Make some strings const
[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] [--user-path | --user-path=path]\n"
22 " [--reuseaddr] [directory...]";
23
24 /* List of acceptable pathname prefixes */
25 static char **ok_paths = NULL;
26 static int strict_paths = 0;
27
28 /* If this is set, git-daemon-export-ok is not required */
29 static int export_all_trees = 0;
30
31 /* Take all paths relative to this one if non-NULL */
32 static char *base_path = NULL;
33
34 /* If defined, ~user notation is allowed and the string is inserted
35 * after ~user/. E.g. a request to git://host/~alice/frotz would
36 * go to /home/alice/pub_git/frotz with --user-path=pub_git.
37 */
38 static const char *user_path = NULL;
39
40 /* Timeout, and initial timeout */
41 static unsigned int timeout = 0;
42 static unsigned int init_timeout = 0;
43
44 static void logreport(int priority, const char *err, va_list params)
45 {
46 /* We should do a single write so that it is atomic and output
47 * of several processes do not get intermingled. */
48 char buf[1024];
49 int buflen;
50 int maxlen, msglen;
51
52 /* sizeof(buf) should be big enough for "[pid] \n" */
53 buflen = snprintf(buf, sizeof(buf), "[%ld] ", (long) getpid());
54
55 maxlen = sizeof(buf) - buflen - 1; /* -1 for our own LF */
56 msglen = vsnprintf(buf + buflen, maxlen, err, params);
57
58 if (log_syslog) {
59 syslog(priority, "%s", buf);
60 return;
61 }
62
63 /* maxlen counted our own LF but also counts space given to
64 * vsnprintf for the terminating NUL. We want to make sure that
65 * we have space for our own LF and NUL after the "meat" of the
66 * message, so truncate it at maxlen - 1.
67 */
68 if (msglen > maxlen - 1)
69 msglen = maxlen - 1;
70 else if (msglen < 0)
71 msglen = 0; /* Protect against weird return values. */
72 buflen += msglen;
73
74 buf[buflen++] = '\n';
75 buf[buflen] = '\0';
76
77 write(2, buf, buflen);
78 }
79
80 static void logerror(const char *err, ...)
81 {
82 va_list params;
83 va_start(params, err);
84 logreport(LOG_ERR, err, params);
85 va_end(params);
86 }
87
88 static void loginfo(const char *err, ...)
89 {
90 va_list params;
91 if (!verbose)
92 return;
93 va_start(params, err);
94 logreport(LOG_INFO, err, params);
95 va_end(params);
96 }
97
98 static int avoid_alias(char *p)
99 {
100 int sl, ndot;
101
102 /*
103 * This resurrects the belts and suspenders paranoia check by HPA
104 * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
105 * does not do getcwd() based path canonicalizations.
106 *
107 * sl becomes true immediately after seeing '/' and continues to
108 * be true as long as dots continue after that without intervening
109 * non-dot character.
110 */
111 if (!p || (*p != '/' && *p != '~'))
112 return -1;
113 sl = 1; ndot = 0;
114 p++;
115
116 while (1) {
117 char ch = *p++;
118 if (sl) {
119 if (ch == '.')
120 ndot++;
121 else if (ch == '/') {
122 if (ndot < 3)
123 /* reject //, /./ and /../ */
124 return -1;
125 ndot = 0;
126 }
127 else if (ch == 0) {
128 if (0 < ndot && ndot < 3)
129 /* reject /.$ and /..$ */
130 return -1;
131 return 0;
132 }
133 else
134 sl = ndot = 0;
135 }
136 else if (ch == 0)
137 return 0;
138 else if (ch == '/') {
139 sl = 1;
140 ndot = 0;
141 }
142 }
143 }
144
145 static char *path_ok(char *dir)
146 {
147 static char rpath[PATH_MAX];
148 char *path;
149
150 if (avoid_alias(dir)) {
151 logerror("'%s': aliased", dir);
152 return NULL;
153 }
154
155 if (*dir == '~') {
156 if (!user_path) {
157 logerror("'%s': User-path not allowed", dir);
158 return NULL;
159 }
160 if (*user_path) {
161 /* Got either "~alice" or "~alice/foo";
162 * rewrite them to "~alice/%s" or
163 * "~alice/%s/foo".
164 */
165 int namlen, restlen = strlen(dir);
166 char *slash = strchr(dir, '/');
167 if (!slash)
168 slash = dir + restlen;
169 namlen = slash - dir;
170 restlen -= namlen;
171 loginfo("userpath <%s>, request <%s>, namlen %d, restlen %d, slash <%s>", user_path, dir, namlen, restlen, slash);
172 snprintf(rpath, PATH_MAX, "%.*s/%s%.*s",
173 namlen, dir, user_path, restlen, slash);
174 dir = rpath;
175 }
176 }
177 else if (base_path) {
178 if (*dir != '/') {
179 /* Allow only absolute */
180 logerror("'%s': Non-absolute path denied (base-path active)", dir);
181 return NULL;
182 }
183 else {
184 snprintf(rpath, PATH_MAX, "%s%s", base_path, dir);
185 dir = rpath;
186 }
187 }
188
189 path = enter_repo(dir, strict_paths);
190
191 if (!path) {
192 logerror("'%s': unable to chdir or not a git archive", dir);
193 return NULL;
194 }
195
196 if ( ok_paths && *ok_paths ) {
197 char **pp;
198 int pathlen = strlen(path);
199
200 /* The validation is done on the paths after enter_repo
201 * appends optional {.git,.git/.git} and friends, but
202 * it does not use getcwd(). So if your /pub is
203 * a symlink to /mnt/pub, you can whitelist /pub and
204 * do not have to say /mnt/pub.
205 * Do not say /pub/.
206 */
207 for ( pp = ok_paths ; *pp ; pp++ ) {
208 int len = strlen(*pp);
209 if (len <= pathlen &&
210 !memcmp(*pp, path, len) &&
211 (path[len] == '\0' ||
212 (!strict_paths && path[len] == '/')))
213 return path;
214 }
215 }
216 else {
217 /* be backwards compatible */
218 if (!strict_paths)
219 return path;
220 }
221
222 logerror("'%s': not in whitelist", path);
223 return NULL; /* Fallthrough. Deny by default */
224 }
225
226 static int upload(char *dir)
227 {
228 /* Timeout as string */
229 char timeout_buf[64];
230 const char *path;
231
232 loginfo("Request for '%s'", dir);
233
234 if (!(path = path_ok(dir)))
235 return -1;
236
237 /*
238 * Security on the cheap.
239 *
240 * We want a readable HEAD, usable "objects" directory, and
241 * a "git-daemon-export-ok" flag that says that the other side
242 * is ok with us doing this.
243 *
244 * path_ok() uses enter_repo() and does whitelist checking.
245 * We only need to make sure the repository is exported.
246 */
247
248 if (!export_all_trees && access("git-daemon-export-ok", F_OK)) {
249 logerror("'%s': repository not exported.", path);
250 errno = EACCES;
251 return -1;
252 }
253
254 /*
255 * We'll ignore SIGTERM from now on, we have a
256 * good client.
257 */
258 signal(SIGTERM, SIG_IGN);
259
260 snprintf(timeout_buf, sizeof timeout_buf, "--timeout=%u", timeout);
261
262 /* git-upload-pack only ever reads stuff, so this is safe */
263 execl_git_cmd("upload-pack", "--strict", timeout_buf, ".", NULL);
264 return -1;
265 }
266
267 static int execute(struct sockaddr *addr)
268 {
269 static char line[1000];
270 int pktlen, len;
271
272 if (addr) {
273 char addrbuf[256] = "";
274 int port = -1;
275
276 if (addr->sa_family == AF_INET) {
277 struct sockaddr_in *sin_addr = (void *) addr;
278 inet_ntop(addr->sa_family, &sin_addr->sin_addr, addrbuf, sizeof(addrbuf));
279 port = sin_addr->sin_port;
280 #ifndef NO_IPV6
281 } else if (addr && addr->sa_family == AF_INET6) {
282 struct sockaddr_in6 *sin6_addr = (void *) addr;
283
284 char *buf = addrbuf;
285 *buf++ = '['; *buf = '\0'; /* stpcpy() is cool */
286 inet_ntop(AF_INET6, &sin6_addr->sin6_addr, buf, sizeof(addrbuf) - 1);
287 strcat(buf, "]");
288
289 port = sin6_addr->sin6_port;
290 #endif
291 }
292 loginfo("Connection from %s:%d", addrbuf, port);
293 }
294
295 alarm(init_timeout ? init_timeout : timeout);
296 pktlen = packet_read_line(0, line, sizeof(line));
297 alarm(0);
298
299 len = strlen(line);
300 if (pktlen != len)
301 loginfo("Extended attributes (%d bytes) exist <%.*s>",
302 (int) pktlen - len,
303 (int) pktlen - len, line + len + 1);
304 if (len && line[len-1] == '\n')
305 line[--len] = 0;
306
307 if (!strncmp("git-upload-pack ", line, 16))
308 return upload(line+16);
309
310 logerror("Protocol error: '%s'", line);
311 return -1;
312 }
313
314
315 /*
316 * We count spawned/reaped separately, just to avoid any
317 * races when updating them from signals. The SIGCHLD handler
318 * will only update children_reaped, and the fork logic will
319 * only update children_spawned.
320 *
321 * MAX_CHILDREN should be a power-of-two to make the modulus
322 * operation cheap. It should also be at least twice
323 * the maximum number of connections we will ever allow.
324 */
325 #define MAX_CHILDREN 128
326
327 static int max_connections = 25;
328
329 /* These are updated by the signal handler */
330 static volatile unsigned int children_reaped = 0;
331 static pid_t dead_child[MAX_CHILDREN];
332
333 /* These are updated by the main loop */
334 static unsigned int children_spawned = 0;
335 static unsigned int children_deleted = 0;
336
337 static struct child {
338 pid_t pid;
339 int addrlen;
340 struct sockaddr_storage address;
341 } live_child[MAX_CHILDREN];
342
343 static void add_child(int idx, pid_t pid, struct sockaddr *addr, int addrlen)
344 {
345 live_child[idx].pid = pid;
346 live_child[idx].addrlen = addrlen;
347 memcpy(&live_child[idx].address, addr, addrlen);
348 }
349
350 /*
351 * Walk from "deleted" to "spawned", and remove child "pid".
352 *
353 * We move everything up by one, since the new "deleted" will
354 * be one higher.
355 */
356 static void remove_child(pid_t pid, unsigned deleted, unsigned spawned)
357 {
358 struct child n;
359
360 deleted %= MAX_CHILDREN;
361 spawned %= MAX_CHILDREN;
362 if (live_child[deleted].pid == pid) {
363 live_child[deleted].pid = -1;
364 return;
365 }
366 n = live_child[deleted];
367 for (;;) {
368 struct child m;
369 deleted = (deleted + 1) % MAX_CHILDREN;
370 if (deleted == spawned)
371 die("could not find dead child %d\n", pid);
372 m = live_child[deleted];
373 live_child[deleted] = n;
374 if (m.pid == pid)
375 return;
376 n = m;
377 }
378 }
379
380 /*
381 * This gets called if the number of connections grows
382 * past "max_connections".
383 *
384 * We _should_ start off by searching for connections
385 * from the same IP, and if there is some address wth
386 * multiple connections, we should kill that first.
387 *
388 * As it is, we just "randomly" kill 25% of the connections,
389 * and our pseudo-random generator sucks too. I have no
390 * shame.
391 *
392 * Really, this is just a place-holder for a _real_ algorithm.
393 */
394 static void kill_some_children(int signo, unsigned start, unsigned stop)
395 {
396 start %= MAX_CHILDREN;
397 stop %= MAX_CHILDREN;
398 while (start != stop) {
399 if (!(start & 3))
400 kill(live_child[start].pid, signo);
401 start = (start + 1) % MAX_CHILDREN;
402 }
403 }
404
405 static void check_max_connections(void)
406 {
407 for (;;) {
408 int active;
409 unsigned spawned, reaped, deleted;
410
411 spawned = children_spawned;
412 reaped = children_reaped;
413 deleted = children_deleted;
414
415 while (deleted < reaped) {
416 pid_t pid = dead_child[deleted % MAX_CHILDREN];
417 remove_child(pid, deleted, spawned);
418 deleted++;
419 }
420 children_deleted = deleted;
421
422 active = spawned - deleted;
423 if (active <= max_connections)
424 break;
425
426 /* Kill some unstarted connections with SIGTERM */
427 kill_some_children(SIGTERM, deleted, spawned);
428 if (active <= max_connections << 1)
429 break;
430
431 /* If the SIGTERM thing isn't helping use SIGKILL */
432 kill_some_children(SIGKILL, deleted, spawned);
433 sleep(1);
434 }
435 }
436
437 static void handle(int incoming, struct sockaddr *addr, int addrlen)
438 {
439 pid_t pid = fork();
440
441 if (pid) {
442 unsigned idx;
443
444 close(incoming);
445 if (pid < 0)
446 return;
447
448 idx = children_spawned % MAX_CHILDREN;
449 children_spawned++;
450 add_child(idx, pid, addr, addrlen);
451
452 check_max_connections();
453 return;
454 }
455
456 dup2(incoming, 0);
457 dup2(incoming, 1);
458 close(incoming);
459
460 exit(execute(addr));
461 }
462
463 static void child_handler(int signo)
464 {
465 for (;;) {
466 int status;
467 pid_t pid = waitpid(-1, &status, WNOHANG);
468
469 if (pid > 0) {
470 unsigned reaped = children_reaped;
471 dead_child[reaped % MAX_CHILDREN] = pid;
472 children_reaped = reaped + 1;
473 /* XXX: Custom logging, since we don't wanna getpid() */
474 if (verbose) {
475 const char *dead = "";
476 if (!WIFEXITED(status) || WEXITSTATUS(status) > 0)
477 dead = " (with error)";
478 if (log_syslog)
479 syslog(LOG_INFO, "[%d] Disconnected%s", pid, dead);
480 else
481 fprintf(stderr, "[%d] Disconnected%s\n", pid, dead);
482 }
483 continue;
484 }
485 break;
486 }
487 }
488
489 static int set_reuse_addr(int sockfd)
490 {
491 int on = 1;
492
493 if (!reuseaddr)
494 return 0;
495 return setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR,
496 &on, sizeof(on));
497 }
498
499 #ifndef NO_IPV6
500
501 static int socksetup(int port, int **socklist_p)
502 {
503 int socknum = 0, *socklist = NULL;
504 int maxfd = -1;
505 char pbuf[NI_MAXSERV];
506
507 struct addrinfo hints, *ai0, *ai;
508 int gai;
509
510 sprintf(pbuf, "%d", port);
511 memset(&hints, 0, sizeof(hints));
512 hints.ai_family = AF_UNSPEC;
513 hints.ai_socktype = SOCK_STREAM;
514 hints.ai_protocol = IPPROTO_TCP;
515 hints.ai_flags = AI_PASSIVE;
516
517 gai = getaddrinfo(NULL, pbuf, &hints, &ai0);
518 if (gai)
519 die("getaddrinfo() failed: %s\n", gai_strerror(gai));
520
521 for (ai = ai0; ai; ai = ai->ai_next) {
522 int sockfd;
523 int *newlist;
524
525 sockfd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
526 if (sockfd < 0)
527 continue;
528 if (sockfd >= FD_SETSIZE) {
529 error("too large socket descriptor.");
530 close(sockfd);
531 continue;
532 }
533
534 #ifdef IPV6_V6ONLY
535 if (ai->ai_family == AF_INET6) {
536 int on = 1;
537 setsockopt(sockfd, IPPROTO_IPV6, IPV6_V6ONLY,
538 &on, sizeof(on));
539 /* Note: error is not fatal */
540 }
541 #endif
542
543 if (set_reuse_addr(sockfd)) {
544 close(sockfd);
545 continue;
546 }
547
548 if (bind(sockfd, ai->ai_addr, ai->ai_addrlen) < 0) {
549 close(sockfd);
550 continue; /* not fatal */
551 }
552 if (listen(sockfd, 5) < 0) {
553 close(sockfd);
554 continue; /* not fatal */
555 }
556
557 newlist = realloc(socklist, sizeof(int) * (socknum + 1));
558 if (!newlist)
559 die("memory allocation failed: %s", strerror(errno));
560
561 socklist = newlist;
562 socklist[socknum++] = sockfd;
563
564 if (maxfd < sockfd)
565 maxfd = sockfd;
566 }
567
568 freeaddrinfo(ai0);
569
570 *socklist_p = socklist;
571 return socknum;
572 }
573
574 #else /* NO_IPV6 */
575
576 static int socksetup(int port, int **socklist_p)
577 {
578 struct sockaddr_in sin;
579 int sockfd;
580
581 sockfd = socket(AF_INET, SOCK_STREAM, 0);
582 if (sockfd < 0)
583 return 0;
584
585 memset(&sin, 0, sizeof sin);
586 sin.sin_family = AF_INET;
587 sin.sin_addr.s_addr = htonl(INADDR_ANY);
588 sin.sin_port = htons(port);
589
590 if (set_reuse_addr(sockfd)) {
591 close(sockfd);
592 return 0;
593 }
594
595 if ( bind(sockfd, (struct sockaddr *)&sin, sizeof sin) < 0 ) {
596 close(sockfd);
597 return 0;
598 }
599
600 if (listen(sockfd, 5) < 0) {
601 close(sockfd);
602 return 0;
603 }
604
605 *socklist_p = xmalloc(sizeof(int));
606 **socklist_p = sockfd;
607 return 1;
608 }
609
610 #endif
611
612 static int service_loop(int socknum, int *socklist)
613 {
614 struct pollfd *pfd;
615 int i;
616
617 pfd = xcalloc(socknum, sizeof(struct pollfd));
618
619 for (i = 0; i < socknum; i++) {
620 pfd[i].fd = socklist[i];
621 pfd[i].events = POLLIN;
622 }
623
624 signal(SIGCHLD, child_handler);
625
626 for (;;) {
627 int i;
628
629 if (poll(pfd, socknum, -1) < 0) {
630 if (errno != EINTR) {
631 error("poll failed, resuming: %s",
632 strerror(errno));
633 sleep(1);
634 }
635 continue;
636 }
637
638 for (i = 0; i < socknum; i++) {
639 if (pfd[i].revents & POLLIN) {
640 struct sockaddr_storage ss;
641 unsigned int sslen = sizeof(ss);
642 int incoming = accept(pfd[i].fd, (struct sockaddr *)&ss, &sslen);
643 if (incoming < 0) {
644 switch (errno) {
645 case EAGAIN:
646 case EINTR:
647 case ECONNABORTED:
648 continue;
649 default:
650 die("accept returned %s", strerror(errno));
651 }
652 }
653 handle(incoming, (struct sockaddr *)&ss, sslen);
654 }
655 }
656 }
657 }
658
659 static int serve(int port)
660 {
661 int socknum, *socklist;
662
663 socknum = socksetup(port, &socklist);
664 if (socknum == 0)
665 die("unable to allocate any listen sockets on port %u", port);
666
667 return service_loop(socknum, socklist);
668 }
669
670 int main(int argc, char **argv)
671 {
672 int port = DEFAULT_GIT_PORT;
673 int inetd_mode = 0;
674 int i;
675
676 /* Without this we cannot rely on waitpid() to tell
677 * what happened to our children.
678 */
679 signal(SIGCHLD, SIG_DFL);
680
681 for (i = 1; i < argc; i++) {
682 char *arg = argv[i];
683
684 if (!strncmp(arg, "--port=", 7)) {
685 char *end;
686 unsigned long n;
687 n = strtoul(arg+7, &end, 0);
688 if (arg[7] && !*end) {
689 port = n;
690 continue;
691 }
692 }
693 if (!strcmp(arg, "--inetd")) {
694 inetd_mode = 1;
695 log_syslog = 1;
696 continue;
697 }
698 if (!strcmp(arg, "--verbose")) {
699 verbose = 1;
700 continue;
701 }
702 if (!strcmp(arg, "--syslog")) {
703 log_syslog = 1;
704 continue;
705 }
706 if (!strcmp(arg, "--export-all")) {
707 export_all_trees = 1;
708 continue;
709 }
710 if (!strncmp(arg, "--timeout=", 10)) {
711 timeout = atoi(arg+10);
712 continue;
713 }
714 if (!strncmp(arg, "--init-timeout=", 15)) {
715 init_timeout = atoi(arg+15);
716 continue;
717 }
718 if (!strcmp(arg, "--strict-paths")) {
719 strict_paths = 1;
720 continue;
721 }
722 if (!strncmp(arg, "--base-path=", 12)) {
723 base_path = arg+12;
724 continue;
725 }
726 if (!strcmp(arg, "--reuseaddr")) {
727 reuseaddr = 1;
728 continue;
729 }
730 if (!strcmp(arg, "--user-path")) {
731 user_path = "";
732 continue;
733 }
734 if (!strncmp(arg, "--user-path=", 12)) {
735 user_path = arg + 12;
736 continue;
737 }
738 if (!strcmp(arg, "--")) {
739 ok_paths = &argv[i+1];
740 break;
741 } else if (arg[0] != '-') {
742 ok_paths = &argv[i];
743 break;
744 }
745
746 usage(daemon_usage);
747 }
748
749 if (log_syslog)
750 openlog("git-daemon", 0, LOG_DAEMON);
751
752 if (strict_paths && (!ok_paths || !*ok_paths)) {
753 if (!inetd_mode)
754 die("git-daemon: option --strict-paths requires a whitelist");
755
756 logerror("option --strict-paths requires a whitelist");
757 exit (1);
758 }
759
760 if (inetd_mode) {
761 struct sockaddr_storage ss;
762 struct sockaddr *peer = (struct sockaddr *)&ss;
763 socklen_t slen = sizeof(ss);
764
765 freopen("/dev/null", "w", stderr);
766
767 if (getpeername(0, peer, &slen))
768 peer = NULL;
769
770 return execute(peer);
771 }
772
773 return serve(port);
774 }