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Encode client-broker messages as json in HTTP body

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Send the client poll request and response in a json-encoded format in
the HTTP request body rather than sending the data in HTTP headers. This
will pave the way for using domain-fronting alternatives for the
Snowflake rendezvous.
This commit is contained in:
Cecylia Bocovich 2021-05-05 15:31:39 -04:00
parent ae7cc478fd
commit 270eb21803
7 changed files with 472 additions and 63 deletions
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36
client/lib/rendezvous.go
View file

@ -19,14 +19,13 @@ import (
"sync"
"time"
"git.torproject.org/pluggable-transports/snowflake.git/common/messages"
"git.torproject.org/pluggable-transports/snowflake.git/common/nat"
"git.torproject.org/pluggable-transports/snowflake.git/common/util"
"github.com/pion/webrtc/v3"
)
const (
BrokerError503 string = "No snowflake proxies currently available."
BrokerError400 string = "You sent an invalid offer in the request."
BrokerErrorUnexpected string = "Unexpected error, no answer."
readLimit = 100000 //Maximum number of bytes to be read from an HTTP response
)
@ -107,7 +106,20 @@ func (bc *BrokerChannel) Negotiate(offer *webrtc.SessionDescription) (
if err != nil {
return nil, err
}
data := bytes.NewReader([]byte(offerSDP))
// Encode client poll request
bc.lock.Lock()
req := &messages.ClientPollRequest{
Offer: offerSDP,
NAT: bc.NATType,
}
body, err := req.EncodePollRequest()
bc.lock.Unlock()
if err != nil {
return nil, err
}
data := bytes.NewReader([]byte(body))
// Suffix with broker's client registration handler.
clientURL := bc.url.ResolveReference(&url.URL{Path: "client"})
request, err := http.NewRequest("POST", clientURL.String(), data)
@ -117,10 +129,6 @@ func (bc *BrokerChannel) Negotiate(offer *webrtc.SessionDescription) (
if "" != bc.Host { // Set true host if necessary.
request.Host = bc.Host
}
// include NAT-TYPE
bc.lock.Lock()
request.Header.Set("Snowflake-NAT-TYPE", bc.NATType)
bc.lock.Unlock()
resp, err := bc.transport.RoundTrip(request)
if nil != err {
return nil, err
@ -135,11 +143,15 @@ func (bc *BrokerChannel) Negotiate(offer *webrtc.SessionDescription) (
return nil, err
}
log.Printf("Received answer: %s", string(body))
return util.DeserializeSessionDescription(string(body))
case http.StatusServiceUnavailable:
return nil, errors.New(BrokerError503)
case http.StatusBadRequest:
return nil, errors.New(BrokerError400)
resp, err := messages.DecodeClientPollResponse(body)
if err != nil {
return nil, err
}
if resp.Error != "" {
return nil, errors.New(resp.Error)
}
return util.DeserializeSessionDescription(resp.Answer)
default:
return nil, errors.New(BrokerErrorUnexpected)
}