fix(via_verifier_coordinator): prevent panic on malformed timestamp header input

[romanornr]

What ❔

Fix let timestamp_diff = timestamp_now - timestamp.parse::<i64>().unwrap();

.unwrap on untrusted input from HTTP header X-timestamp

However, this can also be fixed with

let timestamp_diff = timestamp_now - timestamp.parse::<i64>()
    .map_err(|_| ApiError::Unauthorized("Invalid timestamp".into()))?;

or

// Pre-validate format
if !timestamp.chars().all(|c| c.is_ascii_digit() || c == '-') {
    tracing::warn!("Rejected malformed timestamp");
    return Err(ApiError::Unauthorized("Invalid timestamp format".into()));
}

// Parse with logging
let parsed = timestamp.parse::<i64>().map_err(|e| {
    tracing::warn!("Parse failed: {}", e);
    ApiError::Unauthorized("Invalid timestamp".into())
})?;

// Bounds check
if parsed < 0 || parsed > 253402300799 {
    return Err(ApiError::Unauthorized("Timestamp out of range".into()));
}

Why ❔

Simple crash - malformed timestamp causes panic

curl -X POST "http://localhost:8080/session/new" \
  -H "X-Timestamp: CRASH" \
  -H "X-Verifier-Index: 0" \
  -H "X-Signature: fake" \
  -H "X-Sequencer-Version: 1.0.0"

Empty string

curl -X GET "http://localhost:8080/session/" \
  -H "X-Timestamp: " \
  -H "X-Verifier-Index: 0" \
  -H "X-Signature: fake" \
  -H "X-Sequencer-Version: 1.0.0"

Overflow attempt (too large for i64)

curl -X POST "http://localhost:8080/session/nonce" \
  -H "X-Timestamp: 99999999999999999999999999999" \
  -H "X-Verifier-Index: 0" \
  -H "X-Signature: fake" \
  -H "X-Sequencer-Version: 1.0.0"

Special characters

curl -X GET "http://localhost:8080/session/nonce" \
  -H "X-Timestamp: <script>alert(1)</script>" \
  -H "X-Verifier-Index: 0" \
  -H "X-Signature: fake" \
  -H "X-Sequencer-Version: 1.0.0"

keeps crashing the coordinator

#!/bin/bash
TARGET="http://localhost:8080/session/new"

while true; do
  curl -s -X POST "$TARGET" \
    -H "X-Timestamp: KILL" \
    -H "X-Verifier-Index: 0" \
    -H "X-Signature: x" \
    -H "X-Sequencer-Version: 1.0.0"
  sleep 0.1
done

From the code at api.rs

let bind_address = config.bind_addr();  // Configurable - could be 0.0.0.0
let listener = tokio::net::TcpListener::bind(bind_address).await

The coordinator binds to a network socket

From verifier/mod.rs

let url = format!(
    "{}/session/nonce",
    self.verifier_config.coordinator_http_url  // Other verifiers connect here
);

Production

   Verifier 1 ──┐                                           
   Verifier 2 ──┼──► Coordinator:8080 ◄── Attacker?         
   Verifier 3 ──┘        │                                  
                         │                                  
                    ┌────▼────┐                             
                    │ Bitcoin │                             
                    │ Network │                             
                    └─────────┘                             

Would suck with malicious verifier operators (1/N verifiers goes rogue)
Attacker gains shell
Network insider

Should not be bad if properly isolated and firewall blocks external access

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 addresses a critical vulnerability where malformed X-Timestamp HTTP headers could lead to application panics and denial of service. It introduces robust validation and parsing logic for the timestamp header, including checks for format, parseability, and reasonable bounds (0 to Year 9999). This significantly enhances the stability and security of the coordinator by preventing crashes from untrusted input and centralizing the validation logic into a testable function.

Highlights

• Robust Timestamp Validation: Implemented comprehensive validation for the X-Timestamp HTTP header to prevent application panics caused by malformed, unparseable, or out-of-bounds timestamp inputs.
• Centralized Validation Logic: Extracted the timestamp validation logic into a dedicated, testable function validate_timestamp for improved code organization, reusability, and clarity.
• Enhanced Security and Stability: The changes prevent potential denial-of-service attacks by malicious actors sending invalid timestamps, significantly improving the coordinator's resilience and preventing crashes.

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[gemini-code-assist]

Code Review

This pull request addresses a critical panic caused by malformed timestamp headers, which is an important security fix. The approach of adding robust validation, including format and bounds checks, is excellent. The addition of a comprehensive test suite for the new validation logic is also a great practice. My review focuses on improving code reuse by leveraging the new helper function in the middleware and simplifying the validation logic for better clarity and maintainability.

[0xatomFusion]

Great fix