TJ Saunders

Thank you. From the `config.log`, we can see that the attempt to detect `crypt()` support failed: ``` configure:21176: checking for standalone crypt configure:21202: gcc -o conftest.exe -g2 -O2 -Wall -fno-omit-frame-pointer...

Unfortunately not. I don't develop on, or use, Cygwin/Windows, so I'm not sure what I can do to help here.

Could you provide your `proftpd.conf`, and the [ProFTPD debug logging](http://www.proftpd.org/docs/howto/Debugging.html), so that I can try to reproduce this behavior locally?

I think I see what the issue might be. To help confirm -- if you disable the use of `mod_vroot` temporarily, _e.g._: ``` VRootEngine off ``` then does it work...

> The help needs to be updated with the new params. It's one of the "fun" parts of documenting someone else's (OpenSSL's) interfaces -- they can and will change (across...

Another approach might be to implement yet another `SFTPClientMatch` key, one that allows specifying the minimum allowed DH size, based on the client banner. Having per-client `SFTPDHParamFile` settings might be...

Fair enough. I appreciate you doing this research! I'll probably still add a little logging around, per your suggestion, for future work in this area.

I suppose we could make the DH group selection _slightly_ better by choosing from the "larger than preferred size" DH group list _first_ (see [here](https://github.com/proftpd/proftpd/blob/master/contrib/mod_sftp/kex.c#L3355)), _then_ choosing from the "preferred...

> Fair enough. I appreciate you doing this research! I'll probably still add a little logging around, per your suggestion, for future work in this area. Note that there _is_...

Rather than having multiple new directives for setting server-side policy for DH group sizes, what if we have just one, that looks something like this: ``` SFTPDHGroupLimits min pref max...