From 6cbdbae71e184fb51c8f34983af59b1af7d6198d Mon Sep 17 00:00:00 2001
From: Maximilian Wirtz <maximilian.wirtz@checkmk.com>
Date: Thu, 9 Nov 2023 12:33:04 +0100
Subject: [PATCH] 16219 SEC Limit length of Hostname

Prior to this Werk it was possible to create Hosts with arbitrary length.
Since Checkmk stores information in files which paths contain the hostname these path could exceed the allowed length leading to various errors to an extend that rendered the usage of parts of the GUI useless.

We found this vulnerability internally.

<b>Affected Versions</b>:
* 2.2.0
* 2.1.0
* 2.0.0

<b>Vulnerability Management</b>:
We have rated the issue with a CVSS Score of 2.7 (Low) with the following CVSS vector:
<tt>CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L</tt>.
We assigned CVE-2023-23549 to this vulnerability.

<b>Changes</b>:
This Werk adds a maximum length of 253 characters for the hostname.

CMK-15105

Change-Id: I4be4745ede4220d05f4ff01d51aa6252dc9a1b57
---
 .werks/16219                         | 30 ++++++++++++++++++++++++++++
 cmk/utils/regex.py                   |  2 +-
 tests/unit/cmk/gui/test_valuespec.py | 15 ++++++++++++++
 3 files changed, 46 insertions(+), 1 deletion(-)
 create mode 100644 .werks/16219

diff --git a/.werks/16219 b/.werks/16219
new file mode 100644
index 00000000000..16e02e72514
--- /dev/null
+++ b/.werks/16219
@@ -0,0 +1,30 @@
+Title: Limit length of Hostname
+Class: security
+Compatible: compat
+Component: wato
+Date: 1699601325
+Edition: cre
+Knowledge: undoc
+Level: 1
+State: unknown
+Version: 2.1.0p37
+
+Prior to this Werk it was possible to create Hosts with arbitrary length.
+Since Checkmk stores information in files which paths contain the hostname these path could exceed the allowed length leading to various errors to an extend that rendered the usage of parts of the GUI useless.
+
+We found this vulnerability internally.
+
+<b>Affected Versions</b>:
+LI: 2.2.0
+LI: 2.1.0
+LI: 2.0.0
+
+<b>Vulnerability Management</b>:
+We have rated the issue with a CVSS Score of 2.7 (Low) with the following CVSS vector:
+<tt>CVSS:3.1/AV:N/AC:L/PR:H/UI:N/S:U/C:N/I:N/A:L</tt>.
+We assigned CVE-2023-23549 to this vulnerability.
+
+<b>Changes</b>:
+This Werk adds a maximum length of 253 characters for the hostname.
+
+
diff --git a/cmk/utils/regex.py b/cmk/utils/regex.py
index 47cc6b447e4..5ca83d1685a 100644
--- a/cmk/utils/regex.py
+++ b/cmk/utils/regex.py
@@ -14,7 +14,7 @@
 g_compiled_regexes: Dict[Tuple[Any, int], Pattern] = {}
 
 REGEX_HOST_NAME_CHARS = r"-0-9a-zA-Z_."
-REGEX_HOST_NAME = r"^[%s]+$" % REGEX_HOST_NAME_CHARS
+REGEX_HOST_NAME = f"^[{REGEX_HOST_NAME_CHARS}]{{,253}}$"
 
 REGEX_GENERIC_IDENTIFIER_CHARS = r"-0-9a-zA-Z_."
 REGEX_GENERIC_IDENTIFIER = r"^[%s]+$" % REGEX_GENERIC_IDENTIFIER_CHARS
diff --git a/tests/unit/cmk/gui/test_valuespec.py b/tests/unit/cmk/gui/test_valuespec.py
index 9470d5cd8d3..c1f497ceedb 100644
--- a/tests/unit/cmk/gui/test_valuespec.py
+++ b/tests/unit/cmk/gui/test_valuespec.py
@@ -656,3 +656,18 @@ def test_transform_value_no_match(self) -> None:
                     vs.Integer(),
                 ]
             ).transform_value("strange")
+
+
+@pytest.mark.parametrize(
+    "hostname",
+    (
+        "",  # empty
+        "../../foo",  # invalid char, path traversal
+        "a" * 255,  # too long
+    ),
+)
+def test_nvalid_hostnames_rejected(hostname: str) -> None:
+    """test that certain hostnames fail validation"""
+
+    with pytest.raises(MKUserError):
+        vs.Hostname().validate_value(hostname, "varprefix")