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feat(audit): finalize incomplete http requests #78

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3 changes: 3 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
Expand Up @@ -8,6 +8,9 @@ All notable changes to mcp-audit are documented in this file.

- Terminal audit `outcome` values and UUIDv7 `audit_operation_id` correlation,
with an exactly-once operation finalizer shared by HTTP and stdio transports.
- Complete HTTP terminal auditing for upstream connection failures, timeouts,
malformed and incomplete responses, SSE failures, cancellations, and client
disconnects. HTTP notifications are finalized only after the upstream result.
- Security invariants and release gates for v1.2.0.
- Installation cookbook with platform-specific notes in `INSTALL.md`.
- VS Code stdio configuration example under `examples/vscode/`.
Expand Down
99 changes: 82 additions & 17 deletions internal/proxy/http.go
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Original file line number Diff line number Diff line change
Expand Up @@ -5,6 +5,7 @@ import (
"bytes"
"context"
"encoding/json"
"errors"
"fmt"
"io"
"log/slog"
Expand Down Expand Up @@ -154,6 +155,7 @@ func (p *HTTPProxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {

pending, reject := p.observeHTTPRequest(body, startedAt)
if reject != nil {
p.finalizeHTTPPending(pending, audit.OutcomeCancelled, audit.DirectionClientToServer)
w.Header().Set("Content-Type", "application/json")
w.WriteHeader(http.StatusOK)
_, _ = w.Write(reject)
Expand All @@ -162,6 +164,7 @@ func (p *HTTPProxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {

resp, err := p.doUpstreamRequest(r, body)
if err != nil {
p.finalizeHTTPPending(pending, httpFailureOutcome(r.Context(), err), audit.DirectionServerToClient)
http.Error(w, "upstream request failed", http.StatusBadGateway)
p.log.Error("upstream request failed", "error", err)
return
Expand All @@ -171,19 +174,25 @@ func (p *HTTPProxy) ServeHTTP(w http.ResponseWriter, r *http.Request) {
copyHeader(w.Header(), resp.Header)
if isEventStream(resp.Header.Get("Content-Type")) {
w.WriteHeader(resp.StatusCode)
p.streamSSE(w, resp.Body, pending)
p.streamSSE(r.Context(), w, resp.Body, pending, resp.StatusCode)
return
}

respBody, err := io.ReadAll(resp.Body)
if err != nil {
p.finalizeHTTPPending(pending, httpFailureOutcome(r.Context(), err), audit.DirectionServerToClient)
http.Error(w, "failed to read upstream response", http.StatusBadGateway)
p.log.Error("failed to read upstream response", "error", err)
return
}
w.WriteHeader(resp.StatusCode)
_, _ = w.Write(respBody)
p.observeHTTPResponse(respBody, pending)
if _, err := w.Write(respBody); err != nil {
p.finalizeHTTPPending(pending, audit.OutcomeClientDisconnect, audit.DirectionServerToClient)
p.log.Warn("failed to write response to client", "error", err)
return
}
p.observeHTTPResponse(respBody, pending, resp.StatusCode)
p.finalizeHTTPRemainder(pending, resp.StatusCode)
}

func (p *HTTPProxy) doUpstreamRequest(r *http.Request, body []byte) (*http.Response, error) {
Expand Down Expand Up @@ -309,7 +318,7 @@ func (p *HTTPProxy) observeHTTPRequest(raw []byte, startedAt time.Time) (map[str
continue
}
toolName := toolNameFromParams(msg.Method, msg.Params)
call := p.newPendingCall(msg.Method, jsonRPCID(msg.ID), toolName, msg.Params, startedAt)
call := p.newPendingCall(msg.Method, jsonRPCID(msg.ID), toolName, msg.Params, len(msg.ID) > 0, startedAt)
if msg.Method == "tools/call" {
decision := p.evaluatePolicy(toolName)
p.recordPolicyDecision(decision)
Expand All @@ -335,48 +344,60 @@ func (p *HTTPProxy) observeHTTPRequest(raw []byte, startedAt time.Time) (map[str
pending[string(msg.ID)] = call
continue
}
if err := p.record(call, audit.OutcomeSuccess, audit.DirectionClientToServer, nil, nil); err != nil {
p.log.Error("failed to audit http notification", "error", err)
if call.operation != nil {
pending["notification:"+call.operation.ID()] = call
}
}
return pending, nil
}

func (p *HTTPProxy) observeHTTPResponse(raw []byte, pending map[string]pendingCall) {
func (p *HTTPProxy) observeHTTPResponse(raw []byte, pending map[string]pendingCall, statusCode int) bool {
if len(pending) == 0 || len(bytes.TrimSpace(raw)) == 0 {
return
return true
}
messages, err := decodeMessages(raw)
if err != nil {
p.log.Warn("failed to inspect http response", "error", err)
return
return false
}
for _, msg := range messages {
call, ok := pending[string(msg.ID)]
if !ok {
continue
}
if err := p.record(call, outcomeForRPCError(msg.Error), audit.DirectionServerToClient, msg.Result, msg.Error); err != nil {
outcome := outcomeForRPCError(msg.Error)
if statusCode >= http.StatusBadRequest {
outcome = audit.OutcomeUpstreamError
}
if err := p.record(call, outcome, audit.DirectionServerToClient, msg.Result, msg.Error); err != nil {
p.log.Error("failed to audit http response", "error", err)
}
delete(pending, string(msg.ID))
}
return true
}

func (p *HTTPProxy) streamSSE(w http.ResponseWriter, body io.Reader, pending map[string]pendingCall) {
func (p *HTTPProxy) streamSSE(ctx context.Context, w http.ResponseWriter, body io.Reader, pending map[string]pendingCall, statusCode int) {
flusher, _ := w.(http.Flusher)
reader := bufio.NewReader(body)
var data strings.Builder
for {
lineBytes, err := reader.ReadBytes('\n')
if len(lineBytes) > 0 {
_, _ = w.Write(lineBytes)
if _, writeErr := w.Write(lineBytes); writeErr != nil {
p.finalizeHTTPPending(pending, audit.OutcomeClientDisconnect, audit.DirectionServerToClient)
p.log.Warn("failed to stream response to client", "error", writeErr)
return
}
}
if flusher != nil {
flusher.Flush()
}
if len(lineBytes) == 0 && err != nil {
if err != io.EOF {
if err == io.EOF {
p.finalizeHTTPRemainder(pending, statusCode)
} else {
p.finalizeHTTPPending(pending, httpFailureOutcome(ctx, err), audit.DirectionServerToClient)
p.log.Error("failed to stream SSE response", "error", err)
}
return
Expand All @@ -386,19 +407,63 @@ func (p *HTTPProxy) streamSSE(w http.ResponseWriter, body io.Reader, pending map
data.WriteString(strings.TrimSpace(strings.TrimPrefix(line, "data:")))
}
if line == "" && data.Len() > 0 {
p.observeHTTPResponse([]byte(data.String()), pending)
if !p.observeHTTPResponse([]byte(data.String()), pending, statusCode) {
p.finalizeHTTPRemainder(pending, statusCode)
}
data.Reset()
}
if err != nil {
if err != io.EOF {
if err == io.EOF {
p.finalizeHTTPRemainder(pending, statusCode)
} else {
p.finalizeHTTPPending(pending, httpFailureOutcome(ctx, err), audit.DirectionServerToClient)
p.log.Error("failed to stream SSE response", "error", err)
}
return
}
}
}

func (p *HTTPProxy) newPendingCall(method, requestID, toolName string, params json.RawMessage, startedAt time.Time) pendingCall {
func (p *HTTPProxy) finalizeHTTPRemainder(pending map[string]pendingCall, statusCode int) {
for id, call := range pending {
outcome := audit.OutcomeMalformedUpstreamResponse
direction := audit.DirectionServerToClient
if statusCode >= http.StatusBadRequest {
outcome = audit.OutcomeUpstreamError
} else if !call.expectsResponse {
outcome = audit.OutcomeSuccess
direction = audit.DirectionClientToServer
}
if err := p.record(call, outcome, direction, nil, nil); err != nil {
p.log.Error("failed to finalize http audit operation", "outcome", outcome, "error", err)
}
delete(pending, id)
}
}

func (p *HTTPProxy) finalizeHTTPPending(pending map[string]pendingCall, outcome audit.Outcome, direction string) {
for id, call := range pending {
if err := p.record(call, outcome, direction, nil, nil); err != nil {
p.log.Error("failed to finalize incomplete http audit operation", "outcome", outcome, "error", err)
}
delete(pending, id)
}
}

func httpFailureOutcome(ctx context.Context, err error) audit.Outcome {
if errors.Is(err, context.DeadlineExceeded) {
return audit.OutcomeTimeout
}
if errors.Is(err, context.Canceled) {
if ctx != nil && errors.Is(ctx.Err(), context.Canceled) {
return audit.OutcomeClientDisconnect
}
return audit.OutcomeCancelled
}
return audit.OutcomeUpstreamError
}

func (p *HTTPProxy) newPendingCall(method, requestID, toolName string, params json.RawMessage, expectsResponse bool, startedAt time.Time) pendingCall {
operation, err := audit.NewOperation(p.config.Audit, audit.Entry{
Method: method,
RequestID: requestID,
Expand All @@ -410,7 +475,7 @@ func (p *HTTPProxy) newPendingCall(method, requestID, toolName string, params js
if err != nil {
p.log.Error("failed to start audit operation", "method", method, "error", err)
}
return pendingCall{operation: operation, startedAt: startedAt}
return pendingCall{operation: operation, startedAt: startedAt, expectsResponse: expectsResponse}
}

func (p *HTTPProxy) record(call pendingCall, outcome audit.Outcome, direction string, result json.RawMessage, rpcErr *audit.RPCError) error {
Expand Down
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