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 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 log("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 log("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 96 HostStatus 97 check_host_in_hostfile(const char *filename, const char *host, Key *key, 98 Key *found, int *numret) 99 { 100 FILE *f; 101 char line[8192]; 102 int linenum = 0; 103 u_int kbits; 104 char *cp, *cp2; 105 HostStatus end_return; 106 107 debug3("check_host_in_hostfile: filename %s", filename); 108 if (key == NULL) 109 fatal("no key to look up"); 110 /* Open the file containing the list of known hosts. */ 111 f = fopen(filename, "r"); 112 if (!f) 113 return HOST_NEW; 114 115 /* 116 * Return value when the loop terminates. This is set to 117 * HOST_CHANGED if we have seen a different key for the host and have 118 * not found the proper one. 119 */ 120 end_return = HOST_NEW; 121 122 /* Go through the file. */ 123 while (fgets(line, sizeof(line), f)) { 124 cp = line; 125 linenum++; 126 127 /* Skip any leading whitespace, comments and empty lines. */ 128 for (; *cp == ' ' || *cp == '\t'; cp++) 129 ; 130 if (!*cp || *cp == '#' || *cp == '\n') 131 continue; 132 133 /* Find the end of the host name portion. */ 134 for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) 135 ; 136 137 /* Check if the host name matches. */ 138 if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) 139 continue; 140 141 /* Got a match. Skip host name. */ 142 cp = cp2; 143 144 /* 145 * Extract the key from the line. This will skip any leading 146 * whitespace. Ignore badly formatted lines. 147 */ 148 if (!hostfile_read_key(&cp, &kbits, found)) 149 continue; 150 if (!hostfile_check_key(kbits, found, host, filename, linenum)) 151 continue; 152 153 if (numret != NULL) 154 *numret = linenum; 155 156 /* Check if the current key is the same as the given key. */ 157 if (key_equal(key, found)) { 158 /* Ok, they match. */ 159 debug3("check_host_in_hostfile: match line %d", linenum); 160 fclose(f); 161 return HOST_OK; 162 } 163 /* 164 * They do not match. We will continue to go through the 165 * file; however, we note that we will not return that it is 166 * new. 167 */ 168 end_return = HOST_CHANGED; 169 } 170 /* Clear variables and close the file. */ 171 fclose(f); 172 173 /* 174 * Return either HOST_NEW or HOST_CHANGED, depending on whether we 175 * saw a different key for the host. 176 */ 177 return end_return; 178 } 179 180 /* 181 * Appends an entry to the host file. Returns false if the entry could not 182 * be appended. 183 */ 184 185 int 186 add_host_to_hostfile(const char *filename, const char *host, Key *key) 187 { 188 FILE *f; 189 int success = 0; 190 if (key == NULL) 191 return 1; /* XXX ? */ 192 f = fopen(filename, "a"); 193 if (!f) 194 return 0; 195 fprintf(f, "%s ", host); 196 if (key_write(key, f)) { 197 success = 1; 198 } else { 199 error("add_host_to_hostfile: saving key in %s failed", filename); 200 } 201 fprintf(f, "\n"); 202 fclose(f); 203 return success; 204 } 205