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