[tor-commits] [snowflake/master] Pass client IP from proxy-go to server by parsing SDP
dcf at torproject.org
dcf at torproject.org
Sat Oct 14 19:12:34 UTC 2017
commit ae0643320e30fb1d9b825c779fdfa0ae2d2ac190
Author: Hooman <hoomanm at princeton.edu>
Date: Thu Jul 20 16:39:28 2017 -0700
Pass client IP from proxy-go to server by parsing SDP
Call conn.RemoteAddr() before entering the datachannelHandler goroutine.
This is a workaround for the hang described at
https://bugs.torproject.org/18628#comment:8
---
proxy-go/snowflake.go | 54 ++++++++++++++++++++++--
proxy-go/webrtc_test.go | 109 ++++++++++++++++++++++++++++++++++++++++++++++++
2 files changed, 159 insertions(+), 4 deletions(-)
diff --git a/proxy-go/snowflake.go b/proxy-go/snowflake.go
index 33becb3..1273474 100644
--- a/proxy-go/snowflake.go
+++ b/proxy-go/snowflake.go
@@ -13,6 +13,7 @@ import (
"net/http"
"net/url"
"os"
+ "regexp"
"strings"
"sync"
"time"
@@ -38,6 +39,25 @@ var (
client http.Client
)
+var remoteIPPatterns = []*regexp.Regexp{
+ /* IPv4 */
+ regexp.MustCompile(`(?m)^c=IN IP4 ([\d.]+)(?:(?:\/\d+)?\/\d+)?(:? |\r?\n)`),
+ /* IPv6 */
+ regexp.MustCompile(`(?m)^c=IN IP6 ([0-9A-Fa-f:.]+)(?:\/\d+)?(:? |\r?\n)`),
+}
+
+// https://tools.ietf.org/html/rfc4566#section-5.7
+func remoteIPFromSDP(sdp string) net.IP {
+ for _, pattern := range remoteIPPatterns {
+ m := pattern.FindStringSubmatch(sdp)
+ if m != nil {
+ // Ignore parsing errors, ParseIP returns nil.
+ return net.ParseIP(m[1])
+ }
+ }
+ return nil
+}
+
type webRTCConn struct {
dc *webrtc.DataChannel
pc *webrtc.PeerConnection
@@ -64,7 +84,12 @@ func (c *webRTCConn) LocalAddr() net.Addr {
}
func (c *webRTCConn) RemoteAddr() net.Addr {
- return nil
+ //Parse Remote SDP offer and extract client IP
+ clientIP := remoteIPFromSDP(c.pc.RemoteDescription().Sdp)
+ if clientIP == nil {
+ return nil
+ }
+ return &net.IPAddr{clientIP, ""}
}
func (c *webRTCConn) SetDeadline(t time.Time) error {
@@ -181,11 +206,31 @@ func CopyLoopTimeout(c1 net.Conn, c2 net.Conn, timeout time.Duration) {
wg.Wait()
}
-func datachannelHandler(conn *webRTCConn) {
+// We pass conn.RemoteAddr() as an additional parameter, rather than calling
+// conn.RemoteAddr() inside this function, as a workaround for a hang that
+// otherwise occurs inside of conn.pc.RemoteDescription() (called by
+// RemoteAddr). https://bugs.torproject.org/18628#comment:8
+func datachannelHandler(conn *webRTCConn, remoteAddr net.Addr) {
defer conn.Close()
defer retToken()
- wsConn, err := websocket.Dial(relayURL, "", relayURL)
+ u, err := url.Parse(relayURL)
+ if err != nil {
+ log.Fatalf("invalid relay url: %s", err)
+ }
+
+ // Retrieve client IP address
+ if remoteAddr != nil {
+ // Encode client IP address in relay URL
+ q := u.Query()
+ clientIP := remoteAddr.String()
+ q.Set("client_ip", clientIP)
+ u.RawQuery = q.Encode()
+ } else {
+ log.Printf("no remote address given in websocket")
+ }
+
+ wsConn, err := websocket.Dial(u.String(), "", relayURL)
if err != nil {
log.Printf("error dialing relay: %s", err)
return
@@ -237,8 +282,9 @@ func makePeerConnectionFromOffer(sdp *webrtc.SessionDescription, config *webrtc.
panic("short write")
}
}
+
conn := &webRTCConn{pc: pc, dc: dc, pr: pr}
- go datachannelHandler(conn)
+ go datachannelHandler(conn, conn.RemoteAddr())
}
err = pc.SetRemoteDescription(sdp)
diff --git a/proxy-go/webrtc_test.go b/proxy-go/webrtc_test.go
new file mode 100644
index 0000000..2413207
--- /dev/null
+++ b/proxy-go/webrtc_test.go
@@ -0,0 +1,109 @@
+package main
+
+import (
+ "net"
+ "strings"
+ "testing"
+)
+
+func TestRemoteIPFromSDP(t *testing.T) {
+ tests := []struct {
+ sdp string
+ expected net.IP
+ }{
+ // https://tools.ietf.org/html/rfc4566#section-5
+ {`v=0
+o=jdoe 2890844526 2890842807 IN IP4 10.47.16.5
+s=SDP Seminar
+i=A Seminar on the session description protocol
+u=http://www.example.com/seminars/sdp.pdf
+e=j.doe at example.com (Jane Doe)
+c=IN IP4 224.2.17.12/127
+t=2873397496 2873404696
+a=recvonly
+m=audio 49170 RTP/AVP 0
+m=video 51372 RTP/AVP 99
+a=rtpmap:99 h263-1998/90000
+`, net.ParseIP("224.2.17.12")},
+ // Missing c= line
+ {`v=0
+o=jdoe 2890844526 2890842807 IN IP4 10.47.16.5
+s=SDP Seminar
+i=A Seminar on the session description protocol
+u=http://www.example.com/seminars/sdp.pdf
+e=j.doe at example.com (Jane Doe)
+t=2873397496 2873404696
+a=recvonly
+m=audio 49170 RTP/AVP 0
+m=video 51372 RTP/AVP 99
+a=rtpmap:99 h263-1998/90000
+`, nil},
+ // Single line, IP address only
+ {`c=IN IP4 224.2.1.1
+`, net.ParseIP("224.2.1.1")},
+ // Same, with TTL
+ {`c=IN IP4 224.2.1.1/127
+`, net.ParseIP("224.2.1.1")},
+ // Same, with TTL and multicast addresses
+ {`c=IN IP4 224.2.1.1/127/3
+`, net.ParseIP("224.2.1.1")},
+ // IPv6, address only
+ {`c=IN IP6 FF15::101
+`, net.ParseIP("ff15::101")},
+ // Same, with multicast addresses
+ {`c=IN IP6 FF15::101/3
+`, net.ParseIP("ff15::101")},
+ // Multiple c= lines
+ {`c=IN IP4 1.2.3.4
+c=IN IP4 5.6.7.8
+`, net.ParseIP("1.2.3.4")},
+ // Modified from SDP sent by snowflake-client.
+ {`v=0
+o=- 7860378660295630295 2 IN IP4 127.0.0.1
+s=-
+t=0 0
+a=group:BUNDLE data
+a=msid-semantic: WMS
+m=application 54653 DTLS/SCTP 5000
+c=IN IP4 1.2.3.4
+a=candidate:3581707038 1 udp 2122260223 192.168.0.1 54653 typ host generation 0 network-id 1 network-cost 50
+a=candidate:2617212910 1 tcp 1518280447 192.168.0.1 59673 typ host tcptype passive generation 0 network-id 1 network-cost 50
+a=candidate:2082671819 1 udp 1686052607 1.2.3.4 54653 typ srflx raddr 192.168.0.1 rport 54653 generation 0 network-id 1 network-cost 50
+a=ice-ufrag:IBdf
+a=ice-pwd:G3lTrrC9gmhQx481AowtkhYz
+a=fingerprint:sha-256 53:F8:84:D9:3C:1F:A0:44:AA:D6:3C:65:80:D3:CB:6F:23:90:17:41:06:F9:9C:10:D8:48:4A:A8:B6:FA:14:A1
+a=setup:actpass
+a=mid:data
+a=sctpmap:5000 webrtc-datachannel 1024
+`, net.ParseIP("1.2.3.4")},
+ // Improper character within IPv4
+ {`c=IN IP4 224.2z.1.1
+`, nil},
+ // Improper character within IPv6
+ {`c=IN IP6 ff15:g::101
+`, nil},
+ // Bogus "IP7" addrtype
+ {`c=IN IP7 1.2.3.4
+`, nil},
+ }
+
+ for _, test := range tests {
+ // https://tools.ietf.org/html/rfc4566#section-5: "The sequence
+ // CRLF (0x0d0a) is used to end a record, although parsers
+ // SHOULD be tolerant and also accept records terminated with a
+ // single newline character." We represent the test cases with
+ // LF line endings for convenience, and test them both that way
+ // and with CRLF line endings.
+ lfSDP := test.sdp
+ crlfSDP := strings.Replace(lfSDP, "\n", "\r\n", -1)
+
+ ip := remoteIPFromSDP(lfSDP)
+ if !ip.Equal(test.expected) {
+ t.Errorf("expected %q, got %q from %q", test.expected, ip, lfSDP)
+ }
+ ip = remoteIPFromSDP(crlfSDP)
+ if !ip.Equal(test.expected) {
+ t.Errorf("expected %q, got %q from %q", test.expected, ip, crlfSDP)
+ }
+ }
+}
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