[tor-commits] [snowflake/master] Remove local LAN address ICE candidates
arlo at torproject.org
arlo at torproject.org
Sat Feb 8 15:14:45 UTC 2020
commit 0fae4ee8ea487c3b4384217e193e5b9a9088e7de
Author: Arlo Breault <arlolra at gmail.com>
Date: Fri Jan 31 00:17:50 2020 -0500
Remove local LAN address ICE candidates
Unfortunately, the "public" RTCIceTransportPolicy was removed.
https://developer.mozilla.org/en-US/docs/Web/API/RTCConfiguration#RTCIceTransportPolicy_enum
Trac: 19026
---
client/lib/lib_test.go | 35 +++++++++++++++++++++------
client/lib/rendezvous.go | 63 ++++++++++++++++++++++++++++++++++++++++++++----
client/snowflake.go | 3 ++-
client/torrc-localhost | 1 +
4 files changed, 89 insertions(+), 13 deletions(-)
diff --git a/client/lib/lib_test.go b/client/lib/lib_test.go
index 91a9809..adfc9ec 100644
--- a/client/lib/lib_test.go
+++ b/client/lib/lib_test.go
@@ -288,7 +288,7 @@ func TestSnowflakeClient(t *testing.T) {
fakeOffer := deserializeSessionDescription(`{"type":"offer","sdp":"test"}`)
Convey("Construct BrokerChannel with no front domain", func() {
- b, err := NewBrokerChannel("test.broker", "", transport)
+ b, err := NewBrokerChannel("test.broker", "", transport, false)
So(b.url, ShouldNotBeNil)
So(err, ShouldBeNil)
So(b.url.Path, ShouldResemble, "test.broker")
@@ -296,7 +296,7 @@ func TestSnowflakeClient(t *testing.T) {
})
Convey("Construct BrokerChannel *with* front domain", func() {
- b, err := NewBrokerChannel("test.broker", "front", transport)
+ b, err := NewBrokerChannel("test.broker", "front", transport, false)
So(b.url, ShouldNotBeNil)
So(err, ShouldBeNil)
So(b.url.Path, ShouldResemble, "test.broker")
@@ -305,7 +305,7 @@ func TestSnowflakeClient(t *testing.T) {
})
Convey("BrokerChannel.Negotiate responds with answer", func() {
- b, err := NewBrokerChannel("test.broker", "", transport)
+ b, err := NewBrokerChannel("test.broker", "", transport, false)
So(err, ShouldBeNil)
answer, err := b.Negotiate(fakeOffer)
So(err, ShouldBeNil)
@@ -315,7 +315,8 @@ func TestSnowflakeClient(t *testing.T) {
Convey("BrokerChannel.Negotiate fails with 503", func() {
b, err := NewBrokerChannel("test.broker", "",
- &MockTransport{http.StatusServiceUnavailable, []byte("\n")})
+ &MockTransport{http.StatusServiceUnavailable, []byte("\n")},
+ false)
So(err, ShouldBeNil)
answer, err := b.Negotiate(fakeOffer)
So(err, ShouldNotBeNil)
@@ -325,7 +326,8 @@ func TestSnowflakeClient(t *testing.T) {
Convey("BrokerChannel.Negotiate fails with 400", func() {
b, err := NewBrokerChannel("test.broker", "",
- &MockTransport{http.StatusBadRequest, []byte("\n")})
+ &MockTransport{http.StatusBadRequest, []byte("\n")},
+ false)
So(err, ShouldBeNil)
answer, err := b.Negotiate(fakeOffer)
So(err, ShouldNotBeNil)
@@ -335,7 +337,8 @@ func TestSnowflakeClient(t *testing.T) {
Convey("BrokerChannel.Negotiate fails with large read", func() {
b, err := NewBrokerChannel("test.broker", "",
- &MockTransport{http.StatusOK, make([]byte, 100001, 100001)})
+ &MockTransport{http.StatusOK, make([]byte, 100001, 100001)},
+ false)
So(err, ShouldBeNil)
answer, err := b.Negotiate(fakeOffer)
So(err, ShouldNotBeNil)
@@ -345,7 +348,7 @@ func TestSnowflakeClient(t *testing.T) {
Convey("BrokerChannel.Negotiate fails with unexpected error", func() {
b, err := NewBrokerChannel("test.broker", "",
- &MockTransport{123, []byte("")})
+ &MockTransport{123, []byte("")}, false)
So(err, ShouldBeNil)
answer, err := b.Negotiate(fakeOffer)
So(err, ShouldNotBeNil)
@@ -353,4 +356,22 @@ func TestSnowflakeClient(t *testing.T) {
So(err.Error(), ShouldResemble, BrokerErrorUnexpected)
})
})
+
+ Convey("Strip", t, func() {
+ const offerStart = `{"type":"offer","sdp":"v=0\r\no=- 4358805017720277108 2 IN IP4 8.8.8.8\r\ns=-\r\nt=0 0\r\na=group:BUNDLE data\r\na=msid-semantic: WMS\r\nm=application 56688 DTLS/SCTP 5000\r\nc=IN IP4 8.8.8.8\r\n`
+ const goodCandidate = `a=candidate:3769337065 1 udp 2122260223 8.8.8.8 56688 typ host generation 0 network-id 1 network-cost 50\r\n`
+ const offerEnd = `a=ice-ufrag:aMAZ\r\na=ice-pwd:jcHb08Jjgrazp2dzjdrvPPvV\r\na=ice-options:trickle\r\na=fingerprint:sha-256 C8:88:EE:B9:E7:02:2E:21:37:ED:7A:D1:EB:2B:A3:15:A2:3B:5B:1C:3D:D4:D5:1F:06:CF:52:40:03:F8:DD:66\r\na=setup:actpass\r\na=mid:data\r\na=sctpmap:5000 webrtc-datachannel 1024\r\n"}`
+
+ offer := offerStart + goodCandidate +
+ `a=candidate:3769337065 1 udp 2122260223 192.168.0.100 56688 typ host generation 0 network-id 1 network-cost 50\r\n` + // IsLocal IPv4
+ `a=candidate:3769337065 1 udp 2122260223 fdf8:f53b:82e4::53 56688 typ host generation 0 network-id 1 network-cost 50\r\n` + // IsLocal IPv6
+ `a=candidate:3769337065 1 udp 2122260223 0.0.0.0 56688 typ host generation 0 network-id 1 network-cost 50\r\n` + // IsUnspecified IPv4
+ `a=candidate:3769337065 1 udp 2122260223 :: 56688 typ host generation 0 network-id 1 network-cost 50\r\n` + // IsUnspecified IPv6
+ `a=candidate:3769337065 1 udp 2122260223 127.0.0.1 56688 typ host generation 0 network-id 1 network-cost 50\r\n` + // IsLoopback IPv4
+ `a=candidate:3769337065 1 udp 2122260223 ::1 56688 typ host generation 0 network-id 1 network-cost 50\r\n` + // IsLoopback IPv6
+ offerEnd
+
+ So(stripLocalAddresses(offer), ShouldEqual, offerStart+goodCandidate+offerEnd)
+ })
+
}
diff --git a/client/lib/rendezvous.go b/client/lib/rendezvous.go
index d117ebc..bd8ff00 100644
--- a/client/lib/rendezvous.go
+++ b/client/lib/rendezvous.go
@@ -14,9 +14,12 @@ import (
"io"
"io/ioutil"
"log"
+ "net"
"net/http"
"net/url"
+ "regexp"
+ "github.com/pion/sdp"
"github.com/pion/webrtc"
)
@@ -31,9 +34,10 @@ const (
type BrokerChannel struct {
// The Host header to put in the HTTP request (optional and may be
// different from the host name in URL).
- Host string
- url *url.URL
- transport http.RoundTripper // Used to make all requests.
+ Host string
+ url *url.URL
+ transport http.RoundTripper // Used to make all requests.
+ keepLocalAddresses bool
}
// We make a copy of DefaultTransport because we want the default Dial
@@ -48,7 +52,7 @@ func CreateBrokerTransport() http.RoundTripper {
// Construct a new BrokerChannel, where:
// |broker| is the full URL of the facilitating program which assigns proxies
// to clients, and |front| is the option fronting domain.
-func NewBrokerChannel(broker string, front string, transport http.RoundTripper) (*BrokerChannel, error) {
+func NewBrokerChannel(broker string, front string, transport http.RoundTripper, keepLocalAddresses bool) (*BrokerChannel, error) {
targetURL, err := url.Parse(broker)
if err != nil {
return nil, err
@@ -63,6 +67,7 @@ func NewBrokerChannel(broker string, front string, transport http.RoundTripper)
}
bc.transport = transport
+ bc.keepLocalAddresses = keepLocalAddresses
return bc, nil
}
@@ -76,6 +81,41 @@ func limitedRead(r io.Reader, limit int64) ([]byte, error) {
return p, err
}
+// Stolen from https://github.com/golang/go/pull/30278
+func IsLocal(ip net.IP) bool {
+ if ip4 := ip.To4(); ip4 != nil {
+ // Local IPv4 addresses are defined in https://tools.ietf.org/html/rfc1918
+ return ip4[0] == 10 ||
+ (ip4[0] == 172 && ip4[1]&0xf0 == 16) ||
+ (ip4[0] == 192 && ip4[1] == 168)
+ }
+ // Local IPv6 addresses are defined in https://tools.ietf.org/html/rfc4193
+ return len(ip) == net.IPv6len && ip[0]&0xfe == 0xfc
+}
+
+// Removes local LAN address ICE candidates
+func stripLocalAddresses(str string) string {
+ re := regexp.MustCompile(`a=candidate:.*?\\r\\n`)
+ return re.ReplaceAllStringFunc(str, func(s string) string {
+ t := s[len("a=candidate:") : len(s)-len("\\r\\n")]
+ var ice sdp.ICECandidate
+ err := ice.Unmarshal(t)
+ if err != nil {
+ return s
+ }
+ if ice.Typ == "host" {
+ ip := net.ParseIP(ice.Address)
+ if ip == nil {
+ return s
+ }
+ if IsLocal(ip) || ip.IsUnspecified() || ip.IsLoopback() {
+ return ""
+ }
+ }
+ return s
+ })
+}
+
// Roundtrip HTTP POST using WebRTC SessionDescriptions.
//
// Send an SDP offer to the broker, which assigns a proxy and responds
@@ -84,7 +124,20 @@ func (bc *BrokerChannel) Negotiate(offer *webrtc.SessionDescription) (
*webrtc.SessionDescription, error) {
log.Println("Negotiating via BrokerChannel...\nTarget URL: ",
bc.Host, "\nFront URL: ", bc.url.Host)
- data := bytes.NewReader([]byte(serializeSessionDescription(offer)))
+ str := serializeSessionDescription(offer)
+ // Ideally, we could specify an `RTCIceTransportPolicy` that would handle
+ // this for us. However, "public" was removed from the draft spec.
+ // See https://developer.mozilla.org/en-US/docs/Web/API/RTCConfiguration#RTCIceTransportPolicy_enum
+ //
+ // FIXME: We are stripping local addresses from the JSON serialized string,
+ // which is expedient but unsatisfying. We could advocate upstream to
+ // implement a non-standard ICE transport policy, or to somehow alter
+ // APIs to avoid adding the undesirable candidates or a method to filter
+ // them from the marshalled session description.
+ if !bc.keepLocalAddresses {
+ str = stripLocalAddresses(str)
+ }
+ data := bytes.NewReader([]byte(str))
// Suffix with broker's client registration handler.
clientURL := bc.url.ResolveReference(&url.URL{Path: "client"})
request, err := http.NewRequest("POST", clientURL.String(), data)
diff --git a/client/snowflake.go b/client/snowflake.go
index edcbd4a..7cf8a9d 100644
--- a/client/snowflake.go
+++ b/client/snowflake.go
@@ -90,6 +90,7 @@ func main() {
frontDomain := flag.String("front", "", "front domain")
logFilename := flag.String("log", "", "name of log file")
logToStateDir := flag.Bool("logToStateDir", false, "resolve the log file relative to tor's pt state dir")
+ keepLocalAddresses := flag.Bool("keepLocalAddresses", false, "keep local LAN address ICE candidates")
max := flag.Int("max", DefaultSnowflakeCapacity,
"capacity for number of multiplexed WebRTC peers")
flag.Parse()
@@ -133,7 +134,7 @@ func main() {
snowflakes := sf.NewPeers(*max)
// Use potentially domain-fronting broker to rendezvous.
- broker, err := sf.NewBrokerChannel(*brokerURL, *frontDomain, sf.CreateBrokerTransport())
+ broker, err := sf.NewBrokerChannel(*brokerURL, *frontDomain, sf.CreateBrokerTransport(), *keepLocalAddresses)
if err != nil {
log.Fatalf("parsing broker URL: %v", err)
}
diff --git a/client/torrc-localhost b/client/torrc-localhost
index 7d539fb..9afb033 100644
--- a/client/torrc-localhost
+++ b/client/torrc-localhost
@@ -3,5 +3,6 @@ DataDirectory datadir
ClientTransportPlugin snowflake exec ./client \
-url http://localhost:8080/ \
+-keepLocalAddresses
Bridge snowflake 0.0.3.0:1
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