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61 lines
1.5 KiB
Go
61 lines
1.5 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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"log"
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"github.com/cbeuw/Cloak/internal/ecdh"
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"github.com/cbeuw/Cloak/internal/util"
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)
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// input ticket, return UID
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func decryptSessionTicket(staticPv crypto.PrivateKey, ticket []byte) ([]byte, uint32) {
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ephPub, _ := ecdh.Unmarshal(ticket[0:32])
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key := ecdh.GenerateSharedSecret(staticPv, ephPub)
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UIDsID := util.AESDecrypt(ticket[0:16], key, ticket[32:68])
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sessionID := binary.BigEndian.Uint32(UIDsID[32:36])
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return UIDsID[0:32], sessionID
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}
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func validateRandom(random []byte, UID []byte, time int64) bool {
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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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rdm := 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], rdm)
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h := sha256.New()
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h.Write(preHash)
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return bytes.Equal(h.Sum(nil)[0:16], random[16:32])
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}
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func TouchStone(ch *ClientHello, sta *State) (isSS bool, UID []byte, sessionID uint32) {
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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 false, nil, 0
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}
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ticket := ch.extensions[[2]byte{0x00, 0x23}]
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if len(ticket) < 68 {
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return false, nil, 0
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}
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UID, sessionID = decryptSessionTicket(sta.staticPv, ticket)
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isSS = validateRandom(ch.random, UID, sta.Now().Unix())
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if !isSS {
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return false, nil, 0
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}
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return
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}
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