Commit a2af6fb4 authored by David Fifield's avatar David Fifield
Browse files

Implement ampCacheRendezvous.

parent 06ca0e86
package lib
import (
"bytes"
"errors"
"io"
"io/ioutil"
"log"
"net/http"
"net/url"
"git.torproject.org/pluggable-transports/snowflake.git/common/amp"
)
// ampCacheRendezvous is a rendezvousMethod that communicates with the
......@@ -49,9 +52,22 @@ func (r *ampCacheRendezvous) Exchange(encPollReq []byte) ([]byte, error) {
log.Println("AMP cache URL:", r.cacheURL)
log.Println("Front domain:", r.front)
// Suffix the path with the broker's client registration handler.
reqURL := r.brokerURL.ResolveReference(&url.URL{Path: "client"})
req, err := http.NewRequest("POST", reqURL.String(), bytes.NewReader(encPollReq))
// We cannot POST a body through an AMP cache, so instead we GET and
// encode the client poll request message into the URL.
reqURL := r.brokerURL.ResolveReference(&url.URL{
Path: "amp/client/" + amp.EncodePath(encPollReq),
})
if r.cacheURL != nil {
// Rewrite reqURL to its AMP cache version.
var err error
reqURL, err = amp.CacheURL(reqURL, r.cacheURL, "c")
if err != nil {
return nil, err
}
}
req, err := http.NewRequest("GET", reqURL.String(), nil)
if err != nil {
return nil, err
}
......@@ -71,8 +87,38 @@ func (r *ampCacheRendezvous) Exchange(encPollReq []byte) ([]byte, error) {
log.Printf("AMP cache rendezvous response: %s", resp.Status)
if resp.StatusCode != http.StatusOK {
// A non-200 status indicates an error:
// * If the broker returns a page with invalid AMP, then the AMP
// cache returns a redirect that would bypass the cache.
// * If the broker returns a 5xx status, the AMP cache
// translates it to a 404.
// https://amp.dev/documentation/guides-and-tutorials/learn/amp-caches-and-cors/amp-cache-urls/#redirect-%26-error-handling
return nil, errors.New(BrokerErrorUnexpected)
}
if _, err := resp.Location(); err == nil {
// The Google AMP Cache may return a "silent redirect" with
// status 200, a Location header set, and a JavaScript redirect
// in the body. The redirect points directly at the origin
// server for the request (bypassing the AMP cache). We do not
// follow redirects nor execute JavaScript, but in any case we
// cannot extract information from this response and can only
// treat it as an error.
return nil, errors.New(BrokerErrorUnexpected)
}
return limitedRead(resp.Body, readLimit)
lr := io.LimitReader(resp.Body, readLimit+1)
dec, err := amp.NewArmorDecoder(lr)
if err != nil {
return nil, err
}
encPollResp, err := ioutil.ReadAll(dec)
if err != nil {
return nil, err
}
if lr.(*io.LimitedReader).N == 0 {
// We hit readLimit while decoding AMP armor, that's an error.
return nil, io.ErrUnexpectedEOF
}
return encPollResp, err
}
......@@ -9,6 +9,7 @@ import (
"net/http"
"testing"
"git.torproject.org/pluggable-transports/snowflake.git/common/amp"
"git.torproject.org/pluggable-transports/snowflake.git/common/messages"
"git.torproject.org/pluggable-transports/snowflake.git/common/nat"
. "github.com/smartystreets/goconvey/convey"
......@@ -64,6 +65,8 @@ func makeEncPollResp(answer, errorStr string) []byte {
return encPollResp
}
var fakeEncPollReq = makeEncPollReq(`{"type":"offer","sdp":"test"}`)
func TestHTTPRendezvous(t *testing.T) {
Convey("HTTP rendezvous", t, func() {
Convey("Construct httpRendezvous with no front domain", func() {
......@@ -86,8 +89,6 @@ func TestHTTPRendezvous(t *testing.T) {
So(rend.transport, ShouldEqual, transport)
})
fakeEncPollReq := makeEncPollReq(`{"type":"offer","sdp":"test"}`)
Convey("httpRendezvous.Exchange responds with answer", func() {
fakeEncPollResp := makeEncPollResp(
`{"answer": "{\"type\":\"answer\",\"sdp\":\"fake\"}" }`,
......@@ -143,3 +144,130 @@ func TestHTTPRendezvous(t *testing.T) {
})
})
}
func ampArmorEncode(p []byte) []byte {
var buf bytes.Buffer
enc, err := amp.NewArmorEncoder(&buf)
if err != nil {
panic(err)
}
_, err = enc.Write(p)
if err != nil {
panic(err)
}
err = enc.Close()
if err != nil {
panic(err)
}
return buf.Bytes()
}
func TestAMPCacheRendezvous(t *testing.T) {
Convey("AMP cache rendezvous", t, func() {
Convey("Construct ampCacheRendezvous with no cache and no front domain", func() {
transport := &mockTransport{http.StatusOK, []byte{}}
rend, err := newAMPCacheRendezvous("http://test.broker", "", "", transport)
So(err, ShouldBeNil)
So(rend.brokerURL, ShouldNotBeNil)
So(rend.brokerURL.String(), ShouldResemble, "http://test.broker")
So(rend.cacheURL, ShouldBeNil)
So(rend.front, ShouldResemble, "")
So(rend.transport, ShouldEqual, transport)
})
Convey("Construct ampCacheRendezvous with cache and no front domain", func() {
transport := &mockTransport{http.StatusOK, []byte{}}
rend, err := newAMPCacheRendezvous("http://test.broker", "https://amp.cache/", "", transport)
So(err, ShouldBeNil)
So(rend.brokerURL, ShouldNotBeNil)
So(rend.brokerURL.String(), ShouldResemble, "http://test.broker")
So(rend.cacheURL, ShouldNotBeNil)
So(rend.cacheURL.String(), ShouldResemble, "https://amp.cache/")
So(rend.front, ShouldResemble, "")
So(rend.transport, ShouldEqual, transport)
})
Convey("Construct ampCacheRendezvous with no cache and front domain", func() {
transport := &mockTransport{http.StatusOK, []byte{}}
rend, err := newAMPCacheRendezvous("http://test.broker", "", "front", transport)
So(err, ShouldBeNil)
So(rend.brokerURL, ShouldNotBeNil)
So(rend.brokerURL.String(), ShouldResemble, "http://test.broker")
So(rend.cacheURL, ShouldBeNil)
So(rend.front, ShouldResemble, "front")
So(rend.transport, ShouldEqual, transport)
})
Convey("Construct ampCacheRendezvous with cache and front domain", func() {
transport := &mockTransport{http.StatusOK, []byte{}}
rend, err := newAMPCacheRendezvous("http://test.broker", "https://amp.cache/", "front", transport)
So(err, ShouldBeNil)
So(rend.brokerURL, ShouldNotBeNil)
So(rend.brokerURL.String(), ShouldResemble, "http://test.broker")
So(rend.cacheURL, ShouldNotBeNil)
So(rend.cacheURL.String(), ShouldResemble, "https://amp.cache/")
So(rend.front, ShouldResemble, "front")
So(rend.transport, ShouldEqual, transport)
})
Convey("ampCacheRendezvous.Exchange responds with answer", func() {
fakeEncPollResp := makeEncPollResp(
`{"answer": "{\"type\":\"answer\",\"sdp\":\"fake\"}" }`,
"",
)
rend, err := newAMPCacheRendezvous("http://test.broker", "", "",
&mockTransport{http.StatusOK, ampArmorEncode(fakeEncPollResp)})
So(err, ShouldBeNil)
answer, err := rend.Exchange(fakeEncPollReq)
So(err, ShouldBeNil)
So(answer, ShouldResemble, fakeEncPollResp)
})
Convey("ampCacheRendezvous.Exchange responds with no answer", func() {
fakeEncPollResp := makeEncPollResp(
"",
`{"error": "no snowflake proxies currently available"}`,
)
rend, err := newAMPCacheRendezvous("http://test.broker", "", "",
&mockTransport{http.StatusOK, ampArmorEncode(fakeEncPollResp)})
So(err, ShouldBeNil)
answer, err := rend.Exchange(fakeEncPollReq)
So(err, ShouldBeNil)
So(answer, ShouldResemble, fakeEncPollResp)
})
Convey("ampCacheRendezvous.Exchange fails with unexpected HTTP status code", func() {
rend, err := newAMPCacheRendezvous("http://test.broker", "", "",
&mockTransport{http.StatusInternalServerError, []byte{}})
So(err, ShouldBeNil)
answer, err := rend.Exchange(fakeEncPollReq)
So(err, ShouldNotBeNil)
So(answer, ShouldBeNil)
So(err.Error(), ShouldResemble, BrokerErrorUnexpected)
})
Convey("ampCacheRendezvous.Exchange fails with error", func() {
transportErr := errors.New("error")
rend, err := newAMPCacheRendezvous("http://test.broker", "", "",
&errorTransport{err: transportErr})
So(err, ShouldBeNil)
answer, err := rend.Exchange(fakeEncPollReq)
So(err, ShouldEqual, transportErr)
So(answer, ShouldBeNil)
})
Convey("ampCacheRendezvous.Exchange fails with large read", func() {
// readLimit should apply to the raw HTTP body, not the
// encoded bytes. Encode readLimit bytes—the encoded
// size will be larger—and try to read the body. It
// should fail.
rend, err := newAMPCacheRendezvous("http://test.broker", "", "",
&mockTransport{http.StatusOK, ampArmorEncode(make([]byte, readLimit))})
So(err, ShouldBeNil)
_, err = rend.Exchange(fakeEncPollReq)
// We may get io.ErrUnexpectedEOF here, or something
// like "missing </pre> tag".
So(err, ShouldNotBeNil)
})
})
}
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