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 * Functions for manipulating the known hosts files. 6 * 7 * As far as I am concerned, the code I have written for this software 8 * can be used freely for any purpose. Any derived versions of this 9 * software must be clearly marked as such, and if the derived work is 10 * incompatible with the protocol description in the RFC file, it must be 11 * called by a name other than "ssh" or "Secure Shell". 12 * 13 * 14 * Copyright (c) 1999, 2000 Markus Friedl. All rights reserved. 15 * Copyright (c) 1999 Niels Provos. 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: hostfile.c,v 1.30 2002/07/24 16:11:18 markus Exp $"); 40 41 #pragma ident "%Z%%M% %I% %E% SMI" 42 43 #include "packet.h" 44 #include "match.h" 45 #include "key.h" 46 #include "hostfile.h" 47 #include "log.h" 48 49 /* 50 * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the 51 * pointer over the key. Skips any whitespace at the beginning and at end. 52 */ 53 54 int 55 hostfile_read_key(char **cpp, u_int *bitsp, Key *ret) 56 { 57 char *cp; 58 59 /* Skip leading whitespace. */ 60 for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++) 61 ; 62 63 if (key_read(ret, &cp) != 1) 64 return 0; 65 66 /* Skip trailing whitespace. */ 67 for (; *cp == ' ' || *cp == '\t'; cp++) 68 ; 69 70 /* Return results. */ 71 *cpp = cp; 72 *bitsp = key_size(ret); 73 return 1; 74 } 75 76 static int 77 hostfile_check_key(int bits, Key *key, const char *host, const char *filename, int linenum) 78 { 79 if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL) 80 return 1; 81 if (bits != BN_num_bits(key->rsa->n)) { 82 log("Warning: %s, line %d: keysize mismatch for host %s: " 83 "actual %d vs. announced %d.", 84 filename, linenum, host, BN_num_bits(key->rsa->n), bits); 85 log("Warning: replace %d with %d in %s, line %d.", 86 bits, BN_num_bits(key->rsa->n), filename, linenum); 87 } 88 return 1; 89 } 90 91 /* 92 * Checks whether the given host (which must be in all lowercase) is already 93 * in the list of our known hosts. Returns HOST_OK if the host is known and 94 * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED 95 * if the host is known but used to have a different host key. 96 * 97 * If no 'key' has been specified and a key of type 'keytype' is known 98 * for the specified host, then HOST_FOUND is returned. 99 */ 100 101 static HostStatus 102 check_host_in_hostfile_by_key_or_type(const char *filename, 103 const char *host, Key *key, int keytype, Key *found, int *numret) 104 { 105 FILE *f; 106 char line[8192]; 107 int linenum = 0; 108 u_int kbits; 109 char *cp, *cp2; 110 HostStatus end_return; 111 112 debug3("check_host_in_hostfile: filename %s", filename); 113 114 /* Open the file containing the list of known hosts. */ 115 f = fopen(filename, "r"); 116 if (!f) 117 return HOST_NEW; 118 119 /* 120 * Return value when the loop terminates. This is set to 121 * HOST_CHANGED if we have seen a different key for the host and have 122 * not found the proper one. 123 */ 124 end_return = HOST_NEW; 125 126 /* Go through the file. */ 127 while (fgets(line, sizeof(line), f)) { 128 cp = line; 129 linenum++; 130 131 /* Skip any leading whitespace, comments and empty lines. */ 132 for (; *cp == ' ' || *cp == '\t'; cp++) 133 ; 134 if (!*cp || *cp == '#' || *cp == '\n') 135 continue; 136 137 /* Find the end of the host name portion. */ 138 for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) 139 ; 140 141 /* Check if the host name matches. */ 142 if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) 143 continue; 144 145 /* Got a match. Skip host name. */ 146 cp = cp2; 147 148 /* 149 * Extract the key from the line. This will skip any leading 150 * whitespace. Ignore badly formatted lines. 151 */ 152 if (!hostfile_read_key(&cp, &kbits, found)) 153 continue; 154 155 if (numret != NULL) 156 *numret = linenum; 157 158 if (key == NULL) { 159 /* we found a key of the requested type */ 160 if (found->type == keytype) 161 return HOST_FOUND; 162 continue; 163 } 164 165 if (!hostfile_check_key(kbits, found, host, filename, linenum)) 166 continue; 167 168 /* Check if the current key is the same as the given key. */ 169 if (key_equal(key, found)) { 170 /* Ok, they match. */ 171 debug3("check_host_in_hostfile: match line %d", linenum); 172 fclose(f); 173 return HOST_OK; 174 } 175 /* 176 * They do not match. We will continue to go through the 177 * file; however, we note that we will not return that it is 178 * new. 179 */ 180 end_return = HOST_CHANGED; 181 } 182 /* Clear variables and close the file. */ 183 fclose(f); 184 185 /* 186 * Return either HOST_NEW or HOST_CHANGED, depending on whether we 187 * saw a different key for the host. 188 */ 189 return end_return; 190 } 191 192 HostStatus 193 check_host_in_hostfile(const char *filename, const char *host, Key *key, 194 Key *found, int *numret) 195 { 196 if (key == NULL) 197 fatal("no key to look up"); 198 return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0, 199 found, numret)); 200 } 201 202 int 203 lookup_key_in_hostfile_by_type(const char *filename, const char *host, 204 int keytype, Key *found, int *numret) 205 { 206 return (check_host_in_hostfile_by_key_or_type(filename, host, NULL, 207 keytype, found, numret) == HOST_FOUND); 208 } 209 210 /* 211 * Appends an entry to the host file. Returns false if the entry could not 212 * be appended. 213 */ 214 215 int 216 add_host_to_hostfile(const char *filename, const char *host, Key *key) 217 { 218 FILE *f; 219 int success = 0; 220 if (key == NULL) 221 return 1; /* XXX ? */ 222 f = fopen(filename, "a"); 223 if (!f) 224 return 0; 225 fprintf(f, "%s ", host); 226 if (key_write(key, f)) { 227 success = 1; 228 } else { 229 error("add_host_to_hostfile: saving key in %s failed", filename); 230 } 231 fprintf(f, "\n"); 232 fclose(f); 233 return success; 234 } 235