ssh: Skip sshd_simple_exec when user identity key is missing

Add init_per_testcase guard that skips when the required
private key file does not exist, avoiding slow auth failures.

Generate ed25519 and ecdsa user keys in the GHA Docker image
so all public_key groups authenticate against the OS sshd.

Author: u3s

.github/dockerfiles/Dockerfile.ubuntu-base

@@ -129,7 +129,9 @@ USER ${USER}
 ## Need to set USER and create a keygen file for ssh tests to pass
 ENV USER=${USER}
 RUN ssh-keygen -q -t rsa -N '' -f $HOME/.ssh/id_rsa && \
-    cp $HOME/.ssh/id_rsa.pub $HOME/.ssh/authorized_keys
+    ssh-keygen -q -t ed25519 -N '' -f $HOME/.ssh/id_ed25519 && \
+    ssh-keygen -q -t ecdsa -b 256 -N '' -f $HOME/.ssh/id_ecdsa && \
+    cat $HOME/.ssh/id_rsa.pub $HOME/.ssh/id_ed25519.pub $HOME/.ssh/id_ecdsa.pub > $HOME/.ssh/authorized_keys
 
 COPY --chown=${USER}:${GROUP} dockerfiles/.profile /home/otptest/.profile
 

lib/ssh/test/ssh_algorithms_SUITE.erl

@@ -235,6 +235,25 @@ init_per_testcase(mlkem768x25519_hybrid_secret_encoding, Config) ->
         false -> {skip, "X25519 or ML-KEM768 not supported"};
         true -> Config
     end;
+init_per_testcase(sshd_simple_exec, Config) ->
+    case proplists:get_value(tag_alg, Config) of
+        {public_key, Algs} ->
+            KeyInfo = user_key_files_for(Algs),
+            case has_user_key_for(Algs) of
+                true ->
+                    ?CT_LOG("sshd_simple_exec: identity key check passed~n"
+                            "  Algs: ~p~n"
+                            "  Key files found: ~p", [Algs, KeyInfo]),
+                    Config;
+                false ->
+                    ?CT_LOG("sshd_simple_exec: no identity key~n"
+                            "  Algs: ~p~n"
+                            "  Key files checked: ~p", [Algs, KeyInfo]),
+                    {skip, {no_user_identity_key, Algs}}
+            end;
+        _ ->
+            Config
+    end;
 init_per_testcase(_TC, Config) ->
     Config.
 
@@ -504,6 +523,46 @@ supports(Tag, Alg, Algos) ->
 	      split(Tag, Alg)).
 
 
+%%%----------------------------------------------------------------
+%%% Check that the user has a local identity key matching the algorithm.
+%%% Used by init_per_testcase(sshd_simple_exec, ...) to skip early
+%%% instead of waiting 37s+ for auth failure against the OS sshd.
+
+has_user_key_for(Algs) when is_list(Algs) ->
+    lists:all(fun has_user_key_for_single/1, Algs);
+has_user_key_for(Alg) ->
+    has_user_key_for_single(Alg).
+
+user_key_files_for(Algs) when is_list(Algs) ->
+    lists:flatmap(fun user_key_files_for/1, Algs);
+user_key_files_for(Alg) ->
+    Home = os:getenv("HOME"),
+    KeyFiles = key_filenames(Alg),
+    [{Alg, F, filelib:is_regular(filename:join([Home, ".ssh", F]))}
+     || F <- KeyFiles].
+
+has_user_key_for_single(Alg) ->
+    case ssh_file:user_key(Alg, []) of
+        {ok, _Key} -> true;
+        _ -> false
+    end.
+
+key_filenames(Alg) ->
+    case Alg of
+        'ssh-rsa'             -> ["id_rsa"];
+        'rsa-sha2-256'        -> ["id_rsa"];
+        'rsa-sha2-512'        -> ["id_rsa"];
+        'ssh-dss'             -> ["id_dsa"];
+        'ssh-ed25519'         -> ["id_ed25519"];
+        'ssh-ed448'           -> ["id_ed448"];
+        'ecdsa-sha2-nistp256' -> ["id_ecdsa", "id_ecdsa_sk"];
+        'ecdsa-sha2-nistp384' -> ["id_ecdsa"];
+        'ecdsa-sha2-nistp521' -> ["id_ecdsa"];
+        _                     -> []
+    end.
+
+%%%----------------------------------------------------------------
+
 extract_algos(Spec) ->
     [{Tag,get_atoms(List)} || {Tag,List} <- Spec].