From f43937f0b462734eb9c76700491c18fe4133c8e1 Mon Sep 17 00:00:00 2001
From: Brett Holman <brett.holman@canonical.com>
Date: Mon, 7 Jul 2025 10:19:50 +0800
Subject: [PATCH] fix: Don't attempt to identify non-x86 OpenStack instances
This causes cloud-init to attempt to reach out to the OpenStack Nova
datasource in non-Nova deployments on non-x86 architectures.
Change default policy of ds-identify to disallow discovery of datasources
without strict identifiable artifacts in either kernel cmdline, DMI
platform information or system configuration files. This prevents
cloud-init from attempting to reach out to well-known hard-codded link-local
IP addresses for configuration information unless the platform strictly
identifies as a specific datasource.
CVE-2024-6174
LP: #2069607
BREAKING_CHANGE: This may break non-x86 OpenStack Nova users. Affected users
may wish to use ConfigDrive as a workaround.
doc/rtd/reference/breaking_changes.rst | 49 ++++++++++++++++++++++++++
tests/unittests/test_ds_identify.py | 13 ++++---
tools/ds-identify | 8 ++---
3 files changed, 59 insertions(+), 11 deletions(-)
@@ -11,6 +11,54 @@ releases.
many operating system vendors patch out breaking changes in
cloud-init to ensure consistent behavior on their platform.
+25.1.3
+======
+
+Strict datasource identity before network
+-----------------------------------------
+Affects detection of Ec2, OpenStack or AltCloud datasources for non-x86
+architectures where DMI may not be accessible.Expand commentComment on line R20Code has comments. Press enter to view.
+
+Datasource detection provided by ds-identify in cloud-init now requires strict
+identification based on DMI platform information, kernel command line or
+`datasource_list:` system configuration in /etc/cloud/cloud.cfg.d.
+
+Prior to this change, ds-identify would allow non-x86 architectures without
+strict identifying platform information to run in a discovery mode which would
+attempt to reach out to well known static link-local IPs to attempt to
+retrieve configuration once system networking is up.
+
+To mitigate the potential of a bad-actor in a local network responding
+to such provisioning requests from cloud-init clients, ds-identify will no
+longer allow this late discovery mode for platforms unable to expose clear
+identifying characteristics of a known cloud-init datasource.
+
+The most likely affected cloud platforms are AltCloud, Ec2 and OpenStack for
+non-x86 architectures where DMI data is not exposed by the kernel.
+
+If your non-x86 architecture or images no longer detect the proper datasource,
+any of the following steps can ensure proper detection of cloud-init config:
+
+- Provide kernel commandline containing ``ds=<lowercase_datasource_name>``
+ which forces ds-identify to discover a specific datasource.
+- Image creators: provide a config file part such as
+ :file:`/etc/cloud/cloud.cfg.d/*.cfg` containing the
+ case-sensitive ``datasource_list: [ <datasource_name> ]`` to force cloud-init
+ to use a specific datasource without performing discovery.
+
+For example, to force OpenStack discovery in cloud-init any of the following
+approaches work:
+
+- OpenStack: `attach a ConfigDrive`_ as an alternative config source
+- Kernel command line containing ``ds=openstack``
+- Custom images provide :file:`/etc/cloud/cloud.cfg.d/91-set-datasource.cfg`
+ containing:
+
+.. code-block:: yaml
+
+ datasource_list: [ OpenStack ]
+
+
25.1
@@ -162,5 +210,6 @@ Workarounds include updating the kernel command line and optionally configuring
a ``datasource_list`` in ``/etc/cloud/cloud.cfg.d/*.cfg``.
+.. _attach a ConfigDrive: https://docs.openstack.org/nova/2024.1/admin/config-drive.html
.. _this patch: https://github.com/canonical/cloud-init/blob/ubuntu/noble/debian/patches/no-single-process.patch
.. _Python3 equivalent: https://github.com/canonical/cloud-init/pull/5489#issuecomment-2408210561
@@ -208,9 +208,9 @@ system_info:
"""
POLICY_FOUND_ONLY = "search,found=all,maybe=none,notfound=disabled"
-POLICY_FOUND_OR_MAYBE = "search,found=all,maybe=all,notfound=disabled"
-DI_DEFAULT_POLICY = "search,found=all,maybe=all,notfound=disabled"
-DI_DEFAULT_POLICY_NO_DMI = "search,found=all,maybe=all,notfound=enabled"
+POLICY_FOUND_OR_MAYBE = "search,found=all,maybe=none,notfound=disabled"
+DI_DEFAULT_POLICY = "search,found=all,maybe=none,notfound=disabled"
+DI_DEFAULT_POLICY_NO_DMI = "search,found=all,maybe=none,notfound=enabled"
DI_EC2_STRICT_ID_DEFAULT = "true"
OVF_MATCH_STRING = "http://schemas.dmtf.org/ovf/environment/1"
@@ -947,7 +947,7 @@ class TestDsIdentify(DsIdentifyBase):
self._test_ds_found("OpenStack-AssetTag-Compute")
def test_openstack_on_non_intel_is_maybe(self):
- """On non-Intel, openstack without dmi info is maybe.
+ """On non-Intel, openstack without dmi info is none.
nova does not identify itself on platforms other than intel.
https://bugs.launchpad.net/cloud-init/+bugs?field.tag=dsid-nova"""
@@ -967,10 +967,9 @@ class TestDsIdentify(DsIdentifyBase):
# updating the uname to ppc64 though should get a maybe.
data.update({"mocks": [MOCK_VIRT_IS_KVM, MOCK_UNAME_IS_PPC64]})
- (_, _, err, _, _) = self._check_via_dict(
- data, RC_FOUND, dslist=["OpenStack", "None"]
- )
+ (_, _, err, _, _) = self._check_via_dict(data, RC_NOT_FOUND)
self.assertIn("check for 'OpenStack' returned maybe", err)
+ self.assertIn("No ds found", err)
def test_default_ovf_is_found(self):
"""OVF is identified found when ovf/ovf-env.xml seed file exists."""
@@ -14,7 +14,7 @@
# The format is:
# <mode>,found=value,maybe=value,notfound=value
# default setting is:
-# search,found=all,maybe=all,notfound=disabled
+# search,found=all,maybe=none,notfound=disabled
#
# kernel command line option: ci.di.policy=<policy>
# example line in /etc/cloud/ds-identify.cfg:
@@ -40,7 +40,7 @@
# first: use the first found do no further checking
# all: enable all DS_FOUND
#
-# maybe: (default=all)
+# maybe: (default=none)
# if nothing returned 'found', then how to handle maybe.
# no network sources are allowed to return 'maybe'.
# all: enable all DS_MAYBE
@@ -100,8 +100,8 @@ DI_MAIN=${DI_MAIN:-main}
DI_BLKID_EXPORT_OUT=""
DI_GEOM_LABEL_STATUS_OUT=""
-DI_DEFAULT_POLICY="search,found=all,maybe=all,notfound=${DI_DISABLED}"
-DI_DEFAULT_POLICY_NO_DMI="search,found=all,maybe=all,notfound=${DI_ENABLED}"
+DI_DEFAULT_POLICY="search,found=all,maybe=none,notfound=${DI_DISABLED}"
+DI_DEFAULT_POLICY_NO_DMI="search,found=all,maybe=none,notfound=${DI_ENABLED}"
DI_DMI_BOARD_NAME=""
DI_DMI_CHASSIS_ASSET_TAG=""
DI_DMI_PRODUCT_NAME=""
--
2.43.0