Browse code

Attempt at reverting CVE-2020-1736 changes [2.10] (#71514)

* Revert atomic_move changes
* add note about mode reverts in porting guide

Signed-off-by: Rick Elrod <rick@elrod.me>

Rick Elrod authored on 2020/09/01 15:00:26
Showing 10 changed files
1 1
new file mode 100644
... ...
@@ -0,0 +1,2 @@
0
+security_fixes:
1
+  - The fix for CVE-2020-1736 has been reverted. Users are encouraged to specify a ``mode`` parameter in their file-based tasks when the files being manipulated contain sensitive data.
... ...
@@ -47,80 +47,14 @@ Deprecated
47 47
 Modules
48 48
 =======
49 49
 
50
-Change to Default File Permissions
51
-
52
-To address `CVE-2020-1736 <https://nvd.nist.gov/vuln/detail/CVE-2020-1736>`_, the default permissions for certain files created by Ansible using ``atomic_move()`` were changed from ``0o666`` to ``0o600``. The default permissions value was only used for the temporary file before it was moved into its place or newly created files. If the file existed when the new temporary file was moved into place, Ansible would use the permissions of the existing file. If there was no existing file, Ansible would retain the default file permissions, combined with the system ``umask``, of the temporary file.
53
-
54
-Most modules that call ``atomic_move()`` also call ``set_fs_attributes_if_different()`` or ``set_mode_if_different()``, which will set the permissions of the file to what is specified in the task.
55
-
56
-A new warning will be displayed when all of the following conditions are true:
57
-
58
-    - The file at the final destination, not the temporary file, does not exist
59
-    - A module supports setting ``mode`` but it was not specified for the task
60
-    - The module calls ``atomic_move()`` but does not later call ``set_fs_attributes_if_different()`` or ``set_mode_if_different()`` with a ``mode`` specified
61
-
62
-The following modules call ``atomic_move()`` but do not call ``set_fs_attributes_if_different()``  or ``set_mode_if_different()`` and do not support setting ``mode``. This means for files they create, the default permissions have changed and there is no indication:
63
-
64
-    - :ref:`ansible.builtin.known_hosts <ansible_collections.ansible.builtin.known_hosts_module>`
65
-    - :ref:`ansible.builtin.service <ansible_collections.ansible.builtin.service_module>`
66
-
67
-
68
-Code Audit
69
-~~~~~~~~~~
70
-
71
-The code was audited for modules that use ``atomic_move()`` but **do not** later call ``set_fs_attributes_if_different()`` or ``set_mode_if_different()``. Modules that provide no means for specifying the ``mode`` will not display a warning message since there is no way for the playbook author to remove the warning. The behavior of each module with regards to the default permissions of temporary files and the permissions of newly created files is explained below.
72
-
73
-known_hosts
74
-^^^^^^^^^^^
75
-
76
-The :ref:`ansible.builtin.known_hosts <ansible_collections.ansible.builtin.known_hosts_module>` module uses ``atomic_move()`` to operate on the ``known_hosts`` file specified by the ``path`` parameter in the module. It creates a temporary file using ``tempfile.NamedTemporaryFile()`` which creates a temporary file that is readable and writable only by the creating user ID.
77
-
78
-service
79
-^^^^^^^
80
-
81
-The :ref:`ansible.builtin.service <ansible_collections.ansible.builtin.service_module>` module uses ``atomic_move()`` to operate on the default rc file, which is the first found of ``/etc/rc.conf``,  ``/etc/rc.conf.local``, and ``/usr/local/etc/rc.conf``. Since these files almost always exist on the target system, they will not be created and the existing permissions of the file will be used.
82
-
83
-**The following modules were included in Ansible <= 2.9. They have moved to collections but are documented here for completeness.**
84
-
85
-authorized_key
86
-^^^^^^^^^^^^^^
87
-
88
-The :ref:`ansible.posix.authorized_key <ansible_collections.ansible.posix.authorized_key_module>` module uses ``atomic_move()`` to operate on the the ``authorized_key`` file. A temporary file is created with ``tempfile.mkstemp()`` before being moved into place. The temporary file is readable and writable only by the creating user ID. The :ref:`ansible.builtin.authorized_key <ansible_collections.ansible.posix.authorized_key_module>` module manages the permissions of the the ``.ssh`` direcotry and ``authorized_keys`` files if ``managed_dirs`` is set to ``True``, which is the default. The module sets the ``ssh`` directory owner and group to the ``uid`` and ``gid`` of the user specified in the ``user`` parameter and directory permissions to ``700``. The module sets the ``authorized_key`` file owner and group to the ``uid`` and ``gid`` of the user specified in the ``user`` parameter and file permissions to ``600``. These values cannot be controlled by module parameters.
89
-
90
-interfaces_file
91
-^^^^^^^^^^^^^^^
92
-The :ref:`community.general.interfaces_file <ansible_collections.community.general.interfaces_file_module>` module uses ``atomic_move()`` to operate on ``/etc/network/serivces`` or the ``dest`` specified by the module. A temporary file is created with ``tempfile.mkstemp()`` before being moved into place. The temporary file is readable and writable only by the creating user ID. If the file specified by ``path`` does not exist it will retain the permissions of the temporary file once moved into place.
93
-
94
-pam_limits
95
-^^^^^^^^^^
96
-
97
-The :ref:`community.general.pam_limits <ansible_collections.community.general.pam_limits_module>` module uses ``atomic_move()`` to operate on ``/etc/security/limits.conf`` or the value of ``dest``. A temporary file is created using ``tempfile.NamedTemporaryFile()``, which is only readable and writable by the creating user ID. The temporary file will inherit the permissions of the file specified by ``dest``, or it will retain the permissions that only allow the creating user ID to read and write the file.
98
-
99
-pamd
100
-^^^^
101
-
102
-The :ref:`community.general.pamd <ansible_collections.community.general.pamd_module>` module uses ``atomic_move()`` to operate on a file in ``/etc/pam.d``. The path and the file can be specified by setting the ``path`` and ``name`` parameters. A temporary file is created using ``tempfile.NamedTemporaryFile()``, which is only readable and writable by the creating user ID. The temporary file will inherit the permissions of the file located at ``[dest]/[name]``, or it will retain the permissions of the temporary file that only allow the creating user ID to read and write the file.
103
-
104
-redhat_subscription
105
-^^^^^^^^^^^^^^^^^^^
106
-
107
-The :ref:`community.general.redhat_subscription <ansible_collections.community.general.redhat_subscription_module>` module uses ``atomic_move()`` to operate on ``/etc/yum/pluginconf.d/rhnplugin.conf`` and ``/etc/yum/pluginconf.d/subscription-manager.conf``. A temporary file is created with ``tempfile.mkstemp()`` before being moved into place. The temporary file is readable and writable only by the creating user ID and the temporary file will inherit the permissions of the existing file once it is moved in to place.
108
-
109
-selinux
110
-^^^^^^^
111
-
112
-The :ref:`ansible.posix.selinux <ansible_collections.ansible.posix.selinux_module>` module uses ``atomic_move()`` to operate on ``/etc/selinux/config`` on the value specified by ``configfile``. The module will fail if ``configfile`` does not exist before any temporary data is written to disk. A temporary file is created with ``tempfile.mkstemp()`` before being moved into place. The temporary file is readable and writable only by the creating user ID. Since the file specified by ``configfile`` must exist, the temporary file will inherit the permissions of that file once it is moved in to place.
113
-
114
-sysctl
115
-^^^^^^
116
-
117
-The :ref:`ansible.posix.sysctl <ansible_collections.ansible.posix.sysctl_module>` module uses ``atomic_move()`` to operate on ``/etc/sysctl.conf`` or the value specified by ``sysctl_file``. The module will fail if ``sysctl_file`` does not exist before any temporary data is written to disk. A temporary file is created with ``tempfile.mkstemp()`` before being moved into place. The temporary file is readable and writable only by the creating user ID. Since the file specified by ``sysctl_file`` must exist, the temporary file will inherit the permissions of that file once it is moved in to place.
118
-
119 50
 .. warning::
120 51
 
121 52
 	Links on this page may not point to the most recent versions of modules. We will update them when we can.
122 53
 
54
+* Version 2.10.0 of ansible-base changed the default mode of file-based tasks to ``0o600`` when the user did not specify a ``mode`` parameter on file-based tasks. This was in response to a CVE report which we have reconsidered and no longer consider a flaw in ansible-base. As a result, the ``mode`` change has been reverted in 2.10.1, and ``mode`` will now default to ``0o666`` as in previous versions of Ansible and previous RCs of ansible-base.
55
+* If you changed any tasks to specify less restrictive permissions while using 2.10.0, those changes will be unnecessary (but will do no harm) in 2.10.1.
56
+* To avoid the issue raised in CVE-2020-1736, specify a ``mode`` parameter in all file-based tasks that accept it.
57
+
123 58
 
124 59
 Noteworthy module changes
125 60
 -------------------------
... ...
@@ -1125,9 +1125,6 @@ class AnsibleModule(object):
1125 1125
 
1126 1126
     def set_mode_if_different(self, path, mode, changed, diff=None, expand=True):
1127 1127
 
1128
-        if mode is None:
1129
-            return changed
1130
-
1131 1128
         # Remove paths so we do not warn about creating with default permissions
1132 1129
         # since we are calling this method on the path and setting the specified mode.
1133 1130
         try:
... ...
@@ -1135,6 +1132,9 @@ class AnsibleModule(object):
1135 1135
         except KeyError:
1136 1136
             pass
1137 1137
 
1138
+        if mode is None:
1139
+            return changed
1140
+
1138 1141
         b_path = to_bytes(path, errors='surrogate_or_strict')
1139 1142
         if expand:
1140 1143
             b_path = os.path.expanduser(os.path.expandvars(b_path))
... ...
@@ -59,7 +59,7 @@ PERMS_RE = re.compile(r'[^rwxXstugo]')
59 59
 
60 60
 _PERM_BITS = 0o7777          # file mode permission bits
61 61
 _EXEC_PERM_BITS = 0o0111     # execute permission bits
62
-_DEFAULT_PERM = 0o0600       # default file permission bits
62
+_DEFAULT_PERM = 0o0666       # default file permission bits
63 63
 
64 64
 
65 65
 def is_executable(path):
... ...
@@ -8,7 +8,7 @@
8 8
     test_repo_spec: "deb http://apt.postgresql.org/pub/repos/apt/ {{ ansible_distribution_release }}-pgdg main"
9 9
     test_repo_path: /etc/apt/sources.list.d/apt_postgresql_org_pub_repos_apt.list
10 10
 
11
-- import_tasks: mode_cleanup.yaml
11
+- include: mode_cleanup.yaml
12 12
 
13 13
 - name: Add GPG key to verify signatures
14 14
   apt_key:
... ...
@@ -31,7 +31,7 @@
31 31
   debug:
32 32
     var: mode_given_yaml_literal_0600
33 33
 
34
-- import_tasks: mode_cleanup.yaml
34
+- include: mode_cleanup.yaml
35 35
 
36 36
 - name: Assert mode_given_yaml_literal_0600 is correct
37 37
   assert:
... ...
@@ -52,11 +52,11 @@
52 52
   debug:
53 53
     var: no_mode_stat
54 54
 
55
-- import_tasks: mode_cleanup.yaml
55
+- include: mode_cleanup.yaml
56 56
 
57 57
 - name: Assert no_mode_stat is correct
58 58
   assert:
59
-    that: "no_mode_stat.stat.mode == '0600'"
59
+    that: "no_mode_stat.stat.mode == '0644'"
60 60
 
61 61
 - name: Mode specified as string 0600
62 62
   apt_repository:
... ...
@@ -74,7 +74,7 @@
74 74
   debug:
75 75
     var: mode_given_string_stat
76 76
 
77
-- import_tasks: mode_cleanup.yaml
77
+- include: mode_cleanup.yaml
78 78
 
79 79
 - name: Mode specified as string 600
80 80
   apt_repository:
... ...
@@ -92,7 +92,7 @@
92 92
   debug:
93 93
     var: mode_given_string_600_stat
94 94
 
95
-- import_tasks: mode_cleanup.yaml
95
+- include: mode_cleanup.yaml
96 96
 
97 97
 - name: Assert mode is correct
98 98
   assert:
... ...
@@ -114,7 +114,7 @@
114 114
   debug:
115 115
     var: mode_given_yaml_literal_600
116 116
 
117
-- import_tasks: mode_cleanup.yaml
117
+- include: mode_cleanup.yaml
118 118
 
119 119
 # a literal 600 as the mode will fail currently, in the sense that it
120 120
 # doesn't guess and consider 600 and 0600 to be the same, and will instead
... ...
@@ -127,4 +127,4 @@
127 127
 # See https://github.com/ansible/ansible/issues/16370
128 128
 - name: Assert mode_given_yaml_literal_600 is correct
129 129
   assert:
130
-    that: "mode_given_yaml_literal_600.stat.mode == '1130'"
130
+    that: "mode_given_yaml_literal_600.stat.mode == '1130'"
131 131
\ No newline at end of file
132 132
deleted file mode 100644
... ...
@@ -1 +0,0 @@
1
-shippable/posix/group5
2 1
deleted file mode 100644
... ...
@@ -1,36 +0,0 @@
1
-#!/usr/bin/python
2
-# -*- coding: utf-8 -*-
3
-# Copyright (c) 2020 Ansible Project
4
-# GNU General Public License v3.0+ (see COPYING or https://www.gnu.org/licenses/gpl-3.0.txt)
5
-
6
-from __future__ import absolute_import, division, print_function
7
-__metaclass__ = type
8
-
9
-import tempfile
10
-
11
-from ansible.module_utils.basic import AnsibleModule
12
-
13
-
14
-def main():
15
-    module = AnsibleModule(
16
-        argument_spec={
17
-            'dest': {'type': 'path'},
18
-            'call_fs_attributes': {'type': 'bool', 'default': True},
19
-        },
20
-        add_file_common_args=True,
21
-    )
22
-
23
-    results = {}
24
-
25
-    with tempfile.NamedTemporaryFile(delete=False) as tf:
26
-        file_args = module.load_file_common_arguments(module.params)
27
-        module.atomic_move(tf.name, module.params['dest'])
28
-
29
-        if module.params['call_fs_attributes']:
30
-            results['changed'] = module.set_fs_attributes_if_different(file_args, True)
31
-
32
-    module.exit_json(**results)
33
-
34
-
35
-if __name__ == '__main__':
36
-    main()
37 1
deleted file mode 100644
... ...
@@ -1,2 +0,0 @@
1
-dependencies:
2
-  - setup_remote_tmp_dir
3 1
deleted file mode 100644
... ...
@@ -1,33 +0,0 @@
1
-- name: Run task with no mode
2
-  test_perm_warning:
3
-    dest: "{{ remote_tmp_dir }}/endangerdisown"
4
-  register: no_mode_results
5
-
6
-- name: Run task with mode
7
-  test_perm_warning:
8
-    mode: '0644'
9
-    dest: "{{ remote_tmp_dir }}/groveestablish"
10
-  register: with_mode_results
11
-
12
-- name: Run task without calling set_fs_attributes_if_different()
13
-  test_perm_warning:
14
-    call_fs_attributes: no
15
-    dest: "{{ remote_tmp_dir }}/referabletank"
16
-  register: skip_fs_attributes
17
-
18
-- stat:
19
-    path: "{{ remote_tmp_dir }}/{{ item }}"
20
-  loop:
21
-    - endangerdisown
22
-    - groveestablish
23
-  register: files
24
-
25
-- name: Ensure we get a warning when appropriate
26
-  assert:
27
-    that:
28
-      - no_mode_results.warnings | default([], True) | length == 1
29
-      - "'created with default permissions' in no_mode_results.warnings[0]"
30
-      - files.results[0]['stat']['mode'] == '0600'
31
-      - files.results[1]['stat']['mode'] == '0644'
32
-      - with_mode_results.warnings is not defined  # The Jinja version on CentOS 6 does not support default([], True)
33
-      - skip_fs_attributes.warnings | default([], True) | length == 1
... ...
@@ -63,7 +63,7 @@ def atomic_mocks(mocker, monkeypatch):
63 63
 @pytest.fixture
64 64
 def fake_stat(mocker):
65 65
     stat1 = mocker.MagicMock()
66
-    stat1.st_mode = 0o0600
66
+    stat1.st_mode = 0o0644
67 67
     stat1.st_uid = 0
68 68
     stat1.st_gid = 0
69 69
     stat1.st_flags = 0
... ...
@@ -80,7 +80,7 @@ def test_new_file(atomic_am, atomic_mocks, mocker, selinux):
80 80
     atomic_am.atomic_move('/path/to/src', '/path/to/dest')
81 81
 
82 82
     atomic_mocks['rename'].assert_called_with(b'/path/to/src', b'/path/to/dest')
83
-    assert atomic_mocks['chmod'].call_args_list == [mocker.call(b'/path/to/dest', basic.DEFAULT_PERM & ~0o022)]
83
+    assert atomic_mocks['chmod'].call_args_list == [mocker.call(b'/path/to/dest', basic.DEFAULT_PERM & ~18)]
84 84
 
85 85
     if selinux:
86 86
         assert atomic_am.selinux_default_context.call_args_list == [mocker.call('/path/to/dest')]
... ...
@@ -101,7 +101,7 @@ def test_existing_file(atomic_am, atomic_mocks, fake_stat, mocker, selinux):
101 101
     atomic_am.atomic_move('/path/to/src', '/path/to/dest')
102 102
 
103 103
     atomic_mocks['rename'].assert_called_with(b'/path/to/src', b'/path/to/dest')
104
-    assert atomic_mocks['chmod'].call_args_list == [mocker.call(b'/path/to/src', basic.DEFAULT_PERM & ~0o022)]
104
+    assert atomic_mocks['chmod'].call_args_list == [mocker.call(b'/path/to/src', basic.DEFAULT_PERM & ~18)]
105 105
 
106 106
     if selinux:
107 107
         assert atomic_am.set_context_if_different.call_args_list == [mocker.call('/path/to/dest', mock_context, False)]
... ...
@@ -124,7 +124,7 @@ def test_no_tty_fallback(atomic_am, atomic_mocks, fake_stat, mocker):
124 124
     atomic_am.atomic_move('/path/to/src', '/path/to/dest')
125 125
 
126 126
     atomic_mocks['rename'].assert_called_with(b'/path/to/src', b'/path/to/dest')
127
-    assert atomic_mocks['chmod'].call_args_list == [mocker.call(b'/path/to/src', basic.DEFAULT_PERM & ~0o022)]
127
+    assert atomic_mocks['chmod'].call_args_list == [mocker.call(b'/path/to/src', basic.DEFAULT_PERM & ~18)]
128 128
 
129 129
     assert atomic_am.set_context_if_different.call_args_list == [mocker.call('/path/to/dest', mock_context, False)]
130 130
     assert atomic_am.selinux_context.call_args_list == [mocker.call('/path/to/dest')]
... ...
@@ -154,7 +154,7 @@ def test_existing_file_stat_perms_failure(atomic_am, atomic_mocks, mocker):
154 154
     atomic_mocks['rename'].assert_called_with(b'/path/to/src', b'/path/to/dest')
155 155
     # FIXME: Should atomic_move() set a default permission value when it cannot retrieve the
156 156
     # existing file's permissions?  (Right now it's up to the calling code.
157
-    # assert atomic_mocks['chmod'].call_args_list == [mocker.call(b'/path/to/src', basic.DEFAULT_PERM & ~0o022)]
157
+    # assert atomic_mocks['chmod'].call_args_list == [mocker.call(b'/path/to/src', basic.DEFAULT_PERM & ~18)]
158 158
     assert atomic_am.set_context_if_different.call_args_list == [mocker.call('/path/to/dest', mock_context, False)]
159 159
     assert atomic_am.selinux_context.call_args_list == [mocker.call('/path/to/dest')]
160 160
 
... ...
@@ -211,7 +211,7 @@ def test_rename_perms_fail_temp_succeeds(atomic_am, atomic_mocks, fake_stat, moc
211 211
     atomic_am.atomic_move('/path/to/src', '/path/to/dest')
212 212
     assert atomic_mocks['rename'].call_args_list == [mocker.call(b'/path/to/src', b'/path/to/dest'),
213 213
                                                      mocker.call(b'/path/to/tempfile', b'/path/to/dest')]
214
-    assert atomic_mocks['chmod'].call_args_list == [mocker.call(b'/path/to/dest', basic.DEFAULT_PERM & ~0o022)]
214
+    assert atomic_mocks['chmod'].call_args_list == [mocker.call(b'/path/to/dest', basic.DEFAULT_PERM & ~18)]
215 215
 
216 216
     if selinux:
217 217
         assert atomic_am.selinux_default_context.call_args_list == [mocker.call('/path/to/dest')]