So, endlich hat es die neuste Version (1.3.3-rc1) in den portage-tree von Gentoo geschafft. Allerdings gingen dann wieder die TLS-Verbindungen nicht. Grund des ganzen:
TLSOptions
The NoSessionReuseRequired option has been added. As of ProFTPD 1.3.3rc1, mod_tls only accepts SSL/TLS data connections that reuse the SSL session of the control connection, as a security measure. Unfortunately, there are some clients (e.g. curl) which do not reuse SSL sessions.
To relax the requirement that the SSL session from the control connection be reused for data connections, use the following in the proftpd.conf:
<IfModule mod_tls.c>
…
TLSOptions NoSessionReuseRequired
…
</IfModule>
Quelle: http://proftpd.org/docs/RELEASE_NOTES-1.3.3rc1