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97 lines
3.2 KiB
Go
97 lines
3.2 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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"crypto/hmac"
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"crypto/sha256"
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"crypto/sha512"
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"encoding/binary"
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"fmt"
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"hash"
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"go.mau.fi/whatsmeow/appstate/lthash"
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waProto "go.mau.fi/whatsmeow/binary/proto"
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)
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type Mutation struct {
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Operation waProto.SyncdMutation_SyncdOperation
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Action *waProto.SyncActionValue
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Index []string
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IndexMAC []byte
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ValueMAC []byte
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}
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type HashState struct {
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Version uint64
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Hash [128]byte
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}
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func (hs *HashState) updateHash(mutations []*waProto.SyncdMutation, getPrevSetValueMAC func(indexMAC []byte, maxIndex int) ([]byte, error)) ([]error, error) {
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var added, removed [][]byte
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var warnings []error
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for i, mutation := range mutations {
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if mutation.GetOperation() == waProto.SyncdMutation_SET {
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value := mutation.GetRecord().GetValue().GetBlob()
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added = append(added, value[len(value)-32:])
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}
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indexMAC := mutation.GetRecord().GetIndex().GetBlob()
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removal, err := getPrevSetValueMAC(indexMAC, i)
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if err != nil {
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return warnings, fmt.Errorf("failed to get value MAC of previous SET operation: %w", err)
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} else if removal != nil {
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removed = append(removed, removal)
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} else if mutation.GetOperation() == waProto.SyncdMutation_REMOVE {
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// TODO figure out if there are certain cases that are safe to ignore and others that aren't
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// At least removing contact access from WhatsApp seems to create a REMOVE op for your own JID
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// that points to a non-existent index and is safe to ignore here. Other keys might not be safe to ignore.
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warnings = append(warnings, fmt.Errorf("%w for %X", ErrMissingPreviousSetValueOperation, indexMAC))
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//return ErrMissingPreviousSetValueOperation
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}
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}
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lthash.WAPatchIntegrity.SubtractThenAddInPlace(hs.Hash[:], removed, added)
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return warnings, nil
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}
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func uint64ToBytes(val uint64) []byte {
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data := make([]byte, 8)
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binary.BigEndian.PutUint64(data, val)
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return data
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}
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func concatAndHMAC(alg func() hash.Hash, key []byte, data ...[]byte) []byte {
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h := hmac.New(alg, key)
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for _, item := range data {
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h.Write(item)
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}
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return h.Sum(nil)
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}
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func (hs *HashState) generateSnapshotMAC(name WAPatchName, key []byte) []byte {
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return concatAndHMAC(sha256.New, key, hs.Hash[:], uint64ToBytes(hs.Version), []byte(name))
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}
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func generatePatchMAC(patch *waProto.SyncdPatch, name WAPatchName, key []byte) []byte {
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dataToHash := make([][]byte, len(patch.GetMutations())+3)
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dataToHash[0] = patch.GetSnapshotMac()
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for i, mutation := range patch.Mutations {
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val := mutation.GetRecord().GetValue().GetBlob()
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dataToHash[i+1] = val[len(val)-32:]
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}
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dataToHash[len(dataToHash)-2] = uint64ToBytes(patch.GetVersion().GetVersion())
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dataToHash[len(dataToHash)-1] = []byte(name)
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return concatAndHMAC(sha256.New, key, dataToHash...)
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}
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func generateContentMAC(operation waProto.SyncdMutation_SyncdOperation, data, keyID, key []byte) []byte {
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operationBytes := []byte{byte(operation) + 1}
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keyDataLength := uint64ToBytes(uint64(len(keyID) + 1))
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return concatAndHMAC(sha512.New, key, operationBytes, keyID, data, keyDataLength)[:32]
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}
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