# 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.

from autotest_lib.client.common_lib import utils

AUTHOR = "Chromium OS"
NAME = "autoupdate_CatchBadSignatures"
TIME = "MEDIUM"
TEST_CATEGORY = "Functional"
TEST_CLASS = "platform"
TEST_TYPE = "server"
ATTRIBUTES = "suite:au-perbuild"

DOC = """
This is a test to verify that update_engine correctly checks signatures in the
metadata hash and the update payload itself. This is achieved by feeding updates
to update_engine where the private key used to make the signature, intentionally
does not match with the public key used for verification.

By its very nature, this test requires an image signed with a well-known
key. Since payload-generation is a resource-intensive process, we prepare the
image ahead of time. Also, since the image is never successfully applied, we can
get away with not caring that the image is built for one board but used on
another.

If you ever need to replace the test image and payloads, follow these simple
(jk!) steps:

  1. Build a test image:

     $ cd ~/trunk/src/scripts
     $ ./build_packages --board=${BOARD}
     $ ./build_image --board=${BOARD} --noenable_rootfs_verification test

     Alternatively, you can use any kind of Chrome OS image you already have or
     downloaded.

  2. Reduce the size of Rootfs and Kernel partitions. This is done so these
     autotests don't have to download a huge payload as the payload is not going
     to be applied fully anyway. This can be done many ways. One is:

     $ sudo losetup -fP chromiumos_test_image.bin

     At this point take a note of which loopback device was set up for the
     image. e.g. /dev/loop1

     $ sudo mkfs.ext4 -b 4k /dev/loop1p3 100  # For ROOT-A
     $ sudo mkfs.ext4 -b 4k /dev/loop1p4 100  # For KERN-B
     $ mkdir rootfs kernel
     $ sudo mount /dev/loop1p3 rootfs
     $ sudo mount /dev/loop1p4 kernel

     Now you need a lsb-release file copied from any Chrome OS.

     $ mkdir rootfs/etc && touch cp <lsb-release> rootfs/etc
     $ touch kernel/fake-kernel.bin # Optional
     $ sudo umount rootfs kernel

     Now, the chromiumos_test_image.bin has very small Rootfs and Kernel
     partitions.

  3. Generate a full payload in which its metadata and payload signatures are
     signed by two different private keys. An update payload has two signatures
     embedded in it. The first is the signature of the header (metadata
     signature) and the second is the signature of the entire payload (payload
     signature). We do two tests here: One that makes sure the metadata
     signature verification fails if signed incorrectly (we do this by sending a
     different public key that doesn't verify the aforementioned signature). The
     second one to make sure the metadata signature verification passes fine,
     but the payload signature verification fails. One (not so) simple, but
     available way of doing this is as follows:

     Since we can't generate a payload with metadata and payload signatures
     signed by different keys (simply we haven't designed tools for that), we
     need to sign a payload two times with different keys and swap the payload
     signature of one of them with the other.

     $ mkdir key1 key2
     $ cros_generate_update_payload \
         --image chromiumos_test_image.bin \
         --output key1/full.bin \
         --work_dir key1 \
         --private_key ~/trunk/src/aosp/system/update_engine/unittest_key.pem
     $ cros_generate_update_payload \
         --image chromiumos_test_image.bin \
         --output key2/full.bin \
         --work_dir key2 \
         --private_key ~/trunk/src/aosp/system/update_engine/unittest_key2.pem

     Now we should re-sign an unsigned image (key1/delta.bin) with metadata
     signature from key1 and payload signature from key2 directories. Because we
     passed the --work_dir flag, the intermediate temporary files (including
     signature files) are saved in those directories.

     $ delta_generator \
        --in_file=key1/delta.bin \
        --metadata_signature_file=key1/signature_metadata_<hash>.bin \
        --payload_signature_file=key2/signature_payload_<hash>.bin \
        --out_file=autoupdate_CatchBadSignatures.bin

     This file is signed and ready to be tested.

  4. Generate/modify a payload properties file. For each payload we need a
     payload properties file in JSON format. This file has already been
     generated in the previous step when we generated the signed image. We just
     need to modify it.

     $ cp key1/delta.bin.json autoupdate_CatchBadSignatures.bin.json

     However, since we re-signed the payload, we need to calculate its SHA256
     hash again. Easy way to do this is to use either delta_generator or
     cros_generate_update_payload as:

     $  cros_generate_update_payload \
        --payload autoupdate_CatchBadSignatures.bin --output foo.json

     Open autoupdate_CatchBadSignatures.bin.json and replace the value of
     sha256_hex with the one from foo.json. Also empty the value of 'appid'
     (keep its key) to empty string.

  5. Replace _IMAGE_PUBLIC_KEY2 in this file with value in
     key2/full.bin.json. (You don't need to do this step if you used the same
     keys as mentioned above.)

  6. Upload the generated payload and its properties file to the public
     gsbucket.

  7. Now run the test and ensure that it passes.

    $ cd ~/trunk/src/scripts
    $ test_that -b ${BOARD} --fast <DUT_IP> autoupdate_CatchBadSignatures

With this in place, you can now run the test:

  $ test_that <DUT_IP> autoupdate_CatchBadSignatures -b ${BOARD}

"""

def run_test(machine):
    """Execute a test configuration on a given machine."""
    host = hosts.create_host(machine)
    job.run_test("autoupdate_CatchBadSignatures", host=host)

# Invoke parallel tests.
parallel_simple(run_test, machines)