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