[inet6] recognize unknown router advertisement options (#4233)

scapy/layers/inet6.py

@@ -1737,18 +1737,41 @@ class _ICMPv6NDGuessPayload:
 
     def guess_payload_class(self, p):
         if len(p) > 1:
-            return icmp6ndoptscls.get(orb(p[0]), Raw)  # s/Raw/ICMPv6NDOptUnknown/g ?  # noqa: E501
+            return icmp6ndoptscls.get(orb(p[0]), ICMPv6NDOptUnknown)
 
 
 # Beginning of ICMPv6 Neighbor Discovery Options.
 
+class ICMPv6NDOptDataField(StrLenField):
+    __slots__ = ["strip_zeros"]
+
+    def __init__(self, name, default, strip_zeros=False, **kwargs):
+        super().__init__(name, default, **kwargs)
+        self.strip_zeros = strip_zeros
+
+    def i2len(self, pkt, x):
+        return len(self.i2m(pkt, x))
+
+    def i2m(self, pkt, x):
+        r = (len(x) + 2) % 8
+        if r:
+            x += b"\x00" * (8 - r)
+        return x
+
+    def m2i(self, pkt, x):
+        if self.strip_zeros:
+            x = x.rstrip(b"\x00")
+        return x
+
+
 class ICMPv6NDOptUnknown(_ICMPv6NDGuessPayload, Packet):
     name = "ICMPv6 Neighbor Discovery Option - Scapy Unimplemented"
     fields_desc = [ByteField("type", None),
                    FieldLenField("len", None, length_of="data", fmt="B",
-                                 adjust=lambda pkt, x: x + 2),
-                   StrLenField("data", "",
-                               length_from=lambda pkt: pkt.len - 2)]
+                                 adjust=lambda pkt, x: (2 + x) // 8),
+                   ICMPv6NDOptDataField("data", "", strip_zeros=False,
+                                        length_from=lambda pkt:
+                                        8 * max(pkt.len, 1) - 2)]
 
 # NOTE: len includes type and len field. Expressed in unit of 8 bytes
 # TODO: Revoir le coup du ETHER_ANY
@@ -2059,34 +2082,14 @@ def mysummary(self):
         return self.sprintf("%name% ") + ", ".join(self.searchlist)
 
 
-# URI MUST be padded with NUL (0x00) to make the total option length
-# (including the Type and Length fields) a multiple of 8 bytes.
-# https://www.rfc-editor.org/rfc/rfc8910.html#name-the-captive-portal-ipv6-ra-
-class CaptivePortalURI(StrLenField):
-    def i2len(self, pkt, x):
-        return len(self.i2m(pkt, x))
-
-    def i2m(self, pkt, x):
-        r = (len(x) + 2) % 8
-        if r:
-            x += b"\x00" * (8 - r)
-        return x
-
-    def m2i(self, pkt, x):
-        return x.rstrip(b"\x00")
-
-
 class ICMPv6NDOptCaptivePortal(_ICMPv6NDGuessPayload, Packet):  # RFC 8910
     name = "ICMPv6 Neighbor Discovery Option - Captive-Portal Option"
     fields_desc = [ByteField("type", 37),
                    FieldLenField("len", None, length_of="URI", fmt="B",
                                  adjust=lambda pkt, x: (2 + x) // 8),
-
-                   # Zero length is nonsensical but it's treated as 1 here to
-                   # let the dissector skip bogus options more or less gracefully
-                   CaptivePortalURI("URI", "",
-                                    length_from=lambda pkt: 8 * max(pkt.len, 1) - 2)
-                   ]
+                   ICMPv6NDOptDataField("URI", "", strip_zeros=True,
+                                        length_from=lambda pkt:
+                                        8 * max(pkt.len, 1) - 2)]
 
     def mysummary(self):
         return self.sprintf("%name% %URI%")

test/scapy/layers/inet6.uts

@@ -780,18 +780,40 @@ b.answers(a)
 + ICMPv6NDOptUnknown Class Test
 
 = ICMPv6NDOptUnknown - Basic Instantiation
-raw(ICMPv6NDOptUnknown()) == b'\x00\x02'
+b = b'\x00\x01\x00\x00\x00\x00\x00\x00'
+
+raw(ICMPv6NDOptUnknown()) == b
 
 = ICMPv6NDOptUnknown - Instantiation with specific values
-raw(ICMPv6NDOptUnknown(len=4, data="somestring")) == b'\x00\x04somestring'
+raw(ICMPv6NDOptUnknown(data="somestring")) == b'\x00\x02somestring\x00\x00\x00\x00'
 
 = ICMPv6NDOptUnknown - Basic Dissection
-a=ICMPv6NDOptUnknown(b'\x00\x02')
-a.type == 0 and a.len == 2
+b = b'\x00\x01\x00\x00\x00\x00\x00\x00'
+
+p = ICMPv6NDOptUnknown(b)
+p.type == 0 and p.len == 1 and p.data == b'\x00' * 6
+
+p = ICMPv6NDOptUnknown(b + b'\x00')
+assert Raw in p and raw(p[Raw]) == b'\x00'
+
+p = ICMPv6NDOptUnknown(b + b'\x00\x00')
+assert raw(p[ICMPv6NDOptUnknown:2]) == b'\x00\x00'
 
 = ICMPv6NDOptUnknown - Dissection with specific values 
-a=ICMPv6NDOptUnknown(b'\x00\x04somerawing')
-a.type == 0 and a.len==4 and a.data == b"so" and isinstance(a.payload, Raw) and a.payload.load == b"merawing"
+p = ICMPv6NDOptUnknown(b'\x00\x01string')
+assert p.type == 0 and p.len == 1 and p.data == b'string'
+
+p = ICMPv6NDOptUnknown(b'\x00\x04somestring')
+assert p.type == 0 and p.len == 4 and p.data == b'somestring'
+
+= ICMPv6NDOptUnknown - Instantiation/Dissection with unknown option in the middle
+b = b'\x01\x01\x00\x00\x00\x00\x00\x00\x00\x02somestring\x00\x00\x00\x00%\x01\x00\x00\x00\x00\x00\x00'
+
+p = ICMPv6NDOptSrcLLAddr()/ICMPv6NDOptUnknown(data='somestring')/ICMPv6NDOptCaptivePortal()
+assert raw(p) == b
+
+p = ICMPv6NDOptSrcLLAddr(b)[ICMPv6NDOptUnknown]
+assert p.type == 0 and p.len == 2 and p.data == b'somestring\x00\x00\x00\x00'
 
 
 ############
@@ -1231,8 +1253,10 @@ p = ICMPv6NDOptCaptivePortal(b"\x25\x03https://example.com\x00\x00\x00")
 p.type == 37 and p.len == 3 and p.URI == b"https://example.com"
 
 = ICMPv6NDOptCaptivePortal - Dissection with zero length
-p = ICMPv6NDOptCaptivePortal(b"\x25\x00abcdefgh")
-p.type == 37 and p.len == 0 and p.URI == b"abcdef" and Raw in p and len(p[Raw]) == 2
+p = ICMPv6NDOptCaptivePortal(b"\x25\x00abcdef\x00\x01")
+p.type == 37 and p.len == 0 and p.URI == b"abcdef"
+pay = p.payload
+assert pay.type == 0 and pay.len == 1 and pay.data == b""
 
 = ICMPv6NDOptCaptivePortal - Summary Output
 ICMPv6NDOptCaptivePortal(URI="https://example.com").mysummary() == "ICMPv6 Neighbor Discovery Option - Captive-Portal Option b'https://example.com'"
@@ -1269,7 +1293,7 @@ p = ICMPv6NDOptPREF64(raw(p))
 assert p.type == 38 and p.len == 2 and p.scaledlifetime == 225 and p.plc == 1 and p.prefix == '2003:da8:1::'
 
 p = ICMPv6NDOptPREF64(raw(p) + b'\x00\x00\x00\x00')
-assert Raw in p and len(p[Raw]) == 4
+assert ICMPv6NDOptUnknown in p and len(p[ICMPv6NDOptUnknown]) == 4
 
 = ICMPv6NDOptPREF64 - Summary Output
 ICMPv6NDOptPREF64(prefix='12:34:56::', plc='/32').mysummary() == "ICMPv6 Neighbor Discovery Option - PREF64 Option 12:34:56::/32"