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