Implement a consistent realpath function in certbot.compat.filesystem (#7242)

Fixes #7115 

This PR creates a `realpath` method in `filesystem`, whose goal is to replace any call to `os.path.realpath` in Certbot. The reason is that `os.path.realpath` is broken on some versions of Python for Windows. See https://bugs.python.org/issue9949. The function created here works consistently across Linux and Windows.

As for the other forbidden functions in `os` module, our `certbot.compat.os` will raise an exception if its `path.realpath` function is invoked, and using the `os` module from Python is forbidden from the pylint check implemented in our CI.

Every call to `os.path.realpath` is corrected in `certbot` and `certbot-apache` modules.

* Forbid os.path.realpath

* Finish implementation

* Use filesystem.realpath

* Control symlink loops also for Linux

* Add a test for forbidden method

* Import a new object from os.path module

* Use same approach of wrapping than certbot.compat.os

* Correct errors

* Fix dependencies

* Make path module internal

certbot-apache/certbot_apache/configurator.py

@@ -23,6 +23,7 @@ from certbot import interfaces
 from certbot import util
 
 from certbot.achallenges import KeyAuthorizationAnnotatedChallenge  # pylint: disable=unused-import
+from certbot.compat import filesystem
 from certbot.compat import os
 from certbot.plugins import common
 from certbot.plugins.util import path_surgery
@@ -895,7 +896,7 @@ class ApacheConfigurator(common.Installer):
                 if not new_vhost:
                     continue
                 internal_path = apache_util.get_internal_aug_path(new_vhost.path)
-                realpath = os.path.realpath(new_vhost.filep)
+                realpath = filesystem.realpath(new_vhost.filep)
                 if realpath not in file_paths:
                     file_paths[realpath] = new_vhost.filep
                     internal_paths[realpath].add(internal_path)
@@ -1221,11 +1222,11 @@ class ApacheConfigurator(common.Installer):
         """
 
         if self.conf("vhost-root") and os.path.exists(self.conf("vhost-root")):
-            fp = os.path.join(os.path.realpath(self.option("vhost_root")),
+            fp = os.path.join(filesystem.realpath(self.option("vhost_root")),
                               os.path.basename(non_ssl_vh_fp))
         else:
             # Use non-ssl filepath
-            fp = os.path.realpath(non_ssl_vh_fp)
+            fp = filesystem.realpath(non_ssl_vh_fp)
 
         if fp.endswith(".conf"):
             return fp[:-(len(".conf"))] + self.option("le_vhost_ext")

certbot-apache/certbot_apache/override_debian.py

@@ -7,6 +7,7 @@ import zope.interface
 from certbot import errors
 from certbot import interfaces
 from certbot import util
+from certbot.compat import filesystem
 from certbot.compat import os
 
 from certbot_apache import apache_util
@@ -65,7 +66,7 @@ class DebianConfigurator(configurator.ApacheConfigurator):
         try:
             os.symlink(vhost.filep, enabled_path)
         except OSError as err:
-            if os.path.islink(enabled_path) and os.path.realpath(
+            if os.path.islink(enabled_path) and filesystem.realpath(
                enabled_path) == vhost.filep:
                 # Already in shape
                 vhost.enabled = True

certbot-apache/certbot_apache/tests/centos_test.py

@@ -4,6 +4,7 @@ import unittest
 import mock
 
 from certbot import errors
+from certbot.compat import filesystem
 from certbot.compat import os
 
 from certbot_apache import obj
@@ -160,7 +161,7 @@ class MultipleVhostsTestCentOS(util.ApacheTest):
         """Make sure we read the sysconfig OPTIONS variable correctly"""
         # Return nothing for the process calls
         mock_cfg.return_value = ""
-        self.config.parser.sysconfig_filep = os.path.realpath(
+        self.config.parser.sysconfig_filep = filesystem.realpath(
             os.path.join(self.config.parser.root, "../sysconfig/httpd"))
         self.config.parser.variables = {}
 

certbot-apache/certbot_apache/tests/configurator_test.py

@@ -675,8 +675,7 @@ class MultipleVhostsTest(util.ApacheTest):
     def test_make_vhost_ssl_nonexistent_vhost_path(self):
         ssl_vhost = self.config.make_vhost_ssl(self.vh_truth[1])
         self.assertEqual(os.path.dirname(ssl_vhost.filep),
-                            os.path.dirname(os.path.realpath(
-                                self.vh_truth[1].filep)))
+                         os.path.dirname(filesystem.realpath(self.vh_truth[1].filep)))
 
     def test_make_vhost_ssl(self):
         ssl_vhost = self.config.make_vhost_ssl(self.vh_truth[0])
@@ -1336,7 +1335,7 @@ class MultipleVhostsTest(util.ApacheTest):
         self.config.parser.modules.add("ssl_module")
         self.config.parser.modules.add("mod_ssl.c")
         self.config.parser.modules.add("socache_shmcb_module")
-        tmp_path = os.path.realpath(tempfile.mkdtemp("vhostroot"))
+        tmp_path = filesystem.realpath(tempfile.mkdtemp("vhostroot"))
         filesystem.chmod(tmp_path, 0o755)
         mock_p = "certbot_apache.configurator.ApacheConfigurator._get_ssl_vhost_path"
         mock_a = "certbot_apache.parser.ApacheParser.add_include"

certbot-apache/certbot_apache/tests/debian_test.py

@@ -79,9 +79,9 @@ class MultipleVhostsTestDebian(util.ApacheTest):
 
     def test_enable_site_failure(self):
         self.config.parser.root = "/tmp/nonexistent"
-        with mock.patch("os.path.isdir") as mock_dir:
+        with mock.patch("certbot.compat.os.path.isdir") as mock_dir:
             mock_dir.return_value = True
-            with mock.patch("os.path.islink") as mock_link:
+            with mock.patch("certbot.compat.os.path.islink") as mock_link:
                 mock_link.return_value = False
                 self.assertRaises(
                     errors.NotSupportedError,

certbot-apache/certbot_apache/tests/fedora_test.py

@@ -4,6 +4,7 @@ import unittest
 import mock
 
 from certbot import errors
+from certbot.compat import filesystem
 from certbot.compat import os
 
 from certbot_apache import obj
@@ -160,7 +161,7 @@ class MultipleVhostsTestFedora(util.ApacheTest):
         """Make sure we read the sysconfig OPTIONS variable correctly"""
         # Return nothing for the process calls
         mock_cfg.return_value = ""
-        self.config.parser.sysconfig_filep = os.path.realpath(
+        self.config.parser.sysconfig_filep = filesystem.realpath(
             os.path.join(self.config.parser.root, "../sysconfig/httpd"))
         self.config.parser.variables = {}
 

certbot-apache/certbot_apache/tests/gentoo_test.py

@@ -4,6 +4,7 @@ import unittest
 import mock
 
 from certbot import errors
+from certbot.compat import filesystem
 from certbot.compat import os
 
 from certbot_apache import obj
@@ -81,7 +82,7 @@ class MultipleVhostsTestGentoo(util.ApacheTest):
         """Make sure we read the Gentoo APACHE2_OPTS variable correctly"""
         defines = ['DEFAULT_VHOST', 'INFO',
                    'SSL', 'SSL_DEFAULT_VHOST', 'LANGUAGE']
-        self.config.parser.apacheconfig_filep = os.path.realpath(
+        self.config.parser.apacheconfig_filep = filesystem.realpath(
             os.path.join(self.config.parser.root, "../conf.d/apache2"))
         self.config.parser.variables = {}
         with mock.patch("certbot_apache.override_gentoo.GentooParser.update_modules"):