76 lines
1.3 KiB
Go
76 lines
1.3 KiB
Go
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package obfs
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import (
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"encoding/binary"
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"hash/crc32"
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"math/rand"
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)
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type randomHead struct {
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*Base
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firstRequest bool
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firstResponse bool
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headerSent bool
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buffer []byte
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}
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func init() {
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register("random_head", newRandomHead)
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}
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func newRandomHead(b *Base) Obfs {
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return &randomHead{Base: b}
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}
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func (r *randomHead) initForConn() Obfs {
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return &randomHead{
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Base: r.Base,
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firstRequest: true,
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firstResponse: true,
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}
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}
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func (r *randomHead) GetObfsOverhead() int {
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return 0
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}
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func (r *randomHead) Encode(b []byte) (encoded []byte, err error) {
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if !r.firstRequest {
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return b, nil
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}
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bSize := len(b)
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if r.headerSent {
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if bSize > 0 {
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d := make([]byte, len(r.buffer)+bSize)
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copy(d, r.buffer)
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copy(d[len(r.buffer):], b)
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r.buffer = d
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} else {
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encoded = r.buffer
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r.buffer = nil
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r.firstRequest = false
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}
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} else {
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size := rand.Intn(96) + 8
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encoded = make([]byte, size)
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rand.Read(encoded)
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crc := (0xFFFFFFFF - crc32.ChecksumIEEE(encoded[:size-4])) & 0xFFFFFFFF
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binary.LittleEndian.PutUint32(encoded[size-4:], crc)
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d := make([]byte, bSize)
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copy(d, b)
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r.buffer = d
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}
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r.headerSent = true
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return encoded, nil
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}
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func (r *randomHead) Decode(b []byte) ([]byte, bool, error) {
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if r.firstResponse {
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r.firstResponse = false
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return b, true, nil
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}
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return b, false, nil
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}
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