Ignore encrypted keys in config by default when no passphrase is given

This commit changes the default of the ignore_encrypted option to be
True when keys are being loaded from config files, automatically
ignoring encrypted keys when no passphrase is specified. For keys
set via client_keys, the default is to still give an error in this
case unless ignore_encrypted is explicitly set.

When loading keys from their default locations, encrypted keys were
already ignored when no passphrase is given, and this behavior isn't
changing.

asyncssh/connection.py

@@ -6491,9 +6491,9 @@ class SSHClientConnectionOptions(SSHConnectionOptions):
            are already loaded, this argument is ignored.
        :param ignore_encrypted: (optional)
            Whether or not to ignore encrypted keys when no passphrase is
-           provided. This is intended to allow encrypted keys specified via
-           the IdentityFile config option to be ignored if a passphrase
-           is not specified, loading only unencrypted local keys. Note
+           specified. This defaults to `True` for keys specified via
+           the IdentityFile config option, causing encrypted keys in the
+           config to be ignored when no passphrase is specified. Note
            that encrypted keys loaded into an SSH agent can still be used
            when this option is set.
        :param host_based_auth: (optional)
@@ -6870,7 +6870,7 @@ def prepare(self, last_config: Optional[SSHConfig] = None, # type: ignore
                 client_keys: _ClientKeysArg = (),
                 client_certs: Sequence[FilePath] = (),
                 passphrase: Optional[BytesOrStr] = None,
-                ignore_encrypted: bool = False,
+                ignore_encrypted: DefTuple[bool] = (),
                 gss_host: DefTuple[Optional[str]] = (),
                 gss_kex: DefTuple[bool] = (), gss_auth: DefTuple[bool] = (),
                 gss_delegate_creds: DefTuple[bool] = (),
@@ -7038,6 +7038,11 @@ def prepare(self, last_config: Optional[SSHConfig] = None, # type: ignore
 
         pkcs11_provider: Optional[FilePath]
 
+        if ignore_encrypted == ():
+            ignore_encrypted = client_keys == ()
+
+        ignore_encrypted: bool
+
         if client_keys == ():
             client_keys = cast(_ClientKeysArg, config.get('IdentityFile', ()))
 

tests/test_connection.py

@@ -408,6 +408,26 @@ async def test_connect_sock(self):
         async with asyncssh.connect(sock=sock):
             pass
 
+    @asynctest
+    async def test_connect_encrypted_key(self):
+        """Test connecting with encrytped client key and no passphrase"""
+
+        async with self.connect(client_keys='ckey_encrypted',
+                                ignore_encrypted=True):
+            pass
+
+        with self.assertRaises(asyncssh.KeyImportError):
+            await self.connect(client_keys='ckey_encrypted')
+
+        with open('config', 'w') as f:
+            f.write('IdentityFile ckey_encrypted')
+
+        async with self.connect(config='config'):
+            pass
+
+        with self.assertRaises(asyncssh.KeyImportError):
+            await self.connect(config='config', ignore_encrypted=False)
+
     @asynctest
     async def test_connect_invalid_options_type(self):
         """Test connecting using options using incorrect type of options"""