WebSocket interception

The last "known limitation": a ws://wss:// connection stops being
one-shot request/response the instant its 101 Switching Protocols
lands, and forward()'s normal write-response-then-record flow has no
way to represent that. Scoped to HTTP/1.1 client legs (HTTP/2 can't be
hijacked for raw post-response access the way HTTP/1.1 can, and
browsers open a dedicated HTTP/1.1 connection for WebSocket regardless
of the surrounding page's protocol, so this isn't a real-world gap).

internal/proxy/websocket.go decodes each RFC 6455 frame's opcode and
payload for capture while relaying the exact same raw bytes it read
unmodified - this is capture, not tampering, matching the rest of the
codebase's raw-bytes-as-source-of-truth stance. One row per frame, not
per reassembled message (fragmentation is rare in real-world
WebSocket traffic; not worth buffering an unbounded number of pending
fragments to handle it). forward() branches on a matching 101 into
handleWebSocketUpgrade, which hijacks the client connection, relays
the handshake response raw, records the upgrade request/response to
history normally, then relays frames bidirectionally into a new
ws_messages table - reachable from the TUI's detail view via `w`.

Found and fixed two real bugs by actually driving a WebSocket
connection through a running daemon, not by reading the code:
stripHopByHop was deleting Connection/Upgrade from every outgoing
request (correct for an ordinary request per RFC 7230, catastrophic
for one asking to upgrade - every WebSocket attempt silently became a
426); and the relay tore the whole connection down the instant either
side saw a close frame, before the peer's own close-frame reply could
be relayed back, producing an abrupt EOF instead of a clean close.

Verified live end to end on both paths a real client uses: ws://
(plain HTTP forward-proxying) against a Python websockets echo
server, and wss:// (CONNECT-tunneled, TLS-intercepted) against the
same server behind TLS - text, binary, and extended-length frames,
plus a full close handshake with both directions' close frames
present, confirmed via the actual bytes captured in ws_messages.

2 files changed, 28 insertions, 0 deletions

diff --git a/internal/ipc/ipc.go b/internal/ipc/ipc.go
index 68217c2..dc7a1df 100644
--- a/internal/ipc/ipc.go
+++ b/internal/ipc/ipc.go
@@ -114,6 +114,7 @@ type Response struct {
 	Rules       []rules.Rule      `json:"rules,omitempty"`        // for "rules"
 	ScopeRules  []scope.Rule      `json:"scope_rules,omitempty"`  // for "scope_rules"
 	ClientCerts []clientcert.Cert `json:"client_certs,omitempty"` // for "client_certs"
+	WSMessages  []store.WSMessage `json:"ws_messages,omitempty"`  // for "ws_messages"
 	Status      *StatusMsg        `json:"status,omitempty"`       // for "status"
 
 	// For "import_done": how many entries were actually inserted (a
@@ -331,6 +332,25 @@ func (c *Client) Get(id int64) (*EntryDetail, error) {
 	return resp.Detail, nil
 }
 
+// ListWSMessages returns every WebSocket frame captured for entryID's
+// connection, in the order they were sent - empty (not an error) if the
+// entry wasn't a WebSocket upgrade or nothing was captured.
+func (c *Client) ListWSMessages(entryID int64) ([]store.WSMessage, error) {
+	c.mu.Lock()
+	defer c.mu.Unlock()
+	if err := c.enc.Encode(Request{Type: "ws_messages", ID: entryID}); err != nil {
+		return nil, err
+	}
+	var resp Response
+	if err := c.dec.Decode(&resp); err != nil {
+		return nil, err
+	}
+	if resp.Type == "error" {
+		return nil, errors.New(resp.Error)
+	}
+	return resp.WSMessages, nil
+}
+
 // Repeat sends raw to scheme://host exactly as given (no re-serialization,
 // no header injection) and returns the resulting entry, including the raw
 // response bytes. The exchange is also recorded to history.
diff --git a/internal/ipc/server.go b/internal/ipc/server.go
index 4db27b9..378c1a9 100644
--- a/internal/ipc/server.go
+++ b/internal/ipc/server.go
@@ -143,6 +143,14 @@ func (s *Server) handleConn(conn net.Conn) {
 			}
 			enc.Encode(Response{Type: "get", Detail: detailFromEntry(e)})
 
+		case "ws_messages":
+			msgs, err := s.db.ListWSMessages(req.ID)
+			if err != nil {
+				enc.Encode(Response{Type: "error", Error: err.Error()})
+				continue
+			}
+			enc.Encode(Response{Type: "ws_messages", WSMessages: msgs})
+
 		case "repeat":
 			if s.repeater == nil {
 				enc.Encode(Response{Type: "error", Error: "repeater not available"})