all: Add failure reporting (fixes #7028) (#6925)

cmd/stcrashreceiver/main.go

@@ -0,0 +1,114 @@
+// Copyright (C) 2019 The Syncthing Authors.
+//
+// This Source Code Form is subject to the terms of the Mozilla Public
+// License, v. 2.0. If a copy of the MPL was not distributed with this file,
+// You can obtain one at https://mozilla.org/MPL/2.0/.
+
+// Command stcrashreceiver is a trivial HTTP server that allows two things:
+//
+// - uploading files (crash reports) named like a SHA256 hash using a PUT request
+// - checking whether such file exists using a HEAD request
+//
+// Typically this should be deployed behind something that manages HTTPS.
+package main
+
+import (
+	"encoding/json"
+	"flag"
+	"fmt"
+	"io"
+	"io/ioutil"
+	"log"
+	"net"
+	"net/http"
+	"os"
+	"time"
+
+	"github.com/syncthing/syncthing/lib/sha256"
+	"github.com/syncthing/syncthing/lib/ur"
+
+	raven "github.com/getsentry/raven-go"
+)
+
+const maxRequestSize = 1 << 20 // 1 MiB
+
+func main() {
+	dir := flag.String("dir", ".", "Directory to store reports in")
+	dsn := flag.String("dsn", "", "Sentry DSN")
+	listen := flag.String("listen", ":22039", "HTTP listen address")
+	flag.Parse()
+
+	mux := http.NewServeMux()
+
+	cr := &crashReceiver{
+		dir: *dir,
+		dsn: *dsn,
+	}
+	mux.Handle("/", cr)
+
+	if *dsn != "" {
+		mux.HandleFunc("/failure", handleFailureFn(*dsn))
+	}
+
+	log.SetOutput(os.Stdout)
+	if err := http.ListenAndServe(*listen, mux); err != nil {
+		log.Fatalln("HTTP serve:", err)
+	}
+}
+
+func handleFailureFn(dsn string) func(w http.ResponseWriter, req *http.Request) {
+	return func(w http.ResponseWriter, req *http.Request) {
+		lr := io.LimitReader(req.Body, maxRequestSize)
+		bs, err := ioutil.ReadAll(lr)
+		req.Body.Close()
+		if err != nil {
+			http.Error(w, err.Error(), 500)
+			return
+		}
+
+		var reports []ur.FailureReport
+		err = json.Unmarshal(bs, &reports)
+		if err != nil {
+			http.Error(w, err.Error(), 400)
+			return
+		}
+		if len(reports) == 0 {
+			// Shouldn't happen
+			return
+		}
+
+		version, err := parseVersion(reports[0].Version)
+		if err != nil {
+			http.Error(w, err.Error(), 400)
+			return
+		}
+		for _, r := range reports {
+			pkt := packet(version)
+			pkt.Message = r.Description
+			pkt.Extra = raven.Extra{
+				"count": r.Count,
+			}
+
+			if err := sendReport(dsn, pkt, userIDFor(req)); err != nil {
+				log.Println("Failed to send  crash report:", err)
+			}
+		}
+	}
+}
+
+// userIDFor returns a string we can use as the user ID for the purpose of
+// counting affected users. It's the truncated hash of a salt, the user
+// remote IP, and the current month.
+func userIDFor(req *http.Request) string {
+	addr := req.RemoteAddr
+	if fwd := req.Header.Get("x-forwarded-for"); fwd != "" {
+		addr = fwd
+	}
+	if host, _, err := net.SplitHostPort(addr); err == nil {
+		addr = host
+	}
+	now := time.Now().Format("200601")
+	salt := "stcrashreporter"
+	hash := sha256.Sum256([]byte(salt + addr + now))
+	return fmt.Sprintf("%x", hash[:8])
+}