Is SSL and Compression never secure in nginx?

Hi,

I am working in a project where a password-protected extranet
application
is behind an nginx proxy using ssl.

Now I asked the admin to enable server-side http-compression because we
tend to have rather lengthy json responses from our REST api and they
compress very well and the performance gain would be significant. He
decline doing that, explaining that because of the CRIME vulnerability,
it
is not a good idea to enable compression when using ssl with nginx. Is
this
really always the case? Are there scenarios where the vulnerability is
not
a problem? I am trying to understand this better to make an informed
decision because not using compression (encryption is a must) would
incur
other costs (optimizations in the code) and I don’t just want to waste
that
time and money unless I have to.

Thanks in advance,

Robert

Hello!

On Mon, Jul 27, 2015 at 05:24:21PM +0200, Robert Krüger wrote:

really always the case? Are there scenarios where the vulnerability is not
a problem? I am trying to understand this better to make an informed
decision because not using compression (encryption is a must) would incur
other costs (optimizations in the code) and I don’t just want to waste that
time and money unless I have to.

The CRIME attack only applies when you are using SSL compression,
which is always off in nginx.

There is a similar attack on gzip http compression, BREACH. It
only applies if you return sensitive data in a response with some
user-controlled data, and compress them together. Such attacks
usually can be more or less easily mitigated by either not
compressing sensitive responses (nginx allows to control gzip
compression on a per-location basis) or implementing some rate
limits (like limit_req).

See here for more details:

https://en.wikipedia.org/wiki/BREACH_(security_exploit)


Maxim D.
http://nginx.org/

OK, thanks a lot for the feedback. That helped. I will try to find out
if
one of the “fixes” applies to our case.

CRIME has been superseeded by BREACH, and it is in no way related to any
specific Web server, but to the more general concepts of TLS-encrypted
(gzip-?)compressed HTTP content (SPDY is fine).

On the following website you will get all the details as well as a
cheat-sheet list of ideas to mitigate it. Disabling gzip compression
when
encrypting HTTP content is one idea.
http://breachattack.com/

​The baseline is: nginx in itself has nothing to do with it.​

B. R.

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