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Extract remote address from ICE candidates

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Parse the received ICE candidates as well as the Connection Data
field for a non-local IP address to pass to the bridge. This fixes
bug #33157.
This commit is contained in:
Cecylia Bocovich 2020-09-30 10:10:29 -04:00
parent 8467c01e9e
commit d7aa9b8356
2 changed files with 157 additions and 16 deletions
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47
proxy/snowflake.go
View file

@ -24,6 +24,7 @@ import (
"git.torproject.org/pluggable-transports/snowflake.git/common/util"
"git.torproject.org/pluggable-transports/snowflake.git/common/websocketconn"
"github.com/gorilla/websocket"
"github.com/pion/sdp/v2"
"github.com/pion/webrtc/v2"
)
@ -65,15 +66,47 @@ var remoteIPPatterns = []*regexp.Regexp{
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])
// Checks whether an IP address is a remote address for the client
func isRemoteAddress(ip net.IP) bool {
return !(util.IsLocal(ip) || ip.IsUnspecified() || ip.IsLoopback())
}
func remoteIPFromSDP(str string) net.IP {
// Look for remote IP in "a=candidate" attribute fields
// https://tools.ietf.org/html/rfc5245#section-15.1
var desc sdp.SessionDescription
err := desc.Unmarshal([]byte(str))
if err != nil {
log.Println("Error parsing SDP: ", err.Error())
return nil
}
for _, m := range desc.MediaDescriptions {
for _, a := range m.Attributes {
if a.IsICECandidate() {
ice, err := a.ToICECandidate()
if err == nil {
ip := net.ParseIP(ice.Address)
if ip != nil && isRemoteAddress(ip) {
return ip
}
}
}
}
}
// Finally look for remote IP in "c=" Connection Data field
// https://tools.ietf.org/html/rfc4566#section-5.7
for _, pattern := range remoteIPPatterns {
m := pattern.FindStringSubmatch(str)
if m != nil {
// Ignore parsing errors, ParseIP returns nil.
ip := net.ParseIP(m[1])
if ip != nil && isRemoteAddress(ip) {
return ip
}
}
}
return nil
}