Credv2: Added proper subject fields instead of just commonName for LP…

…S creds

The initial implementation for LPS-enabled credentials was just allowing the commonName OID instead of the full set of X.500 Distinguished Names.

This should fix #35, by reusing as much as possible the X509 layer already in Scapy. Added some test cases as well.

pysap/SAPCredv2.py

@@ -23,12 +23,16 @@
 from binascii import unhexlify
 # External imports
 from scapy.packet import Packet
+from scapy.compat import plain_str
 from scapy.asn1packet import ASN1_Packet
 from scapy.fields import (ByteField, ByteEnumField, ShortField, StrField, StrFixedLenField)
-from scapy.asn1.asn1 import ASN1_IA5_STRING, ASN1_Codecs
+from scapy.layers.x509 import (X509_RDN, X509_AttributeTypeAndValue,
+                               _attrName_mapping, _attrName_specials)
+from scapy.asn1.asn1 import (ASN1_IA5_STRING, ASN1_Codecs, ASN1_PRINTABLE_STRING,
+                             ASN1_OID)
 from scapy.asn1fields import (ASN1F_SEQUENCE, ASN1F_SEQUENCE_OF, ASN1F_BIT_STRING,
-                              ASN1F_IA5_STRING, ASN1F_INTEGER, ASN1F_SET, ASN1F_OID,
-                              ASN1F_PRINTABLE_STRING, ASN1F_UTF8_STRING, ASN1F_optional)
+                              ASN1F_IA5_STRING, ASN1F_INTEGER, ASN1F_UTF8_STRING,
+                              ASN1F_optional)
 # Import needed to initialize conf.mib
 from scapy.asn1.mib import conf  # noqa: F401
 
@@ -286,26 +290,52 @@ def derive_key(key, header, salt, username):
         return SAPCredv2_Cred_Plain(plain)
 
 
+_default_subject = [
+    X509_RDN(),
+    X509_RDN(
+        rdn=[X509_AttributeTypeAndValue(
+            type=ASN1_OID("2.5.4.10"),
+            value=ASN1_PRINTABLE_STRING("pysap"))]),
+    X509_RDN(
+        rdn=[X509_AttributeTypeAndValue(
+            type=ASN1_OID("2.5.4.3"),
+            value=ASN1_PRINTABLE_STRING("pysap Default Subject"))])
+]
+
+
 class SAPCredv2_Cred_LPS(ASN1_Packet):
     """SAP Credv2 Credential with LPS definition"""
     ASN1_codec = ASN1_Codecs.BER
     ASN1_root = ASN1F_SEQUENCE(
         ASN1F_INTEGER("version", 2),
-        ASN1F_SEQUENCE(
-            ASN1F_SET(
-                ASN1F_SEQUENCE(
-                    ASN1F_OID("oid", "2.5.4.3"),
-                    ASN1F_PRINTABLE_STRING("value", None)
-                )
-            )
-        ),
+        ASN1F_SEQUENCE_OF("subject", _default_subject, X509_RDN),
         ASN1F_UTF8_STRING("pse_path", None),
         ASN1F_BIT_STRING("cipher", None),
     )
 
+    def get_subject(self):
+        attrs = self.subject
+        attrsDict = {}
+        for attr in attrs:
+            # we assume there is only one name in each rdn ASN1_SET
+            attrsDict[attr.rdn[0].type.oidname] = plain_str(attr.rdn[0].value.val)  # noqa: E501
+        return attrsDict
+
     @property
     def common_name(self):
-        return self.value.val
+        """This reassembles the issuer construction from Scapy's X.509 Certificate class.
+        """
+        name_str = ""
+        attrsDict = self.get_subject()
+        for attrType, attrSymbol in _attrName_mapping:
+            if attrType in attrsDict:
+                name_str += "/" + attrSymbol + "="
+                name_str += attrsDict[attrType]
+        for attrType in sorted(attrsDict):
+            if attrType not in _attrName_specials:
+                name_str += "/" + attrType + "="
+                name_str += attrsDict[attrType]
+        return name_str
 
     @property
     def pse_file_path(self):

tests/sapcredv2_test.py

@@ -21,6 +21,8 @@
 import sys
 import unittest
 # External imports
+from scapy.asn1.asn1 import ASN1_PRINTABLE_STRING, ASN1_OID
+from scapy.layers.x509 import X509_RDN, X509_AttributeTypeAndValue
 # Custom imports
 from tests.utils import data_filename
 from pysap.SAPCredv2 import (SAPCredv2, SAPCredv2_Cred_Plain,
@@ -33,6 +35,13 @@ class PySAPCredV2Test(unittest.TestCase):
     decrypt_pin = "1234567890"
     cert_name = "CN=PSEOwner"
     common_name = "PSEOwner"
+    subject_str = "/CN=PSEOwner"
+    subject = [
+        X509_RDN(rdn=[
+            X509_AttributeTypeAndValue(type=ASN1_OID("2.5.4.3"),
+                                       value=ASN1_PRINTABLE_STRING(common_name))
+        ])
+    ]
     pse_path = "/secudir/pse-v2-noreq-DSA-1024-SHA1.pse"
     pse_path_win = "C:\\secudir\\pse-v2-noreq-DSA-1024-SHA1.pse"
 
@@ -139,14 +148,15 @@ def test_cred_v2_lps_on_int_aes256(self):
         self.assertEqual(len(creds), 1)
 
         cred = creds[0].cred
-        self.assertEqual(cred.common_name, self.common_name)
+        self.assertEqual(cred.common_name, self.subject_str)
+        self.assertEqual(cred.subject, self.subject)
+        self.assertEqual(cred.subject[0].rdn[0].type.val, "2.5.4.3")
+        self.assertEqual(cred.subject[0].rdn[0].value.val, self.common_name)
+
         self.assertEqual(cred.pse_file_path, self.pse_path)
         self.assertEqual(cred.lps_type, 0)
         self.assertEqual(cred.cipher_format_version, 2)
-
         self.assertEqual(cred.version.val, 2)
-        self.assertEqual(cred.oid.val, "2.5.4.3")
-        self.assertEqual(cred.value.val, self.common_name)
         self.assertEqual(cred.pse_path, self.pse_path)
 
     def test_cred_v2_lps_on_int_aes256_decrypt(self):
@@ -169,16 +179,52 @@ def test_cred_v2_lps_on_dp_aes256(self):
         self.assertEqual(len(creds), 1)
 
         cred = creds[0].cred
-        self.assertEqual(cred.common_name, self.common_name)
+        self.assertEqual(cred.common_name, self.subject_str)
+        self.assertEqual(cred.subject, self.subject)
+        self.assertEqual(cred.subject[0].rdn[0].type.val, "2.5.4.3")
+        self.assertEqual(cred.subject[0].rdn[0].value.val, self.common_name)
+
         self.assertEqual(cred.pse_file_path, self.pse_path_win)
         self.assertEqual(cred.lps_type, 1)
         self.assertEqual(cred.cipher_format_version, 2)
-
         self.assertEqual(cred.version.val, 2)
-        self.assertEqual(cred.oid.val, "2.5.4.3")
-        self.assertEqual(cred.value.val, self.common_name)
         self.assertEqual(cred.pse_path, self.pse_path_win)
 
+    def test_cred_v2_lps_on_int_aes256_composed_subject(self):
+        """Test parsing of a AES256 encrypted credential with LPS on, INT type, and
+        pointing to a PSE with a composed subject
+        """
+
+        with open(data_filename("cred_v2_lps_on_int_aes256_composed_subject"), "rb") as fd:
+            s = fd.read()
+
+        c = SAPCredv2(s)
+        creds = SAPCredv2(s).creds
+        self.assertEqual(len(creds), 1)
+
+        subject_str = "/C=AR/CN=PSEOwner"
+        subject = [
+            X509_RDN(rdn=[
+                X509_AttributeTypeAndValue(type=ASN1_OID("2.5.4.6"),
+                                           value=ASN1_PRINTABLE_STRING("AR"))]),
+            X509_RDN(rdn=[
+                X509_AttributeTypeAndValue(type=ASN1_OID("2.5.4.3"),
+                                           value=ASN1_PRINTABLE_STRING(self.common_name))]),
+        ]
+        cred = creds[0].cred
+        self.assertEqual(cred.common_name, subject_str)
+        self.assertEqual(cred.subject, subject)
+        self.assertEqual(cred.subject[0].rdn[0].type.val, "2.5.4.6")
+        self.assertEqual(cred.subject[0].rdn[0].value.val, "AR")
+        self.assertEqual(cred.subject[1].rdn[0].type.val, "2.5.4.3")
+        self.assertEqual(cred.subject[1].rdn[0].value.val, self.common_name)
+
+        self.assertEqual(cred.lps_type, 0)
+        self.assertEqual(cred.cipher_format_version, 2)
+        self.assertEqual(cred.version.val, 2)
+        self.assertEqual(cred.pse_file_path, "/home/martin/sec/test.pse")
+        self.assertEqual(cred.pse_path, "/home/martin/sec/test.pse")
+
 
 def test_suite():
     loader = unittest.TestLoader()