1 /* $OpenBSD: ssh-keysign.c,v 1.43 2014/10/08 22:20:25 djm Exp $ */ 2 /* 3 * Copyright (c) 2002 Markus Friedl. All rights reserved. 4 * 5 * Redistribution and use in source and binary forms, with or without 6 * modification, are permitted provided that the following conditions 7 * are met: 8 * 1. Redistributions of source code must retain the above copyright 9 * notice, this list of conditions and the following disclaimer. 10 * 2. Redistributions in binary form must reproduce the above copyright 11 * notice, this list of conditions and the following disclaimer in the 12 * documentation and/or other materials provided with the distribution. 13 * 14 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 15 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 16 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 17 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 18 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 19 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 20 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 21 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 22 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 23 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 24 */ 25 26 #include <sys/types.h> 27 28 #include <openssl/evp.h> 29 #include <openssl/rsa.h> 30 31 #include <fcntl.h> 32 #include <paths.h> 33 #include <pwd.h> 34 #include <stdlib.h> 35 #include <string.h> 36 #include <unistd.h> 37 38 #include "xmalloc.h" 39 #include "log.h" 40 #include "key.h" 41 #include "ssh.h" 42 #include "ssh2.h" 43 #include "misc.h" 44 #include "buffer.h" 45 #include "authfile.h" 46 #include "msg.h" 47 #include "canohost.h" 48 #include "pathnames.h" 49 #include "readconf.h" 50 #include "uidswap.h" 51 52 /* XXX readconf.c needs these */ 53 uid_t original_real_uid; 54 55 static int 56 valid_request(struct passwd *pw, char *host, Key **ret, u_char *data, 57 u_int datalen) 58 { 59 Buffer b; 60 Key *key = NULL; 61 u_char *pkblob; 62 u_int blen, len; 63 char *pkalg, *p; 64 int pktype, fail; 65 66 fail = 0; 67 68 buffer_init(&b); 69 buffer_append(&b, data, datalen); 70 71 /* session id, currently limited to SHA1 (20 bytes) or SHA256 (32) */ 72 p = buffer_get_string(&b, &len); 73 if (len != 20 && len != 32) 74 fail++; 75 free(p); 76 77 if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST) 78 fail++; 79 80 /* server user */ 81 buffer_skip_string(&b); 82 83 /* service */ 84 p = buffer_get_string(&b, NULL); 85 if (strcmp("ssh-connection", p) != 0) 86 fail++; 87 free(p); 88 89 /* method */ 90 p = buffer_get_string(&b, NULL); 91 if (strcmp("hostbased", p) != 0) 92 fail++; 93 free(p); 94 95 /* pubkey */ 96 pkalg = buffer_get_string(&b, NULL); 97 pkblob = buffer_get_string(&b, &blen); 98 99 pktype = key_type_from_name(pkalg); 100 if (pktype == KEY_UNSPEC) 101 fail++; 102 else if ((key = key_from_blob(pkblob, blen)) == NULL) 103 fail++; 104 else if (key->type != pktype) 105 fail++; 106 free(pkalg); 107 free(pkblob); 108 109 /* client host name, handle trailing dot */ 110 p = buffer_get_string(&b, &len); 111 debug2("valid_request: check expect chost %s got %s", host, p); 112 if (strlen(host) != len - 1) 113 fail++; 114 else if (p[len - 1] != '.') 115 fail++; 116 else if (strncasecmp(host, p, len - 1) != 0) 117 fail++; 118 free(p); 119 120 /* local user */ 121 p = buffer_get_string(&b, NULL); 122 123 if (strcmp(pw->pw_name, p) != 0) 124 fail++; 125 free(p); 126 127 /* end of message */ 128 if (buffer_len(&b) != 0) 129 fail++; 130 buffer_free(&b); 131 132 debug3("valid_request: fail %d", fail); 133 134 if (fail && key != NULL) 135 key_free(key); 136 else 137 *ret = key; 138 139 return (fail ? -1 : 0); 140 } 141 142 int 143 main(int argc, char **argv) 144 { 145 Buffer b; 146 Options options; 147 #define NUM_KEYTYPES 4 148 Key *keys[NUM_KEYTYPES], *key = NULL; 149 struct passwd *pw; 150 int key_fd[NUM_KEYTYPES], i, found, version = 2, fd; 151 u_char *signature, *data; 152 char *host, *fp; 153 u_int slen, dlen; 154 155 /* Ensure that stdin and stdout are connected */ 156 if ((fd = open(_PATH_DEVNULL, O_RDWR)) < 2) 157 exit(1); 158 /* Leave /dev/null fd iff it is attached to stderr */ 159 if (fd > 2) 160 close(fd); 161 162 i = 0; 163 key_fd[i++] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY); 164 key_fd[i++] = open(_PATH_HOST_ECDSA_KEY_FILE, O_RDONLY); 165 key_fd[i++] = open(_PATH_HOST_ED25519_KEY_FILE, O_RDONLY); 166 key_fd[i++] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY); 167 168 original_real_uid = getuid(); /* XXX readconf.c needs this */ 169 if ((pw = getpwuid(original_real_uid)) == NULL) 170 fatal("getpwuid failed"); 171 pw = pwcopy(pw); 172 173 permanently_set_uid(pw); 174 175 #ifdef DEBUG_SSH_KEYSIGN 176 log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0); 177 #endif 178 179 /* verify that ssh-keysign is enabled by the admin */ 180 initialize_options(&options); 181 (void)read_config_file(_PATH_HOST_CONFIG_FILE, pw, "", "", &options, 0); 182 fill_default_options(&options); 183 if (options.enable_ssh_keysign != 1) 184 fatal("ssh-keysign not enabled in %s", 185 _PATH_HOST_CONFIG_FILE); 186 187 for (i = found = 0; i < NUM_KEYTYPES; i++) { 188 if (key_fd[i] != -1) 189 found = 1; 190 } 191 if (found == 0) 192 fatal("could not open any host key"); 193 194 OpenSSL_add_all_algorithms(); 195 196 found = 0; 197 for (i = 0; i < NUM_KEYTYPES; i++) { 198 keys[i] = NULL; 199 if (key_fd[i] == -1) 200 continue; 201 #ifdef WITH_OPENSSL 202 /* XXX wrong api */ 203 keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC, 204 NULL, NULL); 205 #endif 206 close(key_fd[i]); 207 if (keys[i] != NULL) 208 found = 1; 209 } 210 if (!found) 211 fatal("no hostkey found"); 212 213 buffer_init(&b); 214 if (ssh_msg_recv(STDIN_FILENO, &b) < 0) 215 fatal("ssh_msg_recv failed"); 216 if (buffer_get_char(&b) != version) 217 fatal("bad version"); 218 fd = buffer_get_int(&b); 219 if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO)) 220 fatal("bad fd"); 221 if ((host = get_local_name(fd)) == NULL) 222 fatal("cannot get local name for fd"); 223 224 data = buffer_get_string(&b, &dlen); 225 if (valid_request(pw, host, &key, data, dlen) < 0) 226 fatal("not a valid request"); 227 free(host); 228 229 found = 0; 230 for (i = 0; i < NUM_KEYTYPES; i++) { 231 if (keys[i] != NULL && 232 key_equal_public(key, keys[i])) { 233 found = 1; 234 break; 235 } 236 } 237 if (!found) { 238 fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX); 239 fatal("no matching hostkey found for key %s %s", 240 key_type(key), fp); 241 } 242 243 if (key_sign(keys[i], &signature, &slen, data, dlen) != 0) 244 fatal("key_sign failed"); 245 free(data); 246 247 /* send reply */ 248 buffer_clear(&b); 249 buffer_put_string(&b, signature, slen); 250 if (ssh_msg_send(STDOUT_FILENO, version, &b) == -1) 251 fatal("ssh_msg_send failed"); 252 253 return (0); 254 } 255