credential-cache--daemon.c - jrn/git - Git at Google

 #include "cache.h"
 #include "tempfile.h"
 #include "credential.h"
 #include "unix-socket.h"
 #include "parse-options.h"

 static struct tempfile socket_file;

 struct credential_cache_entry {
 	struct credential item;
 	unsigned long expiration;
 };
 static struct credential_cache_entry *entries;
 static int entries_nr;
 static int entries_alloc;

 static void cache_credential(struct credential *c, int timeout)
 {
 	struct credential_cache_entry *e;

 	ALLOC_GROW(entries, entries_nr + 1, entries_alloc);
 	e = &entries[entries_nr++];

 	/* take ownership of pointers */
 	memcpy(&e->item, c, sizeof(*c));
 	memset(c, 0, sizeof(*c));
 	e->expiration = time(NULL) + timeout;
 }

 static struct credential_cache_entry *lookup_credential(const struct credential *c)
 {
 	int i;
 	for (i = 0; i < entries_nr; i++) {
 		struct credential *e = &entries[i].item;
 		if (credential_match(c, e))
 			return &entries[i];
 	}
 	return NULL;
 }

 static void remove_credential(const struct credential *c)
 {
 	struct credential_cache_entry *e;

 	e = lookup_credential(c);
 	if (e)
 		e->expiration = 0;
 }

 static int check_expirations(void)
 {
 	static unsigned long wait_for_entry_until;
 	int i = 0;
 	unsigned long now = time(NULL);
 	unsigned long next = (unsigned long)-1;

 	/*
 	 * Initially give the client 30 seconds to actually contact us
 	 * and store a credential before we decide there's no point in
 	 * keeping the daemon around.
 	 */
 	if (!wait_for_entry_until)
 		wait_for_entry_until = now + 30;

 	while (i < entries_nr) {
 		if (entries[i].expiration <= now) {
 			entries_nr--;
 			credential_clear(&entries[i].item);
 			if (i != entries_nr)
 				memcpy(&entries[i], &entries[entries_nr], sizeof(*entries));
 			/*
 			 * Stick around 30 seconds in case a new credential
 			 * shows up (e.g., because we just removed a failed
 			 * one, and we will soon get the correct one).
 			 */
 			wait_for_entry_until = now + 30;
 		}
 		else {
 			if (entries[i].expiration < next)
 				next = entries[i].expiration;
 			i++;
 		}
 	}

 	if (!entries_nr) {
 		if (wait_for_entry_until <= now)
 			return 0;
 		next = wait_for_entry_until;
 	}

 	return next - now;
 }

 static int read_request(FILE *fh, struct credential *c,
 			struct strbuf *action, int *timeout) {
 	static struct strbuf item = STRBUF_INIT;
 	const char *p;

 	strbuf_getline_lf(&item, fh);
 	if (!skip_prefix(item.buf, "action=", &p))
 		return error("client sent bogus action line: %s", item.buf);
 	strbuf_addstr(action, p);

 	strbuf_getline_lf(&item, fh);
 	if (!skip_prefix(item.buf, "timeout=", &p))
 		return error("client sent bogus timeout line: %s", item.buf);
 	*timeout = atoi(p);

 	if (credential_read(c, fh) < 0)
 		return -1;
 	return 0;
 }

 static void serve_one_client(FILE *in, FILE *out)
 {
 	struct credential c = CREDENTIAL_INIT;
 	struct strbuf action = STRBUF_INIT;
 	int timeout = -1;

 	if (read_request(in, &c, &action, &timeout) < 0)
 		/* ignore error */ ;
 	else if (!strcmp(action.buf, "get")) {
 		struct credential_cache_entry *e = lookup_credential(&c);
 		if (e) {
 			fprintf(out, "username=%s\n", e->item.username);
 			fprintf(out, "password=%s\n", e->item.password);
 		}
 	}
 	else if (!strcmp(action.buf, "exit")) {
 		/*
 		 * It's important that we clean up our socket first, and then
 		 * signal the client only once we have finished the cleanup.
 		 * Calling exit() directly does this, because we clean up in
 		 * our atexit() handler, and then signal the client when our
 		 * process actually ends, which closes the socket and gives
 		 * them EOF.
 		 */
 		exit(0);
 	}
 	else if (!strcmp(action.buf, "erase"))
 		remove_credential(&c);
 	else if (!strcmp(action.buf, "store")) {
 		if (timeout < 0)
 			warning("cache client didn't specify a timeout");
 		else if (!c.username || !c.password)
 			warning("cache client gave us a partial credential");
 		else {
 			remove_credential(&c);
 			cache_credential(&c, timeout);
 		}
 	}
 	else
 		warning("cache client sent unknown action: %s", action.buf);

 	credential_clear(&c);
 	strbuf_release(&action);
 }

 static int serve_cache_loop(int fd)
 {
 	struct pollfd pfd;
 	unsigned long wakeup;

 	wakeup = check_expirations();
 	if (!wakeup)
 		return 0;

 	pfd.fd = fd;
 	pfd.events = POLLIN;
 	if (poll(&pfd, 1, 1000 * wakeup) < 0) {
 		if (errno != EINTR)
 			die_errno("poll failed");
 		return 1;
 	}

 	if (pfd.revents & POLLIN) {
 		int client, client2;
 		FILE *in, *out;

 		client = accept(fd, NULL, NULL);
 		if (client < 0) {
 			warning("accept failed: %s", strerror(errno));
 			return 1;
 		}
 		client2 = dup(client);
 		if (client2 < 0) {
 			warning("dup failed: %s", strerror(errno));
 			close(client);
 			return 1;
 		}

 		in = xfdopen(client, "r");
 		out = xfdopen(client2, "w");
 		serve_one_client(in, out);
 		fclose(in);
 		fclose(out);
 	}
 	return 1;
 }

 static void serve_cache(const char *socket_path, int debug)
 {
 	int fd;

 	fd = unix_stream_listen(socket_path);
 	if (fd < 0)
 		die_errno("unable to bind to '%s'", socket_path);

 	printf("ok\n");
 	fclose(stdout);
 	if (!debug) {
 		if (!freopen("/dev/null", "w", stderr))
 			die_errno("unable to point stderr to /dev/null");
 	}

 	while (serve_cache_loop(fd))
 		; /* nothing */

 	close(fd);
 }

 static const char permissions_advice[] =
 "The permissions on your socket directory are too loose; other\n"
 "users may be able to read your cached credentials. Consider running:\n"
 "\n"
 "	chmod 0700 %s";
 static void init_socket_directory(const char *path)
 {
 	struct stat st;
 	char *path_copy = xstrdup(path);
 	char *dir = dirname(path_copy);

 	if (!stat(dir, &st)) {
 		if (st.st_mode & 077)
 			die(permissions_advice, dir);
 	} else {
 		/*
 		 * We must be sure to create the directory with the correct mode,
 		 * not just chmod it after the fact; otherwise, there is a race
 		 * condition in which somebody can chdir to it, sleep, then try to open
 		 * our protected socket.
 		 */
 		if (safe_create_leading_directories_const(dir) < 0)
 			die_errno("unable to create directories for '%s'", dir);
 		if (mkdir(dir, 0700) < 0)
 			die_errno("unable to mkdir '%s'", dir);
 	}

 	if (chdir(dir))
 		/*
 		 * We don't actually care what our cwd is; we chdir here just to
 		 * be a friendly daemon and avoid tying up our original cwd.
 		 * If this fails, it's OK to just continue without that benefit.
 		 */
 		;

 	free(path_copy);
 }

 int main(int argc, const char **argv)
 {
 	const char *socket_path;
 	int ignore_sighup = 0;
 	static const char *usage[] = {
 		"git-credential-cache--daemon [opts] <socket_path>",
 		NULL
 	};
 	int debug = 0;
 	const struct option options[] = {
 		OPT_BOOL(0, "debug", &debug,
 			 N_("print debugging messages to stderr")),
 		OPT_END()
 	};

 	git_config_get_bool("credentialcache.ignoresighup", &ignore_sighup);

 	argc = parse_options(argc, argv, NULL, options, usage, 0);
 	socket_path = argv[0];

 	if (!socket_path)
 		usage_with_options(usage, options);

 	if (!is_absolute_path(socket_path))
 		die("socket directory must be an absolute path");

 	init_socket_directory(socket_path);
 	register_tempfile(&socket_file, socket_path);

 	if (ignore_sighup)
 		signal(SIGHUP, SIG_IGN);

 	serve_cache(socket_path, debug);
 	delete_tempfile(&socket_file);

 	return 0;
 }
	#include "cache.h"
	#include "tempfile.h"
	#include "credential.h"
	#include "unix-socket.h"
	#include "parse-options.h"

	static struct tempfile socket_file;

	struct credential_cache_entry {
	struct credential item;
	unsigned long expiration;
	};
	static struct credential_cache_entry *entries;
	static int entries_nr;
	static int entries_alloc;

	static void cache_credential(struct credential *c, int timeout)
	{
	struct credential_cache_entry *e;

	ALLOC_GROW(entries, entries_nr + 1, entries_alloc);
	e = &entries[entries_nr++];

	/* take ownership of pointers */
	memcpy(&e->item, c, sizeof(*c));
	memset(c, 0, sizeof(*c));
	e->expiration = time(NULL) + timeout;
	}

	static struct credential_cache_entry lookup_credential(const struct credential c)
	{
	int i;
	for (i = 0; i < entries_nr; i++) {
	struct credential *e = &entries[i].item;
	if (credential_match(c, e))
	return &entries[i];
	}
	return NULL;
	}

	static void remove_credential(const struct credential *c)
	{
	struct credential_cache_entry *e;

	e = lookup_credential(c);
	if (e)
	e->expiration = 0;
	}

	static int check_expirations(void)
	{
	static unsigned long wait_for_entry_until;
	int i = 0;
	unsigned long now = time(NULL);
	unsigned long next = (unsigned long)-1;

	/*
	* Initially give the client 30 seconds to actually contact us
	* and store a credential before we decide there's no point in
	* keeping the daemon around.
	*/
	if (!wait_for_entry_until)
	wait_for_entry_until = now + 30;

	while (i < entries_nr) {
	if (entries[i].expiration <= now) {
	entries_nr--;
	credential_clear(&entries[i].item);
	if (i != entries_nr)
	memcpy(&entries[i], &entries[entries_nr], sizeof(*entries));
	/*
	* Stick around 30 seconds in case a new credential
	* shows up (e.g., because we just removed a failed
	* one, and we will soon get the correct one).
	*/
	wait_for_entry_until = now + 30;
	}
	else {
	if (entries[i].expiration < next)
	next = entries[i].expiration;
	i++;
	}
	}

	if (!entries_nr) {
	if (wait_for_entry_until <= now)
	return 0;
	next = wait_for_entry_until;
	}

	return next - now;
	}

	static int read_request(FILE fh, struct credential c,
	struct strbuf action, int timeout) {
	static struct strbuf item = STRBUF_INIT;
	const char *p;

	strbuf_getline_lf(&item, fh);
	if (!skip_prefix(item.buf, "action=", &p))
	return error("client sent bogus action line: %s", item.buf);
	strbuf_addstr(action, p);

	strbuf_getline_lf(&item, fh);
	if (!skip_prefix(item.buf, "timeout=", &p))
	return error("client sent bogus timeout line: %s", item.buf);
	*timeout = atoi(p);

	if (credential_read(c, fh) < 0)
	return -1;
	return 0;
	}

	static void serve_one_client(FILE in, FILE out)
	{
	struct credential c = CREDENTIAL_INIT;
	struct strbuf action = STRBUF_INIT;
	int timeout = -1;

	if (read_request(in, &c, &action, &timeout) < 0)
	/* ignore error */ ;
	else if (!strcmp(action.buf, "get")) {
	struct credential_cache_entry *e = lookup_credential(&c);
	if (e) {
	fprintf(out, "username=%s\n", e->item.username);
	fprintf(out, "password=%s\n", e->item.password);
	}
	}
	else if (!strcmp(action.buf, "exit")) {
	/*
	* It's important that we clean up our socket first, and then
	* signal the client only once we have finished the cleanup.
	* Calling exit() directly does this, because we clean up in
	* our atexit() handler, and then signal the client when our
	* process actually ends, which closes the socket and gives
	* them EOF.
	*/
	exit(0);
	}
	else if (!strcmp(action.buf, "erase"))
	remove_credential(&c);
	else if (!strcmp(action.buf, "store")) {
	if (timeout < 0)
	warning("cache client didn't specify a timeout");
	else if (!c.username \|\| !c.password)
	warning("cache client gave us a partial credential");
	else {
	remove_credential(&c);
	cache_credential(&c, timeout);
	}
	}
	else
	warning("cache client sent unknown action: %s", action.buf);

	credential_clear(&c);
	strbuf_release(&action);
	}

	static int serve_cache_loop(int fd)
	{
	struct pollfd pfd;
	unsigned long wakeup;

	wakeup = check_expirations();
	if (!wakeup)
	return 0;

	pfd.fd = fd;
	pfd.events = POLLIN;
	if (poll(&pfd, 1, 1000 * wakeup) < 0) {
	if (errno != EINTR)
	die_errno("poll failed");
	return 1;
	}

	if (pfd.revents & POLLIN) {
	int client, client2;
	FILE in, out;

	client = accept(fd, NULL, NULL);
	if (client < 0) {
	warning("accept failed: %s", strerror(errno));
	return 1;
	}
	client2 = dup(client);
	if (client2 < 0) {
	warning("dup failed: %s", strerror(errno));
	close(client);
	return 1;
	}

	in = xfdopen(client, "r");
	out = xfdopen(client2, "w");
	serve_one_client(in, out);
	fclose(in);
	fclose(out);
	}
	return 1;
	}

	static void serve_cache(const char *socket_path, int debug)
	{
	int fd;

	fd = unix_stream_listen(socket_path);
	if (fd < 0)
	die_errno("unable to bind to '%s'", socket_path);

	printf("ok\n");
	fclose(stdout);
	if (!debug) {
	if (!freopen("/dev/null", "w", stderr))
	die_errno("unable to point stderr to /dev/null");
	}

	while (serve_cache_loop(fd))
	; /* nothing */

	close(fd);
	}

	static const char permissions_advice[] =
	"The permissions on your socket directory are too loose; other\n"
	"users may be able to read your cached credentials. Consider running:\n"
	"\n"
	" chmod 0700 %s";
	static void init_socket_directory(const char *path)
	{
	struct stat st;
	char *path_copy = xstrdup(path);
	char *dir = dirname(path_copy);

	if (!stat(dir, &st)) {
	if (st.st_mode & 077)
	die(permissions_advice, dir);
	} else {
	/*
	* We must be sure to create the directory with the correct mode,
	* not just chmod it after the fact; otherwise, there is a race
	* condition in which somebody can chdir to it, sleep, then try to open
	* our protected socket.
	*/
	if (safe_create_leading_directories_const(dir) < 0)
	die_errno("unable to create directories for '%s'", dir);
	if (mkdir(dir, 0700) < 0)
	die_errno("unable to mkdir '%s'", dir);
	}

	if (chdir(dir))
	/*
	* We don't actually care what our cwd is; we chdir here just to
	* be a friendly daemon and avoid tying up our original cwd.
	* If this fails, it's OK to just continue without that benefit.
	*/
	;

	free(path_copy);
	}

	int main(int argc, const char **argv)
	{
	const char *socket_path;
	int ignore_sighup = 0;
	static const char *usage[] = {
	"git-credential-cache--daemon [opts] <socket_path>",
	NULL
	};
	int debug = 0;
	const struct option options[] = {
	OPT_BOOL(0, "debug", &debug,
	N_("print debugging messages to stderr")),
	OPT_END()
	};

	git_config_get_bool("credentialcache.ignoresighup", &ignore_sighup);

	argc = parse_options(argc, argv, NULL, options, usage, 0);
	socket_path = argv[0];

	if (!socket_path)
	usage_with_options(usage, options);

	if (!is_absolute_path(socket_path))
	die("socket directory must be an absolute path");

	init_socket_directory(socket_path);
	register_tempfile(&socket_file, socket_path);

	if (ignore_sighup)
	signal(SIGHUP, SIG_IGN);

	serve_cache(socket_path, debug);
	delete_tempfile(&socket_file);

	return 0;
	}