1 /*
2 * Dropbear - a SSH2 server
3 *
4 * Copyright (c) 2002-2006 Matt Johnston
5 * All rights reserved.
6 *
7 * Permission is hereby granted, free of charge, to any person obtaining a copy
8 * of this software and associated documentation files (the "Software"), to deal
9 * in the Software without restriction, including without limitation the rights
10 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
11 * copies of the Software, and to permit persons to whom the Software is
12 * furnished to do so, subject to the following conditions:
13 *
14 * The above copyright notice and this permission notice shall be included in
15 * all copies or substantial portions of the Software.
16 *
17 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
18 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
19 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
20 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
21 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
22 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
23 * SOFTWARE. */
24
25 #include "includes.h"
26 #include "dbutil.h"
27 #include "session.h"
28 #include "buffer.h"
29 #include "signkey.h"
30 #include "runopts.h"
31 #include "random.h"
32
33 static size_t listensockets(int *sock, size_t sockcount, int *maxfd);
34 static void sigchld_handler(int dummy);
35 static void sigsegv_handler(int);
36 static void sigintterm_handler(int fish);
37 #ifdef INETD_MODE
38 static void main_inetd();
39 #endif
40 #ifdef NON_INETD_MODE
41 static void main_noinetd();
42 #endif
43 static void commonsetup();
44
45 #if defined(DBMULTI_dropbear) || !defined(DROPBEAR_MULTI)
46 #if defined(DBMULTI_dropbear) && defined(DROPBEAR_MULTI)
dropbear_main(int argc,char ** argv)47 int dropbear_main(int argc, char ** argv)
48 #else
49 int main(int argc, char ** argv)
50 #endif
51 {
52 _dropbear_exit = svr_dropbear_exit;
53 _dropbear_log = svr_dropbear_log;
54
55 disallow_core();
56
57 /* get commandline options */
58 svr_getopts(argc, argv);
59
60 #ifdef INETD_MODE
61 /* service program mode */
62 if (svr_opts.inetdmode) {
63 main_inetd();
64 /* notreached */
65 }
66 #endif
67
68 #ifdef NON_INETD_MODE
69 main_noinetd();
70 /* notreached */
71 #endif
72
73 dropbear_exit("Compiled without normal mode, can't run without -i\n");
74 return -1;
75 }
76 #endif
77
78 #ifdef INETD_MODE
main_inetd()79 static void main_inetd() {
80
81 struct sockaddr_storage remoteaddr;
82 socklen_t remoteaddrlen;
83 char * addrstring = NULL;
84
85 /* Set up handlers, syslog, seed random */
86 commonsetup();
87
88 remoteaddrlen = sizeof(remoteaddr);
89 if (getpeername(0, (struct sockaddr*)&remoteaddr, &remoteaddrlen) < 0) {
90 dropbear_exit("Unable to getpeername: %s", strerror(errno));
91 }
92
93 /* In case our inetd was lax in logging source addresses */
94 addrstring = getaddrstring(&remoteaddr, 1);
95 dropbear_log(LOG_INFO, "Child connection from %s", addrstring);
96
97 /* Don't check the return value - it may just fail since inetd has
98 * already done setsid() after forking (xinetd on Darwin appears to do
99 * this */
100 setsid();
101
102 /* Start service program
103 * -1 is a dummy childpipe, just something we can close() without
104 * mattering. */
105 svr_session(0, -1, getaddrhostname(&remoteaddr), addrstring);
106
107 /* notreached */
108 }
109 #endif /* INETD_MODE */
110
111 #ifdef NON_INETD_MODE
main_noinetd()112 void main_noinetd() {
113 fd_set fds;
114 struct timeval seltimeout;
115 unsigned int i, j;
116 int val;
117 int maxsock = -1;
118 int listensocks[MAX_LISTEN_ADDR];
119 size_t listensockcount = 0;
120 FILE *pidfile = NULL;
121
122 int childpipes[MAX_UNAUTH_CLIENTS];
123 char * preauth_addrs[MAX_UNAUTH_CLIENTS];
124
125 int childsock;
126 int childpipe[2];
127
128 /* Note: commonsetup() must happen before we daemon()ise. Otherwise
129 daemon() will chdir("/"), and we won't be able to find local-dir
130 hostkeys. */
131 commonsetup();
132
133 /* fork */
134 if (svr_opts.forkbg) {
135 int closefds = 0;
136 #ifndef DEBUG_TRACE
137 if (!svr_opts.usingsyslog) {
138 closefds = 1;
139 }
140 #endif
141 if (daemon(0, closefds) < 0) {
142 dropbear_exit("Failed to daemonize: %s", strerror(errno));
143 }
144 }
145
146 /* should be done after syslog is working */
147 if (svr_opts.forkbg) {
148 dropbear_log(LOG_INFO, "Running in background");
149 } else {
150 dropbear_log(LOG_INFO, "Not forking");
151 }
152
153 /* create a PID file so that we can be killed easily */
154 pidfile = fopen(svr_opts.pidfile, "w");
155 if (pidfile) {
156 fprintf(pidfile, "%d\n", getpid());
157 fclose(pidfile);
158 }
159
160 /* sockets to identify pre-authenticated clients */
161 for (i = 0; i < MAX_UNAUTH_CLIENTS; i++) {
162 childpipes[i] = -1;
163 }
164 bzero(preauth_addrs, sizeof(preauth_addrs));
165
166 /* Set up the listening sockets */
167 listensockcount = listensockets(listensocks, MAX_LISTEN_ADDR, &maxsock);
168 if (listensockcount == 0)
169 {
170 dropbear_exit("No listening ports available.");
171 }
172
173 /* incoming connection select loop */
174 for(;;) {
175
176 FD_ZERO(&fds);
177
178 seltimeout.tv_sec = 60;
179 seltimeout.tv_usec = 0;
180
181 /* listening sockets */
182 for (i = 0; i < listensockcount; i++) {
183 FD_SET(listensocks[i], &fds);
184 }
185
186 /* pre-authentication clients */
187 for (i = 0; i < MAX_UNAUTH_CLIENTS; i++) {
188 if (childpipes[i] >= 0) {
189 FD_SET(childpipes[i], &fds);
190 maxsock = MAX(maxsock, childpipes[i]);
191 }
192 }
193
194 val = select(maxsock+1, &fds, NULL, NULL, &seltimeout);
195
196 if (exitflag) {
197 unlink(svr_opts.pidfile);
198 dropbear_exit("Terminated by signal");
199 }
200
201 if (val == 0) {
202 /* timeout reached */
203 continue;
204 }
205
206 if (val < 0) {
207 if (errno == EINTR) {
208 continue;
209 }
210 dropbear_exit("Listening socket error");
211 }
212
213 /* close fds which have been authed or closed - svr-auth.c handles
214 * closing the auth sockets on success */
215 for (i = 0; i < MAX_UNAUTH_CLIENTS; i++) {
216 if (childpipes[i] >= 0 && FD_ISSET(childpipes[i], &fds)) {
217 m_close(childpipes[i]);
218 childpipes[i] = -1;
219 m_free(preauth_addrs[i]);
220 }
221 }
222
223 /* handle each socket which has something to say */
224 for (i = 0; i < listensockcount; i++) {
225
226 struct sockaddr_storage remoteaddr;
227 socklen_t remoteaddrlen = 0;
228 size_t num_unauthed_for_addr = 0;
229 size_t num_unauthed_total = 0;
230 char * remote_addr_str = NULL;
231 pid_t fork_ret = 0;
232 size_t conn_idx = 0;
233
234 if (!FD_ISSET(listensocks[i], &fds))
235 continue;
236
237 remoteaddrlen = sizeof(remoteaddr);
238 childsock = accept(listensocks[i],
239 (struct sockaddr*)&remoteaddr, &remoteaddrlen);
240
241 if (childsock < 0) {
242 /* accept failed */
243 continue;
244 }
245
246 /* Limit the number of unauthenticated connections per IP */
247 remote_addr_str = getaddrstring(&remoteaddr, 0);
248
249 num_unauthed_for_addr = 0;
250 num_unauthed_total = 0;
251 for (j = 0; j < MAX_UNAUTH_CLIENTS; j++) {
252 if (childpipes[j] >= 0) {
253 num_unauthed_total++;
254 if (strcmp(remote_addr_str, preauth_addrs[j]) == 0) {
255 num_unauthed_for_addr++;
256 }
257 } else {
258 /* a free slot */
259 conn_idx = j;
260 }
261 }
262
263 if (num_unauthed_total >= MAX_UNAUTH_CLIENTS
264 || num_unauthed_for_addr >= MAX_UNAUTH_PER_IP) {
265 goto out;
266 }
267
268 if (pipe(childpipe) < 0) {
269 TRACE(("error creating child pipe"))
270 goto out;
271 }
272
273 fork_ret = fork();
274 if (fork_ret < 0) {
275 dropbear_log(LOG_WARNING, "error forking: %s", strerror(errno));
276 goto out;
277
278 } else if (fork_ret > 0) {
279
280 /* parent */
281 childpipes[conn_idx] = childpipe[0];
282 m_close(childpipe[1]);
283 preauth_addrs[conn_idx] = remote_addr_str;
284 remote_addr_str = NULL;
285
286 } else {
287
288 /* child */
289 char * addrstring = NULL;
290 #ifdef DEBUG_FORKGPROF
291 extern void _start(void), etext(void);
292 monstartup((u_long)&_start, (u_long)&etext);
293 #endif /* DEBUG_FORKGPROF */
294
295 m_free(remote_addr_str);
296 addrstring = getaddrstring(&remoteaddr, 1);
297 dropbear_log(LOG_INFO, "Child connection from %s", addrstring);
298
299 if (setsid() < 0) {
300 dropbear_exit("setsid: %s", strerror(errno));
301 }
302
303 /* make sure we close sockets */
304 for (i = 0; i < listensockcount; i++) {
305 m_close(listensocks[i]);
306 }
307
308 m_close(childpipe[0]);
309
310 /* start the session */
311 svr_session(childsock, childpipe[1],
312 getaddrhostname(&remoteaddr),
313 addrstring);
314 /* don't return */
315 dropbear_assert(0);
316 }
317
318 out:
319 /* This section is important for the parent too */
320 m_close(childsock);
321 if (remote_addr_str) {
322 m_free(remote_addr_str);
323 }
324 }
325 } /* for(;;) loop */
326
327 /* don't reach here */
328 }
329 #endif /* NON_INETD_MODE */
330
331
332 /* catch + reap zombie children */
sigchld_handler(int UNUSED (unused))333 static void sigchld_handler(int UNUSED(unused)) {
334 struct sigaction sa_chld;
335
336 while(waitpid(-1, NULL, WNOHANG) > 0);
337
338 sa_chld.sa_handler = sigchld_handler;
339 sa_chld.sa_flags = SA_NOCLDSTOP;
340 if (sigaction(SIGCHLD, &sa_chld, NULL) < 0) {
341 dropbear_exit("signal() error");
342 }
343 }
344
345 /* catch any segvs */
sigsegv_handler(int UNUSED (unused))346 static void sigsegv_handler(int UNUSED(unused)) {
347 fprintf(stderr, "Aiee, segfault! You should probably report "
348 "this as a bug to the developer\n");
349 exit(EXIT_FAILURE);
350 }
351
352 /* catch ctrl-c or sigterm */
sigintterm_handler(int UNUSED (unused))353 static void sigintterm_handler(int UNUSED(unused)) {
354
355 exitflag = 1;
356 }
357
358 /* Things used by inetd and non-inetd modes */
commonsetup()359 static void commonsetup() {
360
361 struct sigaction sa_chld;
362 #ifndef DISABLE_SYSLOG
363 if (svr_opts.usingsyslog) {
364 startsyslog();
365 }
366 #endif
367
368 /* set up cleanup handler */
369 if (signal(SIGINT, sigintterm_handler) == SIG_ERR ||
370 #ifndef DEBUG_VALGRIND
371 signal(SIGTERM, sigintterm_handler) == SIG_ERR ||
372 #endif
373 signal(SIGPIPE, SIG_IGN) == SIG_ERR) {
374 dropbear_exit("signal() error");
375 }
376
377 /* catch and reap zombie children */
378 sa_chld.sa_handler = sigchld_handler;
379 sa_chld.sa_flags = SA_NOCLDSTOP;
380 if (sigaction(SIGCHLD, &sa_chld, NULL) < 0) {
381 dropbear_exit("signal() error");
382 }
383 if (signal(SIGSEGV, sigsegv_handler) == SIG_ERR) {
384 dropbear_exit("signal() error");
385 }
386
387 /* Now we can setup the hostkeys - needs to be after logging is on,
388 * otherwise we might end up blatting error messages to the socket */
389 loadhostkeys();
390
391 seedrandom();
392 }
393
394 /* Set up listening sockets for all the requested ports */
listensockets(int * sock,size_t sockcount,int * maxfd)395 static size_t listensockets(int *sock, size_t sockcount, int *maxfd) {
396
397 unsigned int i;
398 char* errstring = NULL;
399 size_t sockpos = 0;
400 int nsock;
401
402 TRACE(("listensockets: %d to try\n", svr_opts.portcount))
403
404 for (i = 0; i < svr_opts.portcount; i++) {
405
406 TRACE(("listening on '%s:%s'", svr_opts.addresses[i], svr_opts.ports[i]))
407
408 nsock = dropbear_listen(svr_opts.addresses[i], svr_opts.ports[i], &sock[sockpos],
409 sockcount - sockpos,
410 &errstring, maxfd);
411
412 if (nsock < 0) {
413 dropbear_log(LOG_WARNING, "Failed listening on '%s': %s",
414 svr_opts.ports[i], errstring);
415 m_free(errstring);
416 continue;
417 }
418
419 sockpos += nsock;
420
421 }
422 return sockpos;
423 }
424