daemon: Set SO_REUSEADDR on listening sockets.
[git/git.git] / daemon.c
1 #include <signal.h>
2 #include <sys/wait.h>
3 #include <sys/socket.h>
4 #include <sys/time.h>
5 #include <sys/poll.h>
6 #include <netdb.h>
7 #include <netinet/in.h>
8 #include <arpa/inet.h>
9 #include <syslog.h>
10 #include "pkt-line.h"
11 #include "cache.h"
12 #include "exec_cmd.h"
13
14 static int log_syslog;
15 static int verbose;
16 static int reuseaddr;
17
18 static const char daemon_usage[] =
19 "git-daemon [--verbose] [--syslog] [--inetd | --port=n] [--export-all]\n"
20 " [--timeout=n] [--init-timeout=n] [--strict-paths]\n"
21 " [--base-path=path] [--reuseaddr] [directory...]";
22
23 /* List of acceptable pathname prefixes */
24 static char **ok_paths = NULL;
25 static int strict_paths = 0;
26
27 /* If this is set, git-daemon-export-ok is not required */
28 static int export_all_trees = 0;
29
30 /* Take all paths relative to this one if non-NULL */
31 static char *base_path = NULL;
32
33 /* Timeout, and initial timeout */
34 static unsigned int timeout = 0;
35 static unsigned int init_timeout = 0;
36
37 static void logreport(int priority, const char *err, va_list params)
38 {
39 /* We should do a single write so that it is atomic and output
40 * of several processes do not get intermingled. */
41 char buf[1024];
42 int buflen;
43 int maxlen, msglen;
44
45 /* sizeof(buf) should be big enough for "[pid] \n" */
46 buflen = snprintf(buf, sizeof(buf), "[%ld] ", (long) getpid());
47
48 maxlen = sizeof(buf) - buflen - 1; /* -1 for our own LF */
49 msglen = vsnprintf(buf + buflen, maxlen, err, params);
50
51 if (log_syslog) {
52 syslog(priority, "%s", buf);
53 return;
54 }
55
56 /* maxlen counted our own LF but also counts space given to
57 * vsnprintf for the terminating NUL. We want to make sure that
58 * we have space for our own LF and NUL after the "meat" of the
59 * message, so truncate it at maxlen - 1.
60 */
61 if (msglen > maxlen - 1)
62 msglen = maxlen - 1;
63 else if (msglen < 0)
64 msglen = 0; /* Protect against weird return values. */
65 buflen += msglen;
66
67 buf[buflen++] = '\n';
68 buf[buflen] = '\0';
69
70 write(2, buf, buflen);
71 }
72
73 static void logerror(const char *err, ...)
74 {
75 va_list params;
76 va_start(params, err);
77 logreport(LOG_ERR, err, params);
78 va_end(params);
79 }
80
81 static void loginfo(const char *err, ...)
82 {
83 va_list params;
84 if (!verbose)
85 return;
86 va_start(params, err);
87 logreport(LOG_INFO, err, params);
88 va_end(params);
89 }
90
91 static int avoid_alias(char *p)
92 {
93 int sl, ndot;
94
95 /*
96 * This resurrects the belts and suspenders paranoia check by HPA
97 * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
98 * does not do getcwd() based path canonicalizations.
99 *
100 * sl becomes true immediately after seeing '/' and continues to
101 * be true as long as dots continue after that without intervening
102 * non-dot character.
103 */
104 if (!p || (*p != '/' && *p != '~'))
105 return -1;
106 sl = 1; ndot = 0;
107 p++;
108
109 while (1) {
110 char ch = *p++;
111 if (sl) {
112 if (ch == '.')
113 ndot++;
114 else if (ch == '/') {
115 if (ndot < 3)
116 /* reject //, /./ and /../ */
117 return -1;
118 ndot = 0;
119 }
120 else if (ch == 0) {
121 if (0 < ndot && ndot < 3)
122 /* reject /.$ and /..$ */
123 return -1;
124 return 0;
125 }
126 else
127 sl = ndot = 0;
128 }
129 else if (ch == 0)
130 return 0;
131 else if (ch == '/') {
132 sl = 1;
133 ndot = 0;
134 }
135 }
136 }
137
138 static char *path_ok(char *dir)
139 {
140 char *path;
141
142 if (avoid_alias(dir)) {
143 logerror("'%s': aliased", dir);
144 return NULL;
145 }
146
147 if (base_path) {
148 static char rpath[PATH_MAX];
149 if (!strict_paths && *dir == '~')
150 ; /* allow user relative paths */
151 else if (*dir != '/') {
152 /* otherwise allow only absolute */
153 logerror("'%s': Non-absolute path denied (base-path active)", dir);
154 return NULL;
155 }
156 else {
157 snprintf(rpath, PATH_MAX, "%s%s", base_path, dir);
158 dir = rpath;
159 }
160 }
161
162 path = enter_repo(dir, strict_paths);
163
164 if (!path) {
165 logerror("'%s': unable to chdir or not a git archive", dir);
166 return NULL;
167 }
168
169 if ( ok_paths && *ok_paths ) {
170 char **pp;
171 int pathlen = strlen(path);
172
173 /* The validation is done on the paths after enter_repo
174 * appends optional {.git,.git/.git} and friends, but
175 * it does not use getcwd(). So if your /pub is
176 * a symlink to /mnt/pub, you can whitelist /pub and
177 * do not have to say /mnt/pub.
178 * Do not say /pub/.
179 */
180 for ( pp = ok_paths ; *pp ; pp++ ) {
181 int len = strlen(*pp);
182 if (len <= pathlen &&
183 !memcmp(*pp, path, len) &&
184 (path[len] == '\0' ||
185 (!strict_paths && path[len] == '/')))
186 return path;
187 }
188 }
189 else {
190 /* be backwards compatible */
191 if (!strict_paths)
192 return path;
193 }
194
195 logerror("'%s': not in whitelist", path);
196 return NULL; /* Fallthrough. Deny by default */
197 }
198
199 static int upload(char *dir)
200 {
201 /* Timeout as string */
202 char timeout_buf[64];
203 const char *path;
204
205 loginfo("Request for '%s'", dir);
206
207 if (!(path = path_ok(dir)))
208 return -1;
209
210 /*
211 * Security on the cheap.
212 *
213 * We want a readable HEAD, usable "objects" directory, and
214 * a "git-daemon-export-ok" flag that says that the other side
215 * is ok with us doing this.
216 *
217 * path_ok() uses enter_repo() and does whitelist checking.
218 * We only need to make sure the repository is exported.
219 */
220
221 if (!export_all_trees && access("git-daemon-export-ok", F_OK)) {
222 logerror("'%s': repository not exported.", path);
223 errno = EACCES;
224 return -1;
225 }
226
227 /*
228 * We'll ignore SIGTERM from now on, we have a
229 * good client.
230 */
231 signal(SIGTERM, SIG_IGN);
232
233 snprintf(timeout_buf, sizeof timeout_buf, "--timeout=%u", timeout);
234
235 /* git-upload-pack only ever reads stuff, so this is safe */
236 execl_git_cmd("upload-pack", "--strict", timeout_buf, ".", NULL);
237 return -1;
238 }
239
240 static int execute(void)
241 {
242 static char line[1000];
243 int len;
244
245 alarm(init_timeout ? init_timeout : timeout);
246 len = packet_read_line(0, line, sizeof(line));
247 alarm(0);
248
249 if (len && line[len-1] == '\n')
250 line[--len] = 0;
251
252 if (!strncmp("git-upload-pack ", line, 16))
253 return upload(line+16);
254
255 logerror("Protocol error: '%s'", line);
256 return -1;
257 }
258
259
260 /*
261 * We count spawned/reaped separately, just to avoid any
262 * races when updating them from signals. The SIGCHLD handler
263 * will only update children_reaped, and the fork logic will
264 * only update children_spawned.
265 *
266 * MAX_CHILDREN should be a power-of-two to make the modulus
267 * operation cheap. It should also be at least twice
268 * the maximum number of connections we will ever allow.
269 */
270 #define MAX_CHILDREN 128
271
272 static int max_connections = 25;
273
274 /* These are updated by the signal handler */
275 static volatile unsigned int children_reaped = 0;
276 static pid_t dead_child[MAX_CHILDREN];
277
278 /* These are updated by the main loop */
279 static unsigned int children_spawned = 0;
280 static unsigned int children_deleted = 0;
281
282 static struct child {
283 pid_t pid;
284 int addrlen;
285 struct sockaddr_storage address;
286 } live_child[MAX_CHILDREN];
287
288 static void add_child(int idx, pid_t pid, struct sockaddr *addr, int addrlen)
289 {
290 live_child[idx].pid = pid;
291 live_child[idx].addrlen = addrlen;
292 memcpy(&live_child[idx].address, addr, addrlen);
293 }
294
295 /*
296 * Walk from "deleted" to "spawned", and remove child "pid".
297 *
298 * We move everything up by one, since the new "deleted" will
299 * be one higher.
300 */
301 static void remove_child(pid_t pid, unsigned deleted, unsigned spawned)
302 {
303 struct child n;
304
305 deleted %= MAX_CHILDREN;
306 spawned %= MAX_CHILDREN;
307 if (live_child[deleted].pid == pid) {
308 live_child[deleted].pid = -1;
309 return;
310 }
311 n = live_child[deleted];
312 for (;;) {
313 struct child m;
314 deleted = (deleted + 1) % MAX_CHILDREN;
315 if (deleted == spawned)
316 die("could not find dead child %d\n", pid);
317 m = live_child[deleted];
318 live_child[deleted] = n;
319 if (m.pid == pid)
320 return;
321 n = m;
322 }
323 }
324
325 /*
326 * This gets called if the number of connections grows
327 * past "max_connections".
328 *
329 * We _should_ start off by searching for connections
330 * from the same IP, and if there is some address wth
331 * multiple connections, we should kill that first.
332 *
333 * As it is, we just "randomly" kill 25% of the connections,
334 * and our pseudo-random generator sucks too. I have no
335 * shame.
336 *
337 * Really, this is just a place-holder for a _real_ algorithm.
338 */
339 static void kill_some_children(int signo, unsigned start, unsigned stop)
340 {
341 start %= MAX_CHILDREN;
342 stop %= MAX_CHILDREN;
343 while (start != stop) {
344 if (!(start & 3))
345 kill(live_child[start].pid, signo);
346 start = (start + 1) % MAX_CHILDREN;
347 }
348 }
349
350 static void check_max_connections(void)
351 {
352 for (;;) {
353 int active;
354 unsigned spawned, reaped, deleted;
355
356 spawned = children_spawned;
357 reaped = children_reaped;
358 deleted = children_deleted;
359
360 while (deleted < reaped) {
361 pid_t pid = dead_child[deleted % MAX_CHILDREN];
362 remove_child(pid, deleted, spawned);
363 deleted++;
364 }
365 children_deleted = deleted;
366
367 active = spawned - deleted;
368 if (active <= max_connections)
369 break;
370
371 /* Kill some unstarted connections with SIGTERM */
372 kill_some_children(SIGTERM, deleted, spawned);
373 if (active <= max_connections << 1)
374 break;
375
376 /* If the SIGTERM thing isn't helping use SIGKILL */
377 kill_some_children(SIGKILL, deleted, spawned);
378 sleep(1);
379 }
380 }
381
382 static void handle(int incoming, struct sockaddr *addr, int addrlen)
383 {
384 pid_t pid = fork();
385 char addrbuf[256] = "";
386 int port = -1;
387
388 if (pid) {
389 unsigned idx;
390
391 close(incoming);
392 if (pid < 0)
393 return;
394
395 idx = children_spawned % MAX_CHILDREN;
396 children_spawned++;
397 add_child(idx, pid, addr, addrlen);
398
399 check_max_connections();
400 return;
401 }
402
403 dup2(incoming, 0);
404 dup2(incoming, 1);
405 close(incoming);
406
407 if (addr->sa_family == AF_INET) {
408 struct sockaddr_in *sin_addr = (void *) addr;
409 inet_ntop(AF_INET, &sin_addr->sin_addr, addrbuf, sizeof(addrbuf));
410 port = sin_addr->sin_port;
411
412 #ifndef NO_IPV6
413 } else if (addr->sa_family == AF_INET6) {
414 struct sockaddr_in6 *sin6_addr = (void *) addr;
415
416 char *buf = addrbuf;
417 *buf++ = '['; *buf = '\0'; /* stpcpy() is cool */
418 inet_ntop(AF_INET6, &sin6_addr->sin6_addr, buf, sizeof(addrbuf) - 1);
419 strcat(buf, "]");
420
421 port = sin6_addr->sin6_port;
422 #endif
423 }
424 loginfo("Connection from %s:%d", addrbuf, port);
425
426 exit(execute());
427 }
428
429 static void child_handler(int signo)
430 {
431 for (;;) {
432 int status;
433 pid_t pid = waitpid(-1, &status, WNOHANG);
434
435 if (pid > 0) {
436 unsigned reaped = children_reaped;
437 dead_child[reaped % MAX_CHILDREN] = pid;
438 children_reaped = reaped + 1;
439 /* XXX: Custom logging, since we don't wanna getpid() */
440 if (verbose) {
441 char *dead = "";
442 if (!WIFEXITED(status) || WEXITSTATUS(status) > 0)
443 dead = " (with error)";
444 if (log_syslog)
445 syslog(LOG_INFO, "[%d] Disconnected%s", pid, dead);
446 else
447 fprintf(stderr, "[%d] Disconnected%s\n", pid, dead);
448 }
449 continue;
450 }
451 break;
452 }
453 }
454
455 static int set_reuse_addr(int sockfd)
456 {
457 int on = 1;
458
459 if (!reuseaddr)
460 return 0;
461 return setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR,
462 &on, sizeof(on));
463 }
464
465 #ifndef NO_IPV6
466
467 static int socksetup(int port, int **socklist_p)
468 {
469 int socknum = 0, *socklist = NULL;
470 int maxfd = -1;
471 char pbuf[NI_MAXSERV];
472
473 struct addrinfo hints, *ai0, *ai;
474 int gai;
475
476 sprintf(pbuf, "%d", port);
477 memset(&hints, 0, sizeof(hints));
478 hints.ai_family = AF_UNSPEC;
479 hints.ai_socktype = SOCK_STREAM;
480 hints.ai_protocol = IPPROTO_TCP;
481 hints.ai_flags = AI_PASSIVE;
482
483 gai = getaddrinfo(NULL, pbuf, &hints, &ai0);
484 if (gai)
485 die("getaddrinfo() failed: %s\n", gai_strerror(gai));
486
487 for (ai = ai0; ai; ai = ai->ai_next) {
488 int sockfd;
489 int *newlist;
490
491 sockfd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
492 if (sockfd < 0)
493 continue;
494 if (sockfd >= FD_SETSIZE) {
495 error("too large socket descriptor.");
496 close(sockfd);
497 continue;
498 }
499
500 #ifdef IPV6_V6ONLY
501 if (ai->ai_family == AF_INET6) {
502 int on = 1;
503 setsockopt(sockfd, IPPROTO_IPV6, IPV6_V6ONLY,
504 &on, sizeof(on));
505 /* Note: error is not fatal */
506 }
507 #endif
508
509 if (set_reuse_addr(sockfd)) {
510 close(sockfd);
511 return 0; /* not fatal */
512 }
513
514 if (bind(sockfd, ai->ai_addr, ai->ai_addrlen) < 0) {
515 close(sockfd);
516 continue; /* not fatal */
517 }
518 if (listen(sockfd, 5) < 0) {
519 close(sockfd);
520 continue; /* not fatal */
521 }
522
523 newlist = realloc(socklist, sizeof(int) * (socknum + 1));
524 if (!newlist)
525 die("memory allocation failed: %s", strerror(errno));
526
527 socklist = newlist;
528 socklist[socknum++] = sockfd;
529
530 if (maxfd < sockfd)
531 maxfd = sockfd;
532 }
533
534 freeaddrinfo(ai0);
535
536 *socklist_p = socklist;
537 return socknum;
538 }
539
540 #else /* NO_IPV6 */
541
542 static int socksetup(int port, int **socklist_p)
543 {
544 struct sockaddr_in sin;
545 int sockfd;
546
547 sockfd = socket(AF_INET, SOCK_STREAM, 0);
548 if (sockfd < 0)
549 return 0;
550
551 memset(&sin, 0, sizeof sin);
552 sin.sin_family = AF_INET;
553 sin.sin_addr.s_addr = htonl(INADDR_ANY);
554 sin.sin_port = htons(port);
555
556 if (set_reuse_addr(sockfd)) {
557 close(sockfd);
558 return 0;
559 }
560
561 if ( bind(sockfd, (struct sockaddr *)&sin, sizeof sin) < 0 ) {
562 close(sockfd);
563 return 0;
564 }
565
566 if (listen(sockfd, 5) < 0) {
567 close(sockfd);
568 return 0;
569 }
570
571 *socklist_p = xmalloc(sizeof(int));
572 **socklist_p = sockfd;
573 return 1;
574 }
575
576 #endif
577
578 static int service_loop(int socknum, int *socklist)
579 {
580 struct pollfd *pfd;
581 int i;
582
583 pfd = xcalloc(socknum, sizeof(struct pollfd));
584
585 for (i = 0; i < socknum; i++) {
586 pfd[i].fd = socklist[i];
587 pfd[i].events = POLLIN;
588 }
589
590 signal(SIGCHLD, child_handler);
591
592 for (;;) {
593 int i;
594
595 if (poll(pfd, socknum, -1) < 0) {
596 if (errno != EINTR) {
597 error("poll failed, resuming: %s",
598 strerror(errno));
599 sleep(1);
600 }
601 continue;
602 }
603
604 for (i = 0; i < socknum; i++) {
605 if (pfd[i].revents & POLLIN) {
606 struct sockaddr_storage ss;
607 unsigned int sslen = sizeof(ss);
608 int incoming = accept(pfd[i].fd, (struct sockaddr *)&ss, &sslen);
609 if (incoming < 0) {
610 switch (errno) {
611 case EAGAIN:
612 case EINTR:
613 case ECONNABORTED:
614 continue;
615 default:
616 die("accept returned %s", strerror(errno));
617 }
618 }
619 handle(incoming, (struct sockaddr *)&ss, sslen);
620 }
621 }
622 }
623 }
624
625 static int serve(int port)
626 {
627 int socknum, *socklist;
628
629 socknum = socksetup(port, &socklist);
630 if (socknum == 0)
631 die("unable to allocate any listen sockets on port %u", port);
632
633 return service_loop(socknum, socklist);
634 }
635
636 int main(int argc, char **argv)
637 {
638 int port = DEFAULT_GIT_PORT;
639 int inetd_mode = 0;
640 int i;
641
642 for (i = 1; i < argc; i++) {
643 char *arg = argv[i];
644
645 if (!strncmp(arg, "--port=", 7)) {
646 char *end;
647 unsigned long n;
648 n = strtoul(arg+7, &end, 0);
649 if (arg[7] && !*end) {
650 port = n;
651 continue;
652 }
653 }
654 if (!strcmp(arg, "--inetd")) {
655 inetd_mode = 1;
656 log_syslog = 1;
657 continue;
658 }
659 if (!strcmp(arg, "--verbose")) {
660 verbose = 1;
661 continue;
662 }
663 if (!strcmp(arg, "--syslog")) {
664 log_syslog = 1;
665 continue;
666 }
667 if (!strcmp(arg, "--export-all")) {
668 export_all_trees = 1;
669 continue;
670 }
671 if (!strncmp(arg, "--timeout=", 10)) {
672 timeout = atoi(arg+10);
673 continue;
674 }
675 if (!strncmp(arg, "--init-timeout=", 15)) {
676 init_timeout = atoi(arg+15);
677 continue;
678 }
679 if (!strcmp(arg, "--strict-paths")) {
680 strict_paths = 1;
681 continue;
682 }
683 if (!strncmp(arg, "--base-path=", 12)) {
684 base_path = arg+12;
685 continue;
686 }
687 if (!strcmp(arg, "--reuseaddr")) {
688 reuseaddr = 1;
689 continue;
690 }
691 if (!strcmp(arg, "--")) {
692 ok_paths = &argv[i+1];
693 break;
694 } else if (arg[0] != '-') {
695 ok_paths = &argv[i];
696 break;
697 }
698
699 usage(daemon_usage);
700 }
701
702 if (log_syslog)
703 openlog("git-daemon", 0, LOG_DAEMON);
704
705 if (strict_paths && (!ok_paths || !*ok_paths)) {
706 if (!inetd_mode)
707 die("git-daemon: option --strict-paths requires a whitelist");
708
709 logerror("option --strict-paths requires a whitelist");
710 exit (1);
711 }
712
713 if (inetd_mode) {
714 fclose(stderr); //FIXME: workaround
715 return execute();
716 }
717
718 return serve(port);
719 }