security(mcp): implement tools/list_changed refresh path with sanitization#1762
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security(mcp): implement tools/list_changed refresh path with sanitization#1762
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…ation Implement MCP tools/list_changed notification handler in McpManager so that tool list refreshes pushed by servers are sanitized before entering the system prompt (closes #1746). Key changes: - Add ToolListChangedHandler implementing rmcp::ClientHandler; handler applies rate-limiting (5 s per server) and MAX_TOOLS_PER_SERVER cap (100) before calling sanitize_tools(), then sends a ToolRefreshEvent via mpsc - McpManager gains a background refresh task (spawn_refresh_task) that receives ToolRefreshEvents and broadcasts via watch::Sender<Vec<McpTool>> - subscribe_tool_changes() exposes the watch receiver to callers - remove_server() cleans up server_tools HashMap and last_refresh DashMap - shutdown_all_shared() drops refresh_tx, terminating the refresh task cleanly - Agent checks watch::Receiver between turns via check_tool_refresh(), guarded against consuming the empty initial value Security invariants: sanitize_tools() is always called before tools reach the channel or the agent — same guarantee as the connect_all()/add_server() paths.
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Summary
Fixes #1746. MCP servers can push tool list updates via
tools/list_changednotifications. This PR implements the handler so thatsanitize_tools()is always called before refreshed tools enter the registry or system prompt.ToolListChangedHandlerimplementingrmcp::ClientHandler; applies rate-limiting (5 s/server) andMAX_TOOLS_PER_SERVER=100cap beforesanitize_tools(), then sends aToolRefreshEventvia mpscMcpManager::spawn_refresh_task()receives events and broadcasts viawatch::Sender<Vec<McpTool>>McpManager::subscribe_tool_changes()exposes the watch receiver to callersremove_server()cleans upserver_toolsHashMap andlast_refreshDashMapshutdown_all_shared()dropsrefresh_tx, terminating the refresh task cleanlywatch::Receiverbetween turns viacheck_tool_refresh(), guarded against consuming the empty initial valueSecurity invariants:
sanitize_tools()is unconditionally called before tools reach the channel or the agent — same guarantee as theconnect_all()andadd_server()paths.Test plan
cargo nextest run --workspace --features full --lib --bins)cargo clippy --workspace --features full -- -D warningspasses (0 warnings)cargo +nightly fmt --checkpasses