dendrite/keyserver/internal/cross_signing.go
Neil Alexander eb0efa4636
Cross-signing groundwork (#1953)
* Cross-signing groundwork

* Update to matrix-org/gomatrixserverlib#274

* Fix gobind builds, which stops unit tests in CI from yelling

* Some changes from review comments

* Fix build by passing in UIA

* Update to matrix-org/gomatrixserverlib@bec8d22

* Process master/self-signing keys from devices call

* nolint

* Enum-ify the key type in the database

* Process self-signing key too

* Fix sanity check in device list updater

* Fix check

* Fix sytest, hopefully

* Fix build
2021-08-04 17:56:29 +01:00

390 lines
13 KiB
Go

// Copyright 2021 The Matrix.org Foundation C.I.C.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package internal
import (
"context"
"crypto/ed25519"
"encoding/json"
"fmt"
"strings"
"github.com/matrix-org/dendrite/keyserver/api"
"github.com/matrix-org/dendrite/keyserver/types"
"github.com/matrix-org/gomatrixserverlib"
"github.com/sirupsen/logrus"
)
func sanityCheckKey(key gomatrixserverlib.CrossSigningKey, userID string, purpose gomatrixserverlib.CrossSigningKeyPurpose) error {
// Is there exactly one key?
if len(key.Keys) != 1 {
return fmt.Errorf("should contain exactly one key")
}
// Does the key ID match the key value? Iterates exactly once
for keyID, keyData := range key.Keys {
b64 := keyData.Encode()
tokens := strings.Split(string(keyID), ":")
if len(tokens) != 2 {
return fmt.Errorf("key ID is incorrectly formatted")
}
if tokens[1] != b64 {
return fmt.Errorf("key ID isn't correct")
}
}
// Does the key claim to be from the right user?
if userID != key.UserID {
return fmt.Errorf("key has a user ID mismatch")
}
// Does the key contain the correct purpose?
useful := false
for _, usage := range key.Usage {
if usage == purpose {
useful = true
break
}
}
if !useful {
return fmt.Errorf("key does not contain correct usage purpose")
}
return nil
}
// nolint:gocyclo
func (a *KeyInternalAPI) PerformUploadDeviceKeys(ctx context.Context, req *api.PerformUploadDeviceKeysRequest, res *api.PerformUploadDeviceKeysResponse) {
var masterKey gomatrixserverlib.Base64Bytes
hasMasterKey := false
if len(req.MasterKey.Keys) > 0 {
if err := sanityCheckKey(req.MasterKey, req.UserID, gomatrixserverlib.CrossSigningKeyPurposeMaster); err != nil {
res.Error = &api.KeyError{
Err: "Master key sanity check failed: " + err.Error(),
}
return
}
hasMasterKey = true
for _, keyData := range req.MasterKey.Keys { // iterates once, because sanityCheckKey requires one key
masterKey = keyData
}
}
if len(req.SelfSigningKey.Keys) > 0 {
if err := sanityCheckKey(req.SelfSigningKey, req.UserID, gomatrixserverlib.CrossSigningKeyPurposeSelfSigning); err != nil {
res.Error = &api.KeyError{
Err: "Self-signing key sanity check failed: " + err.Error(),
}
return
}
}
if len(req.UserSigningKey.Keys) > 0 {
if err := sanityCheckKey(req.UserSigningKey, req.UserID, gomatrixserverlib.CrossSigningKeyPurposeUserSigning); err != nil {
res.Error = &api.KeyError{
Err: "User-signing key sanity check failed: " + err.Error(),
}
return
}
}
// If the user hasn't given a new master key, then let's go and get their
// existing keys from the database.
if !hasMasterKey {
existingKeys, err := a.DB.CrossSigningKeysForUser(ctx, req.UserID)
if err != nil {
res.Error = &api.KeyError{
Err: "Retrieving cross-signing keys from database failed: " + err.Error(),
}
return
}
masterKey, hasMasterKey = existingKeys[gomatrixserverlib.CrossSigningKeyPurposeMaster]
}
// If the user isn't a local user and we haven't successfully found a key
// through any local means then ask over federation.
if !hasMasterKey {
_, host, err := gomatrixserverlib.SplitID('@', req.UserID)
if err != nil {
res.Error = &api.KeyError{
Err: "Retrieving cross-signing keys from federation failed: " + err.Error(),
}
return
}
keys, err := a.FedClient.QueryKeys(ctx, host, map[string][]string{
req.UserID: {},
})
if err != nil {
res.Error = &api.KeyError{
Err: "Retrieving cross-signing keys from federation failed: " + err.Error(),
}
return
}
switch k := keys.MasterKeys[req.UserID].CrossSigningBody.(type) {
case *gomatrixserverlib.CrossSigningKey:
if err := sanityCheckKey(*k, req.UserID, gomatrixserverlib.CrossSigningKeyPurposeMaster); err != nil {
res.Error = &api.KeyError{
Err: "Master key sanity check failed: " + err.Error(),
}
return
}
default:
res.Error = &api.KeyError{
Err: "Unexpected type for master key retrieved from federation",
}
return
}
}
// If we still don't have a master key at this point then there's nothing else
// we can do - we've checked both the request and the database.
if !hasMasterKey {
res.Error = &api.KeyError{
Err: "No master key was found, either in the database or in the request!",
IsMissingParam: true,
}
return
}
// The key ID is basically the key itself.
masterKeyID := gomatrixserverlib.KeyID(fmt.Sprintf("ed25519:%s", masterKey.Encode()))
// Work out which things we need to verify the signatures for.
toVerify := make(map[gomatrixserverlib.CrossSigningKeyPurpose]gomatrixserverlib.CrossSigningKey, 3)
toStore := types.CrossSigningKeyMap{}
if len(req.MasterKey.Keys) > 0 {
toVerify[gomatrixserverlib.CrossSigningKeyPurposeMaster] = req.MasterKey
}
if len(req.SelfSigningKey.Keys) > 0 {
toVerify[gomatrixserverlib.CrossSigningKeyPurposeSelfSigning] = req.SelfSigningKey
}
if len(req.UserSigningKey.Keys) > 0 {
toVerify[gomatrixserverlib.CrossSigningKeyPurposeUserSigning] = req.UserSigningKey
}
for purpose, key := range toVerify {
// Collect together the key IDs we need to verify with. This will include
// all of the key IDs specified in the signatures. We don't do this for
// the master key because we have no means to verify the signatures - we
// instead just need to store them.
if purpose != gomatrixserverlib.CrossSigningKeyPurposeMaster {
// Marshal the specific key back into JSON so that we can verify the
// signature of it.
keyJSON, err := json.Marshal(key)
if err != nil {
res.Error = &api.KeyError{
Err: fmt.Sprintf("The JSON of the key section is invalid: %s", err.Error()),
}
return
}
// Now check if the subkey is signed by the master key.
if err := gomatrixserverlib.VerifyJSON(req.UserID, masterKeyID, ed25519.PublicKey(masterKey), keyJSON); err != nil {
res.Error = &api.KeyError{
Err: fmt.Sprintf("The %q sub-key failed master key signature verification: %s", purpose, err.Error()),
IsInvalidSignature: true,
}
return
}
}
// If we've reached this point then all the signatures are valid so
// add the key to the list of keys to store.
for _, keyData := range key.Keys { // iterates once, see sanityCheckKey
toStore[purpose] = keyData
}
}
if err := a.DB.StoreCrossSigningKeysForUser(ctx, req.UserID, toStore); err != nil {
res.Error = &api.KeyError{
Err: fmt.Sprintf("a.DB.StoreCrossSigningKeysForUser: %s", err),
}
}
}
func (a *KeyInternalAPI) PerformUploadDeviceSignatures(ctx context.Context, req *api.PerformUploadDeviceSignaturesRequest, res *api.PerformUploadDeviceSignaturesResponse) {
selfSignatures := map[string]map[gomatrixserverlib.KeyID]gomatrixserverlib.CrossSigningForKeyOrDevice{}
otherSignatures := map[string]map[gomatrixserverlib.KeyID]gomatrixserverlib.CrossSigningForKeyOrDevice{}
for userID, forUserID := range req.Signatures {
for keyID, keyOrDevice := range forUserID {
switch key := keyOrDevice.CrossSigningBody.(type) {
case *gomatrixserverlib.CrossSigningKey:
if key.UserID == req.UserID {
if _, ok := selfSignatures[userID]; !ok {
selfSignatures[userID] = map[gomatrixserverlib.KeyID]gomatrixserverlib.CrossSigningForKeyOrDevice{}
}
selfSignatures[userID][keyID] = keyOrDevice
} else {
if _, ok := otherSignatures[userID]; !ok {
otherSignatures[userID] = map[gomatrixserverlib.KeyID]gomatrixserverlib.CrossSigningForKeyOrDevice{}
}
otherSignatures[userID][keyID] = keyOrDevice
}
case *gomatrixserverlib.DeviceKeys:
if key.UserID == req.UserID {
if _, ok := selfSignatures[userID]; !ok {
selfSignatures[userID] = map[gomatrixserverlib.KeyID]gomatrixserverlib.CrossSigningForKeyOrDevice{}
}
selfSignatures[userID][keyID] = keyOrDevice
} else {
if _, ok := otherSignatures[userID]; !ok {
otherSignatures[userID] = map[gomatrixserverlib.KeyID]gomatrixserverlib.CrossSigningForKeyOrDevice{}
}
otherSignatures[userID][keyID] = keyOrDevice
}
default:
continue
}
}
}
if err := a.processSelfSignatures(ctx, req.UserID, selfSignatures); err != nil {
res.Error = &api.KeyError{
Err: fmt.Sprintf("a.processSelfSignatures: %s", err),
}
return
}
if err := a.processOtherSignatures(ctx, req.UserID, otherSignatures); err != nil {
res.Error = &api.KeyError{
Err: fmt.Sprintf("a.processOtherSignatures: %s", err),
}
return
}
}
func (a *KeyInternalAPI) processSelfSignatures(
ctx context.Context, _ string,
signatures map[string]map[gomatrixserverlib.KeyID]gomatrixserverlib.CrossSigningForKeyOrDevice,
) error {
// Here we will process:
// * The user signing their own devices using their self-signing key
// * The user signing their master key using one of their devices
for targetUserID, forTargetUserID := range signatures {
for targetKeyID, signature := range forTargetUserID {
switch sig := signature.CrossSigningBody.(type) {
case *gomatrixserverlib.CrossSigningKey:
for originUserID, forOriginUserID := range sig.Signatures {
for originKeyID, originSig := range forOriginUserID {
if err := a.DB.StoreCrossSigningSigsForTarget(
ctx, originUserID, originKeyID, targetUserID, targetKeyID, originSig,
); err != nil {
return fmt.Errorf("a.DB.StoreCrossSigningKeysForTarget: %w", err)
}
}
}
case *gomatrixserverlib.DeviceKeys:
for originUserID, forOriginUserID := range sig.Signatures {
for originKeyID, originSig := range forOriginUserID {
if err := a.DB.StoreCrossSigningSigsForTarget(
ctx, originUserID, originKeyID, targetUserID, targetKeyID, originSig,
); err != nil {
return fmt.Errorf("a.DB.StoreCrossSigningKeysForTarget: %w", err)
}
}
}
default:
return fmt.Errorf("unexpected type assertion")
}
}
}
return nil
}
func (a *KeyInternalAPI) processOtherSignatures(
ctx context.Context, userID string,
signatures map[string]map[gomatrixserverlib.KeyID]gomatrixserverlib.CrossSigningForKeyOrDevice,
) error {
// Here we will process:
// * A user signing someone else's master keys using their user-signing keys
return nil
}
func (a *KeyInternalAPI) crossSigningKeysFromDatabase(
ctx context.Context, req *api.QueryKeysRequest, res *api.QueryKeysResponse,
) {
for userID := range req.UserToDevices {
keys, err := a.DB.CrossSigningKeysForUser(ctx, userID)
if err != nil {
logrus.WithError(err).Errorf("Failed to get cross-signing keys for user %q", userID)
continue
}
for keyType, keyData := range keys {
b64 := keyData.Encode()
keyID := gomatrixserverlib.KeyID("ed25519:" + b64)
key := gomatrixserverlib.CrossSigningKey{
UserID: userID,
Usage: []gomatrixserverlib.CrossSigningKeyPurpose{
keyType,
},
Keys: map[gomatrixserverlib.KeyID]gomatrixserverlib.Base64Bytes{
keyID: keyData,
},
}
sigs, err := a.DB.CrossSigningSigsForTarget(ctx, userID, keyID)
if err != nil {
logrus.WithError(err).Errorf("Failed to get cross-signing signatures for user %q key %q", userID, keyID)
continue
}
appendSignature := func(originUserID string, originKeyID gomatrixserverlib.KeyID, signature gomatrixserverlib.Base64Bytes) {
if key.Signatures == nil {
key.Signatures = types.CrossSigningSigMap{}
}
if _, ok := key.Signatures[originUserID]; !ok {
key.Signatures[originUserID] = make(map[gomatrixserverlib.KeyID]gomatrixserverlib.Base64Bytes)
}
key.Signatures[originUserID][originKeyID] = signature
}
for originUserID, forOrigin := range sigs {
for originKeyID, signature := range forOrigin {
switch {
case req.UserID != "" && originUserID == req.UserID:
// Include signatures that we created
appendSignature(originUserID, originKeyID, signature)
case originUserID == userID:
// Include signatures that were created by the person whose key
// we are processing
appendSignature(originUserID, originKeyID, signature)
}
}
}
switch keyType {
case gomatrixserverlib.CrossSigningKeyPurposeMaster:
res.MasterKeys[userID] = key
case gomatrixserverlib.CrossSigningKeyPurposeSelfSigning:
res.SelfSigningKeys[userID] = key
case gomatrixserverlib.CrossSigningKeyPurposeUserSigning:
res.UserSigningKeys[userID] = key
}
}
}
}