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From Rainer Jung <>
Subject Re: mod_ssl: Reading dhparams and ecparams not only from the first certificate file
Date Wed, 27 May 2015 07:33:54 GMT
Am 27.05.2015 um 08:40 schrieb Kaspar Brand:
> On 26.05.2015 10:33, Rainer Jung wrote:
>> I find it questionable. I would find it more natural to embed the params
>> in the cert files they apply to, so e.g. the DH params in the RSA cert
>> file and the EC params in the ECDH cert file and also to not require a
>> special order for the files which at the end we do not check. Since
>> missing the embedded params goes unnoticed (finding them is only a DEBUG
>> log line) it is not very user friendly.
> When I added this with r1527295, I didn't expect custom [EC]DH
> parameters in a certificate file to be the typical case for a mod_ssl
> configuration - and even in the light of Logjam, I don't think that we
> would want to recommend creating custom DH parameters for the average
> admin. As long as 2048-bit RSA keys are configured (the standard for
> certs issued by publicly-trusted CAs these days), there's nothing wrong
> with relying on the built-in DH parameters, i.e. those from RFC 3526. [1]
>> Can't we simply try to read DH and ECC params from every certificate
>> file and stop in each of the two cases when we have found some? That
>> would tighten the user unfriendlyness to the case of having multiple
>> inconsistent parameters embedded in different cert files. And even that
>> could be checked and logged as a warning.
> I don't have strong feelings on this, but am not sure if it's worth
> adding more code to address this specific case. My guess is that
> multi-cert virtual host configurations with OpenSSL < 1.0.2 are
> extremely rare, since they are prone to the
> one-intermediate-CA-cert-only issue, and with OpenSSL 1.0.2 or later,
> SSLOpenSSLConfCmd is definitely preferrable.


> As far as your observation "to embed the params in the cert files they
> apply to" is concerned, I think there might be a misunderstanding here:
> the [EC]DH parameters are orthogonal to the authentication algorithm -
> for an RSA key, both are applicable (cf. openssl ciphers -v aRSA+DHE and
> openssl ciphers -v aRSA+ECDHE).

Thanks for the correction.

>> That means if you start mixing embedded keys and separate key files,
> I would definitely discourage from doing so, and wouldn't bother with
> adding configuration code to address such cases (would introduce
> unneeded complexity). Putting the the private key into the
> SSLCertificateFile has been discouraged since the 2.0 release, actually
> - see the SSLCertificateKeyFile docs added with r93825. What is probably
> missing is a more prominent notice in the section on SSLCertificateFile.

OK I'll have a look at the docs an see whether I can improve them.

> [1] The site needs an update on this, as acknowledged by a
> team member meanwhile, see

Thanks for your helpful comments!


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