From: Ralf Jung <post@ralfj.de>
Date: Sat, 5 Mar 2016 17:44:51 +0000 (+0100)
Subject: support splitting TXT records into bind-sized chunks
X-Git-Url: https://git.ralfj.de/zonemaker.git/commitdiff_plain/53f825fef45e8d09bd04ab44fd4a5e9e6e0c7626?ds=sidebyside;hp=a683afa38cc20da20ad379ac9af280eae01433a2

support splitting TXT records into bind-sized chunks
---

diff --git a/zone.py b/zone.py
index 7d692c1..a74ee18 100644
--- a/zone.py
+++ b/zone.py
@@ -110,6 +110,11 @@ def concatenate(root, path):
         return path
     return path+"."+root
 
+def escape_TXT(text):
+    for c in ('\\', '\"'):
+        text = text.replace(c, '\\'+c)
+    return text
+
 
 ## Enums
 class Protocol:
@@ -182,13 +187,17 @@ class TXT:
         for c in ('\n', '\r', '\t'):
             if c in text:
                 raise Exception("TXT record {0} contains invalid character")
-        # escape text
-        for c in ('\\', '\"'):
-            text = text.replace(c, '\\'+c)
         self._text = text
     
     def generate_rr(self):
-        return RR('@', 'TXT', '"{0}"'.format(self._text))
+        text = escape_TXT(self._text)
+        # split into chunks of max. 255 characters; be careful not to split right after a backslash
+        chunks = re.findall(r'.{0,254}[^\\]', text)
+        assert sum(len(c) for c in chunks) == len (text)
+        chunksep = '"\n' + ' '*20 + '"'
+        chunked = '( "' + chunksep.join(chunks) + '" )'
+        # generate the chunks
+        return RR('@', 'TXT', chunked)
 
 
 class DKIM(TXT): # helper class to treat DKIM more antively