From 4ea51eb744e0ede9215194c02a46db8611ea49e9 Mon Sep 17 00:00:00 2001
From: "Sascha L. Teichmann" <sascha.teichmann@intevation.de>
Date: Sat, 15 Nov 2014 13:40:39 +0100
Subject: [PATCH] mtwebmapper: Only allow update requests from a white list of
 remote hosts. Defaults to localhost. To allow all hosts use command line
 option -u=''

---
 cmd/mtwebmapper/main.go         | 35 ++++++++++++++++++++++++++++-
 cmd/mtwebmapper/tilesupdater.go | 39 +++++++++++++++++++++++++++++++++
 2 files changed, 73 insertions(+), 1 deletion(-)

diff --git a/cmd/mtwebmapper/main.go b/cmd/mtwebmapper/main.go
index a70ffd2..4edd209 100644
--- a/cmd/mtwebmapper/main.go
+++ b/cmd/mtwebmapper/main.go
@@ -8,13 +8,34 @@ import (
 	"flag"
 	"fmt"
 	"log"
+	"net"
 	"net/http"
+	"strings"
 
 	"bitbucket.org/s_l_teichmann/mtsatellite/common"
 
 	"github.com/gorilla/mux"
 )
 
+func ipsFromHosts(hosts string) ([]net.IP, error) {
+
+	ips := []net.IP{}
+
+	if len(hosts) == 0 { // Empty list: allow all hosts.
+		return ips, nil
+	}
+
+	for _, host := range strings.Split(hosts, ";") {
+		if hips, err := net.LookupIP(host); err != nil {
+			return nil, err
+		} else {
+			ips = append(ips, hips...)
+		}
+	}
+
+	return ips, nil
+}
+
 func main() {
 	var (
 		webPort     int
@@ -26,6 +47,7 @@ func main() {
 		colorsFile  string
 		workers     int
 		transparent bool
+		updateHosts string
 	)
 	flag.IntVar(&webPort, "web-port", 8808, "port of the web server")
 	flag.IntVar(&webPort, "p", 8808, "port of the web server (shorthand)")
@@ -35,6 +57,10 @@ func main() {
 	flag.StringVar(&webDir, "w", "web", "static served web files (shorthand)")
 	flag.StringVar(&mapDir, "map", "map", "directory of prerendered tiles")
 	flag.StringVar(&mapDir, "m", "map", "directory of prerendered tiles (shorthand)")
+	flag.StringVar(&updateHosts, "update-hosts", "localhost",
+		"';' separated list of hosts which are allowed to send map update requests")
+	flag.StringVar(&updateHosts, "u", "localhost",
+		"';' separated list of hosts which are allowed to send map update requests (shorthand)")
 	flag.StringVar(&redisHost, "redis-host", "", "address of the backend Redis server")
 	flag.StringVar(&redisHost, "rh", "", "address of the backend Redis server (shorthand)")
 	flag.IntVar(&redisPort, "redis-port", 6379, "port of the backend Redis server")
@@ -59,7 +85,14 @@ func main() {
 			log.Fatalf("ERROR: problem loading colors: %s", err)
 		}
 		redisAddress := fmt.Sprintf("%s:%d", redisHost, redisPort)
-		tu := newTileUpdater(mapDir, redisAddress, colors, transparent, workers)
+
+		var allowedUpdateIps []net.IP
+		if allowedUpdateIps, err = ipsFromHosts(updateHosts); err != nil {
+			log.Fatalf("ERROR: name resolving problem: %s", err)
+		}
+
+		tu := newTileUpdater(
+			mapDir, redisAddress, allowedUpdateIps, colors, transparent, workers)
 		go tu.doUpdates()
 		router.Path("/update").Methods("POST").Handler(tu)
 	}
diff --git a/cmd/mtwebmapper/tilesupdater.go b/cmd/mtwebmapper/tilesupdater.go
index 7047164..a0b07d4 100644
--- a/cmd/mtwebmapper/tilesupdater.go
+++ b/cmd/mtwebmapper/tilesupdater.go
@@ -10,13 +10,17 @@ import (
 	"image"
 	"image/draw"
 	"log"
+	"net"
 	"net/http"
 	"path/filepath"
 	"strconv"
+	"strings"
 	"sync"
 
 	"github.com/nfnt/resize"
 
+	"bytes"
+
 	"bitbucket.org/s_l_teichmann/mtsatellite/common"
 )
 
@@ -24,6 +28,7 @@ type tileUpdater struct {
 	changes      map[xz]bool
 	mapDir       string
 	redisAddress string
+	ips          []net.IP
 	colors       *common.Colors
 	workers      int
 	transparent  bool
@@ -59,6 +64,7 @@ func (c xz) parent() xzm {
 
 func newTileUpdater(
 	mapDir, redisAddress string,
+	ips []net.IP,
 	colors *common.Colors,
 	transparent bool,
 	workers int) *tileUpdater {
@@ -66,6 +72,7 @@ func newTileUpdater(
 	tu := tileUpdater{
 		mapDir:       mapDir,
 		redisAddress: redisAddress,
+		ips:          ips,
 		changes:      map[xz]bool{},
 		colors:       colors,
 		transparent:  transparent,
@@ -74,7 +81,39 @@ func newTileUpdater(
 	return &tu
 }
 
+func (tu *tileUpdater) checkIP(r *http.Request) bool {
+	if len(tu.ips) == 0 {
+		return true
+	}
+
+	var host []string
+	if host = strings.SplitN(r.RemoteAddr, ":", 2); len(host) < 1 {
+		log.Printf("WARN: cannot extract host from '%s'\n", r.RemoteAddr)
+		return false
+	}
+
+	var ip net.IP
+	if ip = net.ParseIP(host[0]); ip == nil {
+		log.Printf("WARN: cannot get IP for host '%s'.\n", host[0])
+		return false
+	}
+
+	for i := range tu.ips {
+		if bytes.Compare(tu.ips[i], ip) == 0 {
+			return true
+		}
+	}
+
+	return false
+}
+
 func (tu *tileUpdater) ServeHTTP(rw http.ResponseWriter, r *http.Request) {
+	if !tu.checkIP(r) {
+		log.Printf("WARN: Unauthorized update request from '%s'", r.RemoteAddr)
+		http.Error(rw, http.StatusText(http.StatusUnauthorized), http.StatusUnauthorized)
+		return
+	}
+
 	var err error
 	var newChanges []xz
 	decoder := json.NewDecoder(r.Body)