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Optimise deobfs

This commit is contained in:
Qian Wang 2019-08-07 17:53:34 +01:00
parent e3de2b9852
commit 586cc5ebb6
1 changed files with 18 additions and 11 deletions
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29
internal/multiplex/obfs.go
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@ -74,12 +74,14 @@ func MakeObfs(salsaKey [32]byte, payloadCipher cipher.AEAD) Obfser {
func MakeDeobfs(salsaKey [32]byte, payloadCipher cipher.AEAD) Deobfser {
deobfs := func(in []byte) (*Frame, error) {
if len(in) < 5+HEADER_LEN+8 {
return nil, errors.New("Input cannot be shorter than 33 bytes")
return nil, errors.New("Input cannot be shorter than 25 bytes")
}
peeled := in[5:]
header := peeled[0:12]
payload := peeled[12:]
peeled := make([]byte, len(in)-5)
copy(peeled, in[5:])
header := peeled[:12]
pldWithOverHead := peeled[12:] // plaintext + potential overhead
nonce := peeled[len(peeled)-8:]
salsa20.XORKeyStream(header, header, nonce, &salsaKey)
@ -89,20 +91,25 @@ func MakeDeobfs(salsaKey [32]byte, payloadCipher cipher.AEAD) Deobfser {
closing := header[8]
extraLen := header[9]
outputLen := len(payload) - int(extraLen)
if outputLen < 0 {
return nil, errors.New("extra length is greater than total payload length")
usefulPayloadLen := len(pldWithOverHead) - int(extraLen)
if usefulPayloadLen < 0 {
return nil, errors.New("extra length is greater than total pldWithOverHead length")
}
outputPayload := make([]byte, outputLen)
var outputPayload []byte
if payloadCipher == nil {
copy(outputPayload, payload)
if extraLen == 0 {
outputPayload = pldWithOverHead
} else {
plaintext, err := payloadCipher.Open(nil, header, payload, nil)
outputPayload = pldWithOverHead[:usefulPayloadLen]
}
} else {
_, err := payloadCipher.Open(pldWithOverHead[:0], header, pldWithOverHead, nil)
if err != nil {
return nil, err
}
copy(outputPayload, plaintext)
outputPayload = pldWithOverHead[:usefulPayloadLen]
}
ret := &Frame{