[erlang-questions] Compiling Erlang without RC4?

Andreas Schultz <>
Wed Sep 14 10:08:59 CEST 2016


Hi Oliver,

You could try the attached patch. This just disables the rc4 support,
for a pull request, some adjustments to the test suite might be
required as well.

I don't have a OpenSSL without RC4, so this is purely guesswork!

Andreas

----- Original Message -----
> From: "Oliver Korpilla" <>
> To: "Alexander Færøy" <>
> Cc: "erlang-questions" <>
> Sent: Tuesday, September 13, 2016 11:03:03 PM
> Subject: Re: [erlang-questions] Compiling Erlang without RC4?

> Hello, Alexander.
> 
> You misunderstand... I'm not concerned at all. The Linux distribution I have to
> work with removed the rc4.h header and without it I can not compile the Erlang
> runtime environment (and not deploy my application).
> 
> I did a cursory look but it is as you say - I found no guards and there were
> plenty of references towards definitions from that header, so I was a bit out
> on a limb to ask if anything knew a trick to compile the Erlang runtime without
> this header...
> 
> Thanks,
> Oliver
> 
> 
> 
> Gesendet: Dienstag, 13. September 2016 um 20:42 Uhr
> Von: "Alexander Færøy" <>
> An: erlang-questions <>
> Betreff: Re: [erlang-questions] Compiling Erlang without RC4?
> On 13 September 2016 at 17:16, Oliver Korpilla <> wrote:
>> We currently have to work with a system where somebody thought removing rc4.h
>> would solve the security issues involved with this weak algorithm...
>>
>> Is there any way to build Erlang without RC4 (but still with crypto
>> functionality)?
> 
> It doesn't look like the RC4 functionality is hidden behind a guard in
> the C source code, but I don't think you should be overly worried
> about using an Erlang release that contains RC4 support.
> 
> If you take a look at the ciphers that the SSL application will use by
> default, you will see that there's no RC4 ciphers included (at least
> not in my OTP-18 installation locally):
> 
> lists:foreach(fun (Suite) -> io:format("~p~n", [Suite]) end,
> ssl:cipher_suites()).
> 
> You could consider filtering out the 3DES ciphers that are enabled by
> default though[1] using the {ciphers, [...]} option for SSL
> connections.
> 
> Cheers,
> Alex.
> 
> [1]: https://sweet32.info
> 
> 
> --
> Alexander Færøy
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