Re: [TLS] TLS 1.3 : small fragments attack

Peter Gutmann <pgut001@cs.auckland.ac.nz> Sat, 30 December 2017 05:03 UTC

From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: "tls@ietf.org" <tls@ietf.org>, Jitendra Lulla <lullajd@yahoo.com>
Thread-Topic: [TLS] TLS 1.3 : small fragments attack
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Date: Sat, 30 Dec 2017 05:03:41 +0000
Message-ID: <1514610214269.6873@cs.auckland.ac.nz>
References: <1890717233.6710973.1514584277146.ref@mail.yahoo.com>, <1890717233.6710973.1514584277146@mail.yahoo.com>
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Subject: Re: [TLS] TLS 1.3 : small fragments attack
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Jitendra Lulla <lullajd@yahoo.com> writes:

>The client can have a rogue TLS implementation with the following intentional
>changes:
>
>0. Choose CBC with AES256-SHA56 or any other heavier (in terms of processing
>power requirements) and non paralleliz'able  cipher suite.
>
>1. After the handshake, always send all the TLS records (Application Data)
>plain text fragment size which is no greater than 1 Byte.
>
>2. Always send a padding of max possible or big size (eg 256 Bytes)

Apart from (2), that looks like interactive terminal traffic over TLS.  The
large padding may also be natually sent by an implementation that's trying a
bit too hard to hide typing/traffic patterns.

Peter.

[TLS] TLS 1.3 : small fragments attack Jitendra Lulla
Re: [TLS] TLS 1.3 : small fragments attack Peter Gutmann
Re: [TLS] TLS 1.3 : small fragments attack Jitendra Lulla
Re: [TLS] TLS 1.3 : small fragments attack Peter Gutmann
Re: [TLS] TLS 1.3 : small fragments attack Viktor Dukhovni
Re: [TLS] TLS 1.3 : small fragments attack Yoav Nir