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 1.16 2004/04/18 23:10:26 djm 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 #include "uidswap.h" 45 46 /* XXX readconf.c needs these */ 47 uid_t original_real_uid; 48 49 extern char *__progname; 50 51 static int 52 valid_request(struct passwd *pw, char *host, Key **ret, u_char *data, 53 u_int datalen) 54 { 55 Buffer b; 56 Key *key = NULL; 57 u_char *pkblob; 58 u_int blen, len; 59 char *pkalg, *p; 60 int pktype, fail; 61 62 fail = 0; 63 64 buffer_init(&b); 65 buffer_append(&b, data, datalen); 66 67 /* session id, currently limited to SHA1 (20 bytes) */ 68 p = buffer_get_string(&b, &len); 69 if (len != 20) 70 fail++; 71 xfree(p); 72 73 if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST) 74 fail++; 75 76 /* server user */ 77 buffer_skip_string(&b); 78 79 /* service */ 80 p = buffer_get_string(&b, NULL); 81 if (strcmp("ssh-connection", p) != 0) 82 fail++; 83 xfree(p); 84 85 /* method */ 86 p = buffer_get_string(&b, NULL); 87 if (strcmp("hostbased", p) != 0) 88 fail++; 89 xfree(p); 90 91 /* pubkey */ 92 pkalg = buffer_get_string(&b, NULL); 93 pkblob = buffer_get_string(&b, &blen); 94 95 pktype = key_type_from_name(pkalg); 96 if (pktype == KEY_UNSPEC) 97 fail++; 98 else if ((key = key_from_blob(pkblob, blen)) == NULL) 99 fail++; 100 else if (key->type != pktype) 101 fail++; 102 xfree(pkalg); 103 xfree(pkblob); 104 105 /* client host name, handle trailing dot */ 106 p = buffer_get_string(&b, &len); 107 debug2("valid_request: check expect chost %s got %s", host, p); 108 if (strlen(host) != len - 1) 109 fail++; 110 else if (p[len - 1] != '.') 111 fail++; 112 else if (strncasecmp(host, p, len - 1) != 0) 113 fail++; 114 xfree(p); 115 116 /* local user */ 117 p = buffer_get_string(&b, NULL); 118 119 if (strcmp(pw->pw_name, p) != 0) 120 fail++; 121 xfree(p); 122 123 /* end of message */ 124 if (buffer_len(&b) != 0) 125 fail++; 126 buffer_free(&b); 127 128 debug3("valid_request: fail %d", fail); 129 130 if (fail && key != NULL) 131 key_free(key); 132 else 133 *ret = key; 134 135 return (fail ? -1 : 0); 136 } 137 138 int 139 main(int argc, char **argv) 140 { 141 Buffer b; 142 Options options; 143 Key *keys[2], *key; 144 struct passwd *pw; 145 int key_fd[2], i, found, version = 2, fd; 146 u_char *signature, *data; 147 char *host; 148 u_int slen, dlen; 149 u_int32_t rnd[256]; 150 151 key_fd[0] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY); 152 key_fd[1] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY); 153 154 if ((pw = getpwuid(getuid())) == NULL) 155 fatal("getpwuid failed"); 156 pw = pwcopy(pw); 157 158 permanently_set_uid(pw); 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, 0); 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 SSLeay_add_all_algorithms(); 181 for (i = 0; i < 256; i++) 182 rnd[i] = arc4random(); 183 RAND_seed(rnd, sizeof(rnd)); 184 185 found = 0; 186 for (i = 0; i < 2; i++) { 187 keys[i] = NULL; 188 if (key_fd[i] == -1) 189 continue; 190 keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC, 191 NULL, NULL); 192 close(key_fd[i]); 193 if (keys[i] != NULL) 194 found = 1; 195 } 196 if (!found) 197 fatal("no hostkey found"); 198 199 buffer_init(&b); 200 if (ssh_msg_recv(STDIN_FILENO, &b) < 0) 201 fatal("ssh_msg_recv failed"); 202 if (buffer_get_char(&b) != version) 203 fatal("bad version"); 204 fd = buffer_get_int(&b); 205 if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO)) 206 fatal("bad fd"); 207 if ((host = get_local_name(fd)) == NULL) 208 fatal("cannot get sockname for fd"); 209 210 data = buffer_get_string(&b, &dlen); 211 if (valid_request(pw, host, &key, data, dlen) < 0) 212 fatal("not a valid request"); 213 xfree(host); 214 215 found = 0; 216 for (i = 0; i < 2; i++) { 217 if (keys[i] != NULL && 218 key_equal(key, keys[i])) { 219 found = 1; 220 break; 221 } 222 } 223 if (!found) 224 fatal("no matching hostkey found"); 225 226 if (key_sign(keys[i], &signature, &slen, data, dlen) != 0) 227 fatal("key_sign failed"); 228 xfree(data); 229 230 /* send reply */ 231 buffer_clear(&b); 232 buffer_put_string(&b, signature, slen); 233 if (ssh_msg_send(STDOUT_FILENO, version, &b) == -1) 234 fatal("ssh_msg_send failed"); 235 236 return (0); 237 } 238