[thirdparty/util-linux.git] / lib / pty-session.c

/*
 * This is pseudo-terminal container for child process where parent creates a
 * proxy between the current std{in,out,etrr} and the child's pty. Advantages:
 *
 * - child has no access to parent's terminal (e.g. su --pty)
 * - parent can log all traffic between user and child's terminall (e.g. script(1))
 * - it's possible to start commands on terminal although parent has no terminal
 *
 * This code is in the public domain; do with it what you wish.
 *
 * Written by Karel Zak <kzak@redhat.com> in Jul 2019
 */
#include <stdio.h>
#include <stdlib.h>
#include <pty.h>
#include <poll.h>
#include <sys/signalfd.h>
#include <paths.h>
#include <sys/types.h>
#include <sys/wait.h>

#include "c.h"
#include "all-io.h"
#include "ttyutils.h"
#include "pty-session.h"
#include "monotonic.h"
#include "debug.h"

static UL_DEBUG_DEFINE_MASK(ulpty);
UL_DEBUG_DEFINE_MASKNAMES(ulpty) = UL_DEBUG_EMPTY_MASKNAMES;

#define ULPTY_DEBUG_INIT	(1 << 1)
#define ULPTY_DEBUG_SETUP	(1 << 2)
#define ULPTY_DEBUG_SIG		(1 << 3)
#define ULPTY_DEBUG_IO		(1 << 4)
#define ULPTY_DEBUG_DONE	(1 << 5)
#define ULPTY_DEBUG_ALL		0xFFFF

#define DBG(m, x)       __UL_DBG(ulpty, ULPTY_DEBUG_, m, x)
#define ON_DBG(m, x)    __UL_DBG_CALL(ulpty, ULPTY_DEBUG_, m, x)

#define UL_DEBUG_CURRENT_MASK   UL_DEBUG_MASK(ulpty)
#include "debugobj.h"

void ul_pty_init_debug(int mask)
{
	if (ulpty_debug_mask)
		return;
	__UL_INIT_DEBUG_FROM_ENV(ulpty, ULPTY_DEBUG_, mask, ULPTY_DEBUG);
}

struct ul_pty *ul_new_pty(int is_stdin_tty)
{
	struct ul_pty *pty = calloc(1, sizeof(*pty));

	if (!pty)
		return NULL;

	DBG(SETUP, ul_debugobj(pty, "alloc handler"));
	pty->isterm = is_stdin_tty;
	pty->master = -1;
	pty->slave = -1;
	pty->sigfd = -1;
	pty->child = (pid_t) -1;

	return pty;
}

void ul_free_pty(struct ul_pty *pty)
{
	free(pty);
}


int ul_pty_get_delivered_signal(struct ul_pty *pty)
{
	assert(pty);
	return pty->delivered_signal;
}

struct ul_pty_callbacks *ul_pty_get_callbacks(struct ul_pty *pty)
{
	assert(pty);
	return &pty->callbacks;
}

void ul_pty_set_callback_data(struct ul_pty *pty, void *data)
{
	assert(pty);
	pty->callback_data = data;
}

void ul_pty_set_child(struct ul_pty *pty, pid_t child)
{
	assert(pty);
	pty->child = child;
}

int ul_pty_get_childfd(struct ul_pty *pty)
{
	assert(pty);
	return pty->master;
}

pid_t ul_pty_get_child(struct ul_pty *pty)
{
	assert(pty);
	return pty->child;
}

/* it's active when signals are redurected to sigfd */
int ul_pty_is_running(struct ul_pty *pty)
{
	assert(pty);
	return pty->sigfd >= 0;
}

void ul_pty_set_mainloop_time(struct ul_pty *pty, struct timeval *tv)
{
	assert(pty);
	if (!tv) {
		DBG(IO, ul_debugobj(pty, "mainloop time: clear"));
		timerclear(&pty->next_callback_time);
	} else {
		pty->next_callback_time.tv_sec = tv->tv_sec;
		pty->next_callback_time.tv_usec = tv->tv_usec;
		DBG(IO, ul_debugobj(pty, "mainloop time: %ld.%06ld", tv->tv_sec, tv->tv_usec));
	}
}

/* call me before fork() */
int ul_pty_setup(struct ul_pty *pty)
{
	struct termios slave_attrs;
	int rc;

	/* save the current signals setting */
	sigprocmask(0, NULL, &pty->orgsig);

	if (pty->isterm) {
	        DBG(SETUP, ul_debugobj(pty, "create for terminal"));

		/* original setting of the current terminal */
		if (tcgetattr(STDIN_FILENO, &pty->stdin_attrs) != 0)
			return -errno;
		ioctl(STDIN_FILENO, TIOCGWINSZ, (char *)&pty->win);
		/* create master+slave */
		rc = openpty(&pty->master, &pty->slave, NULL, &pty->stdin_attrs, &pty->win);

		/* set the current terminal to raw mode; pty_cleanup() reverses this change on exit */
		slave_attrs = pty->stdin_attrs;
		cfmakeraw(&slave_attrs);
		slave_attrs.c_lflag &= ~ECHO;
		tcsetattr(STDIN_FILENO, TCSANOW, &slave_attrs);
	} else {
	        DBG(SETUP, ul_debugobj(pty, "create for non-terminal"));
		rc = openpty(&pty->master, &pty->slave, NULL, NULL, NULL);

		if (!rc) {
			tcgetattr(pty->slave, &slave_attrs);
			slave_attrs.c_lflag &= ~ECHO;
			tcsetattr(pty->slave, TCSANOW, &slave_attrs);
		}
	}

	DBG(SETUP, ul_debugobj(pty, "pty setup done [master=%d, slave=%d, rc=%d]",
				pty->master, pty->slave, rc));
	return rc;
}

/* cleanup in parent process */
void ul_pty_cleanup(struct ul_pty *pty)
{
	struct termios rtt;

	if (pty->master == -1 || !pty->isterm)
		return;

	DBG(DONE, ul_debugobj(pty, "cleanup"));
	rtt = pty->stdin_attrs;
	tcsetattr(STDIN_FILENO, TCSADRAIN, &rtt);
}

/* call me in child process */
void ul_pty_init_slave(struct ul_pty *pty)
{
	DBG(SETUP, ul_debugobj(pty, "initialize slave"));

	setsid();

	ioctl(pty->slave, TIOCSCTTY, 1);
	close(pty->master);

	dup2(pty->slave, STDIN_FILENO);
	dup2(pty->slave, STDOUT_FILENO);
	dup2(pty->slave, STDERR_FILENO);

	close(pty->slave);

	if (pty->sigfd >= 0)
		close(pty->sigfd);

	pty->slave = -1;
	pty->master = -1;
	pty->sigfd = -1;

	sigprocmask(SIG_SETMASK, &pty->orgsig, NULL);

	DBG(SETUP, ul_debugobj(pty, "... initialize slave done"));
}

static int write_output(char *obuf, ssize_t bytes)
{
	DBG(IO, ul_debug(" writing output"));

	if (write_all(STDOUT_FILENO, obuf, bytes)) {
		DBG(IO, ul_debug("  writing output *failed*"));
		return -errno;
	}

	return 0;
}

static int write_to_child(struct ul_pty *pty, char *buf, size_t bufsz)
{
	return write_all(pty->master, buf, bufsz);
}

/*
 * The pty is usually faster than shell, so it's a good idea to wait until
 * the previous message has been already read by shell from slave before we
 * write to master. This is necessary especially for EOF situation when we can
 * send EOF to master before shell is fully initialized, to workaround this
 * problem we wait until slave is empty. For example:
 *
 *   echo "date" | su --pty
 *
 * Unfortunately, the child (usually shell) can ignore stdin at all, so we
 * don't wait forever to avoid dead locks...
 *
 * Note that su --pty is primarily designed for interactive sessions as it
 * maintains master+slave tty stuff within the session. Use pipe to write to
 * pty and assume non-interactive (tee-like) behavior is NOT well supported.
 */
static void write_eof_to_child(struct ul_pty *pty)
{
	unsigned int tries = 0;
	struct pollfd fds[] = {
	           { .fd = pty->slave, .events = POLLIN }
	};
	char c = DEF_EOF;

	DBG(IO, ul_debugobj(pty, " waiting for empty slave"));
	while (poll(fds, 1, 10) == 1 && tries < 8) {
		DBG(IO, ul_debugobj(pty, "   slave is not empty"));
		xusleep(250000);
		tries++;
	}
	if (tries < 8)
		DBG(IO, ul_debugobj(pty, "   slave is empty now"));

	DBG(IO, ul_debugobj(pty, " sending EOF to master"));
	write_to_child(pty, &c, sizeof(char));
}

static int mainloop_callback(struct ul_pty *pty)
{
	if (!pty->callbacks.mainloop)
		return 0;

	DBG(IO, ul_debugobj(pty, "calling mainloop callback"));
	return pty->callbacks.mainloop(pty->callback_data);
}

static int handle_io(struct ul_pty *pty, int fd, int *eof)
{
	char buf[BUFSIZ];
	ssize_t bytes;
	int rc = 0;

	DBG(IO, ul_debugobj(pty, " handle I/O on fd=%d", fd));
	*eof = 0;

	/* read from active FD */
	bytes = read(fd, buf, sizeof(buf));
	if (bytes < 0) {
		if (errno == EAGAIN || errno == EINTR)
			return 0;
		return -errno;
	}

	if (bytes == 0) {
		*eof = 1;
		return 0;
	}

	/* from stdin (user) to command */
	if (fd == STDIN_FILENO) {
		DBG(IO, ul_debugobj(pty, " stdin --> master %zd bytes", bytes));

		if (write_to_child(pty, buf, bytes))
			return -errno;

		/* without sync write_output() will write both input &
		 * shell output that looks like double echoing */
		fdatasync(pty->master);

	/* from command (master) to stdout */
	} else if (fd == pty->master) {
		DBG(IO, ul_debugobj(pty, " master --> stdout %zd bytes", bytes));
		write_output(buf, bytes);
	}

	if (pty->callbacks.log_stream_activity)
		rc = pty->callbacks.log_stream_activity(
					pty->callback_data, fd, buf, bytes);

	return rc;
}

void ul_pty_wait_for_child(struct ul_pty *pty)
{
	int status;
	pid_t pid;
	int options = 0;

	if (pty->child == (pid_t) -1)
		return;

	DBG(SIG, ul_debug("waiting for child [child=%d]", (int) pty->child));

	if (ul_pty_is_running(pty)) {
		/* wait for specific child */
		options = WNOHANG;
		for (;;) {
			pid = waitpid(pty->child, &status, options);
			DBG(SIG, ul_debug(" waitpid done [rc=%d]", (int) pid));
			if (pid != (pid_t) - 1) {
				if (pty->callbacks.child_die)
					pty->callbacks.child_die(
							pty->callback_data,
							pty->child, status);
				ul_pty_set_child(pty, (pid_t) -1);
			} else
				break;
		}
	} else {
		/* final wait */
		while ((pid = wait3(&status, options, NULL)) > 0) {
			DBG(SIG, ul_debug(" wait3 done [rc=%d]", (int) pid));
			if (pid == pty->child) {
				if (pty->callbacks.child_die)
					pty->callbacks.child_die(
							pty->callback_data,
							pty->child, status);
				ul_pty_set_child(pty, (pid_t) -1);
			}
		}
	}
}

static int handle_signal(struct ul_pty *pty, int fd)
{
	struct signalfd_siginfo info;
	ssize_t bytes;
	int rc = 0;

	DBG(SIG, ul_debugobj(pty, " handle signal on fd=%d", fd));

	bytes = read(fd, &info, sizeof(info));
	if (bytes != sizeof(info)) {
		if (bytes < 0 && (errno == EAGAIN || errno == EINTR))
			return 0;
		return -errno;
	}

	switch (info.ssi_signo) {
	case SIGCHLD:
		DBG(SIG, ul_debugobj(pty, " get signal SIGCHLD"));

		if (info.ssi_code == CLD_EXITED
		    || info.ssi_code == CLD_KILLED
		    || info.ssi_code == CLD_DUMPED) {

			if (pty->callbacks.child_wait)
				pty->callbacks.child_wait(pty->callback_data,
							  pty->child);
			else
				ul_pty_wait_for_child(pty);

		} else if (info.ssi_status == SIGSTOP && pty->child > 0)
			pty->callbacks.child_sigstop(pty->callback_data,
						     pty->child);

		if (pty->child <= 0) {
			DBG(SIG, ul_debugobj(pty, " no child, setting leaving timeout"));
			pty->poll_timeout = 10;
			timerclear(&pty->next_callback_time);
		}
		return 0;
	case SIGWINCH:
		DBG(SIG, ul_debugobj(pty, " get signal SIGWINCH"));
		if (pty->isterm) {
			ioctl(STDIN_FILENO, TIOCGWINSZ, (char *)&pty->win);
			ioctl(pty->slave, TIOCSWINSZ, (char *)&pty->win);

			if (pty->callbacks.log_signal)
				rc = pty->callbacks.log_signal(pty->callback_data,
							&info, (void *) &pty->win);
		}
		break;
	case SIGTERM:
		/* fallthrough */
	case SIGINT:
		/* fallthrough */
	case SIGQUIT:
		DBG(SIG, ul_debugobj(pty, " get signal SIG{TERM,INT,QUIT}"));
		pty->delivered_signal = info.ssi_signo;
                /* Child termination is going to generate SIGCHILD (see above) */
		if (pty->child > 0)
	                kill(pty->child, SIGTERM);

		if (pty->callbacks.log_signal)
			rc = pty->callbacks.log_signal(pty->callback_data,
					&info, (void *) &pty->win);
		break;
	default:
		abort();
	}

	return rc;
}

/* loop in parent */
int ul_pty_proxy_master(struct ul_pty *pty)
{
	sigset_t ourset;
	int rc = 0, ret, eof = 0;
	enum {
		POLLFD_SIGNAL = 0,
		POLLFD_MASTER,
		POLLFD_STDIN

	};
	struct pollfd pfd[] = {
		[POLLFD_SIGNAL] = { .fd = -1,		.events = POLLIN | POLLERR | POLLHUP },
		[POLLFD_MASTER] = { .fd = pty->master,  .events = POLLIN | POLLERR | POLLHUP },
		[POLLFD_STDIN]	= { .fd = STDIN_FILENO, .events = POLLIN | POLLERR | POLLHUP }
	};

	/* We use signalfd and standard signals by handlers are blocked
	 * at all
	 */
	sigfillset(&ourset);
	if (sigprocmask(SIG_BLOCK, &ourset, NULL))
		return -errno;

	sigemptyset(&ourset);
	sigaddset(&ourset, SIGCHLD);
	sigaddset(&ourset, SIGWINCH);
	sigaddset(&ourset, SIGALRM);
	sigaddset(&ourset, SIGTERM);
	sigaddset(&ourset, SIGINT);
	sigaddset(&ourset, SIGQUIT);

	if ((pty->sigfd = signalfd(-1, &ourset, SFD_CLOEXEC)) < 0) {
		rc = -errno;
		goto done;
	}

	pfd[POLLFD_SIGNAL].fd = pty->sigfd;
	pty->poll_timeout = -1;

	while (!pty->delivered_signal) {
		size_t i;
		int errsv, timeout;

		DBG(IO, ul_debugobj(pty, "--poll() loop--"));

		/* note, callback usually updates @next_callback_time */
		if (timerisset(&pty->next_callback_time)) {
			struct timeval now;

			DBG(IO, ul_debugobj(pty, " callback requested"));
			gettime_monotonic(&now);
			if (timercmp(&now, &pty->next_callback_time, >)) {
				rc = mainloop_callback(pty);
				if (rc)
					break;
			}
		}

		/* set timeout */
		if (timerisset(&pty->next_callback_time)) {
			struct timeval now, rest;

			gettime_monotonic(&now);
			timersub(&pty->next_callback_time, &now, &rest);
			timeout = (rest.tv_sec * 1000) +  (rest.tv_usec / 1000);
		} else
			timeout = pty->poll_timeout;

		/* wait for input, signal or timeout */
		DBG(IO, ul_debugobj(pty, "calling poll() [timeout=%dms]", timeout));
		ret = poll(pfd, ARRAY_SIZE(pfd), timeout);

		errsv = errno;
		DBG(IO, ul_debugobj(pty, "poll() rc=%d", ret));

		/* error */
		if (ret < 0) {
			if (errsv == EAGAIN)
				continue;
			rc = -errno;
			break;
		}

		/* timeout */
		if (ret == 0) {
			if (timerisset(&pty->next_callback_time)) {
				rc = mainloop_callback(pty);
				if (rc == 0)
					continue;
			} else
				rc = 0;

			DBG(IO, ul_debugobj(pty, "leaving poll() loop [timeout=%d, rc=%d]", timeout, rc));
			break;
		}
		/* event */
		for (i = 0; i < ARRAY_SIZE(pfd); i++) {
			rc = 0;

			if (pfd[i].revents == 0)
				continue;

			DBG(IO, ul_debugobj(pty, " active pfd[%s].fd=%d %s %s %s",
						i == POLLFD_STDIN  ? "stdin" :
						i == POLLFD_MASTER ? "master" :
						i == POLLFD_SIGNAL ? "signal" : "???",
						pfd[i].fd,
						pfd[i].revents & POLLIN  ? "POLLIN" : "",
						pfd[i].revents & POLLHUP ? "POLLHUP" : "",
						pfd[i].revents & POLLERR ? "POLLERR" : ""));
			switch (i) {
			case POLLFD_STDIN:
			case POLLFD_MASTER:
				/* data */
				if (pfd[i].revents & POLLIN)
					rc = handle_io(pty, pfd[i].fd, &eof);
				/* EOF maybe detected by two ways:
				 *	A) poll() return POLLHUP event after close()
				 *	B) read() returns 0 (no data) */
				if ((pfd[i].revents & POLLHUP) || eof) {
					DBG(IO, ul_debugobj(pty, " ignore FD"));
					pfd[i].fd = -1;
					if (i == POLLFD_STDIN) {
						write_eof_to_child(pty);
						DBG(IO, ul_debugobj(pty, "  ignore STDIN"));
					}
				}
				continue;
			case POLLFD_SIGNAL:
				rc = handle_signal(pty, pfd[i].fd);
				break;
			}
			if (rc)
				break;
		}
	}

done:
	if (pty->sigfd != -1)
		close(pty->sigfd);
	pty->sigfd = -1;

	/* restore original setting */
	sigprocmask(SIG_SETMASK, &pty->orgsig, NULL);

	DBG(IO, ul_debug("poll() done [signal=%d, rc=%d]", pty->delivered_signal, rc));
	return rc;
}

#ifdef TEST_PROGRAM_PTY
/*
 * $ make test_pty
 * $ ./test_pty
 *
 * ... and see for example tty(1) or "ps afu"
 */
static void child_sigstop(void *data __attribute__((__unused__)), pid_t child)
{
	kill(getpid(), SIGSTOP);
	kill(child, SIGCONT);
}

int main(int argc, char *argv[])
{
	struct ul_pty_callbacks *cb;
	const char *shell, *command = NULL, *shname = NULL;
	int caught_signal = 0;
	pid_t child;
	struct ul_pty *pty;

	shell = getenv("SHELL");
	if (shell == NULL)
		shell = _PATH_BSHELL;
	if (argc == 2)
		command = argv[1];

	ul_pty_init_debug(0);

	pty = ul_new_pty(isatty(STDIN_FILENO));
	if (!pty)
		err(EXIT_FAILURE, "failed to allocate PTY handler");

	cb = ul_pty_get_callbacks(pty);
	cb->child_sigstop = child_sigstop;

	if (ul_pty_setup(pty))
		err(EXIT_FAILURE, "failed to create pseudo-terminal");

	fflush(stdout);			/* ??? */

	switch ((int) (child = fork())) {
	case -1: /* error */
		ul_pty_cleanup(pty);
		err(EXIT_FAILURE, "cannot create child process");
		break;

	case 0: /* child */
		ul_pty_init_slave(pty);

		signal(SIGTERM, SIG_DFL); /* because /etc/csh.login */

		shname = strrchr(shell, '/');
		shname = shname ? shname + 1 : shell;

		if (command)
			execl(shell, shname, "-c", command, NULL);
		else
			execl(shell, shname, "-i", NULL);
		err(EXIT_FAILURE, "failed to execute %s", shell);
		break;

	default:
		break;
	}

	/* parent */
	ul_pty_set_child(pty, child);

	/* this is the main loop */
	ul_pty_proxy_master(pty);

	/* all done; cleanup and kill */
	caught_signal = ul_pty_get_delivered_signal(pty);

	if (!caught_signal && ul_pty_get_child(pty) != (pid_t)-1)
		ul_pty_wait_for_child(pty);	/* final wait */

	if (caught_signal && ul_pty_get_child(pty) != (pid_t)-1) {
		fprintf(stderr, "\nSession terminated, killing shell...");
		kill(child, SIGTERM);
		sleep(2);
		kill(child, SIGKILL);
		fprintf(stderr, " ...killed.\n");
	}

	ul_pty_cleanup(pty);
	ul_free_pty(pty);
	return EXIT_SUCCESS;
}

#endif /* TEST_PROGRAM */
Commit	Line	Data
6954895c KZ	1	/*
	2	* This is pseudo-terminal container for child process where parent creates a
	3	* proxy between the current std{in,out,etrr} and the child's pty. Advantages:
	4	*
	5	* - child has no access to parent's terminal (e.g. su --pty)
	6	* - parent can log all traffic between user and child's terminall (e.g. script(1))
	7	* - it's possible to start commands on terminal although parent has no terminal
	8	*
	9	* This code is in the public domain; do with it what you wish.
	10	*
	11	* Written by Karel Zak <kzak@redhat.com> in Jul 2019
	12	*/
	13	#include <stdio.h>
	14	#include <stdlib.h>
	15	#include <pty.h>
	16	#include <poll.h>
	17	#include <sys/signalfd.h>
	18	#include <paths.h>
	19	#include <sys/types.h>
	20	#include <sys/wait.h>
	21
	22	#include "c.h"
	23	#include "all-io.h"
	24	#include "ttyutils.h"
	25	#include "pty-session.h"
4d5b2fed	26	#include "monotonic.h"
6954895c KZ	27	#include "debug.h"
	28
	29	static UL_DEBUG_DEFINE_MASK(ulpty);
	30	UL_DEBUG_DEFINE_MASKNAMES(ulpty) = UL_DEBUG_EMPTY_MASKNAMES;
	31
	32	#define ULPTY_DEBUG_INIT (1 << 1)
	33	#define ULPTY_DEBUG_SETUP (1 << 2)
	34	#define ULPTY_DEBUG_SIG (1 << 3)
	35	#define ULPTY_DEBUG_IO (1 << 4)
	36	#define ULPTY_DEBUG_DONE (1 << 5)
	37	#define ULPTY_DEBUG_ALL 0xFFFF
	38
	39	#define DBG(m, x) __UL_DBG(ulpty, ULPTY_DEBUG_, m, x)
	40	#define ON_DBG(m, x) __UL_DBG_CALL(ulpty, ULPTY_DEBUG_, m, x)
	41
	42	#define UL_DEBUG_CURRENT_MASK UL_DEBUG_MASK(ulpty)
	43	#include "debugobj.h"
	44
	45	void ul_pty_init_debug(int mask)
	46	{
	47	if (ulpty_debug_mask)
	48	return;
	49	__UL_INIT_DEBUG_FROM_ENV(ulpty, ULPTY_DEBUG_, mask, ULPTY_DEBUG);
	50	}
	51
	52	struct ul_pty *ul_new_pty(int is_stdin_tty)
	53	{
	54	struct ul_pty pty = calloc(1, sizeof(pty));
	55
	56	if (!pty)
	57	return NULL;
	58
	59	DBG(SETUP, ul_debugobj(pty, "alloc handler"));
	60	pty->isterm = is_stdin_tty;
	61	pty->master = -1;
	62	pty->slave = -1;
	63	pty->sigfd = -1;
	64	pty->child = (pid_t) -1;
	65
	66	return pty;
	67	}
	68
ab61a038	69	void ul_free_pty(struct ul_pty *pty)
6954895c	70	{
ab61a038	71	free(pty);
6954895c KZ	72	}
6954895c KZ	73
ab61a038	74
6954895c KZ	75	int ul_pty_get_delivered_signal(struct ul_pty *pty)
	76	{
	77	assert(pty);
	78	return pty->delivered_signal;
	79	}
	80
	81	struct ul_pty_callbacks ul_pty_get_callbacks(struct ul_pty pty)
	82	{
	83	assert(pty);
	84	return &pty->callbacks;
	85	}
	86
	87	void ul_pty_set_callback_data(struct ul_pty pty, void data)
	88	{
	89	assert(pty);
	90	pty->callback_data = data;
	91	}
	92
	93	void ul_pty_set_child(struct ul_pty *pty, pid_t child)
	94	{
	95	assert(pty);
	96	pty->child = child;
	97	}
	98
4d5b2fed KZ	99	int ul_pty_get_childfd(struct ul_pty *pty)
	100	{
	101	assert(pty);
	102	return pty->master;
	103	}
	104
bdd43357 KZ	105	pid_t ul_pty_get_child(struct ul_pty *pty)
	106	{
	107	assert(pty);
	108	return pty->child;
	109	}
	110
6954895c KZ	111	/* it's active when signals are redurected to sigfd */
	112	int ul_pty_is_running(struct ul_pty *pty)
	113	{
	114	assert(pty);
	115	return pty->sigfd >= 0;
	116	}
	117
4d5b2fed KZ	118	void ul_pty_set_mainloop_time(struct ul_pty pty, struct timeval tv)
	119	{
	120	assert(pty);
	121	if (!tv) {
	122	DBG(IO, ul_debugobj(pty, "mainloop time: clear"));
	123	timerclear(&pty->next_callback_time);
	124	} else {
	125	pty->next_callback_time.tv_sec = tv->tv_sec;
	126	pty->next_callback_time.tv_usec = tv->tv_usec;
	127	DBG(IO, ul_debugobj(pty, "mainloop time: %ld.%06ld", tv->tv_sec, tv->tv_usec));
	128	}
	129	}
	130
6954895c KZ	131	/* call me before fork() */
	132	int ul_pty_setup(struct ul_pty *pty)
	133	{
	134	struct termios slave_attrs;
	135	int rc;
	136
ab61a038 KZ	137	/* save the current signals setting */
	138	sigprocmask(0, NULL, &pty->orgsig);
	139
6954895c KZ	140	if (pty->isterm) {
	141	DBG(SETUP, ul_debugobj(pty, "create for terminal"));
	142
	143	/* original setting of the current terminal */
	144	if (tcgetattr(STDIN_FILENO, &pty->stdin_attrs) != 0)
	145	return -errno;
	146	ioctl(STDIN_FILENO, TIOCGWINSZ, (char *)&pty->win);
	147	/* create master+slave */
	148	rc = openpty(&pty->master, &pty->slave, NULL, &pty->stdin_attrs, &pty->win);
	149
	150	/* set the current terminal to raw mode; pty_cleanup() reverses this change on exit */
	151	slave_attrs = pty->stdin_attrs;
	152	cfmakeraw(&slave_attrs);
	153	slave_attrs.c_lflag &= ~ECHO;
	154	tcsetattr(STDIN_FILENO, TCSANOW, &slave_attrs);
	155	} else {
	156	DBG(SETUP, ul_debugobj(pty, "create for non-terminal"));
	157	rc = openpty(&pty->master, &pty->slave, NULL, NULL, NULL);
	158
	159	if (!rc) {
	160	tcgetattr(pty->slave, &slave_attrs);
	161	slave_attrs.c_lflag &= ~ECHO;
	162	tcsetattr(pty->slave, TCSANOW, &slave_attrs);
	163	}
	164	}
	165
	166	DBG(SETUP, ul_debugobj(pty, "pty setup done [master=%d, slave=%d, rc=%d]",
	167	pty->master, pty->slave, rc));
	168	return rc;
	169	}
	170
	171	/* cleanup in parent process */
	172	void ul_pty_cleanup(struct ul_pty *pty)
	173	{
	174	struct termios rtt;
	175
	176	if (pty->master == -1 \|\| !pty->isterm)
	177	return;
	178
	179	DBG(DONE, ul_debugobj(pty, "cleanup"));
	180	rtt = pty->stdin_attrs;
	181	tcsetattr(STDIN_FILENO, TCSADRAIN, &rtt);
	182	}
	183
	184	/* call me in child process */
	185	void ul_pty_init_slave(struct ul_pty *pty)
	186	{
	187	DBG(SETUP, ul_debugobj(pty, "initialize slave"));
	188
	189	setsid();
	190
	191	ioctl(pty->slave, TIOCSCTTY, 1);
	192	close(pty->master);
	193
	194	dup2(pty->slave, STDIN_FILENO);
	195	dup2(pty->slave, STDOUT_FILENO);
	196	dup2(pty->slave, STDERR_FILENO);
	197
	198	close(pty->slave);
	199
	200	if (pty->sigfd >= 0)
	201	close(pty->sigfd);
	202
	203	pty->slave = -1;
204	pty->master = -1;
205	pty->sigfd = -1;
206
207	sigprocmask(SIG_SETMASK, &pty->orgsig, NULL);
208
209	DBG(SETUP, ul_debugobj(pty, "... initialize slave done"));
210	}
211
212	static int write_output(char *obuf, ssize_t bytes)
213	{
214	DBG(IO, ul_debug(" writing output"));
215
216	if (write_all(STDOUT_FILENO, obuf, bytes)) {
217	DBG(IO, ul_debug(" writing output failed"));
218	return -errno;
219	}
220
221	return 0;
222	}
223
4d5b2fed	224	static int write_to_child(struct ul_pty pty, char buf, size_t bufsz)
6954895c KZ	225	{
	226	return write_all(pty->master, buf, bufsz);
	227	}
	228
	229	/*
	230	* The pty is usually faster than shell, so it's a good idea to wait until
	231	* the previous message has been already read by shell from slave before we
	232	* write to master. This is necessary especially for EOF situation when we can
	233	* send EOF to master before shell is fully initialized, to workaround this
	234	* problem we wait until slave is empty. For example:
	235	*
	236	* echo "date" \| su --pty
	237	*
	238	* Unfortunately, the child (usually shell) can ignore stdin at all, so we
	239	* don't wait forever to avoid dead locks...
	240	*
	241	* Note that su --pty is primarily designed for interactive sessions as it
	242	* maintains master+slave tty stuff within the session. Use pipe to write to
	243	* pty and assume non-interactive (tee-like) behavior is NOT well supported.
	244	*/
	245	static void write_eof_to_child(struct ul_pty *pty)
	246	{
	247	unsigned int tries = 0;
	248	struct pollfd fds[] = {
	249	{ .fd = pty->slave, .events = POLLIN }
	250	};
	251	char c = DEF_EOF;
	252
	253	DBG(IO, ul_debugobj(pty, " waiting for empty slave"));
	254	while (poll(fds, 1, 10) == 1 && tries < 8) {
	255	DBG(IO, ul_debugobj(pty, " slave is not empty"));
	256	xusleep(250000);
	257	tries++;
	258	}
	259	if (tries < 8)
	260	DBG(IO, ul_debugobj(pty, " slave is empty now"));
	261
	262	DBG(IO, ul_debugobj(pty, " sending EOF to master"));
	263	write_to_child(pty, &c, sizeof(char));
	264	}
	265
4d5b2fed KZ	266	static int mainloop_callback(struct ul_pty *pty)
	267	{
	268	if (!pty->callbacks.mainloop)
	269	return 0;
	270
	271	DBG(IO, ul_debugobj(pty, "calling mainloop callback"));
	272	return pty->callbacks.mainloop(pty->callback_data);
	273	}
	274
6954895c KZ	275	static int handle_io(struct ul_pty pty, int fd, int eof)
	276	{
	277	char buf[BUFSIZ];
	278	ssize_t bytes;
4f7f723b	279	int rc = 0;
6954895c	280
c4bacbd1	281	DBG(IO, ul_debugobj(pty, " handle I/O on fd=%d", fd));
6954895c KZ	282	*eof = 0;
	283
	284	/* read from active FD */
	285	bytes = read(fd, buf, sizeof(buf));
	286	if (bytes < 0) {
	287	if (errno == EAGAIN \|\| errno == EINTR)
	288	return 0;
	289	return -errno;
	290	}
	291
	292	if (bytes == 0) {
	293	*eof = 1;
	294	return 0;
	295	}
	296
	297	/* from stdin (user) to command */
	298	if (fd == STDIN_FILENO) {
	299	DBG(IO, ul_debugobj(pty, " stdin --> master %zd bytes", bytes));
	300
	301	if (write_to_child(pty, buf, bytes))
	302	return -errno;
	303
	304	/* without sync write_output() will write both input &
	305	* shell output that looks like double echoing */
	306	fdatasync(pty->master);
	307
	308	/* from command (master) to stdout */
	309	} else if (fd == pty->master) {
	310	DBG(IO, ul_debugobj(pty, " master --> stdout %zd bytes", bytes));
	311	write_output(buf, bytes);
	312	}
	313
4f7f723b KZ	314	if (pty->callbacks.log_stream_activity)
	315	rc = pty->callbacks.log_stream_activity(
	316	pty->callback_data, fd, buf, bytes);
	317
	318	return rc;
6954895c KZ	319	}
6954895c KZ	320
bdd43357 KZ	321	void ul_pty_wait_for_child(struct ul_pty *pty)
	322	{
	323	int status;
	324	pid_t pid;
	325	int options = 0;
	326
	327	if (pty->child == (pid_t) -1)
	328	return;
	329
125314c0	330	DBG(SIG, ul_debug("waiting for child [child=%d]", (int) pty->child));
bdd43357 KZ	331
	332	if (ul_pty_is_running(pty)) {
	333	/* wait for specific child */
	334	options = WNOHANG;
	335	for (;;) {
	336	pid = waitpid(pty->child, &status, options);
125314c0	337	DBG(SIG, ul_debug(" waitpid done [rc=%d]", (int) pid));
bdd43357 KZ	338	if (pid != (pid_t) - 1) {
	339	if (pty->callbacks.child_die)
	340	pty->callbacks.child_die(
	341	pty->callback_data,
	342	pty->child, status);
	343	ul_pty_set_child(pty, (pid_t) -1);
	344	} else
	345	break;
	346	}
	347	} else {
	348	/* final wait */
	349	while ((pid = wait3(&status, options, NULL)) > 0) {
125314c0	350	DBG(SIG, ul_debug(" wait3 done [rc=%d]", (int) pid));
bdd43357 KZ	351	if (pid == pty->child) {
	352	if (pty->callbacks.child_die)
	353	pty->callbacks.child_die(
	354	pty->callback_data,
	355	pty->child, status);
	356	ul_pty_set_child(pty, (pid_t) -1);
	357	}
	358	}
	359	}
	360	}
	361
6954895c KZ	362	static int handle_signal(struct ul_pty *pty, int fd)
	363	{
	364	struct signalfd_siginfo info;
	365	ssize_t bytes;
4f7f723b	366	int rc = 0;
6954895c	367
c4bacbd1	368	DBG(SIG, ul_debugobj(pty, " handle signal on fd=%d", fd));
6954895c KZ	369
	370	bytes = read(fd, &info, sizeof(info));
	371	if (bytes != sizeof(info)) {
	372	if (bytes < 0 && (errno == EAGAIN \|\| errno == EINTR))
	373	return 0;
	374	return -errno;
	375	}
	376
	377	switch (info.ssi_signo) {
	378	case SIGCHLD:
	379	DBG(SIG, ul_debugobj(pty, " get signal SIGCHLD"));
	380
	381	if (info.ssi_code == CLD_EXITED
	382	\|\| info.ssi_code == CLD_KILLED
bdd43357 KZ	383	\|\| info.ssi_code == CLD_DUMPED) {
	384
	385	if (pty->callbacks.child_wait)
	386	pty->callbacks.child_wait(pty->callback_data,
	387	pty->child);
	388	else
	389	ul_pty_wait_for_child(pty);
6954895c	390
bdd43357 KZ	391	} else if (info.ssi_status == SIGSTOP && pty->child > 0)
	392	pty->callbacks.child_sigstop(pty->callback_data,
	393	pty->child);
6954895c	394
984082fa	395	if (pty->child <= 0) {
125314c0	396	DBG(SIG, ul_debugobj(pty, " no child, setting leaving timeout"));
6954895c	397	pty->poll_timeout = 10;
984082fa KZ	398	timerclear(&pty->next_callback_time);
984082fa KZ	399	}
6954895c KZ	400	return 0;
	401	case SIGWINCH:
	402	DBG(SIG, ul_debugobj(pty, " get signal SIGWINCH"));
	403	if (pty->isterm) {
	404	ioctl(STDIN_FILENO, TIOCGWINSZ, (char *)&pty->win);
	405	ioctl(pty->slave, TIOCSWINSZ, (char *)&pty->win);
4f7f723b KZ	406
	407	if (pty->callbacks.log_signal)
	408	rc = pty->callbacks.log_signal(pty->callback_data,
	409	&info, (void *) &pty->win);
6954895c KZ	410	}
	411	break;
	412	case SIGTERM:
	413	/* fallthrough */
	414	case SIGINT:
	415	/* fallthrough */
	416	case SIGQUIT:
	417	DBG(SIG, ul_debugobj(pty, " get signal SIG{TERM,INT,QUIT}"));
	418	pty->delivered_signal = info.ssi_signo;
	419	/* Child termination is going to generate SIGCHILD (see above) */
	420	if (pty->child > 0)
	421	kill(pty->child, SIGTERM);
4f7f723b KZ	422
	423	if (pty->callbacks.log_signal)
	424	rc = pty->callbacks.log_signal(pty->callback_data,
	425	&info, (void *) &pty->win);
6954895c KZ	426	break;
	427	default:
	428	abort();
	429	}
	430
4f7f723b	431	return rc;
6954895c KZ	432	}
	433
	434	/* loop in parent */
	435	int ul_pty_proxy_master(struct ul_pty *pty)
	436	{
	437	sigset_t ourset;
	438	int rc = 0, ret, eof = 0;
	439	enum {
	440	POLLFD_SIGNAL = 0,
	441	POLLFD_MASTER,
	442	POLLFD_STDIN
	443
	444	};
	445	struct pollfd pfd[] = {
	446	[POLLFD_SIGNAL] = { .fd = -1, .events = POLLIN \| POLLERR \| POLLHUP },
	447	[POLLFD_MASTER] = { .fd = pty->master, .events = POLLIN \| POLLERR \| POLLHUP },
	448	[POLLFD_STDIN] = { .fd = STDIN_FILENO, .events = POLLIN \| POLLERR \| POLLHUP }
	449	};
	450
	451	/* We use signalfd and standard signals by handlers are blocked
	452	* at all
	453	*/
	454	sigfillset(&ourset);
	455	if (sigprocmask(SIG_BLOCK, &ourset, NULL))
	456	return -errno;
	457
	458	sigemptyset(&ourset);
	459	sigaddset(&ourset, SIGCHLD);
	460	sigaddset(&ourset, SIGWINCH);
	461	sigaddset(&ourset, SIGALRM);
	462	sigaddset(&ourset, SIGTERM);
	463	sigaddset(&ourset, SIGINT);
	464	sigaddset(&ourset, SIGQUIT);
	465
	466	if ((pty->sigfd = signalfd(-1, &ourset, SFD_CLOEXEC)) < 0) {
	467	rc = -errno;
	468	goto done;
	469	}
	470
	471	pfd[POLLFD_SIGNAL].fd = pty->sigfd;
	472	pty->poll_timeout = -1;
	473
	474	while (!pty->delivered_signal) {
	475	size_t i;
4d5b2fed KZ	476	int errsv, timeout;
	477
	478	DBG(IO, ul_debugobj(pty, "--poll() loop--"));
	479
	480	/* note, callback usually updates @next_callback_time */
	481	if (timerisset(&pty->next_callback_time)) {
	482	struct timeval now;
	483
	484	DBG(IO, ul_debugobj(pty, " callback requested"));
	485	gettime_monotonic(&now);
	486	if (timercmp(&now, &pty->next_callback_time, >)) {
	487	rc = mainloop_callback(pty);
	488	if (rc)
	489	break;
	490	}
	491	}
	492
	493	/* set timeout */
	494	if (timerisset(&pty->next_callback_time)) {
	495	struct timeval now, rest;
	496
	497	gettime_monotonic(&now);
	498	timersub(&pty->next_callback_time, &now, &rest);
	499	timeout = (rest.tv_sec * 1000) + (rest.tv_usec / 1000);
	500	} else
	501	timeout = pty->poll_timeout;
6954895c	502
4d5b2fed KZ	503	/* wait for input, signal or timeout */
	504	DBG(IO, ul_debugobj(pty, "calling poll() [timeout=%dms]", timeout));
	505	ret = poll(pfd, ARRAY_SIZE(pfd), timeout);
6954895c	506
6954895c KZ	507	errsv = errno;
	508	DBG(IO, ul_debugobj(pty, "poll() rc=%d", ret));
	509
4d5b2fed	510	/* error */
6954895c KZ	511	if (ret < 0) {
	512	if (errsv == EAGAIN)
	513	continue;
	514	rc = -errno;
	515	break;
	516	}
4d5b2fed KZ	517
4d5b2fed KZ	518	/* timeout */
6954895c	519	if (ret == 0) {
4d5b2fed KZ	520	if (timerisset(&pty->next_callback_time)) {
	521	rc = mainloop_callback(pty);
	522	if (rc == 0)
	523	continue;
	524	} else
	525	rc = 0;
	526
984082fa	527	DBG(IO, ul_debugobj(pty, "leaving poll() loop [timeout=%d, rc=%d]", timeout, rc));
6954895c KZ	528	break;
6954895c KZ	529	}
4d5b2fed	530	/* event */
6954895c KZ	531	for (i = 0; i < ARRAY_SIZE(pfd); i++) {
	532	rc = 0;
	533
	534	if (pfd[i].revents == 0)
	535	continue;
	536
	537	DBG(IO, ul_debugobj(pty, " active pfd[%s].fd=%d %s %s %s",
	538	i == POLLFD_STDIN ? "stdin" :
	539	i == POLLFD_MASTER ? "master" :
	540	i == POLLFD_SIGNAL ? "signal" : "???",
	541	pfd[i].fd,
	542	pfd[i].revents & POLLIN ? "POLLIN" : "",
	543	pfd[i].revents & POLLHUP ? "POLLHUP" : "",
	544	pfd[i].revents & POLLERR ? "POLLERR" : ""));
	545	switch (i) {
	546	case POLLFD_STDIN:
	547	case POLLFD_MASTER:
	548	/* data */
	549	if (pfd[i].revents & POLLIN)
	550	rc = handle_io(pty, pfd[i].fd, &eof);
	551	/* EOF maybe detected by two ways:
	552	* A) poll() return POLLHUP event after close()
	553	* B) read() returns 0 (no data) */
	554	if ((pfd[i].revents & POLLHUP) \|\| eof) {
	555	DBG(IO, ul_debugobj(pty, " ignore FD"));
	556	pfd[i].fd = -1;
	557	if (i == POLLFD_STDIN) {
	558	write_eof_to_child(pty);
	559	DBG(IO, ul_debugobj(pty, " ignore STDIN"));
	560	}
	561	}
	562	continue;
	563	case POLLFD_SIGNAL:
	564	rc = handle_signal(pty, pfd[i].fd);
	565	break;
	566	}
	567	if (rc)
	568	break;
	569	}
	570	}
	571
	572	done:
	573	if (pty->sigfd != -1)
	574	close(pty->sigfd);
	575	pty->sigfd = -1;
	576
	577	/* restore original setting */
	578	sigprocmask(SIG_SETMASK, &pty->orgsig, NULL);
	579
	580	DBG(IO, ul_debug("poll() done [signal=%d, rc=%d]", pty->delivered_signal, rc));
	581	return rc;
	582	}
	583
	584	#ifdef TEST_PROGRAM_PTY
	585	/*
	586	* $ make test_pty
	587	* $ ./test_pty
	588	*
	589	* ... and see for example tty(1) or "ps afu"
	590	*/
bdd43357	591	static void child_sigstop(void *data __attribute__((__unused__)), pid_t child)
6954895c	592	{
6954895c	593	kill(getpid(), SIGSTOP);
bdd43357	594	kill(child, SIGCONT);
6954895c KZ	595	}
	596
	597	int main(int argc, char *argv[])
	598	{
6954895c KZ	599	struct ul_pty_callbacks *cb;
	600	const char shell, command = NULL, *shname = NULL;
	601	int caught_signal = 0;
bdd43357	602	pid_t child;
8cf448e9	603	struct ul_pty *pty;
6954895c KZ	604
	605	shell = getenv("SHELL");
	606	if (shell == NULL)
	607	shell = _PATH_BSHELL;
	608	if (argc == 2)
	609	command = argv[1];
	610
	611	ul_pty_init_debug(0);
	612
8cf448e9 KZ	613	pty = ul_new_pty(isatty(STDIN_FILENO));
8cf448e9 KZ	614	if (!pty)
6954895c KZ	615	err(EXIT_FAILURE, "failed to allocate PTY handler");
6954895c KZ	616
8cf448e9	617	cb = ul_pty_get_callbacks(pty);
6954895c KZ	618	cb->child_sigstop = child_sigstop;
6954895c KZ	619
8cf448e9	620	if (ul_pty_setup(pty))
6954895c KZ	621	err(EXIT_FAILURE, "failed to create pseudo-terminal");
	622
	623	fflush(stdout); /* ??? */
	624
bdd43357	625	switch ((int) (child = fork())) {
6954895c	626	case -1: /* error */
8cf448e9	627	ul_pty_cleanup(pty);
6954895c KZ	628	err(EXIT_FAILURE, "cannot create child process");
	629	break;
	630
	631	case 0: /* child */
8cf448e9	632	ul_pty_init_slave(pty);
6954895c KZ	633
	634	signal(SIGTERM, SIG_DFL); /* because /etc/csh.login */
	635
	636	shname = strrchr(shell, '/');
	637	shname = shname ? shname + 1 : shell;
	638
	639	if (command)
	640	execl(shell, shname, "-c", command, NULL);
	641	else
	642	execl(shell, shname, "-i", NULL);
	643	err(EXIT_FAILURE, "failed to execute %s", shell);
	644	break;
	645
	646	default:
	647	break;
	648	}
	649
	650	/* parent */
8cf448e9	651	ul_pty_set_child(pty, child);
6954895c KZ	652
6954895c KZ	653	/* this is the main loop */
8cf448e9	654	ul_pty_proxy_master(pty);
6954895c KZ	655
6954895c KZ	656	/* all done; cleanup and kill */
8cf448e9	657	caught_signal = ul_pty_get_delivered_signal(pty);
6954895c	658
8cf448e9 KZ	659	if (!caught_signal && ul_pty_get_child(pty) != (pid_t)-1)
8cf448e9 KZ	660	ul_pty_wait_for_child(pty); /* final wait */
6954895c	661
8cf448e9	662	if (caught_signal && ul_pty_get_child(pty) != (pid_t)-1) {
6954895c	663	fprintf(stderr, "\nSession terminated, killing shell...");
bdd43357	664	kill(child, SIGTERM);
6954895c	665	sleep(2);
bdd43357	666	kill(child, SIGKILL);
6954895c KZ	667	fprintf(stderr, " ...killed.\n");
	668	}
	669
8cf448e9 KZ	670	ul_pty_cleanup(pty);
8cf448e9 KZ	671	ul_free_pty(pty);
6954895c KZ	672	return EXIT_SUCCESS;
	673	}
	674
	675	#endif /* TEST_PROGRAM */
	676