311 lines
11 KiB
Go
311 lines
11 KiB
Go
// Copyright (c) 2021 Tulir Asokan
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//
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this
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// file, You can obtain one at http://mozilla.org/MPL/2.0/.
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package appstate
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import (
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"bytes"
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"crypto/sha256"
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"encoding/json"
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"fmt"
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"google.golang.org/protobuf/proto"
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waBinary "go.mau.fi/whatsmeow/binary"
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waProto "go.mau.fi/whatsmeow/binary/proto"
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"go.mau.fi/whatsmeow/store"
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"go.mau.fi/whatsmeow/util/cbcutil"
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)
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// PatchList represents a decoded response to getting app state patches from the WhatsApp servers.
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type PatchList struct {
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Name WAPatchName
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HasMorePatches bool
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Patches []*waProto.SyncdPatch
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Snapshot *waProto.SyncdSnapshot
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}
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// DownloadExternalFunc is a function that can download a blob of external app state patches.
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type DownloadExternalFunc func(*waProto.ExternalBlobReference) ([]byte, error)
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func parseSnapshotInternal(collection *waBinary.Node, downloadExternal DownloadExternalFunc) (*waProto.SyncdSnapshot, error) {
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snapshotNode := collection.GetChildByTag("snapshot")
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rawSnapshot, ok := snapshotNode.Content.([]byte)
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if snapshotNode.Tag != "snapshot" || !ok {
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return nil, nil
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}
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var snapshot waProto.ExternalBlobReference
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err := proto.Unmarshal(rawSnapshot, &snapshot)
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if err != nil {
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return nil, fmt.Errorf("failed to unmarshal snapshot: %w", err)
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}
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var rawData []byte
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rawData, err = downloadExternal(&snapshot)
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if err != nil {
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return nil, fmt.Errorf("failed to download external mutations: %w", err)
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}
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var downloaded waProto.SyncdSnapshot
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err = proto.Unmarshal(rawData, &downloaded)
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if err != nil {
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return nil, fmt.Errorf("failed to unmarshal mutation list: %w", err)
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}
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return &downloaded, nil
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}
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func parsePatchListInternal(collection *waBinary.Node, downloadExternal DownloadExternalFunc) ([]*waProto.SyncdPatch, error) {
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patchesNode := collection.GetChildByTag("patches")
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patchNodes := patchesNode.GetChildren()
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patches := make([]*waProto.SyncdPatch, 0, len(patchNodes))
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for i, patchNode := range patchNodes {
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rawPatch, ok := patchNode.Content.([]byte)
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if patchNode.Tag != "patch" || !ok {
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continue
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}
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var patch waProto.SyncdPatch
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err := proto.Unmarshal(rawPatch, &patch)
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if err != nil {
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return nil, fmt.Errorf("failed to unmarshal patch #%d: %w", i+1, err)
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}
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if patch.GetExternalMutations() != nil && downloadExternal != nil {
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var rawData []byte
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rawData, err = downloadExternal(patch.GetExternalMutations())
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if err != nil {
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return nil, fmt.Errorf("failed to download external mutations: %w", err)
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}
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var downloaded waProto.SyncdMutations
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err = proto.Unmarshal(rawData, &downloaded)
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if err != nil {
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return nil, fmt.Errorf("failed to unmarshal mutation list: %w", err)
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} else if len(downloaded.GetMutations()) == 0 {
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return nil, fmt.Errorf("didn't get any mutations from download")
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}
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patch.Mutations = downloaded.Mutations
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}
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patches = append(patches, &patch)
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}
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return patches, nil
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}
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// ParsePatchList will decode an XML node containing app state patches, including downloading any external blobs.
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func ParsePatchList(node *waBinary.Node, downloadExternal DownloadExternalFunc) (*PatchList, error) {
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collection := node.GetChildByTag("sync", "collection")
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ag := collection.AttrGetter()
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snapshot, err := parseSnapshotInternal(&collection, downloadExternal)
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if err != nil {
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return nil, err
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}
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patches, err := parsePatchListInternal(&collection, downloadExternal)
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if err != nil {
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return nil, err
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}
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list := &PatchList{
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Name: WAPatchName(ag.String("name")),
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HasMorePatches: ag.OptionalBool("has_more_patches"),
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Patches: patches,
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Snapshot: snapshot,
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}
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return list, ag.Error()
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}
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type patchOutput struct {
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RemovedMACs [][]byte
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AddedMACs []store.AppStateMutationMAC
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Mutations []Mutation
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}
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func (proc *Processor) decodeMutations(mutations []*waProto.SyncdMutation, out *patchOutput, validateMACs bool) error {
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for i, mutation := range mutations {
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keyID := mutation.GetRecord().GetKeyId().GetId()
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keys, err := proc.getAppStateKey(keyID)
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if err != nil {
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return fmt.Errorf("failed to get key %X to decode mutation: %w", keyID, err)
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}
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content := mutation.GetRecord().GetValue().GetBlob()
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content, valueMAC := content[:len(content)-32], content[len(content)-32:]
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if validateMACs {
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expectedValueMAC := generateContentMAC(mutation.GetOperation(), content, keyID, keys.ValueMAC)
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if !bytes.Equal(expectedValueMAC, valueMAC) {
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return fmt.Errorf("failed to verify mutation #%d: %w", i+1, ErrMismatchingContentMAC)
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}
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}
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iv, content := content[:16], content[16:]
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plaintext, err := cbcutil.Decrypt(keys.ValueEncryption, iv, content)
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if err != nil {
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return fmt.Errorf("failed to decrypt mutation #%d: %w", i+1, err)
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}
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var syncAction waProto.SyncActionData
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err = proto.Unmarshal(plaintext, &syncAction)
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if err != nil {
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return fmt.Errorf("failed to unmarshal mutation #%d: %w", i+1, err)
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}
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indexMAC := mutation.GetRecord().GetIndex().GetBlob()
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if validateMACs {
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expectedIndexMAC := concatAndHMAC(sha256.New, keys.Index, syncAction.Index)
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if !bytes.Equal(expectedIndexMAC, indexMAC) {
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return fmt.Errorf("failed to verify mutation #%d: %w", i+1, ErrMismatchingIndexMAC)
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}
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}
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var index []string
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err = json.Unmarshal(syncAction.GetIndex(), &index)
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if err != nil {
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return fmt.Errorf("failed to unmarshal index of mutation #%d: %w", i+1, err)
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}
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if mutation.GetOperation() == waProto.SyncdMutation_REMOVE {
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out.RemovedMACs = append(out.RemovedMACs, indexMAC)
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} else if mutation.GetOperation() == waProto.SyncdMutation_SET {
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out.AddedMACs = append(out.AddedMACs, store.AppStateMutationMAC{
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IndexMAC: indexMAC,
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ValueMAC: valueMAC,
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})
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}
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out.Mutations = append(out.Mutations, Mutation{
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Operation: mutation.GetOperation(),
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Action: syncAction.GetValue(),
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Index: index,
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IndexMAC: indexMAC,
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ValueMAC: valueMAC,
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})
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}
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return nil
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}
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func (proc *Processor) storeMACs(name WAPatchName, currentState HashState, out *patchOutput) {
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err := proc.Store.AppState.PutAppStateVersion(string(name), currentState.Version, currentState.Hash)
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if err != nil {
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proc.Log.Errorf("Failed to update app state version in the database: %v", err)
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}
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err = proc.Store.AppState.DeleteAppStateMutationMACs(string(name), out.RemovedMACs)
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if err != nil {
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proc.Log.Errorf("Failed to remove deleted mutation MACs from the database: %v", err)
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}
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err = proc.Store.AppState.PutAppStateMutationMACs(string(name), currentState.Version, out.AddedMACs)
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if err != nil {
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proc.Log.Errorf("Failed to insert added mutation MACs to the database: %v", err)
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}
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}
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func (proc *Processor) validateSnapshotMAC(name WAPatchName, currentState HashState, keyID, expectedSnapshotMAC []byte) (keys ExpandedAppStateKeys, err error) {
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keys, err = proc.getAppStateKey(keyID)
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if err != nil {
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err = fmt.Errorf("failed to get key %X to verify patch v%d MACs: %w", keyID, currentState.Version, err)
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return
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}
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snapshotMAC := currentState.generateSnapshotMAC(name, keys.SnapshotMAC)
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if !bytes.Equal(snapshotMAC, expectedSnapshotMAC) {
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err = fmt.Errorf("failed to verify patch v%d: %w", currentState.Version, ErrMismatchingLTHash)
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}
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return
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}
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func (proc *Processor) decodeSnapshot(name WAPatchName, ss *waProto.SyncdSnapshot, initialState HashState, validateMACs bool, newMutationsInput []Mutation) (newMutations []Mutation, currentState HashState, err error) {
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currentState = initialState
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currentState.Version = ss.GetVersion().GetVersion()
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encryptedMutations := make([]*waProto.SyncdMutation, len(ss.GetRecords()))
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for i, record := range ss.GetRecords() {
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encryptedMutations[i] = &waProto.SyncdMutation{
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Operation: waProto.SyncdMutation_SET.Enum(),
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Record: record,
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}
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}
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var warn []error
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warn, err = currentState.updateHash(encryptedMutations, func(indexMAC []byte, maxIndex int) ([]byte, error) {
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return nil, nil
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})
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if len(warn) > 0 {
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proc.Log.Warnf("Warnings while updating hash for %s: %+v", name, warn)
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}
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if err != nil {
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err = fmt.Errorf("failed to update state hash: %w", err)
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return
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}
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if validateMACs {
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_, err = proc.validateSnapshotMAC(name, currentState, ss.GetKeyId().GetId(), ss.GetMac())
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if err != nil {
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return
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}
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}
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var out patchOutput
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out.Mutations = newMutationsInput
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err = proc.decodeMutations(encryptedMutations, &out, validateMACs)
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if err != nil {
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err = fmt.Errorf("failed to decode snapshot of v%d: %w", currentState.Version, err)
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return
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}
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proc.storeMACs(name, currentState, &out)
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newMutations = out.Mutations
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return
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}
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// DecodePatches will decode all the patches in a PatchList into a list of app state mutations.
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func (proc *Processor) DecodePatches(list *PatchList, initialState HashState, validateMACs bool) (newMutations []Mutation, currentState HashState, err error) {
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currentState = initialState
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var expectedLength int
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if list.Snapshot != nil {
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expectedLength = len(list.Snapshot.GetRecords())
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}
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for _, patch := range list.Patches {
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expectedLength += len(patch.GetMutations())
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}
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newMutations = make([]Mutation, 0, expectedLength)
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if list.Snapshot != nil {
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newMutations, currentState, err = proc.decodeSnapshot(list.Name, list.Snapshot, currentState, validateMACs, newMutations)
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if err != nil {
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return
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}
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}
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for _, patch := range list.Patches {
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version := patch.GetVersion().GetVersion()
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currentState.Version = version
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var warn []error
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warn, err = currentState.updateHash(patch.GetMutations(), func(indexMAC []byte, maxIndex int) ([]byte, error) {
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for i := maxIndex - 1; i >= 0; i-- {
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if bytes.Equal(patch.Mutations[i].GetRecord().GetIndex().GetBlob(), indexMAC) {
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value := patch.Mutations[i].GetRecord().GetValue().GetBlob()
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return value[len(value)-32:], nil
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}
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}
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// Previous value not found in current patch, look in the database
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return proc.Store.AppState.GetAppStateMutationMAC(string(list.Name), indexMAC)
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})
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if len(warn) > 0 {
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proc.Log.Warnf("Warnings while updating hash for %s: %+v", list.Name, warn)
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}
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if err != nil {
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err = fmt.Errorf("failed to update state hash: %w", err)
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return
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}
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if validateMACs {
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var keys ExpandedAppStateKeys
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keys, err = proc.validateSnapshotMAC(list.Name, currentState, patch.GetKeyId().GetId(), patch.GetSnapshotMac())
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if err != nil {
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return
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}
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patchMAC := generatePatchMAC(patch, list.Name, keys.PatchMAC)
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if !bytes.Equal(patchMAC, patch.GetPatchMac()) {
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err = fmt.Errorf("failed to verify patch v%d: %w", version, ErrMismatchingPatchMAC)
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return
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}
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}
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var out patchOutput
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out.Mutations = newMutations
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err = proc.decodeMutations(patch.GetMutations(), &out, validateMACs)
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if err != nil {
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return
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}
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proc.storeMACs(list.Name, currentState, &out)
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newMutations = out.Mutations
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}
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return
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}
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