Step 1 - Welcome to the course!

[github-learning-lab]

Welcome to the CodeQL U-Boot Challenge for C/C++

We created this course to help you quickly learn CodeQL, our query language and engine for code analysis. The goal is to find several remote code execution (RCE) vulnerabilities in the open-source software known as U-Boot, using CodeQL and its libraries for analyzing C/C++ code. To find the real vulnerabilities, you'll need to write a sequence of queries, making them more precise at each step of the course.

More detail

The goal is to find a set of 9 remote-code-execution vulnerabilities in the U-Boot boot loader. These vulnerabilities were originally discovered by GitHub Security Lab researchers and have since been fixed. An attacker with positioning on the local network, or control of a malicious NFS server, could potentially achieve remote code execution on the U-Boot powered device. This was possible because the code read data from the network (that could be attacker-controlled) and passed it to the length parameter of a call to the memcpy function. When such a length parameter is not properly validated before use, it may lead to exploitable memory corruption vulnerabilities.

U-Boot contains hundreds of calls to both memcpy and libc functions that read data from the network. You can often recognize network data being acted upon through use of the ntohs (network to host short) and ntohl (network to host long) functions or macros. These swap the byte ordering for integer values that are received in network ordering to the host's native byte ordering (which is architecture dependent).

In this course, you will use CodeQL to find such calls. Many of those calls may actually be safe, so throughout this course you will refine your query to reduce the number of false positives, and finally track down the unsafe calls to memcpy that are influenced by remote input.

Upon completion of the course, you will have created a CodeQL query that is able to find variants of this common vulnerability pattern.

Step 1: Know where to get help

Bookmark these useful documentation links:

• Writing a basic C++ Code QL query
• Introduction to CodeQL
• CodeQL Docs

If you get stuck during this course and need some help, the best place to ask for help is on the GitHub Security Lab Slack. Request an invitation from the Security Lab Get Involved page and ask in the channel #codeql-writing. There are also sample solutions in the course repository, but please try to solve the tasks on your own first!

Hope this is exciting! Please close this issue now, then wait for the next set of instructions to appear in a comment below.

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