cc_keys_to_console: add option to disable key emission (#811)

Specifically:

ssh:                                                                            
  emit_keys_to_console: false

We also port the cc_keys_to_console cloud tests to the new integration
testing framework, and add a test for this new option.

LP: #1915460

4 files changed, 97 insertions, 0 deletions

diff --git a/cloudinit/config/cc_keys_to_console.py b/cloudinit/config/cc_keys_to_console.py
index 0f2be52b..646d1f67 100644
--- a/cloudinit/config/cc_keys_to_console.py
+++ b/cloudinit/config/cc_keys_to_console.py
@@ -51,6 +51,11 @@ def _get_helper_tool_path(distro):
 
 
 def handle(name, cfg, cloud, log, _args):
+    if util.is_false(cfg.get("ssh", {}).get("emit_keys_to_console", True)):
+        log.debug(("Skipping module named %s, "
+                   "logging of SSH host keys disabled"), name)
+        return
+
     helper_path = _get_helper_tool_path(cloud.distro)
     if not os.path.exists(helper_path):
         log.warning(("Unable to activate module %s,"
diff --git a/cloudinit/config/tests/test_keys_to_console.py b/cloudinit/config/tests/test_keys_to_console.py
new file mode 100644
index 00000000..4083fc54
--- /dev/null
+++ b/cloudinit/config/tests/test_keys_to_console.py
@@ -0,0 +1,34 @@
+"""Tests for cc_keys_to_console."""
+from unittest import mock
+
+import pytest
+
+from cloudinit.config import cc_keys_to_console
+
+
+class TestHandle:
+    """Tests for cloudinit.config.cc_keys_to_console.handle.
+
+    TODO: These tests only cover the emit_keys_to_console config option, they
+    should be expanded to cover the full functionality.
+    """
+
+    @mock.patch("cloudinit.config.cc_keys_to_console.util.multi_log")
+    @mock.patch("cloudinit.config.cc_keys_to_console.os.path.exists")
+    @mock.patch("cloudinit.config.cc_keys_to_console.subp.subp")
+    @pytest.mark.parametrize("cfg,subp_called", [
+        ({}, True),  # Default to emitting keys
+        ({"ssh": {}}, True),  # Default even if we have the parent key
+        ({"ssh": {"emit_keys_to_console": True}}, True),  # Explicitly enabled
+        ({"ssh": {"emit_keys_to_console": False}}, False),  # Disabled
+    ])
+    def test_emit_keys_to_console_config(
+        self, m_subp, m_path_exists, _m_multi_log, cfg, subp_called
+    ):
+        # Ensure we always find the helper
+        m_path_exists.return_value = True
+        m_subp.return_value = ("", "")
+
+        cc_keys_to_console.handle("name", cfg, mock.Mock(), mock.Mock(), ())
+
+        assert subp_called == (m_subp.call_count == 1)
diff --git a/doc/examples/cloud-config-ssh-keys.txt b/doc/examples/cloud-config-ssh-keys.txt
index aad8b683..bfe5ab44 100644
--- a/doc/examples/cloud-config-ssh-keys.txt
+++ b/doc/examples/cloud-config-ssh-keys.txt
@@ -42,3 +42,13 @@ ssh_keys:
     -----END DSA PRIVATE KEY-----
 
   dsa_public: ssh-dss AAAAB3NzaC1kc3MAAACBAM/Ycu7ulMTEvz1RLIzTbrhELJZf8Iwua6TFfQl1ubb1rHwUElOkus7xMhdVjms8AmbV1Meem7ImE69T0bszy09QAG3NImHgZVIeXBoJ/JzByku/1NcOBYilKP7oSIcLJpGUHX8IGn1GJoH7XRBwVub6Vqm4RP78C7q9IOn0hG2VAAAAFQCDEfCrnL1GGzhCPsr/uS1vbt8/wQAAAIEAjSrok/4m8mbBkVp4IwxXFdRuqJKSj8/WWxos00Ednn/ww5QibysHYULrOKJ1+54mmpMyp5CZICUQELCfCt5ScZ9GsqgmnI80Q1h3Xkwbo3kn7PzWwRwcV6muvJn4PcZ71WM+rdN/c2EorAINDTbjRo97NueM94WbiYdtjHFxn0YAAACAXmLIFSQgiAPu459rCKxT46tHJtM0QfnNiEnQLbFluefZ/yiI4DI38UzTCOXLhUA7ybmZha+D/csj15Y9/BNFuO7unzVhikCQV9DTeXX46pG4s1o23JKC/QaYWNMZ7kTRv+wWow9MhGiVdML4ZN4XnifuO5krqAybngIy66PMEoQ= smoser@localhost
+
+# By default, the fingerprints of the authorized keys for the users
+# cloud-init adds are printed to the console. Setting
+# no_ssh_fingerprints to true suppresses this output.
+no_ssh_fingerprints: false
+
+# By default, (most) ssh host keys are printed to the console. Setting
+# emit_keys_to_console to false suppresses this output.
+ssh:
+  emit_keys_to_console: false
diff --git a/tests/integration_tests/modules/test_keys_to_console.py b/tests/integration_tests/modules/test_keys_to_console.py
new file mode 100644
index 00000000..298c9e6d
--- /dev/null
+++ b/tests/integration_tests/modules/test_keys_to_console.py
@@ -0,0 +1,48 @@
+"""Integration tests for the cc_keys_to_console module.
+
+(This is ported from
+``tests/cloud_tests/testcases/modules/keys_to_console.yaml``.)"""
+import pytest
+
+BLACKLIST_USER_DATA = """\
+#cloud-config
+ssh_fp_console_blacklist: [ssh-dss, ssh-dsa, ecdsa-sha2-nistp256]
+ssh_key_console_blacklist: [ssh-dss, ssh-dsa, ecdsa-sha2-nistp256]
+"""
+
+DISABLED_USER_DATA = """\
+#cloud-config
+ssh:
+  emit_keys_to_console: false
+"""
+
+
+@pytest.mark.user_data(BLACKLIST_USER_DATA)
+class TestKeysToConsoleBlacklist:
+    """Test that the blacklist options work as expected."""
+    @pytest.mark.parametrize("key_type", ["DSA", "ECDSA"])
+    def test_excluded_keys(self, class_client, key_type):
+        syslog = class_client.read_from_file("/var/log/syslog")
+        assert "({})".format(key_type) not in syslog
+
+    @pytest.mark.parametrize("key_type", ["ED25519", "RSA"])
+    def test_included_keys(self, class_client, key_type):
+        syslog = class_client.read_from_file("/var/log/syslog")
+        assert "({})".format(key_type) in syslog
+
+
+@pytest.mark.user_data(DISABLED_USER_DATA)
+class TestKeysToConsoleDisabled:
+    """Test that output can be fully disabled."""
+    @pytest.mark.parametrize("key_type", ["DSA", "ECDSA", "ED25519", "RSA"])
+    def test_keys_excluded(self, class_client, key_type):
+        syslog = class_client.read_from_file("/var/log/syslog")
+        assert "({})".format(key_type) not in syslog
+
+    def test_header_excluded(self, class_client):
+        syslog = class_client.read_from_file("/var/log/syslog")
+        assert "BEGIN SSH HOST KEY FINGERPRINTS" not in syslog
+
+    def test_footer_excluded(self, class_client):
+        syslog = class_client.read_from_file("/var/log/syslog")
+        assert "END SSH HOST KEY FINGERPRINTS" not in syslog