From 6b1386d10566307ea1fe87c0ec73def57fcc8d1d Mon Sep 17 00:00:00 2001
From: Jan Smutny <js@excello.cz>
Date: Thu, 30 Mar 2023 11:16:53 +0200
Subject: [PATCH] arc.lua: fix signature of ARC-Seal header

The ARC Set header field values must be supplied to the hash function in increasing
instance order, starting at 1.
Defined in https://www.rfc-editor.org/rfc/rfc8617.html#section-5.1.1.
---
 src/plugins/lua/arc.lua | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/plugins/lua/arc.lua b/src/plugins/lua/arc.lua
index 33ae3dba2..4fdd4fe9f 100644
--- a/src/plugins/lua/arc.lua
+++ b/src/plugins/lua/arc.lua
@@ -530,7 +530,7 @@ local function arc_sign_seal(task, params, header)
   local cur_idx = 1
   if arc_seals then
     cur_idx = #arc_seals + 1
-    for i = (cur_idx - 1), 1, (-1) do
+    for i = 1, #arc_seals, 1 do
       if arc_auth_results[i] then
         local s = dkim_canonicalize('ARC-Authentication-Results',
           arc_auth_results[i].raw_header)
-- 
2.39.5