mirror of
https://github.com/cwinfo/matterbridge.git
synced 2024-11-24 17:51:36 +00:00
59 lines
1.8 KiB
Go
59 lines
1.8 KiB
Go
// Copyright (c) 2021 Tulir Asokan
|
|
//
|
|
// This Source Code Form is subject to the terms of the Mozilla Public
|
|
// License, v. 2.0. If a copy of the MPL was not distributed with this
|
|
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
|
|
|
|
// Package lthash implements a summation based hash algorithm that maintains the
|
|
// integrity of a piece of data over a series of mutations. You can add/remove
|
|
// mutations, and it'll return a hash equal to if the same series of mutations
|
|
// was made sequentially.
|
|
package lthash
|
|
|
|
import (
|
|
"encoding/binary"
|
|
|
|
"go.mau.fi/whatsmeow/util/hkdfutil"
|
|
)
|
|
|
|
type LTHash struct {
|
|
HKDFInfo []byte
|
|
HKDFSize uint8
|
|
}
|
|
|
|
// WAPatchIntegrity is a LTHash instance initialized with the details used for verifying integrity of WhatsApp app state sync patches.
|
|
var WAPatchIntegrity = LTHash{[]byte("WhatsApp Patch Integrity"), 128}
|
|
|
|
func (lth LTHash) SubtractThenAdd(base []byte, subtract, add [][]byte) []byte {
|
|
output := make([]byte, len(base))
|
|
copy(output, base)
|
|
lth.SubtractThenAddInPlace(output, subtract, add)
|
|
return output
|
|
}
|
|
|
|
func (lth LTHash) SubtractThenAddInPlace(base []byte, subtract, add [][]byte) {
|
|
lth.multipleOp(base, subtract, true)
|
|
lth.multipleOp(base, add, false)
|
|
}
|
|
|
|
func (lth LTHash) multipleOp(base []byte, input [][]byte, subtract bool) {
|
|
for _, item := range input {
|
|
performPointwiseWithOverflow(base, hkdfutil.SHA256(item, nil, lth.HKDFInfo, lth.HKDFSize), subtract)
|
|
}
|
|
}
|
|
|
|
func performPointwiseWithOverflow(base, input []byte, subtract bool) []byte {
|
|
for i := 0; i < len(base); i += 2 {
|
|
x := binary.LittleEndian.Uint16(base[i : i+2])
|
|
y := binary.LittleEndian.Uint16(input[i : i+2])
|
|
var result uint16
|
|
if subtract {
|
|
result = x - y
|
|
} else {
|
|
result = x + y
|
|
}
|
|
binary.LittleEndian.PutUint16(base[i:i+2], result)
|
|
}
|
|
return base
|
|
}
|