bug: recursive scan_value/redact_value in payload filter can stack overflow on deeply nested JSON

[nfvelten]

Migrated from nfvelten/arbitus#123

Summary

scan_value and redact_value in src/middleware/payload_filter.rs recurse into nested JSON without any depth limit. A payload with 10,000+ levels of nesting will overflow the stack and crash the server.

Location

src/middleware/payload_filter.rs

Fix

Add a max_depth parameter (default 64). On limit: either reject the payload with a JSON-RPC error or treat it as a block decision. Convert to iterative traversal using an explicit stack for robustness.

Related

• feat: replace custom rate limiter with governor (GCRA, lock-free) #110 tracks the test for large payload / deeply nested JSON rejection
• This is the code-level fix that feat: replace custom rate limiter with governor (GCRA, lock-free) #110's test will validate

References

• PROPOSAL.md §4.3