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 1.18 2004/08/23 14:29:23 dtucker 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 static int 50 valid_request(struct passwd *pw, char *host, Key **ret, u_char *data, 51 u_int datalen) 52 { 53 Buffer b; 54 Key *key = NULL; 55 u_char *pkblob; 56 u_int blen, len; 57 char *pkalg, *p; 58 int pktype, fail; 59 60 fail = 0; 61 62 buffer_init(&b); 63 buffer_append(&b, data, datalen); 64 65 /* session id, currently limited to SHA1 (20 bytes) */ 66 p = buffer_get_string(&b, &len); 67 if (len != 20) 68 fail++; 69 xfree(p); 70 71 if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST) 72 fail++; 73 74 /* server user */ 75 buffer_skip_string(&b); 76 77 /* service */ 78 p = buffer_get_string(&b, NULL); 79 if (strcmp("ssh-connection", p) != 0) 80 fail++; 81 xfree(p); 82 83 /* method */ 84 p = buffer_get_string(&b, NULL); 85 if (strcmp("hostbased", p) != 0) 86 fail++; 87 xfree(p); 88 89 /* pubkey */ 90 pkalg = buffer_get_string(&b, NULL); 91 pkblob = buffer_get_string(&b, &blen); 92 93 pktype = key_type_from_name(pkalg); 94 if (pktype == KEY_UNSPEC) 95 fail++; 96 else if ((key = key_from_blob(pkblob, blen)) == NULL) 97 fail++; 98 else if (key->type != pktype) 99 fail++; 100 xfree(pkalg); 101 xfree(pkblob); 102 103 /* client host name, handle trailing dot */ 104 p = buffer_get_string(&b, &len); 105 debug2("valid_request: check expect chost %s got %s", host, p); 106 if (strlen(host) != len - 1) 107 fail++; 108 else if (p[len - 1] != '.') 109 fail++; 110 else if (strncasecmp(host, p, len - 1) != 0) 111 fail++; 112 xfree(p); 113 114 /* local user */ 115 p = buffer_get_string(&b, NULL); 116 117 if (strcmp(pw->pw_name, p) != 0) 118 fail++; 119 xfree(p); 120 121 /* end of message */ 122 if (buffer_len(&b) != 0) 123 fail++; 124 buffer_free(&b); 125 126 debug3("valid_request: fail %d", fail); 127 128 if (fail && key != NULL) 129 key_free(key); 130 else 131 *ret = key; 132 133 return (fail ? -1 : 0); 134 } 135 136 int 137 main(int argc, char **argv) 138 { 139 Buffer b; 140 Options options; 141 Key *keys[2], *key; 142 struct passwd *pw; 143 int key_fd[2], i, found, version = 2, fd; 144 u_char *signature, *data; 145 char *host; 146 u_int slen, dlen; 147 u_int32_t rnd[256]; 148 149 key_fd[0] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY); 150 key_fd[1] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY); 151 152 original_real_uid = getuid(); /* XXX readconf.c needs this */ 153 if ((pw = getpwuid(original_real_uid)) == NULL) 154 fatal("getpwuid failed"); 155 pw = pwcopy(pw); 156 157 permanently_set_uid(pw); 158 159 #ifdef DEBUG_SSH_KEYSIGN 160 log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0); 161 #endif 162 163 /* verify that ssh-keysign is enabled by the admin */ 164 initialize_options(&options); 165 (void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options, 0); 166 fill_default_options(&options); 167 if (options.enable_ssh_keysign != 1) 168 fatal("ssh-keysign not enabled in %s", 169 _PATH_HOST_CONFIG_FILE); 170 171 if (key_fd[0] == -1 && key_fd[1] == -1) 172 fatal("could not open any host key"); 173 174 SSLeay_add_all_algorithms(); 175 for (i = 0; i < 256; i++) 176 rnd[i] = arc4random(); 177 RAND_seed(rnd, sizeof(rnd)); 178 179 found = 0; 180 for (i = 0; i < 2; i++) { 181 keys[i] = NULL; 182 if (key_fd[i] == -1) 183 continue; 184 keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC, 185 NULL, NULL); 186 close(key_fd[i]); 187 if (keys[i] != NULL) 188 found = 1; 189 } 190 if (!found) 191 fatal("no hostkey found"); 192 193 buffer_init(&b); 194 if (ssh_msg_recv(STDIN_FILENO, &b) < 0) 195 fatal("ssh_msg_recv failed"); 196 if (buffer_get_char(&b) != version) 197 fatal("bad version"); 198 fd = buffer_get_int(&b); 199 if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO)) 200 fatal("bad fd"); 201 if ((host = get_local_name(fd)) == NULL) 202 fatal("cannot get sockname for fd"); 203 204 data = buffer_get_string(&b, &dlen); 205 if (valid_request(pw, host, &key, data, dlen) < 0) 206 fatal("not a valid request"); 207 xfree(host); 208 209 found = 0; 210 for (i = 0; i < 2; i++) { 211 if (keys[i] != NULL && 212 key_equal(key, keys[i])) { 213 found = 1; 214 break; 215 } 216 } 217 if (!found) 218 fatal("no matching hostkey found"); 219 220 if (key_sign(keys[i], &signature, &slen, data, dlen) != 0) 221 fatal("key_sign failed"); 222 xfree(data); 223 224 /* send reply */ 225 buffer_clear(&b); 226 buffer_put_string(&b, signature, slen); 227 if (ssh_msg_send(STDOUT_FILENO, version, &b) == -1) 228 fatal("ssh_msg_send failed"); 229 230 return (0); 231 } 232