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feat(QMCv2): better rc4 cipher

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This commit is contained in:
MengYX 2021-12-17 04:31:58 +08:00
parent 62f7991a64
commit def2925900
No known key found for this signature in database
GPG Key ID: E63F9C7303E8F604
2 changed files with 42 additions and 36 deletions
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57
algo/qmc/cipher_rc4.go
View File

@ -9,7 +9,7 @@ type rc4Cipher struct {
box []byte
key []byte
hash uint32
boxTmp []byte
n int
}
// NewRC4Cipher creates and returns a new rc4Cipher. The key argument should be the
@ -20,9 +20,8 @@ func NewRC4Cipher(key []byte) (*rc4Cipher, error) {
return nil, errors.New("qmc/cipher_rc4: invalid key size")
}
var c = rc4Cipher{key: key}
var c = rc4Cipher{key: key, n: n}
c.box = make([]byte, n)
c.boxTmp = make([]byte, n)
for i := 0; i < n; i++ {
c.box[i] = byte(i)
@ -39,7 +38,7 @@ func NewRC4Cipher(key []byte) (*rc4Cipher, error) {
func (c *rc4Cipher) getHashBase() {
c.hash = 1
for i := 0; i < len(c.key); i++ {
for i := 0; i < c.n; i++ {
v := uint32(c.key[i])
if v == 0 {
continue
@ -52,7 +51,10 @@ func (c *rc4Cipher) getHashBase() {
}
}
const rc4SegmentSize = 5120
const (
rc4SegmentSize = 5120
rc4FirstSegmentSize = 128
)
func (c *rc4Cipher) Decrypt(src []byte, offset int) {
toProcess := len(src)
@ -64,10 +66,10 @@ func (c *rc4Cipher) Decrypt(src []byte, offset int) {
return toProcess == 0
}
if offset < 128 {
if offset < rc4FirstSegmentSize {
blockSize := toProcess
if blockSize > 128-offset {
blockSize = 128 - offset
if blockSize > rc4FirstSegmentSize-offset {
blockSize = rc4FirstSegmentSize - offset
}
c.encFirstSegment(src[:blockSize], offset)
if markProcess(blockSize) {
@ -80,8 +82,7 @@ func (c *rc4Cipher) Decrypt(src []byte, offset int) {
if blockSize > rc4SegmentSize-offset%rc4SegmentSize {
blockSize = rc4SegmentSize - offset%rc4SegmentSize
}
k := src[processed : processed+blockSize]
c.encASegment(k, offset)
c.encASegment(src[processed:processed+blockSize], offset)
if markProcess(blockSize) {
return
}
@ -96,38 +97,28 @@ func (c *rc4Cipher) Decrypt(src []byte, offset int) {
}
}
func (c *rc4Cipher) encFirstSegment(buf []byte, offset int) {
n := len(c.box)
for i := 0; i < len(buf); i++ {
idx1 := offset + i
segmentID := int(c.key[idx1%n])
idx2 := int(float64(c.hash) / float64((idx1+1)*segmentID) * 100.0)
buf[i] ^= c.key[idx2%n]
buf[i] ^= c.key[c.getSegmentSkip(offset+i)]
}
}
func (c *rc4Cipher) encASegment(buf []byte, offset int) {
n := len(c.box)
copy(c.boxTmp, c.box)
segmentID := (offset / rc4SegmentSize) & 0x1FF
if n <= segmentID {
return
}
idx2 := int64(float64(c.hash) /
float64((offset/rc4SegmentSize+1)*int(c.key[segmentID])) *
100.0)
skipLen := int((idx2 & 0x1FF) + int64(offset%rc4SegmentSize))
box := make([]byte, c.n)
copy(box, c.box)
j, k := 0, 0
skipLen := (offset % rc4SegmentSize) + c.getSegmentSkip(offset/rc4SegmentSize)
for i := -skipLen; i < len(buf); i++ {
j = (j + 1) % n
k = (int(c.boxTmp[j]) + k) % n
c.boxTmp[j], c.boxTmp[k] = c.boxTmp[k], c.boxTmp[j]
j = (j + 1) % c.n
k = (int(box[j]) + k) % c.n
box[j], box[k] = box[k], box[j]
if i >= 0 {
buf[i] ^= c.boxTmp[int(c.boxTmp[j])+int(c.boxTmp[k])%n]
buf[i] ^= box[(int(box[j])+int(box[k]))%c.n]
}
}
}
func (c *rc4Cipher) getSegmentSkip(id int) int {
seed := int(c.key[id%c.n])
idx := int(float64(c.hash) / float64((id+1)*seed) * 100.0)
return idx % c.n
}

15
algo/qmc/cipher_rc4_test.go
View File

@ -40,6 +40,21 @@ func Test_rc4Cipher_Decrypt(t *testing.T) {
})
}
func BenchmarkRc4Cipher_Decrypt(b *testing.B) {
key, raw, _, err := loadTestRC4CipherData()
if err != nil {
b.Fatalf("load testing data failed: %s", err)
}
c, err := NewRC4Cipher(key)
if err != nil {
b.Errorf("init rc4Cipher failed: %s", err)
return
}
b.ResetTimer()
for i := 0; i < b.N; i++ {
c.Decrypt(raw, 0)
}
}
func Test_rc4Cipher_encFirstSegment(t *testing.T) {
key, raw, target, err := loadTestRC4CipherData()