[erlang-questions] POODLE 2.0 and Erlang

Andreas Schultz <>
Tue Dec 9 10:21:37 CET 2014


Hi,

The SSL POODLE attacks is back and this time it affects TLS 1.0:

   https://www.imperialviolet.org/2014/12/08/poodleagain.html

The blog entry refers to an interesting discussion on TLS WG
maillinglist:

   https://www.ietf.org/mail-archive/web/tls/current/msg14072.html

It went to check the Erlang SSL stack and it does contain this
comment:

%% For interoperability reasons we do not check the padding content in
%% SSL 3.0 and TLS 1.0 as it is not strictly required and breaks
%% interopability with for instance Google. 


In other words, Erlangs TLS 1.0 implementation is 100% RFC compliant
and still vulnerable to a POODLE attack on TLS 1.0.

For the paranoid, this is a quick fix hack to check padding
bytes on TLS 1.0:

diff --git a/lib/ssl/src/ssl_cipher.erl b/lib/ssl/src/ssl_cipher.erl
index a6e5e1b..9e23229 100644
--- a/lib/ssl/src/ssl_cipher.erl
+++ b/lib/ssl/src/ssl_cipher.erl
@@ -1638,8 +1638,7 @@ generic_stream_cipher_from_bin(T, HashSz) ->
 %% SSL 3.0 and TLS 1.0 as it is not strictly required and breaks
 %% interopability with for instance Google. 
 is_correct_padding(#generic_block_cipher{padding_length = Len,
-                                        padding = Padding}, {3, N})
-  when N == 0; N == 1 ->
+                                        padding = Padding}, {3, 0}) ->
     Len == byte_size(Padding); 
 %% Padding must be check in TLS 1.1 and after  
 is_correct_padding(#generic_block_cipher{padding_length = Len,

Andreas
-- 
-- 
Dipl. Inform.
Andreas Schultz


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