bits, BN_num_bits(key->rsa->n), filename, linenum); 182 } 183 return 1; 184 } 185 186 /* 187 * Checks whether the given host (which must be in all lowercase) is already 188 * in the list of our known hosts. Returns HOST_OK if the host is known and 189 * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED 190 * if the host is known but used to have a different host key. 191 * 192 * If no 'key' has been specified and a key of type 'keytype' is known 193 * for the specified host, then HOST_FOUND is returned. 194 */ 195 196 static HostStatus 197 check_host_in_hostfile_by_key_or_type(const char *filename, 198 const char *host, const Key *key, int keytype, Key *found, int *numret) 199 { 200 FILE *f; 201 char line[8192]; 202 int linenum = 0; 203 u_int kbits; 204 char *cp, *cp2, *hashed_host; 205 HostStatus end_return; 206 207 debug3("check_host_in_hostfile: filename %s", filename); 208 209 /* Open the file containing the list of known hosts. */ 210 f = fopen(filename, "r"); 211 if (!f) 212 return HOST_NEW; 213 214 /* 215 * Return value when the loop terminates. This is set to 216 * HOST_CHANGED if we have seen a different key for the host and have 217 * not found the proper one. 218 */ 219 end_return = HOST_NEW; 220 221 /* Go through the file. */ 222 while (fgets(line, sizeof(line), f)) { 223 cp = line; 224 linenum++; 225 226 /* Skip any leading whitespace, comments and empty lines. */ 227 for (; *cp == ' ' || *cp == '\t'; cp++) 228 ; 229 if (!*cp || *cp == '#' || *cp == '\n') 230 continue; 231 232 /* Find the end of the host name portion. */ 233 for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) 234 ; 235 236 /* Check if the host name matches. */ 237 if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) { 238 if (*cp != HASH_DELIM) 239 continue; 240 hashed_host = host_hash(host, cp, (u_int) (cp2 - cp)); 241 if (hashed_host == NULL) { 242 debug("Invalid hashed host line %d of %s", 243 linenum, filename); 244 continue; 245 } 246 if (strncmp(hashed_host, cp, (u_int) (cp2 - cp)) != 0) 247 continue; 248 } 249 250 /* Got a match. Skip host name. */ 251 cp = cp2; 252 253 /* 254 * Extract the key from the line. This will skip any leading 255 * whitespace. Ignore badly formatted lines. 256 */ 257 if (!hostfile_read_key(&cp, &kbits, found)) 258 continue; 259 260 if (numret != NULL) 261 *numret = linenum; 262 263 if (key == NULL) { 264 /* we found a key of the requested type */ 265 if (found->type == keytype) { 266 fclose(f); 267 return HOST_FOUND; 268 } 269 continue; 270 } 271 272 if (!hostfile_check_key(kbits, found, host, filename, linenum)) 273 continue; 274 275 /* Check if the current key is the same as the given key. */ 276 if (key_equal(key, found)) { 277 /* Ok, they match. */ 278 debug3("check_host_in_hostfile: match line %d", linenum); 279 fclose(f); 280 return HOST_OK; 281 } 282 /* 283 * They do not match. We will continue to go through the 284 * file; however, we note that we will not return that it is 285 * new. 286 */ 287 end_return = HOST_CHANGED; 288 } 289 /* Clear variables and close the file. */ 290 fclose(f); 291 292 /* 293 * Return either HOST_NEW or HOST_CHANGED, depending on whether we 294 * saw a different key for the host. 295 */ 296 return end_return; 297 } 298 299 HostStatus 300 check_host_in_hostfile(const char *filename, const char *host, const Key *key, 301 Key *found, int *numret) 302 { 303 if (key == NULL) 304 fatal("no key to look up"); 305 return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0, 306 found, numret)); 307 } 308 309 int 310 lookup_key_in_hostfile_by_type(const char *filename, const char *host, 311 int keytype, Key *found, int *numret) 312 { 313 return (check_host_in_hostfile_by_key_or_type(filename, host, NULL, 314 keytype, found, numret) == HOST_FOUND); 315 } 316 317 /* 318 * Appends an entry to the host file. Returns false if the entry could not 319 * be appended. 320 */ 321 322 int 323 add_host_to_hostfile(const char *filename, const char *host, const Key *key, 324 int store_hash) 325 { 326 FILE *f; 327 int success = 0; 328 char *hashed_host = NULL; 329 330 if (key == NULL) 331 return 1; /* XXX ? */ 332 f = fopen(filename, "a"); 333 if (!f) 334 return 0; 335 336 if (store_hash) { 337 if ((hashed_host = host_hash(host, NULL, 0)) == NULL) { 338 error("add_host_to_hostfile: host_hash failed"); 339 fclose(f); 340 return 0; 341 } 342 } 343 fprintf(f, "%s ", store_hash ? hashed_host : host); 344 345 if (key_write(key, f)) { 346 success = 1; 347 } else { 348 error("add_host_to_hostfile: saving key in %s failed", filename); 349 } 350 fprintf(f, "\n"); 351 fclose(f); 352 return success; 353 } 354