mirror of
https://github.com/cbeuw/Cloak.git
synced 2024-10-23 15:46:25 +00:00
75 lines
2.0 KiB
Go
75 lines
2.0 KiB
Go
package server
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import (
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"bytes"
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"crypto"
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"crypto/sha256"
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"encoding/binary"
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"github.com/cbeuw/Cloak/internal/ecdh"
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"github.com/cbeuw/Cloak/internal/util"
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"log"
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)
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const SESSION_TICKET_LEN = 192
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const PUB_KEY_LEN = 32
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const AUTH_TAG_LEN = 16
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const USED_STAGNO_LEN = 16 + 16 + 1
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func decryptSessionTicket(staticPv crypto.PrivateKey, ticket []byte) (UID []byte, proxyMethod string, encryptionMethod byte, tthKey []byte) {
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// sessionTicket: [marshalled ephemeral pub key 32 bytes][encrypted UID 16 bytes, proxy method 16 bytes, encryption method 1 byte][reserved 111 bytes][padding 111 bytes]
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ephPub, _ := ecdh.Unmarshal(ticket[0:PUB_KEY_LEN])
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tthKey = ecdh.GenerateSharedSecret(staticPv, ephPub)
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plain, err := util.AESGCMDecrypt(ticket[0:12], tthKey, ticket[PUB_KEY_LEN:])
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if err != nil {
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return
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}
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return plain[0:16], string(bytes.Trim(plain[16:32], "\x00")), plain[32], tthKey
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}
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func validateRandom(random []byte, UID []byte, time int64) (bool, uint32) {
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t := make([]byte, 8)
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binary.BigEndian.PutUint64(t, uint64(time/(12*60*60)))
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front := random[0:16]
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preHash := make([]byte, 56)
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copy(preHash[0:32], UID)
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copy(preHash[32:40], t)
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copy(preHash[40:56], front)
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h := sha256.New()
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h.Write(preHash)
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sessionID := binary.BigEndian.Uint32(front[0:4])
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return bytes.Equal(h.Sum(nil)[0:16], random[16:32]), sessionID
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}
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func TouchStone(ch *ClientHello, sta *State) (isCK bool, UID []byte, sessionID uint32, proxyMethod string, encryptionMethod byte, tthKey []byte) {
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var random [32]byte
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copy(random[:], ch.random)
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sta.usedRandomM.Lock()
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used := sta.usedRandom[random]
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sta.usedRandom[random] = int(sta.Now().Unix())
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sta.usedRandomM.Unlock()
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if used != 0 {
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log.Println("Replay! Duplicate random")
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return
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}
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ticket := ch.extensions[[2]byte{0x00, 0x23}]
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if len(ticket) < PUB_KEY_LEN+USED_STAGNO_LEN+AUTH_TAG_LEN {
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return
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}
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UID, proxyMethod, encryptionMethod, tthKey = decryptSessionTicket(sta.staticPv, ticket)
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if len(UID) < 16 {
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return
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}
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isCK, sessionID = validateRandom(ch.random, UID, sta.Now().Unix())
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if !isCK {
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return
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}
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return
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}
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