PageTableInjection: Code Injection, Inject malicious payload

PageTableInjection

Code Injection, Inject malicious payload via pagetables pml4.

Introduction

This is just a proof-of-concept of the page table injection technique to inject malicious code into the arbitrary user processes.
On Windows(and some modern OSes), every process has a its PML4 a.k.a Directory Table Base. Thus the process A cannot access process B without APIs. but how about if we can inject arbitrary PML4 entry? of course, the PML4 entry will point to the corresponding physical address of entries, PDP, PD, and PT as exactly the same as the backing process.

In order to inject malicious PML4 entry to the target process, we need to have an actual resident page (physical memory) that backing the malicious PML4 entry. Thus literally the resident page must be a resident, otherwise, the system will crash or would become unstable, because, during the MMU translating to the physical address, there is nothing that MMU expects, as well as there is nothing the windows memory manager has nothing expects.

Let’s look at the both backing process and target process buffers. In this case, the buffers are:

• Backing Process VA: 0x1A45F810000
• Deployment Process Injected VA: 0x6EA45F810000

Before step to the next, some of you may think that the 2nd address(0x6EA45F810000) looks weird like usually, we allocated buffer via malloc or VirtualAlloc, the virtual address should look like 0x17C7CAC0000 0x23BE9D80000 0x19FE76F0000 or some sort of these. it’s because the malicious PML4 entry is not involved to the memory manager of windows, and is not managed as well. of course every virtual address on Windows 64-bit process could possibly have any value within a range of user memory range.

So if we look into both addresses…

0: kd> .process ffff9803d8037080

Implicit process is now ffff9803`d8037080

0: kd> db 0x6EA45F810000 l2

00006ea4`5f810000  4d 5a       MZ



0: kd> !vtop 7968b000 0x6EA45F810000

Amd64VtoP: Virt 00006ea45f810000, pagedir 000000007968b000

Amd64VtoP: PML4E 000000007968b6e8

Amd64VtoP: PDPE 000000005849b488

Amd64VtoP: PDE 0000000059e9c7e0

Amd64VtoP: PTE 000000003251d080

Amd64VtoP: Mapped phys 0000000014306000

Virtual address 6ea45f810000 translates to physical address 14306000.

0: kd> .process ffff9803d9f6b080

Implicit process is now ffff9803`d9f6b080

0: kd> db 0x1A45F810000 l2

000001a4`5f810000  4d 5a       MZ



0: kd> !vtop 564f6000 0x1A45F810000

Amd64VtoP: Virt 000001a45f810000, pagedir 00000000564f6000

Amd64VtoP: PML4E 00000000564f6018

Amd64VtoP: PDPE 000000005849b488

Amd64VtoP: PDE 0000000059e9c7e0

Amd64VtoP: PTE 000000003251d080

Amd64VtoP: Mapped phys 0000000014306000

Virtual address 1a45f810000 translates to physical address 14306000.

Both addresses are corresponding to the exact same page table entries, PDP, PD, PT, and a physical address. Therefore if we modified the backing process’s buffer, the change also on the target process. This is very similar to the shared memory on Windows, but the difference is that the memory region on the target process will never be shown in any VAD entries of its process. but in another hand, if the backing process’s buffer is freed, it means also the target process but without cleaning the target process’s page table entries, which means that the memory manager will cause a bugcheck MEMORY_MANAGEMENT, or will trigger a worse triple fault on the CPU.

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Copyright (c) 2021 Kento Oki