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275 lines
7.7 KiB
275 lines
7.7 KiB
/*
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* Copyright (C) 2019 The Android Open Source Project
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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#include <errno.h>
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#include <fcntl.h>
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#include <inttypes.h>
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#include <libavb_user/libavb_user.h>
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#include <stdarg.h>
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#include <stdio.h>
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#include <sys/mount.h>
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#include <sys/stat.h>
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#include <unistd.h>
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#include <android-base/file.h>
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#include <android-base/logging.h>
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#include <android-base/properties.h>
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#include <android-base/stringprintf.h>
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#include <android-base/unique_fd.h>
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#include <fs_mgr.h>
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#include <fs_mgr_overlayfs.h>
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#include <fstab/fstab.h>
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#include <log/log_properties.h>
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#include "fec/io.h"
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#ifdef ALLOW_DISABLE_VERITY
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static const bool kAllowDisableVerity = true;
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#else
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static const bool kAllowDisableVerity = false;
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#endif
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using android::base::unique_fd;
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static void suggest_run_adb_root() {
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if (getuid() != 0) printf("Maybe run adb root?\n");
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}
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static bool make_block_device_writable(const std::string& dev) {
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unique_fd fd(open(dev.c_str(), O_RDONLY | O_CLOEXEC));
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if (fd == -1) {
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return false;
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}
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int OFF = 0;
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bool result = (ioctl(fd.get(), BLKROSET, &OFF) != -1);
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return result;
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}
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/* Turn verity on/off */
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static bool set_verity_enabled_state(const char* block_device, const char* mount_point,
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bool enable) {
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if (!make_block_device_writable(block_device)) {
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printf("Could not make block device %s writable (%s).\n", block_device, strerror(errno));
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return false;
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}
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fec::io fh(block_device, O_RDWR);
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if (!fh) {
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printf("Could not open block device %s (%s).\n", block_device, strerror(errno));
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suggest_run_adb_root();
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return false;
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}
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fec_verity_metadata metadata;
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if (!fh.get_verity_metadata(metadata)) {
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printf("Couldn't find verity metadata!\n");
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return false;
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}
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if (!enable && metadata.disabled) {
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printf("Verity already disabled on %s\n", mount_point);
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return false;
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}
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if (enable && !metadata.disabled) {
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printf("Verity already enabled on %s\n", mount_point);
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return false;
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}
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if (!fh.set_verity_status(enable)) {
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printf("Could not set verity %s flag on device %s with error %s\n",
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enable ? "enabled" : "disabled", block_device, strerror(errno));
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return false;
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}
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auto change = false;
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errno = 0;
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if (enable ? fs_mgr_overlayfs_teardown(mount_point, &change)
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: fs_mgr_overlayfs_setup(nullptr, mount_point, &change)) {
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if (change) {
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printf("%s overlayfs for %s\n", enable ? "disabling" : "using", mount_point);
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}
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} else if (errno) {
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int expected_errno = enable ? EBUSY : ENOENT;
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if (errno != expected_errno) {
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printf("Overlayfs %s for %s failed with error %s\n", enable ? "teardown" : "setup",
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mount_point, strerror(errno));
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}
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}
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printf("Verity %s on %s\n", enable ? "enabled" : "disabled", mount_point);
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return true;
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}
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/* Helper function to get A/B suffix, if any. If the device isn't
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* using A/B the empty string is returned. Otherwise either "_a",
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* "_b", ... is returned.
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*/
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static std::string get_ab_suffix() {
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return android::base::GetProperty("ro.boot.slot_suffix", "");
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}
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static bool is_avb_device_locked() {
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return android::base::GetProperty("ro.boot.vbmeta.device_state", "") == "locked";
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}
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static bool overlayfs_setup(bool enable) {
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auto change = false;
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errno = 0;
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if (enable ? fs_mgr_overlayfs_teardown(nullptr, &change)
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: fs_mgr_overlayfs_setup(nullptr, nullptr, &change)) {
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if (change) {
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printf("%s overlayfs\n", enable ? "disabling" : "using");
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}
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} else if (errno) {
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printf("Overlayfs %s failed with error %s\n", enable ? "teardown" : "setup", strerror(errno));
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suggest_run_adb_root();
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}
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return change;
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}
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/* Use AVB to turn verity on/off */
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static bool set_avb_verity_enabled_state(AvbOps* ops, bool enable_verity) {
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std::string ab_suffix = get_ab_suffix();
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bool verity_enabled;
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if (is_avb_device_locked()) {
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printf("Device is locked. Please unlock the device first\n");
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return false;
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}
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if (!avb_user_verity_get(ops, ab_suffix.c_str(), &verity_enabled)) {
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printf("Error getting verity state. Try adb root first?\n");
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return false;
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}
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if ((verity_enabled && enable_verity) || (!verity_enabled && !enable_verity)) {
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printf("verity is already %s\n", verity_enabled ? "enabled" : "disabled");
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return false;
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}
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if (!avb_user_verity_set(ops, ab_suffix.c_str(), enable_verity)) {
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printf("Error setting verity\n");
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return false;
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}
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overlayfs_setup(enable_verity);
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printf("Successfully %s verity\n", enable_verity ? "enabled" : "disabled");
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return true;
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}
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int main(int argc, char* argv[]) {
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if (argc == 0) {
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LOG(FATAL) << "set-verity-state called with empty argv";
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}
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std::optional<bool> enable_opt;
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std::string procname = android::base::Basename(argv[0]);
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if (procname == "enable-verity") {
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enable_opt = true;
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} else if (procname == "disable-verity") {
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enable_opt = false;
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}
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if (!enable_opt.has_value()) {
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if (argc != 2) {
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printf("usage: %s [1|0]\n", argv[0]);
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return 1;
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}
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if (strcmp(argv[1], "1") == 0) {
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enable_opt = true;
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} else if (strcmp(argv[1], "0") == 0) {
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enable_opt = false;
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} else {
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printf("usage: %s [1|0]\n", argv[0]);
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return 1;
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}
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}
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bool enable = enable_opt.value();
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bool any_changed = false;
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// Figure out if we're using VB1.0 or VB2.0 (aka AVB) - by
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// contract, androidboot.vbmeta.digest is set by the bootloader
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// when using AVB).
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bool using_avb = !android::base::GetProperty("ro.boot.vbmeta.digest", "").empty();
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// If using AVB, dm-verity is used on any build so we want it to
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// be possible to disable/enable on any build (except USER). For
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// VB1.0 dm-verity is only enabled on certain builds.
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if (!using_avb) {
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if (!kAllowDisableVerity) {
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printf("%s only works for userdebug builds\n", argv[0]);
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}
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if (!android::base::GetBoolProperty("ro.secure", false)) {
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overlayfs_setup(enable);
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printf("verity not enabled - ENG build\n");
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return 0;
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}
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}
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// Should never be possible to disable dm-verity on a USER build
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// regardless of using AVB or VB1.0.
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if (!__android_log_is_debuggable()) {
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printf("verity cannot be disabled/enabled - USER build\n");
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return 0;
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}
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if (using_avb) {
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// Yep, the system is using AVB.
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AvbOps* ops = avb_ops_user_new();
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if (ops == nullptr) {
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printf("Error getting AVB ops\n");
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return 1;
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}
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if (set_avb_verity_enabled_state(ops, enable)) {
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any_changed = true;
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}
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avb_ops_user_free(ops);
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} else {
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// Not using AVB - assume VB1.0.
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// read all fstab entries at once from all sources
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android::fs_mgr::Fstab fstab;
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if (!android::fs_mgr::ReadDefaultFstab(&fstab)) {
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printf("Failed to read fstab\n");
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suggest_run_adb_root();
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return 0;
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}
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// Loop through entries looking for ones that verity manages.
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for (const auto& entry : fstab) {
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if (entry.fs_mgr_flags.verify) {
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if (set_verity_enabled_state(entry.blk_device.c_str(), entry.mount_point.c_str(), enable)) {
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any_changed = true;
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}
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}
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}
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}
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if (!any_changed) any_changed = overlayfs_setup(enable);
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if (any_changed) {
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printf("Now reboot your device for settings to take effect\n");
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}
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return 0;
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}
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