+#ifndef UTMP_FILE
+#define UTMP_FILE "/var/run/utmp"
+#endif
+#ifndef WTMP_FILE
+#define WTMP_FILE "/var/log/wtmp"
+#endif
+#ifndef LASTLOG_FILE
+#ifdef _PATH_LASTLOG
+#define LASTLOG_FILE _PATH_LASTLOG
+#else
+#define LASTLOG_FILE "/var/log/lastlog"
+#endif
+#endif
+
+/*
+ * Set up a default for vaguely sane systems. The idea is that if
+ * OMIT_UTMP is not defined, then at least one of the symbols which
+ * enable particular forms of utmp processing should be, if only so
+ * that a link error can warn you that you should have defined
+ * OMIT_UTMP if you didn't want any. Currently HAVE_PUTUTLINE is
+ * the only such symbol.
+ */
+#ifndef OMIT_UTMP
+#if !defined HAVE_PUTUTLINE
+#define HAVE_PUTUTLINE
+#endif
+#endif
+
+static Config pty_cfg;
+static int pty_master_fd;
+static void *pty_frontend;
+static char pty_name[FILENAME_MAX];
+static int pty_signal_pipe[2];
+static int pty_child_pid;
+static int pty_term_width, pty_term_height;
+static int pty_child_dead, pty_finished;
+static int pty_exit_code;
+char **pty_argv;
+int use_pty_argv = TRUE;
+
+static void pty_close(void);
+
+#ifndef OMIT_UTMP
+static int pty_utmp_helper_pid, pty_utmp_helper_pipe;
+static int pty_stamped_utmp = 0;
+static struct utmp utmp_entry;
+
+static void setup_utmp(char *ttyname, char *location)
+{
+#ifdef HAVE_LASTLOG
+ struct lastlog lastlog_entry;
+ FILE *lastlog;
+#endif
+ struct passwd *pw;
+ FILE *wtmp;
+ time_t uttime;
+
+ pw = getpwuid(getuid());
+ memset(&utmp_entry, 0, sizeof(utmp_entry));
+ utmp_entry.ut_type = USER_PROCESS;
+ utmp_entry.ut_pid = getpid();
+ strncpy(utmp_entry.ut_line, ttyname+5, lenof(utmp_entry.ut_line));
+ strncpy(utmp_entry.ut_id, ttyname+8, lenof(utmp_entry.ut_id));
+ strncpy(utmp_entry.ut_user, pw->pw_name, lenof(utmp_entry.ut_user));
+ strncpy(utmp_entry.ut_host, location, lenof(utmp_entry.ut_host));
+ /* Apparently there are some architectures where (struct utmp).ut_time
+ * is not essentially time_t (e.g. Linux amd64). Hence the temporary. */
+ time(&uttime);
+ utmp_entry.ut_time = uttime; /* may truncate */
+
+#if defined HAVE_PUTUTLINE
+ utmpname(UTMP_FILE);
+ setutent();
+ pututline(&utmp_entry);
+ endutent();
+#endif
+
+ if ((wtmp = fopen(WTMP_FILE, "a")) != NULL) {
+ fwrite(&utmp_entry, 1, sizeof(utmp_entry), wtmp);
+ fclose(wtmp);
+ }
+
+#ifdef HAVE_LASTLOG
+ memset(&lastlog_entry, 0, sizeof(lastlog_entry));
+ strncpy(lastlog_entry.ll_line, ttyname+5, lenof(lastlog_entry.ll_line));
+ strncpy(lastlog_entry.ll_host, location, lenof(lastlog_entry.ll_host));
+ time(&lastlog_entry.ll_time);
+ if ((lastlog = fopen(LASTLOG_FILE, "r+")) != NULL) {
+ fseek(lastlog, sizeof(lastlog_entry) * getuid(), SEEK_SET);
+ fwrite(&lastlog_entry, 1, sizeof(lastlog_entry), lastlog);
+ fclose(lastlog);
+ }
+#endif
+
+ pty_stamped_utmp = 1;
+
+}
+
+static void cleanup_utmp(void)
+{
+ FILE *wtmp;
+ time_t uttime;
+
+ if (!pty_stamped_utmp)
+ return;
+
+ utmp_entry.ut_type = DEAD_PROCESS;
+ memset(utmp_entry.ut_user, 0, lenof(utmp_entry.ut_user));
+ time(&uttime);
+ utmp_entry.ut_time = uttime;
+
+ if ((wtmp = fopen(WTMP_FILE, "a")) != NULL) {
+ fwrite(&utmp_entry, 1, sizeof(utmp_entry), wtmp);
+ fclose(wtmp);
+ }
+
+ memset(utmp_entry.ut_line, 0, lenof(utmp_entry.ut_line));
+ utmp_entry.ut_time = 0;
+
+#if defined HAVE_PUTUTLINE
+ utmpname(UTMP_FILE);
+ setutent();
+ pututline(&utmp_entry);
+ endutent();
+#endif
+
+ pty_stamped_utmp = 0; /* ensure we never double-cleanup */
+}
+#endif
+
+static void sigchld_handler(int signum)
+{
+ write(pty_signal_pipe[1], "x", 1);
+}
+
+#ifndef OMIT_UTMP
+static void fatal_sig_handler(int signum)
+{
+ putty_signal(signum, SIG_DFL);
+ cleanup_utmp();
+ setuid(getuid());
+ raise(signum);
+}
+#endif
+
+static void pty_open_master(void)
+{
+#ifdef BSD_PTYS
+ const char chars1[] = "pqrstuvwxyz";
+ const char chars2[] = "0123456789abcdef";
+ const char *p1, *p2;
+ char master_name[20];
+ struct group *gp;
+
+ for (p1 = chars1; *p1; p1++)
+ for (p2 = chars2; *p2; p2++) {
+ sprintf(master_name, "/dev/pty%c%c", *p1, *p2);
+ pty_master_fd = open(master_name, O_RDWR);
+ if (pty_master_fd >= 0) {
+ if (geteuid() == 0 ||
+ access(master_name, R_OK | W_OK) == 0)
+ goto got_one;
+ close(pty_master_fd);
+ }
+ }
+
+ /* If we get here, we couldn't get a tty at all. */
+ fprintf(stderr, "pterm: unable to open a pseudo-terminal device\n");
+ exit(1);
+
+ got_one:
+ strcpy(pty_name, master_name);
+ pty_name[5] = 't'; /* /dev/ptyXX -> /dev/ttyXX */
+
+ /* We need to chown/chmod the /dev/ttyXX device. */
+ gp = getgrnam("tty");
+ chown(pty_name, getuid(), gp ? gp->gr_gid : -1);
+ chmod(pty_name, 0600);
+#else
+ pty_master_fd = open("/dev/ptmx", O_RDWR);
+
+ if (pty_master_fd < 0) {
+ perror("/dev/ptmx: open");
+ exit(1);
+ }
+
+ if (grantpt(pty_master_fd) < 0) {
+ perror("grantpt");
+ exit(1);
+ }
+
+ if (unlockpt(pty_master_fd) < 0) {
+ perror("unlockpt");
+ exit(1);
+ }
+
+ pty_name[FILENAME_MAX-1] = '\0';
+ strncpy(pty_name, ptsname(pty_master_fd), FILENAME_MAX-1);
+#endif
+}
+
+/*
+ * Pre-initialisation. This is here to get around the fact that GTK
+ * doesn't like being run in setuid/setgid programs (probably
+ * sensibly). So before we initialise GTK - and therefore before we
+ * even process the command line - we check to see if we're running
+ * set[ug]id. If so, we open our pty master _now_, chown it as
+ * necessary, and drop privileges. We can always close it again
+ * later. If we're potentially going to be doing utmp as well, we
+ * also fork off a utmp helper process and communicate with it by
+ * means of a pipe; the utmp helper will keep privileges in order
+ * to clean up utmp when we exit (i.e. when its end of our pipe
+ * closes).
+ */
+void pty_pre_init(void)
+{
+#ifndef OMIT_UTMP
+ pid_t pid;
+ int pipefd[2];
+#endif
+
+ /* set the child signal handler straight away; it needs to be set
+ * before we ever fork. */
+ putty_signal(SIGCHLD, sigchld_handler);
+ pty_master_fd = -1;
+
+ if (geteuid() != getuid() || getegid() != getgid()) {
+ pty_open_master();
+ }
+
+#ifndef OMIT_UTMP
+ /*
+ * Fork off the utmp helper.
+ */
+ if (pipe(pipefd) < 0) {
+ perror("pterm: pipe");
+ exit(1);
+ }
+ pid = fork();
+ if (pid < 0) {
+ perror("pterm: fork");
+ exit(1);
+ } else if (pid == 0) {
+ char display[128], buffer[128];
+ int dlen, ret;
+
+ close(pipefd[1]);
+ /*
+ * Now sit here until we receive a display name from the
+ * other end of the pipe, and then stamp utmp. Unstamp utmp
+ * again, and exit, when the pipe closes.
+ */
+
+ dlen = 0;
+ while (1) {
+
+ ret = read(pipefd[0], buffer, lenof(buffer));
+ if (ret <= 0) {
+ cleanup_utmp();
+ _exit(0);
+ } else if (!pty_stamped_utmp) {
+ if (dlen < lenof(display))
+ memcpy(display+dlen, buffer,
+ min(ret, lenof(display)-dlen));
+ if (buffer[ret-1] == '\0') {
+ /*
+ * Now we have a display name. NUL-terminate
+ * it, and stamp utmp.
+ */
+ display[lenof(display)-1] = '\0';
+ /*
+ * Trap as many fatal signals as we can in the
+ * hope of having the best possible chance to
+ * clean up utmp before termination. We are
+ * unfortunately unprotected against SIGKILL,
+ * but that's life.
+ */
+ putty_signal(SIGHUP, fatal_sig_handler);
+ putty_signal(SIGINT, fatal_sig_handler);
+ putty_signal(SIGQUIT, fatal_sig_handler);
+ putty_signal(SIGILL, fatal_sig_handler);
+ putty_signal(SIGABRT, fatal_sig_handler);
+ putty_signal(SIGFPE, fatal_sig_handler);
+ putty_signal(SIGPIPE, fatal_sig_handler);
+ putty_signal(SIGALRM, fatal_sig_handler);
+ putty_signal(SIGTERM, fatal_sig_handler);
+ putty_signal(SIGSEGV, fatal_sig_handler);
+ putty_signal(SIGUSR1, fatal_sig_handler);
+ putty_signal(SIGUSR2, fatal_sig_handler);
+#ifdef SIGBUS
+ putty_signal(SIGBUS, fatal_sig_handler);
+#endif
+#ifdef SIGPOLL
+ putty_signal(SIGPOLL, fatal_sig_handler);
+#endif
+#ifdef SIGPROF
+ putty_signal(SIGPROF, fatal_sig_handler);
+#endif
+#ifdef SIGSYS
+ putty_signal(SIGSYS, fatal_sig_handler);
+#endif
+#ifdef SIGTRAP
+ putty_signal(SIGTRAP, fatal_sig_handler);
+#endif
+#ifdef SIGVTALRM
+ putty_signal(SIGVTALRM, fatal_sig_handler);
+#endif
+#ifdef SIGXCPU
+ putty_signal(SIGXCPU, fatal_sig_handler);
+#endif
+#ifdef SIGXFSZ
+ putty_signal(SIGXFSZ, fatal_sig_handler);
+#endif
+#ifdef SIGIO
+ putty_signal(SIGIO, fatal_sig_handler);
+#endif
+ setup_utmp(pty_name, display);
+ }
+ }
+ }
+ } else {
+ close(pipefd[0]);
+ pty_utmp_helper_pid = pid;
+ pty_utmp_helper_pipe = pipefd[1];
+ }
+#endif
+
+ /* Drop privs. */
+ {
+#ifndef HAVE_NO_SETRESUID
+ int gid = getgid(), uid = getuid();
+ int setresgid(gid_t, gid_t, gid_t);
+ int setresuid(uid_t, uid_t, uid_t);
+ setresgid(gid, gid, gid);
+ setresuid(uid, uid, uid);
+#else
+ setgid(getgid());
+ setuid(getuid());
+#endif
+ }
+}