Subject: dns-0x20 section 5.4

From: Paul Vixie <[email-masked]>
Date: Mon, 03 Mar 2008 01:38:44 +0000

thanks very much to wouters@nlnetlabs for this important observation+technique:

Index: dns-0x20.ms
===================================================================
RCS file: /udir/vixie/src/cvsroot/i-d/Working/dns-0x20.ms,v
retrieving revision 1.2
diff -u -r1.2 dns-0x20.ms
--- dns-0x20.ms 3 Mar 2008 01:21:30 -0000       1.2
+++ dns-0x20.ms 3 Mar 2008 01:26:16 -0000
@@ -191,6 +191,14 @@
 their operations log when a mismatch in the 0x20 bits occurs, to help measure
 global cache poisoning attempts, and to diagnose problems which may be due to
 DNS middleboxes.
+.LP
+5.4. Requestors should take care to remember the original question name, so
+that following successful verification of the 0x20-randomized question name,
+the original can be copied into the response message before the other sections
+are uncompressed.  This is because compression pointers in the answer,
+authority, and additional section often point back to the question section,
+with the ugly result of copying the 0x20-randomized bits into the cache, and
+into subsequent responses which include data from the cache.
 .\" -------------------------------
 .Sh "5 - Implementation and Measurement"
 .LP

i noted from the above diff that i had two section 5's.  further investigation
revealed a lack of a section 10.  i renumbered the second 5, and 6..9, by +1.

that URL again is <http://sa.vix.com/~vixie/dns-0x20.txt>.

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