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package pub
import (
"bytes"
"context"
"crypto"
"fmt"
"io/ioutil"
"net/http"
"net/url"
"strings"
"sync"
"github.com/go-fed/httpsig"
)
const (
// acceptHeaderValue is the Accept header value indicating that the
// response should contain an ActivityStreams object.
acceptHeaderValue = "application/ld+json; profile=\"https://www.w3.org/ns/activitystreams\""
)
// isSuccess returns true if the HTTP status code is either OK, Created, or
// Accepted.
func isSuccess(code int) bool {
return code == http.StatusOK ||
code == http.StatusCreated ||
code == http.StatusAccepted
}
// Transport makes ActivityStreams calls to other servers in order to send or
// receive ActivityStreams data.
//
// It is responsible for setting the appropriate request headers, signing the
// requests if needed, and facilitating the traffic between this server and
// another.
//
// The transport is exclusively used to issue requests on behalf of an actor,
// and is never sending requests on behalf of the server in general.
//
// It may be reused multiple times, but never concurrently.
type Transport interface {
// Dereference fetches the ActivityStreams object located at this IRI
// with a GET request.
Dereference(c context.Context, iri *url.URL) ([]byte, error)
// Deliver sends an ActivityStreams object.
Deliver(c context.Context, b []byte, to *url.URL) error
// BatchDeliver sends an ActivityStreams object to multiple recipients.
BatchDeliver(c context.Context, b []byte, recipients []*url.URL) error
}
// Transport must be implemented by HttpSigTransport.
var _ Transport = &HttpSigTransport{}
// HttpSigTransport makes a dereference call using HTTP signatures to
// authenticate the request on behalf of a particular actor.
//
// No rate limiting is applied.
//
// Only one request is tried per call.
type HttpSigTransport struct {
client HttpClient
appAgent string
gofedAgent string
clock Clock
getSigner httpsig.Signer
getSignerMu *sync.Mutex
postSigner httpsig.Signer
postSignerMu *sync.Mutex
pubKeyId string
privKey crypto.PrivateKey
}
// NewHttpSigTransport returns a new Transport.
//
// It sends requests specifically on behalf of a specific actor on this server.
// The actor's credentials are used to add an HTTP Signature to requests, which
// requires an actor's private key, a unique identifier for their public key,
// and an HTTP Signature signing algorithm.
//
// The client lets users issue requests through any HTTP client, including the
// standard library's HTTP client.
//
// The appAgent uniquely identifies the calling application's requests, so peers
// may aid debugging the requests incoming from this server. Note that the
// agent string will also include one for go-fed, so at minimum peer servers can
// reach out to the go-fed library to aid in notifying implementors of malformed
// or unsupported requests.
func NewHttpSigTransport(
client HttpClient,
appAgent string,
clock Clock,
getSigner, postSigner httpsig.Signer,
pubKeyId string,
privKey crypto.PrivateKey) *HttpSigTransport {
return &HttpSigTransport{
client: client,
appAgent: appAgent,
gofedAgent: goFedUserAgent(),
clock: clock,
getSigner: getSigner,
getSignerMu: &sync.Mutex{},
postSigner: postSigner,
postSignerMu: &sync.Mutex{},
pubKeyId: pubKeyId,
privKey: privKey,
}
}
// Dereference sends a GET request signed with an HTTP Signature to obtain an
// ActivityStreams value.
func (h HttpSigTransport) Dereference(c context.Context, iri *url.URL) ([]byte, error) {
req, err := http.NewRequest("GET", iri.String(), nil)
if err != nil {
return nil, err
}
req = req.WithContext(c)
req.Header.Add(acceptHeader, acceptHeaderValue)
req.Header.Add("Accept-Charset", "utf-8")
req.Header.Add("Date", h.clock.Now().UTC().Format("Mon, 02 Jan 2006 15:04:05")+" GMT")
req.Header.Add("User-Agent", fmt.Sprintf("%s %s", h.appAgent, h.gofedAgent))
req.Header.Set("Host", iri.Host)
h.getSignerMu.Lock()
err = h.getSigner.SignRequest(h.privKey, h.pubKeyId, req, nil)
h.getSignerMu.Unlock()
if err != nil {
return nil, err
}
resp, err := h.client.Do(req)
if err != nil {
return nil, err
}
defer resp.Body.Close()
if resp.StatusCode != http.StatusOK {
return nil, fmt.Errorf("GET request to %s failed (%d): %s", iri.String(), resp.StatusCode, resp.Status)
}
return ioutil.ReadAll(resp.Body)
}
// Deliver sends a POST request with an HTTP Signature.
func (h HttpSigTransport) Deliver(c context.Context, b []byte, to *url.URL) error {
req, err := http.NewRequest("POST", to.String(), bytes.NewReader(b))
if err != nil {
return err
}
req = req.WithContext(c)
req.Header.Add(contentTypeHeader, contentTypeHeaderValue)
req.Header.Add("Accept-Charset", "utf-8")
req.Header.Add("Date", h.clock.Now().UTC().Format("Mon, 02 Jan 2006 15:04:05")+" GMT")
req.Header.Add("User-Agent", fmt.Sprintf("%s %s", h.appAgent, h.gofedAgent))
req.Header.Set("Host", to.Host)
h.postSignerMu.Lock()
err = h.postSigner.SignRequest(h.privKey, h.pubKeyId, req, b)
h.postSignerMu.Unlock()
if err != nil {
return err
}
resp, err := h.client.Do(req)
if err != nil {
return err
}
defer resp.Body.Close()
if !isSuccess(resp.StatusCode) {
return fmt.Errorf("POST request to %s failed (%d): %s", to.String(), resp.StatusCode, resp.Status)
}
return nil
}
// BatchDeliver sends concurrent POST requests. Returns an error if any of the
// requests had an error.
func (h HttpSigTransport) BatchDeliver(c context.Context, b []byte, recipients []*url.URL) error {
var wg sync.WaitGroup
errCh := make(chan error, len(recipients))
for _, recipient := range recipients {
wg.Add(1)
go func(r *url.URL) {
defer wg.Done()
if err := h.Deliver(c, b, r); err != nil {
errCh <- err
}
}(recipient)
}
wg.Wait()
errs := make([]string, 0, len(recipients))
outer:
for {
select {
case e := <-errCh:
errs = append(errs, e.Error())
default:
break outer
}
}
if len(errs) > 0 {
return fmt.Errorf("batch deliver had at least one failure: %s", strings.Join(errs, "; "))
}
return nil
}
// HttpClient sends http requests, and is an abstraction only needed by the
// HttpSigTransport. The standard library's Client satisfies this interface.
type HttpClient interface {
Do(req *http.Request) (*http.Response, error)
}
// HttpClient must be implemented by http.Client.
var _ HttpClient = &http.Client{}
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