via fix verifier: add body hash to auth payload to prevent replay attack

[romanornr]

What ❔

Include the SHA-256 hash of request body in the signed authentication payload to make every request cryptographically unique

Why ❔

Right now verifier signs

{
  "timestamp": "1703800000",
  "verifier_index": "2",
  "sequencer_version": "0.1.0"
}

but needs a body hash to see if a valid signature hasn't been messed with
Signature only covers timestamp, index, and version while the body is not part of the signed data

Probably not likely to cause trouble but it migth

Checklist

• PR title corresponds to the body of PR (we generate changelog entries from PRs).
• Tests for the changes have been added / updated.
• Documentation comments have been added / updated.
• Code has been formatted via zkstack dev fmt and zkstack dev lint.

[gemini-code-assist]

Summary of Changes

Hello @romanornr, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request significantly bolsters the security posture of the verifier coordinator's API by introducing a body hash into the authentication process. By cryptographically linking the request body to its signature, the system gains protection against replay attacks and ensures that the data transmitted cannot be tampered with or re-used without invalidating the authentication. This change enhances the overall integrity and trustworthiness of communications within the verifier system.

Highlights

• Replay Attack Prevention: Implemented a robust mechanism to prevent replay attacks by incorporating a SHA-256 hash of the request body directly into the signed authentication payload, making each request cryptographically unique.
• Authentication Payload Enhancement: The authentication payload, previously comprising timestamp, verifier index, and sequencer version, now additionally includes the computed body hash, ensuring the integrity of the request content is part of the signature verification.
• Middleware Reordering for Body Hashing: Adjusted the order of middleware application, ensuring that the request body is extracted and available for hashing by the body_mw before the auth_mw attempts to verify the signature, which now depends on the body hash.
• Client-Side Body Hashing and Header Inclusion: The verifier client is updated to compute the SHA-256 hash of the request body for all authenticated requests and include this hash in a new X-Body-Hash header, which is then verified by the coordinator.

Using Gemini Code Assist

The full guide for Gemini Code Assist can be found on our documentation page, here are some quick tips.

Invoking Gemini

You can request assistance from Gemini at any point by creating a comment using either /gemini <command> or @gemini-code-assist <command>. Below is a summary of the supported commands on the current page.

Feature	Command	Description
Code Review	/gemini review	Performs a code review for the current pull request in its current state.
Pull Request Summary	/gemini summary	Provides a summary of the current pull request in its current state.
Comment	@gemini-code-assist	Responds in comments when explicitly tagged, both in pull request comments and review comments.
Help	/gemini help	Displays a list of available commands.

Customization

To customize Gemini Code Assist for GitHub experience, repository maintainers can create a configuration file and/or provide a custom code review style guide (such as PEP-8 for Python) by creating and adding files to a .gemini/ folder in the base of the repository. Detailed instructions can be found here.

Limitations & Feedback

Gemini Code Assist may make mistakes. Please leave feedback on any instances where its feedback is incorrect or counter productive. You can react with 👍 and 👎 on @gemini-code-assist comments. If you're interested in giving your feedback about your experience with Gemini Code Assist for Github and other Google products, sign up here.

You can also get AI-powered code generation, chat, as well as code reviews directly in the IDE at no cost with the Gemini Code Assist IDE Extension.

Footnotes

1. Review the Privacy Notices, Generative AI Prohibited Use Policy, Terms of Service, and learn how to configure Gemini Code Assist in GitHub here. Gemini can make mistakes, so double check it and use code with caution. ↩

[gemini-code-assist]

Code Review

This pull request effectively enhances security by incorporating a hash of the request body into the authentication payload, which prevents replay attacks. The changes are well-implemented across both the verifier (client) and coordinator (server). I appreciate the reordering of the middleware to ensure the body is available for hashing, and the updates to the client-side request building to handle raw bodies are correct. The improved error handling for timestamp parsing is also a nice touch. The new test case adequately covers the added functionality.