/*

 * A fast client for Mercurial command server

 *

 * Copyright (c) 2011 Yuya Nishihara <yuya@tcha.org>

 *

 * This software may be used and distributed according to the terms of the

 * GNU General Public License version 2 or any later version.

 */

#include <assert.h>

#include <errno.h>

#include <fcntl.h>

#include <signal.h>

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <sys/file.h>

#include <sys/stat.h>

#include <sys/types.h>

#include <sys/un.h>

#include <sys/wait.h>

#include <time.h>

#include <unistd.h>

#include "hgclient.h"

#include "util.h"

#ifndef UNIX_PATH_MAX

#define UNIX_PATH_MAX (sizeof(((struct sockaddr_un *)NULL)->sun_path))

#endif

struct cmdserveropts {

	char sockname[UNIX_PATH_MAX];

	char redirectsockname[UNIX_PATH_MAX];

	char lockfile[UNIX_PATH_MAX];

	size_t argsize;

	const char **args;

	int lockfd;

};

static void initcmdserveropts(struct cmdserveropts *opts) {

	memset(opts, 0, sizeof(struct cmdserveropts));

	opts->lockfd = -1;

}

static void freecmdserveropts(struct cmdserveropts *opts) {

	free(opts->args);

	opts->args = NULL;

	opts->argsize = 0;

}

/*

 * Test if an argument is a sensitive flag that should be passed to the server.

 * Return 0 if not, otherwise the number of arguments starting from the current

 * one that should be passed to the server.

 */

static size_t testsensitiveflag(const char *arg)

{

	static const struct {

		const char *name;

		size_t narg;

	} flags[] = {

		{"--config", 1},

		{"--cwd", 1},

		{"--repo", 1},

		{"--repository", 1},

		{"--traceback", 0},

		{"-R", 1},

	};

	size_t i;

	for (i = 0; i < sizeof(flags) / sizeof(flags[0]); ++i) {

		size_t len = strlen(flags[i].name);

		size_t narg = flags[i].narg;

		if (memcmp(arg, flags[i].name, len) == 0) {

			if (arg[len] == '\0') {  /* --flag (value) */

				return narg + 1;

			} else if (arg[len] == '=' && narg > 0) {  /* --flag=value */

				return 1;

			} else if (flags[i].name[1] != '-') {  /* short flag */

				return 1;

			}

		}

	}

	return 0;

}

/*

 * Parse argv[] and put sensitive flags to opts->args

 */

static void setcmdserverargs(struct cmdserveropts *opts,

			     int argc, const char *argv[])

{

	size_t i, step;

	opts->argsize = 0;

	for (i = 0, step = 1; i < (size_t)argc; i += step, step = 1) {

		if (!argv[i])

			continue;  /* pass clang-analyse */

		if (strcmp(argv[i], "--") == 0)

			break;

		size_t n = testsensitiveflag(argv[i]);

		if (n == 0 || i + n > (size_t)argc)

			continue;

		opts->args = reallocx(opts->args,

				      (n + opts->argsize) * sizeof(char *));

		memcpy(opts->args + opts->argsize, argv + i,

		       sizeof(char *) * n);

		opts->argsize += n;

		step = n;

	}

}

static void preparesockdir(const char *sockdir)

{

	int r;

	r = mkdir(sockdir, 0700);

	if (r < 0 && errno != EEXIST)

		abortmsg("cannot create sockdir %s (errno = %d)",

			 sockdir, errno);

	struct stat st;

	r = lstat(sockdir, &st);

	if (r < 0)

		abortmsg("cannot stat %s (errno = %d)", sockdir, errno);

	if (!S_ISDIR(st.st_mode))

		abortmsg("cannot create sockdir %s (file exists)", sockdir);

	if (st.st_uid != geteuid() || st.st_mode & 0077)

		abortmsg("insecure sockdir %s", sockdir);

}

static void setcmdserveropts(struct cmdserveropts *opts)

{

	int r;

	char sockdir[UNIX_PATH_MAX];

	const char *envsockname = getenv("CHGSOCKNAME");

	if (!envsockname) {

		/* by default, put socket file in secure directory

		 * (permission of socket file may be ignored on some Unices) */

		const char *tmpdir = getenv("TMPDIR");

		if (!tmpdir)

			tmpdir = "/tmp";

		r = snprintf(sockdir, sizeof(sockdir), "%s/chg%d",

			     tmpdir, geteuid());

		if (r < 0 || (size_t)r >= sizeof(sockdir))

			abortmsg("too long TMPDIR (r = %d)", r);

		preparesockdir(sockdir);

	}

	const char *basename = (envsockname) ? envsockname : sockdir;

	const char *sockfmt = (envsockname) ? "%s" : "%s/server";

	const char *lockfmt = (envsockname) ? "%s.lock" : "%s/lock";

	r = snprintf(opts->sockname, sizeof(opts->sockname), sockfmt, basename);

	if (r < 0 || (size_t)r >= sizeof(opts->sockname))

		abortmsg("too long TMPDIR or CHGSOCKNAME (r = %d)", r);

	r = snprintf(opts->lockfile, sizeof(opts->lockfile), lockfmt, basename);

	if (r < 0 || (size_t)r >= sizeof(opts->lockfile))

		abortmsg("too long TMPDIR or CHGSOCKNAME (r = %d)", r);

}

/*

 * Acquire a file lock that indicates a client is trying to start and connect

 * to a server, before executing a command. The lock is released upon exit or

 * explicit unlock. Will block if the lock is held by another process.

 */

static void lockcmdserver(struct cmdserveropts *opts)

{

	if (opts->lockfd == -1) {

		opts->lockfd = open(opts->lockfile, O_RDWR | O_CREAT | O_NOFOLLOW, 0600);

		if (opts->lockfd == -1)

			abortmsg("cannot create lock file %s", opts->lockfile);

	}

	int r = flock(opts->lockfd, LOCK_EX);

	if (r == -1)

		abortmsg("cannot acquire lock");

}

/*

 * Release the file lock held by calling lockcmdserver. Will do nothing if

 * lockcmdserver is not called.

 */

static void unlockcmdserver(struct cmdserveropts *opts)

{

	if (opts->lockfd == -1)

		return;

	flock(opts->lockfd, LOCK_UN);

	close(opts->lockfd);

	opts->lockfd = -1;

}

static const char *gethgcmd(void)

{

	static const char *hgcmd = NULL;

	if (!hgcmd) {

		hgcmd = getenv("CHGHG");

		if (!hgcmd || hgcmd[0] == '\0')

			hgcmd = getenv("HG");

		if (!hgcmd || hgcmd[0] == '\0')

			hgcmd = "hg";

	}

	return hgcmd;

}

static void execcmdserver(const struct cmdserveropts *opts)

{

	const char *hgcmd = gethgcmd();

	const char *baseargv[] = {

		hgcmd,

		"serve",

		"--cmdserver", "chgunix",

		"--address", opts->sockname,

		"--daemon-postexec", "chdir:/",

		"--config", "extensions.chgserver=",

	};

	size_t baseargvsize = sizeof(baseargv) / sizeof(baseargv[0]);

	size_t argsize = baseargvsize + opts->argsize + 1;

	const char **argv = mallocx(sizeof(char *) * argsize);

	memcpy(argv, baseargv, sizeof(baseargv));

	memcpy(argv + baseargvsize, opts->args, sizeof(char *) * opts->argsize);

	argv[argsize - 1] = NULL;

	if (putenv("CHGINTERNALMARK=") != 0)

		abortmsg("failed to putenv (errno = %d)", errno);

	if (execvp(hgcmd, (char **)argv) < 0)

		abortmsg("failed to exec cmdserver (errno = %d)", errno);

	free(argv);

}

/* Retry until we can connect to the server. Give up after some time. */

static hgclient_t *retryconnectcmdserver(struct cmdserveropts *opts, pid_t pid)

{

	static const struct timespec sleepreq = {0, 10 * 1000000};

	int pst = 0;

	for (unsigned int i = 0; i < 10 * 100; i++) {

		hgclient_t *hgc = hgc_open(opts->sockname);

		if (hgc)

			return hgc;

		if (pid > 0) {

			/* collect zombie if child process fails to start */

			int r = waitpid(pid, &pst, WNOHANG);

			if (r != 0)

				goto cleanup;

		}

		nanosleep(&sleepreq, NULL);

	}

	abortmsg("timed out waiting for cmdserver %s", opts->sockname);

	return NULL;

cleanup:

	if (WIFEXITED(pst)) {

		debugmsg("cmdserver exited with status %d", WEXITSTATUS(pst));

		exit(WEXITSTATUS(pst));

	} else if (WIFSIGNALED(pst)) {

		abortmsg("cmdserver killed by signal %d", WTERMSIG(pst));

	} else {

		abortmsg("error white waiting cmdserver");

	}

	return NULL;

}

/* Connect to a cmdserver. Will start a new server on demand. */

static hgclient_t *connectcmdserver(struct cmdserveropts *opts)

{

	const char *sockname = opts->redirectsockname[0] ?

		opts->redirectsockname : opts->sockname;

	hgclient_t *hgc = hgc_open(sockname);

	if (hgc)

		return hgc;

	lockcmdserver(opts);

	hgc = hgc_open(sockname);

	if (hgc) {

		unlockcmdserver(opts);

		debugmsg("cmdserver is started by another process");

		return hgc;

	}

	/* prevent us from being connected to an outdated server: we were

	 * told by a server to redirect to opts->redirectsockname and that

	 * address does not work. we do not want to connect to the server

	 * again because it will probably tell us the same thing. */

	if (sockname == opts->redirectsockname)

		unlink(opts->sockname);

	debugmsg("start cmdserver at %s", opts->sockname);

	pid_t pid = fork();

	if (pid < 0)

		abortmsg("failed to fork cmdserver process");

	if (pid == 0) {

		/* do not leak lockfd to hg */

		close(opts->lockfd);

		/* bypass uisetup() of pager extension */

		int nullfd = open("/dev/null", O_WRONLY);

		if (nullfd >= 0) {

			dup2(nullfd, fileno(stdout));

			close(nullfd);

		}

		execcmdserver(opts);

	} else {

		hgc = retryconnectcmdserver(opts, pid);

	}

	unlockcmdserver(opts);

	return hgc;

}

static void killcmdserver(const struct cmdserveropts *opts)

{

	/* resolve config hash */

	char *resolvedpath = realpath(opts->sockname, NULL);

	if (resolvedpath) {

		unlink(resolvedpath);

		free(resolvedpath);

	}

}

static pid_t peerpid = 0;

static void forwardsignal(int sig)

{

	assert(peerpid > 0);

	if (kill(peerpid, sig) < 0)

		abortmsg("cannot kill %d (errno = %d)", peerpid, errno);

	debugmsg("forward signal %d", sig);

}

static void handlestopsignal(int sig)

{

	sigset_t unblockset, oldset;

	struct sigaction sa, oldsa;

	if (sigemptyset(&unblockset) < 0)

		goto error;

	if (sigaddset(&unblockset, sig) < 0)

		goto error;

	memset(&sa, 0, sizeof(sa));

	sa.sa_handler = SIG_DFL;

	sa.sa_flags = SA_RESTART;

	if (sigemptyset(&sa.sa_mask) < 0)

		goto error;

	forwardsignal(sig);

	if (raise(sig) < 0)  /* resend to self */

		goto error;

	if (sigaction(sig, &sa, &oldsa) < 0)

		goto error;

	if (sigprocmask(SIG_UNBLOCK, &unblockset, &oldset) < 0)

		goto error;

	/* resent signal will be handled before sigprocmask() returns */

	if (sigprocmask(SIG_SETMASK, &oldset, NULL) < 0)

		goto error;

	if (sigaction(sig, &oldsa, NULL) < 0)

		goto error;

	return;

error:

	abortmsg("failed to handle stop signal (errno = %d)", errno);

}

static void setupsignalhandler(pid_t pid)

{

	if (pid <= 0)

		return;

	peerpid = pid;

	struct sigaction sa;

	memset(&sa, 0, sizeof(sa));

	sa.sa_handler = forwardsignal;

	sa.sa_flags = SA_RESTART;

	if (sigemptyset(&sa.sa_mask) < 0)

		goto error;

	if (sigaction(SIGHUP, &sa, NULL) < 0)

		goto error;

	if (sigaction(SIGINT, &sa, NULL) < 0)

		goto error;

	/* terminate frontend by double SIGTERM in case of server freeze */

	sa.sa_flags |= SA_RESETHAND;