CVE-2012-3447 (Python, published 2012-08-20T18:55Z)
Description: value: virt/disk/api.py in OpenStack Compute (Nova) 2012.1.x before 2012.1.2 and Folsom before Folsom-3 allows remote authenticated users to overwrite arbitrary files via a symlink attack on a file in an image that uses a symlink that is only readable by root.  NOTE: this vulnerability exists because of an incomplete fix for CVE-2012-3361.
Severity: MEDIUM (CVSS v3 base score: )
Weakness: CWE-264 \u2014 Permissions, Privileges, and Access Controls
Weaknesses in this category are related to the management of permissions, privileges, and other security features that are used to perform access control.
Repository: https://github.com/openstack/nova
Files changed:
nova/tests/test_virt.py
nova/tests/test_xenapi.py
nova/virt/disk/api.py
Commit message: Prohibit file injection writing to host filesystem

This is a refinement of the previous fix in commit 2427d4a9,
which does the file name canonicalization as the root user.
This is required so that guest images could not for example,
protect malicious symlinks in a directory only readable by root.

Fixes bug: 1031311, CVE-2012-3447
Change-Id: I7f7cdeeffadebae7451e1e13f73f1313a7df9c5c


Vulnerable code:
    def test_check_safe_path(self):
        ret = disk_api._join_and_check_path_within_fs('/foo', 'etc',
                                                      'something.conf')
        self.assertEquals(ret, '/foo/etc/something.conf')

    def test_check_unsafe_path(self):
        self.assertRaises(exception.Invalid,
                          disk_api._join_and_check_path_within_fs,
                          '/foo', 'etc/../../../something.conf')

    def test_inject_files_with_bad_path(self):
        self.assertRaises(exception.Invalid,
                          disk_api._inject_file_into_fs,
                          '/tmp', '/etc/../../../../etc/passwd',
                          'hax')

    absolute_path = os.path.realpath(os.path.join(fs, *args))

Fixed code:


class TestVirtDiskPaths(test.TestCase):
    def setUp(self):
        super(TestVirtDiskPaths, self).setUp()

        real_execute = utils.execute

        def nonroot_execute(*cmd_parts, **kwargs):
            kwargs.pop('run_as_root', None)
            return real_execute(*cmd_parts, **kwargs)

        self.stubs.Set(utils, 'execute', nonroot_execute)

    def test_check_safe_path(self):
        ret = disk_api._join_and_check_path_within_fs('/foo', 'etc',
                                                      'something.conf')
        self.assertEquals(ret, '/foo/etc/something.conf')

    def test_check_unsafe_path(self):
        self.assertRaises(exception.Invalid,
                          disk_api._join_and_check_path_within_fs,
                          '/foo', 'etc/../../../something.conf')

    def test_inject_files_with_bad_path(self):
        self.assertRaises(exception.Invalid,
                          disk_api._inject_file_into_fs,
                          '/tmp', '/etc/../../../../etc/passwd',
                          'hax')
        def _readlink_handler(cmd_parts, **kwargs):
            return os.path.realpath(cmd_parts[2]), ''

            (r'readlink -nm.*', _readlink_handler),
    absolute_path, _err = utils.execute('readlink', '-nm',
                                        os.path.join(fs, *args),
                                        run_as_root=True)