// consts.go - consts for xsnet

// Copyright (c) 2017-2020 Russell Magee
// Licensed under the terms of the MIT license (see LICENSE.mit in this
// distribution)
//
// golang implementation by Russ Magee (rmagee_at_gmail.com)
package xsnet

// KEX algorithm values
//
// Specified (in string form) as the extensions parameter
// to xsnet.Dial()
// Alg is sent in a uint8 so there are up to 256 possible
const (
	KEX_HERRADURA256 = iota // this MUST be first for default if omitted in ctor
	KEX_HERRADURA512
	KEX_HERRADURA1024
	KEX_HERRADURA2048
	KEX_resvd4
	KEX_resvd5
	KEX_resvd6
	KEX_resvd7
	KEX_KYBER512
	KEX_KYBER768
	KEX_KYBER1024
	KEX_resvd11
	KEX_NEWHOPE
	KEX_NEWHOPE_SIMPLE // 'NewHopeLP-Simple' - https://eprint.iacr.org/2016/1157
	KEX_resvd14
	KEX_resvd15
	KEX_FRODOKEM_1344AES
	KEX_FRODOKEM_1344SHAKE
	KEX_FRODOKEM_976AES
	KEX_FRODOKEM_976SHAKE
	KEX_invalid = 255
)

// Sent from client to server in order to specify which
// algo shall be used (see xsnet.KEX_HERRADURA256, ...)
type KEXAlg uint8

// Extended exit status codes - indicate comm/pty issues
// rather than remote end normal UNIX exit codes
const (
	CSENone            = 1024 + iota
	CSETruncCSO        // No CSOExitStatus in payload
	CSEStillOpen       // Channel closed unexpectedly
	CSEExecFail        // cmd.Start() (exec) failed
	CSEPtyExecFail     // pty.Start() (exec w/pty) failed
	CSEPtyGetNameFail  // failed to obtain pty name
	CSEKEXAlgDenied    // server rejected proposed KEX alg
	CSECipherAlgDenied // server rejected proposed Cipher alg
	CSEHMACAlgDenied   // server rejected proposed HMAC alg
	CSEConnDead        // connection keepalives expired
	CSELoginTimeout
)

// Extended (>255 UNIX exit status) codes
// This indicate channel-related or internal errors
type CSExtendedCode uint32

// Channel Status/Op bytes - packet types
const (
	// Main connection/session control
	CSONone        = iota // No error, normal packet
	CSOHmacInvalid        // HMAC mismatch detected on remote end
	CSOTermSize           // set term size (rows:cols)
	CSOExitStatus         // Remote cmd exit status
	CSOChaff              // Dummy packet, do not pass beyond decryption

	// Tunnel setup/control/status
	CSOTunSetup     // client -> server tunnel setup request (dstport)
	CSOTunSetupAck  // server -> client tunnel setup ack
	CSOTunRefused   // server -> client: tunnel rport connection refused
	CSOTunData      // packet contains tunnel data [rport:data]
	CSOTunKeepAlive // client tunnel heartbeat
	CSOTunDisconn   // server -> client: tunnel rport disconnected
	CSOTunHangup    // client -> server: tunnel lport hung up
	CSOKeepAlive    // bidir keepalive packet to monitor main connection
	CSORekey        // TODO: rekey/re-select session cipher/hash algs
)

// TunEndpoint.tunCtl control values - used to control workers for client
// or server tunnels depending on the code
const (
	TunCtl_Client_Listen = 'a'
	// [CSOTunAccept]
	// status: server has ack'd tun setup request
	// action: client should accept (after re-listening, if required) on lport

	TunCtl_Server_Dial = 'd' // server has dialled OK, client side can accept() conns
	// [CSOTunAccept]
	// status: client wants to open tunnel to rport
	// action:server side should dial() rport on client's behalf
)

// Channel status Op byte type (see CSONone, ... and CSENone, ...)
type CSOType uint32

// TODO: this should be small (max unfragmented packet size?)
const MAX_PAYLOAD_LEN = 2*1024*1024*1024 - 1

// Session symmetric crypto algs
const (
	CAlgAES256     = iota
	CAlgTwofish128 // golang.org/x/crypto/twofish
	CAlgBlowfish64 // golang.org/x/crypto/blowfish
	CAlgCryptMT1   //cryptmt using mtwist64
	CAlgChaCha20_12
	CAlgHopscotch
	CAlgNoneDisallowed
)

// Available ciphers for hkex.Conn
type CSCipherAlg uint32

// Session packet auth HMAC algs
const (
	HmacSHA256 = iota
	HmacSHA512
	HmacNoneDisallowed
)

// Conn opts outside of basic kex/cipher/hmac connect config
const (
	CONone              = iota
	CORemodulateShields // if set, rekeying also reselects random cipher/hmac alg
)

type COValue uint32

// Available HMACs for hkex.Conn
type CSHmacAlg uint32

// Some bounds-checking consts
const (
	REKEY_SECS_MIN       = 1
	REKEY_SECS_MAX       = 28800  // 8 hours
	CHAFF_FREQ_MSECS_MIN = 1
	CHAFF_FREQ_MSECS_MAX = 300000 // 5 minutes
)

const XS_ID_AUTHTOKFILE = ".config/xs/.xs_id"