1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
|
// 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
}
|
