openssh: Enable DSA host/client keys

This applies a patch from Fedora to make HostKeyAlgorithms do the
right thing, fixing the issue described in
401782cb678d2e28c0f7f2d40c6421624f410148.

2 files changed, 15 insertions, 1 deletions

diff --git a/nixos/modules/programs/ssh.nix b/nixos/modules/programs/ssh.nix
index 2da8ff738fbc..169c6a38e75b 100644
--- a/nixos/modules/programs/ssh.nix
+++ b/nixos/modules/programs/ssh.nix
@@ -186,6 +186,9 @@ in
 
         ForwardX11 ${if cfg.forwardX11 then "yes" else "no"}
 
+        # Allow DSA keys for now. (These were deprecated in OpenSSH 7.0.)
+        PubkeyAcceptedKeyTypes +ssh-dss
+
         ${cfg.extraConfig}
       '';
 
diff --git a/nixos/modules/services/networking/ssh/sshd.nix b/nixos/modules/services/networking/ssh/sshd.nix
index 5baea4bc6aea..ba3efc8c0c2a 100644
--- a/nixos/modules/services/networking/ssh/sshd.nix
+++ b/nixos/modules/services/networking/ssh/sshd.nix
@@ -52,6 +52,8 @@ let
     ));
   in listToAttrs (map mkAuthKeyFile usersWithKeys);
 
+  supportOldHostKeys = !versionAtLeast config.system.stateVersion "15.07";
+
 in
 
 {
@@ -177,7 +179,7 @@ in
         default =
           [ { type = "rsa"; bits = 4096; path = "/etc/ssh/ssh_host_rsa_key"; }
             { type = "ed25519"; path = "/etc/ssh/ssh_host_ed25519_key"; }
-          ] ++ optionals (!versionAtLeast config.system.stateVersion "15.07")
+          ] ++ optionals supportOldHostKeys
           [ { type = "dsa"; path = "/etc/ssh/ssh_host_dsa_key"; }
             { type = "ecdsa"; bits = 521; path = "/etc/ssh/ssh_host_ecdsa_key"; }
           ];
@@ -347,6 +349,15 @@ in
         ${flip concatMapStrings cfg.hostKeys (k: ''
           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;