package
android.os;
/**
*
@hide Only for use within the system server
*/
interface IUuidService {
String getOrCreatePersistentUuid
();
}
package
com.android.server
.os;
import
android.content
.Context;
import
android.os
.IUuidService;
import
android.os
.UuidManager;
import
android.util
.Slog;
import
com.android.internal.os
.UuidPersistStorage;
public class UuidService extends IUuidService
.Stub {
private static final String TAG = "UuidService";
private final Context mContext;
public UuidService
(Context context
) {
mContext = context;
Slog
.i
(TAG, "UuidService started"
);
}
@Override
public String getOrCreatePersistentUuid
() {
mContext
.enforceCallingOrSelfPermission
(
android.Manifest
.permission
.READ_DEVICE_UUID, null
);
return UuidPersistStorage
.getOrCreatePersistentUuid
();
}
}
// frameworks/base/core/java/
android/os/UuidManager
.java
package
android.os;
import
android.annotation
.NonNull;
import
android.annotation
.System
Api;
import
android.os
.IBinder;
import
android.os
.Parcel;
import
android.os
.RemoteException;
import
android.os
.ServiceManager;
import
android.util
.Log;
/**
* Provides access to a persistent unique identifier for the device
.
*
*
@hide This class may be promoted to @System
Api in future
.
*/
@System
Api
public class UuidManager {
private static final String TAG = "UuidManager";
private static final String SERVICE_NAME = "uuid";
// 必须与 IUuidService
.aidl 中的方法顺序一致
private static final int TRANSACTION_getOrCreatePersistentUuid = IBinder
.FIRST_CALL_TRANSACTION + 0;
private final IBinder mBinder;
/**
* Private constructor to prevent direct instantiation
.
* Use getSystemService
(UuidManager
.class
) instead
.
*/
/* package */ UuidManager
() {
mBinder = ServiceManager
.getService
(SERVICE_NAME
);
if
(mBinder == null
) {
Log
.e
(TAG, "Failed to get UUID service from ServiceManager"
);
}
}
/**
* Factory method for creating UuidManager instances
.
* Used by SystemServiceRegistry
.
*
*
@hide
*/
@System
Api(client = System
Api.Client
.SYSTEM_SERVER
)
public static UuidManager create
() {
return new UuidManager
();
}
/**
* Gets or creates a persistent UUID for this device
.
*
* @return the UUID string, never null
* @throws IllegalStateException if service is unavailable
*/
@NonNull
public String getOrCreatePersistentUuid
() {
if
(mBinder == null
) {
throw new IllegalStateException
("UUID service not available"
);
}
Parcel data = Parcel
.obtain
();
Parcel reply = Parcel
.obtain
();
try {
// 必须写入接口标识符（由 AIDL 自动生成）
data
.write
InterfaceToken
("
android.os
.IUuidService"
);
// 发起调用（transaction code 由 AIDL 分配）
mBinder
.transact
(TRANSACTION_getOrCreatePersistentUuid, data, reply, 0
);
// 检查异常
reply
.readException
();
// 读取返回值
String uuid = reply
.readString
();
return uuid != null ? uuid : "unknown";
} catch
(RemoteException e
) {
Log
.e
(TAG, "Remote exception while getting UUID", e
);
throw e
.rethrowFromSystemServer
();
} finally {
data
.recycle
();
reply
.recycle
();
}
}
}
package
com.android.internal.os;
import
android.util
.Log;
import
android.annotation
.NonNull;
import java
.io
.*;
import java
.util
.UUID;
public final class UuidPersistStorage {
private static final String TAG = "UuidPersistStorage";
private static final String UUID_FILE_PATH = "/persist/device_uuid";
private static String sCachedUuid;
private static final Object sLock = new Object
();
public static @NonNull String getOrCreatePersistentUuid
() {
if
(sCachedUuid != null
) {
return sCachedUuid;
}
synchronized
(sLock
) {
if
(sCachedUuid != null
) {
return sCachedUuid;
}
File file = new File
(UUID_FILE_PATH
);
if
(file
.exists
()) {
try
(BufferedReader reader = new BufferedReader
(new FileReader
(file
))) {
String line = reader
.readLine
();
if
(isValidUuid
(line
)) {
sCachedUuid = line
.trim
();
Log
.i
(TAG, "Loaded UUID from " + UUID_FILE_PATH
);
return sCachedUuid;
} else {
Log
.w
(TAG, "Invalid UUID format, regenerating
..."
);
}
} catch
(IOException e
) {
Log
.e
(TAG, "Failed to read UUID file", e
);
}
}
// 生成新 UUID
String newUuid = UUID
.randomUUID
().toString
();
sCachedUuid = newUuid;
// 写入文件
File parentDir = file
.getParentFile
();
if
(parentDir != null && !parentDir
.exists
()) {
parentDir
.mkdirs
();
}
try
(FileWriter writer = new FileWriter
(file
)) {
writer
.write
(newUuid
);
writer
.flush
();
Runtime
.getRuntime
().exec
("chmod 644 " + UUID_FILE_PATH
).waitFor
();
Log
.i
(TAG, "Saved new UUID: " + newUuid
);
} catch
(IOException |
InterruptedException e
) {
Log
.e
(TAG, "Failed to write UUID", e
);
}
}
return sCachedUuid;
}
private static boolean isValidUuid
(String str
) {
if
(str == null || str
.length
() != 36
) return false;
return str
.matches
(
"^[0-9a-fA-F]{8}-[0-9a-fA-F]{4}-[1-5][0-9a-fA-F]{3}-[89abAB][0-9a-fA-F]{3}-[0-9a-fA-F]{12}$"
);
}
}
registerService
(Context
.UUID_SERVICE, UuidManager
.class,
new CachedServiceFetcher<UuidManager>
() {
@Override
public UuidManager createService
(ContextImpl ctx
) {
return UuidManager
.create
(); //通过公共静态方法创建
}
}
);
try {
Slog
.i
(TAG, "Starting UUID Service"
);
UuidService uuidService = new UuidService
(mSystemContext
);
ServiceManager
.addService
(Context
.UUID_SERVICE, uuidService
);
} catch
(Throwable e
) {
reportWtf
("starting UUID Service", e
);
}
<!-- caiwenlu add -->
<permission
android:name="
android.permission
.READ_DEVICE_UUID"
android:protectionLevel="signature|privileged"
android:label="@string/permlab_readDeviceUuid"
android:description="@string/permdesc_readDeviceUuid" />
<!-- caiwenlu add end -->
//caiwenlu add
/**
* Use with {@link #getSystemService
(Class
)} to retrieve a {@link UuidManager}
.
*/
public static final String UUID_SERVICE = "uuid";
//caiwenlu add end
UuidManager uuidManager = getSystemService
(UuidManager
.class
);
if
(uuidManager != null
) {
String uuid = uuidManager
.getOrCreatePersistentUuid
();
Log
.d
("UUID", "Device UUID: " + uuid
);
} else {
Log
.e
("UUID", "UuidManager is null - check if service started"
);
}
本文探讨了Android中两类不可见API：内部API与隐藏API的区别及使用风险，并提供了不借助反射机制调用这些API的方法。
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