/*                               -*- Mode: C -*- 
 * open_init_pty.c --- 
 * Author           : Manoj Srivastava ( srivasta@glaurung.internal.golden-gryphon.com ) 
 * Created On       : Fri Jan 14 10:48:28 2005
 * Created On Node  : glaurung.internal.golden-gryphon.com
 * Last Modified By : Manoj Srivastava
 * Last Modified On : Thu Sep 15 00:57:00 2005
 * Last Machine Used: glaurung.internal.golden-gryphon.com
 * Update Count     : 92
 * Status           : Unknown, Use with caution!
 * HISTORY          : 
 * Description      : 
 *
 * Distributed under the terms of the GNU General Public License v2
 *
 * open_init_pty
 *
 * SYNOPSIS:
 *
 * This program allows a systems administrator to execute daemons
 * which need to work in the initrc domain, and which need to have
 * pty's as system_u:system_r:initrc_t
 *
 * USAGE:
 *
 * * arch-tag: a5583d39-72b9-4cdf-ba1b-5678ea4cbe20
 */

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <errno.h>

#include <sysexits.h>

#include <pty.h>		/* for openpty and forkpty */
#include <utmp.h>		/* for login_tty */
#include <termios.h>
#include <fcntl.h>

#include <sys/select.h>

static struct termios saved_termios;
static int saved_fd = -1;
static enum { RESET, RAW, CBREAK } tty_state = RESET;

static int tty_semi_raw(int fd)
{
	struct termios buf;

	if (tty_state == RESET) {
		if (tcgetattr(fd, &saved_termios) < 0) {
			return -1;
		}
	}

	buf = saved_termios;
	/*
	 * echo off, canonical mode off, extended input processing off,
	 * signal chars off 
	 */
	buf.c_lflag &= ~(ECHO | ICANON | IEXTEN | ISIG);
	/*
	 * no SIGINT on break, CR-to-NL off, input parity check off, do not
	 * strip 8th bit on input,output flow control off
	 */
	buf.c_iflag &= ~(BRKINT | ICRNL | INPCK | ISTRIP | IXON);
	/* Clear size bits, parity checking off */
	buf.c_cflag &= ~(CSIZE | PARENB);
	/* set 8 bits/char */
	buf.c_cflag |= CS8;
	/* Output processing off 
	   buf.c_oflag    &= ~(OPOST); */

	buf.c_cc[VMIN] = 1;	/* one byte at a time, no timer */
	buf.c_cc[VTIME] = 0;
	if (tcsetattr(fd, TCSANOW, &buf) < 0) {
		return -1;
	}			/* end of if(tcsetattr(fileno(stdin), TCSANOW, &buf) < 0) */
	tty_state = RAW;
	saved_fd = fd;
	return 0;
}

void tty_atexit(void)
{
	if (tty_state != CBREAK && tty_state != RAW) {
		return;
	}

	if (tcsetattr(saved_fd, TCSANOW, &saved_termios) < 0) {
		return;
	}			/* end of if(tcsetattr(fileno(stdin), TCSANOW, &buf) < 0) */
	tty_state = RESET;
	return;
}

int main(int argc, char *argv[])
{
	pid_t child_pid;
	struct termios tty_attr;
	struct winsize window_size;
	int pty_master;
	int retval = 0;

	/* for select */
	fd_set readfds;
	fd_set writefds;
	fd_set exceptfds;

	int err_count = 0;

	/* for sigtimedwait() */
	struct timespec timeout;
	char buf[16384];

	if (argc == 1) {
		printf("usage: %s PROGRAM [ARGS]...\n", argv[0]);
		exit(1);
	}

	sigset_t signal_set;
	siginfo_t signalinfo;

	/* set up SIGCHLD */
	sigemptyset(&signal_set);	/* no signals */
	sigaddset(&signal_set, SIGCHLD);	/* Add sig child  */
	sigprocmask(SIG_BLOCK, &signal_set, NULL);	/* Block the signal */

	/* Set both to 0, so sigtimed wait just does a poll */
	timeout.tv_sec = 0;
	timeout.tv_nsec = 0;

	if (isatty(fileno(stdin))) {
		/* get terminal parameters associated with stdout */
		if (tcgetattr(fileno(stdout), &tty_attr) < 0) {
			perror("tcgetattr:");
			exit(EX_OSERR);
		}

		/* end of if(tcsetattr(&tty_attr)) */
		/* get window size */
		if (ioctl(fileno(stdout), TIOCGWINSZ, &window_size) < 0) {
			perror("ioctl stdout:");
			exit(1);
		}

		child_pid = forkpty(&pty_master, NULL, &tty_attr, &window_size);
	} /* end of if(isatty(fileno(stdin))) */
	else {			/* not interactive */
		child_pid = forkpty(&pty_master, NULL, NULL, NULL);
	}

	if (child_pid < 0) {
		perror("forkpty():");
		fflush(stdout);
		fflush(stderr);
		exit(EX_OSERR);
	}			/* end of if(child_pid < 0) */
	if (child_pid == 0) {
		/* in the child */
		struct termios s_tty_attr;
		if (tcgetattr(fileno(stdin), &s_tty_attr)) {
			perror("forkpty child:");
			fflush(stdout);
			fflush(stderr);
			exit(EXIT_FAILURE);
		}
		/* Turn off echo */
		s_tty_attr.c_lflag &= ~(ECHO | ECHOE | ECHOK | ECHONL);
		/* Also turn of NL to CR?LF on output */
		s_tty_attr.c_oflag &= ~(ONLCR);
		if (tcsetattr(fileno(stdin), TCSANOW, &s_tty_attr)) {
			perror("Child:");
			exit(EXIT_FAILURE);
		}
		{		/* There is no reason to block sigchild for the process we
				   shall exec here */
			sigset_t chld_signal_set;
			/* release SIGCHLD */
			sigemptyset(&chld_signal_set);	/* no signals */
			sigaddset(&chld_signal_set, SIGCHLD);	/* Add sig child  */
			sigprocmask(SIG_UNBLOCK, &chld_signal_set, NULL);	/* Unblock the signal */
		}

		if (execvp(argv[1], argv + 1)) {
			perror("Exec:");
			fflush(stdout);
			fflush(stderr);
			exit(EXIT_FAILURE);
		}
	}

	/* end of if(child_pid == 0) */
	/* 
	 * OK. Prepare to handle IO from the child. We need to transfer
	 * everything from the child's stdout to ours.
	 */
	FD_ZERO(&readfds);
	FD_ZERO(&writefds);
	FD_ZERO(&exceptfds);

	/*
	 * Read current file descriptor flags, preparing to do non blocking reads
	 */
	retval = fcntl(pty_master, F_GETFL);
	if (retval < 0) {
		perror("fcntl_get");
		fflush(stdout);
		fflush(stderr);
		exit(EX_IOERR);
	}

	/* Set the connection to be non-blocking */
	if (fcntl(pty_master, F_SETFL, retval | O_NONBLOCK) < 0) {
		perror("fcnt_setFlag_nonblock:");
		fflush(stdout);
		fflush(stderr);
		exit(1);
	}

	FD_SET(pty_master, &readfds);
	FD_SET(pty_master, &writefds);
	FD_SET(fileno(stdin), &readfds);
	if (isatty(fileno(stdin))) {
		if (tty_semi_raw(fileno(stdin)) < 0) {
			perror("Error: settingraw mode:");
			fflush(stdout);
			fflush(stderr);
		}		/* end of if(tty_raw(fileno(stdin)) < 0) */
		if (atexit(tty_atexit) < 0) {
			perror("Atexit setup:");
			fflush(stdout);
			fflush(stderr);
		}		/* end of if(atexit(tty_atexit) < 0) */
	}

	/* ignore return from nice, but lower our priority */
	int ignore __attribute__ ((unused)) = nice(19);

	/* while no signal, we loop around */
	int done = 0;
	while (!done) {
		struct timeval interval;
		fd_set t_readfds;
		fd_set t_writefds;
		fd_set t_exceptfds;
		/*
		 * We still use a blocked signal, and check for SIGCHLD every
		 * loop, since waiting infinitely did not really help the load
		 * when running, say, top. 
		 */
		interval.tv_sec = 0;
		interval.tv_usec = 200000;	/* so, check for signals every 200 milli
						   seconds */

		t_readfds = readfds;
		t_writefds = writefds;
		t_exceptfds = exceptfds;

		/* check for the signal */
		retval = sigtimedwait(&signal_set, &signalinfo, &timeout);

		if (retval == SIGCHLD) {
			/* child terminated */
			done = 1;	/* in case they do not close off their
					   file descriptors */
		} else {
			if (retval < 0) {
				if (errno != EAGAIN) {
					perror("sigtimedwait");
					fflush(stdout);
					fflush(stderr);
					exit(EX_IOERR);
				} else {
					/* No signal in set was delivered within the timeout period specified */
				}
			}
		}		/* end of else */

		if (select
		    (pty_master + 1, &t_readfds, &t_writefds, &t_exceptfds,
		     &interval) < 0) {
			perror("Select:");
			fflush(stdout);
			fflush(stderr);
			exit(EX_IOERR);
		}

		if (FD_ISSET(pty_master, &t_readfds)) {
			retval = read(pty_master, buf, (unsigned int)16384);
			if (retval < 0) {
				if (errno != EINTR && errno != EAGAIN) {	/* Nothing left to read?  */
					fflush(stdout);
					fflush(stderr);
					/* fprintf(stderr, "DEBUG: %d: Nothing left to read?\n", __LINE__); */
					exit(EXIT_SUCCESS);
				}	/* end of else */
			} /* end of if(retval < 0) */
			else {
				if (retval == 0) {
					if (++err_count > 5) {	/* child closed connection */
						fflush(stdout);
						fflush(stderr);
						/*fprintf(stderr, "DEBUG: %d: child closed connection?\n", __LINE__); */
						exit(EXIT_SUCCESS);
					}
				} /* end of if(retval == 0) */
				else {
					ssize_t nleft = retval;
					ssize_t nwritten = 0;
					char *ptr = buf;
					while (nleft > 0) {
						if ((nwritten =
						     write(fileno(stdout), ptr,
							   (unsigned int)nleft))
						    <= 0) {
							if (errno == EINTR) {
								nwritten = 0;
							} /* end of if(errno == EINTR) */
							else {
								perror("write");
								fflush(stdout);
								fflush(stderr);
								exit(EXIT_SUCCESS);
							}	/* end of else */
						}	/* end of if((nwritten = write(sockfd, ptr, nleft)) <= 0) */
						nleft -= nwritten;
						ptr += nwritten;
					}	/* end of while(nleft > 0) */

					/* fprintf(stderr, "DEBUG: %d: wrote %d\n", __LINE__, retval); */
					fflush(stdout);
				}	/* end of else */
			}	/* end of else */
		}
		if (FD_ISSET(fileno(stdin), &t_readfds)) {
			if (FD_ISSET(pty_master, &t_writefds)) {
				retval =
				    read(fileno(stdin), buf,
					 (unsigned int)16384);
				if (retval < 0) {
					if (errno != EINTR && errno != EAGAIN) {	/* Nothing left to read?  */
						fflush(stdout);
						fflush(stderr);
						exit(EXIT_SUCCESS);
					}	/* end of else */
				} /* end of if(retval < 0) */
				else {
					if (retval == 0) {
						if (++err_count > 5) {	/* lost controlling tty */
							fflush(stdout);
							fflush(stderr);
							exit(EXIT_SUCCESS);
						}
					} /* end of if(retval == 0) */
					else {
						ssize_t nleft = retval;
						ssize_t nwritten = 0;
						char *ptr = buf;
						while (nleft > 0) {
							if ((nwritten =
							     write(pty_master,
								   ptr,
								   (unsigned
								    int)nleft))
							    <= 0) {
								if (errno ==
								    EINTR) {
									nwritten
									    = 0;
								} /* end of if(errno == EINTR) */
								else {
									perror
									    ("write");
									fflush
									    (stdout);
									fflush
									    (stderr);
									exit(EXIT_SUCCESS);
								}	/* end of else */
							}	/* end of if((nwritten = write(sockfd, ptr, nleft)) <= 0) */
							nleft -= nwritten;
							ptr += nwritten;
						}	/* end of while(nleft > 0) */

						fflush(stdout);
					}	/* end of else */
				}	/* end of else */
			}	/* end of if(FD_ISSET(pty_master, &writefds)) */
		}		/* something to read on stdin */
	}			/* Loop */

	fflush(stdout);
	fflush(stderr);

	exit(EXIT_SUCCESS);
}				/* end of main() */