284 lines
11 KiB
Go
284 lines
11 KiB
Go
/*
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GoToSocial
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Copyright (C) 2021-2022 GoToSocial Authors admin@gotosocial.org
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This program is free software: you can redistribute it and/or modify
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it under the terms of the GNU Affero General Public License as published by
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the Free Software Foundation, either version 3 of the License, or
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(at your option) any later version.
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This program is distributed in the hope that it will be useful,
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but WITHOUT ANY WARRANTY; without even the implied warranty of
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MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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GNU Affero General Public License for more details.
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You should have received a copy of the GNU Affero General Public License
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along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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package federation
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import (
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"context"
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"crypto/x509"
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"encoding/json"
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"encoding/pem"
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"errors"
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"fmt"
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"net/url"
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"strings"
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"github.com/go-fed/httpsig"
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"github.com/superseriousbusiness/activity/pub"
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"github.com/superseriousbusiness/activity/streams"
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"github.com/superseriousbusiness/activity/streams/vocab"
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"github.com/superseriousbusiness/gotosocial/internal/ap"
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"github.com/superseriousbusiness/gotosocial/internal/config"
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"github.com/superseriousbusiness/gotosocial/internal/db"
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"github.com/superseriousbusiness/gotosocial/internal/gtserror"
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"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
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"github.com/superseriousbusiness/gotosocial/internal/log"
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)
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/*
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publicKeyer is BORROWED DIRECTLY FROM https://github.com/go-fed/apcore/blob/master/ap/util.go
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Thank you @cj@mastodon.technology ! <3
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*/
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type publicKeyer interface {
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GetW3IDSecurityV1PublicKey() vocab.W3IDSecurityV1PublicKeyProperty
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}
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/*
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getPublicKeyFromResponse is adapted from https://github.com/go-fed/apcore/blob/master/ap/util.go
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Thank you @cj@mastodon.technology ! <3
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*/
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func getPublicKeyFromResponse(c context.Context, b []byte, keyID *url.URL) (vocab.W3IDSecurityV1PublicKey, error) {
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m := make(map[string]interface{})
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if err := json.Unmarshal(b, &m); err != nil {
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return nil, err
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}
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t, err := streams.ToType(c, m)
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if err != nil {
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return nil, err
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}
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pker, ok := t.(publicKeyer)
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if !ok {
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return nil, fmt.Errorf("ActivityStreams type cannot be converted to one known to have publicKey property: %T", t)
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}
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pkp := pker.GetW3IDSecurityV1PublicKey()
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if pkp == nil {
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return nil, errors.New("publicKey property is not provided")
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}
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var pkpFound vocab.W3IDSecurityV1PublicKey
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for pkpIter := pkp.Begin(); pkpIter != pkp.End(); pkpIter = pkpIter.Next() {
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if !pkpIter.IsW3IDSecurityV1PublicKey() {
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continue
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}
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pkValue := pkpIter.Get()
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var pkID *url.URL
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pkID, err = pub.GetId(pkValue)
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if err != nil {
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return nil, err
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}
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if pkID.String() != keyID.String() {
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continue
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}
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pkpFound = pkValue
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break
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}
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if pkpFound == nil {
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return nil, fmt.Errorf("cannot find publicKey with id: %s", keyID)
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}
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return pkpFound, nil
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}
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// AuthenticateFederatedRequest authenticates any kind of incoming federated request from a remote server. This includes things like
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// GET requests for dereferencing our users or statuses etc, and POST requests for delivering new Activities. The function returns
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// the URL of the owner of the public key used in the requesting http signature.
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//
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// Authenticate in this case is defined as making sure that the http request is actually signed by whoever claims
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// to have signed it, by fetching the public key from the signature and checking it against the remote public key.
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//
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// The provided username will be used to generate a transport for making remote requests/derefencing the public key ID of the request signature.
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// Ideally you should pass in the username of the user *being requested*, so that the remote server can decide how to handle the request based on who's making it.
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// Ie., if the request on this server is for https://example.org/users/some_username then you should pass in the username 'some_username'.
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// The remote server will then know that this is the user making the dereferencing request, and they can decide to allow or deny the request depending on their settings.
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//
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// Note that it is also valid to pass in an empty string here, in which case the keys of the instance account will be used.
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//
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// Also note that this function *does not* dereference the remote account that the signature key is associated with.
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// Other functions should use the returned URL to dereference the remote account, if required.
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func (f *federator) AuthenticateFederatedRequest(ctx context.Context, requestedUsername string) (*url.URL, gtserror.WithCode) {
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var publicKey interface{}
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var pkOwnerURI *url.URL
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var err error
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// thanks to signaturecheck.go in the security package, we should already have a signature verifier set on the context
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vi := ctx.Value(ap.ContextRequestingPublicKeyVerifier)
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if vi == nil {
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err := errors.New("http request wasn't signed or http signature was invalid")
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errWithCode := gtserror.NewErrorUnauthorized(err, err.Error())
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log.Debug(errWithCode)
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return nil, errWithCode
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}
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verifier, ok := vi.(httpsig.Verifier)
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if !ok {
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err := errors.New("http request wasn't signed or http signature was invalid")
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errWithCode := gtserror.NewErrorUnauthorized(err, err.Error())
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log.Debug(errWithCode)
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return nil, errWithCode
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}
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// we should have the signature itself set too
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si := ctx.Value(ap.ContextRequestingPublicKeySignature)
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if si == nil {
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err := errors.New("http request wasn't signed or http signature was invalid")
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errWithCode := gtserror.NewErrorUnauthorized(err, err.Error())
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log.Debug(errWithCode)
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return nil, errWithCode
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}
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signature, ok := si.(string)
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if !ok {
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err := errors.New("http request wasn't signed or http signature was invalid")
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errWithCode := gtserror.NewErrorUnauthorized(err, err.Error())
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log.Debug(errWithCode)
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return nil, errWithCode
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}
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// now figure out who actually signed it
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requestingPublicKeyID, err := url.Parse(verifier.KeyId())
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if err != nil {
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errWithCode := gtserror.NewErrorBadRequest(err, fmt.Sprintf("couldn't parse public key URL %s", verifier.KeyId()))
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log.Debug(errWithCode)
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return nil, errWithCode
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}
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requestingRemoteAccount := >smodel.Account{}
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requestingLocalAccount := >smodel.Account{}
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requestingHost := requestingPublicKeyID.Host
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if host := config.GetHost(); strings.EqualFold(requestingHost, host) {
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// LOCAL ACCOUNT REQUEST
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// the request is coming from INSIDE THE HOUSE so skip the remote dereferencing
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log.Tracef("proceeding without dereference for local public key %s", requestingPublicKeyID)
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if err := f.db.GetWhere(ctx, []db.Where{{Key: "public_key_uri", Value: requestingPublicKeyID.String()}}, requestingLocalAccount); err != nil {
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errWithCode := gtserror.NewErrorInternalError(fmt.Errorf("couldn't get account with public key uri %s from the database: %s", requestingPublicKeyID.String(), err))
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log.Debug(errWithCode)
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return nil, errWithCode
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}
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publicKey = requestingLocalAccount.PublicKey
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pkOwnerURI, err = url.Parse(requestingLocalAccount.URI)
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if err != nil {
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errWithCode := gtserror.NewErrorBadRequest(err, fmt.Sprintf("couldn't parse public key owner URL %s", requestingLocalAccount.URI))
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log.Debug(errWithCode)
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return nil, errWithCode
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}
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} else if err := f.db.GetWhere(ctx, []db.Where{{Key: "public_key_uri", Value: requestingPublicKeyID.String()}}, requestingRemoteAccount); err == nil {
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// REMOTE ACCOUNT REQUEST WITH KEY CACHED LOCALLY
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// this is a remote account and we already have the public key for it so use that
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log.Tracef("proceeding without dereference for cached public key %s", requestingPublicKeyID)
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publicKey = requestingRemoteAccount.PublicKey
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pkOwnerURI, err = url.Parse(requestingRemoteAccount.URI)
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if err != nil {
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errWithCode := gtserror.NewErrorBadRequest(err, fmt.Sprintf("couldn't parse public key owner URL %s", requestingRemoteAccount.URI))
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log.Debug(errWithCode)
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return nil, errWithCode
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}
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} else {
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// REMOTE ACCOUNT REQUEST WITHOUT KEY CACHED LOCALLY
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// the request is remote and we don't have the public key yet,
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// so we need to authenticate the request properly by dereferencing the remote key
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log.Tracef("proceeding with dereference for uncached public key %s", requestingPublicKeyID)
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transport, err := f.transportController.NewTransportForUsername(ctx, requestedUsername)
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if err != nil {
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errWithCode := gtserror.NewErrorInternalError(fmt.Errorf("error creating transport for %s: %s", requestedUsername, err))
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log.Debug(errWithCode)
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return nil, errWithCode
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}
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// The actual http call to the remote server is made right here in the Dereference function.
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b, err := transport.Dereference(ctx, requestingPublicKeyID)
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if err != nil {
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errWithCode := gtserror.NewErrorUnauthorized(fmt.Errorf("error dereferencing public key %s: %s", requestingPublicKeyID, err))
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log.Debug(errWithCode)
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return nil, errWithCode
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}
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// if the key isn't in the response, we can't authenticate the request
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requestingPublicKey, err := getPublicKeyFromResponse(ctx, b, requestingPublicKeyID)
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if err != nil {
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errWithCode := gtserror.NewErrorUnauthorized(fmt.Errorf("error parsing public key %s: %s", requestingPublicKeyID, err))
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log.Debug(errWithCode)
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return nil, errWithCode
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}
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// we should be able to get the actual key embedded in the vocab.W3IDSecurityV1PublicKey
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pkPemProp := requestingPublicKey.GetW3IDSecurityV1PublicKeyPem()
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if pkPemProp == nil || !pkPemProp.IsXMLSchemaString() {
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errWithCode := gtserror.NewErrorUnauthorized(errors.New("publicKeyPem property is not provided or it is not embedded as a value"))
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log.Debug(errWithCode)
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return nil, errWithCode
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}
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// and decode the PEM so that we can parse it as a golang public key
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pubKeyPem := pkPemProp.Get()
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block, _ := pem.Decode([]byte(pubKeyPem))
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if block == nil || block.Type != "PUBLIC KEY" {
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errWithCode := gtserror.NewErrorUnauthorized(errors.New("could not decode publicKeyPem to PUBLIC KEY pem block type"))
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log.Debug(errWithCode)
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return nil, errWithCode
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}
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publicKey, err = x509.ParsePKIXPublicKey(block.Bytes)
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if err != nil {
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errWithCode := gtserror.NewErrorUnauthorized(fmt.Errorf("could not parse public key %s from block bytes: %s", requestingPublicKeyID, err))
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log.Debug(errWithCode)
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return nil, errWithCode
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}
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// all good! we just need the URI of the key owner to return
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pkOwnerProp := requestingPublicKey.GetW3IDSecurityV1Owner()
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if pkOwnerProp == nil || !pkOwnerProp.IsIRI() {
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errWithCode := gtserror.NewErrorUnauthorized(errors.New("publicKeyOwner property is not provided or it is not embedded as a value"))
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log.Debug(errWithCode)
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return nil, errWithCode
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}
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pkOwnerURI = pkOwnerProp.GetIRI()
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}
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// after all that, public key should be defined
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if publicKey == nil {
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errWithCode := gtserror.NewErrorInternalError(errors.New("returned public key was empty"))
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log.Debug(errWithCode)
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return nil, errWithCode
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}
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// do the actual authentication here!
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algos := []httpsig.Algorithm{
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httpsig.RSA_SHA256,
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httpsig.RSA_SHA512,
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httpsig.ED25519,
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}
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for _, algo := range algos {
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log.Tracef("trying algo: %s", algo)
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err := verifier.Verify(publicKey, algo)
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if err == nil {
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log.Tracef("authentication for %s PASSED with algorithm %s", pkOwnerURI, algo)
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return pkOwnerURI, nil
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}
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log.Tracef("authentication for %s NOT PASSED with algorithm %s: %s", pkOwnerURI, algo, err)
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}
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errWithCode := gtserror.NewErrorUnauthorized(fmt.Errorf("authentication not passed for public key owner %s; signature value was '%s'", pkOwnerURI, signature))
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log.Debug(errWithCode)
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return nil, errWithCode
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}
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