[racket-dev] [patch] OpenSSL ECDH(E) + DHE support.

From: Ryan Culpepper (ryanc at ccs.neu.edu)
Date: Mon Feb 10 18:37:56 EST 2014

On 02/08/2014 05:52 PM, Edward Lee wrote:
> Hi.
> Racket's OpenSSL bindings do not currently enable the ECDH(E) and the
> DHE ciphers, which are needed for perfect forward secrecy.
> I've attached a patch that:
>    - Embeds reasonable defaults for DHE mode.
>    - Adds two functions, ssl-server-context-enable-dhe! and
>      ssl-server-context-enable-ecdhe! that when given
>      DHE/ECDHE setup arguments (for DHE, a DH parameter file path,
>      for ECDHE, the name of one of the built-in OpenSSL elliptic curves
>      [currently, only secp521r1])
>    - (unrelated, but also useful) Adds bindings for TLS 1.1/1.2-only
>      server/client contexts.
> This patch is currently a work in progress (it currently only supports
> one elliptic curve name) that works well enough for what I am using it
> for, but I'm interested in getting this patch upstream.

Here are a few comments:

What is SSL_CTRL_SET_ECDH_AUTO? I couldn't find it in the openssl 
headers, and I searched a few recent versions. It seems unused here, anyway.

I think it would be better to read the DH params file into memory using 
Racket file operations and then use a memory BIO for 
PEM_read_bio_DHparams. Two reasons: the file access will then 
automatically go through Racket's security-guard checks, and the file 
read will go through Racket's IO system, so if the read blocks it won't 
block all Racket threads.

In ...enable-ecdhe!, the 'case' form doesn't need 'quote'. It should be 
this instead:

   (case name
     [(secp521r1) NID_secp521r1]
     [else ___])

As it is, the function will accept 'quote as the name of a curve.

> What's the exact process for this?

If you have a github account, you can fork the repo there and submit a 
pull request. But we can certainly handle patches like this too.


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