Re: how to compile out selected ciphers

Matt Caswell <[email protected]> Thu, 31 Aug 2017 15:06:51 +0100

Newsgroups	gmane.comp.encryption.openssl.devel
Message-ID	<[email protected]>


On 31/08/17 14:52, Hubert Kario wrote:
> On Thursday, 31 August 2017 11:13:13 CEST Richard Levitte wrote:
>> In message
>> <CALq8RvJrMZ=zmymQ1Z1HiHDDWwdCWMKjZL5whjGrET=Jw5asgQ@mail.gmail.com> on
>> Thu, 31 Aug 2017 11:25:16 +0530, Jayalakshmi bhat
>> <[email protected]> said:
>>
>> bhat.jayalakshmi> Hi All,
>> bhat.jayalakshmi>
>> bhat.jayalakshmi> I am trying to build openssl. As part of that I want
>> bhat.jayalakshmi> to remove some ciphers like md4, rc5 etc.
>> bhat.jayalakshmi>
>> bhat.jayalakshmi> I tried ./config no-md5, no-rc5 and ./Configure
>> bhat.jayalakshmi> no-md5, no-rc5. In both the case MD4 and RC5
>> bhat.jayalakshmi> directories are still getting compiled.
>> bhat.jayalakshmi>
>> bhat.jayalakshmi> Please can you let me know what could be going wrong.
>>
>> Your configuration line says 'no-md5', which is an attempt to remove
>> MD5, not MD4.  Your config line should be this:
>>
>>     ./config no-md4 no-rc5
>>
>> It's possible, though, that you really meant to remove MD5...
>> unfortunately, it's such an integral part of most SSL/TLS protocol
>> versions that we cannot for the moment allow it to be disabled.
>> That's the issue you're hitting.
> 
> It's not integral part of TLS 1.2 though so allowing for disabling of MD5 when 
> SSL, TLS1.0 and TLS 1.1 are disabled isn't unreasonable.
> 
> At the same time, the problem of data-at-rest remains, because while disabling 
> it for TLS is a good idea, disabling it for decryption of PKCS#12 or PKCS#8 
> (private keys), CMS or S/MIME at the same time could create issues that 
> manifest only quite a bit later.
> 

Note (as an aside) that no-md5 was removed as an option from OpenSSL
1.1.0 (and master).

Matt

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