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 1.29 2001/12/18 10:04:21 jakob Exp $"); 40 RCSID("$FreeBSD$"); 41 42 #include "packet.h" 43 #include "match.h" 44 #include "key.h" 45 #include "hostfile.h" 46 #include "log.h" 47 48 /* 49 * Parses an RSA (number of bits, e, n) or DSA key from a string. Moves the 50 * pointer over the key. Skips any whitespace at the beginning and at end. 51 */ 52 53 int 54 hostfile_read_key(char **cpp, u_int *bitsp, Key *ret) 55 { 56 char *cp; 57 58 /* Skip leading whitespace. */ 59 for (cp = *cpp; *cp == ' ' || *cp == '\t'; cp++) 60 ; 61 62 if (key_read(ret, &cp) != 1) 63 return 0; 64 65 /* Skip trailing whitespace. */ 66 for (; *cp == ' ' || *cp == '\t'; cp++) 67 ; 68 69 /* Return results. */ 70 *cpp = cp; 71 *bitsp = key_size(ret); 72 return 1; 73 } 74 75 static int 76 hostfile_check_key(int bits, Key *key, const char *host, const char *filename, int linenum) 77 { 78 if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL) 79 return 1; 80 if (bits != BN_num_bits(key->rsa->n)) { 81 log("Warning: %s, line %d: keysize mismatch for host %s: " 82 "actual %d vs. announced %d.", 83 filename, linenum, host, BN_num_bits(key->rsa->n), bits); 84 log("Warning: replace %d with %d in %s, line %d.", 85 bits, BN_num_bits(key->rsa->n), filename, linenum); 86 } 87 return 1; 88 } 89 90 /* 91 * Checks whether the given host (which must be in all lowercase) is already 92 * in the list of our known hosts. Returns HOST_OK if the host is known and 93 * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED 94 * if the host is known but used to have a different host key. 95 */ 96 97 HostStatus 98 check_host_in_hostfile(const char *filename, const char *host, Key *key, 99 Key *found, int *numret) 100 { 101 FILE *f; 102 char line[8192]; 103 int linenum = 0; 104 u_int kbits; 105 char *cp, *cp2; 106 HostStatus end_return; 107 108 debug3("check_host_in_hostfile: filename %s", filename); 109 if (key == NULL) 110 fatal("no key to look up"); 111 /* Open the file containing the list of known hosts. */ 112 f = fopen(filename, "r"); 113 if (!f) 114 return HOST_NEW; 115 116 /* 117 * Return value when the loop terminates. This is set to 118 * HOST_CHANGED if we have seen a different key for the host and have 119 * not found the proper one. 120 */ 121 end_return = HOST_NEW; 122 123 /* Go through the file. */ 124 while (fgets(line, sizeof(line), f)) { 125 cp = line; 126 linenum++; 127 128 /* Skip any leading whitespace, comments and empty lines. */ 129 for (; *cp == ' ' || *cp == '\t'; cp++) 130 ; 131 if (!*cp || *cp == '#' || *cp == '\n') 132 continue; 133 134 /* Find the end of the host name portion. */ 135 for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) 136 ; 137 138 /* Check if the host name matches. */ 139 if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) 140 continue; 141 142 /* Got a match. Skip host name. */ 143 cp = cp2; 144 145 /* 146 * Extract the key from the line. This will skip any leading 147 * whitespace. Ignore badly formatted lines. 148 */ 149 if (!hostfile_read_key(&cp, &kbits, found)) 150 continue; 151 if (!hostfile_check_key(kbits, found, host, filename, linenum)) 152 continue; 153 154 if (numret != NULL) 155 *numret = linenum; 156 157 /* Check if the current key is the same as the given key. */ 158 if (key_equal(key, found)) { 159 /* Ok, they match. */ 160 debug3("check_host_in_hostfile: match line %d", linenum); 161 fclose(f); 162 return HOST_OK; 163 } 164 /* 165 * They do not match. We will continue to go through the 166 * file; however, we note that we will not return that it is 167 * new. 168 */ 169 end_return = HOST_CHANGED; 170 } 171 /* Clear variables and close the file. */ 172 fclose(f); 173 174 /* 175 * Return either HOST_NEW or HOST_CHANGED, depending on whether we 176 * saw a different key for the host. 177 */ 178 return end_return; 179 } 180 181 /* 182 * Appends an entry to the host file. Returns false if the entry could not 183 * be appended. 184 */ 185 186 int 187 add_host_to_hostfile(const char *filename, const char *host, Key *key) 188 { 189 FILE *f; 190 int success = 0; 191 if (key == NULL) 192 return 1; /* XXX ? */ 193 f = fopen(filename, "a"); 194 if (!f) 195 return 0; 196 fprintf(f, "%s ", host); 197 if (key_write(key, f)) { 198 success = 1; 199 } else { 200 error("add_host_to_hostfile: saving key in %s failed", filename); 201 } 202 fprintf(f, "\n"); 203 fclose(f); 204 return success; 205 } 206