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platform_system_vold/KeyStorage.cpp
Eric Biggers 2d30b890d2 KeyStorage: don't request rollback resistance for wrapped storage keys 
Hardware-wrapped inline encryption keys (a.k.a. "wrapped storage keys"
or "TAG_STORAGE_KEY keys") are being generated with rollback resistance
enabled, but are never deleted.  This leaks the space that KeyMint
implementations reserve for rollback-resistant keys, e.g. space in the
RPMB.  This is a problem especially for the per-boot key, as that gets
regenerated every time the device is rebooted.  After enough reboots,
KeyMint runs out of space for rollback-resistant keys.  This stops any
new or upgraded keys from being rollback-resistant, reducing security.

This bug affects all devices that use HW-wrapped inline encryption keys
for FBE (have "wrappedkey_v0" in the options for fileencryption in their
fstab), and whose KeyMint implementations support TAG_STORAGE_KEY in
combination with TAG_ROLLBACK_RESISTANCE.  But it's more of a problem on
devices that are rebooted frequently, as per the above.

Fix this bug by not requesting rollback resistance for HW-wrapped inline
encryption keys.  It was a mistake for these keys to ever be rollback-
resistant, as they are simply a stand-in for raw keys.  Secure deletion
instead has to happen higher up the stack, via the Keystore key that
encrypts these keys being deleted, or via the Keystore key and/or Weaver
slot needed to decrypt the user's synthetic password being deleted.

(It was also a mistake for HW-wrapped inline encryption keys to use
Keystore at all.  The revised design for them that I'm working on for
upstream Linux doesn't use Keystore.  But for now, Android uses Keystore
for them, and the fix is to not request rollback resistance.)

Bug: 240533602
Fixes: 3dfb094cb2 ("vold: Support Storage keys for FBE")
Change-Id: I648a1af9e16787dfcfeefa2b2f2e4a72cac2c6a6
2022-07-28 18:48:46 +00:00

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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 "KeyStorage.h"
#include "Checkpoint.h"
#include "Keystore.h"
#include "Utils.h"
#include <algorithm>
#include <memory>
#include <mutex>
#include <thread>
#include <vector>
#include <errno.h>
#include <stdio.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <openssl/err.h>
#include <openssl/evp.h>
#include <openssl/sha.h>
#include <android-base/file.h>
#include <android-base/logging.h>
#include <android-base/properties.h>
#include <android-base/unique_fd.h>
#include <cutils/properties.h>
namespace android {
namespace vold {
const KeyAuthentication kEmptyAuthentication{""};
static constexpr size_t AES_KEY_BYTES = 32;
static constexpr size_t GCM_NONCE_BYTES = 12;
static constexpr size_t GCM_MAC_BYTES = 16;
static constexpr size_t SECDISCARDABLE_BYTES = 1 << 14;
static const char* kCurrentVersion = "1";
static const char* kRmPath = "/system/bin/rm";
static const char* kSecdiscardPath = "/system/bin/secdiscard";
static const char* kStretch_none = "none";
static const char* kStretch_nopassword = "nopassword";
static const char* kHashPrefix_secdiscardable = "Android secdiscardable SHA512";
static const char* kHashPrefix_keygen = "Android key wrapping key generation SHA512";
static const char* kFn_encrypted_key = "encrypted_key";
static const char* kFn_keymaster_key_blob = "keymaster_key_blob";
static const char* kFn_keymaster_key_blob_upgraded = "keymaster_key_blob_upgraded";
static const char* kFn_secdiscardable = "secdiscardable";
static const char* kFn_stretching = "stretching";
static const char* kFn_version = "version";
namespace {
// Storage binding info for ensuring key encryption keys include a
// platform-provided seed in their derivation.
struct StorageBindingInfo {
enum class State {
UNINITIALIZED,
IN_USE, // key storage keys are bound to seed
NOT_USED, // key storage keys are NOT bound to seed
};
// Binding seed mixed into all key storage keys.
std::vector<uint8_t> seed;
// State tracker for the key storage key binding.
State state = State::UNINITIALIZED;
std::mutex guard;
};
// Never freed as the dtor is non-trivial.
StorageBindingInfo& storage_binding_info = *new StorageBindingInfo;
} // namespace
static bool checkSize(const std::string& kind, size_t actual, size_t expected) {
if (actual != expected) {
LOG(ERROR) << "Wrong number of bytes in " << kind << ", expected " << expected << " got "
<< actual;
return false;
}
return true;
}
static void hashWithPrefix(char const* prefix, const std::string& tohash, std::string* res) {
SHA512_CTX c;
SHA512_Init(&c);
// Personalise the hashing by introducing a fixed prefix.
// Hashing applications should use personalization except when there is a
// specific reason not to; see section 4.11 of https://www.schneier.com/skein1.3.pdf
std::string hashingPrefix = prefix;
hashingPrefix.resize(SHA512_CBLOCK);
SHA512_Update(&c, hashingPrefix.data(), hashingPrefix.size());
SHA512_Update(&c, tohash.data(), tohash.size());
res->assign(SHA512_DIGEST_LENGTH, '\0');
SHA512_Final(reinterpret_cast<uint8_t*>(&(*res)[0]), &c);
}
static bool generateKeyStorageKey(Keystore& keystore, const std::string& appId, std::string* key) {
auto paramBuilder = km::AuthorizationSetBuilder()
.AesEncryptionKey(AES_KEY_BYTES * 8)
.GcmModeMinMacLen(GCM_MAC_BYTES * 8)
.Authorization(km::TAG_APPLICATION_ID, appId)
.Authorization(km::TAG_NO_AUTH_REQUIRED);
LOG(DEBUG) << "Generating \"key storage\" key";
auto paramsWithRollback = paramBuilder;
paramsWithRollback.Authorization(km::TAG_ROLLBACK_RESISTANCE);
if (!keystore.generateKey(paramsWithRollback, key)) {
LOG(WARNING) << "Failed to generate rollback-resistant key. This is expected if keystore "
"doesn't support rollback resistance. Falling back to "
"non-rollback-resistant key.";
if (!keystore.generateKey(paramBuilder, key)) return false;
}
return true;
}
bool generateWrappedStorageKey(KeyBuffer* key) {
Keystore keystore;
if (!keystore) return false;
std::string key_temp;
auto paramBuilder = km::AuthorizationSetBuilder().AesEncryptionKey(AES_KEY_BYTES * 8);
paramBuilder.Authorization(km::TAG_STORAGE_KEY);
if (!keystore.generateKey(paramBuilder, &key_temp)) return false;
*key = KeyBuffer(key_temp.size());
memcpy(reinterpret_cast<void*>(key->data()), key_temp.c_str(), key->size());
return true;
}
bool exportWrappedStorageKey(const KeyBuffer& ksKey, KeyBuffer* key) {
Keystore keystore;
if (!keystore) return false;
std::string key_temp;
if (!keystore.exportKey(ksKey, &key_temp)) return false;
*key = KeyBuffer(key_temp.size());
memcpy(reinterpret_cast<void*>(key->data()), key_temp.c_str(), key->size());
return true;
}
static km::AuthorizationSet beginParams(const std::string& appId) {
return km::AuthorizationSetBuilder()
.GcmModeMacLen(GCM_MAC_BYTES * 8)
.Authorization(km::TAG_APPLICATION_ID, appId);
}
static bool readFileToString(const std::string& filename, std::string* result) {
if (!android::base::ReadFileToString(filename, result)) {
PLOG(ERROR) << "Failed to read from " << filename;
return false;
}
return true;
}
static bool readRandomBytesOrLog(size_t count, std::string* out) {
auto status = ReadRandomBytes(count, *out);
if (status != OK) {
LOG(ERROR) << "Random read failed with status: " << status;
return false;
}
return true;
}
bool createSecdiscardable(const std::string& filename, std::string* hash) {
std::string secdiscardable;
if (!readRandomBytesOrLog(SECDISCARDABLE_BYTES, &secdiscardable)) return false;
if (!writeStringToFile(secdiscardable, filename)) return false;
hashWithPrefix(kHashPrefix_secdiscardable, secdiscardable, hash);
return true;
}
bool readSecdiscardable(const std::string& filename, std::string* hash) {
std::string secdiscardable;
if (!readFileToString(filename, &secdiscardable)) return false;
hashWithPrefix(kHashPrefix_secdiscardable, secdiscardable, hash);
return true;
}
static std::mutex key_upgrade_lock;
// List of key directories that have had their Keystore key upgraded during
// this boot and written to "keymaster_key_blob_upgraded", but replacing the old
// key was delayed due to an active checkpoint. Protected by key_upgrade_lock.
// A directory can be in this list at most once.
static std::vector<std::string> key_dirs_to_commit;
// Replaces |dir|/keymaster_key_blob with |dir|/keymaster_key_blob_upgraded and
// deletes the old key from Keystore.
static bool CommitUpgradedKey(Keystore& keystore, const std::string& dir) {
auto blob_file = dir + "/" + kFn_keymaster_key_blob;
auto upgraded_blob_file = dir + "/" + kFn_keymaster_key_blob_upgraded;
std::string blob;
if (!readFileToString(blob_file, &blob)) return false;
if (rename(upgraded_blob_file.c_str(), blob_file.c_str()) != 0) {
PLOG(ERROR) << "Failed to rename " << upgraded_blob_file << " to " << blob_file;
return false;
}
// Ensure that the rename is persisted before deleting the Keystore key.
if (!FsyncDirectory(dir)) return false;
if (!keystore || !keystore.deleteKey(blob)) {
LOG(WARNING) << "Failed to delete old key " << blob_file
<< " from Keystore; continuing anyway";
// Continue on, but the space in Keystore used by the old key won't be freed.
}
return true;
}
static void DeferredCommitKeys() {
android::base::WaitForProperty("vold.checkpoint_committed", "1");
LOG(INFO) << "Committing upgraded keys";
Keystore keystore;
if (!keystore) {
LOG(ERROR) << "Failed to open Keystore; old keys won't be deleted from Keystore";
// Continue on, but the space in Keystore used by the old keys won't be freed.
}
std::lock_guard<std::mutex> lock(key_upgrade_lock);
for (auto& dir : key_dirs_to_commit) {
LOG(INFO) << "Committing upgraded key " << dir;
CommitUpgradedKey(keystore, dir);
}
key_dirs_to_commit.clear();
}
// Returns true if the Keystore key in |dir| has already been upgraded and is
// pending being committed. Assumes that key_upgrade_lock is held.
static bool IsKeyCommitPending(const std::string& dir) {
for (const auto& dir_to_commit : key_dirs_to_commit) {
if (IsSameFile(dir, dir_to_commit)) return true;
}
return false;
}
// Schedules the upgraded Keystore key in |dir| to be committed later. Assumes
// that key_upgrade_lock is held and that a commit isn't already pending for the
// directory.
static void ScheduleKeyCommit(const std::string& dir) {
if (key_dirs_to_commit.empty()) std::thread(DeferredCommitKeys).detach();
key_dirs_to_commit.push_back(dir);
}
static void CancelPendingKeyCommit(const std::string& dir) {
std::lock_guard<std::mutex> lock(key_upgrade_lock);
for (auto it = key_dirs_to_commit.begin(); it != key_dirs_to_commit.end(); it++) {
if (IsSameFile(*it, dir)) {
LOG(DEBUG) << "Cancelling pending commit of upgraded key " << dir
<< " because it is being destroyed";
key_dirs_to_commit.erase(it);
break;
}
}
}
bool RenameKeyDir(const std::string& old_name, const std::string& new_name) {
std::lock_guard<std::mutex> lock(key_upgrade_lock);
// Find the entry in key_dirs_to_commit (if any) for this directory so that
// we can update it if the rename succeeds. We don't allow duplicates in
// this list, so there can be at most one such entry.
auto it = key_dirs_to_commit.begin();
for (; it != key_dirs_to_commit.end(); it++) {
if (IsSameFile(old_name, *it)) break;
}
if (rename(old_name.c_str(), new_name.c_str()) != 0) {
PLOG(ERROR) << "Failed to rename key directory \"" << old_name << "\" to \"" << new_name
<< "\"";
return false;
}
if (it != key_dirs_to_commit.end()) *it = new_name;
return true;
}
// Deletes a leftover upgraded key, if present. An upgraded key can be left
// over if an update failed, or if we rebooted before committing the key in a
// freak accident. Either way, we can re-upgrade the key if we need to.
static void DeleteUpgradedKey(Keystore& keystore, const std::string& path) {
if (pathExists(path)) {
LOG(DEBUG) << "Deleting leftover upgraded key " << path;
std::string blob;
if (!android::base::ReadFileToString(path, &blob)) {
LOG(WARNING) << "Failed to read leftover upgraded key " << path
<< "; continuing anyway";
} else if (!keystore.deleteKey(blob)) {
LOG(WARNING) << "Failed to delete leftover upgraded key " << path
<< " from Keystore; continuing anyway";
}
if (unlink(path.c_str()) != 0) {
LOG(WARNING) << "Failed to unlink leftover upgraded key " << path
<< "; continuing anyway";
}
}
}
// Begins a Keystore operation using the key stored in |dir|.
static KeystoreOperation BeginKeystoreOp(Keystore& keystore, const std::string& dir,
const km::AuthorizationSet& keyParams,
const km::AuthorizationSet& opParams,
km::AuthorizationSet* outParams) {
km::AuthorizationSet inParams(keyParams);
inParams.append(opParams.begin(), opParams.end());
auto blob_file = dir + "/" + kFn_keymaster_key_blob;
auto upgraded_blob_file = dir + "/" + kFn_keymaster_key_blob_upgraded;
std::lock_guard<std::mutex> lock(key_upgrade_lock);
std::string blob;
bool already_upgraded = IsKeyCommitPending(dir);
if (already_upgraded) {
LOG(DEBUG)
<< blob_file
<< " was already upgraded and is waiting to be committed; using the upgraded blob";
if (!readFileToString(upgraded_blob_file, &blob)) return KeystoreOperation();
} else {
DeleteUpgradedKey(keystore, upgraded_blob_file);
if (!readFileToString(blob_file, &blob)) return KeystoreOperation();
}
auto opHandle = keystore.begin(blob, inParams, outParams);
if (!opHandle) return opHandle;
// If key blob wasn't upgraded, nothing left to do.
if (!opHandle.getUpgradedBlob()) return opHandle;
if (already_upgraded) {
LOG(ERROR) << "Unexpected case; already-upgraded key " << upgraded_blob_file
<< " still requires upgrade";
return KeystoreOperation();
}
LOG(INFO) << "Upgrading key: " << blob_file;
if (!writeStringToFile(*opHandle.getUpgradedBlob(), upgraded_blob_file))
return KeystoreOperation();
if (cp_needsCheckpoint()) {
LOG(INFO) << "Wrote upgraded key to " << upgraded_blob_file
<< "; delaying commit due to checkpoint";
ScheduleKeyCommit(dir);
} else {
if (!CommitUpgradedKey(keystore, dir)) return KeystoreOperation();
LOG(INFO) << "Key upgraded: " << blob_file;
}
return opHandle;
}
static bool encryptWithKeystoreKey(Keystore& keystore, const std::string& dir,
const km::AuthorizationSet& keyParams, const KeyBuffer& message,
std::string* ciphertext) {
km::AuthorizationSet opParams =
km::AuthorizationSetBuilder().Authorization(km::TAG_PURPOSE, km::KeyPurpose::ENCRYPT);
km::AuthorizationSet outParams;
auto opHandle = BeginKeystoreOp(keystore, dir, keyParams, opParams, &outParams);
if (!opHandle) return false;
auto nonceBlob = outParams.GetTagValue(km::TAG_NONCE);
if (!nonceBlob) {
LOG(ERROR) << "GCM encryption but no nonce generated";
return false;
}
// nonceBlob here is just a pointer into existing data, must not be freed
std::string nonce(nonceBlob.value().get().begin(), nonceBlob.value().get().end());
if (!checkSize("nonce", nonce.size(), GCM_NONCE_BYTES)) return false;
std::string body;
if (!opHandle.updateCompletely(message, &body)) return false;
std::string mac;
if (!opHandle.finish(&mac)) return false;
if (!checkSize("mac", mac.size(), GCM_MAC_BYTES)) return false;
*ciphertext = nonce + body + mac;
return true;
}
static bool decryptWithKeystoreKey(Keystore& keystore, const std::string& dir,
const km::AuthorizationSet& keyParams,
const std::string& ciphertext, KeyBuffer* message) {
const std::string nonce = ciphertext.substr(0, GCM_NONCE_BYTES);
auto bodyAndMac = ciphertext.substr(GCM_NONCE_BYTES);
auto opParams = km::AuthorizationSetBuilder()
.Authorization(km::TAG_NONCE, nonce)
.Authorization(km::TAG_PURPOSE, km::KeyPurpose::DECRYPT);
auto opHandle = BeginKeystoreOp(keystore, dir, keyParams, opParams, nullptr);
if (!opHandle) return false;
if (!opHandle.updateCompletely(bodyAndMac, message)) return false;
if (!opHandle.finish(nullptr)) return false;
return true;
}
static std::string getStretching(const KeyAuthentication& auth) {
if (auth.usesKeystore()) {
return kStretch_nopassword;
} else {
return kStretch_none;
}
}
static bool stretchSecret(const std::string& stretching, const std::string& secret,
std::string* stretched) {
if (stretching == kStretch_nopassword) {
if (!secret.empty()) {
LOG(WARNING) << "Password present but stretching is nopassword";
// Continue anyway
}
stretched->clear();
} else if (stretching == kStretch_none) {
*stretched = secret;
} else {
LOG(ERROR) << "Unknown stretching type: " << stretching;
return false;
}
return true;
}
static bool generateAppId(const KeyAuthentication& auth, const std::string& stretching,
const std::string& secdiscardable_hash, std::string* appId) {
std::string stretched;
if (!stretchSecret(stretching, auth.secret, &stretched)) return false;
*appId = secdiscardable_hash + stretched;
const std::lock_guard<std::mutex> scope_lock(storage_binding_info.guard);
switch (storage_binding_info.state) {
case StorageBindingInfo::State::UNINITIALIZED:
storage_binding_info.state = StorageBindingInfo::State::NOT_USED;
break;
case StorageBindingInfo::State::IN_USE:
appId->append(storage_binding_info.seed.begin(), storage_binding_info.seed.end());
break;
case StorageBindingInfo::State::NOT_USED:
// noop
break;
}
return true;
}
static void logOpensslError() {
LOG(ERROR) << "Openssl error: " << ERR_get_error();
}
static bool encryptWithoutKeystore(const std::string& preKey, const KeyBuffer& plaintext,
std::string* ciphertext) {
std::string key;
hashWithPrefix(kHashPrefix_keygen, preKey, &key);
key.resize(AES_KEY_BYTES);
if (!readRandomBytesOrLog(GCM_NONCE_BYTES, ciphertext)) return false;
auto ctx = std::unique_ptr<EVP_CIPHER_CTX, decltype(&::EVP_CIPHER_CTX_free)>(
EVP_CIPHER_CTX_new(), EVP_CIPHER_CTX_free);
if (!ctx) {
logOpensslError();
return false;
}
if (1 != EVP_EncryptInit_ex(ctx.get(), EVP_aes_256_gcm(), NULL,
reinterpret_cast<const uint8_t*>(key.data()),
reinterpret_cast<const uint8_t*>(ciphertext->data()))) {
logOpensslError();
return false;
}
ciphertext->resize(GCM_NONCE_BYTES + plaintext.size() + GCM_MAC_BYTES);
int outlen;
if (1 != EVP_EncryptUpdate(
ctx.get(), reinterpret_cast<uint8_t*>(&(*ciphertext)[0] + GCM_NONCE_BYTES),
&outlen, reinterpret_cast<const uint8_t*>(plaintext.data()), plaintext.size())) {
logOpensslError();
return false;
}
if (outlen != static_cast<int>(plaintext.size())) {
LOG(ERROR) << "GCM ciphertext length should be " << plaintext.size() << " was " << outlen;
return false;
}
if (1 != EVP_EncryptFinal_ex(
ctx.get(),
reinterpret_cast<uint8_t*>(&(*ciphertext)[0] + GCM_NONCE_BYTES + plaintext.size()),
&outlen)) {
logOpensslError();
return false;
}
if (outlen != 0) {
LOG(ERROR) << "GCM EncryptFinal should be 0, was " << outlen;
return false;
}
if (1 != EVP_CIPHER_CTX_ctrl(ctx.get(), EVP_CTRL_GCM_GET_TAG, GCM_MAC_BYTES,
reinterpret_cast<uint8_t*>(&(*ciphertext)[0] + GCM_NONCE_BYTES +
plaintext.size()))) {
logOpensslError();
return false;
}
return true;
}
static bool decryptWithoutKeystore(const std::string& preKey, const std::string& ciphertext,
KeyBuffer* plaintext) {
if (ciphertext.size() < GCM_NONCE_BYTES + GCM_MAC_BYTES) {
LOG(ERROR) << "GCM ciphertext too small: " << ciphertext.size();
return false;
}
std::string key;
hashWithPrefix(kHashPrefix_keygen, preKey, &key);
key.resize(AES_KEY_BYTES);
auto ctx = std::unique_ptr<EVP_CIPHER_CTX, decltype(&::EVP_CIPHER_CTX_free)>(
EVP_CIPHER_CTX_new(), EVP_CIPHER_CTX_free);
if (!ctx) {
logOpensslError();
return false;
}
if (1 != EVP_DecryptInit_ex(ctx.get(), EVP_aes_256_gcm(), NULL,
reinterpret_cast<const uint8_t*>(key.data()),
reinterpret_cast<const uint8_t*>(ciphertext.data()))) {
logOpensslError();
return false;
}
*plaintext = KeyBuffer(ciphertext.size() - GCM_NONCE_BYTES - GCM_MAC_BYTES);
int outlen;
if (1 != EVP_DecryptUpdate(ctx.get(), reinterpret_cast<uint8_t*>(&(*plaintext)[0]), &outlen,
reinterpret_cast<const uint8_t*>(ciphertext.data() + GCM_NONCE_BYTES),
plaintext->size())) {
logOpensslError();
return false;
}
if (outlen != static_cast<int>(plaintext->size())) {
LOG(ERROR) << "GCM plaintext length should be " << plaintext->size() << " was " << outlen;
return false;
}
if (1 != EVP_CIPHER_CTX_ctrl(ctx.get(), EVP_CTRL_GCM_SET_TAG, GCM_MAC_BYTES,
const_cast<void*>(reinterpret_cast<const void*>(
ciphertext.data() + GCM_NONCE_BYTES + plaintext->size())))) {
logOpensslError();
return false;
}
if (1 != EVP_DecryptFinal_ex(ctx.get(),
reinterpret_cast<uint8_t*>(&(*plaintext)[0] + plaintext->size()),
&outlen)) {
logOpensslError();
return false;
}
if (outlen != 0) {
LOG(ERROR) << "GCM EncryptFinal should be 0, was " << outlen;
return false;
}
return true;
}
// Creates a directory at the given path |dir| and stores |key| in it, in such a
// way that it can only be retrieved via Keystore (if no secret is given in
// |auth|) or with the given secret (if a secret is given in |auth|), and can be
// securely deleted. If a storage binding seed has been set, then the storage
// binding seed will be required to retrieve the key as well.
static bool storeKey(const std::string& dir, const KeyAuthentication& auth, const KeyBuffer& key) {
if (TEMP_FAILURE_RETRY(mkdir(dir.c_str(), 0700)) == -1) {
PLOG(ERROR) << "key mkdir " << dir;
return false;
}
if (!writeStringToFile(kCurrentVersion, dir + "/" + kFn_version)) return false;
std::string secdiscardable_hash;
if (!createSecdiscardable(dir + "/" + kFn_secdiscardable, &secdiscardable_hash)) return false;
std::string stretching = getStretching(auth);
if (!writeStringToFile(stretching, dir + "/" + kFn_stretching)) return false;
std::string appId;
if (!generateAppId(auth, stretching, secdiscardable_hash, &appId)) return false;
std::string encryptedKey;
if (auth.usesKeystore()) {
Keystore keystore;
if (!keystore) return false;
std::string ksKey;
if (!generateKeyStorageKey(keystore, appId, &ksKey)) return false;
if (!writeStringToFile(ksKey, dir + "/" + kFn_keymaster_key_blob)) return false;
km::AuthorizationSet keyParams = beginParams(appId);
if (!encryptWithKeystoreKey(keystore, dir, keyParams, key, &encryptedKey)) {
LOG(ERROR) << "encryptWithKeystoreKey failed";
return false;
}
} else {
if (!encryptWithoutKeystore(appId, key, &encryptedKey)) {
LOG(ERROR) << "encryptWithoutKeystore failed";
return false;
}
}
if (!writeStringToFile(encryptedKey, dir + "/" + kFn_encrypted_key)) return false;
if (!FsyncDirectory(dir)) return false;
return true;
}
bool storeKeyAtomically(const std::string& key_path, const std::string& tmp_path,
const KeyAuthentication& auth, const KeyBuffer& key) {
if (pathExists(key_path)) {
LOG(ERROR) << "Already exists, cannot create key at: " << key_path;
return false;
}
if (pathExists(tmp_path)) {
LOG(DEBUG) << "Already exists, destroying: " << tmp_path;
destroyKey(tmp_path); // May be partially created so ignore errors
}
if (!storeKey(tmp_path, auth, key)) return false;
if (!RenameKeyDir(tmp_path, key_path)) return false;
if (!FsyncParentDirectory(key_path)) return false;
LOG(DEBUG) << "Created key: " << key_path;
return true;
}
bool retrieveKey(const std::string& dir, const KeyAuthentication& auth, KeyBuffer* key) {
std::string version;
if (!readFileToString(dir + "/" + kFn_version, &version)) return false;
if (version != kCurrentVersion) {
LOG(ERROR) << "Version mismatch, expected " << kCurrentVersion << " got " << version;
return false;
}
std::string secdiscardable_hash;
if (!readSecdiscardable(dir + "/" + kFn_secdiscardable, &secdiscardable_hash)) return false;
std::string stretching;
if (!readFileToString(dir + "/" + kFn_stretching, &stretching)) return false;
std::string appId;
if (!generateAppId(auth, stretching, secdiscardable_hash, &appId)) return false;
std::string encryptedMessage;
if (!readFileToString(dir + "/" + kFn_encrypted_key, &encryptedMessage)) return false;
if (auth.usesKeystore()) {
Keystore keystore;
if (!keystore) return false;
km::AuthorizationSet keyParams = beginParams(appId);
if (!decryptWithKeystoreKey(keystore, dir, keyParams, encryptedMessage, key)) {
LOG(ERROR) << "decryptWithKeystoreKey failed";
return false;
}
} else {
if (!decryptWithoutKeystore(appId, encryptedMessage, key)) {
LOG(ERROR) << "decryptWithoutKeystore failed";
return false;
}
}
return true;
}
static bool DeleteKeystoreKey(const std::string& blob_file) {
std::string blob;
if (!readFileToString(blob_file, &blob)) return false;
Keystore keystore;
if (!keystore) return false;
LOG(DEBUG) << "Deleting key " << blob_file << " from Keystore";
if (!keystore.deleteKey(blob)) return false;
return true;
}
bool runSecdiscardSingle(const std::string& file) {
if (ForkExecvp(std::vector<std::string>{kSecdiscardPath, "--", file}) != 0) {
LOG(ERROR) << "secdiscard failed";
return false;
}
return true;
}
static bool recursiveDeleteKey(const std::string& dir) {
if (ForkExecvp(std::vector<std::string>{kRmPath, "-rf", dir}) != 0) {
LOG(ERROR) << "recursive delete failed";
return false;
}
return true;
}
bool destroyKey(const std::string& dir) {
bool success = true;
CancelPendingKeyCommit(dir);
auto secdiscard_cmd = std::vector<std::string>{
kSecdiscardPath,
"--",
dir + "/" + kFn_encrypted_key,
dir + "/" + kFn_secdiscardable,
};
// Try each thing, even if previous things failed.
for (auto& fn : {kFn_keymaster_key_blob, kFn_keymaster_key_blob_upgraded}) {
auto blob_file = dir + "/" + fn;
if (pathExists(blob_file)) {
success &= DeleteKeystoreKey(blob_file);
secdiscard_cmd.push_back(blob_file);
}
}
if (ForkExecvp(secdiscard_cmd) != 0) {
LOG(ERROR) << "secdiscard failed";
success = false;
}
success &= recursiveDeleteKey(dir);
return success;
}
bool setKeyStorageBindingSeed(const std::vector<uint8_t>& seed) {
const std::lock_guard<std::mutex> scope_lock(storage_binding_info.guard);
switch (storage_binding_info.state) {
case StorageBindingInfo::State::UNINITIALIZED:
storage_binding_info.state = StorageBindingInfo::State::IN_USE;
storage_binding_info.seed = seed;
android::base::SetProperty("vold.storage_seed_bound", "1");
return true;
case StorageBindingInfo::State::IN_USE:
LOG(ERROR) << "key storage binding seed already set";
return false;
case StorageBindingInfo::State::NOT_USED:
LOG(ERROR) << "key storage already in use without binding";
return false;
}
return false;
}
} // namespace vold
} // namespace android
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