finit/src/exec.c

/* Functions for exec'ing processes
 *
 * Copyright (c) 2008-2010  Claudio Matsuoka <cmatsuoka@gmail.com>
 * Copyright (c) 2008-2023  Joachim Wiberg <troglobit@gmail.com>
 *
 * Permission is hereby granted, free of charge, to any person obtaining a copy
 * of this software and associated documentation files (the "Software"), to deal
 * in the Software without restriction, including without limitation the rights
 * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the Software is
 * furnished to do so, subject to the following conditions:
 *
 * The above copyright notice and this permission notice shall be included in
 * all copies or substantial portions of the Software.
 *
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
 * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
 * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
 * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
 * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
 * THE SOFTWARE.
 */

#include "config.h"		/* Generated by configure script */

#include <err.h>
#include <stdarg.h>
#include <sysexits.h>
#include <sys/ioctl.h>
#include <sys/prctl.h>
#include <sys/wait.h>
#include <sys/ttydefaults.h>	/* Not included by default in musl libc */
#include <termios.h>
#ifdef _LIBITE_LITE
# include <libite/lite.h>
#else
# include <lite/lite.h>
#endif
#include <linux/vt.h>

#include "finit.h"
#include "cgroup.h"
#include "conf.h"
#include "helpers.h"
#include "sig.h"
#include "util.h"
#include "utmp-api.h"

#define NUM_ARGS    16


/* Wait for process completion, returns status of waitpid(2) syscall */
int complete(char *cmd, int pid)
{
	int status = 0;

	if (waitpid(pid, &status, 0) == -1) {
		if (errno == EINTR)
			warnx("Caught unblocked signal waiting for %s, aborting", cmd);
		else if (errno == ECHILD)
			warnx("Caught SIGCHLD waiting for %s, aborting", cmd);
		else
			warnx("Failed starting %s, error %d: %s", cmd, errno, strerror(errno));

		return -1;
	}

	return status;
}

static int do_redirect(void)
{
	FILE *fp;

	fp = fopen("/dev/null", "w");
	if (fp) {
		int fd = fileno(fp);

		dup2(fd, STDIN_FILENO);
		dup2(fd, STDOUT_FILENO);
		dup2(fd, STDERR_FILENO);

		return fclose(fp);
	}

	return -1;
}

/*
 * Run 'cmd' and wait for completion.  If 'log' is not NULL any output
 * from the command is logged with the given string as prefix, use "" to
 * skip.  If 'log' is NULL all output is redirected to /dev/null, which
 * is what this function originally did.
 */
int run(char *cmd, char *log)
{
	char *args[NUM_ARGS + 1] = { 0 };
	int status, result, i = 0;
	char *backup = NULL;
	pid_t pid;

	if (!log) {
		char *arg;

		/* We must create a copy that is possible to modify. */
		backup = arg = strdup(cmd);
		if (!arg)
			return 1;

		/* Split command line into tokens of an argv[] array. */
		args[i++] = strsep(&arg, "\t ");
		while (arg && i < NUM_ARGS) {
			/* Handle run("su -c \"dbus-daemon --system\" messagebus");
			 *   => "su", "-c", "\"dbus-daemon --system\"", "messagebus" */
			if (*arg == '\'' || *arg == '"') {
				char *p, delim[2] = " ";

				delim[0]  = arg[0];
				args[i++] = arg++;
				strsep(&arg, delim);
				 p     = arg - 1;
				*p     = *delim;
				*arg++ = 0;
			} else {
				args[i++] = strsep(&arg, "\t ");
			}
		}
		args[i] = NULL;

		if (i == NUM_ARGS && arg) {
			errx(1, "Command too long: %s", cmd);
			free(backup);
			errno = EOVERFLOW;
			return 1;
		}
	}

	pid = fork();
	if (0 == pid) {
		int rc = EX_OSERR;

		setsid();
		sig_unblock();
		if (!log) {
			do_redirect();
			execvp(args[0], args);
		} else {
			char *pfx = *log ? ": " : "";
			FILE *pp;

			pp = popen(cmd, "r");
			if (pp) {
				char buf[256];

				while (fgets(buf, sizeof(buf), pp)) {
					chomp(buf);
					logit(LOG_NOTICE, "%s%s%s", log, pfx, buf);
				}

				rc = pclose(pp);
			}
		}

		_exit(rc);
	} else if (-1 == pid) {
		err(1, "%s", !log ? args[0] : cmd);
		if (backup)
			free(backup);

		return -1;
	}

	status = complete(args[0], pid);
	if (-1 == status) {
		if (backup)
			free(backup);
		return 1;
	}

	result = WEXITSTATUS(status);
	if (WIFEXITED(status)) {
		dbg("Started '%s' and exit without signal, status: %d", cmd, result);
	} else if (WIFSIGNALED(status)) {
		dbg("Process '%s' terminated by signal %d", cmd, WTERMSIG(status));
		if (!result)
			result = 1; /* Must alert callee the command did not complete successfully.
				     * This is necessary since not all programs trap signals and
				     * change their return code accordingly. --Jocke */
	}

	if (backup)
		free(backup);

	return result;
}

int run_interactive(char *cmd, char *fmt, ...)
{
	int status, oldout = 1, olderr = 2;
	char line[LINE_SIZE];
	FILE *fp;

	if (!cmd) {
		errno = EINVAL;
		return 1;
	}

	if (fmt) {
		va_list ap;

		va_start(ap, fmt);
		printv(fmt, ap);
		va_end(ap);
	}

	/* Redirect output from cmd to a tempfile */
	fp = tempfile();
	if (fp && !debug) {
		oldout = dup(STDOUT_FILENO);
		olderr = dup(STDERR_FILENO);
		dup2(fileno(fp), STDOUT_FILENO);
		dup2(fileno(fp), STDERR_FILENO);
	}

	/* Run cmd ... */
	status = run(cmd, "");

	/* Restore stderr/stdout */
	if (fp && !debug) {
		if (oldout >= 0) {
			dup2(oldout, STDOUT_FILENO);
			close(oldout);
		}
		if (olderr >= 0) {
			dup2(olderr, STDERR_FILENO);
			close(olderr);
		}
	}

	if (fmt)
		print_result(status);

	/* Dump any results of cmd on stderr after we've printed [ OK ] or [FAIL]  */
	if (fp && !debug) {
		size_t len, written;

		rewind(fp);
		do {
			len     = fread(line, 1, sizeof(line), fp);
			written = fwrite(line, len, sizeof(char), stderr);
		} while (len > 0 && written == len);
	}

	if (fp)
		fclose(fp);

	return status;
}

int exec_runtask(char *cmd, char *args[])
{
	char buf[1024] = "";
	char *argv[4] = {
		"sh",
		"-c",
		buf,
		NULL
	};
	size_t i;

	strlcat(buf, cmd, sizeof(buf));
	for (i = 1; args && args[i]; i++) {
		strlcat(buf, " ", sizeof(buf));
		strlcat(buf, args[i], sizeof(buf));
	}
	logit(LOG_DEBUG, "Calling %s %s", _PATH_BSHELL, buf);
	dbg("Calling %s %s", _PATH_BSHELL, buf);

	return execvp(_PATH_BSHELL, argv);
}

static void prepare_tty(char *tty, speed_t speed, char *procname, struct rlimit rlimit[])
{
	char name[80];
	int fd, dummy;

	fd = open(tty, O_RDWR);
	if (fd < 0) {
		logit(LOG_ERR, "Failed opening %s: %s", tty, strerror(errno));
		_exit(1);
	}

	dup2(fd, STDIN_FILENO);
	dup2(fd, STDOUT_FILENO);
	dup2(fd, STDERR_FILENO);

	/* Set default TERM, run_getty() below allows override */
	if (ioctl(fd, VT_OPENQRY, &dummy) == -1)
		setenv("TERM", "vt102", 1); /* likely a serial line */
	else
		setenv("TERM", "linux", 1);

	/*
	 * Reset to sane defaults in case of messup from prev. session
	 */
	stty(fd, speed);
	close(fd);

	/* Set configured limits */
	for (int i = 0; i < RLIMIT_NLIMITS; i++) {
		if (setrlimit(i, &rlimit[i]) == -1)
			logit(LOG_WARNING, "%s: rlimit: Failed setting %s", tty, rlim2str(i));
	}

	/* Finit is responsible for the UTMP INIT_PROCESS record */
	utmp_set_init(tty, 0);
	if (!strncmp("/dev/", tty, 5))
		tty += 5;
	snprintf(name, sizeof(name), "%s %s", procname, tty);
	prctl(PR_SET_NAME, name, 0, 0, 0);
}

static int activate_console(int noclear, int nowait)
{
	static const char msg[] = "\nPlease press Enter to activate this console.";
	static const char clr[] = "\r\e[K";
	static const char cup[] = "\e[A";
	struct termios orig;
	char ch;
	int rc;

	if (nowait || rescue)
		return 1;

	if (!noclear)
		dprint(STDERR_FILENO, "\e[r\e[H\e[J", 9);

	/* Disable ECHO, XON/OFF while waiting for <CR> */
	if (!tcgetattr(STDIN_FILENO, &orig)) {
		struct termios c = orig;

		c.c_iflag &= ~(BRKINT|ICRNL|INPCK|ISTRIP|IXON|IXOFF);
		c.c_oflag &= ~(OPOST);
		c.c_cflag |=  (CS8);
		c.c_lflag &= ~(ECHO|ICANON|IEXTEN|ISIG);
		tcsetattr(STDIN_FILENO, TCSAFLUSH, &c);
	}

	dprint(STDERR_FILENO, clr, strlen(clr));
	dprint(STDERR_FILENO, msg, strlen(msg));
	while ((rc = read(STDIN_FILENO, &ch, 1)) > 0 && ch != '\r' && ch != '\n')
		continue;

	/* On any error (likely EINTR), we avoid starting getty */
	if (rc == -1)
		rc = 0;

	/* Clear msg and move cursor up for next message/login: */
	dprint(STDERR_FILENO, clr, strlen(clr));
	dprint(STDERR_FILENO, cup, strlen(cup));

	/* Restore TTY */
	if (tcsetattr(STDIN_FILENO, TCSAFLUSH, &orig) == -1)
		rc = 0;		/* TTY in bad shape, restart */

	return rc;
}

/*
 * Start a getty on @tty
 *
 * At the login: prompt, no signals are allowed, both Ctrl-C and Ctrl-D
 * should be disabled.  Ctrl-S and Ctrl-Q are optional, but most getty
 * allow them.
 *
 * Prior to getty is called and login: is printed, Finit may display the
 * "Please press Enter ..." if @nowait is unset.  This mode must be RAW,
 * only accepting <CR> and not echoing anything, this also means no
 * signals are allowed.  For ease of implementation Finit will call the
 * stty() function to reset the TTY and then force RAW mode until a <CR>
 * has been received.  This is handled in the same fashion for both this
 * function and run_getty2(), which is used for external getty.
 *
 * When handing over to /bin/login, Ctrl-C and Ctrl-D must be enabled
 * since /bin/login usually only disables ECHO until a password line has
 * been entered.  Upon starting the user's $SHELL the ISIG flag is reset
 */
pid_t run_getty(char *tty, char *cmd, char *args[], int noclear, int nowait, struct rlimit rlimit[])
{
	int rc = 1;

	/* Dunno speed, tell stty() to not mess with it */
	prepare_tty(tty, B0, "getty", rlimit);
	if (activate_console(noclear, nowait)) {
		logit(LOG_INFO, "Starting getty on %s", tty);
		rc = execv(cmd, args);
	}

	vhangup();

	return rc;
}

int sh(char *tty)
{
	char *args[2] = {
		NULL,
		NULL
	};
	char *arg0;
	size_t len;

	/* The getty process is usually responsible for the UTMP login record */
	utmp_set_login(tty, NULL);

	/* Start /bin/sh as a login shell, i.e. with a prefix '-' */
	len = strlen(_PATH_BSHELL) + 2;
	arg0 = malloc(len);
	if (!arg0) {
		err(1, "Failed allocating memory");
		return 1;
	}
	snprintf(arg0, len, "-%s", _PATH_BSHELL);
	args[0] = arg0;

	/* Unblock signals inherited from parent */
	sig_unblock();

	return execv(_PATH_BSHELL, args);
}

pid_t run_sh(char *tty, int noclear, int nowait, struct rlimit rlimit[])
{
	int rc = 1;

	prepare_tty(tty, B0, "finitsh", rlimit);
	if (activate_console(noclear, nowait))
		rc = sh(tty);

	return rc;
}

pid_t run_bg(char *cmd, char *args[])
{
	pid_t pid;

	if (access(cmd, X_OK))
		return 0;

	print(-1, "Calling %s in the background", cmd);
	pid = fork();
	if (!pid)
		_exit(exec_runtask(cmd, args));
	print_result(pid == -1);

	return pid;
}

/**
 * Local Variables:
 *  indent-tabs-mode: t
 *  c-file-style: "linux"
 * End:
 */