middleware: add sanitization hook

frontend/http/frontend.go

@@ -13,6 +13,7 @@ import (
 	"github.com/prometheus/client_golang/prometheus"
 	"github.com/tylerb/graceful"
 
+	"github.com/chihaya/chihaya/bittorrent"
 	"github.com/chihaya/chihaya/frontend"
 	"github.com/chihaya/chihaya/middleware"
 )
@@ -22,6 +23,9 @@ func init() {
 	recordResponseDuration("action", nil, time.Second)
 }
 
+// ErrInvalidIP indicates an invalid IP.
+var ErrInvalidIP = bittorrent.ClientError("invalid IP")
+
 var promResponseDurationMilliseconds = prometheus.NewHistogramVec(
 	prometheus.HistogramOpts{
 		Name:    "chihaya_http_response_duration_milliseconds",
@@ -172,8 +176,19 @@ func (t *Frontend) scrapeRoute(w http.ResponseWriter, r *http.Request, _ httprou
 		return
 	}
 
-	ip := net.ParseIP(host)
-	ctx := context.WithValue(context.Background(), middleware.ScrapeIsIPv6Key, len(ip) == net.IPv6len)
+	reqIP := net.ParseIP(host)
+	af := bittorrent.IPv4
+	if reqIP.To4() != nil {
+		af = bittorrent.IPv4
+	} else if len(reqIP) == net.IPv6len { // implies reqIP.To4() == nil
+		af = bittorrent.IPv6
+	} else {
+		log.Errorln("http: invalid IP: neither v4 nor v6, RemoteAddr was", r.RemoteAddr)
+		WriteError(w, ErrInvalidIP)
+		return
+	}
+
+	ctx := context.WithValue(context.Background(), middleware.ScrapeIsIPv6Key, af == bittorrent.IPv6)
 
 	resp, err := t.logic.HandleScrape(ctx, req)
 	if err != nil {

frontend/http/parser.go

@@ -74,16 +74,11 @@ func ParseAnnounce(r *http.Request, realIPHeader string, allowIPSpoofing bool) (
 	}
 	request.Peer.Port = uint16(port)
 
-	request.Peer.IP = requestedIP(r, qp, realIPHeader, allowIPSpoofing)
-	if request.Peer.IP == nil {
+	request.Peer.IP.IP = requestedIP(r, qp, realIPHeader, allowIPSpoofing)
+	if request.Peer.IP.IP == nil {
 		return nil, bittorrent.ClientError("failed to parse peer IP address")
 	}
 
-	// Sanitize IPv4 addresses to 4 bytes.
-	if ip := request.Peer.IP.To4(); ip != nil {
-		request.Peer.IP = ip
-	}
-
 	return request, nil
 }
 

frontend/udp/frontend.go

@@ -10,6 +10,7 @@ import (
 	"sync"
 	"time"
 
+	log "github.com/Sirupsen/logrus"
 	"github.com/prometheus/client_golang/prometheus"
 
 	"github.com/chihaya/chihaya/bittorrent"
@@ -23,6 +24,9 @@ func init() {
 	recordResponseDuration("action", nil, time.Second)
 }
 
+// ErrInvalidIP indicates an invalid IP.
+var ErrInvalidIP = bittorrent.ClientError("invalid IP")
+
 var promResponseDurationMilliseconds = prometheus.NewHistogramVec(
 	prometheus.HistogramOpts{
 		Name:    "chihaya_udp_response_duration_milliseconds",
@@ -228,7 +232,18 @@ func (t *Frontend) handleRequest(r Request, w ResponseWriter) (actionName string
 			return
 		}
 
-		ctx := context.WithValue(context.Background(), middleware.ScrapeIsIPv6Key, len(r.IP) == net.IPv6len)
+		af := bittorrent.IPv4
+		if r.IP.To4() != nil {
+			af = bittorrent.IPv4
+		} else if len(r.IP) == net.IPv6len { // implies r.IP.To4() == nil
+			af = bittorrent.IPv6
+		} else {
+			log.Errorln("http: invalid IP: neither v4 nor v6, IP was", r.IP)
+			WriteError(w, txID, ErrInvalidIP)
+			return
+		}
+
+		ctx := context.WithValue(context.Background(), middleware.ScrapeIsIPv6Key, af == bittorrent.IPv6)
 
 		var resp *bittorrent.ScrapeResponse
 		resp, err = t.logic.HandleScrape(ctx, req)

frontend/udp/parser.go

@@ -29,10 +29,6 @@ var (
 	// initialConnectionID is the magic initial connection ID specified by BEP 15.
 	initialConnectionID = []byte{0, 0, 0x04, 0x17, 0x27, 0x10, 0x19, 0x80}
 
-	// emptyIPs are the value of an IP field that has been left blank.
-	emptyIPv4 = []byte{0, 0, 0, 0}
-	emptyIPv6 = []byte{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0}
-
 	// eventIDs map values described in BEP 15 to Events.
 	eventIDs = []bittorrent.Event{
 		bittorrent.None,
@@ -105,7 +101,7 @@ func ParseAnnounce(r Request, allowIPSpoofing, v6 bool) (*bittorrent.AnnounceReq
 		Uploaded:   uploaded,
 		Peer: bittorrent.Peer{
 			ID:   bittorrent.PeerIDFromBytes(peerID),
-			IP:   ip,
+			IP:   bittorrent.IP{IP: ip},
 			Port: port,
 		},
 		Params: params,

frontend/udp/writer.go

@@ -46,7 +46,7 @@ func WriteAnnounce(w io.Writer, txID []byte, resp *bittorrent.AnnounceResponse,
 	}
 
 	for _, peer := range peers {
-		buf.Write(peer.IP)
+		buf.Write(peer.IP.IP)
 		binary.Write(buf, binary.BigEndian, peer.Port)
 	}