/*

 * 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 "procutil.h"

#include "util.h"

#ifndef PATH_MAX

#define PATH_MAX 4096

#endif

struct cmdserveropts {

	char sockname[PATH_MAX];

	char initsockname[PATH_MAX];

	char redirectsockname[PATH_MAX];

	size_t argsize;

	const char **args;

};

static void initcmdserveropts(struct cmdserveropts *opts) {

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

}

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)

		abortmsgerrno("cannot create sockdir %s", sockdir);

	struct stat st;

	r = lstat(sockdir, &st);

	if (r < 0)

		abortmsgerrno("cannot stat %s", sockdir);

	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);

}

/*

 * Check if a socket directory exists and is only owned by the current user.

 * Return 1 if so, 0 if not. This is used to check if XDG_RUNTIME_DIR can be

 * used or not. According to the specification [1], XDG_RUNTIME_DIR should be

 * ignored if the directory is not owned by the user with mode 0700.

 * [1]: https://standards.freedesktop.org/basedir-spec/basedir-spec-latest.html

 */

static int checkruntimedir(const char *sockdir)

{

	struct stat st;

	int r = lstat(sockdir, &st);

	if (r < 0) /* ex. does not exist */

		return 0;

	if (!S_ISDIR(st.st_mode)) /* ex. is a file, not a directory */

		return 0;

	return st.st_uid == geteuid() && (st.st_mode & 0777) == 0700;

}

static void getdefaultsockdir(char sockdir[], size_t size)

{

	/* by default, put socket file in secure directory

	 * (${XDG_RUNTIME_DIR}/chg, or /${TMPDIR:-tmp}/chg$UID)

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

	const char *runtimedir = getenv("XDG_RUNTIME_DIR");

	int r;

	if (runtimedir && checkruntimedir(runtimedir)) {

		r = snprintf(sockdir, size, "%s/chg", runtimedir);

	} else {

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

		if (!tmpdir)

			tmpdir = "/tmp";

		r = snprintf(sockdir, size, "%s/chg%d", tmpdir, geteuid());

	}

	if (r < 0 || (size_t)r >= size)

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

}

static void setcmdserveropts(struct cmdserveropts *opts)

{

	int r;

	char sockdir[PATH_MAX];

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

	if (!envsockname) {

		getdefaultsockdir(sockdir, sizeof(sockdir));

		preparesockdir(sockdir);

	}

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

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

	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->initsockname, sizeof(opts->initsockname),

			"%s.%u", opts->sockname, (unsigned)getpid());

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

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

}

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')

#ifdef HGPATH

			hgcmd = (HGPATH);

#else

			hgcmd = "hg";

#endif

	}

	return hgcmd;

}

static void execcmdserver(const struct cmdserveropts *opts)

{

	const char *hgcmd = gethgcmd();

	const char *baseargv[] = {

		hgcmd,

		"serve",

		"--cmdserver", "chgunix",

		"--address", opts->initsockname,

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

	};

	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)

		abortmsgerrno("failed to putenv");

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

		abortmsgerrno("failed to exec cmdserver");

	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;

	debugmsg("try connect to %s repeatedly", opts->initsockname);

	unsigned int timeoutsec = 60;  /* default: 60 seconds */

	const char *timeoutenv = getenv("CHGTIMEOUT");

	if (timeoutenv)

		sscanf(timeoutenv, "%u", &timeoutsec);

	for (unsigned int i = 0; !timeoutsec || i < timeoutsec * 100; i++) {

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

		if (hgc) {

			debugmsg("rename %s to %s", opts->initsockname,

					opts->sockname);

			int r = rename(opts->initsockname, opts->sockname);

			if (r != 0)

				abortmsgerrno("cannot rename");

			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->initsockname);

	return NULL;

cleanup:

	if (WIFEXITED(pst)) {

		if (WEXITSTATUS(pst) == 0)

			abortmsg("could not connect to cmdserver "

				 "(exited with status 0)");

		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 while waiting for 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;

	debugmsg("try connect to %s", sockname);

	hgclient_t *hgc = hgc_open(sockname);

	if (hgc)

		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->initsockname);

	pid_t pid = fork();

	if (pid < 0)

		abortmsg("failed to fork cmdserver process");

	if (pid == 0) {

		execcmdserver(opts);

	} else {

		hgc = retryconnectcmdserver(opts, pid);

	}

	return hgc;

}

static void killcmdserver(const struct cmdserveropts *opts)

{

	/* resolve config hash */

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

	if (resolvedpath) {

		unlink(resolvedpath);

		free(resolvedpath);

	}

}

/* Run instructions sent from the server like unlink and set redirect path

 * Return 1 if reconnect is needed, otherwise 0 */

static int runinstructions(struct cmdserveropts *opts, const char **insts)

{

	int needreconnect = 0;

	if (!insts)

		return needreconnect;

	assert(insts);

	opts->redirectsockname[0] = '\0';

	const char **pinst;

	for (pinst = insts; *pinst; pinst++) {

		debugmsg("instruction: %s", *pinst);

		if (strncmp(*pinst, "unlink ", 7) == 0) {

			unlink(*pinst + 7);

		} else if (strncmp(*pinst, "redirect ", 9) == 0) {

			int r = snprintf(opts->redirectsockname,

					 sizeof(opts->redirectsockname),

					 "%s", *pinst + 9);

			if (r < 0 || r >= (int)sizeof(opts->redirectsockname))

				abortmsg("redirect path is too long (%d)", r);

			needreconnect = 1;

		} else if (strncmp(*pinst, "exit ", 5) == 0) {

			int n = 0;

			if (sscanf(*pinst + 5, "%d", &n) != 1)

				abortmsg("cannot read the exit code");

			exit(n);

		} else if (strcmp(*pinst, "reconnect") == 0) {

			needreconnect = 1;

		} else {

			abortmsg("unknown instruction: %s", *pinst);

		}

	}

	return needreconnect;

}

/*

 * Test whether the command is unsupported or not. This is not designed to

 * cover all cases. But it's fast, does not depend on the server and does

 * not return false positives.

 */

static int isunsupported(int argc, const char *argv[])

{

	enum {

		SERVE = 1,

		DAEMON = 2,

		SERVEDAEMON = SERVE | DAEMON,

		TIME = 4,

	};

	unsigned int state = 0;

	int i;

	for (i = 0; i < argc; ++i) {

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