Give rageshake script its own repo

This was previously at
https://github.com/vector-im/riot-web/blob/develop/scripts/rageshake.go, but
it's not really exclusive to riot-web, and given I'm about to add some more
complexity to it, I'd like for it to be in its own repo.

hooks/install.sh

@@ -0,0 +1,5 @@
+#! /bin/bash
+
+DOT_GIT="$(dirname $0)/../.git"
+
+ln -s "../../hooks/pre-commit" "$DOT_GIT/hooks/pre-commit"

hooks/pre-commit

@@ -0,0 +1,9 @@
+#! /bin/bash
+
+set -eu
+
+golint src/...
+go fmt ./src/...
+go tool vet --shadow ./src
+gocyclo -over 12 src/
+gb test

src/github.com/matrix-org/rageshake/main.go

@@ -0,0 +1,146 @@
+// Run a web server capable of dumping bug reports sent by Riot.
+// Requires Go 1.5+
+// Usage:   BUGS_USER=user BUGS_PASS=password go run rageshake.go PORT
+// Example: BUGS_USER=alice BUGS_PASS=secret go run rageshake.go 8080
+package main
+
+import (
+	"bytes"
+	"compress/gzip"
+	"crypto/subtle"
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"log"
+	"net/http"
+	"os"
+	"path/filepath"
+	"strconv"
+	"time"
+)
+
+var maxPayloadSize = 1024 * 1024 * 55 // 55 MB
+
+type LogEntry struct {
+	ID    string `json:"id"`
+	Lines string `json:"lines"`
+}
+
+type Payload struct {
+	Text      string     `json:"text"`
+	Version   string     `json:"version"`
+	UserAgent string     `json:"user_agent"`
+	Logs      []LogEntry `json:"logs"`
+}
+
+func respond(code int, w http.ResponseWriter) {
+	w.WriteHeader(code)
+	w.Write([]byte("{}"))
+}
+
+func gzipAndSave(data []byte, dirname, fpath string) error {
+	_ = os.MkdirAll(filepath.Join("bugs", dirname), os.ModePerm)
+	fpath = filepath.Join("bugs", dirname, fpath)
+
+	if _, err := os.Stat(fpath); err == nil {
+		return fmt.Errorf("file already exists") // the user can just retry
+	}
+	var b bytes.Buffer
+	gz := gzip.NewWriter(&b)
+	if _, err := gz.Write(data); err != nil {
+		return err
+	}
+	if err := gz.Flush(); err != nil {
+		return err
+	}
+	if err := gz.Close(); err != nil {
+		return err
+	}
+	if err := ioutil.WriteFile(fpath, b.Bytes(), 0644); err != nil {
+		return err
+	}
+	return nil
+}
+
+func basicAuth(handler http.Handler, username, password, realm string) http.Handler {
+	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		user, pass, ok := r.BasicAuth() // pull creds from the request
+
+		// check user and pass securely
+		if !ok || subtle.ConstantTimeCompare([]byte(user), []byte(username)) != 1 || subtle.ConstantTimeCompare([]byte(pass), []byte(password)) != 1 {
+			w.Header().Set("WWW-Authenticate", `Basic realm="`+realm+`"`)
+			w.WriteHeader(401)
+			w.Write([]byte("Unauthorised.\n"))
+			return
+		}
+
+		handler.ServeHTTP(w, r)
+	})
+}
+
+func main() {
+	http.HandleFunc("/api/submit", func(w http.ResponseWriter, req *http.Request) {
+		if req.Method != "POST" && req.Method != "OPTIONS" {
+			respond(405, w)
+			return
+		}
+		// Set CORS
+		w.Header().Set("Access-Control-Allow-Origin", "*")
+		w.Header().Set("Access-Control-Allow-Methods", "POST, OPTIONS")
+		w.Header().Set("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept")
+		if req.Method == "OPTIONS" {
+			respond(200, w)
+			return
+		}
+		if length, err := strconv.Atoi(req.Header.Get("Content-Length")); err != nil || length > maxPayloadSize {
+			respond(413, w)
+			return
+		}
+		var p Payload
+		if err := json.NewDecoder(req.Body).Decode(&p); err != nil {
+			respond(400, w)
+			return
+		}
+		// Dump bug report to disk as form:
+		//  "bugreport-20170115-112233.log.gz" => user text, version, user agent, # logs
+		//  "bugreport-20170115-112233-0.log.gz" => most recent log
+		//  "bugreport-20170115-112233-1.log.gz" => ...
+		//  "bugreport-20170115-112233-N.log.gz" => oldest log
+		t := time.Now().UTC()
+		prefix := t.Format("2006-01-02/150405")
+		summary := fmt.Sprintf(
+			"%s\n\nNumber of logs: %d\nVersion: %s\nUser-Agent: %s\n", p.Text, len(p.Logs), p.Version, p.UserAgent,
+		)
+		if err := gzipAndSave([]byte(summary), prefix, "details.log.gz"); err != nil {
+			respond(500, w)
+			return
+		}
+		for i, log := range p.Logs {
+			if err := gzipAndSave([]byte(log.Lines), prefix, fmt.Sprintf("logs-%d.log.gz", i)); err != nil {
+				respond(500, w)
+				return // TODO: Rollback?
+			}
+		}
+		respond(200, w)
+	})
+
+	// Make sure bugs directory exists
+	_ = os.Mkdir("bugs", os.ModePerm)
+
+	// serve files under "bugs"
+	fs := http.FileServer(http.Dir("bugs"))
+	fs = http.StripPrefix("/api/listing/", fs)
+
+	// set auth if env vars exist
+	usr := os.Getenv("BUGS_USER")
+	pass := os.Getenv("BUGS_PASS")
+	if usr == "" || pass == "" {
+		fmt.Println("BUGS_USER and BUGS_PASS env vars not found. No authentication is running for /api/listing")
+	} else {
+		fs = basicAuth(fs, usr, pass, "Riot bug reports")
+	}
+	http.Handle("/api/listing/", fs)
+
+	port := os.Args[1]
+	log.Fatal(http.ListenAndServe(":"+port, nil))
+}