first commit

1 files changed, 247 insertions, 0 deletions

diff --git a/src/setuid.c.orig b/src/setuid.c.orig
new file mode 100644
index 0000000..2c55c2e
--- /dev/null
+++ b/src/setuid.c.orig
@@ -0,0 +1,247 @@
+/* -*- Mode: C; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 8 -*-
+ *
+ * setuid.c --- management of runtime privileges.
+ *
+ * xscreensaver, Copyright (c) 1993-1998 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.
+ */
+
+#include "config.h"
+
+#ifndef EPERM
+#include <errno.h>
+#endif
+
+#include <stdio.h>
+#include <string.h>
+#include <sys/types.h>
+#include <unistd.h>
+#include <pwd.h>		/* for getpwnam() and struct passwd */
+#include <grp.h>		/* for getgrgid() and struct group */
+#include <glib.h>
+
+#include "setuid.h"
+
+static char *
+uid_gid_string (uid_t uid,
+                gid_t gid)
+{
+    static char   *buf;
+    struct passwd *p = NULL;
+    struct group  *g = NULL;
+
+    p = getpwuid (uid);
+    g = getgrgid (gid);
+
+    buf = g_strdup_printf ("%s/%s (%ld/%ld)",
+                           (p && p->pw_name ? p->pw_name : "???"),
+                           (g && g->gr_name ? g->gr_name : "???"),
+                           (long) uid, (long) gid);
+
+    return buf;
+}
+
+static gboolean
+set_ids_by_number (uid_t  uid,
+                   gid_t  gid,
+                   char **message_ret)
+{
+    int uid_errno = 0;
+    int gid_errno = 0;
+    int sgs_errno = 0;
+    struct passwd *p = getpwuid (uid);
+    struct group  *g = getgrgid (gid);
+
+    if (message_ret)
+        *message_ret = NULL;
+
+    /* Rumor has it that some implementations of of setuid() do nothing
+       when called with -1; therefore, if the "nobody" user has a uid of
+       -1, then that would be Really Bad.  Rumor further has it that such
+       systems really ought to be using -2 for "nobody", since that works.
+       So, if we get a uid (or gid, for good measure) of -1, switch to -2
+       instead.  Note that this must be done after we've looked up the
+       user/group names with getpwuid(-1) and/or getgrgid(-1).
+    */
+    if (gid == (gid_t) -1) gid = (gid_t) -2;
+    if (uid == (uid_t) -1) uid = (uid_t) -2;
+
+    errno = 0;
+    if (setgroups (1, &gid) < 0)
+        sgs_errno = errno ? errno : -1;
+
+    errno = 0;
+    if (setgid (gid) != 0)
+        gid_errno = errno ? errno : -1;
+
+    errno = 0;
+    if (setuid (uid) != 0)
+        uid_errno = errno ? errno : -1;
+
+    if (uid_errno == 0 && gid_errno == 0 && sgs_errno == 0)
+    {
+        static char *reason;
+        reason = g_strdup_printf ("changed uid/gid to %s/%s (%ld/%ld).",
+                                  (p && p->pw_name ? p->pw_name : "???"),
+                                  (g && g->gr_name ? g->gr_name : "???"),
+                                  (long) uid, (long) gid);
+        if (message_ret)
+            *message_ret = g_strdup (reason);
+
+        g_free (reason);
+
+        return TRUE;
+    }
+    else
+    {
+        char *reason = NULL;
+
+        if (sgs_errno)
+        {
+            reason = g_strdup_printf ("couldn't setgroups to %s (%ld)",
+                                      (g && g->gr_name ? g->gr_name : "???"),
+                                      (long) gid);
+            if (sgs_errno == -1)
+                fprintf (stderr, "%s: unknown error\n", reason);
+            else
+            {
+                errno = sgs_errno;
+                perror (reason);
+            }
+            g_free (reason);
+            reason = NULL;
+        }
+
+        if (gid_errno)
+        {
+            reason = g_strdup_printf ("couldn't set gid to %s (%ld)",
+                                      (g && g->gr_name ? g->gr_name : "???"),
+                                      (long) gid);
+            if (gid_errno == -1)
+                fprintf (stderr, "%s: unknown error\n", reason);
+            else
+            {
+                errno = gid_errno;
+                perror (reason);
+            }
+            g_free (reason);
+            reason = NULL;
+        }
+
+        if (uid_errno)
+        {
+            reason = g_strdup_printf ("couldn't set uid to %s (%ld)",
+                                      (p && p->pw_name ? p->pw_name : "???"),
+                                      (long) uid);
+            if (uid_errno == -1)
+                fprintf (stderr, "%s: unknown error\n", reason);
+            else
+            {
+                errno = uid_errno;
+                perror (reason);
+            }
+            g_free (reason);
+            reason = NULL;
+        }
+        return FALSE;
+    }
+    return FALSE;
+}
+
+
+/* If we've been run as setuid or setgid to someone else (most likely root)
+   turn off the extra permissions so that random user-specified programs
+   don't get special privileges.  (On some systems it is necessary to install
+   this program as setuid root in order to read the passwd file to implement
+   lock-mode.)
+
+   *** WARNING: DO NOT DISABLE ANY OF THE FOLLOWING CODE!
+   If you do so, you will open a security hole.  See the sections
+   of the xscreensaver manual titled "LOCKING AND ROOT LOGINS",
+   and "USING XDM".
+*/
+
+/* Returns TRUE if OK to lock, FALSE otherwise */
+gboolean
+hack_uid (char **nolock_reason,
+          char **orig_uid,
+          char **uid_message)
+{
+    char    *reason;
+    gboolean ret;
+
+    ret = TRUE;
+    reason = NULL;
+
+    if (nolock_reason != NULL)
+    {
+        *nolock_reason = NULL;
+    }
+    if (orig_uid != NULL)
+    {
+        *orig_uid = NULL;
+    }
+    if (uid_message != NULL)
+    {
+        *uid_message = NULL;
+    }
+
+    /* Discard privileges, and set the effective user/group ids to the
+       real user/group ids.  That is, give up our "chmod +s" rights.
+    */
+    {
+        uid_t euid = geteuid ();
+        gid_t egid = getegid ();
+        uid_t uid  = getuid ();
+        gid_t gid  = getgid ();
+
+        if (orig_uid != NULL)
+        {
+            *orig_uid = uid_gid_string (euid, egid);
+        }
+
+        if (uid != euid || gid != egid)
+        {
+            if (! set_ids_by_number (uid, gid, uid_message))
+            {
+                reason = g_strdup ("unable to discard privileges.");
+
+                ret = FALSE;
+                goto out;
+            }
+        }
+    }
+
+
+    /* Locking can't work when running as root, because we have no way of
+       knowing what the user id of the logged in user is (so we don't know
+       whose password to prompt for.)
+
+       *** WARNING: DO NOT DISABLE THIS CODE!
+       If you do so, you will open a security hole.  See the sections
+       of the xscreensaver manual titled "LOCKING AND ROOT LOGINS",
+       and "USING XDM".
+    */
+    if (getuid () == (uid_t) 0)
+    {
+        reason = g_strdup ("running as root");
+        ret = FALSE;
+        goto out;
+    }
+
+out:
+    if (nolock_reason != NULL)
+    {
+        *nolock_reason = g_strdup (reason);
+    }
+    g_free (reason);
+
+    return ret;
+}