2.3.2.1 - EC keys suppport?

Aki Tuomi aki.tuomi at dovecot.fi
Tue Jul 31 08:50:29 EEST 2018



On 31.07.2018 03:32, ѽ҉ᶬḳ℠ wrote:
>> Perhaps for whose interested - IETF RFC 7027 specifies for TLS use:
>>
>> [ brainpoolP256r1 | brainpoolP384r1 | brainpoolP512r1 ]
>>
>> And thus t1 would not work anyway. However, having tested r1 the result
>> was just the same.
>>
>> A tcpdump during the openssl test [ s_server | s_client ] then revealed
>> (TLSv1.2 Record Layer: Handshake Protocol: Client Hello) :
>>
>> Extension: supported_groups (len=10)
>>     Type: supported_groups (10)
>>     Length: 10
>>     Supported Groups List Length: 8
>>     Supported Groups (4 groups)
>>         Supported Group: x25519 (0x001d)
>>         Supported Group: secp256r1 (0x0017)
>>         Supported Group: secp521r1 (0x0019)
>>         Supported Group: secp384r1 (0x0018)
>>
>> Apparently [ brainpool ] would apparently not fit into any of those
>> groups. Perhaps a bug in OpenSSL 1.1.0h thus.
>>
>>
> Turned out not being a bug in OpenSSL after all. From the cli it works
> with no issues this way:
>
> [ openssl s_server -cert ec.cert.pem -key ec.key.pem -port 5555 -curves
> brainpoolP512r1 ]
> [ openssl s_client -connect localhost:5555 -curves brainpoolP512r1 ]
>
> I am not familiar really with the OpenSSL API and only roughly gather
> that the app (dovecot) would have to make the API call [
> SSL_CTX_set1_groups_list ]
> (https://www.openssl.org/docs/manmaster/man3/SSL_CTX_set1_groups.html)
> in order to support those curves.
>
>
Whoops.

We have a setting called `ssl_curve_list` in dovecot, and I tried using
that when I was testing. Turns out that there is a bug preventing that
setting from being used. If you are compiling yourself, you can use the
attached patch to fix this.

After applying, you can set

ssl_curve_list = brainpoolP512r1

And then you can connect again.

Aki
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