feat: stun protocol & stun connection

.github/workflows/ci.yml

@@ -61,6 +61,6 @@ jobs:
         run: |
           nim --version
           nimble --version
-          # nimble test
+          nimble test
           # nim c examples/ping.nim
           # nim c examples/pong.nim

tests/runalltests.nim

@@ -0,0 +1,3 @@
+{.used.}
+
+import teststun

tests/teststun.nim

@@ -0,0 +1,36 @@
+import options
+import ../webrtc/stun/stun
+import ../webrtc/stun/stun_attributes
+import ./asyncunit
+
+suite "Stun message encoding/decoding":
+  test "Stun decoding":
+    let msg = @[ 0x00'u8, 0x01, 0x00, 0xa4, 0x21, 0x12, 0xa4, 0x42, 0x75, 0x6a, 0x58, 0x46, 0x42, 0x58, 0x4e, 0x72, 0x6a, 0x50, 0x4d, 0x2b, 0x00, 0x06, 0x00, 0x63, 0x6c, 0x69, 0x62, 0x70, 0x32, 0x70, 0x2b, 0x77, 0x65, 0x62, 0x72, 0x74, 0x63, 0x2b, 0x76, 0x31, 0x2f, 0x62, 0x71, 0x36, 0x67, 0x69, 0x43, 0x75, 0x4a, 0x38, 0x6e, 0x78, 0x59, 0x46, 0x4a, 0x36, 0x43, 0x63, 0x67, 0x45, 0x59, 0x58, 0x58, 0x2f, 0x78, 0x51, 0x58, 0x56, 0x4c, 0x74, 0x39, 0x71, 0x7a, 0x3a, 0x6c, 0x69, 0x62, 0x70, 0x32, 0x70, 0x2b, 0x77, 0x65, 0x62, 0x72, 0x74, 0x63, 0x2b, 0x76, 0x31, 0x2f, 0x62, 0x71, 0x36, 0x67, 0x69, 0x43, 0x75, 0x4a, 0x38, 0x6e, 0x78, 0x59, 0x46, 0x4a, 0x36, 0x43, 0x63, 0x67, 0x45, 0x59, 0x58, 0x58, 0x2f, 0x78, 0x51, 0x58, 0x56, 0x4c, 0x74, 0x39, 0x71, 0x7a, 0x00, 0xc0, 0x57, 0x00, 0x04, 0x00, 0x00, 0x03, 0xe7, 0x80, 0x2a, 0x00, 0x08, 0x86, 0x63, 0xfd, 0x45, 0xa9, 0xe5, 0x4c, 0xdb, 0x00, 0x24, 0x00, 0x04, 0x6e, 0x00, 0x1e, 0xff, 0x00, 0x08, 0x00, 0x14, 0x16, 0xff, 0x70, 0x8d, 0x97, 0x0b, 0xd6, 0xa3, 0x5b, 0xac, 0x8f, 0x4c, 0x85, 0xe6, 0xa6, 0xac, 0xaa, 0x7a, 0x68, 0x27, 0x80, 0x28, 0x00, 0x04, 0x79, 0x5e, 0x03, 0xd8 ]
+    let stunmsg = StunMessage.decode(msg)
+    check:
+      stunmsg.msgType == 1
+      stunmsg.transactionId.len() == 12
+      stunmsg.attributes.len() == 6
+      stunmsg.attributes[0].attributeType == 6 # AttrUsername
+      stunmsg.attributes[^1].attributeType == 0x8028 # AttrFingerprint
+
+  test "Stun encoding":
+    let transactionId: array[12, byte] = [1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12]
+    var msg = StunMessage(msgType: 0x0001'u16, transactionId: transactionId)
+    msg.attributes.add(ErrorCode.encode(ECUnknownAttribute))
+    let encoded = msg.encode()
+    let decoded = StunMessage.decode(encoded)
+    # cannot do `check msg == decoded` because encode add a Fingerprint
+    # attribute at the end
+    check:
+      decoded.msgType == 1
+      decoded.transactionId == transactionId
+      decoded.attributes.len() == 2
+      decoded.attributes[0].attributeType == 9 # AttrErrorCode
+      decoded.attributes[^1].attributeType == 0x8028 # AttrFingerprint
+
+  test "Error while decoding":
+    let msgLengthFailed = @[ 0x00'u8, 0x01, 0x00, 0xa4, 0x21, 0x12, 0xa4, 0x42, 0x75, 0x6a, 0x58, 0x46, 0x42, 0x58, 0x4e, 0x72, 0x6a, 0x50, 0x4d ]
+    expect AssertionDefect: discard StunMessage.decode(msgLengthFailed)
+    let msgAttrFailed = @[ 0x00'u8, 0x01, 0x00, 0x08, 0x21, 0x12, 0xa4, 0x42, 0x75, 0x6a, 0x58, 0x46, 0x42, 0x58, 0x4e, 0x72, 0x6a, 0x50, 0x4d, 0x2b, 0x28, 0x00, 0x05, 0x79, 0x5e, 0x03, 0xd8 ]
+    expect AssertionDefect: discard StunMessage.decode(msgAttrFailed)

webrtc.nimble

@@ -33,5 +33,5 @@ proc runTest(filename: string) =
   exec excstr & " -r " & " tests/" & filename
   rmFile "tests/" & filename.toExe
 
-# task test, "Run test":
-#   runTest("runalltests")
+task test, "Run test":
+  runTest("runalltests")

webrtc/stun/stun.nim

@@ -0,0 +1,151 @@
+# Nim-WebRTC
+# Copyright (c) 2024 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/byteutils
+import stun_attributes
+
+export binary_serialization
+
+logScope:
+  topics = "webrtc stun"
+
+const
+  msgHeaderSize = 20
+  magicCookieSeq = @[ 0x21'u8, 0x12, 0xa4, 0x42 ]
+  magicCookie = 0x2112a442
+  BindingRequest = 0x0001'u16
+  BindingResponse = 0x0101'u16
+
+proc decode(T: typedesc[RawStunAttribute], cnt: seq[byte]): seq[RawStunAttribute] =
+  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 += pad[padding mod 4]
+
+type
+#  Stun Header
+#  0                   1                   2                   3
+#  0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+# |0 0|     STUN Message Type     |         Message Length        |
+# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+# |                         Magic Cookie                          |
+# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+# |                                                               |
+# |                     Transaction ID (96 bits)                  |
+# |                                                               |
+# +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
+# Message type:
+#   0x0001: Binding Request
+#   0x0101: Binding Response
+#   0x0111: Binding Error Response
+#   0x0002: Shared Secret Request
+#   0x0102: Shared Secret Response
+#   0x0112: Shared Secret Error Response
+
+  RawStunMessage = object
+    msgType: uint16
+    length* {.bin_value: it.content.len().}: uint16
+    magicCookie: uint32
+    transactionId: array[12, byte] # Down from 16 to 12 bytes in RFC5389
+    content* {.bin_len: it.length.}: seq[byte]
+
+  StunMessage* = object
+    msgType*: uint16
+    transactionId*: array[12, byte]
+    attributes*: seq[RawStunAttribute]
+
+  Stun* = object
+
+proc getAttribute(attrs: seq[RawStunAttribute], typ: uint16): Option[seq[byte]] =
+  for attr in attrs:
+    if attr.attributeType == typ:
+      return some(attr.value)
+  return none(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, userOpt: Option[seq[byte]] = none(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](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[seq[byte]] =
+  if ta.family != AddressFamily.IPv4 and ta.family != AddressFamily.IPv6:
+    return none(seq[byte])
+  let sm =
+    try:
+      StunMessage.decode(msg)
+    except CatchableError as exc:
+      return none(seq[byte])
+
+  if sm.msgType != BindingRequest:
+    return none(seq[byte])
+
+  var res = StunMessage(msgType: BindingResponse,
+                        transactionId: sm.transactionId)
+
+  var unknownAttr: seq[uint16]
+  for attr in sm.attributes:
+    let typ = attr.attributeType
+    if typ.isRequired() and typ notin StunAttributeEnum:
+      unknownAttr.add(typ)
+  if unknownAttr.len() > 0:
+    res.attributes.add(ErrorCode.encode(ECUnknownAttribute))
+    res.attributes.add(UnknownAttribute.encode(unknownAttr))
+    return some(res.encode(sm.attributes.getAttribute(AttrUsername.uint16)))
+
+  res.attributes.add(XorMappedAddress.encode(ta, sm.transactionId))
+  return some(res.encode(sm.attributes.getAttribute(AttrUsername.uint16)))
+
+proc new*(T: typedesc[Stun]): T =
+  result = T()