init.c

早期freebsd实现

/*-
 * Copyright (c) 1991, 1993
 *	The Regents of the University of California.  All rights reserved.
 *
 * This code is derived from software contributed to Berkeley by
 * Donn Seeley at Berkeley Software Design, Inc.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. All advertising materials mentioning features or use of this software
 *    must display the following acknowledgement:
 *	This product includes software developed by the University of
 *	California, Berkeley and its contributors.
 * 4. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */

#ifndef lint
static char copyright[] =
"@(#) Copyright (c) 1991, 1993\n\
	The Regents of the University of California.  All rights reserved.\n";
#endif /* not lint */

#ifndef lint
static char sccsid[] = "@(#)init.c	8.1 (Berkeley) 7/15/93";
#endif /* not lint */

#include <sys/param.h>
#include <sys/sysctl.h>
#include <sys/wait.h>

#include <db.h>
#include <errno.h>
#include <fcntl.h>
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <syslog.h>
#include <time.h>
#include <ttyent.h>
#include <unistd.h>

#ifdef __STDC__
#include <stdarg.h>
#else
#include <varargs.h>
#endif

#ifdef SECURE
#include <pwd.h>
#endif

#include "pathnames.h"

/*
 * Until the mythical util.h arrives...
 */
extern int login_tty __P((int));
extern int logout __P((const char *));
extern void logwtmp __P((const char *, const char *, const char *));

/*
 * Sleep times; used to prevent thrashing.
 */
#define	GETTY_SPACING		 5	/* N secs minimum getty spacing */
#define	GETTY_SLEEP		30	/* sleep N secs after spacing problem */
#define	WINDOW_WAIT		 3	/* wait N secs after starting window */
#define	STALL_TIMEOUT		30	/* wait N secs after warning */
#define	DEATH_WATCH		10	/* wait N secs for procs to die */

void handle __P((sig_t, ...));
void delset __P((sigset_t *, ...));

void stall __P((char *, ...));
void warning __P((char *, ...));
void emergency __P((char *, ...));
void disaster __P((int));
void badsys __P((int));

/*
 * We really need a recursive typedef...
 * The following at least guarantees that the return type of (*state_t)()
 * is sufficiently wide to hold a function pointer.
 */
typedef long (*state_func_t) __P((void));
typedef state_func_t (*state_t) __P((void));

state_func_t single_user __P((void));
state_func_t runcom __P((void));
state_func_t read_ttys __P((void));
state_func_t multi_user __P((void));
state_func_t clean_ttys __P((void));
state_func_t catatonia __P((void));
state_func_t death __P((void));

enum { AUTOBOOT, FASTBOOT } runcom_mode = AUTOBOOT;

void transition __P((state_t));
state_t requested_transition = runcom;

void setctty __P((char *));

typedef struct init_session {
	int	se_index;		/* index of entry in ttys file */
	pid_t	se_process;		/* controlling process */
	time_t	se_started;		/* used to avoid thrashing */
	int	se_flags;		/* status of session */
#define	SE_SHUTDOWN	0x1		/* session won't be restarted */
	char	*se_device;		/* filename of port */
	char	*se_getty;		/* what to run on that port */
	char	**se_getty_argv;	/* pre-parsed argument array */
	char	*se_window;		/* window system (started only once) */
	char	**se_window_argv;	/* pre-parsed argument array */
	struct	init_session *se_prev;
	struct	init_session *se_next;
} session_t;

void free_session __P((session_t *));
session_t *new_session __P((session_t *, int, struct ttyent *));
session_t *sessions;

char **construct_argv __P((char *));
void start_window_system __P((session_t *));
void collect_child __P((pid_t));
pid_t start_getty __P((session_t *));
void transition_handler __P((int));
void alrm_handler __P((int));
void setsecuritylevel __P((int));
int getsecuritylevel __P((void));
int setupargv __P((session_t *, struct ttyent *));
int clang;

void clear_session_logs __P((session_t *));

int start_session_db __P((void));
void add_session __P((session_t *));
void del_session __P((session_t *));
session_t *find_session __P((pid_t));
DB *session_db;

/*
 * The mother of all processes.
 */
int
main(argc, argv)
	int argc;
	char **argv;
{
	int c;
	struct sigaction sa;
	sigset_t mask;


	/* Dispose of random users. */
	if (getuid() != 0) {
		(void)fprintf(stderr, "init: %s\n", strerror(EPERM));
		exit (1);
	}

	/* System V users like to reexec init. */
	if (getpid() != 1) {
		(void)fprintf(stderr, "init: already running\n");
		exit (1);
	}

	/*
	 * Note that this does NOT open a file...
	 * Does 'init' deserve its own facility number?
	 */
	openlog("init", LOG_CONS|LOG_ODELAY, LOG_AUTH);

	/*
	 * Create an initial session.
	 */
	if (setsid() < 0)
		warning("initial setsid() failed: %m");

	/*
	 * Establish an initial user so that programs running
	 * single user do not freak out and die (like passwd).
	 */
	if (setlogin("root") < 0)
		warning("setlogin() failed: %m");

	/*
	 * This code assumes that we always get arguments through flags,
	 * never through bits set in some random machine register.
	 */
	while ((c = getopt(argc, argv, "sf")) != -1)
		switch (c) {
		case 's':
			requested_transition = single_user;
			break;
		case 'f':
			runcom_mode = FASTBOOT;
			break;
		default:
			warning("unrecognized flag '-%c'", c);
			break;
		}

	if (optind != argc)
		warning("ignoring excess arguments");

	/*
	 * We catch or block signals rather than ignore them,
	 * so that they get reset on exec.
	 */
	handle(badsys, SIGSYS, 0);
	handle(disaster, SIGABRT, SIGFPE, SIGILL, SIGSEGV,
	       SIGBUS, SIGXCPU, SIGXFSZ, 0);
	handle(transition_handler, SIGHUP, SIGTERM, SIGTSTP, 0);
	handle(alrm_handler, SIGALRM, 0);
	sigfillset(&mask);
	delset(&mask, SIGABRT, SIGFPE, SIGILL, SIGSEGV, SIGBUS, SIGSYS,
		SIGXCPU, SIGXFSZ, SIGHUP, SIGTERM, SIGTSTP, SIGALRM, 0);
	sigprocmask(SIG_SETMASK, &mask, (sigset_t *) 0);
	sigemptyset(&sa.sa_mask);
	sa.sa_flags = 0;
	sa.sa_handler = SIG_IGN;
	(void) sigaction(SIGTTIN, &sa, (struct sigaction *)0);
	(void) sigaction(SIGTTOU, &sa, (struct sigaction *)0);

	/*
	 * Paranoia.
	 */
	close(0);
	close(1);
	close(2);

	/*
	 * Start the state machine.
	 */
	transition(requested_transition);

	/*
	 * Should never reach here.
	 */
	return 1;
}

/*
 * Associate a function with a signal handler.
 */
void
#ifdef __STDC__
handle(sig_t handler, ...)
#else
handle(va_alist)
	va_dcl
#endif
{
	int sig;
	struct sigaction sa;
	int mask_everything;
	va_list ap;
#ifndef __STDC__
	sig_t handler;

	va_start(ap);
	handler = va_arg(ap, sig_t);
#else
	va_start(ap, handler);
#endif

	sa.sa_handler = handler;
	sigfillset(&mask_everything);

	while (sig = va_arg(ap, int)) {
		sa.sa_mask = mask_everything;
		/* XXX SA_RESTART? */
		sa.sa_flags = sig == SIGCHLD ? SA_NOCLDSTOP : 0;
		sigaction(sig, &sa, (struct sigaction *) 0);
	}
	va_end(ap);
}

/*
 * Delete a set of signals from a mask.
 */
void
#ifdef __STDC__
delset(sigset_t *maskp, ...)
#else
delset(va_alist)
	va_dcl
#endif
{
	int sig;
	va_list ap;
#ifndef __STDC__
	sigset_t *maskp;

	va_start(ap);
	maskp = va_arg(ap, sigset_t *);
#else
	va_start(ap, maskp);
#endif

	while (sig = va_arg(ap, int))
		sigdelset(maskp, sig);
	va_end(ap);
}

/*
 * Log a message and sleep for a while (to give someone an opportunity
 * to read it and to save log or hardcopy output if the problem is chronic).
 * NB: should send a message to the session logger to avoid blocking.
 */
void
#ifdef __STDC__
stall(char *message, ...)
#else
stall(va_alist)
	va_dcl
#endif
{
	va_list ap;
#ifndef __STDC__
	char *message;

	va_start(ap);
	message = va_arg(ap, char *);
#else
	va_start(ap, message);
#endif

	vsyslog(LOG_ALERT, message, ap);
	va_end(ap);
	sleep(STALL_TIMEOUT);
}

/*
 * Like stall(), but doesn't sleep.
 * If cpp had variadic macros, the two functions could be #defines for another.
 * NB: should send a message to the session logger to avoid blocking.
 */
void
#ifdef __STDC__
warning(char *message, ...)
#else
warning(va_alist)
	va_dcl
#endif
{
	va_list ap;
#ifndef __STDC__
	char *message;

	va_start(ap);
	message = va_arg(ap, char *);
#else
	va_start(ap, message);
#endif

	vsyslog(LOG_ALERT, message, ap);
	va_end(ap);
}

/*
 * Log an emergency message.
 * NB: should send a message to the session logger to avoid blocking.
 */
void
#ifdef __STDC__
emergency(char *message, ...)
#else
emergency(va_alist)
	va_dcl
#endif
{
	va_list ap;
#ifndef __STDC__
	char *message;

	va_start(ap);
	message = va_arg(ap, char *);
#else
	va_start(ap, message);
#endif

	vsyslog(LOG_EMERG, message, ap);
	va_end(ap);
}

/*
 * Catch a SIGSYS signal.
 *
 * These may arise if a system does not support sysctl.
 * We tolerate up to 25 of these, then throw in the towel.
 */
void
badsys(sig)
	int sig;
{
	static int badcount = 0;

	if (badcount++ < 25)
		return;
	disaster(sig);
}

/*
 * Catch an unexpected signal.
 */
void
disaster(sig)
	int sig;
{
	emergency("fatal signal: %s",
		sig < (unsigned) NSIG ? sys_siglist[sig] : "unknown signal");

	sleep(STALL_TIMEOUT);
	_exit(sig);		/* reboot */
}

/*
 * Get the security level of the kernel.
 */
int
getsecuritylevel()
{
#ifdef KERN_SECURELVL
	int name[2], curlevel;
	size_t len;
	extern int errno;

	name[0] = CTL_KERN;
	name[1] = KERN_SECURELVL;
	len = sizeof curlevel;
	if (sysctl(name, 2, &curlevel, &len, NULL, 0) == -1) {
		emergency("cannot get kernel security level: %s",
		    strerror(errno));
		return (-1);
	}
	return (curlevel);
#else
	return (-1);
#endif
}

/*
 * Set the security level of the kernel.
 */
void
setsecuritylevel(newlevel)
	int newlevel;
{
#ifdef KERN_SECURELVL
	int name[2], curlevel;
	extern int errno;

	curlevel = getsecuritylevel();
	if (newlevel == curlevel)
		return;
	name[0] = CTL_KERN;
	name[1] = KERN_SECURELVL;
	if (sysctl(name, 2, NULL, NULL, &newlevel, sizeof newlevel) == -1) {
		emergency(
		    "cannot change kernel security level from %d to %d: %s",
		    curlevel, newlevel, strerror(errno));
		return;
	}
#ifdef SECURE
	warning("kernel security level changed from %d to %d",
	    curlevel, newlevel);
#endif
#endif
}

/*
 * Change states in the finite state machine.
 * The initial state is passed as an argument.
 */
void
transition(s)
	state_t s;
{
	for (;;)
		s = (state_t) (*s)();
}

/*
 * Close out the accounting files for a login session.
 * NB: should send a message to the session logger to avoid blocking.
 */
void
clear_session_logs(sp)
	session_t *sp;
{
	char *line = sp->se_device + sizeof(_PATH_DEV) - 1;

	if (logout(line))
		logwtmp(line, "", "");
}

/*
 * Start a session and allocate a controlling terminal.
 * Only called by children of init after forking.
 */
void
setctty(name)
	char *name;
{
	int fd;

	(void) revoke(name);
	sleep (2);			/* leave DTR low */
	if ((fd = open(name, O_RDWR)) == -1) {
		stall("can't open %s: %m", name);
		_exit(1);
	}
	if (login_tty(fd) == -1) {
		stall("can't get %s for controlling terminal: %m", name);
		_exit(1);
	}
}

/*
 * Bring the system up single user.
 */
state_func_t
single_user()
{
	pid_t pid, wpid;
	int status;
	sigset_t mask;
	char *shell = _PATH_BSHELL;
	char *argv[2];
#ifdef SECURE
	struct ttyent *typ;
	struct passwd *pp;
	static const char banner[] =
		"Enter root password, or ^D to go multi-user\n";
	char *clear, *password;
#endif

	/*
	 * If the kernel is in secure mode, downgrade it to insecure mode.
	 */
	if (getsecuritylevel() > 0)
		setsecuritylevel(0);

	if ((pid = fork()) == 0) {
		/*
		 * Start the single user session.
		 */
		setctty(_PATH_CONSOLE);

#ifdef SECURE
		/*
		 * Check the root password.
		 * We don't care if the console is 'on' by default;
		 * it's the only tty that can be 'off' and 'secure'.
		 */
		typ = getttynam("console");
		pp = getpwnam("root");
		if (typ && (typ->ty_status & TTY_SECURE) == 0 && pp) {
			write(2, banner, sizeof banner - 1);
			for (;;) {
				clear = getpass("Password:");
				if (clear == 0 || *clear == '\0')
					_exit(0);
				password = crypt(clear, pp->pw_passwd);
				bzero(clear, _PASSWORD_LEN);
				if (strcmp(password, pp->pw_passwd) == 0)
					break;
				warning("single-user login failed\n");
			}
		}
		endttyent();
		endpwent();
#endif /* SECURE */

#ifdef DEBUGSHELL
		{
			char altshell[128], *cp = altshell;
			int num;

#define	SHREQUEST \
	"Enter pathname of shell or RETURN for sh: "
			(void)write(STDERR_FILENO,
			    SHREQUEST, sizeof(SHREQUEST) - 1);
			while ((num = read(STDIN_FILENO, cp, 1)) != -1 &&
			    num != 0 && *cp != '\n' && cp < &altshell[127])
					cp++;
			*cp = '\0';
			if (altshell[0] != '\0')
				shell = altshell;
		}
#endif /* DEBUGSHELL */

		/*
		 * Unblock signals.
		 * We catch all the interesting ones,
		 * and those are reset to SIG_DFL on exec.
		 */
		sigemptyset(&mask);
		sigprocmask(SIG_SETMASK, &mask, (sigset_t *) 0);

		/*
		 * Fire off a shell.
		 * If the default one doesn't work, try the Bourne shell.
		 */
		argv[0] = "-sh";
		argv[1] = 0;
		execv(shell, argv);
		emergency("can't exec %s for single user: %m", shell);
		execv(_PATH_BSHELL, argv);
		emergency("can't exec %s for single user: %m", _PATH_BSHELL);
		sleep(STALL_TIMEOUT);
		_exit(1);
	}

	if (pid == -1) {
		/*
		 * We are seriously hosed.  Do our best.
		 */
		emergency("can't fork single-user shell, trying again");
		while (waitpid(-1, (int *) 0, WNOHANG) > 0)
			continue;
		return (state_func_t) single_user;
	}

	requested_transition = 0;
	do {
		if ((wpid = waitpid(-1, &status, WUNTRACED)) != -1)
			collect_child(wpid);
		if (wpid == -1) {