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/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 8 -*-
*
* written by Olaf Kirch <okir@suse.de>
* xscreensaver, Copyright (c) 1993-2004 Jamie Zawinski <jwz@jwz.org>
* Copyright (C) 2012-2021 MATE Developers
*
* Permission to use, copy, modify, distribute, and sell this software and its
* documentation for any purpose is hereby granted without fee, provided that
* the above copyright notice appear in all copies and that both that
* copyright notice and this permission notice appear in supporting
* documentation. No representations are made about the suitability of this
* software for any purpose. It is provided "as is" without express or
* implied warranty.
*/
/* The idea here is to be able to run mate-screensaver-dialog without any setuid bits.
* Password verification happens through an external program that you feed
* your password to on stdin. The external command is invoked with a user
* name argument.
*
* The external helper does whatever authentication is necessary. Currently,
* SuSE uses "unix2_chkpwd", which is a variation of "unix_chkpwd" from the
* PAM distribution.
*
* Normally, the password helper should just authenticate the calling user
* (i.e. based on the caller's real uid). This is in order to prevent
* brute-forcing passwords in a shadow environment. A less restrictive
* approach would be to allow verifying other passwords as well, but always
* with a 2 second delay or so. (Not sure what SuSE's "unix2_chkpwd"
* currently does.)
* -- Olaf Kirch <okir@suse.de>, 16-Dec-2003
*/
#include "config.h"
#include <stdlib.h>
#ifdef HAVE_UNISTD_H
# include <unistd.h>
#endif
#include <stdio.h>
#include <string.h>
#include <sys/types.h>
#include <pwd.h>
#include <errno.h>
#include <sys/wait.h>
#include <glib.h>
#include <glib/gstdio.h>
#include "gs-auth.h"
#include "subprocs.h"
static gboolean verbose_enabled = FALSE;
GQuark
gs_auth_error_quark (void)
{
static GQuark quark = 0;
if (! quark)
{
quark = g_quark_from_static_string ("gs_auth_error");
}
return quark;
}
void
gs_auth_set_verbose (gboolean enabled)
{
verbose_enabled = enabled;
}
gboolean
gs_auth_get_verbose (void)
{
return verbose_enabled;
}
static gboolean
ext_run (const char *user,
const char *typed_passwd,
gboolean verbose)
{
int pfd[2], status;
pid_t pid;
if (pipe (pfd) < 0)
{
return 0;
}
if (verbose)
{
g_message ("ext_run (%s, %s)",
PASSWD_HELPER_PROGRAM, user);
}
block_sigchld ();
if ((pid = fork ()) < 0)
{
close (pfd [0]);
close (pfd [1]);
return FALSE;
}
if (pid == 0)
{
close (pfd [1]);
if (pfd [0] != 0)
{
dup2 (pfd [0], 0);
}
/* Helper is invoked as helper service-name [user] */
execlp (PASSWD_HELPER_PROGRAM, PASSWD_HELPER_PROGRAM, "mate-screensaver", user, NULL);
if (verbose)
{
g_message ("%s: %s", PASSWD_HELPER_PROGRAM, g_strerror (errno));
}
exit (1);
}
close (pfd [0]);
/* Write out password to helper process */
if (!typed_passwd)
{
typed_passwd = "";
}
write (pfd [1], typed_passwd, strlen (typed_passwd));
close (pfd [1]);
while (waitpid (pid, &status, 0) < 0)
{
if (errno == EINTR)
{
continue;
}
if (verbose)
{
g_message ("ext_run: waitpid failed: %s\n",
g_strerror (errno));
}
unblock_sigchld ();
return FALSE;
}
unblock_sigchld ();
if (! WIFEXITED (status) || WEXITSTATUS (status) != 0)
{
return FALSE;
}
return TRUE;
}
gboolean
gs_auth_verify_user (const char *username,
const char *display,
GSAuthMessageFunc func,
gpointer data,
GError **error)
{
gboolean res = FALSE;
char *password;
password = NULL;
/* ask for the password for user */
if (func != NULL)
{
func (GS_AUTH_MESSAGE_PROMPT_ECHO_OFF,
"Password: ",
&password,
data);
}
if (password == NULL)
{
return FALSE;
}
res = ext_run (username, password, gs_auth_get_verbose ());
return res;
}
gboolean
gs_auth_init (void)
{
return TRUE;
}
gboolean
gs_auth_priv_init (void)
{
/* Make sure the passwd helper exists */
if (g_access (PASSWD_HELPER_PROGRAM, X_OK) < 0)
{
g_warning ("%s does not exist. "
"password authentication via "
"external helper will not work.",
PASSWD_HELPER_PROGRAM);
return FALSE;
}
return TRUE;
}
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