From a105b587ac042ea2b129bed42cf47586b59818c6 Mon Sep 17 00:00:00 2001
From: alexzorin <alex@zorin.id.au>
Date: Fri, 16 Jul 2021 04:12:14 +1000
Subject: [PATCH] apache: fix crash when authenticating empty vhosts (#8941)

Fixes #8940.
---
 certbot-apache/certbot_apache/_internal/parser.py           | 6 +++++-
 certbot-apache/tests/parser_test.py                         | 5 +++++
 .../multiple_vhosts/apache2/sites-available/empty.conf      | 0
 .../apache2/sites-available/no-directives.conf              | 5 +++++
 certbot/CHANGELOG.md                                        | 3 ++-
 5 files changed, 17 insertions(+), 2 deletions(-)
 create mode 100644 certbot-apache/tests/testdata/debian_apache_2_4/multiple_vhosts/apache2/sites-available/empty.conf
 create mode 100644 certbot-apache/tests/testdata/debian_apache_2_4/multiple_vhosts/apache2/sites-available/no-directives.conf

diff --git a/certbot-apache/certbot_apache/_internal/parser.py b/certbot-apache/certbot_apache/_internal/parser.py
index 141991ccc..3c705e066 100644
--- a/certbot-apache/certbot_apache/_internal/parser.py
+++ b/certbot-apache/certbot_apache/_internal/parser.py
@@ -440,7 +440,11 @@ class ApacheParser:
         :type args: list or str
         """
         first_dir = aug_conf_path + "/directive[1]"
-        self.aug.insert(first_dir, "directive", True)
+        if self.aug.get(first_dir):
+            self.aug.insert(first_dir, "directive", True)
+        else:
+            self.aug.set(first_dir, "directive")
+
         self.aug.set(first_dir, dirname)
         if isinstance(args, list):
             for i, value in enumerate(args, 1):
diff --git a/certbot-apache/tests/parser_test.py b/certbot-apache/tests/parser_test.py
index 00ca23f7a..5ee64d3fd 100644
--- a/certbot-apache/tests/parser_test.py
+++ b/certbot-apache/tests/parser_test.py
@@ -105,6 +105,11 @@ class BasicParserTest(util.ParserTest):
         for i, match in enumerate(matches):
             self.assertEqual(self.parser.aug.get(match), str(i + 1))
 
+        for name in ("empty.conf", "no-directives.conf"):
+            conf = "/files" + os.path.join(self.parser.root, "sites-available", name)
+            self.parser.add_dir_beginning(conf, "AddDirectiveBeginning", "testBegin")
+            self.assertTrue(self.parser.find_dir("AddDirectiveBeginning", "testBegin", conf))
+
     def test_empty_arg(self):
         self.assertEqual(None,
                           self.parser.get_arg("/files/whatever/nonexistent"))
diff --git a/certbot-apache/tests/testdata/debian_apache_2_4/multiple_vhosts/apache2/sites-available/empty.conf b/certbot-apache/tests/testdata/debian_apache_2_4/multiple_vhosts/apache2/sites-available/empty.conf
new file mode 100644
index 000000000..e69de29bb
diff --git a/certbot-apache/tests/testdata/debian_apache_2_4/multiple_vhosts/apache2/sites-available/no-directives.conf b/certbot-apache/tests/testdata/debian_apache_2_4/multiple_vhosts/apache2/sites-available/no-directives.conf
new file mode 100644
index 000000000..e7ceab441
--- /dev/null
+++ b/certbot-apache/tests/testdata/debian_apache_2_4/multiple_vhosts/apache2/sites-available/no-directives.conf
@@ -0,0 +1,5 @@
+<VirtualHost *:80>
+  <Location />
+        Require all denied
+  </Location>
+</VirtualHost>
diff --git a/certbot/CHANGELOG.md b/certbot/CHANGELOG.md
index 865de631e..8dcc5049f 100644
--- a/certbot/CHANGELOG.md
+++ b/certbot/CHANGELOG.md
@@ -18,7 +18,8 @@ Certbot adheres to [Semantic Versioning](https://semver.org/).
 
 ### Fixed
 
-*
+* The Apache authenticator no longer crashes with "Unable to insert label"
+  when encountering a completely empty vhost. This issue affected Certbot 1.17.0.
 
 More details about these changes can be found on our GitHub repo.