aboutsummaryrefslogtreecommitdiff
path: root/daemon.c
blob: bdfe80d2e4f4fc13ad45bd35aeeeb3ec71422a4f (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
696
697
698
699
700
701
702
703
704
705
706
707
708
709
710
711
712
713
714
715
716
717
718
719
720
721
722
723
724
725
726
727
728
729
730
731
732
733
734
735
736
737
738
739
740
741
742
743
744
745
746
747
748
749
750
751
752
753
754
755
756
757
758
759
760
761
762
763
764
765
766
767
768
769
#include <signal.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <sys/time.h>
#include <sys/poll.h>
#include <netdb.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <syslog.h>
#include "pkt-line.h"
#include "cache.h"
#include "exec_cmd.h"

static int log_syslog;
static int verbose;
static int reuseaddr;

static const char daemon_usage[] =
"git-daemon [--verbose] [--syslog] [--inetd | --port=n] [--export-all]\n"
"           [--timeout=n] [--init-timeout=n] [--strict-paths]\n"
"           [--base-path=path] [--user-path | --user-path=path]\n"
"           [--reuseaddr] [directory...]";

/* List of acceptable pathname prefixes */
static char **ok_paths = NULL;
static int strict_paths = 0;

/* If this is set, git-daemon-export-ok is not required */
static int export_all_trees = 0;

/* Take all paths relative to this one if non-NULL */
static char *base_path = NULL;

/* If defined, ~user notation is allowed and the string is inserted
 * after ~user/.  E.g. a request to git://host/~alice/frotz would
 * go to /home/alice/pub_git/frotz with --user-path=pub_git.
 */
static char *user_path = NULL;

/* Timeout, and initial timeout */
static unsigned int timeout = 0;
static unsigned int init_timeout = 0;

static void logreport(int priority, const char *err, va_list params)
{
	/* We should do a single write so that it is atomic and output
	 * of several processes do not get intermingled. */
	char buf[1024];
	int buflen;
	int maxlen, msglen;

	/* sizeof(buf) should be big enough for "[pid] \n" */
	buflen = snprintf(buf, sizeof(buf), "[%ld] ", (long) getpid());

	maxlen = sizeof(buf) - buflen - 1; /* -1 for our own LF */
	msglen = vsnprintf(buf + buflen, maxlen, err, params);

	if (log_syslog) {
		syslog(priority, "%s", buf);
		return;
	}

	/* maxlen counted our own LF but also counts space given to
	 * vsnprintf for the terminating NUL.  We want to make sure that
	 * we have space for our own LF and NUL after the "meat" of the
	 * message, so truncate it at maxlen - 1.
	 */
	if (msglen > maxlen - 1)
		msglen = maxlen - 1;
	else if (msglen < 0)
		msglen = 0; /* Protect against weird return values. */
	buflen += msglen;

	buf[buflen++] = '\n';
	buf[buflen] = '\0';

	write(2, buf, buflen);
}

static void logerror(const char *err, ...)
{
	va_list params;
	va_start(params, err);
	logreport(LOG_ERR, err, params);
	va_end(params);
}

static void loginfo(const char *err, ...)
{
	va_list params;
	if (!verbose)
		return;
	va_start(params, err);
	logreport(LOG_INFO, err, params);
	va_end(params);
}

static int avoid_alias(char *p)
{
	int sl, ndot;

	/* 
	 * This resurrects the belts and suspenders paranoia check by HPA
	 * done in <435560F7.4080006@zytor.com> thread, now enter_repo()
	 * does not do getcwd() based path canonicalizations.
	 *
	 * sl becomes true immediately after seeing '/' and continues to
	 * be true as long as dots continue after that without intervening
	 * non-dot character.
	 */
	if (!p || (*p != '/' && *p != '~'))
		return -1;
	sl = 1; ndot = 0;
	p++;

	while (1) {
		char ch = *p++;
		if (sl) {
			if (ch == '.')
				ndot++;
			else if (ch == '/') {
				if (ndot < 3)
					/* reject //, /./ and /../ */
					return -1;
				ndot = 0;
			}
			else if (ch == 0) {
				if (0 < ndot && ndot < 3)
					/* reject /.$ and /..$ */
					return -1;
				return 0;
			}
			else
				sl = ndot = 0;
		}
		else if (ch == 0)
			return 0;
		else if (ch == '/') {
			sl = 1;
			ndot = 0;
		}
	}
}

static char *path_ok(char *dir)
{
	static char rpath[PATH_MAX];
	char *path;

	if (avoid_alias(dir)) {
		logerror("'%s': aliased", dir);
		return NULL;
	}

	if (*dir == '~') {
		if (!user_path) {
			logerror("'%s': User-path not allowed", dir);
			return NULL;
		}
		if (*user_path) {
			/* Got either "~alice" or "~alice/foo";
			 * rewrite them to "~alice/%s" or
			 * "~alice/%s/foo".
			 */
			int namlen, restlen = strlen(dir);
			char *slash = strchr(dir, '/');
			if (!slash)
				slash = dir + restlen;
			namlen = slash - dir;
			restlen -= namlen;
			loginfo("userpath <%s>, request <%s>, namlen %d, restlen %d, slash <%s>", user_path, dir, namlen, restlen, slash);
			snprintf(rpath, PATH_MAX, "%.*s/%s%.*s",
				 namlen, dir, user_path, restlen, slash);
			dir = rpath;
		}
	}
	else if (base_path) {
		if (*dir != '/') {
			/* Allow only absolute */
			logerror("'%s': Non-absolute path denied (base-path active)", dir);
			return NULL;
		}
		else {
			snprintf(rpath, PATH_MAX, "%s%s", base_path, dir);
			dir = rpath;
		}
	}

	path = enter_repo(dir, strict_paths);

	if (!path) {
		logerror("'%s': unable to chdir or not a git archive", dir);
		return NULL;
	}

	if ( ok_paths && *ok_paths ) {
		char **pp;
		int pathlen = strlen(path);

		/* The validation is done on the paths after enter_repo
		 * appends optional {.git,.git/.git} and friends, but 
		 * it does not use getcwd().  So if your /pub is
		 * a symlink to /mnt/pub, you can whitelist /pub and
		 * do not have to say /mnt/pub.
		 * Do not say /pub/.
		 */
		for ( pp = ok_paths ; *pp ; pp++ ) {
			int len = strlen(*pp);
			if (len <= pathlen &&
			    !memcmp(*pp, path, len) &&
			    (path[len] == '\0' ||
			     (!strict_paths && path[len] == '/')))
				return path;
		}
	}
	else {
		/* be backwards compatible */
		if (!strict_paths)
			return path;
	}

	logerror("'%s': not in whitelist", path);
	return NULL;		/* Fallthrough. Deny by default */
}

static int upload(char *dir)
{
	/* Timeout as string */
	char timeout_buf[64];
	const char *path;

	loginfo("Request for '%s'", dir);

	if (!(path = path_ok(dir)))
		return -1;

	/*
	 * Security on the cheap.
	 *
	 * We want a readable HEAD, usable "objects" directory, and
	 * a "git-daemon-export-ok" flag that says that the other side
	 * is ok with us doing this.
	 *
	 * path_ok() uses enter_repo() and does whitelist checking.
	 * We only need to make sure the repository is exported.
	 */

	if (!export_all_trees && access("git-daemon-export-ok", F_OK)) {
		logerror("'%s': repository not exported.", path);
		errno = EACCES;
		return -1;
	}

	/*
	 * We'll ignore SIGTERM from now on, we have a
	 * good client.
	 */
	signal(SIGTERM, SIG_IGN);

	snprintf(timeout_buf, sizeof timeout_buf, "--timeout=%u", timeout);

	/* git-upload-pack only ever reads stuff, so this is safe */
	execl_git_cmd("upload-pack", "--strict", timeout_buf, ".", NULL);
	return -1;
}

static int execute(struct sockaddr *addr)
{
	static char line[1000];
	int pktlen, len;

	if (addr) {
		char addrbuf[256] = "";
		int port = -1;

		if (addr->sa_family == AF_INET) {
			struct sockaddr_in *sin_addr = (void *) addr;
			inet_ntop(addr->sa_family, &sin_addr->sin_addr, addrbuf, sizeof(addrbuf));
			port = sin_addr->sin_port;
#ifndef NO_IPV6
		} else if (addr && addr->sa_family == AF_INET6) {
			struct sockaddr_in6 *sin6_addr = (void *) addr;

			char *buf = addrbuf;
			*buf++ = '['; *buf = '\0'; /* stpcpy() is cool */
			inet_ntop(AF_INET6, &sin6_addr->sin6_addr, buf, sizeof(addrbuf) - 1);
			strcat(buf, "]");

			port = sin6_addr->sin6_port;
#endif
		}
		loginfo("Connection from %s:%d", addrbuf, port);
	}

	alarm(init_timeout ? init_timeout : timeout);
	pktlen = packet_read_line(0, line, sizeof(line));
	alarm(0);

	len = strlen(line);
	if (pktlen != len)
		loginfo("Extended attributes (%d bytes) exist <%.*s>",
			(int) pktlen - len,
			(int) pktlen - len, line + len + 1);
	if (len && line[len-1] == '\n')
		line[--len] = 0;

	if (!strncmp("git-upload-pack ", line, 16))
		return upload(line+16);

	logerror("Protocol error: '%s'", line);
	return -1;
}


/*
 * We count spawned/reaped separately, just to avoid any
 * races when updating them from signals. The SIGCHLD handler
 * will only update children_reaped, and the fork logic will
 * only update children_spawned.
 *
 * MAX_CHILDREN should be a power-of-two to make the modulus
 * operation cheap. It should also be at least twice
 * the maximum number of connections we will ever allow.
 */
#define MAX_CHILDREN 128

static int max_connections = 25;

/* These are updated by the signal handler */
static volatile unsigned int children_reaped = 0;
static pid_t dead_child[MAX_CHILDREN];

/* These are updated by the main loop */
static unsigned int children_spawned = 0;
static unsigned int children_deleted = 0;

static struct child {
	pid_t pid;
	int addrlen;
	struct sockaddr_storage address;
} live_child[MAX_CHILDREN];

static void add_child(int idx, pid_t pid, struct sockaddr *addr, int addrlen)
{
	live_child[idx].pid = pid;
	live_child[idx].addrlen = addrlen;
	memcpy(&live_child[idx].address, addr, addrlen);
}

/*
 * Walk from "deleted" to "spawned", and remove child "pid".
 *
 * We move everything up by one, since the new "deleted" will
 * be one higher.
 */
static void remove_child(pid_t pid, unsigned deleted, unsigned spawned)
{
	struct child n;

	deleted %= MAX_CHILDREN;
	spawned %= MAX_CHILDREN;
	if (live_child[deleted].pid == pid) {
		live_child[deleted].pid = -1;
		return;
	}
	n = live_child[deleted];
	for (;;) {
		struct child m;
		deleted = (deleted + 1) % MAX_CHILDREN;
		if (deleted == spawned)
			die("could not find dead child %d\n", pid);
		m = live_child[deleted];
		live_child[deleted] = n;
		if (m.pid == pid)
			return;
		n = m;
	}
}

/*
 * This gets called if the number of connections grows
 * past "max_connections".
 *
 * We _should_ start off by searching for connections
 * from the same IP, and if there is some address wth
 * multiple connections, we should kill that first.
 *
 * As it is, we just "randomly" kill 25% of the connections,
 * and our pseudo-random generator sucks too. I have no
 * shame.
 *
 * Really, this is just a place-holder for a _real_ algorithm.
 */
static void kill_some_children(int signo, unsigned start, unsigned stop)
{
	start %= MAX_CHILDREN;
	stop %= MAX_CHILDREN;
	while (start != stop) {
		if (!(start & 3))
			kill(live_child[start].pid, signo);
		start = (start + 1) % MAX_CHILDREN;
	}
}

static void check_max_connections(void)
{
	for (;;) {
		int active;
		unsigned spawned, reaped, deleted;

		spawned = children_spawned;
		reaped = children_reaped;
		deleted = children_deleted;

		while (deleted < reaped) {
			pid_t pid = dead_child[deleted % MAX_CHILDREN];
			remove_child(pid, deleted, spawned);
			deleted++;
		}
		children_deleted = deleted;

		active = spawned - deleted;
		if (active <= max_connections)
			break;

		/* Kill some unstarted connections with SIGTERM */
		kill_some_children(SIGTERM, deleted, spawned);
		if (active <= max_connections << 1)
			break;

		/* If the SIGTERM thing isn't helping use SIGKILL */
		kill_some_children(SIGKILL, deleted, spawned);
		sleep(1);
	}
}

static void handle(int incoming, struct sockaddr *addr, int addrlen)
{
	pid_t pid = fork();

	if (pid) {
		unsigned idx;

		close(incoming);
		if (pid < 0)
			return;

		idx = children_spawned % MAX_CHILDREN;
		children_spawned++;
		add_child(idx, pid, addr, addrlen);

		check_max_connections();
		return;
	}

	dup2(incoming, 0);
	dup2(incoming, 1);
	close(incoming);

	exit(execute(addr));
}

static void child_handler(int signo)
{
	for (;;) {
		int status;
		pid_t pid = waitpid(-1, &status, WNOHANG);

		if (pid > 0) {
			unsigned reaped = children_reaped;
			dead_child[reaped % MAX_CHILDREN] = pid;
			children_reaped = reaped + 1;
			/* XXX: Custom logging, since we don't wanna getpid() */
			if (verbose) {
				char *dead = "";
				if (!WIFEXITED(status) || WEXITSTATUS(status) > 0)
					dead = " (with error)";
				if (log_syslog)
					syslog(LOG_INFO, "[%d] Disconnected%s", pid, dead);
				else
					fprintf(stderr, "[%d] Disconnected%s\n", pid, dead);
			}
			continue;
		}
		break;
	}
}

static int set_reuse_addr(int sockfd)
{
	int on = 1;

	if (!reuseaddr)
		return 0;
	return setsockopt(sockfd, SOL_SOCKET, SO_REUSEADDR,
			  &on, sizeof(on));
}

#ifndef NO_IPV6

static int socksetup(int port, int **socklist_p)
{
	int socknum = 0, *socklist = NULL;
	int maxfd = -1;
	char pbuf[NI_MAXSERV];

	struct addrinfo hints, *ai0, *ai;
	int gai;

	sprintf(pbuf, "%d", port);
	memset(&hints, 0, sizeof(hints));
	hints.ai_family = AF_UNSPEC;
	hints.ai_socktype = SOCK_STREAM;
	hints.ai_protocol = IPPROTO_TCP;
	hints.ai_flags = AI_PASSIVE;

	gai = getaddrinfo(NULL, pbuf, &hints, &ai0);
	if (gai)
		die("getaddrinfo() failed: %s\n", gai_strerror(gai));

	for (ai = ai0; ai; ai = ai->ai_next) {
		int sockfd;
		int *newlist;

		sockfd = socket(ai->ai_family, ai->ai_socktype, ai->ai_protocol);
		if (sockfd < 0)
			continue;
		if (sockfd >= FD_SETSIZE) {
			error("too large socket descriptor.");
			close(sockfd);
			continue;
		}

#ifdef IPV6_V6ONLY
		if (ai->ai_family == AF_INET6) {
			int on = 1;
			setsockopt(sockfd, IPPROTO_IPV6, IPV6_V6ONLY,
				   &on, sizeof(on));
			/* Note: error is not fatal */
		}
#endif

		if (set_reuse_addr(sockfd)) {
			close(sockfd);
			continue;
		}

		if (bind(sockfd, ai->ai_addr, ai->ai_addrlen) < 0) {
			close(sockfd);
			continue;	/* not fatal */
		}
		if (listen(sockfd, 5) < 0) {
			close(sockfd);
			continue;	/* not fatal */
		}

		newlist = realloc(socklist, sizeof(int) * (socknum + 1));
		if (!newlist)
			die("memory allocation failed: %s", strerror(errno));

		socklist = newlist;
		socklist[socknum++] = sockfd;

		if (maxfd < sockfd)
			maxfd = sockfd;
	}

	freeaddrinfo(ai0);

	*socklist_p = socklist;
	return socknum;
}

#else /* NO_IPV6 */

static int socksetup(int port, int **socklist_p)
{
	struct sockaddr_in sin;
	int sockfd;

	sockfd = socket(AF_INET, SOCK_STREAM, 0);
	if (sockfd < 0)
		return 0;

	memset(&sin, 0, sizeof sin);
	sin.sin_family = AF_INET;
	sin.sin_addr.s_addr = htonl(INADDR_ANY);
	sin.sin_port = htons(port);

	if (set_reuse_addr(sockfd)) {
		close(sockfd);
		return 0;
	}

	if ( bind(sockfd, (struct sockaddr *)&sin, sizeof sin) < 0 ) {
		close(sockfd);
		return 0;
	}

	if (listen(sockfd, 5) < 0) {
		close(sockfd);
		return 0;
	}

	*socklist_p = xmalloc(sizeof(int));
	**socklist_p = sockfd;
	return 1;
}

#endif

static int service_loop(int socknum, int *socklist)
{
	struct pollfd *pfd;
	int i;

	pfd = xcalloc(socknum, sizeof(struct pollfd));

	for (i = 0; i < socknum; i++) {
		pfd[i].fd = socklist[i];
		pfd[i].events = POLLIN;
	}

	signal(SIGCHLD, child_handler);

	for (;;) {
		int i;

		if (poll(pfd, socknum, -1) < 0) {
			if (errno != EINTR) {
				error("poll failed, resuming: %s",
				      strerror(errno));
				sleep(1);
			}
			continue;
		}

		for (i = 0; i < socknum; i++) {
			if (pfd[i].revents & POLLIN) {
				struct sockaddr_storage ss;
				unsigned int sslen = sizeof(ss);
				int incoming = accept(pfd[i].fd, (struct sockaddr *)&ss, &sslen);
				if (incoming < 0) {
					switch (errno) {
					case EAGAIN:
					case EINTR:
					case ECONNABORTED:
						continue;
					default:
						die("accept returned %s", strerror(errno));
					}
				}
				handle(incoming, (struct sockaddr *)&ss, sslen);
			}
		}
	}
}

static int serve(int port)
{
	int socknum, *socklist;

	socknum = socksetup(port, &socklist);
	if (socknum == 0)
		die("unable to allocate any listen sockets on port %u", port);

	return service_loop(socknum, socklist);
}

int main(int argc, char **argv)
{
	int port = DEFAULT_GIT_PORT;
	int inetd_mode = 0;
	int i;

	for (i = 1; i < argc; i++) {
		char *arg = argv[i];

		if (!strncmp(arg, "--port=", 7)) {
			char *end;
			unsigned long n;
			n = strtoul(arg+7, &end, 0);
			if (arg[7] && !*end) {
				port = n;
				continue;
			}
		}
		if (!strcmp(arg, "--inetd")) {
			inetd_mode = 1;
			log_syslog = 1;
			continue;
		}
		if (!strcmp(arg, "--verbose")) {
			verbose = 1;
			continue;
		}
		if (!strcmp(arg, "--syslog")) {
			log_syslog = 1;
			continue;
		}
		if (!strcmp(arg, "--export-all")) {
			export_all_trees = 1;
			continue;
		}
		if (!strncmp(arg, "--timeout=", 10)) {
			timeout = atoi(arg+10);
			continue;
		}
		if (!strncmp(arg, "--init-timeout=", 15)) {
			init_timeout = atoi(arg+15);
			continue;
		}
		if (!strcmp(arg, "--strict-paths")) {
			strict_paths = 1;
			continue;
		}
		if (!strncmp(arg, "--base-path=", 12)) {
			base_path = arg+12;
			continue;
		}
		if (!strcmp(arg, "--reuseaddr")) {
			reuseaddr = 1;
			continue;
		}
		if (!strcmp(arg, "--user-path")) {
			user_path = "";
			continue;
		}
		if (!strncmp(arg, "--user-path=", 12)) {
			user_path = arg + 12;
			continue;
		}
		if (!strcmp(arg, "--")) {
			ok_paths = &argv[i+1];
			break;
		} else if (arg[0] != '-') {
			ok_paths = &argv[i];
			break;
		}

		usage(daemon_usage);
	}

	if (log_syslog)
		openlog("git-daemon", 0, LOG_DAEMON);

	if (strict_paths && (!ok_paths || !*ok_paths)) {
		if (!inetd_mode)
			die("git-daemon: option --strict-paths requires a whitelist");

		logerror("option --strict-paths requires a whitelist");
		exit (1);
	}

	if (inetd_mode) {
		struct sockaddr_storage ss;
		struct sockaddr *peer = (struct sockaddr *)&ss;
		socklen_t slen = sizeof(ss);

		fclose(stderr); //FIXME: workaround

		if (getpeername(0, peer, &slen))
			peer = NULL;

		return execute(peer);
	}

	return serve(port);
}