1/* $OpenBSD: ssh-keysign.c,v 1.36 2011/02/16 00:31:14 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 "includes.h" 27 28#include <fcntl.h> 29#ifdef HAVE_PATHS_H 30#include <paths.h> 31#endif 32#include <pwd.h> 33#include <stdarg.h> 34#include <stdlib.h> 35#include <string.h> 36#include <unistd.h> 37 38#ifdef __APPLE_CRYPTO__ 39#include "ossl-evp.h" 40#include "ossl-rand.h" 41#include "ossl-rsa.h" 42#else 43#include <openssl/evp.h> 44#include <openssl/rand.h> 45#include <openssl/rsa.h> 46#endif 47 48#include "xmalloc.h" 49#include "log.h" 50#include "key.h" 51#include "ssh.h" 52#include "ssh2.h" 53#include "misc.h" 54#include "buffer.h" 55#include "authfile.h" 56#include "msg.h" 57#include "canohost.h" 58#include "pathnames.h" 59#include "readconf.h" 60#include "uidswap.h" 61 62/* XXX readconf.c needs these */ 63uid_t original_real_uid; 64 65extern char *__progname; 66 67static int 68valid_request(struct passwd *pw, char *host, Key **ret, u_char *data, 69 u_int datalen) 70{ 71 Buffer b; 72 Key *key = NULL; 73 u_char *pkblob; 74 u_int blen, len; 75 char *pkalg, *p; 76 int pktype, fail; 77 78 fail = 0; 79 80 buffer_init(&b); 81 buffer_append(&b, data, datalen); 82 83 /* session id, currently limited to SHA1 (20 bytes) or SHA256 (32) */ 84 p = buffer_get_string(&b, &len); 85 if (len != 20 && len != 32) 86 fail++; 87 xfree(p); 88 89 if (buffer_get_char(&b) != SSH2_MSG_USERAUTH_REQUEST) 90 fail++; 91 92 /* server user */ 93 buffer_skip_string(&b); 94 95 /* service */ 96 p = buffer_get_string(&b, NULL); 97 if (strcmp("ssh-connection", p) != 0) 98 fail++; 99 xfree(p); 100 101 /* method */ 102 p = buffer_get_string(&b, NULL); 103 if (strcmp("hostbased", p) != 0) 104 fail++; 105 xfree(p); 106 107 /* pubkey */ 108 pkalg = buffer_get_string(&b, NULL); 109 pkblob = buffer_get_string(&b, &blen); 110 111 pktype = key_type_from_name(pkalg); 112 if (pktype == KEY_UNSPEC) 113 fail++; 114 else if ((key = key_from_blob(pkblob, blen)) == NULL) 115 fail++; 116 else if (key->type != pktype) 117 fail++; 118 xfree(pkalg); 119 xfree(pkblob); 120 121 /* client host name, handle trailing dot */ 122 p = buffer_get_string(&b, &len); 123 debug2("valid_request: check expect chost %s got %s", host, p); 124 if (strlen(host) != len - 1) 125 fail++; 126 else if (p[len - 1] != '.') 127 fail++; 128 else if (strncasecmp(host, p, len - 1) != 0) 129 fail++; 130 xfree(p); 131 132 /* local user */ 133 p = buffer_get_string(&b, NULL); 134 135 if (strcmp(pw->pw_name, p) != 0) 136 fail++; 137 xfree(p); 138 139 /* end of message */ 140 if (buffer_len(&b) != 0) 141 fail++; 142 buffer_free(&b); 143 144 debug3("valid_request: fail %d", fail); 145 146 if (fail && key != NULL) 147 key_free(key); 148 else 149 *ret = key; 150 151 return (fail ? -1 : 0); 152} 153 154int 155main(int argc, char **argv) 156{ 157 Buffer b; 158 Options options; 159#define NUM_KEYTYPES 3 160 Key *keys[NUM_KEYTYPES], *key = NULL; 161 struct passwd *pw; 162 int key_fd[NUM_KEYTYPES], i, found, version = 2, fd; 163 u_char *signature, *data; 164 char *host; 165 u_int slen, dlen; 166 u_int32_t rnd[256]; 167 168 /* Ensure that stdin and stdout are connected */ 169 if ((fd = open(_PATH_DEVNULL, O_RDWR)) < 2) 170 exit(1); 171 /* Leave /dev/null fd iff it is attached to stderr */ 172 if (fd > 2) 173 close(fd); 174 175 i = 0; 176 key_fd[i++] = open(_PATH_HOST_DSA_KEY_FILE, O_RDONLY); 177 key_fd[i++] = open(_PATH_HOST_ECDSA_KEY_FILE, O_RDONLY); 178 key_fd[i++] = open(_PATH_HOST_RSA_KEY_FILE, O_RDONLY); 179 180 original_real_uid = getuid(); /* XXX readconf.c needs this */ 181 if ((pw = getpwuid(original_real_uid)) == NULL) 182 fatal("getpwuid failed"); 183 pw = pwcopy(pw); 184 185 permanently_set_uid(pw); 186 187 seed_rng(); 188 arc4random_stir(); 189 190#ifdef DEBUG_SSH_KEYSIGN 191 log_init("ssh-keysign", SYSLOG_LEVEL_DEBUG3, SYSLOG_FACILITY_AUTH, 0); 192#endif 193 194 /* verify that ssh-keysign is enabled by the admin */ 195 initialize_options(&options); 196 (void)read_config_file(_PATH_HOST_CONFIG_FILE, "", &options, 0); 197 fill_default_options(&options); 198 if (options.enable_ssh_keysign != 1) 199 fatal("ssh-keysign not enabled in %s", 200 _PATH_HOST_CONFIG_FILE); 201 202 for (i = found = 0; i < NUM_KEYTYPES; i++) { 203 if (key_fd[i] != -1) 204 found = 1; 205 } 206 if (found == 0) 207 fatal("could not open any host key"); 208 209 OpenSSL_add_all_algorithms(); 210 for (i = 0; i < 256; i++) 211 rnd[i] = arc4random(); 212 RAND_seed(rnd, sizeof(rnd)); 213 214 found = 0; 215 for (i = 0; i < NUM_KEYTYPES; i++) { 216 keys[i] = NULL; 217 if (key_fd[i] == -1) 218 continue; 219 keys[i] = key_load_private_pem(key_fd[i], KEY_UNSPEC, 220 NULL, NULL); 221 close(key_fd[i]); 222 if (keys[i] != NULL) 223 found = 1; 224 } 225 if (!found) 226 fatal("no hostkey found"); 227 228 buffer_init(&b); 229 if (ssh_msg_recv(STDIN_FILENO, &b) < 0) 230 fatal("ssh_msg_recv failed"); 231 if (buffer_get_char(&b) != version) 232 fatal("bad version"); 233 fd = buffer_get_int(&b); 234 if ((fd == STDIN_FILENO) || (fd == STDOUT_FILENO)) 235 fatal("bad fd"); 236 if ((host = get_local_name(fd)) == NULL) 237 fatal("cannot get local name for fd"); 238 239 data = buffer_get_string(&b, &dlen); 240 if (valid_request(pw, host, &key, data, dlen) < 0) 241 fatal("not a valid request"); 242 xfree(host); 243 244 found = 0; 245 for (i = 0; i < NUM_KEYTYPES; i++) { 246 if (keys[i] != NULL && 247 key_equal_public(key, keys[i])) { 248 found = 1; 249 break; 250 } 251 } 252 if (!found) 253 fatal("no matching hostkey found"); 254 255 if (key_sign(keys[i], &signature, &slen, data, dlen) != 0) 256 fatal("key_sign failed"); 257 xfree(data); 258 259 /* send reply */ 260 buffer_clear(&b); 261 buffer_put_string(&b, signature, slen); 262 if (ssh_msg_send(STDOUT_FILENO, version, &b) == -1) 263 fatal("ssh_msg_send failed"); 264 265 return (0); 266} 267