lib/ur: Implement crash (panic) reporting (fixes #959) (#5702)

* lib/ur: Implement crash (panic) reporting (fixes #959)

This implements a simple crash reporting method. It piggybacks on the
panic log files created by the monitor process, picking these up and
uploading them from the usage reporting routine.

A new config value points to the crash receiver base URL, which defaults
to "https://crash.syncthing.net/newcrash" (following the pattern of
"https://data.syncthing.net/newdata" for usage reports, but allowing us
to separate the service as required).

cmd/stcrashreceiver/sentry.go

@@ -0,0 +1,160 @@
+// 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/.
+
+package main
+
+import (
+	"bytes"
+	"errors"
+	"io/ioutil"
+	"regexp"
+	"strings"
+
+	raven "github.com/getsentry/raven-go"
+	"github.com/maruel/panicparse/stack"
+)
+
+const reportServer = "https://crash.syncthing.net/report/"
+
+func sendReport(dsn, path string, report []byte) error {
+	pkt, err := parseReport(path, report)
+	if err != nil {
+		return err
+	}
+
+	cli, err := raven.New(dsn)
+	if err != nil {
+		return err
+	}
+
+	// The client sets release and such on the packet before sending, in the
+	// misguided idea that it knows this better than than the packet we give
+	// it. So we copy the values from the packet to the client first...
+	cli.SetRelease(pkt.Release)
+	cli.SetEnvironment(pkt.Environment)
+
+	_, errC := cli.Capture(pkt, nil)
+	return <-errC
+}
+
+func parseReport(path string, report []byte) (*raven.Packet, error) {
+	parts := bytes.SplitN(report, []byte("\n"), 2)
+	if len(parts) != 2 {
+		return nil, errors.New("no first line")
+	}
+
+	version, err := parseVersion(string(parts[0]))
+	if err != nil {
+		return nil, err
+	}
+	report = parts[1]
+
+	foundPanic := false
+	var subjectLine []byte
+	for {
+		parts = bytes.SplitN(report, []byte("\n"), 2)
+		if len(parts) != 2 {
+			return nil, errors.New("no panic line found")
+		}
+
+		line := parts[0]
+		report = parts[1]
+
+		if foundPanic {
+			// The previous line was our "Panic at ..." header. We are now
+			// at the beginning of the real panic trace and this is our
+			// subject line.
+			subjectLine = line
+			break
+		} else if bytes.HasPrefix(line, []byte("Panic at")) {
+			foundPanic = true
+		}
+	}
+
+	r := bytes.NewReader(report)
+	ctx, err := stack.ParseDump(r, ioutil.Discard, false)
+	if err != nil {
+		return nil, err
+	}
+
+	var trace raven.Stacktrace
+	for _, gr := range ctx.Goroutines {
+		if gr.First {
+			trace.Frames = make([]*raven.StacktraceFrame, len(gr.Stack.Calls))
+			for i, sc := range gr.Stack.Calls {
+				trace.Frames[len(trace.Frames)-1-i] = &raven.StacktraceFrame{
+					Function: sc.Func.Name(),
+					Module:   sc.Func.PkgName(),
+					Filename: sc.SrcPath,
+					Lineno:   sc.Line,
+				}
+			}
+			break
+		}
+	}
+
+	pkt := &raven.Packet{
+		Message:  string(subjectLine),
+		Platform: "go",
+		Release:  version.tag,
+		Tags: raven.Tags{
+			raven.Tag{Key: "version", Value: version.version},
+			raven.Tag{Key: "tag", Value: version.tag},
+			raven.Tag{Key: "commit", Value: version.commit},
+			raven.Tag{Key: "codename", Value: version.codename},
+			raven.Tag{Key: "runtime", Value: version.runtime},
+			raven.Tag{Key: "goos", Value: version.goos},
+			raven.Tag{Key: "goarch", Value: version.goarch},
+			raven.Tag{Key: "builder", Value: version.builder},
+		},
+		Extra: raven.Extra{
+			"url": reportServer + path,
+		},
+		Interfaces: []raven.Interface{&trace},
+	}
+
+	return pkt, nil
+}
+
+// syncthing v1.1.4-rc.1+30-g6aaae618-dirty-crashrep "Erbium Earthworm" (go1.12.5 darwin-amd64) jb@kvin.kastelo.net 2019-05-23 16:08:14 UTC
+var longVersionRE = regexp.MustCompile(`syncthing\s+(v[^\s]+)\s+"([^"]+)"\s\(([^\s]+)\s+([^-]+)-([^)]+)\)\s+([^\s]+)`)
+
+type version struct {
+	version  string // "v1.1.4-rc.1+30-g6aaae618-dirty-crashrep"
+	tag      string // "v1.1.4-rc.1"
+	commit   string // "6aaae618", blank when absent
+	codename string // "Erbium Earthworm"
+	runtime  string // "go1.12.5"
+	goos     string // "darwin"
+	goarch   string // "amd64"
+	builder  string // "jb@kvin.kastelo.net"
+}
+
+func parseVersion(line string) (version, error) {
+	m := longVersionRE.FindStringSubmatch(line)
+	if len(m) == 0 {
+		return version{}, errors.New("unintelligeble version string")
+	}
+
+	v := version{
+		version:  m[1],
+		codename: m[2],
+		runtime:  m[3],
+		goos:     m[4],
+		goarch:   m[5],
+		builder:  m[6],
+	}
+	parts := strings.Split(v.version, "+")
+	v.tag = parts[0]
+	if len(parts) > 1 {
+		fields := strings.Split(parts[1], "-")
+		if len(fields) >= 2 && strings.HasPrefix(fields[1], "g") {
+			v.commit = fields[1][1:]
+		}
+	}
+
+	return v, nil
+}

cmd/stcrashreceiver/sentry_test.go

@@ -0,0 +1,64 @@
+// 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/.
+
+package main
+
+import (
+	"fmt"
+	"io/ioutil"
+	"testing"
+)
+
+func TestParseVersion(t *testing.T) {
+	cases := []struct {
+		longVersion string
+		parsed      version
+	}{
+		{
+			longVersion: `syncthing v1.1.4-rc.1+30-g6aaae618-dirty-crashrep "Erbium Earthworm" (go1.12.5 darwin-amd64) jb@kvin.kastelo.net 2019-05-23 16:08:14 UTC`,
+			parsed: version{
+				version:  "v1.1.4-rc.1+30-g6aaae618-dirty-crashrep",
+				tag:      "v1.1.4-rc.1",
+				commit:   "6aaae618",
+				codename: "Erbium Earthworm",
+				runtime:  "go1.12.5",
+				goos:     "darwin",
+				goarch:   "amd64",
+				builder:  "jb@kvin.kastelo.net",
+			},
+		},
+	}
+
+	for _, tc := range cases {
+		v, err := parseVersion(tc.longVersion)
+		if err != nil {
+			t.Error(err)
+			continue
+		}
+		if v != tc.parsed {
+			t.Error(v)
+		}
+	}
+}
+
+func TestParseReport(t *testing.T) {
+	bs, err := ioutil.ReadFile("_testdata/panic.log")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	pkt, err := parseReport("1/2/345", bs)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	bs, err = pkt.JSON()
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	fmt.Printf("%s\n", bs)
+}

cmd/stcrashreceiver/stcrashreceiver.go

@@ -0,0 +1,135 @@
+// 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 (
+	"flag"
+	"io"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+	"path"
+	"path/filepath"
+	"strings"
+)
+
+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()
+
+	cr := &crashReceiver{
+		dir: *dir,
+		dsn: *dsn,
+	}
+
+	log.SetOutput(os.Stdout)
+	if err := http.ListenAndServe(*listen, cr); err != nil {
+		log.Fatalln("HTTP serve:", err)
+	}
+}
+
+type crashReceiver struct {
+	dir string
+	dsn string
+}
+
+func (r *crashReceiver) ServeHTTP(w http.ResponseWriter, req *http.Request) {
+	// The final path component should be a SHA256 hash in hex, so 64 hex
+	// characters. We don't care about case on the request but use lower
+	// case internally.
+	base := strings.ToLower(path.Base(req.URL.Path))
+	if len(base) != 64 {
+		http.Error(w, "Bad request", http.StatusBadRequest)
+		return
+	}
+	for _, c := range base {
+		if c >= 'a' && c <= 'f' {
+			continue
+		}
+		if c >= '0' && c <= '9' {
+			continue
+		}
+		http.Error(w, "Bad request", http.StatusBadRequest)
+		return
+	}
+
+	switch req.Method {
+	case http.MethodHead:
+		r.serveHead(base, w, req)
+	case http.MethodPut:
+		r.servePut(base, w, req)
+	default:
+		http.Error(w, "Method not allowed", http.StatusMethodNotAllowed)
+	}
+}
+
+// serveHead responds to HEAD requests by checking if the named report
+// already exists in the system.
+func (r *crashReceiver) serveHead(base string, w http.ResponseWriter, _ *http.Request) {
+	path := filepath.Join(r.dirFor(base), base)
+	if _, err := os.Lstat(path); err != nil {
+		http.Error(w, "Not found", http.StatusNotFound)
+	}
+	// 200 OK
+}
+
+// servePut accepts and stores the given report.
+func (r *crashReceiver) servePut(base string, w http.ResponseWriter, req *http.Request) {
+	path := filepath.Join(r.dirFor(base), base)
+	fullPath := filepath.Join(r.dir, path)
+
+	// Ensure the destination directory exists
+	if err := os.MkdirAll(filepath.Dir(fullPath), 0755); err != nil {
+		log.Printf("Creating directory for report %s: %v", base, err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	// Read at most maxRequestSize of report data.
+	log.Println("Receiving report", base)
+	lr := io.LimitReader(req.Body, maxRequestSize)
+	bs, err := ioutil.ReadAll(lr)
+	if err != nil {
+		log.Println("Reading report:", err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	// Create an output file
+	err = ioutil.WriteFile(fullPath, bs, 0644)
+	if err != nil {
+		log.Printf("Creating file for report %s: %v", base, err)
+		http.Error(w, "Internal server error", http.StatusInternalServerError)
+		return
+	}
+
+	// Send the report to Sentry
+	if r.dsn != "" {
+		go func() {
+			// There's no need for the client to have to wait for this part.
+			if err := sendReport(r.dsn, path, bs); err != nil {
+				log.Println("Failed to send report:", err)
+			}
+		}()
+	}
+}
+
+// 01234567890abcdef... => 01/23
+func (r *crashReceiver) dirFor(base string) string {
+	return filepath.Join(base[0:2], base[2:4])
+}