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 1.31 2003/04/08 20:21:28 itojun Exp $"); 40 41 #include "packet.h" 42 #include "match.h" 43 #include "key.h" 44 #include "hostfile.h" 45 #include "log.h" 46 47 /* 48 * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the 49 * pointer over the key. Skips any whitespace at the beginning and at end. 50 */ 51 52 int 53 hostfile_read_key(char **cpp, u_int *bitsp, Key *ret) 54 { 55 char *cp; 56 57 /* Skip leading whitespace. */ 58 for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++) 59 ; 60 61 if (key_read(ret, &cp) != 1) 62 return 0; 63 64 /* Skip trailing whitespace. */ 65 for (; *cp == ' ' || *cp == '\t'; cp++) 66 ; 67 68 /* Return results. */ 69 *cpp = cp; 70 *bitsp = key_size(ret); 71 return 1; 72 } 73 74 static int 75 hostfile_check_key(int bits, Key *key, const char *host, const char *filename, int linenum) 76 { 77 if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL) 78 return 1; 79 if (bits != BN_num_bits(key->rsa->n)) { 80 logit("Warning: %s, line %d: keysize mismatch for host %s: " 81 "actual %d vs. announced %d.", 82 filename, linenum, host, BN_num_bits(key->rsa->n), bits); 83 logit("Warning: replace %d with %d in %s, line %d.", 84 bits, BN_num_bits(key->rsa->n), filename, linenum); 85 } 86 return 1; 87 } 88 89 /* 90 * Checks whether the given host (which must be in all lowercase) is already 91 * in the list of our known hosts. Returns HOST_OK if the host is known and 92 * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED 93 * if the host is known but used to have a different host key. 94 * 95 * If no 'key' has been specified and a key of type 'keytype' is known 96 * for the specified host, then HOST_FOUND is returned. 97 */ 98 99 static HostStatus 100 check_host_in_hostfile_by_key_or_type(const char *filename, 101 const char *host, Key *key, int keytype, Key *found, int *numret) 102 { 103 FILE *f; 104 char line[8192]; 105 int linenum = 0; 106 u_int kbits; 107 char *cp, *cp2; 108 HostStatus end_return; 109 110 debug3("check_host_in_hostfile: filename %s", filename); 111 112 /* Open the file containing the list of known hosts. */ 113 f = fopen(filename, "r"); 114 if (!f) 115 return HOST_NEW; 116 117 /* 118 * Return value when the loop terminates. This is set to 119 * HOST_CHANGED if we have seen a different key for the host and have 120 * not found the proper one. 121 */ 122 end_return = HOST_NEW; 123 124 /* Go through the file. */ 125 while (fgets(line, sizeof(line), f)) { 126 cp = line; 127 linenum++; 128 129 /* Skip any leading whitespace, comments and empty lines. */ 130 for (; *cp == ' ' || *cp == '\t'; cp++) 131 ; 132 if (!*cp || *cp == '#' || *cp == '\n') 133 continue; 134 135 /* Find the end of the host name portion. */ 136 for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) 137 ; 138 139 /* Check if the host name matches. */ 140 if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) 141 continue; 142 143 /* Got a match. Skip host name. */ 144 cp = cp2; 145 146 /* 147 * Extract the key from the line. This will skip any leading 148 * whitespace. Ignore badly formatted lines. 149 */ 150 if (!hostfile_read_key(&cp, &kbits, found)) 151 continue; 152 153 if (numret != NULL) 154 *numret = linenum; 155 156 if (key == NULL) { 157 /* we found a key of the requested type */ 158 if (found->type == keytype) 159 return HOST_FOUND; 160 continue; 161 } 162 163 if (!hostfile_check_key(kbits, found, host, filename, linenum)) 164 continue; 165 166 /* Check if the current key is the same as the given key. */ 167 if (key_equal(key, found)) { 168 /* Ok, they match. */ 169 debug3("check_host_in_hostfile: match line %d", linenum); 170 fclose(f); 171 return HOST_OK; 172 } 173 /* 174 * They do not match. We will continue to go through the 175 * file; however, we note that we will not return that it is 176 * new. 177 */ 178 end_return = HOST_CHANGED; 179 } 180 /* Clear variables and close the file. */ 181 fclose(f); 182 183 /* 184 * Return either HOST_NEW or HOST_CHANGED, depending on whether we 185 * saw a different key for the host. 186 */ 187 return end_return; 188 } 189 190 HostStatus 191 check_host_in_hostfile(const char *filename, const char *host, Key *key, 192 Key *found, int *numret) 193 { 194 if (key == NULL) 195 fatal("no key to look up"); 196 return (check_host_in_hostfile_by_key_or_type(filename, host, key, 0, 197 found, numret)); 198 } 199 200 int 201 lookup_key_in_hostfile_by_type(const char *filename, const char *host, 202 int keytype, Key *found, int *numret) 203 { 204 return (check_host_in_hostfile_by_key_or_type(filename, host, NULL, 205 keytype, found, numret) == HOST_FOUND); 206 } 207 208 /* 209 * Appends an entry to the host file. Returns false if the entry could not 210 * be appended. 211 */ 212 213 int 214 add_host_to_hostfile(const char *filename, const char *host, Key *key) 215 { 216 FILE *f; 217 int success = 0; 218 if (key == NULL) 219 return 1; /* XXX ? */ 220 f = fopen(filename, "a"); 221 if (!f) 222 return 0; 223 fprintf(f, "%s ", host); 224 if (key_write(key, f)) { 225 success = 1; 226 } else { 227 error("add_host_to_hostfile: saving key in %s failed", filename); 228 } 229 fprintf(f, "\n"); 230 fclose(f); 231 return success; 232 } 233