xzbot - notes, honeypot, and exploit demo for the xz backd

项目说明

xzbot

Exploration of the xz backdoor (C).
Includes the following:
* honeypot: fake 服务端 to detect exploit attempts
* ed448 patch: patch liblzma.so to use our own ED448 public key
* backdoor format: format of the backdoor payload
* backdoor demo: cli to trigger the RCE assuming knowledge of the ED448 private key

!xzbot demo

honeypot

See openssh.patch for a simple patch to openssh that logs any
connection attempt with a public key N matching the backdoor format.

Any connection attempt will appear as follows in sshd logs:

ed448 patch

The backdoor uses a hardcoded ED448 public key for signature and
decrypting the payload. If we replace this key with our own, we can trigger
the backdoor.

The attacker's ED448 key is:

We will replace this key with our own (generated with seed=0):

To start, download a backdoored libxzma shared object, e.g.
from
Then run the patch script. See assets/ for examples.

Then run sshd using this modified liblzma.so.5.6.1.patch shared object.

backdoor format

The backdoor can be triggered by connecting with an SSH certificate with a
payload in the CA signing key N value. This payload must be encrypted and
signed with the attacker's ED448 key.

The structure has the following format:

A request type is derived from the three above (a * b + c).
If this value is greater than 3, the backdoor skips processing.

* Type 1: unknown, expects zero bytes
* Type 2: executes null-terminated payload with system()
* Type 3: unknown, expects 48 bytes (signed)

The ciphertext is encrypted with chacha20 using the first 32 bytes of the
ED448 public key as a symmetric key. As a result, we can decrypt any
exploit attempt using the following key:

The ciphertext has the following format:

Setting either x or y leads to slightly different code paths.

The signature is an RFC-8032 ED448 signature computed over the following :
* The 32-bit magic value (e.g. 02 00 00 00)
* The 5 bytes of fields before command
* [optional] length bytes of the command
* The first 32 bytes of the sha256 hash of the 服务端's hostkey

backdoor demo

The following will connect to a SSH 服务端 at 127.0.0.1:2222 and
run the command id > /tmp/.xz:

On the 服务端, we can set a watchpoint for the call to system()
and observe the command is executed:

The process tree after exploitation looks different from a normal sshd
process tree:

*Note: successful exploitation does not generate any INFO or higher log entries.*

References

项目信息

开发语言：Go

Star 数：3550

技术要点

该项目属于黑客技术方向的开源资源，代码结构清晰，适合安全研究人员学习参考。项目围绕notes, honeypot, and exploit demo for the xz backdoor (C)展开，提供了可运行的实现，对理解相关安全机制、工具原理与攻防技术具有较高的研究价值。

从技术实现角度看，此类项目的核心在于对底层原理的深入理解与工程化落地。开发者在研究过程中可以结合官方文档与社区讨论，梳理项目的初始化流程、核心模块职责与数据流转，逐步掌握其中的技术细节与设计思路。

使用与学习建议

1. 下载源码压缩包，解压到本地环境。

2. 根据项目类型准备对应的运行环境与依赖。

3. 按照 README 中的步骤完成配置与部署。

4. 在隔离的测试环境中运行验证，避免影响生产系统。

免责声明

本资源来源于开源社区，仅供安全研究、技术学习与合法授权范围内的攻防演练使用，请勿用于任何非法或侵害他人权益的用途。使用本项目产生的一切后果由使用者自行承担。