reverse-proxy/tasks/fix/admin-socket-resource-limits.md

id, name, status, depends_on, scope, risk, impact, level, review_findings

id	name	status	depends_on	scope	risk	impact	level	review_findings
fix/admin-socket-resource-limits	Add read timeout and line length limit to admin socket (ADR-027)	pending		narrow	low	component	implementation	W4 S4

Description

The admin socket's handle_connection reads one newline-terminated line with reader.read_line(&mut line) but sets no timeout and no length limit. This allows:

1. A client to connect and send no data, holding a connection indefinitely
2. A client to send unbounded data without a newline, causing OOM

ADR-027 specifies: 5-second read timeout, 4096 byte line length limit.

Changes Required

src/admin/socket.rs — handle_connection function (lines 166-210):

• Wrap the BufReader with tokio::io::take to limit read size to 4096 bytes:

  let (reader, mut writer) = stream.into_split();
  let mut reader = BufReader::new(tokio::io::take(reader, 4096));
  let mut line = String::new();
  

• Wrap the read_line call in a tokio::time::timeout:

  use std::time::Duration;
  let read_result = tokio::time::timeout(
      Duration::from_secs(5),
      reader.read_line(&mut line),
  ).await;
  

• Handle timeout and line-too-long cases:

  match read_result {
      Ok(Ok(0)) | Ok(Err(_)) => {
          // existing "invalid input" handling
      }
      Err(_) => {
          // timeout
          tracing::debug!("admin socket connection timed out");
          let _ = writer.write_all(
              format!("{}\n", serde_json::to_string(&ErrorResponse {
                  status: "error",
                  message: "read timeout".to_string(),
              }).unwrap()).as_bytes()
          ).await;
          return;
      }
      Ok(Ok(n)) => {
          // Check if line was truncated (no newline found within limit)
          if !line.ends_with('\n') && n > 0 {
              tracing::warn!("admin socket command exceeded 4096 byte limit");
              let _ = writer.write_all(
                  format!("{}\n", serde_json::to_string(&ErrorResponse {
                      status: "error",
                      message: "command too long".to_string(),
                  }).unwrap()).as_bytes()
              ).await;
              return;
          }
          // ... existing command handling
      }
  }
  

• Update existing tests and add new tests for timeout and line length limit.

Acceptance Criteria

• Read timeout of 5 seconds applied to admin socket connections
• Line length limit of 4096 bytes applied (via tokio::io::take)
• Timeout logged at debug level per ADR-027
• Line-too-long logged at warn level per ADR-027
• Both conditions return appropriate error JSON to the client
• Legitimate commands (reload, status) still work
• New tests for timeout and line length limit behavior
• cargo test passes
• cargo clippy passes with no warnings

References

• docs/architecture/decisions/027-admin-socket-resource-limits.md — ADR-027
• docs/architecture/operations.md — admin socket resource limits
• docs/reviews/003-security-and-bug-review.md — W4, S4 findings
• src/admin/socket.rs — handle_connection

Notes

To be filled on completion

Summary

To be filled on completion