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// Copyright 2021 Code Intelligence GmbH
//
// 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.
package com.code_intelligence.jazzer.sanitizers
import com.code_intelligence.jazzer.api.HookType
import com.code_intelligence.jazzer.api.MethodHook
import com.code_intelligence.jazzer.api.MethodHooks
import java.io.BufferedInputStream
import java.io.ByteArrayOutputStream
import java.io.InputStream
import java.io.ObjectInputStream
import java.io.ObjectOutputStream
import java.io.ObjectStreamConstants
import java.lang.invoke.MethodHandle
import java.util.WeakHashMap
/**
* Detects unsafe deserialization that leads to attacker-controlled method calls, in particular to [Object.finalize].
*/
@Suppress("unused_parameter")
object Deserialization {
private val OBJECT_INPUT_STREAM_HEADER =
ObjectStreamConstants.STREAM_MAGIC.toBytes() + ObjectStreamConstants.STREAM_VERSION.toBytes()
/**
* Used to memoize the [InputStream] used to construct a given [ObjectInputStream].
* [ThreadLocal] is required because the map is not synchronized (and likely cheaper than
* synchronization).
* [WeakHashMap] ensures that we don't prevent the GC from cleaning up [ObjectInputStream] from
* previous fuzzing runs.
*
* Note: The [InputStream] values can all be assumed to be markable, i.e., their
* [InputStream.markSupported] returns true.
*/
private var inputStreamForObjectInputStream: ThreadLocal<WeakHashMap<ObjectInputStream, InputStream>> =
ThreadLocal.withInitial {
WeakHashMap<ObjectInputStream, InputStream>()
}
/**
* A serialized instance of our honeypot class.
*/
private val SERIALIZED_JAZ_ZER_INSTANCE: ByteArray by lazy {
// We can't instantiate jaz.Zer directly, so we instantiate and serialize jaz.Ter and then
// patch the class name.
val baos = ByteArrayOutputStream()
ObjectOutputStream(baos).writeObject(jaz.Ter())
val serializedJazTerInstance = baos.toByteArray()
val posToPatch = serializedJazTerInstance.indexOf("jaz.Ter".toByteArray())
serializedJazTerInstance[posToPatch + "jaz.".length] = 'Z'.code.toByte()
serializedJazTerInstance
}
/**
* Guides the fuzzer towards producing a valid header for an ObjectInputStream.
*/
@MethodHook(
type = HookType.BEFORE,
targetClassName = "java.io.ObjectInputStream",
targetMethod = "<init>",
targetMethodDescriptor = "(Ljava/io/InputStream;)V"
)
@JvmStatic
fun objectInputStreamInitBeforeHook(method: MethodHandle?, alwaysNull: Any?, args: Array<Any?>, hookId: Int) {
val originalInputStream = args[0] as? InputStream ?: return
val fixedInputStream = if (originalInputStream.markSupported())
originalInputStream
else
BufferedInputStream(originalInputStream)
args[0] = fixedInputStream
guideMarkableInputStreamTowardsEquality(fixedInputStream, OBJECT_INPUT_STREAM_HEADER, hookId)
}
/**
* Memoizes the input stream used for creating the [ObjectInputStream] instance.
*/
@MethodHook(
type = HookType.AFTER,
targetClassName = "java.io.ObjectInputStream",
targetMethod = "<init>",
targetMethodDescriptor = "(Ljava/io/InputStream;)V"
)
@JvmStatic
fun objectInputStreamInitAfterHook(
method: MethodHandle?,
objectInputStream: ObjectInputStream?,
args: Array<Any?>,
hookId: Int,
alwaysNull: Any?,
) {
val inputStream = args[0] as? InputStream
check(inputStream?.markSupported() == true) {
"ObjectInputStream#<init> AFTER hook reached with null or non-markable input stream"
}
inputStreamForObjectInputStream.get()[objectInputStream] = inputStream
}
/**
* Guides the fuzzer towards producing a valid serialized instance of our honeypot class.
*/
@MethodHooks(
MethodHook(
type = HookType.BEFORE,
targetClassName = "java.io.ObjectInputStream",
targetMethod = "readObject"
),
MethodHook(
type = HookType.BEFORE,
targetClassName = "java.io.ObjectInputStream",
targetMethod = "readObjectOverride"
),
MethodHook(
type = HookType.BEFORE,
targetClassName = "java.io.ObjectInputStream",
targetMethod = "readUnshared"
),
)
@JvmStatic
fun readObjectBeforeHook(
method: MethodHandle?,
objectInputStream: ObjectInputStream?,
args: Array<Any?>,
hookId: Int,
) {
val inputStream = inputStreamForObjectInputStream.get()[objectInputStream]
if (inputStream?.markSupported() != true) return
guideMarkableInputStreamTowardsEquality(inputStream, SERIALIZED_JAZ_ZER_INSTANCE, hookId)
}
/**
* Calls [Object.finalize] early if the returned object is [jaz.Zer]. A call to finalize is
* guaranteed to happen at some point, but calling it early means that we can accurately report
* the input that lead to its execution.
*/
@MethodHooks(
MethodHook(type = HookType.AFTER, targetClassName = "java.io.ObjectInputStream", targetMethod = "readObject"),
MethodHook(type = HookType.AFTER, targetClassName = "java.io.ObjectInputStream", targetMethod = "readObjectOverride"),
MethodHook(type = HookType.AFTER, targetClassName = "java.io.ObjectInputStream", targetMethod = "readUnshared"),
)
@JvmStatic
fun readObjectAfterHook(
method: MethodHandle?,
objectInputStream: ObjectInputStream?,
args: Array<Any?>,
hookId: Int,
deserializedObject: Any?,
) {
if (deserializedObject?.javaClass?.name == HONEYPOT_CLASS_NAME) {
deserializedObject.javaClass.getDeclaredMethod("finalize").run {
isAccessible = true
invoke(deserializedObject)
}
}
}
}
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