ec2: Fix maybe_perform_dhcp_discovery to use /var/tmp as a tmpdir

/run/cloud-init/tmp is on a filesystem mounted noexec, so running
dchlient in Ec2Local during discovery breaks with 'Permission denied'.
This branch allows us to run from a different tmp dir so we have exec
rights.

LP: #1717627

1 files changed, 101 insertions, 0 deletions

diff --git a/cloudinit/tests/test_temp_utils.py b/cloudinit/tests/test_temp_utils.py
new file mode 100644
index 00000000..ffbb92cd
--- /dev/null
+++ b/cloudinit/tests/test_temp_utils.py
@@ -0,0 +1,101 @@
+# This file is part of cloud-init. See LICENSE file for license information.
+
+"""Tests for cloudinit.temp_utils"""
+
+from cloudinit.temp_utils import mkdtemp, mkstemp
+from cloudinit.tests.helpers import CiTestCase, wrap_and_call
+
+
+class TestTempUtils(CiTestCase):
+
+    def test_mkdtemp_default_non_root(self):
+        """mkdtemp creates a dir under /tmp for the unprivileged."""
+        calls = []
+
+        def fake_mkdtemp(*args, **kwargs):
+            calls.append(kwargs)
+            return '/fake/return/path'
+
+        retval = wrap_and_call(
+            'cloudinit.temp_utils',
+            {'os.getuid': 1000,
+             'tempfile.mkdtemp': {'side_effect': fake_mkdtemp},
+             '_TMPDIR': {'new': None},
+             'os.path.isdir': True},
+            mkdtemp)
+        self.assertEqual('/fake/return/path', retval)
+        self.assertEqual([{'dir': '/tmp'}], calls)
+
+    def test_mkdtemp_default_non_root_needs_exe(self):
+        """mkdtemp creates a dir under /var/tmp/cloud-init when needs_exe."""
+        calls = []
+
+        def fake_mkdtemp(*args, **kwargs):
+            calls.append(kwargs)
+            return '/fake/return/path'
+
+        retval = wrap_and_call(
+            'cloudinit.temp_utils',
+            {'os.getuid': 1000,
+             'tempfile.mkdtemp': {'side_effect': fake_mkdtemp},
+             '_TMPDIR': {'new': None},
+             'os.path.isdir': True},
+            mkdtemp, needs_exe=True)
+        self.assertEqual('/fake/return/path', retval)
+        self.assertEqual([{'dir': '/var/tmp/cloud-init'}], calls)
+
+    def test_mkdtemp_default_root(self):
+        """mkdtemp creates a dir under /run/cloud-init for the privileged."""
+        calls = []
+
+        def fake_mkdtemp(*args, **kwargs):
+            calls.append(kwargs)
+            return '/fake/return/path'
+
+        retval = wrap_and_call(
+            'cloudinit.temp_utils',
+            {'os.getuid': 0,
+             'tempfile.mkdtemp': {'side_effect': fake_mkdtemp},
+             '_TMPDIR': {'new': None},
+             'os.path.isdir': True},
+            mkdtemp)
+        self.assertEqual('/fake/return/path', retval)
+        self.assertEqual([{'dir': '/run/cloud-init/tmp'}], calls)
+
+    def test_mkstemp_default_non_root(self):
+        """mkstemp creates secure tempfile under /tmp for the unprivileged."""
+        calls = []
+
+        def fake_mkstemp(*args, **kwargs):
+            calls.append(kwargs)
+            return '/fake/return/path'
+
+        retval = wrap_and_call(
+            'cloudinit.temp_utils',
+            {'os.getuid': 1000,
+             'tempfile.mkstemp': {'side_effect': fake_mkstemp},
+             '_TMPDIR': {'new': None},
+             'os.path.isdir': True},
+            mkstemp)
+        self.assertEqual('/fake/return/path', retval)
+        self.assertEqual([{'dir': '/tmp'}], calls)
+
+    def test_mkstemp_default_root(self):
+        """mkstemp creates a secure tempfile in /run/cloud-init for root."""
+        calls = []
+
+        def fake_mkstemp(*args, **kwargs):
+            calls.append(kwargs)
+            return '/fake/return/path'
+
+        retval = wrap_and_call(
+            'cloudinit.temp_utils',
+            {'os.getuid': 0,
+             'tempfile.mkstemp': {'side_effect': fake_mkstemp},
+             '_TMPDIR': {'new': None},
+             'os.path.isdir': True},
+            mkstemp)
+        self.assertEqual('/fake/return/path', retval)
+        self.assertEqual([{'dir': '/run/cloud-init/tmp'}], calls)
+
+# vi: ts=4 expandtab