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 1.28 2001/06/25 08:25:37 markus 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 static 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 int 75 auth_rsa_read_key(char **cpp, u_int *bitsp, BIGNUM * e, BIGNUM * n) 76 { 77 Key *k = key_new(KEY_RSA1); 78 int ret = hostfile_read_key(cpp, bitsp, k); 79 BN_copy(e, k->rsa->e); 80 BN_copy(n, k->rsa->n); 81 key_free(k); 82 return ret; 83 } 84 85 static int 86 hostfile_check_key(int bits, Key *key, const char *host, const char *filename, int linenum) 87 { 88 if (key == NULL || key->type != KEY_RSA1 || key->rsa == NULL) 89 return 1; 90 if (bits != BN_num_bits(key->rsa->n)) { 91 log("Warning: %s, line %d: keysize mismatch for host %s: " 92 "actual %d vs. announced %d.", 93 filename, linenum, host, BN_num_bits(key->rsa->n), bits); 94 log("Warning: replace %d with %d in %s, line %d.", 95 bits, BN_num_bits(key->rsa->n), filename, linenum); 96 } 97 return 1; 98 } 99 100 /* 101 * Checks whether the given host (which must be in all lowercase) is already 102 * in the list of our known hosts. Returns HOST_OK if the host is known and 103 * has the specified key, HOST_NEW if the host is not known, and HOST_CHANGED 104 * if the host is known but used to have a different host key. 105 */ 106 107 HostStatus 108 check_host_in_hostfile(const char *filename, const char *host, Key *key, 109 Key *found, int *numret) 110 { 111 FILE *f; 112 char line[8192]; 113 int linenum = 0; 114 u_int kbits; 115 char *cp, *cp2; 116 HostStatus end_return; 117 118 debug3("check_host_in_hostfile: filename %s", filename); 119 if (key == NULL) 120 fatal("no key to look up"); 121 /* Open the file containing the list of known hosts. */ 122 f = fopen(filename, "r"); 123 if (!f) 124 return HOST_NEW; 125 126 /* 127 * Return value when the loop terminates. This is set to 128 * HOST_CHANGED if we have seen a different key for the host and have 129 * not found the proper one. 130 */ 131 end_return = HOST_NEW; 132 133 /* Go through the file. */ 134 while (fgets(line, sizeof(line), f)) { 135 cp = line; 136 linenum++; 137 138 /* Skip any leading whitespace, comments and empty lines. */ 139 for (; *cp == ' ' || *cp == '\t'; cp++) 140 ; 141 if (!*cp || *cp == '#' || *cp == '\n') 142 continue; 143 144 /* Find the end of the host name portion. */ 145 for (cp2 = cp; *cp2 && *cp2 != ' ' && *cp2 != '\t'; cp2++) 146 ; 147 148 /* Check if the host name matches. */ 149 if (match_hostname(host, cp, (u_int) (cp2 - cp)) != 1) 150 continue; 151 152 /* Got a match. Skip host name. */ 153 cp = cp2; 154 155 /* 156 * Extract the key from the line. This will skip any leading 157 * whitespace. Ignore badly formatted lines. 158 */ 159 if (!hostfile_read_key(&cp, &kbits, found)) 160 continue; 161 if (!hostfile_check_key(kbits, found, host, filename, linenum)) 162 continue; 163 164 if (numret != NULL) 165 *numret = linenum; 166 167 /* Check if the current key is the same as the given key. */ 168 if (key_equal(key, found)) { 169 /* Ok, they match. */ 170 debug3("check_host_in_hostfile: match line %d", linenum); 171 fclose(f); 172 return HOST_OK; 173 } 174 /* 175 * They do not match. We will continue to go through the 176 * file; however, we note that we will not return that it is 177 * new. 178 */ 179 end_return = HOST_CHANGED; 180 } 181 /* Clear variables and close the file. */ 182 fclose(f); 183 184 /* 185 * Return either HOST_NEW or HOST_CHANGED, depending on whether we 186 * saw a different key for the host. 187 */ 188 return end_return; 189 } 190 191 /* 192 * Appends an entry to the host file. Returns false if the entry could not 193 * be appended. 194 */ 195 196 int 197 add_host_to_hostfile(const char *filename, const char *host, Key *key) 198 { 199 FILE *f; 200 int success = 0; 201 if (key == NULL) 202 return 1; /* XXX ? */ 203 f = fopen(filename, "a"); 204 if (!f) 205 return 0; 206 fprintf(f, "%s ", host); 207 if (key_write(key, f)) { 208 success = 1; 209 } else { 210 error("add_host_to_hostfile: saving key in %s failed", filename); 211 } 212 fprintf(f, "\n"); 213 fclose(f); 214 return success; 215 } 216