decrypt: AOSP 10 requires the use of fscrypt
fscrypt aosp doc: https://source.android.com/security/encryption/file-based
kernel fscrypt doc: https://www.kernel.org/doc/html/v4.18/filesystems/fscrypt.html
This commit implements the ability for TWRP to use fscrypt to decrypt
files on the fscrypt implementation. It has been implemented mostly
in a new successor library to e4crypt called libtwrpfscrypt. Most of the
code was ported from AOSP vold.
Notable updates include:
- updated policy storage by libtar
- lookup of fbe policies by libtwrpfscrypt
- threaded keystore operations
Big thanks to Dees_Troy for the initial trailblazing
of encryption in TWRP.
Change-Id: I69cd2eba3693a9914e00213d4943229635d0cdae
diff --git a/crypto/fscrypt/MetadataCrypt.cpp b/crypto/fscrypt/MetadataCrypt.cpp
new file mode 100755
index 0000000..45f3af3
--- /dev/null
+++ b/crypto/fscrypt/MetadataCrypt.cpp
@@ -0,0 +1,304 @@
+/*
+ * Copyright (C) 2016 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.
+ */
+
+#include "MetadataCrypt.h"
+#include "KeyBuffer.h"
+
+#include <algorithm>
+#include <string>
+#include <thread>
+#include <vector>
+
+#include <fcntl.h>
+#include <sys/ioctl.h>
+#include <sys/param.h>
+#include <sys/stat.h>
+#include <sys/types.h>
+
+#include <linux/dm-ioctl.h>
+
+#include <android-base/file.h>
+#include <android-base/logging.h>
+#include <android-base/properties.h>
+#include <android-base/unique_fd.h>
+#include <cutils/fs.h>
+#include <fs_mgr.h>
+
+#include "Checkpoint.h"
+#include "EncryptInplace.h"
+#include "KeyStorage.h"
+#include "KeyUtil.h"
+#include "Keymaster.h"
+#include "Utils.h"
+#include "VoldUtil.h"
+
+#define DM_CRYPT_BUF_SIZE 4096
+#define TABLE_LOAD_RETRIES 10
+#define DEFAULT_KEY_TARGET_TYPE "default-key"
+
+using android::fs_mgr::FstabEntry;
+using android::fs_mgr::GetEntryForMountPoint;
+using android::fs_mgr::ReadDefaultFstab;
+using android::vold::KeyBuffer;
+
+static const std::string kDmNameUserdata = "userdata";
+
+static const char* kFn_keymaster_key_blob = "keymaster_key_blob";
+static const char* kFn_keymaster_key_blob_upgraded = "keymaster_key_blob_upgraded";
+
+static bool mount_via_fs_mgr(const char* mount_point, const char* blk_device) {
+ // fs_mgr_do_mount runs fsck. Use setexeccon to run trusted
+ // partitions in the fsck domain.
+ if (setexeccon(android::vold::sFsckContext)) {
+ PLOG(ERROR) << "Failed to setexeccon";
+ return false;
+ }
+ auto mount_rc = fs_mgr_do_mount(&fstab_default, const_cast<char*>(mount_point),
+ const_cast<char*>(blk_device), nullptr,
+ false);
+ if (setexeccon(nullptr)) {
+ PLOG(ERROR) << "Failed to clear setexeccon";
+ return false;
+ }
+ if (mount_rc != 0) {
+ LOG(ERROR) << "fs_mgr_do_mount failed with rc " << mount_rc;
+ return false;
+ }
+ LOG(DEBUG) << "Mounted " << mount_point;
+ return true;
+}
+
+android::fs_mgr::Fstab fstab_default;
+
+namespace android {
+namespace vold {
+
+// Note: It is possible to orphan a key if it is removed before deleting
+// Update this once keymaster APIs change, and we have a proper commit.
+static void commit_key(const std::string& dir) {
+ while (!android::base::WaitForProperty("vold.checkpoint_committed", "1")) {
+ LOG(ERROR) << "Wait for boot timed out";
+ }
+ Keymaster keymaster;
+ auto keyPath = dir + "/" + kFn_keymaster_key_blob;
+ auto newKeyPath = dir + "/" + kFn_keymaster_key_blob_upgraded;
+ std::string key;
+
+ if (!android::base::ReadFileToString(keyPath, &key)) {
+ LOG(ERROR) << "Failed to read old key: " << dir;
+ return;
+ }
+ if (rename(newKeyPath.c_str(), keyPath.c_str()) != 0) {
+ PLOG(ERROR) << "Unable to move upgraded key to location: " << keyPath;
+ return;
+ }
+ if (!keymaster.deleteKey(key)) {
+ LOG(ERROR) << "Key deletion failed during upgrade, continuing anyway: " << dir;
+ }
+ LOG(INFO) << "Old Key deleted: " << dir;
+}
+
+static bool read_key(const FstabEntry& data_rec, bool create_if_absent, KeyBuffer* key) {
+ if (data_rec.key_dir.empty()) {
+ LOG(ERROR) << "Failed to get key_dir";
+ return false;
+ }
+ std::string key_dir = data_rec.key_dir;
+ std::string sKey;
+ auto dir = key_dir + "/key";
+ LOG(DEBUG) << "key_dir/key: " << dir;
+ if (fs_mkdirs(dir.c_str(), 0700)) {
+ PLOG(ERROR) << "Creating directories: " << dir;
+ return false;
+ }
+ auto temp = key_dir + "/tmp";
+ auto newKeyPath = dir + "/" + kFn_keymaster_key_blob_upgraded;
+ /* If we have a leftover upgraded key, delete it.
+ * We either failed an update and must return to the old key,
+ * or we rebooted before commiting the keys in a freak accident.
+ * Either way, we can re-upgrade the key if we need to.
+ */
+ Keymaster keymaster;
+ if (pathExists(newKeyPath)) {
+ if (!android::base::ReadFileToString(newKeyPath, &sKey))
+ LOG(ERROR) << "Failed to read old key: " << dir;
+ else if (!keymaster.deleteKey(sKey))
+ LOG(ERROR) << "Old key deletion failed, continuing anyway: " << dir;
+ else
+ unlink(newKeyPath.c_str());
+ }
+ // bool needs_cp = cp_needsCheckpoint();
+ bool needs_cp = false;
+ if (!android::vold::retrieveKey(create_if_absent, dir, temp, key, needs_cp)) return false;
+ if (needs_cp && pathExists(newKeyPath)) std::thread(commit_key, dir).detach();
+ return true;
+}
+
+} // namespace vold
+} // namespace android
+
+static KeyBuffer default_key_params(const std::string& real_blkdev, const KeyBuffer& key) {
+ KeyBuffer hex_key;
+ if (android::vold::StrToHex(key, hex_key) != android::OK) {
+ LOG(ERROR) << "Failed to turn key to hex";
+ return KeyBuffer();
+ }
+ auto res = KeyBuffer() + "AES-256-XTS " + hex_key + " " + real_blkdev.c_str() + " 0";
+ return res;
+}
+
+static bool get_number_of_sectors(const std::string& real_blkdev, uint64_t* nr_sec) {
+ if (android::vold::GetBlockDev512Sectors(real_blkdev, nr_sec) != android::OK) {
+ PLOG(ERROR) << "Unable to measure size of " << real_blkdev;
+ return false;
+ }
+ return true;
+}
+
+static struct dm_ioctl* dm_ioctl_init(char* buffer, size_t buffer_size, const std::string& dm_name) {
+ if (buffer_size < sizeof(dm_ioctl)) {
+ LOG(ERROR) << "dm_ioctl buffer too small";
+ return nullptr;
+ }
+
+ memset(buffer, 0, buffer_size);
+ struct dm_ioctl* io = (struct dm_ioctl*)buffer;
+ io->data_size = buffer_size;
+ io->data_start = sizeof(struct dm_ioctl);
+ io->version[0] = 4;
+ io->version[1] = 0;
+ io->version[2] = 0;
+ io->flags = 0;
+ dm_name.copy(io->name, sizeof(io->name));
+ return io;
+}
+
+static bool create_crypto_blk_dev(const std::string& dm_name, uint64_t nr_sec,
+ const std::string& target_type, const KeyBuffer& crypt_params,
+ std::string* crypto_blkdev) {
+ android::base::unique_fd dm_fd(
+ TEMP_FAILURE_RETRY(open("/dev/device-mapper", O_RDWR | O_CLOEXEC, 0)));
+ if (dm_fd == -1) {
+ PLOG(ERROR) << "Cannot open device-mapper";
+ return false;
+ }
+ alignas(struct dm_ioctl) char buffer[DM_CRYPT_BUF_SIZE];
+ auto io = dm_ioctl_init(buffer, sizeof(buffer), dm_name);
+ if (!io || ioctl(dm_fd.get(), DM_DEV_CREATE, io) != 0) {
+ PLOG(ERROR) << "Cannot create dm-crypt device " << dm_name;
+ return false;
+ }
+
+ // Get the device status, in particular, the name of its device file
+ io = dm_ioctl_init(buffer, sizeof(buffer), dm_name);
+ if (ioctl(dm_fd.get(), DM_DEV_STATUS, io) != 0) {
+ PLOG(ERROR) << "Cannot retrieve dm-crypt device status " << dm_name;
+ return false;
+ }
+ *crypto_blkdev = std::string() + "/dev/block/dm-" +
+ std::to_string((io->dev & 0xff) | ((io->dev >> 12) & 0xfff00));
+
+ io = dm_ioctl_init(buffer, sizeof(buffer), dm_name);
+ size_t paramix = io->data_start + sizeof(struct dm_target_spec);
+ size_t nullix = paramix + crypt_params.size();
+ size_t endix = (nullix + 1 + 7) & 8; // Add room for \0 and align to 8 byte boundary
+
+ if (endix > sizeof(buffer)) {
+ LOG(ERROR) << "crypt_params too big for DM_CRYPT_BUF_SIZE";
+ return false;
+ }
+
+ io->target_count = 1;
+ auto tgt = (struct dm_target_spec*)(buffer + io->data_start);
+ tgt->status = 0;
+ tgt->sector_start = 0;
+ tgt->length = nr_sec;
+ target_type.copy(tgt->target_type, sizeof(tgt->target_type));
+ memcpy(buffer + paramix, crypt_params.data(),
+ std::min(crypt_params.size(), sizeof(buffer) - paramix));
+ buffer[nullix] = '\0';
+ tgt->next = endix;
+
+ for (int i = 0;; i++) {
+ if (ioctl(dm_fd.get(), DM_TABLE_LOAD, io) == 0) {
+ break;
+ }
+ if (i + 1 >= TABLE_LOAD_RETRIES) {
+ PLOG(ERROR) << "DM_TABLE_LOAD ioctl failed";
+ return false;
+ }
+ PLOG(INFO) << "DM_TABLE_LOAD ioctl failed, retrying";
+ usleep(500000);
+ }
+
+ // Resume this device to activate it
+ io = dm_ioctl_init(buffer, sizeof(buffer), dm_name);
+ if (ioctl(dm_fd.get(), DM_DEV_SUSPEND, io)) {
+ PLOG(ERROR) << "Cannot resume dm-crypt device " << dm_name;
+ return false;
+ }
+ return true;
+}
+
+bool fscrypt_mount_metadata_encrypted(const std::string& blk_device, const std::string& mount_point,
+ bool needs_encrypt) {
+ LOG(ERROR) << "fscrypt_mount_metadata_encrypted: " << blk_device << " " << mount_point << " " << needs_encrypt;
+ // auto encrypted_state = android::base::GetProperty("ro.crypto.state", "");
+ // if (encrypted_state != "") {
+ // LOG(ERROR) << "fscrypt_enable_crypto got unexpected starting state: " << encrypted_state;
+ // return false;
+ // }
+
+ if (!ReadDefaultFstab(&fstab_default)) {
+ PLOG(ERROR) << "Failed to open default fstab";
+ return -1;
+ }
+
+ auto data_rec = GetEntryForMountPoint(&fstab_default, mount_point);
+ if (!data_rec) {
+ LOG(ERROR) << "Failed to get data_rec";
+ return false;
+ }
+ KeyBuffer key;
+ if (!read_key(*data_rec, needs_encrypt, &key)) return false;
+ uint64_t nr_sec;
+ if (!get_number_of_sectors(data_rec->blk_device, &nr_sec)) return false;
+ std::string crypto_blkdev;
+ if (!create_crypto_blk_dev(kDmNameUserdata, nr_sec, DEFAULT_KEY_TARGET_TYPE,
+ default_key_params(blk_device, key), &crypto_blkdev))
+ return false;
+ // FIXME handle the corrupt case
+ if (needs_encrypt) {
+ LOG(INFO) << "Beginning inplace encryption, nr_sec: " << nr_sec;
+ off64_t size_already_done = 0;
+ auto rc = cryptfs_enable_inplace(crypto_blkdev.data(), blk_device.data(), nr_sec,
+ &size_already_done, nr_sec, 0, false);
+ if (rc != 0) {
+ LOG(ERROR) << "Inplace crypto failed with code: " << rc;
+ return false;
+ }
+ if (static_cast<uint64_t>(size_already_done) != nr_sec) {
+ LOG(ERROR) << "Inplace crypto only got up to sector: " << size_already_done;
+ return false;
+ }
+ LOG(INFO) << "Inplace encryption complete";
+ }
+
+ LOG(ERROR) << "Mounting metadata-encrypted filesystem:" << mount_point;
+ mount_via_fs_mgr(data_rec->mount_point.c_str(), crypto_blkdev.c_str());
+ android::base::SetProperty("ro.crypto.fs_crypto_blkdev", crypto_blkdev);
+ return true;
+}