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1# Copyright (c) 2014 The Chromium OS Authors. All rights reserved.
2# Use of this source code is governed by a BSD-style license that can be
3# found in the LICENSE file.
4"""A module containing rootfs handler class."""
5
6import os
7import re
8
9TMP_FILE_NAME = 'kernel_dump'
10
11_KERNEL_MAP = {'A': '2', 'B': '4'}
12_ROOTFS_MAP = {'A': '3', 'B': '5'}
13_DM_DEVICE = 'verifyroot'
14_DM_DEV_PATH = os.path.join('/dev/mapper', _DM_DEVICE)
15
16
17class RootfsHandler(object):
18    """An object to provide ChromeOS root FS related actions.
19
20    It provides functions to verify the integrity of the root FS.
21    """
22
23    def __init__(self):
24        self.os_if = None
25        self.root_dev = None
26        self.kernel_dump_file = None
27
28    def verify_rootfs(self, section):
29        """Verifies the integrity of the root FS.
30
31        @param section: The rootfs to verify. May be A or B.
32        """
33        kernel_path = self.os_if.join_part(self.root_dev,
34                                           _KERNEL_MAP[section.upper()])
35        rootfs_path = self.os_if.join_part(self.root_dev,
36                                           _ROOTFS_MAP[section.upper()])
37        # vbutil_kernel won't operate on a device, only a file.
38        self.os_if.run_shell_command(
39                'dd if=%s of=%s' % (kernel_path, self.kernel_dump_file))
40        vbutil_kernel = self.os_if.run_shell_command_get_output(
41                'vbutil_kernel --verify %s --verbose' % self.kernel_dump_file)
42        DM_REGEXP = re.compile(
43                r'dm="(?:1 )?vroot none ro(?: 1)?,(0 (\d+) .+)"')
44        match = DM_REGEXP.search('\n'.join(vbutil_kernel))
45        if not match:
46            return False
47
48        table = match.group(1)
49        partition_size = int(match.group(2)) * 512
50
51        if table.find('PARTUUID=%U/PARTNROFF=1') < 0:
52            return False
53        table = table.replace('PARTUUID=%U/PARTNROFF=1', rootfs_path)
54        # Cause I/O error on invalid bytes
55        table += ' error_behavior=eio'
56
57        self._remove_mapper()
58        assert not self.os_if.path_exists(_DM_DEV_PATH)
59        self.os_if.run_shell_command(
60                "dmsetup create -r %s --table '%s'" % (_DM_DEVICE, table))
61        assert self.os_if.path_exists(_DM_DEV_PATH)
62        try:
63            count = self.os_if.get_file_size(_DM_DEV_PATH)
64            return count == partition_size
65        except:
66            return False
67        finally:
68            self._remove_mapper()
69
70    def _remove_mapper(self):
71        """Removes the dm device mapper used by this class."""
72        if self.os_if.path_exists(_DM_DEV_PATH):
73            self.os_if.run_shell_command_get_output(
74                    'dmsetup remove %s' % _DM_DEVICE)
75
76    def init(self, os_if):
77        """Initialize the rootfs handler object.
78
79        @param os_if: OS interface object reference.
80        """
81        self.os_if = os_if
82        self.root_dev = os_if.get_root_dev()
83        self.kernel_dump_file = os_if.state_dir_file(TMP_FILE_NAME)
84