Stun done

webrtc/stun.nim

@@ -1,8 +1,18 @@
-import bitops
+# Nim-WebRTC
+# Copyright (c) 2023 Status Research & Development GmbH
+# Licensed under either of
+#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
+#  * MIT license ([LICENSE-MIT](LICENSE-MIT))
+# at your option.
+# This file may not be copied, modified, or distributed except according to
+# those terms.
+
+import bitops, strutils
 import chronos,
        chronicles,
        binary_serialization,
-       stew/objects
+       stew/objects,
+       stew/byteutils
 import stunattributes
 
 export binary_serialization
@@ -18,13 +28,13 @@ const
   BindingResponse = 0x0101'u16
 
 proc decode(T: typedesc[RawStunAttribute], cnt: seq[byte]): seq[RawStunAttribute] =
-  const val = @[0, 3, 2, 1]
+  const pad = @[0, 3, 2, 1]
   var padding = 0
   while padding < cnt.len():
     let attr = Binary.decode(cnt[padding ..^ 1], RawStunAttribute)
     result.add(attr)
     padding += 4 + attr.value.len()
-    padding += val[padding mod 4]
+    padding += pad[padding mod 4]
 
 type
 #  Stun Header
@@ -50,7 +60,7 @@ type
   RawStunMessage = object
     msgType: uint16
     # it.conten.len() + 8 Because the Fingerprint is added after the encoding
-    length* {.bin_value: it.content.len() + 8.}: uint16
+    length* {.bin_value: it.content.len().}: uint16
     magicCookie: uint32
     transactionId: array[12, byte]
     content* {.bin_len: it.length.}: seq[byte]
@@ -71,36 +81,56 @@ proc getAttribute(attrs: seq[RawStunAttribute], typ: uint16): Option[seq[byte]]
 proc isMessage*(T: typedesc[Stun], msg: seq[byte]): bool =
   msg.len >= msgHeaderSize and msg[4..<8] == magicCookieSeq and bitand(0xC0'u8, msg[0]) == 0'u8
 
+proc addLength(msgEncoded: var seq[byte], length: uint16) =
+  let
+    hi = (length div 256'u16).uint8
+    lo = (length mod 256'u16).uint8
+  msgEncoded[2] = msgEncoded[2] + hi
+  if msgEncoded[3].int + lo.int >= 256:
+    msgEncoded[2] = msgEncoded[2] + 1
+    msgEncoded[3] = ((msgEncoded[3].int + lo.int) mod 256).uint8
+  else:
+    msgEncoded[3] = msgEncoded[3] + lo
+
 proc decode*(T: typedesc[StunMessage], msg: seq[byte]): StunMessage =
   let smi = Binary.decode(msg, RawStunMessage)
   return T(msgType: smi.msgType,
            transactionId: smi.transactionId,
            attributes: RawStunAttribute.decode(smi.content))
 
-proc encode*(msg: StunMessage): seq[byte] =
-  const val = @[0, 3, 2, 1]
+proc encode*(msg: StunMessage, userOpt: Option[seq[byte]]): seq[byte] =
+  const pad = @[0, 3, 2, 1]
   var smi = RawStunMessage(msgType: msg.msgType,
                              magicCookie: magicCookie,
                              transactionId: msg.transactionId)
   for attr in msg.attributes:
     smi.content.add(Binary.encode(attr))
-    smi.content.add(newSeq[byte](val[smi.content.len() mod 4]))
+    smi.content.add(newSeq[byte](pad[smi.content.len() mod 4]))
 
   result = Binary.encode(smi)
+
+  if userOpt.isSome():
+    let username = string.fromBytes(userOpt.get())
+    let usersplit = username.split(":")
+    if usersplit.len() == 2 and usersplit[0].startsWith("libp2p+webrtc+v1/"):
+      result.addLength(24)
+      result.add(Binary.encode(MessageIntegrity.encode(result, toBytes(usersplit[0]))))
+
+  result.addLength(8)
   result.add(Binary.encode(Fingerprint.encode(result)))
 
 proc getResponse*(T: typedesc[Stun], msg: seq[byte],
-    ta: TransportAddress): Option[StunMessage] =
+    ta: TransportAddress): Option[seq[byte]] =
   if ta.family != AddressFamily.IPv4 and ta.family != AddressFamily.IPv6:
-    return none(StunMessage)
+    return none(seq[byte])
   let sm =
     try:
       StunMessage.decode(msg)
     except CatchableError as exc:
-      return none(StunMessage)
+      return none(seq[byte])
 
   if sm.msgType != BindingRequest:
-    return none(StunMessage)
+    return none(seq[byte])
 
   var res = StunMessage(msgType: BindingResponse,
                         transactionId: sm.transactionId)
@@ -113,10 +143,10 @@ proc getResponse*(T: typedesc[Stun], msg: seq[byte],
   if unknownAttr.len() > 0:
     res.attributes.add(ErrorCode.encode(ECUnknownAttribute))
     res.attributes.add(UnknownAttribute.encode(unknownAttr))
-    return some(res)
+    return some(res.encode(sm.attributes.getAttribute(AttrUsername.uint16)))
 
   res.attributes.add(XorMappedAddress.encode(ta, sm.transactionId))
-  return some(res)
+  return some(res.encode(sm.attributes.getAttribute(AttrUsername.uint16)))
 
 proc new*(T: typedesc[Stun]): T =
   result = T()

webrtc/stunattributes.nim

@@ -1,3 +1,12 @@
+# Nim-WebRTC
+# Copyright (c) 2023 Status Research & Development GmbH
+# Licensed under either of
+#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
+#  * MIT license ([LICENSE-MIT](LICENSE-MIT))
+# at your option.
+# This file may not be copied, modified, or distributed except according to
+# those terms.
+
 import sequtils, typetraits
 import binary_serialization,
        stew/byteutils,
@@ -150,3 +159,15 @@ proc encode*(T: typedesc[XorMappedAddress], ta: TransportAddress,
   result = RawStunAttribute(attributeType: AttrXORMappedAddress.uint16,
                             length: value.len().uint16,
                             value: value)
+
+# Message Integrity
+
+type
+  MessageIntegrity* = object
+    msgInt: seq[byte]
+
+proc encode*(T: typedesc[MessageIntegrity], msg: seq[byte], key: seq[byte]): RawStunAttribute =
+  let value = Binary.encode(T(msgInt: hmacSha1(key, msg)))
+  result = RawStunAttribute(attributeType: AttrMessageIntegrity.uint16,
+                            length: value.len().uint16,
+                            value: value)

webrtc/webrtc.nim

@@ -1,3 +1,12 @@
+# Nim-WebRTC
+# Copyright (c) 2023 Status Research & Development GmbH
+# Licensed under either of
+#  * Apache License, version 2.0, ([LICENSE-APACHE](LICENSE-APACHE))
+#  * MIT license ([LICENSE-MIT](LICENSE-MIT))
+# at your option.
+# This file may not be copied, modified, or distributed except according to
+# those terms.
+
 import chronos, chronicles
 import stun
 
@@ -17,9 +26,8 @@ proc new*(T: typedesc[WebRTC], port: uint16 = 42657): T =
       msg = udp.getMessage()
     if Stun.isMessage(msg):
       let res = Stun.getResponse(msg, address)
-      echo res
       if res.isSome():
-        await udp.sendTo(address, res.get().encode())
+        await udp.sendTo(address, res.get())
 
     trace "onReceive", isStun = Stun.isMessage(msg)
     if not fut.completed(): fut.complete()