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[翻译]Windows内核漏洞利用教程5：空指针引用
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发表于: 2018-1-22 11:25
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原文地址：https://rootkits.xyz/blog/2018/01/kernel-null-pointer-dereference/
该系列已翻译文章
在这个系列中，在上一篇详细的文章之后，本文将分析一个理解起来相对简单的漏洞类型。空指针引用漏洞，当一个指针的值为空时，却被调用指向某一块内存地址时，就产生了空指针引用漏洞。显然，问题很清楚，如果我们可以控制NULL page，并且在那里写入东西，我们就可能得到代码执行权限。你可能已经猜到，我们将使用和上一篇文章一样的方法去申请NULL page，布局我们的shellcode。所以这一片文章中的很多信息将依赖上一篇文章。
再次感谢hacksysteam提供的驱动程序。
看一下
NullPointerDereference.c
文件。
NTSTATUS TriggerNullPointerDereference(IN PVOID UserBuffer) {
ULONG UserValue = 0;
ULONG MagicValue = 0xBAD0B0B0;
NTSTATUS Status = STATUS_SUCCESS;
PNULL_POINTER_DEREFERENCE NullPointerDereference = NULL;
PAGED_CODE();
__try {
// 检查buffer是否属于用户态
ProbeForRead(UserBuffer,
sizeof(NULL_POINTER_DEREFERENCE),
(ULONG)__alignof(NULL_POINTER_DEREFERENCE));
// 申请pool 块
NullPointerDereference = (PNULL_POINTER_DEREFERENCE)
ExAllocatePoolWithTag(NonPagedPool,
sizeof(NULL_POINTER_DEREFERENCE),
(ULONG)POOL_TAG);
if (!NullPointerDereference) {
// 申请失败
DbgPrint("[-] Unable to allocate Pool chunk\n");
Status = STATUS_NO_MEMORY;
return Status;
}
else {
DbgPrint("[+] Pool Tag: %s\n", STRINGIFY(POOL_TAG));
DbgPrint("[+] Pool Type: %s\n", STRINGIFY(NonPagedPool));
DbgPrint("[+] Pool Size: 0x%X\n", sizeof(NULL_POINTER_DEREFERENCE));
DbgPrint("[+] Pool Chunk: 0x%p\n", NullPointerDereference);
}
// 获取用户态传进来的值
UserValue = *(PULONG)UserBuffer;
DbgPrint("[+] UserValue: 0x%p\n", UserValue);
DbgPrint("[+] NullPointerDereference: 0x%p\n", NullPointerDereference);
//检查magic值
if (UserValue == MagicValue) {
NullPointerDereference->Value = UserValue;
NullPointerDereference->Callback = &NullPointerDereferenceObjectCallback;
DbgPrint("[+] NullPointerDereference->Value: 0x%p\n", NullPointerDereference->Value);
DbgPrint("[+] NullPointerDereference->Callback: 0x%p\n", NullPointerDereference->Callback);
}
else {
DbgPrint("[+] Freeing NullPointerDereference Object\n");
DbgPrint("[+] Pool Tag: %s\n", STRINGIFY(POOL_TAG));
DbgPrint("[+] Pool Chunk: 0x%p\n", NullPointerDereference);
// 释放申请的pool块
ExFreePoolWithTag((PVOID)NullPointerDereference, (ULONG)POOL_TAG);
// 设置指针为空
NullPointerDereference = NULL;
}
#ifdef SECURE
// 安全代码：在调用回调函数之前，检查指针是否为空
if (NullPointerDereference) {
NullPointerDereference->Callback();
}
#else
DbgPrint("[+] Triggering Null Pointer Dereference\n");
// 不安全代码：在调用回调函数之前，没有检查指针是否为空
NullPointerDereference->Callback();
#endifNTSTATUS TriggerNullPointerDereference(IN PVOID UserBuffer) {
ULONG UserValue = 0;
ULONG MagicValue = 0xBAD0B0B0;
NTSTATUS Status = STATUS_SUCCESS;
PNULL_POINTER_DEREFERENCE NullPointerDereference = NULL;
PAGED_CODE();
__try {
// 检查buffer是否属于用户态
ProbeForRead(UserBuffer,
sizeof(NULL_POINTER_DEREFERENCE),
(ULONG)__alignof(NULL_POINTER_DEREFERENCE));
// 申请pool 块
NullPointerDereference = (PNULL_POINTER_DEREFERENCE)
ExAllocatePoolWithTag(NonPagedPool,
sizeof(NULL_POINTER_DEREFERENCE),
(ULONG)POOL_TAG);
if (!NullPointerDereference) {
// 申请失败
DbgPrint("[-] Unable to allocate Pool chunk\n");
Status = STATUS_NO_MEMORY;
return Status;
}
else {
DbgPrint("[+] Pool Tag: %s\n", STRINGIFY(POOL_TAG));
DbgPrint("[+] Pool Type: %s\n", STRINGIFY(NonPagedPool));
DbgPrint("[+] Pool Size: 0x%X\n", sizeof(NULL_POINTER_DEREFERENCE));
DbgPrint("[+] Pool Chunk: 0x%p\n", NullPointerDereference);
}
// 获取用户态传进来的值
UserValue = *(PULONG)UserBuffer;
DbgPrint("[+] UserValue: 0x%p\n", UserValue);
DbgPrint("[+] NullPointerDereference: 0x%p\n", NullPointerDereference);
//检查magic值
if (UserValue == MagicValue) {
NullPointerDereference->Value = UserValue;
NullPointerDereference->Callback = &NullPointerDereferenceObjectCallback;
DbgPrint("[+] NullPointerDereference->Value: 0x%p\n", NullPointerDereference->Value);
DbgPrint("[+] NullPointerDereference->Callback: 0x%p\n", NullPointerDereference->Callback);
}
else {
DbgPrint("[+] Freeing NullPointerDereference Object\n");
DbgPrint("[+] Pool Tag: %s\n", STRINGIFY(POOL_TAG));
DbgPrint("[+] Pool Chunk: 0x%p\n", NullPointerDereference);
// 释放申请的pool块
ExFreePoolWithTag((PVOID)NullPointerDereference, (ULONG)POOL_TAG);
// 设置指针为空
NullPointerDereference = NULL;
}
#ifdef SECURE
// 安全代码：在调用回调函数之前，检查指针是否为空
if (NullPointerDereference) {
NullPointerDereference->Callback();
}
#else
DbgPrint("[+] Triggering Null Pointer Dereference\n");
// 不安全代码：在调用回调函数之前，没有检查指针是否为空
NullPointerDereference->Callback();
#endif在代码中，用magic值（0xBAD0B0B0）和用户态的值相比较，如果不相同，NullPointerDereference指针被设置为空。我们可以看到，在安全的代码中，检查了NullPointerDereference指针是否为空。
从IDA简单分析可以看出，非分页pool的Tag 为“Hack”，magic值，以及偏移0x4，我们要写入shellcode的地方。
这次要使用的IOCTL值为0x22202b.
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，未初始化的堆变量
