From cbbd04cdc36aa4874115062297850c8b7bf4ff31 Mon Sep 17 00:00:00 2001
From: mtu <maxence.tury@ssi.gouv.fr>
Date: Thu, 4 Feb 2016 17:10:57 +0100
Subject: [PATCH] Make ASN1F_CHOICE more simple and readable
---
scapy/asn1fields.py | 43 ++++++++-----------------------------------
test/x509.uts | 2 +-
2 files changed, 9 insertions(+), 36 deletions(-)
diff --git a/scapy/asn1fields.py b/scapy/asn1fields.py
index 296ce0a7..bff04578 100644
--- a/scapy/asn1fields.py
+++ b/scapy/asn1fields.py
@@ -400,16 +400,8 @@ class ASN1F_optional(ASN1F_field):
class ASN1F_CHOICE(ASN1F_field):
"""
Multiple types are allowed: ASN1_Packet, ASN1F_field and ASN1F_PACKET(),
- e.g. you could define ASN1F_CHOICE("qualifier", None,
- X509_UserNotice,
- ASN1F_X509_CPSuri)
- or ASN1F_CHOICE("qualifier", None,
- ASN1F_PACKET("index", dflt, X509_Pkt,
- implicit_tag=0x82),
- explicit_tag=0xa1)
+ See layers/x509.py for examples.
Other ASN1F_field instances than ASN1F_PACKET instances must not be used.
- ASN1F_PACKET instances must not be mixed with other types.
- self.instantiated_choices signals whether only such instances are present.
"""
holds_packets = 1
ASN1_tag = ASN1_Class_UNIVERSAL.ANY
@@ -428,10 +420,9 @@ class ASN1F_CHOICE(ASN1F_field):
self.default = default
self.current_choice = None
self.choices = {}
- self.instantiated_choices = True
+ self.pktchoices = {}
for p in args:
if hasattr(p, "ASN1_root"): # should be ASN1_Packet
- self.instantiated_choices = False
if hasattr(p.ASN1_root, "choices"):
for k,v in p.ASN1_root.choices.items():
self.choices[k] = v # ASN1F_CHOICE recursion
@@ -439,18 +430,16 @@ class ASN1F_CHOICE(ASN1F_field):
self.choices[p.ASN1_root.network_tag] = p
elif hasattr(p, "ASN1_tag"):
if type(p) is type: # should be ASN1F_field class
- self.instantiated_choices = False
self.choices[p.ASN1_tag] = p
else: # should be ASN1F_PACKET instance
self.choices[p.network_tag] = p
+ self.pktchoices[hash(p.cls)] = (p.implicit_tag, p.explicit_tag)
else:
raise ASN1_Error("ASN1F_CHOICE: no tag found for one field")
def m2i(self, pkt, s):
"""
First we have to retrieve the appropriate choice.
Then we extract the field/packet, according to this choice.
- In case the choice depends on implicit or explicit tags,
- ASN1F_PACKET instance choices can be defined with the right tags.
"""
if len(s) == 0:
raise ASN1_Error("ASN1F_CHOICE: got empty string")
@@ -472,32 +461,16 @@ class ASN1F_CHOICE(ASN1F_field):
return choice(self.name, "").m2i(pkt, s)
else:
# choice must be an ASN1F_PACKET instance here
- c,s = choice.m2i(pkt, s)
- # dirty hack here: when c is an ASN1_Packet, its __dict__
- # is controlled so we hide tags inside overload_fields
- hcls = hash(choice.cls)
- c.overload_fields[hcls] = {}
- if hasattr(choice, "implicit_tag"):
- c.overload_fields[hcls]["imp"] = choice.implicit_tag
- else:
- c.overload_fields[hcls]["imp"] = None
- if hasattr(choice, "explicit_tag"):
- c.overload_fields[hcls]["exp"] = choice.explicit_tag
- else:
- c.overload_fields[hcls]["exp"] = None
- return c,s
+ return choice.m2i(pkt, s)
def i2m(self, pkt, x):
if x is None:
s = ""
else:
s = str(x)
- if self.instantiated_choices:
- cls = type(x)
- if hash(cls) not in x.overload_fields:
- raise ASN1_Error("ASN1F_CHOICE: could not encode object")
- tags = x.overload_fields[hash(cls)]
- s = BER_tagging_enc(s, implicit_tag=tags["imp"],
- explicit_tag=tags["exp"])
+ if hash(type(x)) in self.pktchoices.keys():
+ imp, exp = self.pktchoices[hash(type(x))]
+ s = BER_tagging_enc(s, implicit_tag=imp,
+ explicit_tag=exp)
return BER_tagging_enc(s, explicit_tag=self.explicit_tag)
def randval(self):
return RandChoice(*map(lambda x:fuzz(x()), self.choice.values()))
diff --git a/test/x509.uts b/test/x509.uts
index 3c0cb430..3505c10d 100644
--- a/test/x509.uts
+++ b/test/x509.uts
@@ -1,4 +1,4 @@
-# X.509 unit tests
+% Tests for X.509 objects
#
# Launch me with:
# sudo bash test/run_tests -t test/x509.uts -F
--
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