feat: ClamAV file scanning for uploaded/downloaded content

[aecs4u]

Summary

Integrate ClamAV virus scanning for files processed by agent tools (write_file, web_fetch, skill installation) to prevent malware from entering the workspace.

Prior Art

• AutoGPT integrates ClamAV scanning for all file uploads in its platform — files are scanned via clamd socket before being stored or processed by agent blocks. Infected files are quarantined and the agent is notified.
• This aligns with RustyClaw's security-first philosophy and complements the existing sandbox isolation.

Motivation

RustyClaw agents can download files from the web (web_fetch), install skills, and write arbitrary files. A compromised or hallucinating agent could inadvertently download malware. ClamAV scanning adds a defense layer that catches known malware signatures before files reach the filesystem.

Proposed Design

1. Optional integration with clamd daemon via Unix socket or TCP
2. Scan triggers:
   • web_fetch responses before writing to disk
   • write_file content before writing
   • Skill package files during installation
3. On detection: quarantine file, log the event (feat: Structured JSONL audit logging with rotation #68), notify user via TUI
4. Configuration:

   [security.clamav]
   enabled = false
   socket = "/var/run/clamav/clamd.ctl"
   quarantine_dir = "~/.rustyclaw/quarantine"

5. Feature-gated behind --features clamav to avoid mandatory dependency

Acceptance Criteria

• ClamAV integration via clamd socket
• Scanning on file write, web fetch, and skill install
• Quarantine infected files with audit log entry
• Feature-gated and optional (graceful degradation when clamd unavailable)
• Documentation for ClamAV setup

Related Issues

• feat: LLM-based prompt injection classifier #67 (LLM-based prompt injection classifier — complementary security layer)
• feat: Structured JSONL audit logging with rotation #68 (Structured JSONL audit logging)
• feat: WASM sandbox with capability-based security #59 (WASM sandbox — file scanning at sandbox boundary)