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authorPerberos <[email protected]>2011-11-04 22:16:15 -0300
committerPerberos <[email protected]>2011-11-04 22:16:15 -0300
commitfff4ecc82f2bcfa7427596e7ad9c3769fcab040b (patch)
treeac4f1812a7991609c9c32c776daede2d8492f7b5 /src/gs-auth-helper.c
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+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 8 -*-
+ *
+ * written by Olaf Kirch <[email protected]>
+ * xscreensaver, Copyright (c) 1993-2004 Jamie Zawinski <[email protected]>
+ *
+ * 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 <[email protected]>, 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;
+}