From ad36a88b58202c9a4a899b7ffd51b4a9cb54c0ac Mon Sep 17 00:00:00 2001
From: Vsevolod Stakhov <vsevolod@highsecure.ru>
Date: Fri, 5 Aug 2016 16:05:54 +0100
Subject: [PATCH] [Feature] Properly implement R_WHITE_ON_WHITE rule

---
 conf/metrics.conf |  6 +-----
 rules/html.lua    | 47 +++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 48 insertions(+), 5 deletions(-)

diff --git a/conf/metrics.conf b/conf/metrics.conf
index ce20753c7..407f1c3ba 100644
--- a/conf/metrics.conf
+++ b/conf/metrics.conf
@@ -157,10 +157,6 @@ metric {
             weight = 3.0;
             description = "Detects bad content-transfer-encoding for text parts";
         }
-        symbol "R_FLASH_REDIR_IMGSHACK" {
-            weight = 10.0;
-            description = "Flash redirect on imageshack.us";
-        }
         symbol "INVALID_MSGID" {
             weight = 1.7;
             description = "Message id is incorrect";
@@ -365,7 +361,7 @@ metric {
 
     group "body" {
         symbol "R_WHITE_ON_WHITE" {
-            weight = 9.0;
+            weight = 6.0;
             description = "White color on white background in HTML messages";
         }
         symbol "HTML_SHORT_LINK_IMG_1" {
diff --git a/rules/html.lua b/rules/html.lua
index bab636322..955d5a42e 100644
--- a/rules/html.lua
+++ b/rules/html.lua
@@ -164,3 +164,50 @@ rspamd_config.R_SUSPICIOUS_IMAGES = {
   group = 'html',
   description = 'Message contains many suspicious messages'
 }
+
+rspamd_config.R_WHITE_ON_WHITE = {
+  callback = function(task)
+    local tp = task:get_text_parts() -- get text parts in a message
+    local ret = false
+    local diff = 0.0
+
+    for _,p in ipairs(tp) do -- iterate over text parts array using `ipairs`
+      if p:is_html() then -- if the current part is html part
+        local hc = p:get_html() -- we get HTML context
+
+        hc:foreach_tag('font', function(tag, len)
+          local bl = tag:get_extra()
+          if bl then
+            if bl['bgcolor'] and bl['color'] then
+              local color = bl['color']
+              local bgcolor = bl['bgcolor']
+              -- Should use visual approach here some day
+              local diff_r = math.abs(color[1] - bgcolor[1]) / 255.0
+              local diff_g = math.abs(color[2] - bgcolor[2]) / 255.0
+              local diff_b = math.abs(color[3] - bgcolor[3]) / 255.0
+              diff = (diff_r + diff_g + diff_b) / 3.0
+
+              if diff < 0.2 then
+                ret = true
+                return true
+              end
+            end
+          end
+
+          return false -- Continue search
+        end)
+
+      end
+    end
+
+    if ret then
+      return true,(0.2 - diff) * 5.0,tostring(diff * 100.0)
+    end
+
+    return false
+  end,
+
+  score = 6.0,
+  group = 'html',
+  description = 'Message contains low contrast text'
+}
-- 
2.39.5