/* Copyright (c) The Exim Maintainers 2020 - 2022 */
/* Copyright (c) University of Cambridge 1995 - 2018 */
/* See the file NOTICE for conditions of use and distribution. */
+/* SPDX-License-Identifier: GPL-2.0-or-later */
/* Functions for interfacing with the DNS. */
int rc;
#ifndef STAND_ALONE
const uschar * save_domain;
+static BOOL try_again_recursion = FALSE;
#endif
/* DNS lookup failures of any kind are cached in a tree. This is mainly so that
/* Cut this out for various test programs */
#ifndef STAND_ALONE
- save_domain = deliver_domain;
- deliver_domain = string_copy(name); /* set $domain */
- rc = match_isinlist(name, CUSS &dns_again_means_nonexist, 0,
- &domainlist_anchor, NULL, MCL_DOMAIN, TRUE, NULL);
- deliver_domain = save_domain;
+ /* Permitting dns_again_means nonexist for TLSA lookups breaks the
+ doewngrade resistance of dane, so avoid for those. */
+
+ if (type == T_TLSA)
+ rc = FAIL;
+ else
+ {
+ if (try_again_recursion)
+ {
+ log_write(0, LOG_MAIN|LOG_PANIC,
+ "dns_again_means_nonexist recursion seen for %s"
+ " (assuming nonexist)", name);
+ return dns_fail_return(name, type, dns_expire_from_soa(dnsa, type),
+ DNS_NOMATCH);
+ }
+
+ try_again_recursion = TRUE;
+ save_domain = deliver_domain;
+ deliver_domain = string_copy(name); /* set $domain */
+ rc = match_isinlist(name, CUSS &dns_again_means_nonexist, 0,
+ &domainlist_anchor, NULL, MCL_DOMAIN, TRUE, NULL);
+ deliver_domain = save_domain;
+ try_again_recursion = FALSE;
+ }
+
if (rc != OK)
{
DEBUG(D_dns) debug_printf("returning DNS_AGAIN\n");
{
if (check_dns_names_pattern[0] != 0 && !regex_check_dns_names)
regex_check_dns_names =
- regex_must_compile(check_dns_names_pattern, FALSE, TRUE);
+ regex_must_compile(check_dns_names_pattern, MCS_NOFLAGS, TRUE);
}
/* vi: aw ai sw=2