Add CodeQL Workflow for Code Security Analysis

[b4yuan]

Summary

This pull request introduces a CodeQL workflow to enhance the security analysis of this repository.

What is CodeQL

CodeQL is a static analysis tool that helps identify and mitigate security vulnerabilities. It is primarily intra-function but does provide some support for inter-function analysis. By integrating CodeQL into a GitHub Actions workflow, it can proactively identify and address potential issues before they become security threats.

For more information on CodeQL and how to interpret its results, refer to the GitHub documentation and the CodeQL documentation (https://codeql.github.com/ and https://codeql.github.com/docs/).

What this PR does

We added a new CodeQL workflow file (.github/workflows/codeql.yml) that

• Runs on every pull request (functionality to run on every push to main branches is included as a comment for convenience).
• Runs daily.
• Excludes queries with a high false positive rate or low-severity findings.
• Does not display results for git submodules, focusing only on our own codebase.

Validation

To validate the functionality of this workflow, we have run several test scans on the codebase and reviewed the results. The workflow successfully compiles the project, identifies issues, and provides actionable insights while reducing noise by excluding certain queries and third-party code.

Using the workflow results

If this pull request is merged, the CodeQL workflow will be automatically run on every push to the main branch and on every pull request to the main branch. To view the results of these code scans, follow these steps:

1. Under the repository name, click on the Security tab.
2. In the left sidebar, click Code scanning alerts.

Is this a good idea?

We are researchers at Purdue University in the USA. We are studying the potential benefits and costs of using CodeQL on open-source repositories of embedded software.

We wrote up a report of our findings so far. The TL;DR is “CodeQL outperforms the other freely-available static analysis tools, with fairly low false positive rates and lots of real defects”. You can read about the report here: https://arxiv.org/abs/2310.00205

Review of engineering hazards

License: see the license at https://github.com/github/codeql-cli-binaries/blob/main/LICENSE.md:

Here's what you may also do with the Software, but only with an Open Source Codebase and subject to the License Restrictions provisions below:

Perform analysis on the Open Source Codebase.

If the Open Source Codebase is hosted and maintained on GitHub.com, generate CodeQL databases for or during automated analysis, CI, or CD.

False positives: We find that around 20% of errors are false positives, but that these FPs are polarized and only a few rules contribute to most FPs. We find that the top rules contributing to FPs are: cpp/uninitialized-local, cpp/missing-check-scanf, cpp/suspicious-pointer-scaling, cpp/unbounded-write, cpp/constant-comparison, and cpp/inconsistent-null-check. Adding a filter to filter out certain rules that contribute to a high FP rate can be done simply in the workflow file.

[b4yuan]

@ozersa Pinging to check in on a possible followup to this PR?

[mathias-arm]

I have reservations about this PR. I would be interested in static analysis tooling that could point out bad code in DAPLink, but with a focus on quality rather than security. DAPLink includes a lot of third-party code we would probably want to exclude that from the analysis.

Would it be possible to see what kind of report is generated for DAPLink.

In terms of implementation, I would rather start with merges on develop (add later main) before extending to pull requests. I don't think daily runs make sense for us. I do not understand why the workflow also builds the project.

[b4yuan]

Thanks for the concerns.

DAPLink includes a lot of third-party code we would probably want to exclude that from the analysis.

Third party code can be filtered out from the analysis, so the wf is only analyzing DAPLink source code.

Would it be possible to see what kind of report is generated for DAPLink.

Yes! Actually, I raised the following that were bugs from a CodeQL analysis during our data collection stage:

• uart.c constant comparison issues #1039
• fix: incorrect not operator #1045
• Address of local variable buffer is assigned to a non-local variable #1046
• Unsigned int comparison to 0 #1051

The output, after uploaded to Code Scanning under the Security tab looks like:

For any of the bugs, you can dismiss them for the following reasons:

I do not understand why the workflow also builds the project.

The workflow builds the project so that CodeQL can analyze the source code. From https://docs.github.com/en/code-security/code-scanning/troubleshooting-code-scanning/no-source-code-seen-during-build: "Since CodeQL observes the activity of the compiler to understand the data flows in a repository, CodeQL requires a complete build to take place in order to perform analysis."