From: Wolfgang Breyha <wbreyha@gmx.net>
Date: Thu, 2 Jan 2020 13:27:25 +0000 (+0000)
Subject: SPF: shortcircuit SPF RR lookups.  Bug 1294
X-Git-Url: https://git.exim.org/users/jgh/exim.git/commitdiff_plain/79e5ebf9e9bb833ce004be65c04b2f8eea91c337

SPF: shortcircuit SPF RR lookups.  Bug 1294
---

diff --git a/doc/doc-txt/ChangeLog b/doc/doc-txt/ChangeLog
index e1e1e3bf0..b904aa99c 100644
--- a/doc/doc-txt/ChangeLog
+++ b/doc/doc-txt/ChangeLog
@@ -77,6 +77,12 @@ JH/17 Logging: when the deliver_time selector ise set, include the DT= field
 JH/18 Authentication: the gsasl driver not provides the $authN variables in time
       for the expansion of the server_scram_iter and server_scram_salt options.
 
+WB/01 SPF: DNS lookups for the obsolete SPF RR type done by the libspf2 library
+      are now specifically given a HOST_NOT_FOUND response without hitting the
+      system resolver.  The library goes on to do the now-standard TXT lookup.
+      Use of dnsdb lookups is not affected.
+      
+
 
 Exim version 4.93
 -----------------
diff --git a/src/src/spf.c b/src/src/spf.c
index 9b053ccf9..fd9831c43 100644
--- a/src/src/spf.c
+++ b/src/src/spf.c
@@ -72,6 +72,18 @@ int dns_rc;
 
 DEBUG(D_receive) debug_printf("SPF_dns_exim_lookup '%s'\n", domain);
 
+/* Shortcircuit SPF RR lookups by returning HOST_NOT_FOUND (shortest code path
+in libspf2).  They were obsoleted by RFC 6686/7208 years ago. see bug #1294
+*/
+
+if (rr_type == T_SPF)
+  {
+  HDEBUG(D_host_lookup) debug_printf("faking HOST_NOT_FOUND for SPF RR(99) lookup\n");
+  srr.herrno = HOST_NOT_FOUND;
+  SPF_dns_rr_dup(&spfrr, &srr);
+  return spfrr;
+  }
+
 switch (dns_rc = dns_lookup(dnsa, US domain, rr_type, NULL))
   {
   case DNS_SUCCEED:	srr.herrno = NETDB_SUCCESS;	break;