1 /* 2 * Copyright (C) 2017 The Android Open Source Project 3 * 4 * Licensed under the Apache License, Version 2.0 (the "License"); 5 * you may not use this file except in compliance with the License. 6 * You may obtain a copy of the License at 7 * 8 * http://www.apache.org/licenses/LICENSE-2.0 9 * 10 * Unless required by applicable law or agreed to in writing, software 11 * distributed under the License is distributed on an "AS IS" BASIS, 12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 13 * See the License for the specific language governing permissions and 14 * limitations under the License. 15 */ 16 17 #ifndef __CORE_FS_MGR_AVB_H 18 #define __CORE_FS_MGR_AVB_H 19 20 #include <map> 21 #include <memory> 22 #include <string> 23 24 #include <libavb/libavb.h> 25 26 #include "fs_mgr.h" 27 28 enum class SetUpAvbHashtreeResult { 29 kSuccess = 0, 30 kFail, 31 kDisabled, 32 }; 33 34 class FsManagerAvbOps; 35 36 class FsManagerAvbHandle; 37 using FsManagerAvbUniquePtr = std::unique_ptr<FsManagerAvbHandle>; 38 39 using ByNameSymlinkMap = std::map<std::string, std::string>; 40 41 // Provides a factory method to return a unique_ptr pointing to itself and the 42 // SetUpAvbHashtree() function to extract dm-verity parameters from AVB HASHTREE 43 // descriptors to load verity table into kernel through ioctl. 44 class FsManagerAvbHandle { 45 public: 46 // The factory method to return a FsManagerAvbUniquePtr that holds 47 // the verified AVB (external/avb) metadata of all verified partitions 48 // in avb_slot_data_.vbmeta_images[]. 49 // 50 // The metadata is checked against the following values from /proc/cmdline. 51 // - androidboot.vbmeta.{hash_alg, size, digest}. 52 // 53 // A typical usage will be: 54 // - FsManagerAvbUniquePtr handle = FsManagerAvbHandle::Open(); 55 // 56 // There are two overloaded Open() functions with a single parameter. 57 // The argument can be a ByNameSymlinkMap describing the mapping from partition 58 // name to by-name symlink, or a fstab file to which the ByNameSymlinkMap is 59 // constructed from. e.g., 60 // - /dev/block/platform/soc.0/7824900.sdhci/by-name/system_a -> 61 // - ByNameSymlinkMap["system_a"] = "/dev/block/platform/soc.0/7824900.sdhci/by-name/system_a" 62 // 63 // Possible return values: 64 // - nullptr: any error when reading and verifying the metadata, 65 // e.g., I/O error, digest value mismatch, size mismatch, etc. 66 // 67 // - a valid unique_ptr with status kAvbHandleHashtreeDisabled: 68 // to support the existing 'adb disable-verity' feature in Android. 69 // It's very helpful for developers to make the filesystem writable to 70 // allow replacing binaries on the device. 71 // 72 // - a valid unique_ptr with status kAvbHandleVerificationDisabled: 73 // to support 'avbctl disable-verification': only the top-level 74 // vbmeta is read, vbmeta structs in other partitions are not processed. 75 // It's needed to bypass AVB when using the generic system.img to run 76 // VTS for project Treble. 77 // 78 // - a valid unique_ptr with status kAvbHandleVerificationError: 79 // there is verification error when libavb loads vbmeta from each 80 // partition. This is only allowed when the device is unlocked. 81 // 82 // - a valid unique_ptr with status kAvbHandleSuccess: the metadata 83 // is verified and can be trusted. 84 // 85 static FsManagerAvbUniquePtr Open(const fstab& fstab); 86 static FsManagerAvbUniquePtr Open(ByNameSymlinkMap&& by_name_symlink_map); 87 88 // Sets up dm-verity on the given fstab entry. 89 // The 'wait_for_verity_dev' parameter makes this function wait for the 90 // verity device to get created before return. 91 // 92 // Return value: 93 // - kSuccess: successfully loads dm-verity table into kernel. 94 // - kFailed: failed to setup dm-verity, e.g., vbmeta verification error, 95 // failed to get the HASHTREE descriptor, runtime error when set up 96 // device-mapper, etc. 97 // - kDisabled: hashtree is disabled. 98 SetUpAvbHashtreeResult SetUpAvbHashtree(fstab_rec* fstab_entry, bool wait_for_verity_dev); 99 100 const std::string& avb_version() const { return avb_version_; } 101 102 FsManagerAvbHandle(const FsManagerAvbHandle&) = delete; // no copy 103 FsManagerAvbHandle& operator=(const FsManagerAvbHandle&) = delete; // no assignment 104 105 FsManagerAvbHandle(FsManagerAvbHandle&&) noexcept = delete; // no move 106 FsManagerAvbHandle& operator=(FsManagerAvbHandle&&) noexcept = delete; // no move assignment 107 108 ~FsManagerAvbHandle() { 109 if (avb_slot_data_) { 110 avb_slot_verify_data_free(avb_slot_data_); 111 } 112 }; 113 114 private: 115 enum AvbHandleStatus { 116 kAvbHandleSuccess = 0, 117 kAvbHandleUninitialized, 118 kAvbHandleHashtreeDisabled, 119 kAvbHandleVerificationDisabled, 120 kAvbHandleVerificationError, 121 }; 122 123 FsManagerAvbHandle() : avb_slot_data_(nullptr), status_(kAvbHandleUninitialized) {} 124 static FsManagerAvbUniquePtr DoOpen(FsManagerAvbOps* avb_ops); 125 126 AvbSlotVerifyData* avb_slot_data_; 127 AvbHandleStatus status_; 128 std::string avb_version_; 129 }; 130 131 #endif /* __CORE_FS_MGR_AVB_H */ 132
