From 6ebd79ec02c66e273975e48b481714768080790b Mon Sep 17 00:00:00 2001
From: Jeremy Harris <jgh146exb@wizmail.org>
Date: Mon, 19 Jan 2015 16:42:31 +0000
Subject: [PATCH] DANE: if all TLSA records are unusable, retry verification
 non-dane.

---
 src/src/tls-openssl.c     |  2 +-
 src/src/transports/smtp.c | 14 +++++++++++--
 src/src/verify.c          | 43 ++++++++++++++++++++++++++++-----------
 3 files changed, 44 insertions(+), 15 deletions(-)

diff --git a/src/src/tls-openssl.c b/src/src/tls-openssl.c
index ce6b47832..24ae3ea7e 100644
--- a/src/src/tls-openssl.c
+++ b/src/src/tls-openssl.c
@@ -1764,7 +1764,7 @@ if (found)
   return OK;
 
 log_write(0, LOG_MAIN, "DANE error: No usable TLSA records");
-return FAIL;
+return DEFER;
 }
 #endif	/*EXPERIMENTAL_DANE*/
 
diff --git a/src/src/transports/smtp.c b/src/src/transports/smtp.c
index 094353415..087b10cda 100644
--- a/src/src/transports/smtp.c
+++ b/src/src/transports/smtp.c
@@ -1279,6 +1279,7 @@ BOOL prdr_active;
 BOOL dsn_all_lasthop = TRUE;
 #if defined(SUPPORT_TLS) && defined(EXPERIMENTAL_DANE)
 BOOL dane = FALSE;
+BOOL dane_required;
 dns_answer tlsa_dnsa;
 #endif
 smtp_inblock inblock;
@@ -1365,8 +1366,6 @@ if (continue_hostname == NULL)
 
 #if defined(SUPPORT_TLS) && defined(EXPERIMENTAL_DANE)
     {
-    BOOL dane_required;
-
     tls_out.dane_verified = FALSE;
     tls_out.tlsa_usage = 0;
 
@@ -1605,6 +1604,17 @@ if (  tls_offered
 
     if (rc != OK)
       {
+# ifdef EXPERIMENTAL_DANE
+      if (rc == DEFER && dane && !dane_required)
+	{
+	log_write(0, LOG_MAIN, "DANE attempt failed;"
+	  " trying CA-root TLS to %s [%s] (not in hosts_require_dane)",
+	  host->name, host->address);
+	dane = FALSE;
+	goto TLS_NEGOTIATE;
+	}
+# endif
+
       save_errno = ERRNO_TLSFAILURE;
       message = US"failure while setting up TLS session";
       send_quit = FALSE;
diff --git a/src/src/verify.c b/src/src/verify.c
index bdd4b8b0a..a22bb7d5b 100644
--- a/src/src/verify.c
+++ b/src/src/verify.c
@@ -535,6 +535,7 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
     uschar *interface = NULL;  /* Outgoing interface to use; NULL => any */
 #if defined(SUPPORT_TLS) && defined(EXPERIMENTAL_DANE)
     BOOL dane = FALSE;
+    BOOL dane_required;
     dns_answer tlsa_dnsa;
 #endif
     uschar inbuffer[4096];
@@ -592,7 +593,6 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
 
 #if defined(SUPPORT_TLS) && defined(EXPERIMENTAL_DANE)
       {
-      BOOL dane_required;
       int rc;
 
       tls_out.dane_verified = FALSE;
@@ -797,6 +797,7 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
 	int oldtimeout = ob->command_timeout;
 	int rc;
 
+	tls_negotiate:
 	ob->command_timeout = callout;
         rc = tls_client_start(inblock.sock, host, addr, addr->transport
 # ifdef EXPERIMENTAL_DANE
@@ -805,26 +806,44 @@ can do it there for the non-rcpt-verify case.  For this we keep an addresscount.
 			    );
 	ob->command_timeout = oldtimeout;
 
-        /* TLS negotiation failed; give an error.  Try in clear on a new connection,
-           if the options permit it for this host. */
+        /* TLS negotiation failed; give an error.  Try in clear on a new
+	connection, if the options permit it for this host. */
         if (rc != OK)
           {
-	  if (  rc == DEFER
-	     && ob->tls_tempfail_tryclear
-	     && !smtps
-	     && verify_check_given_host(&ob->hosts_require_tls, host) != OK
-	     )
+	  if (rc == DEFER)
 	    {
 	    (void)close(inblock.sock);
 # ifdef EXPERIMENTAL_EVENT
 	    (void) event_raise(addr->transport->event_action,
 				    US"tcp:close", NULL);
 # endif
-	    log_write(0, LOG_MAIN, "TLS session failure: delivering unencrypted "
-	      "to %s [%s] (not in hosts_require_tls)", host->name, host->address);
-	    suppress_tls = TRUE;
-	    goto tls_retry_connection;
+# ifdef EXPERIMENTAL_DANE
+	    if (dane)
+	      {
+	      if (!dane_required)
+		{
+		log_write(0, LOG_MAIN, "DANE attempt failed;"
+		  " trying CA-root TLS to %s [%s] (not in hosts_require_dane)",
+		  host->name, host->address);
+		dane = FALSE;
+		goto tls_negotiate;
+		}
+	      }
+	    else
+# endif
+	      if (  ob->tls_tempfail_tryclear
+		 && !smtps
+		 && verify_check_given_host(&ob->hosts_require_tls, host) != OK
+		 )
+	      {
+	      log_write(0, LOG_MAIN, "TLS session failure:"
+		" delivering unencrypted to %s [%s] (not in hosts_require_tls)",
+		host->name, host->address);
+	      suppress_tls = TRUE;
+	      goto tls_retry_connection;
+	      }
 	    }
+
 	  /*save_errno = ERRNO_TLSFAILURE;*/
 	  /*message = US"failure while setting up TLS session";*/
 	  send_quit = FALSE;
-- 
2.25.1