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 1.10 2003/03/13 11:42:19 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 uid_t original_real_uid; /* XXX readconf.c needs this */ 46 47 #ifdef HAVE___PROGNAME 48 extern char *__progname; 49 #else 50 char *__progname; 51 #endif 52 53 static int 54 valid_request(struct passwd *pw, char *host, Key **ret, u_char *data, 55 u_int datalen) 56 { 57 Buffer b; 58 Key *key; 59 u_char *pkblob; 60 u_int blen, len; 61 char *pkalg, *p; 62 int pktype, fail; 63 64 fail = 0; 65 66 buffer_init(&b); 67 buffer_append(&b, data, datalen); 68 69 /* session id, currently limited to SHA1 (20 bytes) */ 70 p = buffer_get_string(&b, &len); 71 if (len != 20) 72 fail++; 73 xfree(p); 74 75 if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST) 76 fail++; 77 78 /* server user */ 79 buffer_skip_string(&b); 80 81 /* service */ 82 p = buffer_get_string(&b, NULL); 83 if (strcmp("ssh-connection", p) != 0) 84 fail++; 85 xfree(p); 86 87 /* method */ 88 p = buffer_get_string(&b, NULL); 89 if (strcmp("hostbased", p) != 0) 90 fail++; 91 xfree(p); 92 93 /* pubkey */ 94 pkalg = buffer_get_string(&b, NULL); 95 pkblob = buffer_get_string(&b, &blen); 96 97 pktype = key_type_from_name(pkalg); 98 if (pktype == KEY_UNSPEC) 99 fail++; 100 else if ((key = key_from_blob(pkblob, blen)) == NULL) 101 fail++; 102 else if (key->type != pktype) 103 fail++; 104 xfree(pkalg); 105 xfree(pkblob); 106 107 /* client host name, handle trailing dot */ 108 p = buffer_get_string(&b, &len); 109 debug2("valid_request: check expect chost %s got %s", host, p); 110 if (strlen(host) != len - 1) 111 fail++; 112 else if (p[len - 1] != '.') 113 fail++; 114 else if (strncasecmp(host, p, len - 1) != 0) 115 fail++; 116 xfree(p); 117 118 /* local user */ 119 p = buffer_get_string(&b, NULL); 120 121 if (strcmp(pw->pw_name, p) != 0) 122 fail++; 123 xfree(p); 124 125 /* end of message */ 126 if (buffer_len(&b) != 0) 127 fail++; 128 129 debug3("valid_request: fail %d", fail); 130 131 if (fail && key != NULL) 132 key_free(key); 133 else 134 *ret = key; 135 136 return (fail ? -1 : 0); 137 } 138 139 int 140 main(int argc, char **argv) 141 { 142 Buffer b; 143 Options options; 144 Key *keys[2], *key; 145 struct passwd *pw; 146 int key_fd[2], i, found, version = 2, fd; 147 u_char *signature, *data; 148 char *host; 149 u_int slen, dlen; 150 u_int32_t rnd[256]; 151 152 key_fd[0] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY); 153 key_fd[1] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY); 154 155 seteuid(getuid()); 156 setuid(getuid()); 157 158 init_rng(); 159 seed_rng(); 160 arc4random_stir(); 161 162 #ifdef DEBUG_SSH_KEYSIGN 163 log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0); 164 #endif 165 166 /* verify that ssh-keysign is enabled by the admin */ 167 original_real_uid = getuid(); /* XXX readconf.c needs this */ 168 initialize_options(&options); 169 (void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options); 170 fill_default_options(&options); 171 if (options.enable_ssh_keysign != 1) 172 fatal("ssh-keysign not enabled in %s", 173 _PATH_HOST_CONFIG_FILE); 174 175 if (key_fd[0] == -1 && key_fd[1] == -1) 176 fatal("could not open any host key"); 177 178 if ((pw = getpwuid(getuid())) == NULL) 179 fatal("getpwuid failed"); 180 pw = pwcopy(pw); 181 182 SSLeay_add_all_algorithms(); 183 for (i = 0; i < 256; i++) 184 rnd[i] = arc4random(); 185 RAND_seed(rnd, sizeof(rnd)); 186 187 found = 0; 188 for (i = 0; i < 2; i++) { 189 keys[i] = NULL; 190 if (key_fd[i] == -1) 191 continue; 192 keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC, 193 NULL, NULL); 194 close(key_fd[i]); 195 if (keys[i] != NULL) 196 found = 1; 197 } 198 if (!found) 199 fatal("no hostkey found"); 200 201 buffer_init(&b); 202 if (ssh_msg_recv(STDIN_FILENO, &b) < 0) 203 fatal("ssh_msg_recv failed"); 204 if (buffer_get_char(&b) != version) 205 fatal("bad version"); 206 fd = buffer_get_int(&b); 207 if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO)) 208 fatal("bad fd"); 209 if ((host = get_local_name(fd)) == NULL) 210 fatal("cannot get sockname for fd"); 211 212 data = buffer_get_string(&b, &dlen); 213 if (valid_request(pw, host, &key, data, dlen) < 0) 214 fatal("not a valid request"); 215 xfree(host); 216 217 found = 0; 218 for (i = 0; i < 2; i++) { 219 if (keys[i] != NULL && 220 key_equal(key, keys[i])) { 221 found = 1; 222 break; 223 } 224 } 225 if (!found) 226 fatal("no matching hostkey found"); 227 228 if (key_sign(keys[i], &signature, &slen, data, dlen) != 0) 229 fatal("key_sign failed"); 230 xfree(data); 231 232 /* send reply */ 233 buffer_clear(&b); 234 buffer_put_string(&b, signature, slen); 235 ssh_msg_send(STDOUT_FILENO, version, &b); 236 237 return (0); 238 } 239