nixos/ssh: Remove support for old host keys

nixos/modules/services/networking/ssh/sshd.nix

@@ -54,8 +54,6 @@ let
     ));
   in listToAttrs (map mkAuthKeyFile usersWithKeys);
 
-  supportOldHostKeys = !versionAtLeast config.system.stateVersion "15.07";
-
 in
 
 {
@@ -191,9 +189,6 @@ in
         default =
           [ { type = "rsa"; bits = 4096; path = "/etc/ssh/ssh_host_rsa_key"; }
             { type = "ed25519"; path = "/etc/ssh/ssh_host_ed25519_key"; }
-          ] ++ optionals supportOldHostKeys
-          [ { type = "dsa"; path = "/etc/ssh/ssh_host_dsa_key"; }
-            { type = "ecdsa"; bits = 521; path = "/etc/ssh/ssh_host_ecdsa_key"; }
           ];
         description = ''
           NixOS can automatically generate SSH host keys.  This option
@@ -363,14 +358,6 @@ in
           HostKey ${k.path}
         '')}
 
-        # Allow DSA client keys for now. (These were deprecated
-        # in OpenSSH 7.0.)
-        PubkeyAcceptedKeyTypes +ssh-dss
-
-        # Re-enable DSA host keys for now.
-        ${optionalString supportOldHostKeys ''
-          HostKeyAlgorithms +ssh-dss
-        ''}
       '';
 
     assertions = [{ assertion = if cfg.forwardX11 then cfgc.setXAuthLocation else true;