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/*
* Copyright (C) 2017 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.
*/
#ifndef __CORE_FS_MGR_AVB_H
#define __CORE_FS_MGR_AVB_H
#include <map>
#include <memory>
#include <string>
#include <libavb/libavb.h>
#include "fs_mgr.h"
enum class SetUpAvbHashtreeResult {
kSuccess = 0,
kFail,
kDisabled,
};
class FsManagerAvbOps;
class FsManagerAvbHandle;
using FsManagerAvbUniquePtr = std::unique_ptr<FsManagerAvbHandle>;
using ByNameSymlinkMap = std::map<std::string, std::string>;
// Provides a factory method to return a unique_ptr pointing to itself and the
// SetUpAvbHashtree() function to extract dm-verity parameters from AVB HASHTREE
// descriptors to load verity table into kernel through ioctl.
class FsManagerAvbHandle {
public:
// The factory method to return a FsManagerAvbUniquePtr that holds
// the verified AVB (external/avb) metadata of all verified partitions
// in avb_slot_data_.vbmeta_images[].
//
// The metadata is checked against the following values from /proc/cmdline.
// - androidboot.vbmeta.{hash_alg, size, digest}.
//
// A typical usage will be:
// - FsManagerAvbUniquePtr handle = FsManagerAvbHandle::Open();
//
// There are two overloaded Open() functions with a single parameter.
// The argument can be a ByNameSymlinkMap describing the mapping from partition
// name to by-name symlink, or a fstab file to which the ByNameSymlinkMap is
// constructed from. e.g.,
// - /dev/block/platform/soc.0/7824900.sdhci/by-name/system_a ->
// - ByNameSymlinkMap["system_a"] = "/dev/block/platform/soc.0/7824900.sdhci/by-name/system_a"
//
// Possible return values:
// - nullptr: any error when reading and verifying the metadata,
// e.g., I/O error, digest value mismatch, size mismatch, etc.
//
// - a valid unique_ptr with status kAvbHandleHashtreeDisabled:
// to support the existing 'adb disable-verity' feature in Android.
// It's very helpful for developers to make the filesystem writable to
// allow replacing binaries on the device.
//
// - a valid unique_ptr with status kAvbHandleVerificationDisabled:
// to support 'avbctl disable-verification': only the top-level
// vbmeta is read, vbmeta structs in other partitions are not processed.
// It's needed to bypass AVB when using the generic system.img to run
// VTS for project Treble.
//
// - a valid unique_ptr with status kAvbHandleVerificationError:
// there is verification error when libavb loads vbmeta from each
// partition. This is only allowed when the device is unlocked.
//
// - a valid unique_ptr with status kAvbHandleSuccess: the metadata
// is verified and can be trusted.
//
static FsManagerAvbUniquePtr Open(const fstab& fstab);
static FsManagerAvbUniquePtr Open(ByNameSymlinkMap&& by_name_symlink_map);
// Sets up dm-verity on the given fstab entry.
// The 'wait_for_verity_dev' parameter makes this function wait for the
// verity device to get created before return.
//
// Return value:
// - kSuccess: successfully loads dm-verity table into kernel.
// - kFailed: failed to setup dm-verity, e.g., vbmeta verification error,
// failed to get the HASHTREE descriptor, runtime error when set up
// device-mapper, etc.
// - kDisabled: hashtree is disabled.
SetUpAvbHashtreeResult SetUpAvbHashtree(fstab_rec* fstab_entry, bool wait_for_verity_dev);
const std::string& avb_version() const { return avb_version_; }
FsManagerAvbHandle(const FsManagerAvbHandle&) = delete; // no copy
FsManagerAvbHandle& operator=(const FsManagerAvbHandle&) = delete; // no assignment
FsManagerAvbHandle(FsManagerAvbHandle&&) noexcept = delete; // no move
FsManagerAvbHandle& operator=(FsManagerAvbHandle&&) noexcept = delete; // no move assignment
~FsManagerAvbHandle() {
if (avb_slot_data_) {
avb_slot_verify_data_free(avb_slot_data_);
}
};
private:
enum AvbHandleStatus {
kAvbHandleSuccess = 0,
kAvbHandleUninitialized,
kAvbHandleHashtreeDisabled,
kAvbHandleVerificationDisabled,
kAvbHandleVerificationError,
};
FsManagerAvbHandle() : avb_slot_data_(nullptr), status_(kAvbHandleUninitialized) {}
static FsManagerAvbUniquePtr DoOpen(FsManagerAvbOps* avb_ops);
AvbSlotVerifyData* avb_slot_data_;
AvbHandleStatus status_;
std::string avb_version_;
};
#endif /* __CORE_FS_MGR_AVB_H */
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