Update payload library + command-line tool

An initial implementation of a Python module for parsing, checking and
applying a Chrome OS update payload. Comes with a command-line tool
(paycheck.py) for applying such operations on payload files, and a test
script (test_paycheck.sh) for ensuring that the library and tool are
working correctly.

Since update_payload is introduced as a package, we're moving some
previously merged utilities into the package's directory.

(Unit testing for this code will be uploaded on a separate CL; see
chromium-os:39663)

BUG=chromium-os:34911,chromium-os:33607,chromium-os:7597
TEST=test_paycheck.sh successful on MP-signed payloads
CQ-DEPEND=I5746a1d80e822a575f0d96f94d0b4e765fc64507

Change-Id: I77123a1fffbb2059c239b7145c6922968fdffb6a
Reviewed-on: https://gerrit.chromium.org/gerrit/43041
Reviewed-by: Gilad Arnold <garnold@chromium.org>
Tested-by: Gilad Arnold <garnold@chromium.org>
Reviewed-by: Chris Sosa <sosa@chromium.org>
Reviewed-by: Jay Srinivasan <jaysri@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Commit-Queue: Gilad Arnold <garnold@chromium.org>
diff --git a/scripts/paycheck.py b/scripts/paycheck.py
new file mode 100755
index 0000000..77af744
--- /dev/null
+++ b/scripts/paycheck.py
@@ -0,0 +1,160 @@
+#!/usr/bin/python
+#
+# Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Command-line tool for checking and applying Chrome OS update payloads."""
+
+import optparse
+import os
+import sys
+
+# pylint: disable=F0401
+lib_dir = os.path.join(os.path.dirname(__file__), 'lib')
+if os.path.exists(lib_dir) and os.path.isdir(lib_dir):
+  sys.path.insert(1, lib_dir)
+import update_payload
+
+
+_TYPE_FULL = 'full'
+_TYPE_DELTA = 'delta'
+
+
+def ParseArguments(parser, argv):
+  """Parse and validate command-line arguments.
+
+  Args:
+    parser: the command-line parser
+  Returns:
+    A tuple (options, payload, extra_args), where `options' are the options
+    returned by the parser, `payload' is the name of the payload file
+    (mandatory argument) and `extra_args' are any additional command-line
+    arguments.
+
+  """
+  options, args = parser.parse_args(argv)
+
+  # Validate a value given to --type, if any.
+  if options.assert_type not in (None, _TYPE_FULL, _TYPE_DELTA):
+    parser.error('invalid argument to --type: %s' % options.assert_type)
+
+  # There are several options that imply --check.
+  options.check = (options.check or options.report or options.assert_type or
+                   options.block_size or options.allow_unhashed or
+                   options.key or options.meta_sig)
+
+  # Check number of arguments, enforce payload type accordingly.
+  if len(args) == 3:
+    if options.assert_type == _TYPE_DELTA:
+      parser.error('%s payload requires source partition arguments' %
+                   _TYPE_DELTA)
+    options.assert_type = _TYPE_FULL
+  elif len(args) == 5:
+    if options.assert_type == _TYPE_FULL:
+      parser.error('%s payload does not accept source partition arguments' %
+                   _TYPE_FULL)
+    options.assert_type = _TYPE_DELTA
+  elif len(args) != 1:
+    parser.error('unexpected number of arguments')
+
+  return options, args[0], args[1:]
+
+
+def main(argv):
+  parser = optparse.OptionParser(
+      usage='Usage: %prog [OPTION...] PAYLOAD [DST_KERN DST_ROOT '
+            '[SRC_KERN SRC_ROOT]]',
+      description='Applies a Chrome OS update PAYLOAD to SRC_KERN and '
+                  'SRC_ROOT emitting DST_KERN and DST_ROOT, respectively. '
+                  'SRC_KERN and SRC_ROOT need only be provided for delta '
+                  'payloads. If no partitions are provided, only verifies '
+                  'payload integrity.')
+
+  check_opts = optparse.OptionGroup(parser, 'Payload checking')
+  check_opts.add_option('-c', '--check', action='store_true', default=False,
+                        help='check payload integrity')
+  check_opts.add_option('-r', '--report', metavar='FILE',
+                        help="dump payload report (`-' for stdout)")
+  check_opts.add_option('-t', '--type', metavar='TYPE', dest='assert_type',
+                        help="assert that payload is either `%s' or `%s'" %
+                             (_TYPE_FULL, _TYPE_DELTA))
+  check_opts.add_option('-z', '--block-size', metavar='NUM', default=0,
+                        type='int',
+                        help='assert a non-default (4096) payload block size')
+  check_opts.add_option('-u', '--allow-unhashed', action='store_true',
+                        default=False, help='allow unhashed operations')
+  check_opts.add_option('-k', '--key', metavar='FILE',
+                        help='public key to be used for signature verification')
+  check_opts.add_option('-m', '--meta-sig', metavar='FILE',
+                        help='verify metadata against its signature')
+  parser.add_option_group(check_opts)
+
+  trace_opts = optparse.OptionGroup(parser, 'Block tracing')
+  trace_opts.add_option('-b', '--root-block', metavar='BLOCK', type='int',
+                        help='trace the origin for a rootfs block')
+  trace_opts.add_option('-B', '--kern-block', metavar='BLOCK', type='int',
+                        help='trace the origin for a kernel block')
+  trace_opts.add_option('-s', '--skip', metavar='NUM', default='0', type='int',
+                        help='skip first NUM occurrences of traced block')
+  parser.add_option_group(trace_opts)
+
+  # Parse and validate arguments.
+  options, payload_file_name, extra_args = ParseArguments(parser, argv[1:])
+
+  with open(payload_file_name) as payload_file:
+    payload = update_payload.Payload(payload_file)
+    try:
+      # Initialize payload.
+      payload.Init()
+
+      # Perform payload integrity checks.
+      if options.check:
+        report_file = None
+        do_close_report_file = False
+        try:
+          if options.report:
+            if options.report == '-':
+              report_file = sys.stdout
+            else:
+              report_file = open(options.report, 'w')
+              do_close_report_file = True
+
+          payload.Check(
+              pubkey_file_name=options.key,
+              metadata_sig_file=open(options.meta_sig)
+              if options.meta_sig else None,
+              report_out_file=report_file,
+              assert_type=options.assert_type,
+              block_size=int(options.block_size),
+              allow_unhashed=options.allow_unhashed)
+        finally:
+          if do_close_report_file:
+            report_file.close()
+
+      # Trace blocks.
+      if options.root_block is not None:
+        payload.TraceBlock(options.root_block, options.skip, sys.stdout, False)
+      if options.kern_block is not None:
+        payload.TraceBlock(options.kern_block, options.skip, sys.stdout, True)
+
+      # Apply payload.
+      if extra_args:
+        if options.assert_type == _TYPE_FULL:
+          payload.Apply(extra_args[0], extra_args[1])
+        elif options.assert_type == _TYPE_DELTA:
+          payload.Apply(extra_args[0], extra_args[1],
+                        src_kernel_part=extra_args[2],
+                        src_rootfs_part=extra_args[3])
+        else:
+          assert False, 'cannot get here'
+
+    except update_payload.PayloadError, e:
+      sys.stderr.write('Error: %s\n' % e)
+      return 1
+
+  return 0
+
+
+if __name__ == '__main__':
+  sys.exit(main(sys.argv))