Add support for bwrap

This will be the minimum "batteries included" bubblwrap driver. It does
not do any MAC configuration, since these vary by system. Operators
may wish to wrap it further in a MAC wrapper driver.

Because we set bubblewrap as the default wrapper, test_playbooks tests
it. However, it lacks a negative test, so we won't know if we're not
actually containing things.

Users who don't have bubblewrap or don't wish to use it can set the
untrusted_wrapper to 'nullwrap' which will just execute things as
they're done before this change.

Change-Id: I84dd7c8cc55d2110b58609784007ffda0d135716
Story: 2000910
Task: 3540
Signed-off-by: Paul Belanger <pabelanger@redhat.com>

tests/unit/test_bubblewrap.py

@@ -0,0 +1,54 @@
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
+# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
+# License for the specific language governing permissions and limitations
+# under the License.
+
+import fixtures
+import logging
+import subprocess
+import tempfile
+import testtools
+
+from zuul.driver import bubblewrap
+from zuul.executor.server import SshAgent
+
+
+class TestBubblewrap(testtools.TestCase):
+    def setUp(self):
+        super(TestBubblewrap, self).setUp()
+        self.log_fixture = self.useFixture(
+            fixtures.FakeLogger(level=logging.DEBUG))
+        self.useFixture(fixtures.NestedTempfile())
+
+    def test_bubblewrap_wraps(self):
+        bwrap = bubblewrap.BubblewrapDriver()
+        work_dir = tempfile.mkdtemp()
+        ansible_dir = tempfile.mkdtemp()
+        ssh_agent = SshAgent()
+        self.addCleanup(ssh_agent.stop)
+        ssh_agent.start()
+        po = bwrap.getPopen(work_dir=work_dir,
+                            ansible_dir=ansible_dir,
+                            ssh_auth_sock=ssh_agent.env['SSH_AUTH_SOCK'])
+        self.assertTrue(po.passwd_r > 2)
+        self.assertTrue(po.group_r > 2)
+        self.assertTrue(work_dir in po.command)
+        self.assertTrue(ansible_dir in po.command)
+        # Now run /usr/bin/id to verify passwd/group entries made it in
+        true_proc = po(['/usr/bin/id'], stdout=subprocess.PIPE,
+                       stderr=subprocess.PIPE)
+        (output, errs) = true_proc.communicate()
+        # Make sure it printed things on stdout
+        self.assertTrue(len(output.strip()))
+        # And that it did not print things on stderr
+        self.assertEqual(0, len(errs.strip()))
+        # Make sure the _r's are closed
+        self.assertIsNone(po.passwd_r)
+        self.assertIsNone(po.group_r)