1 /* 2 * Copyright (c) 2002 Markus Friedl. All rights reserved. 3 * 4 * Redistribution and use in source and binary forms, with or without 5 * modification, are permitted provided that the following conditions 6 * are met: 7 * 1. Redistributions of source code must retain the above copyright 8 * notice, this list of conditions and the following disclaimer. 9 * 2. Redistributions in binary form must reproduce the above copyright 10 * notice, this list of conditions and the following disclaimer in the 11 * documentation and/or other materials provided with the distribution. 12 * 13 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 14 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 15 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 16 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 17 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 18 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 19 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 20 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 21 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 22 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 23 */ 24 #include "includes.h" 25 RCSID("$OpenBSD: ssh-keysign.c,v 1.15 2004/01/19 21:25:15 markus Exp $"); 26 27 #include <openssl/evp.h> 28 #include <openssl/rand.h> 29 #include <openssl/rsa.h> 30 31 #include "log.h" 32 #include "key.h" 33 #include "ssh.h" 34 #include "ssh2.h" 35 #include "misc.h" 36 #include "xmalloc.h" 37 #include "buffer.h" 38 #include "bufaux.h" 39 #include "authfile.h" 40 #include "msg.h" 41 #include "canohost.h" 42 #include "pathnames.h" 43 #include "readconf.h" 44 45 /* XXX readconf.c needs these */ 46 uid_t original_real_uid; 47 48 #ifdef HAVE___PROGNAME 49 extern char *__progname; 50 #else 51 char *__progname; 52 #endif 53 54 static int 55 valid_request(struct passwd *pw, char *host, Key **ret, u_char *data, 56 u_int datalen) 57 { 58 Buffer b; 59 Key *key = NULL; 60 u_char *pkblob; 61 u_int blen, len; 62 char *pkalg, *p; 63 int pktype, fail; 64 65 fail = 0; 66 67 buffer_init(&b); 68 buffer_append(&b, data, datalen); 69 70 /* session id, currently limited to SHA1 (20 bytes) */ 71 p = buffer_get_string(&b, &len); 72 if (len != 20) 73 fail++; 74 xfree(p); 75 76 if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST) 77 fail++; 78 79 /* server user */ 80 buffer_skip_string(&b); 81 82 /* service */ 83 p = buffer_get_string(&b, NULL); 84 if (strcmp("ssh-connection", p) != 0) 85 fail++; 86 xfree(p); 87 88 /* method */ 89 p = buffer_get_string(&b, NULL); 90 if (strcmp("hostbased", p) != 0) 91 fail++; 92 xfree(p); 93 94 /* pubkey */ 95 pkalg = buffer_get_string(&b, NULL); 96 pkblob = buffer_get_string(&b, &blen); 97 98 pktype = key_type_from_name(pkalg); 99 if (pktype == KEY_UNSPEC) 100 fail++; 101 else if ((key = key_from_blob(pkblob, blen)) == NULL) 102 fail++; 103 else if (key->type != pktype) 104 fail++; 105 xfree(pkalg); 106 xfree(pkblob); 107 108 /* client host name, handle trailing dot */ 109 p = buffer_get_string(&b, &len); 110 debug2("valid_request: check expect chost %s got %s", host, p); 111 if (strlen(host) != len - 1) 112 fail++; 113 else if (p[len - 1] != '.') 114 fail++; 115 else if (strncasecmp(host, p, len - 1) != 0) 116 fail++; 117 xfree(p); 118 119 /* local user */ 120 p = buffer_get_string(&b, NULL); 121 122 if (strcmp(pw->pw_name, p) != 0) 123 fail++; 124 xfree(p); 125 126 /* end of message */ 127 if (buffer_len(&b) != 0) 128 fail++; 129 buffer_free(&b); 130 131 debug3("valid_request: fail %d", fail); 132 133 if (fail && key != NULL) 134 key_free(key); 135 else 136 *ret = key; 137 138 return (fail ? -1 : 0); 139 } 140 141 int 142 main(int argc, char **argv) 143 { 144 Buffer b; 145 Options options; 146 Key *keys[2], *key; 147 struct passwd *pw; 148 int key_fd[2], i, found, version = 2, fd; 149 u_char *signature, *data; 150 char *host; 151 u_int slen, dlen; 152 u_int32_t rnd[256]; 153 154 key_fd[0] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY); 155 key_fd[1] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY); 156 157 seteuid(getuid()); 158 setuid(getuid()); 159 160 init_rng(); 161 seed_rng(); 162 arc4random_stir(); 163 164 #ifdef DEBUG_SSH_KEYSIGN 165 log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0); 166 #endif 167 168 /* verify that ssh-keysign is enabled by the admin */ 169 original_real_uid = getuid(); /* XXX readconf.c needs this */ 170 initialize_options(&options); 171 (void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options); 172 fill_default_options(&options); 173 if (options.enable_ssh_keysign != 1) 174 fatal("ssh-keysign not enabled in %s", 175 _PATH_HOST_CONFIG_FILE); 176 177 if (key_fd[0] == -1 && key_fd[1] == -1) 178 fatal("could not open any host key"); 179 180 if ((pw = getpwuid(getuid())) == NULL) 181 fatal("getpwuid failed"); 182 pw = pwcopy(pw); 183 184 SSLeay_add_all_algorithms(); 185 for (i = 0; i < 256; i++) 186 rnd[i] = arc4random(); 187 RAND_seed(rnd, sizeof(rnd)); 188 189 found = 0; 190 for (i = 0; i < 2; i++) { 191 keys[i] = NULL; 192 if (key_fd[i] == -1) 193 continue; 194 keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC, 195 NULL, NULL); 196 close(key_fd[i]); 197 if (keys[i] != NULL) 198 found = 1; 199 } 200 if (!found) 201 fatal("no hostkey found"); 202 203 buffer_init(&b); 204 if (ssh_msg_recv(STDIN_FILENO, &b) < 0) 205 fatal("ssh_msg_recv failed"); 206 if (buffer_get_char(&b) != version) 207 fatal("bad version"); 208 fd = buffer_get_int(&b); 209 if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO)) 210 fatal("bad fd"); 211 if ((host = get_local_name(fd)) == NULL) 212 fatal("cannot get sockname for fd"); 213 214 data = buffer_get_string(&b, &dlen); 215 if (valid_request(pw, host, &key, data, dlen) < 0) 216 fatal("not a valid request"); 217 xfree(host); 218 219 found = 0; 220 for (i = 0; i < 2; i++) { 221 if (keys[i] != NULL && 222 key_equal(key, keys[i])) { 223 found = 1; 224 break; 225 } 226 } 227 if (!found) 228 fatal("no matching hostkey found"); 229 230 if (key_sign(keys[i], &signature, &slen, data, dlen) != 0) 231 fatal("key_sign failed"); 232 xfree(data); 233 234 /* send reply */ 235 buffer_clear(&b); 236 buffer_put_string(&b, signature, slen); 237 if (ssh_msg_send(STDOUT_FILENO, version, &b) == -1) 238 fatal("ssh_msg_send failed"); 239 240 return (0); 241 } 242