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platform_system_vold/MetadataCrypt.cpp
Paul Crowley 0fd2626fc3 Add a mount with metadata encryption service 
Don't use the FDE flow to support metadata encryption; just provide a
vold service which directly mounts the volume and use that.

Bug: 63927601
Test: Boot Taimen to SUW with and without metadata encryption.
Change-Id: Ifc6a012c02c0ea66893020ed1d0da4cba6914aed
2018-02-01 10:08:17 -08:00

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8.5 KiB
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/*
* 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 "KeyBuffer.h"
#include "MetadataCrypt.h"
#include <string>
#include <thread>
#include <vector>
#include <algorithm>
#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/logging.h>
#include <android-base/properties.h>
#include <android-base/unique_fd.h>
#include <cutils/fs.h>
#include <fs_mgr.h>
#include "EncryptInplace.h"
#include "KeyStorage.h"
#include "KeyUtil.h"
#include "secontext.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::vold::KeyBuffer;
static const std::string kDmNameUserdata = "userdata";
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(secontextFsck())) {
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);
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;
}
static bool read_key(struct fstab_rec const* data_rec, bool create_if_absent, KeyBuffer* key) {
if (!data_rec->key_dir) {
LOG(ERROR) << "Failed to get key_dir";
return false;
}
std::string key_dir = data_rec->key_dir;
auto dir = key_dir + "/key";
LOG(DEBUG) << "key_dir/key: " << key;
if (!fs_mkdirs(dir.c_str(), 0700)) {
PLOG(ERROR) << "Creating directories: " << dir;
}
auto temp = key_dir + "/tmp";
if (!android::vold::retrieveKey(create_if_absent, dir, temp, key)) return false;
return true;
}
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) {
android::base::unique_fd dev_fd(TEMP_FAILURE_RETRY(open(
real_blkdev.c_str(), O_RDONLY | O_CLOEXEC, 0)));
if (dev_fd == -1) {
PLOG(ERROR) << "Unable to open " << real_blkdev << " to measure size";
return false;
}
unsigned long res;
// TODO: should use BLKGETSIZE64
get_blkdev_size(dev_fd.get(), &res);
if (res == 0) {
PLOG(ERROR) << "Unable to measure size of " << real_blkdev;
return false;
}
*nr_sec = res;
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 e4crypt_mount_metadata_encrypted(const std::string& mount_point, bool needs_encrypt) {
LOG(DEBUG) << "e4crypt_mount_metadata_encrypted: " << mount_point << " " << needs_encrypt;
auto encrypted_state = android::base::GetProperty("ro.crypto.state", "");
if (encrypted_state != "") {
LOG(DEBUG) << "e4crypt_enable_crypto got unexpected starting state: " << encrypted_state;
return false;
}
auto data_rec = fs_mgr_get_entry_for_mount_point(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(data_rec->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(const_cast<char*>(crypto_blkdev.c_str()), data_rec->blk_device,
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(DEBUG) << "Mounting metadata-encrypted filesystem:" << mount_point;
mount_via_fs_mgr(data_rec->mount_point, crypto_blkdev.c_str());
return true;
}
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