From a52250bcf8d9043dc55cf92bc7c53fd77aa2cd39 Mon Sep 17 00:00:00 2001
From: Noah Metz <noah@metznet.ca>
Date: Wed, 3 Apr 2024 19:31:58 -0600
Subject: [PATCH] Added session connect packet

---
 client.go      |  8 ++---
 packet.go      | 80 ++++++++++++++++++++++++++++++++++++++++++++++++++
 packet_test.go | 17 +++++++++++
 server.go      | 15 ----------
 4 files changed, 99 insertions(+), 21 deletions(-)

diff --git a/client.go b/client.go
index 1a53223..aa3e65b 100644
--- a/client.go
+++ b/client.go
@@ -10,13 +10,9 @@ type Client struct {
   Key ed25519.PrivateKey
 }
 
-func KeyID(key ed25519.PublicKey) ClientID {
-  hash := sha512.Sum512([]byte(key))
-  return (ClientID)((hash)[0:16])
-}
-
 func(client Client) ID() ClientID { 
-  return KeyID(client.Key.Public().(ed25519.PublicKey))
+  hash := sha512.Sum512([]byte(client.Key.Public().(ed25519.PublicKey)))
+  return (ClientID)(hash[0:16])
 }
 
 func NewClient(key ed25519.PrivateKey) (Client, error) {
diff --git a/packet.go b/packet.go
index 5081dc6..ce1141a 100644
--- a/packet.go
+++ b/packet.go
@@ -4,11 +4,91 @@ import (
 	"crypto/ed25519"
 	"crypto/rand"
 	"crypto/sha512"
+	"encoding/binary"
+
 	"fmt"
+  "slices"
 
 	"filippo.io/edwards25519"
 )
 
+type PacketType uint16
+const (
+  ID_LENGTH = 16
+  PUBKEY_LENGTH = 32
+  ECDH_LENGTH = 32
+  SIGNATURE_LENGTH = 64
+  HMAC_LENGTH = 64
+
+  SESSION_OPEN_LENGTH = PUBKEY_LENGTH + ECDH_LENGTH + SIGNATURE_LENGTH
+  SESSION_CONNECT_LENGTH = ID_LENGTH + 2 + HMAC_LENGTH // + return addr string length
+
+  SESSION_OPEN PacketType = iota
+  SESSION_CONNECT
+  SESSION_CLOSE
+  SESSION_CLOSED
+  SESSION_DATA
+)
+
+func SessionKeyID(session_secret []byte) SessionID {
+  hash := sha512.Sum512(session_secret)
+  return (SessionID)(hash[0:16])
+}
+
+func NewSessionConnect(address string, session_secret []byte) []byte {
+  packet := make([]byte, SESSION_CONNECT_LENGTH + len(address))
+  cur := 0
+
+  session_id := [16]byte(SessionKeyID(session_secret))
+  copy(packet[cur:], session_id[:])
+  cur += ID_LENGTH
+
+  binary.BigEndian.PutUint16(packet[cur:], uint16(len(address)))
+  cur += 2
+  
+  copy(packet[cur:], []byte(address))
+  cur += len(address)
+
+  hmac := sha512.Sum512(append(packet[:cur], session_secret...))
+  copy(packet[cur:], hmac[:])
+
+  return packet
+}
+
+func ParseSessionConnect(session_connect []byte, session_secret []byte) (SessionID, string, error) {
+  if len(session_connect) < SESSION_CONNECT_LENGTH {
+    return SessionID{}, "", fmt.Errorf("Bad session connect length: %d/%d", len(session_connect), SESSION_CONNECT_LENGTH)
+  }
+
+  cur := 0
+
+  session_id := SessionID(session_connect[cur:cur+ID_LENGTH])
+  cur += ID_LENGTH
+
+  address_length := int(binary.BigEndian.Uint16(session_connect[cur:cur+2]))
+  cur += 2
+
+  if len(session_connect) != (SESSION_CONNECT_LENGTH + address_length) {
+    return SessionID{}, "", fmt.Errorf("Bad session connect length: %d/%d", len(session_connect), SESSION_CONNECT_LENGTH + address_length)
+  }
+
+  address := string(session_connect[cur:cur+address_length])
+  cur += address_length
+
+  hmac_digest := make([]byte, cur)
+  copy(hmac_digest, session_connect[:cur])
+
+  hmac := session_connect[cur:cur+HMAC_LENGTH]
+  cur += HMAC_LENGTH
+
+  calculated_hmac := sha512.Sum512(append(hmac_digest, session_secret...))
+  if slices.Compare(hmac, calculated_hmac[:]) != 0 {
+    return SessionID{}, "", fmt.Errorf("Session connect bad HMAC")
+  }
+
+  return session_id, address, nil
+}
+
 func NewSessionOpen(key ed25519.PrivateKey) ([]byte, ed25519.PrivateKey, error) {
   if key == nil {
     return nil, nil, fmt.Errorf("Cannot create a SESSION_OPEN packet without a key")
diff --git a/packet_test.go b/packet_test.go
index 1fdb6d1..5c02537 100644
--- a/packet_test.go
+++ b/packet_test.go
@@ -49,3 +49,20 @@ func TestECDH(t *testing.T) {
     t.Fatalf("Server and Client secrets do not match")
   }
 }
+
+func TestSessionConnect(t *testing.T) {
+  secret := make([]byte, 32)
+  test_addr := "test_addr"
+
+  session_connect := NewSessionConnect(test_addr, secret)
+  parsed_session_id, parsed_addr, err := ParseSessionConnect(session_connect, secret)
+  fatalErr(t, err)
+
+  if parsed_addr != test_addr {
+    t.Fatalf("Parsed address(%s) does not match test address(%s)", parsed_addr, test_addr)
+  }
+
+  if parsed_session_id != SessionKeyID(secret) {
+    t.Fatalf("Parsed session ID %s does not match original %s", parsed_session_id, SessionKeyID(secret))
+  }
+}
diff --git a/server.go b/server.go
index 81c7d22..d8efb4f 100644
--- a/server.go
+++ b/server.go
@@ -13,21 +13,6 @@ import (
 
 const (
  SERVER_UDP_BUFFER_SIZE = 2048
-
- PUBKEY_LENGTH = 32
- ECDH_LENGTH = 32
- SIGNATURE_LENGTH = 64
- SESSION_OPEN_LENGTH = PUBKEY_LENGTH + ECDH_LENGTH + SIGNATURE_LENGTH
-)
-
-type PacketType uint16
-const (
-  SESSION_OPEN PacketType = iota
-  SESSION_AUTHENTICATE
-  SESSION_CONNECT
-  SESSION_CLOSE
-  SESSION_CLOSED
-  SESSION_DATA
 )
 
 /*