1/*
2 * Copyright (C) 2016 The Android Open Source Project
3 *
4 * Permission is hereby granted, free of charge, to any person
5 * obtaining a copy of this software and associated documentation
6 * files (the "Software"), to deal in the Software without
7 * restriction, including without limitation the rights to use, copy,
8 * modify, merge, publish, distribute, sublicense, and/or sell copies
9 * of the Software, and to permit persons to whom the Software is
10 * furnished to do so, subject to the following conditions:
11 *
12 * The above copyright notice and this permission notice shall be
13 * included in all copies or substantial portions of the Software.
14 *
15 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
16 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
17 * MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
18 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS
19 * BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN
20 * ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN
21 * CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
22 * SOFTWARE.
23 */
24
25#include "fs_mgr_priv_avb_ops.h"
26
27#include <errno.h>
28#include <fcntl.h>
29#include <stdlib.h>
30#include <string.h>
31#include <sys/stat.h>
32#include <string>
33
34#include <android-base/macros.h>
35#include <android-base/strings.h>
36#include <android-base/unique_fd.h>
37#include <libavb/libavb.h>
38#include <utils/Compat.h>
39
40#include "fs_mgr.h"
41#include "fs_mgr_priv.h"
42
43static AvbIOResult read_from_partition(AvbOps* ops, const char* partition, int64_t offset,
44                                       size_t num_bytes, void* buffer, size_t* out_num_read) {
45    return FsManagerAvbOps::GetInstanceFromAvbOps(ops)->ReadFromPartition(
46        partition, offset, num_bytes, buffer, out_num_read);
47}
48
49static AvbIOResult dummy_read_rollback_index(AvbOps* ops ATTRIBUTE_UNUSED,
50                                             size_t rollback_index_location ATTRIBUTE_UNUSED,
51                                             uint64_t* out_rollback_index) {
52    // rollback_index has been checked in bootloader phase.
53    // In user-space, returns the smallest value 0 to pass the check.
54    *out_rollback_index = 0;
55    return AVB_IO_RESULT_OK;
56}
57
58static AvbIOResult dummy_validate_vbmeta_public_key(
59    AvbOps* ops ATTRIBUTE_UNUSED, const uint8_t* public_key_data ATTRIBUTE_UNUSED,
60    size_t public_key_length ATTRIBUTE_UNUSED, const uint8_t* public_key_metadata ATTRIBUTE_UNUSED,
61    size_t public_key_metadata_length ATTRIBUTE_UNUSED, bool* out_is_trusted) {
62    // vbmeta public key has been checked in bootloader phase.
63    // In user-space, returns true to pass the check.
64    //
65    // Addtionally, user-space should check
66    // androidboot.vbmeta.{hash_alg, size, digest} against the digest
67    // of all vbmeta images after invoking avb_slot_verify().
68    *out_is_trusted = true;
69    return AVB_IO_RESULT_OK;
70}
71
72static AvbIOResult dummy_read_is_device_unlocked(AvbOps* ops ATTRIBUTE_UNUSED,
73                                                 bool* out_is_unlocked) {
74    // The function is for bootloader to update the value into
75    // androidboot.vbmeta.device_state in kernel cmdline.
76    // In user-space, returns true as we don't need to update it anymore.
77    *out_is_unlocked = true;
78    return AVB_IO_RESULT_OK;
79}
80
81static AvbIOResult dummy_get_unique_guid_for_partition(AvbOps* ops ATTRIBUTE_UNUSED,
82                                                       const char* partition ATTRIBUTE_UNUSED,
83                                                       char* guid_buf, size_t guid_buf_size) {
84    // The function is for bootloader to set the correct UUID
85    // for a given partition in kernel cmdline.
86    // In user-space, returns a faking one as we don't need to update
87    // it anymore.
88    snprintf(guid_buf, guid_buf_size, "1234-fake-guid-for:%s", partition);
89    return AVB_IO_RESULT_OK;
90}
91
92void FsManagerAvbOps::InitializeAvbOps() {
93    // We only need to provide the implementation of read_from_partition()
94    // operation since that's all what is being used by the avb_slot_verify().
95    // Other I/O operations are only required in bootloader but not in
96    // user-space so we set them as dummy operations.
97    avb_ops_.read_from_partition = read_from_partition;
98    avb_ops_.read_rollback_index = dummy_read_rollback_index;
99    avb_ops_.validate_vbmeta_public_key = dummy_validate_vbmeta_public_key;
100    avb_ops_.read_is_device_unlocked = dummy_read_is_device_unlocked;
101    avb_ops_.get_unique_guid_for_partition = dummy_get_unique_guid_for_partition;
102
103    // Sets user_data for GetInstanceFromAvbOps() to convert it back to FsManagerAvbOps.
104    avb_ops_.user_data = this;
105}
106
107FsManagerAvbOps::FsManagerAvbOps(std::map<std::string, std::string>&& by_name_symlink_map)
108    : by_name_symlink_map_(std::move(by_name_symlink_map)) {
109    InitializeAvbOps();
110}
111
112FsManagerAvbOps::FsManagerAvbOps(const fstab& fstab) {
113    // Constructs the by-name symlink map for each fstab record.
114    // /dev/block/platform/soc.0/7824900.sdhci/by-name/system_a =>
115    // by_name_symlink_map_["system_a"] = "/dev/block/platform/soc.0/7824900.sdhci/by-name/system_a"
116    for (int i = 0; i < fstab.num_entries; i++) {
117        std::string partition_name = basename(fstab.recs[i].blk_device);
118        by_name_symlink_map_[partition_name] = fstab.recs[i].blk_device;
119    }
120    InitializeAvbOps();
121}
122
123AvbIOResult FsManagerAvbOps::ReadFromPartition(const char* partition, int64_t offset,
124                                               size_t num_bytes, void* buffer,
125                                               size_t* out_num_read) {
126    const auto iter = by_name_symlink_map_.find(partition);
127    if (iter == by_name_symlink_map_.end()) {
128        LERROR << "by-name symlink not found for partition: '" << partition << "'";
129        return AVB_IO_RESULT_ERROR_NO_SUCH_PARTITION;
130    }
131    std::string path = iter->second;
132
133    // Ensures the device path (a symlink created by init) is ready to
134    // access. fs_mgr_test_access() will test a few iterations if the
135    // path doesn't exist yet.
136    if (fs_mgr_test_access(path.c_str()) < 0) {
137        return AVB_IO_RESULT_ERROR_NO_SUCH_PARTITION;
138    }
139
140    android::base::unique_fd fd(TEMP_FAILURE_RETRY(open(path.c_str(), O_RDONLY | O_CLOEXEC)));
141    if (fd < 0) {
142        PERROR << "Failed to open " << path;
143        return AVB_IO_RESULT_ERROR_IO;
144    }
145
146    // If offset is negative, interprets its absolute value as the
147    //  number of bytes from the end of the partition.
148    if (offset < 0) {
149        off64_t total_size = lseek64(fd, 0, SEEK_END);
150        if (total_size == -1) {
151            LERROR << "Failed to lseek64 to end of the partition";
152            return AVB_IO_RESULT_ERROR_IO;
153        }
154        offset = total_size + offset;
155        // Repositions the offset to the beginning.
156        if (lseek64(fd, 0, SEEK_SET) == -1) {
157            LERROR << "Failed to lseek64 to the beginning of the partition";
158            return AVB_IO_RESULT_ERROR_IO;
159        }
160    }
161
162    // On Linux, we never get partial reads from block devices (except
163    // for EOF).
164    ssize_t num_read = TEMP_FAILURE_RETRY(pread64(fd, buffer, num_bytes, offset));
165    if (num_read < 0 || (size_t)num_read != num_bytes) {
166        PERROR << "Failed to read " << num_bytes << " bytes from " << path << " offset " << offset;
167        return AVB_IO_RESULT_ERROR_IO;
168    }
169
170    if (out_num_read != nullptr) {
171        *out_num_read = num_read;
172    }
173
174    return AVB_IO_RESULT_OK;
175}
176
177AvbSlotVerifyResult FsManagerAvbOps::AvbSlotVerify(const std::string& ab_suffix,
178                                                   bool allow_verification_error,
179                                                   AvbSlotVerifyData** out_data) {
180    // Invokes avb_slot_verify() to load and verify all vbmeta images.
181    // Sets requested_partitions to nullptr as it's to copy the contents
182    // of HASH partitions into handle>avb_slot_data_, which is not required as
183    // fs_mgr only deals with HASHTREE partitions.
184    const char* requested_partitions[] = {nullptr};
185    return avb_slot_verify(&avb_ops_, requested_partitions, ab_suffix.c_str(),
186                           allow_verification_error, out_data);
187}
188