Added DNS layers and packet test

README.md

@@ -1,4 +1,4 @@
-# Geneva
+# Geneva [![Build Status](https://travis-ci.com/Kkevsterrr/geneva.svg?branch=master)](https://travis-ci.com/Kkevsterrr/geneva) [![codecov](https://codecov.io/gh/Kkevsterrr/geneva/branch/master/graph/badge.svg)](https://codecov.io/gh/Kkevsterrr/geneva)
 
 Geneva is an artificial intelligence tool that defeats censorship by exploiting bugs in censors, such as those in China, India, and Kazakhstan. Unlike many other anti-censorship solutions which require assistance from outside the censoring regime (Tor, VPNs, etc.), Geneva runs strictly on the client.
 

actions/layer.py

@@ -4,7 +4,8 @@ import string
 import os
 import urllib.parse
 
-from scapy.all import IP, RandIP, UDP, Raw, TCP, fuzz
+from scapy.all import IP, RandIP, UDP, DNS, DNSQR, Raw, TCP, fuzz
+
 
 class Layer():
     """
@@ -179,6 +180,11 @@ class Layer():
         value = urllib.parse.unquote(value)
 
         value = value.encode('utf-8')
+        dns_payload = b"\x009ib\x81\x80\x00\x01\x00\x01\x00\x00\x00\x01\x08examples\x03com\x00\x00\x01\x00\x01\xc0\x0c\x00\x01\x00\x01\x00\x00\x01+\x00\x04\xc7\xbf2I\x00\x00)\x02\x00\x00\x00\x00\x00\x00\x00"
+        http_payload = b"GET / HTTP/1.1\r\nHost: www.example.com\r\n\r\n"
+
+        value = value.replace(b"__DNS_REQUEST__", dns_payload)
+        value = value.replace(b"__HTTP_REQUEST__", http_payload)
 
         self.layer.payload = Raw(value)
 
@@ -188,7 +194,7 @@ class Layer():
         as a field properly.
         """
         load = ''.join([random.choice(string.ascii_lowercase + string.digits) for k in range(10)])
-        return urllib.parse.quote(load)
+        return random.choice(urllib.parse.quote(load))
 
 
 class IPLayer(Layer):
@@ -592,3 +598,239 @@ class UDPLayer(Layer):
         self.generators = {
             'load' : self.gen_load,
         }
+
+
+class DNSLayer(Layer):
+    """
+    Defines an interface to access DNS header fields.
+    """
+    name = "DNS"
+    protocol = DNS
+    _fields = [
+        "id",
+        "qr",
+        "opcode",
+        "aa",
+        "tc",
+        "rd",
+        "ra",
+        "z",
+        "ad",
+        "cd",
+        "qd",
+        "rcode",
+        "qdcount",
+        "ancount",
+        "nscount",
+        "arcount"
+    ]
+    fields = _fields
+    def __init__(self, layer):
+        """
+        Initializes the DNS layer.
+        """
+        Layer.__init__(self, layer)
+
+        self.getters = {
+            "qr" : self.get_bitfield,
+            "aa" : self.get_bitfield,
+            "tc" : self.get_bitfield,
+            "rd" : self.get_bitfield,
+            "ra" : self.get_bitfield,
+            "z"  : self.get_bitfield,
+            "ad" : self.get_bitfield,
+            "cd" : self.get_bitfield
+        }
+
+        self.setters = {
+            "qr" : self.set_bitfield,
+            "aa" : self.set_bitfield,
+            "tc" : self.set_bitfield,
+            "rd" : self.set_bitfield,
+            "ra" : self.set_bitfield,
+            "z"  : self.set_bitfield,
+            "ad" : self.set_bitfield,
+            "cd" : self.set_bitfield
+        }
+
+        self.generators = {
+            "id" : self.gen_id,
+            "qr" : self.gen_bitfield,
+            "opcode" : self.gen_opcode,
+            "aa" : self.gen_bitfield,
+            "tc" : self.gen_bitfield,
+            "rd" : self.gen_bitfield,
+            "ra" : self.gen_bitfield,
+            "z"  : self.gen_bitfield,
+            "ad" : self.gen_bitfield,
+            "cd" : self.gen_bitfield,
+            "rcode" : self.gen_rcode,
+            "qdcount" : self.gen_count,
+            "ancount" : self.gen_count,
+            "nscount" : self.gen_count,
+            "arcount" : self.gen_count
+        }
+
+    def get_bitfield(self, field):
+        """"""
+        return int(getattr(self.layer, field))
+
+    def set_bitfield(self, packet, field, value):
+        """"""
+        return setattr(self.layer, field, int(value))
+
+    def gen_bitfield(self, field):
+        """"""
+        return random.choice([0,1])
+
+    def gen_id(self, field):
+        return random.randint(0, 65535)
+
+    def gen_opcode(self, field):
+        return random.randint(0, 15)
+
+    def gen_rcode(self, field):
+        return random.randint(0, 15)
+
+    def gen_count(self, field):
+        return random.randint(0, 65535)
+
+    @staticmethod
+    def dns_decompress(packet, logger):
+        """
+        Performs DNS decompression on the given scapy packet, if applicable.
+        Note that DNS compression/decompression must be done on the boundaries
+        of a label, so DNS compression does not support arbitrary offsets.
+        """
+        # If this is a TCP packet
+        if packet.haslayer("TCP"):
+            raise NotImplementedError
+
+        # Perform no action if this is not a DNS or DNSRQ packet
+        if not packet.haslayer("DNS") or not packet.haslayer("DNSQR"):
+            return packet
+
+        # Extract the query from the DNSQR layer
+        query = packet["DNSQR"].qname.decode()
+        if query[len(query) - 1] != '.':
+            query += '.'
+
+        # Split the query by label
+        labels = query.split(".")
+
+        # Collect the first and second half of the query
+        fhalf = labels[0]
+        shalf = ".".join(labels[1:])
+
+        # Build the first DNS query directly. The format of this a byte string like this:
+        # b'\x07minghui\xc0\x1a\x00\x01\x00\x01'
+        # \x07     = the length of the label in this DNSQR
+        # minghui  = the portion of the domain we will request in the first DNSQR
+        # \xc0\x1a = offset into the DNS packet where the rest of the query will be. The actual offset
+        #            here is the \x1a - DNS mandates that if compression is used, the first two bits be 11
+        #            to differentiate them from the rest. \x1A = 26, which is the length of the DNS header
+        #            plus the length of this DNSQR.
+        # \x00\x01 = type A record
+        # \x00\x01 = IN
+        length = bytes([len(fhalf)])
+        label = fhalf.encode()
+
+        # Since the domain will include an extra ".", add 1
+        # 2 * 6 is the DNS header
+        # 1 is the byte that determines the length of the label
+        # len(label) is the length of the label
+        # 2 is the offset pointer
+        # 4 - other record information (class, IN)
+        packet_offset = 2 * 6 + 1 + len(label) + 2 + 2 + 2
+
+        # The word must start with binary 11, so OR the offset with 0xC000.
+        offset = (0xc000 | packet_offset).to_bytes(2, byteorder='big')
+        request = b'\x00\x01\x00\x01'
+
+        dns_qr1 = length + label + offset + request
+
+        # Build the second DNS query directly. The format of the byte string is the same as above
+        # b'\x02ca\x00\x00\x01\x00\x01'
+        # \x02     = length of the remaining domain
+        # ca       = portion of the domain in this DNSQR
+        # \x00     = null byte to signify the end of the query
+        # \x00\x01 = type A record
+        # \x00\x01 = IN
+        # Since the second half could potentially contain many labels, this is done in a list comprehension
+        dns_qr2 = b"".join([bytes([len(tld)]) + tld.encode() for tld in shalf.split(".")]) + b"\x00\x01\x00\x01"
+
+        # Next, we must rebuild the DNS packet itself. If we try to have scapy parse either dns_qr1 or dns_qr2, they
+        # will look malformed, since neither contains a complete request. Therefore, we must build the entire
+        # DNS packet at once. First, we must remove the original DNSQR, since this contains the original request
+        del packet["DNS"].qd
+
+        # Once the DNSQR is removed, scapy automatically sets the qdcount to 0. Adjust it to 2
+        packet["DNS"].qdcount = 2
+
+        # Extract the DNS header standalone now for building
+        dns_header = bytes(packet["DNS"])
+
+        dns_packet = DNS(dns_header + dns_qr1 + dns_qr2)
+
+        del packet["DNS"]
+        packet = packet / dns_packet
+
+        # Since the size and data of the packet have changed, force scapy to recalculate the important fields
+        # in below layers, if applicable
+        if packet.haslayer("IP"):
+            del packet["IP"].chksum
+            del packet["IP"].len
+        if packet.haslayer("TCP"):
+            del packet["TCP"].chksum
+        if packet.haslayer("UDP"):
+            del packet["UDP"].chksum
+            del packet["UDP"].len
+
+        return packet
+
+
+class DNSQRLayer(Layer):
+    """
+    Defines an interface to access DNSQR header fields.
+    """
+    name = "DNSQR"
+    protocol = DNSQR
+    _fields = [
+        "qname",
+        "qtype",
+        "qclass"
+    ]
+    fields = _fields
+
+    def __init__(self, layer):
+        """
+        Initializes the DNS layer.
+        """
+        Layer.__init__(self, layer)
+        self.getters = {
+            "qname" : self.get_qname
+        }
+        self.generators = {
+            "qname" : self.gen_qname
+        }
+
+    def get_qname(self, field):
+        """
+        Returns decoded qname from packet.
+        """
+        return self.layer.qname.decode('utf-8')
+
+    def gen_qname(self, field):
+        """
+        Generates domain name.
+        """
+        return "example.com."
+
+    @classmethod
+    def name_matches(cls, name):
+        """
+        Scapy returns the name of DNSQR as _both_ DNSQR and "DNS Question Record",
+        which breaks parsing. Override the name_matches method to handle that case
+        here.
+        """
+        return name.upper() in ["DNSQR", "DNS QUESTION RECORD"]

actions/packet.py

@@ -7,7 +7,9 @@ import actions.layer
 _SUPPORTED_LAYERS = [
     actions.layer.IPLayer,
     actions.layer.TCPLayer,
-    actions.layer.UDPLayer
+    actions.layer.UDPLayer,
+    actions.layer.DNSLayer,
+    actions.layer.DNSQRLayer
 ]
 SUPPORTED_LAYERS = _SUPPORTED_LAYERS
 
@@ -64,9 +66,25 @@ class Packet():
     @staticmethod
     def _str_load(packet, protocol):
         """
-        Prints packet payload
+        Prints DNS header for now
         """
-        return str(packet[protocol].payload)
+        if packet.haslayer("DNS") and packet.haslayer("DNSQR"):
+            res = "%s:%s:%s " % (
+            packet["DNSQR"].qname.decode('utf8'),
+            str(packet["DNSQR"].qtype),
+            str(packet["DNSQR"].qclass))
+            DNS_res = ""
+            for i in range(packet["DNS"].ancount):
+                dnsrr = packet["DNS"].an[i]
+                DNS_res += " " + ':'.join([str(dnsrr.rrname.decode('utf8')),
+                               str(dnsrr.type),
+                               str(dnsrr.rclass),
+                               str(dnsrr.ttl),
+                               str(dnsrr.rdlen),
+                               str(dnsrr.rdata)])
+            return "%s %s" % (res, DNS_res)
+        else:
+            return str(packet[protocol].payload)
 
     def __bytes__(self):
         """
@@ -238,3 +256,77 @@ class Packet():
                 return layer
 
         return None
+
+    @staticmethod
+    def reset_restrictions():
+        """
+        Removes layer and field restrictions.
+        """
+        global SUPPORTED_LAYERS, _SUPPORTED_LAYERS
+
+        SUPPORTED_LAYERS = _SUPPORTED_LAYERS
+        for layer in SUPPORTED_LAYERS:
+            layer.reset_restrictions()
+
+    @staticmethod
+    def restrict_fields(logger, filter_protocols, filter_fields, disable_fields):
+        """
+        Validates input arguments. Used by evolve.py to restrict the scope
+        of this evolution.
+        """
+        global SUPPORTED_LAYERS
+
+        if not disable_fields:
+            disable_fields = []
+
+        # First, apply a field whitelist if it was requested
+        valid = []
+        if filter_fields:
+            for layer in SUPPORTED_LAYERS:
+                new_fields = []
+                for field in filter_fields:
+                    if field in layer.fields:
+                        new_fields.append(field)
+                        valid.append(field)
+                layer.fields = new_fields
+
+            if valid and logger:
+                logger.info("Strategies will only be allowed to use fields: %s" % ", ".join(list(set(valid))))
+            elif logger:
+                logger.error("None of the given fields exist in the packet headers of given protocols.")
+
+        # Apply a field blacklist if it was requested
+        for field in disable_fields:
+            for layer in SUPPORTED_LAYERS:
+                layer.fields = [f for f in layer.fields if f not in disable_fields]
+
+        if disable_fields and logger:
+            logger.info("Strategies will not be allowed to use fields %s" % ", ".join(disable_fields))
+
+        allowed_layers = []
+        # Finally, filter protocols
+        for protocol in filter_protocols:
+            allowed_layer = Packet.get_supported_protocol(protocol)
+            if not allowed_layer:
+                if logger:
+                    logger.error("%s not a supported protocol." % protocol)
+                continue
+
+            # Only keep the layer allowed if it contains allowed fields
+            if allowed_layer.fields:
+                allowed_layers.append(allowed_layer)
+
+        assert allowed_layers, "Cannot evolve with no available packet layers!"
+
+        SUPPORTED_LAYERS = allowed_layers
+
+        if logger and allowed_layers:
+            logger.info("Strategies will only be allowed to use protocols: %s" % ", ".join([l.name for l in allowed_layers]))
+
+    def dns_decompress(self, logger):
+        """
+        Performs DNS decompression, if applicable. Returns a new packet.
+        """
+        self.packet = actions.layer.DNSLayer.dns_decompress(self.packet, logger)
+        self.layers = self.setup_layers()
+        return self

tests/test_packet.py

@@ -0,0 +1,544 @@
+import logging
+import pytest
+
+import actions.packet
+import actions.layer
+
+from scapy.all import IP, TCP, UDP, DNS, DNSQR, Raw, DNSRR
+
+logger = logging.getLogger("test")
+
+
+def test_parse_layers():
+    """
+    Tests layer parsing.
+    """
+    pkt = IP()/TCP()/Raw("")
+    packet = actions.packet.Packet(pkt)
+    layers = list(packet.read_layers())
+    assert layers[0].name == "IP"
+    assert layers[1].name == "TCP"
+
+    layers_dict = packet.setup_layers()
+    assert layers_dict["IP"]
+    assert layers_dict["TCP"]
+
+
+def test_get_random():
+    """
+    Tests get random
+    """
+
+    tcplayer = actions.layer.TCPLayer(TCP())
+    field, value = tcplayer.get_random()
+    assert field in actions.layer.TCPLayer.fields
+
+
+def test_gen_random():
+    """
+    Tests gen random
+    """
+    for i in range(0, 2000):
+        layer, field, value = actions.packet.Packet().gen_random()
+        assert layer in [DNS, TCP, UDP, IP, DNSQR]
+
+
+def test_dnsqr():
+    """
+    Tests DNSQR.
+    """
+    pkt = UDP()/DNS(ancount=1)/DNSQR()
+    pkt.show()
+    packet = actions.packet.Packet(pkt)
+    packet.show()
+    assert len(packet.layers) == 3
+    assert "UDP" in packet.layers
+    assert "DNS" in packet.layers
+    assert "DNSQR" in packet.layers
+    pkt = IP()/UDP()/DNS()/DNSQR()
+    packet = actions.packet.Packet(pkt)
+    assert str(packet)
+
+
+def test_load():
+    """
+    Tests loads.
+    """
+    tcp = actions.layer.TCPLayer(TCP())
+    assert tcp.gen("load")
+    pkt = IP()/"datadata"
+    p = actions.packet.Packet(pkt)
+    assert p.get("IP", "load") == "datadata"
+    p2 = actions.packet.Packet(IP(bytes(p)))
+    assert p2.get("IP", "load") == "datadata"
+    p2.set("IP", "load", "data2")
+    # Check p is unchanged
+    assert p.get("IP", "load") == "datadata"
+    assert p2.get("IP", "load") == "data2"
+    p2.show2()
+    # Check that we can dump
+    assert p2.show2(dump=True)
+    # Check that we can dump
+    assert p2.show(dump=True)
+    assert p2.get("IP", "chksum") == None
+
+    pkt = IP()/TCP()/"datadata"
+    p = actions.packet.Packet(pkt)
+    assert p.get("TCP", "load") == "datadata"
+    p2 = actions.packet.Packet(IP(bytes(p)))
+    assert p2.get("TCP", "load") == "datadata"
+    p2.set("TCP", "load", "data2")
+    # Check p is unchanged
+    assert p.get("TCP", "load") == "datadata"
+    assert p2.get("TCP", "load") == "data2"
+    p2.show2()
+    assert p2.get("IP", "chksum") == None
+
+
+def test_parse_load(log_level):
+    """
+    Tests load parsing.
+    """
+    pkt = actions.packet.Packet(IP()/TCP()/"TYPE A\r\n")
+    print("Parsed: %s" % pkt.get("TCP", "load"))
+
+    strat = actions.utils.parse("[TCP:load:TYPE%20A%0D%0A]-drop-| \/", logger)
+    results = strat.act_on_packet(pkt, logger)
+    assert not results
+
+    value = pkt.gen("TCP", "load") + " " + pkt.gen("TCP", "load")
+    pkt.set("TCP", "load", value)
+    assert " " not in pkt.get("TCP", "load"), "%s contained a space!" % pkt.get("TCP", "load")
+
+
+def test_dns():
+    """
+    Tests DNS layer.
+    """
+    dns = actions.layer.DNSLayer(DNS())
+    print(dns.gen("id"))
+    assert dns.gen("id")
+
+    p = actions.packet.Packet(DNS(id=0xabcd))
+    p2 = actions.packet.Packet(DNS(bytes(p)))
+    assert p.get("DNS", "id") == 0xabcd
+    assert p2.get("DNS", "id") == 0xabcd
+
+    p2.set("DNS", "id", 0x4321)
+    assert p.get("DNS", "id") == 0xabcd # Check p is unchanged
+    assert p2.get("DNS", "id") == 0x4321
+
+    dns = actions.packet.Packet(DNS(aa=1))
+    assert dns.get("DNS", "aa") == 1
+    aa = dns.gen("DNS", "aa")
+    assert aa == 0 or aa == 1
+    assert dns.get("DNS", "aa") == 1 # Original value unchanged
+
+    dns = actions.packet.Packet(DNS(opcode=15))
+    assert dns.get("DNS", "opcode") == 15
+    opcode = dns.gen("DNS", "opcode")
+    assert opcode >= 0 and opcode <= 15
+    assert dns.get("DNS", "opcode") == 15 # Original value unchanged
+
+    dns.set("DNS", "opcode", 3)
+    assert dns.get("DNS", "opcode") == 3
+
+    dns = actions.packet.Packet(DNS(qr=0))
+    assert dns.get("DNS", "qr") == 0
+    qr = dns.gen("DNS", "qr")
+    assert qr == 0 or qr == 1
+    assert dns.get("DNS", "qr") == 0 # Original value unchanged
+
+    dns.set("DNS", "qr", 1)
+    assert dns.get("DNS", "qr") == 1
+
+    dns = actions.packet.Packet(DNS(arcount=0xAABB))
+    assert dns.get("DNS", "arcount") == 0xAABB
+    arcount = dns.gen("DNS", "arcount")
+    assert arcount >= 0 and arcount <= 0xffff
+    assert dns.get("DNS", "arcount") == 0xAABB # Original value unchanged
+
+    dns.set("DNS", "arcount", 65432)
+    assert dns.get("DNS", "arcount") == 65432
+
+    dns = actions.layer.DNSLayer(DNS()/DNSQR(qname="example.com"))
+    assert isinstance(dns.get_next_layer(), DNSQR)
+    print(dns.gen("id"))
+    assert dns.gen("id")
+
+    p = actions.packet.Packet(DNS(id=0xabcd))
+    p2 = actions.packet.Packet(DNS(bytes(p)))
+    assert p.get("DNS", "id") == 0xabcd
+    assert p2.get("DNS", "id") == 0xabcd
+
+
+def test_read_layers():
+    """
+    Tests the ability to read each layer
+    """
+    packet = IP() / UDP() / TCP() / DNS() / DNSQR(qname="example.com") / DNSQR(qname="example2.com") / DNSQR(qname="example3.com")
+    packet_geneva = actions.packet.Packet(packet)
+    packet_geneva.setup_layers()
+
+    i = 0
+    for layer in packet_geneva.read_layers():
+        if i == 0:
+            assert isinstance(layer, actions.layer.IPLayer)
+        elif i == 1:
+            assert isinstance(layer, actions.layer.UDPLayer)
+        elif i == 2:
+            assert isinstance(layer, actions.layer.TCPLayer)
+        elif i == 3:
+            assert isinstance(layer, actions.layer.DNSLayer)
+        elif i == 4:
+            assert isinstance(layer, actions.layer.DNSQRLayer)
+            assert layer.layer.qname == b"example.com"
+        elif i == 5:
+            assert isinstance(layer, actions.layer.DNSQRLayer)
+            assert layer.layer.qname == b"example2.com"
+        elif i == 6:
+            assert isinstance(layer, actions.layer.DNSQRLayer)
+            assert layer.layer.qname == b"example3.com"
+        i += 1
+
+def test_multi_opts():
+    """
+    Tests various option getting/setting.
+    """
+    pkt = IP()/TCP(options=[('MSS', 1460), ('SAckOK', b''), ('Timestamp', (4154603075, 0)), ('NOP', None), ('WScale', 7)])
+    packet = actions.packet.Packet(pkt)
+    assert packet.get("TCP", "options-sackok") == ''
+    assert packet.get("TCP", "options-mss") == 1460
+    assert packet.get("TCP", "options-timestamp") == 4154603075
+    assert packet.get("TCP", "options-wscale") == 7
+    packet.set("TCP", "options-timestamp", 400000000)
+    assert packet.get("TCP", "options-sackok") == ''
+    assert packet.get("TCP", "options-mss") == 1460
+    assert packet.get("TCP", "options-timestamp") == 400000000
+    assert packet.get("TCP", "options-wscale") == 7
+    pkt = IP()/TCP(options=[('SAckOK', b''), ('Timestamp', (4154603075, 0)), ('NOP', None), ('WScale', 7)])
+    packet = actions.packet.Packet(pkt)
+    # If the option isn't present, it will be returned as an empty string
+    assert packet.get("TCP", "options-mss") == ''
+    packet.set("TCP", "options-mss", "")
+    assert packet.get("TCP", "options-mss") == 0
+
+
+def test_options_eol():
+    """
+    Tests options-eol.
+    """
+    pkt = TCP(options=[("EOL", None)])
+    p = actions.packet.Packet(pkt)
+    assert p.get("TCP", "options-eol") == ""
+    p2 = actions.packet.Packet(TCP(bytes(p)))
+    assert p2.get("TCP", "options-eol") == ""
+    p = actions.packet.Packet(IP()/TCP(options=[]))
+    assert p.get("TCP", "options-eol") == ""
+    p.set("TCP", "options-eol", "")
+    p.show()
+    assert len(p["TCP"].options) == 1
+    assert any(k == "EOL" for k, v in p["TCP"].options)
+    value = p.gen("TCP", "options-eol")
+    assert value == "", "eol cannot store data"
+    p.set("TCP", "options-eol", value)
+    p2 = TCP(bytes(p))
+    assert any(k == "EOL" for k, v in p2["TCP"].options)
+
+
+def test_options_mss():
+    """
+    Tests options-eol.
+    """
+    pkt = TCP(options=[("MSS", 1440)])
+    p = actions.packet.Packet(pkt)
+    assert p.get("TCP", "options-mss") == 1440
+    p2 = actions.packet.Packet(TCP(bytes(p)))
+    assert p2.get("TCP", "options-mss") == 1440
+    p = actions.packet.Packet(TCP(options=[]))
+    assert p.get("TCP", "options-mss") == ""
+    p.set("TCP", "options-mss", 2880)
+    p.show()
+    assert len(p["TCP"].options) == 1
+    assert any(k == "MSS" for k, v in p["TCP"].options)
+    value = p.gen("TCP", "options-mss")
+    p.set("TCP", "options-mss", value)
+    p2 = TCP(bytes(p))
+    assert any(k == "MSS" for k, v in p2["TCP"].options)
+
+
+def check_get(protocol, field, value):
+    """
+    Checks if the get method worked for this protocol, field, and value.
+    """
+    pkt = protocol()
+    setattr(pkt, field, value)
+    packet = actions.packet.Packet(pkt)
+    assert packet.get(protocol.__name__, field) == value
+
+
+def get_test_configs():
+    """
+    Generates test configurations for the getters.
+    """
+    return [
+        (IP, 'version', 4),
+        (IP, 'version', 6),
+        (IP, 'version', 0),
+        (IP, 'ihl', 0),
+        (IP, 'tos', 0),
+        (IP, 'len', 50),
+        (IP, 'len', 6),
+        (IP, 'flags', 'MF'),
+        (IP, 'flags', 'DF'),
+        (IP, 'flags', 'MF+DF'),
+        (IP, 'ttl', 25),
+        (IP, 'proto', 4),
+        (IP, 'chksum', 0x4444),
+        (IP, 'src', '127.0.0.1'),
+        (IP, 'dst', '127.0.0.1'),
+        (TCP, 'sport', 12345),
+        (TCP, 'dport', 55555),
+        (TCP, 'seq', 123123123),
+        (TCP, 'ack', 181818181),
+        (TCP, 'dataofs', 5),
+        (TCP, 'dataofs', 0),
+        (TCP, 'dataofs', 15),
+        (TCP, 'reserved', 0),
+        (TCP, 'window', 100),
+        (TCP, 'chksum', 0x4444),
+        (TCP, 'urgptr', 1),
+
+        (DNS, 'id', 0xabcd),
+        (DNS, 'qr', 1),
+        (DNS, 'opcode', 9),
+        (DNS, 'aa', 0),
+        (DNS, 'tc', 1),
+        (DNS, 'rd', 0),
+        (DNS, 'ra', 1),
+        (DNS, 'z', 0),
+        (DNS, 'ad', 1),
+        (DNS, 'cd', 0),
+        (DNS, 'qdcount', 0x1234),
+        (DNS, 'ancount', 12345),
+        (DNS, 'nscount', 49870),
+        (DNS, 'arcount', 0xABCD),
+
+        (DNSQR, 'qname', 'example.com.'),
+        (DNSQR, 'qtype', 1),
+        (DNSQR, 'qclass', 0),
+    ]
+
+
+def get_custom_configs():
+    """
+    Generates test configurations that can use the custom getters.
+    """
+    return [
+        (IP, 'flags', ''),
+        (TCP, 'options-eol', ''),
+        (TCP, 'options-nop', ''),
+        (TCP, 'options-mss', 0),
+        (TCP, 'options-mss', 1440),
+        (TCP, 'options-mss', 5000),
+        (TCP, 'options-wscale', 20),
+        (TCP, 'options-sackok', ''),
+        (TCP, 'options-sack', ''),
+        (TCP, 'options-timestamp', 12345678),
+        (TCP, 'options-altchksum', 0x44),
+        (TCP, 'options-altchksumopt', ''),
+        (TCP, 'options-uto', 1),
+        #(TCP, 'options-md5header', 'deadc0ffee')
+    ]
+
+
+@pytest.mark.parametrize("config", get_test_configs(),
+    ids=['%s-%s-%s' % (proto.__name__, field, str(val)) for proto, field, val in get_test_configs()])
+def test_get(config):
+    """
+    Tests value retrieval.
+    """
+    proto, field, val = config
+    check_get(proto, field, val)
+
+
+def check_set_get(protocol, field, value):
+    """
+    Checks if the get method worked for this protocol, field, and value.
+    """
+    pkt = actions.packet.Packet(protocol())
+    pkt.set(protocol.__name__, field, value)
+    assert pkt.get(protocol.__name__, field) == value
+    # Rebuild the packet to confirm the type survived
+    pkt2 = actions.packet.Packet(protocol(bytes(pkt)))
+    assert pkt2.get(protocol.__name__, field) == value, "Value %s for header %s didn't survive packet parsing." % (value, field)
+
+
+@pytest.mark.parametrize("config", get_test_configs() + get_custom_configs(),
+    ids=['%s-%s-%s' % (proto.__name__, field, str(val)) for proto, field, val in get_test_configs() + get_custom_configs()])
+def test_set_get(config):
+    """
+    Tests value retrieval.
+    """
+    proto, field, value = config
+    check_set_get(proto, field, value)
+
+
+def check_gen_set_get(protocol, field):
+    """
+    Checks if the get method worked for this protocol, field, and value.
+    """
+    pkt = actions.packet.Packet(protocol())
+    new_value = pkt.gen(protocol.__name__, field)
+    pkt.set(protocol.__name__, field, new_value)
+    assert pkt.get(protocol.__name__, field) == new_value
+    # Rebuild the packet to confirm the type survived
+    pkt2 = actions.packet.Packet(protocol(bytes(pkt)))
+    assert pkt2.get(protocol.__name__, field) == new_value
+
+
+@pytest.mark.parametrize("config", get_test_configs() + get_custom_configs(),
+    ids=['%s-%s' % (proto.__name__, field) for proto, field, _ in get_test_configs() + get_custom_configs()])
+def test_gen_set_get(config):
+    """
+    Tests value retrieval.
+    """
+    # Test each generator 50 times to hit a range of values
+    for i in range(0, 50):
+        proto, field, _ = config
+        check_gen_set_get(proto, field)
+
+
+def test_custom_get():
+    """
+    Tests value retrieval for custom getters.
+    """
+    pkt = IP()/TCP()/Raw(load="AAAA")
+    tcp = actions.packet.Packet(pkt)
+    assert tcp.get("TCP", "load") == "AAAA"
+
+
+def test_restrict_fields():
+    """
+    Tests packet field restriction.
+    """
+    actions.packet.SUPPORTED_LAYERS = [
+        actions.layer.IPLayer,
+        actions.layer.TCPLayer,
+        actions.layer.UDPLayer
+    ]
+    tcpfields = actions.layer.TCPLayer.fields
+    udpfields = actions.layer.UDPLayer.fields
+    ipfields = actions.layer.IPLayer.fields
+
+    actions.packet.Packet.restrict_fields(logger, ["TCP", "UDP"], [], [])
+    assert len(actions.packet.SUPPORTED_LAYERS) == 2
+    assert actions.layer.TCPLayer in actions.packet.SUPPORTED_LAYERS
+    assert actions.layer.UDPLayer in actions.packet.SUPPORTED_LAYERS
+    assert not actions.layer.IPLayer in actions.packet.SUPPORTED_LAYERS
+
+    pkt = IP()/TCP()
+    packet = actions.packet.Packet(pkt)
+    assert "TCP" in packet.layers
+    assert not "IP" in packet.layers
+    assert len(packet.layers) == 1
+
+    for i in range(0, 2000):
+        layer, proto, field = actions.packet.Packet().gen_random()
+        assert layer in [TCP, UDP]
+
+    # Check we can't retrieve any IP fields
+    for field in actions.layer.IPLayer.fields:
+        with pytest.raises(AssertionError):
+            packet.get("IP", field)
+
+    # Check we can get all the TCP fields
+    for field in actions.layer.TCPLayer.fields:
+        packet.get("TCP", field)
+
+    actions.packet.Packet.restrict_fields(logger, ["TCP", "UDP"], ["flags"], [])
+    packet = actions.packet.Packet(pkt)
+    assert len(actions.packet.SUPPORTED_LAYERS) == 1
+    assert actions.layer.TCPLayer in actions.packet.SUPPORTED_LAYERS
+    assert not actions.layer.UDPLayer in actions.packet.SUPPORTED_LAYERS
+    assert not actions.layer.IPLayer in actions.packet.SUPPORTED_LAYERS
+    assert actions.layer.TCPLayer.fields == ["flags"]
+    assert not actions.layer.UDPLayer.fields
+
+    # Check we can't retrieve any IP fields
+    for field in actions.layer.IPLayer.fields:
+        with pytest.raises(AssertionError):
+            packet.get("IP", field)
+
+    # Check we can get all the TCP fields
+    for field in tcpfields:
+        if field == "flags":
+            packet.get("TCP", field)
+        else:
+            with pytest.raises(AssertionError):
+                packet.get("TCP", field)
+
+    for i in range(0, 2000):
+        layer, field, value = actions.packet.Packet().gen_random()
+        assert layer == TCP
+        assert field == "flags"
+
+    actions.packet.Packet.reset_restrictions()
+    actions.packet.SUPPORTED_LAYERS = [
+        actions.layer.IPLayer,
+        actions.layer.TCPLayer,
+        actions.layer.UDPLayer
+    ]
+    actions.packet.Packet.restrict_fields(logger, ["TCP", "IP"], [], ["sport", "dport", "seq", "src"])
+    packet = actions.packet.Packet(pkt)
+    packet = packet.copy()
+    assert packet.has_supported_layers()
+    assert len(actions.packet.SUPPORTED_LAYERS) == 2
+    assert actions.layer.TCPLayer in actions.packet.SUPPORTED_LAYERS
+    assert not actions.layer.UDPLayer in actions.packet.SUPPORTED_LAYERS
+    assert actions.layer.IPLayer in actions.packet.SUPPORTED_LAYERS
+    assert set(actions.layer.TCPLayer.fields) == set([f for f in tcpfields if f not in ["sport", "dport", "seq"]])
+    assert set(actions.layer.IPLayer.fields) == set([f for f in ipfields if f not in ["src"]])
+
+    # Check we can't retrieve any IP fields
+    for field in actions.layer.IPLayer.fields:
+        if field == "src":
+            with pytest.raises(AssertionError):
+                packet.get("IP", field)
+        else:
+            packet.get("IP", field)
+
+    # Check we can get all the TCP fields
+    for field in tcpfields:
+        if field in ["sport", "dport", "seq"]:
+            with pytest.raises(AssertionError):
+                packet.get("TCP", field)
+        else:
+            packet.get("TCP", field)
+
+    for i in range(0, 2000):
+        layer, field, value = actions.packet.Packet().gen_random()
+        assert layer in [TCP, IP]
+        assert field not in ["sport", "dport", "seq", "src"]
+
+    actions.packet.Packet.reset_restrictions()
+    actions.packet.SUPPORTED_LAYERS = [
+        actions.layer.IPLayer,
+        actions.layer.TCPLayer,
+        actions.layer.UDPLayer
+    ]
+
+    actions.packet.Packet.restrict_fields(logger, ["IP", "UDP", "DNS"], [], ["version"])
+    packet = actions.packet.Packet(pkt)
+    proto, field, value = packet.get_random()
+    assert proto.__name__ in ["IP", "UDP"]
+    assert len(actions.packet.SUPPORTED_LAYERS) == 2
+    assert not actions.layer.TCPLayer in actions.packet.SUPPORTED_LAYERS
+    assert actions.layer.UDPLayer in actions.packet.SUPPORTED_LAYERS
+    assert actions.layer.IPLayer in actions.packet.SUPPORTED_LAYERS
+    assert set(actions.layer.IPLayer.fields) == set([f for f in ipfields if f not in ["version"]])
+    assert set(actions.layer.UDPLayer.fields) == set(udpfields)
+
+    actions.packet.Packet.reset_restrictions()
+    for layer in actions.packet.SUPPORTED_LAYERS:
+        assert layer.fields, '%s has no fields - reset failed!' % str(layer)