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48 lines
1.8 KiB
Go
48 lines
1.8 KiB
Go
package client
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import (
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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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)
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const (
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UNORDERED_FLAG = 0x01 // 0000 0001
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)
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type authenticationPayload struct {
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randPubKey [32]byte
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ciphertextWithTag [64]byte
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}
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// makeAuthenticationPayload generates the ephemeral key pair, calculates the shared secret, and then compose and
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// encrypt the authenticationPayload
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func makeAuthenticationPayload(authInfo AuthInfo) (ret authenticationPayload, sharedSecret [32]byte) {
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/*
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Authentication data:
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+----------+----------------+---------------------+-------------+--------------+--------+------------+
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| _UID_ | _Proxy Method_ | _Encryption Method_ | _Timestamp_ | _Session Id_ | _Flag_ | _reserved_ |
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+----------+----------------+---------------------+-------------+--------------+--------+------------+
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| 16 bytes | 12 bytes | 1 byte | 8 bytes | 4 bytes | 1 byte | 6 bytes |
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+----------+----------------+---------------------+-------------+--------------+--------+------------+
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*/
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ephPv, ephPub, _ := ecdh.GenerateKey(authInfo.WorldState.Rand)
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copy(ret.randPubKey[:], ecdh.Marshal(ephPub))
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plaintext := make([]byte, 48)
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copy(plaintext, authInfo.UID)
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copy(plaintext[16:28], authInfo.ProxyMethod)
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plaintext[28] = authInfo.EncryptionMethod
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binary.BigEndian.PutUint64(plaintext[29:37], uint64(authInfo.WorldState.Now().Unix()))
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binary.BigEndian.PutUint32(plaintext[37:41], authInfo.SessionId)
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if authInfo.Unordered {
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plaintext[41] |= UNORDERED_FLAG
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}
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copy(sharedSecret[:], ecdh.GenerateSharedSecret(ephPv, authInfo.ServerPubKey))
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ciphertextWithTag, _ := util.AESGCMEncrypt(ret.randPubKey[:12], sharedSecret[:], plaintext)
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copy(ret.ciphertextWithTag[:], ciphertextWithTag[:])
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return
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}
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