[lmi] DSA now disabled in OpenSSH

[Greg Chicares]

I've completely reinstalled Cygwin, and now ssh isn't working, presumably
because I've used DSA since forever, and openssh now disables it...

$ssh -V
OpenSSH_7.1p1, OpenSSL 1.0.2e 3 Dec 2015

http://www.openssh.com/legacy.html
| OpenSSH 7.0 and greater similarly disables the ssh-dss (DSA) public key 
algorithm.
| It too is weak and we recommend against its use.

http://savannah.gnu.org/maintenance/SshAccess/
| We recommend using only RSA keys, not DSA.

$ssh -v svn.sv.gnu.org
...
debug1: Trying private key: /home/XXXX/.ssh/id_rsa
debug1: Skipping ssh-dss key /home/XXXX/.ssh/id_dsa for not in 
PubkeyAcceptedKeyTypes

I tried this workaround...

$ssh -v -oHostKeyAlgorithms=+ssh-dss -oPubkeyAcceptedKeyTypes=+ssh-dss 
svn.sv.gnu.org
debug1: Next authentication method: publickey
debug1: Trying private key: /home/XXXX/.ssh/id_rsa
debug1: Offering DSA public key: /home/XXXX/.ssh/id_dsa
...
Permission denied (publickey).

...but it failed, so I created a new RSA key...

$ssh-keygen -t rsa -b 4096 -C "address@hidden"

...and registered it at savannah. It still doesn't work yet...

$ssh -v svn.sv.gnu.org
debug1: Offering RSA public key: /home/XXXX/.ssh/id_rsa
debug1: Authentications that can continue: publickey
debug1: Skipping ssh-dss key /home/XXXX/.ssh/id_dsa for not in 
PubkeyAcceptedKeyTypes
debug1: Trying private key: /home/XXXX/.ssh/id_ecdsa
debug1: Trying private key: /home/XXXX/.ssh/id_ed25519
debug1: No more authentication methods to try.
Permission denied (publickey).

...but at least now it's offered. Presumably I just have to wait an hour
until savannah's cron job picks up the new key.