system/update_engine/update_metadata.proto

//
// Copyright (C) 2010 The Android Open Source Project
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

// Update file format: A delta update file contains all the deltas needed
// to update a system from one specific version to another specific
// version. The update format is represented by this struct pseudocode:
// struct delta_update_file {
//   char magic[4] = "CrAU";
//   uint64 file_format_version;
//   uint64 manifest_size;  // Size of protobuf DeltaArchiveManifest
//
//   // Only present if format_version > 1:
//   uint32 metadata_signature_size;
//
//   // The Bzip2 compressed DeltaArchiveManifest
//   char manifest[];
//
//   // The signature of the metadata (from the beginning of the payload up to
//   // this location, not including the signature itself). This is a serialized
//   // Signatures message.
//   char medatada_signature_message[metadata_signature_size];
//
//   // Data blobs for files, no specific format. The specific offset
//   // and length of each data blob is recorded in the DeltaArchiveManifest.
//   struct {
//     char data[];
//   } blobs[];
//
//   // These two are not signed:
//   uint64 payload_signatures_message_size;
//   char payload_signatures_message[];
//
// };

// The DeltaArchiveManifest protobuf is an ordered list of InstallOperation
// objects. These objects are stored in a linear array in the
// DeltaArchiveManifest. Each operation is applied in order by the client.

// The DeltaArchiveManifest also contains the initial and final
// checksums for the device.

// The client will perform each InstallOperation in order, beginning even
// before the entire delta file is downloaded (but after at least the
// protobuf is downloaded). The types of operations are explained:
// - REPLACE: Replace the dst_extents on the drive with the attached data,
//   zero padding out to block size.
// - REPLACE_BZ: bzip2-uncompress the attached data and write it into
//   dst_extents on the drive, zero padding to block size.
// - MOVE: Copy the data in src_extents to dst_extents. Extents may overlap,
//   so it may be desirable to read all src_extents data into memory before
//   writing it out.
// - SOURCE_COPY: Copy the data in src_extents in the old partition to
//   dst_extents in the new partition. There's no overlapping of data because
//   the extents are in different partitions.
// - BSDIFF: Read src_length bytes from src_extents into memory, perform
//   bspatch with attached data, write new data to dst_extents, zero padding
//   to block size.
// - SOURCE_BSDIFF: Read the data in src_extents in the old partition, perform
//   bspatch with the attached data and write the new data to dst_extents in the
//   new partition.
// - ZERO: Write zeros to the destination dst_extents.
// - DISCARD: Discard the destination dst_extents blocks on the physical medium.
//   the data read from those block is undefined.
// - REPLACE_XZ: Replace the dst_extents with the contents of the attached
//   xz file after decompression. The xz file should only use crc32 or no crc at
//   all to be compatible with xz-embedded.
// - PUFFDIFF: Read the data in src_extents in the old partition, perform
//   puffpatch with the attached data and write the new data to dst_extents in
//   the new partition.
//
// The operations allowed in the payload (supported by the client) depend on the
// major and minor version. See InstallOperation.Type bellow for details.

syntax = "proto2";

package chromeos_update_engine;
option optimize_for = LITE_RUNTIME;

// Data is packed into blocks on disk, always starting from the beginning
// of the block. If a file's data is too large for one block, it overflows
// into another block, which may or may not be the following block on the
// physical partition. An ordered list of extents is another
// representation of an ordered list of blocks. For example, a file stored
// in blocks 9, 10, 11, 2, 18, 12 (in that order) would be stored in
// extents { {9, 3}, {2, 1}, {18, 1}, {12, 1} } (in that order).
// In general, files are stored sequentially on disk, so it's more efficient
// to use extents to encode the block lists (this is effectively
// run-length encoding).
// A sentinel value (kuint64max) as the start block denotes a sparse-hole
// in a file whose block-length is specified by num_blocks.

// Signatures: Updates may be signed by the OS vendor. The client verifies
// an update's signature by hashing the entire download. The section of the
// download that contains the signature is at the end of the file, so when
// signing a file, only the part up to the signature part is signed.
// Then, the client looks inside the download's Signatures message for a
// Signature message that it knows how to handle. Generally, a client will
// only know how to handle one type of signature, but an update may contain
// many signatures to support many different types of client. Then client
// selects a Signature message and uses that, along with a known public key,
// to verify the download. The public key is expected to be part of the
// client.

message Extent {
  optional uint64 start_block = 1;
  optional uint64 num_blocks = 2;
}

message Signatures {
  message Signature {
    optional uint32 version = 1;
    optional bytes data = 2;
  }
  repeated Signature signatures = 1;
}

message PartitionInfo {
  optional uint64 size = 1;
  optional bytes hash = 2;
}

// Describe an image we are based on in a human friendly way.
// Examples:
//   dev-channel, x86-alex, 1.2.3, mp-v3
//   nplusone-channel, x86-alex, 1.2.4, mp-v3, dev-channel, 1.2.3
//
// All fields will be set, if this message is present.
message ImageInfo {
  optional string board = 1;
  optional string key = 2;
  optional string channel = 3;
  optional string version = 4;

  // If these values aren't present, they should be assumed to match
  // the equivalent value above. They are normally only different for
  // special image types such as nplusone images.
  optional string build_channel = 5;
  optional string build_version = 6;
}

message InstallOperation {
  enum Type {
    REPLACE = 0;  // Replace destination extents w/ attached data
    REPLACE_BZ = 1;  // Replace destination extents w/ attached bzipped data
    MOVE = 2;  // Move source extents to destination extents
    BSDIFF = 3;  // The data is a bsdiff binary diff

    // On minor version 2 or newer, these operations are supported:
    SOURCE_COPY = 4; // Copy from source to target partition
    SOURCE_BSDIFF = 5; // Like BSDIFF, but read from source partition

    // On minor version 3 or newer and on major version 2 or newer, these
    // operations are supported:
    REPLACE_XZ = 8; // Replace destination extents w/ attached xz data.

    // On minor version 4 or newer, these operations are supported:
    ZERO = 6;  // Write zeros in the destination.
    DISCARD = 7;  // Discard the destination blocks, reading as undefined.
    BROTLI_BSDIFF = 10;  // Like SOURCE_BSDIFF, but compressed with brotli.

    // On minor version 5 or newer, these operations are supported:
    PUFFDIFF = 9;  // The data is in puffdiff format.
  }
  required Type type = 1;
  // The offset into the delta file (after the protobuf)
  // where the data (if any) is stored
  optional uint32 data_offset = 2;
  // The length of the data in the delta file
  optional uint32 data_length = 3;

  // Ordered list of extents that are read from (if any) and written to.
  repeated Extent src_extents = 4;
  // Byte length of src, equal to the number of blocks in src_extents *
  // block_size. It is used for BSDIFF and SOURCE_BSDIFF, because we need to
  // pass that external program the number of bytes to read from the blocks we
  // pass it.  This is not used in any other operation.
  optional uint64 src_length = 5;

  repeated Extent dst_extents = 6;
  // Byte length of dst, equal to the number of blocks in dst_extents *
  // block_size. Used for BSDIFF and SOURCE_BSDIFF, but not in any other
  // operation.
  optional uint64 dst_length = 7;

  // Optional SHA 256 hash of the blob associated with this operation.
  // This is used as a primary validation for http-based downloads and
  // as a defense-in-depth validation for https-based downloads. If
  // the operation doesn't refer to any blob, this field will have
  // zero bytes.
  optional bytes data_sha256_hash = 8;

  // Indicates the SHA 256 hash of the source data referenced in src_extents at
  // the time of applying the operation. If present, the update_engine daemon
  // MUST read and verify the source data before applying the operation.
  optional bytes src_sha256_hash = 9;
}

// Describes the update to apply to a single partition.
message PartitionUpdate {
  // A platform-specific name to identify the partition set being updated. For
  // example, in Chrome OS this could be "ROOT" or "KERNEL".
  required string partition_name = 1;

  // Whether this partition carries a filesystem with post-install program that
  // must be run to finalize the update process. See also |postinstall_path| and
  // |filesystem_type|.
  optional bool run_postinstall = 2;

  // The path of the executable program to run during the post-install step,
  // relative to the root of this filesystem. If not set, the default "postinst"
  // will be used. This setting is only used when |run_postinstall| is set and
  // true.
  optional string postinstall_path = 3;

  // The filesystem type as passed to the mount(2) syscall when mounting the new
  // filesystem to run the post-install program. If not set, a fixed list of
  // filesystems will be attempted. This setting is only used if
  // |run_postinstall| is set and true.
  optional string filesystem_type = 4;

  // If present, a list of signatures of the new_partition_info.hash signed with
  // different keys. If the update_engine daemon requires vendor-signed images
  // and has its public key installed, one of the signatures should be valid
  // for /postinstall to run.
  repeated Signatures.Signature new_partition_signature = 5;

  optional PartitionInfo old_partition_info = 6;
  optional PartitionInfo new_partition_info = 7;

  // The list of operations to be performed to apply this PartitionUpdate. The
  // associated operation blobs (in operations[i].data_offset, data_length)
  // should be stored contiguously and in the same order.
  repeated InstallOperation operations = 8;

  // Whether a failure in the postinstall step for this partition should be
  // ignored.
  optional bool postinstall_optional = 9;
}

message DeltaArchiveManifest {
  // Only present in major version = 1. List of install operations for the
  // kernel and rootfs partitions. For major version = 2 see the |partitions|
  // field.
  repeated InstallOperation install_operations = 1;
  repeated InstallOperation kernel_install_operations = 2;

  // (At time of writing) usually 4096
  optional uint32 block_size = 3 [default = 4096];

  // If signatures are present, the offset into the blobs, generally
  // tacked onto the end of the file, and the length. We use an offset
  // rather than a bool to allow for more flexibility in future file formats.
  // If either is absent, it means signatures aren't supported in this
  // file.
  optional uint64 signatures_offset = 4;
  optional uint64 signatures_size = 5;

  // Only present in major version = 1. Partition metadata used to validate the
  // update. For major version = 2 see the |partitions| field.
  optional PartitionInfo old_kernel_info = 6;
  optional PartitionInfo new_kernel_info = 7;
  optional PartitionInfo old_rootfs_info = 8;
  optional PartitionInfo new_rootfs_info = 9;

  // old_image_info will only be present for delta images.
  optional ImageInfo old_image_info = 10;

  optional ImageInfo new_image_info = 11;

  // The minor version, also referred as "delta version", of the payload.
  optional uint32 minor_version = 12 [default = 0];

  // Only present in major version >= 2. List of partitions that will be
  // updated, in the order they will be updated. This field replaces the
  // |install_operations|, |kernel_install_operations| and the
  // |{old,new}_{kernel,rootfs}_info| fields used in major version = 1. This
  // array can have more than two partitions if needed, and they are identified
  // by the partition name.
  repeated PartitionUpdate partitions = 13;

  // The maximum timestamp of the OS allowed to apply this payload.
  // Can be used to prevent downgrading the OS.
  optional int64 max_timestamp = 14;
}