fix(security): harden image proxy DNS rebinding, upload memory limits, and origin audit logging - #771
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- image_proxy: add DNS resolution check before outbound request to prevent DNS rebinding SSRF attacks. Resolves hostname and verifies IP is not in blocked ranges before making the HTTP request. - upload: add per-file size limit (20 MiB) to prevent memory exhaustion from large individual file uploads within the 100 MiB total limit. - origin: log WebSocket upgrades without Origin header for audit trail. Non-browser clients are still allowed but their access is now recorded. - outbound_http: document buildOutboundAllowedPorts memory allocation and add compact alternative for future optimization. Ref: source code audit findings
StackCairn
marked this pull request as draft
September 7, 2026 01:15
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Summary
This PR addresses several security findings from a source code audit of the agent-gateway component.
Changes
1. Image Proxy DNS Rebinding Protection (
image_proxy.go)safeurlwith IP blocklist, but did not resolve DNS before the actual request. DNS rebinding attacks could return a safe IP during validation and a malicious (internal) IP during the request.validateImageProxyURLthat resolves the hostname and verifies all resolved IPs are not in blocked ranges before allowing the request.2. Per-File Upload Size Limit (
upload.go)maxPerFileUploadBytes = 20 MiBper-file limit withio.LimitReaderto prevent unbounded memory allocation. Returns413 Request Entity Too Largewith the specific file name when exceeded.3. WebSocket Origin Audit Logging (
origin.go)Originheader (non-browser clients) were silently allowed with no audit trail.slog.Debuglogging when no Origin header is present, recording the remote address for security audit purposes.4. Outbound Ports Documentation (
outbound_http.go)buildOutboundAllowedPorts()allocates a 65535-element[]intslice (~512 KB) at init time, passed as variadic arguments tosafeurl.buildOutboundAllowedPortsCompact()alternative for future optimization if the library supports range-based configuration.Testing
Related
Source code audit of the agent-gateway Go codebase, focusing on SSRF, memory safety, and security observability.