work on validating incoming fed requests

internal/federation/protocol.go

@@ -30,22 +30,25 @@ import (
 	"github.com/sirupsen/logrus"
 	"github.com/superseriousbusiness/gotosocial/internal/config"
 	"github.com/superseriousbusiness/gotosocial/internal/db"
+	"github.com/superseriousbusiness/gotosocial/internal/transport"
 	"github.com/superseriousbusiness/gotosocial/internal/util"
 )
 
 // Federator implements the go-fed federating protocol interface
 type Federator struct {
-	db     db.DB
-	log    *logrus.Logger
-	config *config.Config
+	db                  db.DB
+	log                 *logrus.Logger
+	config              *config.Config
+	transportController transport.Controller
 }
 
 // NewFederator returns the gotosocial implementation of the go-fed FederatingProtocol interface
-func NewFederator(db db.DB, log *logrus.Logger, config *config.Config) pub.FederatingProtocol {
+func NewFederator(db db.DB, log *logrus.Logger, config *config.Config, transportController transport.Controller) pub.FederatingProtocol {
 	return &Federator{
-		db:     db,
-		log:    log,
-		config: config,
+		db:                  db,
+		log:                 log,
+		config:              config,
+		transportController: transportController,
 	}
 }
 
@@ -76,17 +79,18 @@ func NewFederator(db db.DB, log *logrus.Logger, config *config.Config) pub.Feder
 // write a response to the ResponseWriter as is expected that the caller
 // to PostInbox will do so when handling the error.
 func (f *Federator) PostInboxRequestBodyHook(ctx context.Context, r *http.Request, activity pub.Activity) (context.Context, error) {
-	if activity == nil {
-		return nil, errors.New("nil activity in PostInboxRequestBodyHook")
-	}
-
 	l := f.log.WithFields(logrus.Fields{
 		"func":      "PostInboxRequestBodyHook",
 		"useragent": r.UserAgent(),
 		"url":       r.URL.String(),
-		"aptype":    activity.GetTypeName(),
 	})
 
+	if activity == nil {
+		err := errors.New("nil activity in PostInboxRequestBodyHook")
+		l.Debug(err)
+		return nil, err
+	}
+
 	if !util.IsInboxPath(r.URL) {
 		err := fmt.Errorf("url %s did not corresponding to inbox path", r.URL.String())
 		l.Debug(err)
@@ -123,8 +127,28 @@ func (f *Federator) PostInboxRequestBodyHook(ctx context.Context, r *http.Reques
 // authenticated must be true and error nil. The request will continue
 // to be processed.
 func (f *Federator) AuthenticatePostInbox(ctx context.Context, w http.ResponseWriter, r *http.Request) (context.Context, bool, error) {
-	// TODO
-	return nil, false, nil
+	l := f.log.WithFields(logrus.Fields{
+		"func":      "AuthenticatePostInbox",
+		"useragent": r.UserAgent(),
+		"url":       r.URL.String(),
+	})
+	l.Trace("received request to authenticate")
+
+	if !util.IsInboxPath(r.URL) {
+		err := fmt.Errorf("url %s did not corresponding to inbox path", r.URL.String())
+		l.Debug(err)
+		return nil, false, err
+	}
+
+	username, err := util.ParseInboxPath(r.URL)
+	if err != nil {
+		err := fmt.Errorf("could not parse username from url: %s", r.URL.String())
+		l.Debug(err)
+		return nil, false, err
+	}
+	l.Tracef("parsed username %s from %s", username, r.URL.String())
+
+	return validateInboundFederationRequest(ctx, r, f.db, username, f.transportController)
 }
 
 // Blocked should determine whether to permit a set of actors given by

internal/federation/protocol_test.go

@@ -34,6 +34,7 @@ import (
 	"github.com/superseriousbusiness/gotosocial/internal/config"
 	"github.com/superseriousbusiness/gotosocial/internal/db"
 	"github.com/superseriousbusiness/gotosocial/internal/federation"
+	"github.com/superseriousbusiness/gotosocial/internal/transport"
 	"github.com/superseriousbusiness/gotosocial/internal/util"
 	"github.com/superseriousbusiness/gotosocial/testrig"
 )
@@ -44,6 +45,7 @@ type ProtocolTestSuite struct {
 	db         db.DB
 	log        *logrus.Logger
 	federator  *federation.Federator
+	tc         transport.Controller
 	activities map[string]pub.Activity
 }
 
@@ -53,10 +55,13 @@ func (suite *ProtocolTestSuite) SetupSuite() {
 	suite.config = testrig.NewTestConfig()
 	suite.db = testrig.NewTestDB()
 	suite.log = testrig.NewTestLog()
+	suite.tc = testrig.NewTestTransportController(suite.db, testrig.NewMockHTTPClient(func(req *http.Request)(*http.Response, error) {
+		return nil, nil
+	}))
 	suite.activities = testrig.NewTestActivities()
 
 	// setup module being tested
-	suite.federator = federation.NewFederator(suite.db, suite.log, suite.config).(*federation.Federator)
+	suite.federator = federation.NewFederator(suite.db, suite.log, suite.config, suite.tc).(*federation.Federator)
 }
 
 func (suite *ProtocolTestSuite) SetupTest() {

internal/federation/util.go

@@ -0,0 +1,151 @@
+/*
+   GoToSocial
+   Copyright (C) 2021 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package federation
+
+import (
+	"context"
+	"crypto"
+	"crypto/x509"
+	"encoding/json"
+	"encoding/pem"
+	"fmt"
+	"net/http"
+	"net/url"
+
+	"github.com/go-fed/activity/pub"
+	"github.com/go-fed/activity/streams"
+	"github.com/go-fed/activity/streams/vocab"
+	"github.com/go-fed/httpsig"
+	"github.com/superseriousbusiness/gotosocial/internal/db"
+	"github.com/superseriousbusiness/gotosocial/internal/db/gtsmodel"
+	"github.com/superseriousbusiness/gotosocial/internal/transport"
+)
+
+
+/*
+	publicKeyer is BORROWED DIRECTLY FROM https://github.com/go-fed/apcore/blob/master/ap/util.go
+	Thank you @cj@mastodon.technology ! <3
+*/
+type publicKeyer interface {
+	GetW3IDSecurityV1PublicKey() vocab.W3IDSecurityV1PublicKeyProperty
+}
+
+/*
+	getPublicKeyFromResponse is BORROWED DIRECTLY FROM https://github.com/go-fed/apcore/blob/master/ap/util.go
+	Thank you @cj@mastodon.technology ! <3
+*/
+func getPublicKeyFromResponse(c context.Context, b []byte, keyId *url.URL) (p crypto.PublicKey, err error) {
+	m := make(map[string]interface{}, 0)
+	err = json.Unmarshal(b, &m)
+	if err != nil {
+		return
+	}
+	var t vocab.Type
+	t, err = streams.ToType(c, m)
+	if err != nil {
+		return
+	}
+	pker, ok := t.(publicKeyer)
+	if !ok {
+		err = fmt.Errorf("ActivityStreams type cannot be converted to one known to have publicKey property: %T", t)
+		return
+	}
+	pkp := pker.GetW3IDSecurityV1PublicKey()
+	if pkp == nil {
+		err = fmt.Errorf("publicKey property is not provided")
+		return
+	}
+	var pkpFound vocab.W3IDSecurityV1PublicKey
+	for pkpIter := pkp.Begin(); pkpIter != pkp.End(); pkpIter = pkpIter.Next() {
+		if !pkpIter.IsW3IDSecurityV1PublicKey() {
+			continue
+		}
+		pkValue := pkpIter.Get()
+		var pkId *url.URL
+		pkId, err = pub.GetId(pkValue)
+		if err != nil {
+			return
+		}
+		if pkId.String() != keyId.String() {
+			continue
+		}
+		pkpFound = pkValue
+		break
+	}
+	if pkpFound == nil {
+		err = fmt.Errorf("cannot find publicKey with id: %s", keyId)
+		return
+	}
+	pkPemProp := pkpFound.GetW3IDSecurityV1PublicKeyPem()
+	if pkPemProp == nil || !pkPemProp.IsXMLSchemaString() {
+		err = fmt.Errorf("publicKeyPem property is not provided or it is not embedded as a value")
+		return
+	}
+	pubKeyPem := pkPemProp.Get()
+	var block *pem.Block
+	block, _ = pem.Decode([]byte(pubKeyPem))
+	if block == nil || block.Type != "PUBLIC KEY" {
+		err = fmt.Errorf("could not decode publicKeyPem to PUBLIC KEY pem block type")
+		return
+	}
+	p, err = x509.ParsePKIXPublicKey(block.Bytes)
+	return
+}
+
+// validateInboundFederationRequest validates an incoming federation request (!!) by deriving the public key
+// of the requester from the request, checking the owner of the inbox that's being requested, and doing
+// some fiddling around with http signatures.
+func validateInboundFederationRequest(ctx context.Context, request *http.Request, db db.DB, inboxUsername string, transportController transport.Controller) (context.Context, bool, error) {
+	v, err := httpsig.NewVerifier(request)
+	if err != nil {
+		return ctx, false, fmt.Errorf("could not create http sig verifier: %s", err)
+	}
+
+	requesterPublicKeyID, err := url.Parse(v.KeyId())
+	if err != nil {
+		return ctx, false, fmt.Errorf("could not create parse key id into a url: %s", err)
+	}
+
+	acct := &gtsmodel.Account{}
+	if err := db.GetWhere("username", inboxUsername, acct); err != nil {
+		return ctx, false, fmt.Errorf("could not fetch username %s from the database: %s", inboxUsername, err)
+	}
+
+	transport, err := transportController.NewTransport(acct.PublicKeyURI, acct.PrivateKey)
+	if err != nil {
+		return ctx, false, fmt.Errorf("error creating new transport: %s", err)
+	}
+
+	b, err := transport.Dereference(ctx, requesterPublicKeyID)
+	if err != nil {
+		return ctx, false, fmt.Errorf("error deferencing key %s: %s", requesterPublicKeyID.String(), err)
+	}
+
+	requesterPublicKey, err := getPublicKeyFromResponse(ctx, b, requesterPublicKeyID)
+	if err != nil {
+		return ctx, false, fmt.Errorf("error getting key %s from response %s: %s", requesterPublicKeyID.String(), string(b), err)
+	}
+
+	algo := httpsig.RSA_SHA256
+	if err := v.Verify(requesterPublicKey, algo); err != nil {
+		return ctx, false, fmt.Errorf("error verifying key %s: %s", requesterPublicKeyID.String(), err)
+	}
+
+	return ctx, true, nil
+}