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
2020-04-11 20:47:09 -04:00
parent f4c1553789
commit 7ba7500953
60 changed files with 8117 additions and 280 deletions
@@ -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;
+}