From 766b99b6c9ed1c9122643ef5e7da51486dacc6af Mon Sep 17 00:00:00 2001
From: Pierre LALET <pierre.lalet@cea.fr>
Date: Tue, 6 Jan 2015 09:48:11 +0100
Subject: [PATCH] Introduce a cache mechanism to track changes in mutable field
values
This is useful when a field value content is tampered without the
value itself being changed (this can happen with values of type list
and Packet, for example).
--HG--
branch : issue-5105
---
scapy/packet.py | 51 +++++++++++++++++++++++++++++++++++++++++++++++--
1 file changed, 49 insertions(+), 2 deletions(-)
diff --git a/scapy/packet.py b/scapy/packet.py
index 01dac646..6bb4ff3e 100644
--- a/scapy/packet.py
+++ b/scapy/packet.py
@@ -49,6 +49,7 @@ class Packet(BasePacket):
show_indent=1
explicit = 0
raw_packet_cache = None
+ raw_packet_cache_fields = None
@classmethod
def from_hexcap(cls):
@@ -153,6 +154,7 @@ class Packet(BasePacket):
clone.underlayer = self.underlayer
clone.explicit = self.explicit
clone.raw_packet_cache = self.raw_packet_cache
+ clone.raw_packet_cache_fields = self.clone_raw_packet_cache_fields()
clone.post_transforms = self.post_transforms[:]
clone.__dict__["payload"] = self.payload.copy()
clone.payload.add_underlayer(clone)
@@ -194,6 +196,7 @@ class Packet(BasePacket):
self.fields[attr] = any2i(self, val)
self.explicit = 0
self.raw_packet_cache = None
+ self.raw_packet_cache_fields = None
elif attr == "payload":
self.remove_payload()
self.add_payload(val)
@@ -215,6 +218,7 @@ class Packet(BasePacket):
del(self.fields[attr])
self.explicit = 0 # in case a default value must be explicited
self.raw_packet_cache = None
+ self.raw_packet_cache_fields = None
elif self.default_fields.has_key(attr):
pass
elif attr == "payload":
@@ -295,9 +299,34 @@ class Packet(BasePacket):
return True
def __len__(self):
return len(self.__str__())
+ def clone_raw_packet_cache_fields(self):
+ if self.raw_packet_cache_fields is None:
+ return None
+ result = {}
+ for key, (value, islist,
+ holds_packets) in self.raw_packet_cache_fields.iteritems():
+ if islist:
+ if holds_packets:
+ result[key] = ([
+ p.copy() for p in value
+ ], 1, 1)
+ else:
+ # XXX Not ideal since elements themselves can be
+ # mutable
+ result[key] = (value[:], 1, 0)
+ else:
+ # if holds_packets:
+ result[key] = (value, 0, 0)
+ return result
def self_build(self, field_pos_list=None):
if self.raw_packet_cache is not None:
- return self.raw_packet_cache
+ for fname, (fval, _, _) in self.raw_packet_cache_fields.iteritems():
+ if self.getfieldval(fname) != fval:
+ self.raw_packet_cache = None
+ self.raw_packet_cache_fields = None
+ break
+ if self.raw_packet_cache is not None:
+ return self.raw_packet_cache
p=""
for f in self.fields_desc:
val = self.getfieldval(f.name)
@@ -558,9 +587,26 @@ Creates an EPS file describing a packet. If filename is not provided a temporary
flist = self.fields_desc[:]
flist.reverse()
raw = s
+ self.raw_packet_cache_fields = {}
while s and flist:
f = flist.pop()
- s,fval = f.getfield(self, s)
+ s, fval = f.getfield(self, s)
+ # We need to track fields with mutable values to discard
+ # .raw_packet_cache when needed.
+ #
+ # The values in f.raw_packet_cache_fields are three
+ # elements tuples (value, f.islist, f.holds_packets)
+ if f.islist:
+ if f.holds_packets:
+ self.raw_packet_cache_fields[f.name] = ([
+ p.copy() for p in fval
+ ], 1, 1)
+ else:
+ # XXX Not ideal since elements themselves can be
+ # mutable
+ self.raw_packet_cache_fields[f.name] = (fval[:], 1, 0)
+ elif f.holds_packets and fval is not None:
+ self.raw_packet_cache_fields[f.name] = (fval.copy(), 0, 1)
self.fields[f.name] = fval
assert(raw.endswith(s))
if s:
@@ -635,6 +681,7 @@ Creates an EPS file describing a packet. If filename is not provided a temporary
pkt.overload_fields = self.overload_fields.copy()
pkt.post_transforms = self.post_transforms
pkt.raw_packet_cache = self.raw_packet_cache
+ pkt.raw_packet_cache_fields = self.clone_raw_packet_cache_fields()
if payload is not None:
pkt.add_payload(payload)
return pkt
--
GitLab