From 69d2399789e0fe6be26c7a4bf145f2a200ee24fd Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Fran=C3=A7ois=20De=20Keersmaeker?=
<francois.dekeersmaeker@uclouvain.be>
Date: Wed, 31 May 2023 16:59:31 +0200
Subject: [PATCH] Fix checksum and len fields update
---
src/packet/BOOTP.py | 2 +-
src/packet/CoAP.py | 2 +-
src/packet/DNS.py | 2 +-
src/packet/IGMPv3mr.py | 7 +------
src/packet/Packet.py | 34 ++++++++++++++++++++++------------
src/packet/Transport.py | 2 +-
6 files changed, 27 insertions(+), 22 deletions(-)
diff --git a/src/packet/BOOTP.py b/src/packet/BOOTP.py
index 805562b..075697b 100644
--- a/src/packet/BOOTP.py
+++ b/src/packet/BOOTP.py
@@ -91,7 +91,7 @@ class BOOTP(Packet):
self.set_dhcp_option(field, new_value) # Set new value for field
# Update checksums
- self.update_checksums()
+ self.update_fields()
# Return value: dictionary containing tweak information
return self.get_dict_log(field, old_value, new_value)
diff --git a/src/packet/CoAP.py b/src/packet/CoAP.py
index 9d79806..1d1d9e0 100644
--- a/src/packet/CoAP.py
+++ b/src/packet/CoAP.py
@@ -101,7 +101,7 @@ class CoAP(Packet):
self.layer.setfieldval("options", result["new_options"])
# Update checksums
- self.update_checksums()
+ self.update_fields()
# Return value: dictionary containing tweak information
return self.get_dict_log(field, old_value, new_value)
diff --git a/src/packet/DNS.py b/src/packet/DNS.py
index 7b2de66..6e9d750 100644
--- a/src/packet/DNS.py
+++ b/src/packet/DNS.py
@@ -110,7 +110,7 @@ class DNS(Packet):
question_record.setfieldval("qname", new_value_single)
# Update checksums
- self.update_checksums()
+ self.update_fields()
# Return value: dictionary containing tweak information
return self.get_dict_log(field, old_value, new_value)
diff --git a/src/packet/IGMPv3mr.py b/src/packet/IGMPv3mr.py
index 2015bf3..2f1cfc0 100644
--- a/src/packet/IGMPv3mr.py
+++ b/src/packet/IGMPv3mr.py
@@ -33,14 +33,9 @@ class IGMPv3mr(Packet):
new_value += new_address
group.setfieldval("maddr", new_address)
i += 1
-
- logging.info(f"Packet {self.id}: randomized all IGMPv3 group addresses.")
# Update checksums
- del self.packet.getlayer("IGMPv3").chksum
- del self.packet.getlayer("IP").len
- del self.packet.getlayer("IP").chksum
- self.packet = scapy.Ether(self.packet.build())
+ self.update_fields()
# Return value: dictionary containing tweak information
return self.get_dict_log("maddr", old_value, new_value)
diff --git a/src/packet/Packet.py b/src/packet/Packet.py
index 9c60a96..d739cff 100644
--- a/src/packet/Packet.py
+++ b/src/packet/Packet.py
@@ -194,19 +194,29 @@ class Packet:
self.packet.time = timestamp
- def update_checksums(self) -> None:
+ def update_fields(self) -> None:
"""
- Update packet checksums, if needed.
+ Update checksum and length fields on all relevant layers,
+ and rebuild packet.
"""
- if self.packet.haslayer("IP"):
- ip_layer = self.packet.getlayer("IP")
- ip_layer.delfieldval("len")
- ip_layer.delfieldval("chksum")
- transport_layer = self.packet.getlayer(2)
- if hasattr(transport_layer, "len"):
- transport_layer.delfieldval("len")
- if hasattr(transport_layer, "chksum"):
- transport_layer.delfieldval("chksum")
+ # Loop on all packet layers
+ i = 0
+ while True:
+ layer = self.packet.getlayer(i)
+ if layer is None:
+ break
+
+ # Delete checksum field
+ if hasattr(layer, "chksum") and layer.getfieldval("chksum") is not None:
+ layer.delfieldval("chksum")
+
+ # Delete length field
+ if hasattr(layer, "len") and layer.getfieldval("len") is not None:
+ layer.delfieldval("len")
+
+ i += 1
+
+ # Rebuild packet, to update deleted fields
self.rebuild()
@@ -305,7 +315,7 @@ class Packet:
self.layer.setfieldval(field, new_value)
# Update checksums
- self.update_checksums()
+ self.update_fields()
# Return value: dictionary containing tweak information
return self.get_dict_log(field, old_value, new_value)
diff --git a/src/packet/Transport.py b/src/packet/Transport.py
index 9109bac..433d82c 100644
--- a/src/packet/Transport.py
+++ b/src/packet/Transport.py
@@ -50,7 +50,7 @@ class Transport(Packet):
self.layer.setfieldval(field, new_value)
# Update checksums, if needed
- self.update_checksums()
+ self.update_fields()
# Return value: dictionary containing tweak information
return self.get_dict_log(field, old_value, new_value)
--
GitLab