From: Jeremy Harris <jgh146exb@wizmail.org>
Date: Tue, 20 Mar 2018 19:58:00 +0000 (+0000)
Subject: ARC: on the smtp transport option take empty or forced-fail to disable signing
X-Git-Tag: exim-4_91_RC2~2
X-Git-Url: https://vcs.fsf.org/?p=exim.git;a=commitdiff_plain;h=587d831d9428c40f108ac91c1e061096b17a7a3e

ARC: on the smtp transport option take empty or forced-fail to disable signing
---

diff --git a/doc/doc-txt/experimental-spec.txt b/doc/doc-txt/experimental-spec.txt
index ce140c553..149598ee8 100644
--- a/doc/doc-txt/experimental-spec.txt
+++ b/doc/doc-txt/experimental-spec.txt
@@ -799,6 +799,7 @@ arc_sign = <admd-identifier> : <selector> : <privkey>
 An option on the smtp transport, which constructs and prepends to the message
 an ARC set of headers.  The textually-first Authentication-Results: header
 is used as a basis (you must have added one on entry to the ADMD).
+Expanded; if unset, empty or forced-failure then no signing is done.
 
 
 
diff --git a/src/src/transports/smtp.c b/src/src/transports/smtp.c
index c4a6c0283..23083f5d8 100644
--- a/src/src/transports/smtp.c
+++ b/src/src/transports/smtp.c
@@ -2999,15 +2999,21 @@ else
     uschar * s = sx.ob->arc_sign;
     if (s)
       {
-      if (!(sx.ob->dkim.arc_signspec = expand_string(s)))
+      if (!(sx.ob->dkim.arc_signspec = s = expand_string(s)))
 	{
-	message = US"failed to expand arc_sign";
-	sx.ok = FALSE;
-	goto SEND_FAILED;
+	if (!expand_string_forcedfail)
+	  {
+	  message = US"failed to expand arc_sign";
+	  sx.ok = FALSE;
+	  goto SEND_FAILED;
+	  }
+	}
+      else if (*s)
+	{
+	/* Ask dkim code to hash the body for ARC */
+	(void) arc_ams_setup_sign_bodyhash();
+	sx.ob->dkim.force_bodyhash = TRUE;
 	}
-      /* Ask dkim code to hash the body for ARC */
-      (void) arc_ams_setup_sign_bodyhash();
-      sx.ob->dkim.force_bodyhash = TRUE;
       }
     }
 # endif