Clarify keystore types; improve exception message

Author: martinpaljak

src/main/java/com/hardssh/provider/SSHKeyStoreSpi.java

@@ -323,7 +323,7 @@ private void reload() throws CertificateException {
                 // Alias name: ...
                 // Creation date: null
                 // Unknown Entry Type
-                var e = new SSHProvider.KeyPairEntry(identity.getKey().getJavaKey(), priv);
+                var e = new SSHProvider.KeyPairEntry(identity.getKey(), priv);
                 entries.put(identity.getFingerprint(), e);
             } else {
                 throw new CertificateException("Unknown signer type: %s".formatted(identity));

src/main/java/com/hardssh/provider/SSHSignatureSpi.java

@@ -118,7 +118,7 @@ private SSHSignature agent_sign(byte[] dtbs, SSHAgentPrivateKey keyref) throws S
                 var p = SignResponse.fromByteBuffer(r);
                 return p.getSignature();
             } else {
-                throw new SignatureException("Could not sign: " + code);
+                throw new SignatureException("Could not sign: " + AgentMessage.name(code));
             }
         } catch (IOException e) {
             throw new SignatureException("Can not transmit sign request: " + e.getMessage(), e);

src/test/java/com/hardssh/provider/TestProviderKeyStore.java

@@ -72,7 +72,7 @@ public void testKeyStore() throws Exception {
                 var verify = Signature.getInstance("SHA256withECDSA");
                 // XXX: this should not trigger.
                 Assert.assertNotEquals(verify.getProvider().getName(), SSHProvider.NAME, "unexpected provider for native verification");
-                verify.initVerify(keypair.publicKey());
+                verify.initVerify(((SSHPublicKey) keypair.publicKey()).getJavaKey()); // FIXME: the types in entries need clarification
                 verify.update(payload);
                 Assert.assertTrue(verify.verify(result), "Native verification failed");