linux-rootkits
A collection of Linux kernel rootkits found across the internet taken and put together, with a short report on how they work. The README's in each folder contain the report about the rootkit sample.
Table of Contents
Rootkits
| Name | Short Description | link to orignal repo |
|---|---|---|
| Puszek | rootkit which can log requests and prevent itself from being rmmod'd | Eternal's repo |
| Reptile | A highly configurable and sophisticated rootkit which can give root privs to users and a backdoor | f0rb1dd3n's repo |
| Khook | (Not a rootkit) but an engine that can be used to hook functions, also mentioned here since it's used by rootkits to hook functions | milabs's repo |
| rkduck | A rootkit which can hide files and record key strokes, also is configurable after installation | QuokkaLight's repo |
If you plan to download the latest version of these rootkits please download them from their original repo, as it would be the latest version.
Features Descriptions
| Name | Short Description | Rootkits | links to code samples |
|---|---|---|---|
| Finding Syscall Table address (1) | Search memory for the pointer table! using a address of syscall function (eg. close) as reference | Puszek and rkduck | In Puszek and in rkduck |
| Function Hooking (1) | Get the address of the function to be hooked and then Modify CR0 to remove write protect bit and then add a jump instruction to a stub | Khook and Reptile (uses Khook) | in Khook and detailed explanation |
| Function Hooking (2) | Get the address of the function to be hooked and then map the page as readable and replace it with a jumo to the new function | rkduck | in rkduck |
| Syscall Table Hooking (1) | Modify CR0 to remove write protect bit and change syscall table | Puszek | In Puszek |
| Syscall Table Hooking (2) | Get the page where the Syscall table is mapped, and set that page as writeable and then modify it | Puszek | In Puszek |
| Syscall Table Hooking (3) | Hook the syscall functions by using the Function Hooking(1) Technique | Reptile (uses Khook) | In Reptile |
| Hide Rootkit | Hook open syscall and modify the contents of the files (/proc/modules) which contain the name of the rooktit | Puszek | In Puszek |
| Interactive Control | Implementing an IOCTL which manages the features of the rootkit and allows the user to send it commands | Reptile | In Reptile |
| Unable to rmmod module | Hook open syscall and make it not possible to open the rootkit module | Puszek | In Puszek |
| Hide Process (1) | Hook kernel functions copy_creds and exit_creds to add/remove a flag on the task_struct for a process being invisible. Hook next_tgid function which is responsible for the /proc/PID entries and make the process invisible. |
Reptile | Reptile - next_tgid and cred functions |
| Backdoor Access | Hook ip_recv function in the kernel and parse the packets for a specific string in the payload section |
Reptile | In Reptile |
| Hide Files (1) | Hook new_sys_getdents and new_sys_getdents64 syscalls and modify it's result to hide files matching a specified prefix |
Puszek | In Puszek |
| Hide Files (2) | Hook kernel functions filldir and co to remove files with a specified prefix |
Reptile | in Reptile |
| File Content Tampering (1) | Hook kernel function vfs_read where all data between specific tags will be removed before sending back to the user |
Reptile | In Reptile |
| Intercept Http Requests and Leak Data (1) | Hook send_to syscall and the tcp data sent is checked for presence of headers. This is then searchd for presence of passwords etc |
Puszek | In Puszek |
| Hide Network Connections | Hide TCP and UDP connections by hooking into the functions tcp4_seq_show and udp4_seq_show filtering based on the IP |
Reptile | In Reptile |
| Avoiding kernel auditing | Hook the audit_alloc function in the kernel and clear the TIF_SYSCALL_AUDIT flag which defines wherter the process is audited |
Reptile | In Reptile |
Test Environment
All rootkits are tested in a fresh Ubuntu 16.04 VM where uname -a returns Linux r3x-VirtualBox 4.15.0-112-generic #113~16.04.1-Ubuntu SMP Fri Jul 10 04:37:08 UTC 2020 x86_64 x86_64 x86_64 GNU/Linux
Disclaimer
The rootkits were written by their respective authors and the code belongs to them. This is just an attempt to preserve rootkits with a report on how they work and the OS they were tested on.
If your rootkit is present here and you wish it to be removed please contact me at siddharth.muralee[AT]gmail[DOT]com
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