/**
* Verify that after the fork we can successfully change to this user.
*
* @param user the username given in the daemon configuration
* @returns #TRUE if username is valid
*/
dbus_bool_t
_dbus_verify_daemon_user (const char *user)
{
DBusString u;
_dbus_string_init_const (&u, user);
return _dbus_get_user_id_and_primary_group (&u, NULL, NULL);
}
/**
* Changes the user and group the bus is running as.
*
* @param user the user to become
* @param error return location for errors
* @returns #FALSE on failure
*/
dbus_bool_t
_dbus_change_to_daemon_user (const char *user,
DBusError *error)
{
dbus_uid_t uid;
dbus_gid_t gid;
DBusString u;
_dbus_string_init_const (&u, user);
if (!_dbus_get_user_id_and_primary_group (&u, &uid, &gid))
{
dbus_set_error (error, DBUS_ERROR_FAILED,
"User '%s' does not appear to exist?",
user);
return FALSE;
}
/* setgroups() only works if we are a privileged process,
* so we don't return error on failure; the only possible
* failure is that we don't have perms to do it.
*
* not sure this is right, maybe if setuid()
* is going to work then setgroups() should also work.
*/
if (setgroups (0, NULL) < 0)
_dbus_warn ("Failed to drop supplementary groups: %s\n",
_dbus_strerror (errno));
/* Set GID first, or the setuid may remove our permission
* to change the GID
*/
if (setgid (gid) < 0)
{
dbus_set_error (error, _dbus_error_from_errno (errno),
"Failed to set GID to %lu: %s", gid,
_dbus_strerror (errno));
return FALSE;
}
if (setuid (uid) < 0)
{
dbus_set_error (error, _dbus_error_from_errno (errno),
"Failed to set UID to %lu: %s", uid,
_dbus_strerror (errno));
return FALSE;
}
return TRUE;
}
/**
* Gets user ID given username
*
* @param username the username
* @param uid return location for UID
* @returns #TRUE if username existed and we got the UID
*/
dbus_bool_t
_dbus_get_user_id (const DBusString *username,
dbus_uid_t *uid)
{
return _dbus_get_user_id_and_primary_group (username, uid, NULL);
}
/**
* Changes the user and group the bus is running as.
*
* @param user the user to become
* @param error return location for errors
* @returns #FALSE on failure
*/
dbus_bool_t
_dbus_change_to_daemon_user (const char *user,
DBusError *error)
{
dbus_uid_t uid;
dbus_gid_t gid;
DBusString u;
_dbus_string_init_const (&u, user);
if (!_dbus_get_user_id_and_primary_group (&u, &uid, &gid))
{
dbus_set_error (error, DBUS_ERROR_FAILED,
"User '%s' does not appear to exist?",
user);
return FALSE;
}
/* If we were root */
if (_dbus_geteuid () == 0)
{
int rc;
int have_audit_write;
have_audit_write = capng_have_capability (CAPNG_PERMITTED, CAP_AUDIT_WRITE);
capng_clear (CAPNG_SELECT_BOTH);
/* Only attempt to retain CAP_AUDIT_WRITE if we had it when
* starting. See:
* https://bugs.freedesktop.org/show_bug.cgi?id=49062#c9
*/
if (have_audit_write)
capng_update (CAPNG_ADD, CAPNG_EFFECTIVE | CAPNG_PERMITTED,
CAP_AUDIT_WRITE);
rc = capng_change_id (uid, gid, CAPNG_DROP_SUPP_GRP);
if (rc)
{
switch (rc) {
default:
dbus_set_error (error, DBUS_ERROR_FAILED,
"Failed to drop capabilities: %s\n",
_dbus_strerror (errno));
break;
case -4:
dbus_set_error (error, _dbus_error_from_errno (errno),
"Failed to set GID to %lu: %s", gid,
_dbus_strerror (errno));
break;
case -5:
_dbus_warn ("Failed to drop supplementary groups: %s\n",
_dbus_strerror (errno));
break;
case -6:
dbus_set_error (error, _dbus_error_from_errno (errno),
"Failed to set UID to %lu: %s", uid,
_dbus_strerror (errno));
break;
case -7:
dbus_set_error (error, _dbus_error_from_errno (errno),
"Failed to unset keep-capabilities: %s\n",
_dbus_strerror (errno));
break;
}
return FALSE;
}
}
return TRUE;
}
