From def29259004306cf65f0504eb5a65949d03fba2a Mon Sep 17 00:00:00 2001 From: MengYX Date: Fri, 17 Dec 2021 04:31:58 +0800 Subject: [PATCH] feat(QMCv2): better rc4 cipher --- algo/qmc/cipher_rc4.go | 63 ++++++++++++++++--------------------- algo/qmc/cipher_rc4_test.go | 15 +++++++++ 2 files changed, 42 insertions(+), 36 deletions(-) diff --git a/algo/qmc/cipher_rc4.go b/algo/qmc/cipher_rc4.go index 9b140bf..4485076 100644 --- a/algo/qmc/cipher_rc4.go +++ b/algo/qmc/cipher_rc4.go @@ -6,10 +6,10 @@ import ( // A rc4Cipher is an instance of RC4 using a particular key. type rc4Cipher struct { - box []byte - key []byte - hash uint32 - boxTmp []byte + box []byte + key []byte + hash uint32 + 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 +} diff --git a/algo/qmc/cipher_rc4_test.go b/algo/qmc/cipher_rc4_test.go index 7a1519d..c5f4a23 100644 --- a/algo/qmc/cipher_rc4_test.go +++ b/algo/qmc/cipher_rc4_test.go @@ -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()