The SSL patches were downloaded from
ftp://ftp.uni-mainz.de/pub/internet/security/ssl/SSL-MZapps/netkit-telnet-0.17+ssl-0.1.diff.gz

The packages was build in the following way:

apt-get source netkit-telnet
mv netkit-telnet-0.17 netkit-telnet-ssl-0.17.13+0.1
cd netkit-telnet-ssl-0.17.13+0.1
zcat netkit-telnet-0.17+ssl-0.1.diff.gz | patch -p1
cd ..
cp -a netkit-telnet-ssl-0.17.13+0.1 netkit-telnet-ssl-0.17.13+0.1.orig