71 lines
2.8 KiB
Go
71 lines
2.8 KiB
Go
package shared
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import "encoding/binary"
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const PROTO_VERSION uint16 = 1
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// pubKey - public key generated by the client
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// privKey - private key generated by the client
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// serverPubKey - pre-shared public key used for authenticating the server
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// serverPrivKey - long-term private key used for authenticating the server
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// sessionKey - per-peer symmetrical key derived via HPKE for encrypting unicast packets
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// multicastKey - key shared between everyone for encrypting multicast packets
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// authSecret - secret assigned to a client for authenticating subsequent requests
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// SYM = XChaCha20-Poly1305 with nonce prepended
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// HMAC = HMAC-SHA-256
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// hpke = HPKE(MLKEM768X25519, ChaCha20Poly1305, HKDF-SHA-256)
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// ds = ML-DSA
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// packet format
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// [ version - 2 bytes ] [ type - 2 bytes ] [ payload - see below ]
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const (
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_ uint16 = iota
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// (client -> server) requests a challenge to prove the ownership of the privKey
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// [ pubKey - 1216 bytes ]
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REQ_GET_CHALLENGE
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// (server -> client) provides an encrypted authSecret
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// [ ds.Sign(serverPrivKey, rest) - 2420 bytes ] [ HPKE(pubKey, authSecret) - 1168 bytes ]
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RESP_GET_CHALLENGE
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// (client -> server) requests an IP
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// [ HMAC(authSecret, pubKey) - 32 bytes ] [ pubKey - 1216 bytes ]
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REQ_REGISTER
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// (server -> client) returns the assigned IP and encrypted multicastKey
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// [ ds.Sign(serverPrivKey, rest) - 2420 bytes ] [ ip - 16 bytes ] [ hpke.Seal(pubKey, multicastKey) - 1168 bytes ]
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RESP_REGISTER
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// (client -> server) requests peer's pubKey from the server for encapsulation
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// [ HMAC(authSecret, rest) - 32 bytes ] [ ip - 16 bytes ]
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REQ_GET_PUBKEY
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// (server -> client) provides requested pubKey
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// [ ds.Sign(serverPrivKey, rest) - 2420 bytes ] [ ip - 16 bytes ] [ pubKey - 1216 bytes ]
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RESP_GET_PUBKEY
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// (client -> server -> client2) establishes a sessionKey with another peer
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// [ HMAC(authSecret, rest) - 32 bytes ] [ destIP - 16 bytes ] [ srcIP - 16 bytes ] [ hpke.Encap(pubKey) - 1120 bytes ]
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REQ_ESTABLISH
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// (client2 -> server -> client) acknowledges the sessionKey was established
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// [ HMAC(authSecret, rest) - 32 bytes ] [ destIP - 16 bytes ] [ srcIP - 16 bytes ]
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RESP_ESTABLISH
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// (client -> server -> client2) relays an encrypted packet to a specified peer
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// [ HMAC(authSecret, rest) - 32 bytes ] [ destIP - 16 bytes ] [ srcIP - 16 bytes ] [ SYM(sessionKey, pkt) ]
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UNICAST_PKT
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// (client -> server -> *) broadcasts an encrypted packet
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// [ HMAC(authSecret, rest) - 32 bytes ] [ srcIP - 16 bytes ] [ SYM(multicastKey, pkt) ]
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BROADCAST_PKT
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)
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func BuildPkt(pktType uint16, parts ...[]byte) []byte {
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var total int
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for _, p := range parts {
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total += len(p)
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}
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out := make([]byte, 4, 4+total)
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binary.LittleEndian.PutUint16(out[0:], PROTO_VERSION)
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binary.LittleEndian.PutUint16(out[2:], pktType)
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for _, p := range parts {
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out = append(out, p...)
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}
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return out
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}
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