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/*
Copyright (C) 2002-2025 Free Software Foundation, Inc.
This file is part of GNU Inetutils.
GNU Inetutils is free software: you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation, either version 3 of the License, or (at
your option) any later version.
GNU Inetutils is distributed in the hope that it will be useful, but
WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program. If not, see `http://www.gnu.org/licenses/'. */
#include <config.h>
#include "telnetd.h"
#include <sys/wait.h>
#include <pty.h>
#ifdef AUTHENTICATION
# include <libtelnet/auth.h>
#endif
#include <libinetutils.h>
void
setup_utmp (char *line, char *host)
{
char *ut_id = utmp_ptsid (line, "tn");
utmp_init (line + sizeof (PATH_TTY_PFX) - 1, ".telnet", ut_id, host);
}
int
startslave (char *host, int autologin, char *autoname)
{
pid_t pid;
int master;
#ifdef AUTHENTICATION
if (!autoname || !autoname[0])
autologin = 0;
if (autologin < auth_level)
{
fatal (net, "Authorization failed");
exit (EXIT_FAILURE);
}
#else /* !AUTHENTICATION */
(void) autoname; /* Silence warnings. */
#endif
pid = forkpty (&master, line, NULL, NULL);
if (pid < 0)
{
if (errno == ENOENT)
{
syslog (LOG_ERR, "Out of ptys");
fatal (net, "Out of ptys");
}
else
{
syslog (LOG_ERR, "forkpty: %m");
fatal (net, "Forkpty");
}
}
if (pid == 0)
{
/* Child */
if (net > 2)
close (net);
setup_utmp (line, host);
start_login (host, autologin, line);
}
/* Master */
return master;
}
/*
* scrub_env()
*
* Remove a few things from the environment that
* don't need to be there.
*
* Security fix included in telnet-95.10.23.NE of David Borman <deb@cray.com>.
*/
static void
scrub_env (void)
{
char **cpp, **cpp2;
for (cpp2 = cpp = environ; *cpp; cpp++)
{
if (strncmp (*cpp, "LD_", 3)
&& strncmp (*cpp, "_RLD_", 5)
&& strncmp (*cpp, "LIBPATH=", 8) && strncmp (*cpp, "IFS=", 4))
*cpp2++ = *cpp;
}
*cpp2 = 0;
}
void
start_login (char *host, int autologin, char *name)
{
char *cmd;
int argc;
char **argv;
(void) host; /* Silence warnings. Diagnostic use? */
(void) autologin;
(void) name;
scrub_env ();
/* Set the environment variable "LINEMODE" to indicate our linemode */
if (lmodetype == REAL_LINEMODE)
setenv ("LINEMODE", "real", 1);
else if (lmodetype == KLUDGE_LINEMODE || lmodetype == KLUDGE_OK)
setenv ("LINEMODE", "kludge", 1);
cmd = expand_line (login_invocation);
if (!cmd)
fatal (net, "can't expand login command line");
argcv_get (cmd, "", &argc, &argv);
execv (argv[0], argv);
syslog (LOG_ERR, "%s: %m\n", cmd);
fatalperror (net, cmd);
}
/* SIG is generally naught every time the server itself
* decides to close the connection out of an error condition.
* In response to TELOPT_LOGOUT from the client, SIG is set
* to SIGHUP, so we consider the exit as a success. In other
* cases, when the forked client process is caught exiting,
* then SIG will be SIGCHLD. Then we deliver the clients's
* reported exit code.
*/
void
cleanup (int sig)
{
int status = EXIT_FAILURE;
char *p;
if (sig == SIGCHLD)
{
pid_t pid = waitpid ((pid_t) - 1, &status, WNOHANG);
syslog (LOG_INFO, "child process %ld exited: %d",
(long) pid, WEXITSTATUS (status));
status = WEXITSTATUS (status);
}
else if (sig == SIGHUP)
status = EXIT_SUCCESS; /* Response to TELOPT_LOGOUT. */
p = line + sizeof (PATH_TTY_PFX) - 1;
utmp_logout (p);
chmod (line, 0644);
chown (line, 0, 0);
shutdown (net, 2);
exit (status);
}
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