1 /* $NetBSD: ssh-keysign.c,v 1.2 2009/06/07 22:38:47 christos Exp $ */ 2 /* $OpenBSD: ssh-keysign.c,v 1.29 2006/08/03 03:34:42 deraadt Exp $ */ 3 /* 4 * Copyright (c) 2002 Markus Friedl. All rights reserved. 5 * 6 * Redistribution and use in source and binary forms, with or without 7 * modification, are permitted provided that the following conditions 8 * are met: 9 * 1. Redistributions of source code must retain the above copyright 10 * notice, this list of conditions and the following disclaimer. 11 * 2. Redistributions in binary form must reproduce the above copyright 12 * notice, this list of conditions and the following disclaimer in the 13 * documentation and/or other materials provided with the distribution. 14 * 15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 25 */ 26 27 #include "includes.h" 28 __RCSID("$NetBSD: ssh-keysign.c,v 1.2 2009/06/07 22:38:47 christos Exp $"); 29 #include <sys/types.h> 30 31 #include <openssl/evp.h> 32 #include <openssl/rand.h> 33 #include <openssl/rsa.h> 34 35 #include <fcntl.h> 36 #include <paths.h> 37 #include <pwd.h> 38 #include <stdlib.h> 39 #include <string.h> 40 #include <unistd.h> 41 42 #include "xmalloc.h" 43 #include "log.h" 44 #include "key.h" 45 #include "ssh.h" 46 #include "ssh2.h" 47 #include "misc.h" 48 #include "buffer.h" 49 #include "authfile.h" 50 #include "msg.h" 51 #include "canohost.h" 52 #include "pathnames.h" 53 #include "readconf.h" 54 #include "uidswap.h" 55 56 /* XXX readconf.c needs these */ 57 uid_t original_real_uid; 58 59 static int 60 valid_request(struct passwd *pw, char *host, Key **ret, u_char *data, 61 u_int datalen) 62 { 63 Buffer b; 64 Key *key = NULL; 65 u_char *pkblob; 66 u_int blen, len; 67 char *pkalg, *p; 68 int pktype, fail; 69 70 fail = 0; 71 72 buffer_init(&b); 73 buffer_append(&b, data, datalen); 74 75 /* session id, currently limited to SHA1 (20 bytes) or SHA256 (32) */ 76 p = buffer_get_string(&b, &len); 77 if (len != 20 && len != 32) 78 fail++; 79 xfree(p); 80 81 if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST) 82 fail++; 83 84 /* server user */ 85 buffer_skip_string(&b); 86 87 /* service */ 88 p = buffer_get_string(&b, NULL); 89 if (strcmp("ssh-connection", p) != 0) 90 fail++; 91 xfree(p); 92 93 /* method */ 94 p = buffer_get_string(&b, NULL); 95 if (strcmp("hostbased", p) != 0) 96 fail++; 97 xfree(p); 98 99 /* pubkey */ 100 pkalg = buffer_get_string(&b, NULL); 101 pkblob = buffer_get_string(&b, &blen); 102 103 pktype = key_type_from_name(pkalg); 104 if (pktype == KEY_UNSPEC) 105 fail++; 106 else if ((key = key_from_blob(pkblob, blen)) == NULL) 107 fail++; 108 else if (key->type != pktype) 109 fail++; 110 xfree(pkalg); 111 xfree(pkblob); 112 113 /* client host name, handle trailing dot */ 114 p = buffer_get_string(&b, &len); 115 debug2("valid_request: check expect chost %s got %s", host, p); 116 if (strlen(host) != len - 1) 117 fail++; 118 else if (p[len - 1] != '.') 119 fail++; 120 else if (strncasecmp(host, p, len - 1) != 0) 121 fail++; 122 xfree(p); 123 124 /* local user */ 125 p = buffer_get_string(&b, NULL); 126 127 if (strcmp(pw->pw_name, p) != 0) 128 fail++; 129 xfree(p); 130 131 /* end of message */ 132 if (buffer_len(&b) != 0) 133 fail++; 134 buffer_free(&b); 135 136 debug3("valid_request: fail %d", fail); 137 138 if (fail && key != NULL) 139 key_free(key); 140 else 141 *ret = key; 142 143 return (fail ? -1 : 0); 144 } 145 146 int 147 main(int argc, char **argv) 148 { 149 Buffer b; 150 Options options; 151 Key *keys[2], *key; 152 struct passwd *pw; 153 int key_fd[2], i, found, version = 2, fd; 154 u_char *signature, *data; 155 char *host; 156 u_int slen, dlen; 157 u_int32_t rnd[256]; 158 159 key = NULL; /* XXX gcc */ 160 161 /* Ensure that stdin and stdout are connected */ 162 if ((fd = open(_PATH_DEVNULL, O_RDWR)) < 2) 163 exit(1); 164 /* Leave /dev/null fd iff it is attached to stderr */ 165 if (fd > 2) 166 close(fd); 167 168 key_fd[0] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY); 169 key_fd[1] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY); 170 171 original_real_uid = getuid(); /* XXX readconf.c needs this */ 172 if ((pw = getpwuid(original_real_uid)) == NULL) 173 fatal("getpwuid failed"); 174 pw = pwcopy(pw); 175 176 permanently_set_uid(pw); 177 178 #ifdef DEBUG_SSH_KEYSIGN 179 log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0); 180 #endif 181 182 /* verify that ssh-keysign is enabled by the admin */ 183 initialize_options(&options); 184 (void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options, 0); 185 fill_default_options(&options); 186 if (options.enable_ssh_keysign != 1) 187 fatal("ssh-keysign not enabled in %s", 188 _PATH_HOST_CONFIG_FILE); 189 190 if (key_fd[0] == -1 && key_fd[1] == -1) 191 fatal("could not open any host key"); 192 193 SSLeay_add_all_algorithms(); 194 for (i = 0; i < 256; i++) 195 rnd[i] = arc4random(); 196 RAND_seed(rnd, sizeof(rnd)); 197 198 found = 0; 199 for (i = 0; i < 2; i++) { 200 keys[i] = NULL; 201 if (key_fd[i] == -1) 202 continue; 203 keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC, 204 NULL, NULL); 205 close(key_fd[i]); 206 if (keys[i] != NULL) 207 found = 1; 208 } 209 if (!found) 210 fatal("no hostkey found"); 211 212 buffer_init(&b); 213 if (ssh_msg_recv(STDIN_FILENO, &b) < 0) 214 fatal("ssh_msg_recv failed"); 215 if (buffer_get_char(&b) != version) 216 fatal("bad version"); 217 fd = buffer_get_int(&b); 218 if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO)) 219 fatal("bad fd"); 220 if ((host = get_local_name(fd)) == NULL) 221 fatal("cannot get sockname for fd"); 222 223 data = buffer_get_string(&b, &dlen); 224 if (valid_request(pw, host, &key, data, dlen) < 0) 225 fatal("not a valid request"); 226 xfree(host); 227 228 found = 0; 229 for (i = 0; i < 2; i++) { 230 if (keys[i] != NULL && 231 key_equal(key, keys[i])) { 232 found = 1; 233 break; 234 } 235 } 236 if (!found) 237 fatal("no matching hostkey found"); 238 239 if (key_sign(keys[i], &signature, &slen, data, dlen) != 0) 240 fatal("key_sign failed"); 241 xfree(data); 242 243 /* send reply */ 244 buffer_clear(&b); 245 buffer_put_string(&b, signature, slen); 246 if (ssh_msg_send(STDOUT_FILENO, version, &b) == -1) 247 fatal("ssh_msg_send failed"); 248 249 return (0); 250 } 251