Extended Sequence Numbers support in ESP

Author: phuhavan

scapy/layers/ipsec.py

@@ -674,16 +674,17 @@ def sign(self, pkt, key, esn_en=False, esn=0):
         mac = self.new_mac(key)
 
         if pkt.haslayer(ESP):
-            mac.update(raw(pkt[ESP]))
+            mac.update(bytes(pkt[ESP]))
+            if esn_en:
+                # RFC4303 sect 2.2.1
+                mac.update(struct.pack('!L', esn))
             pkt[ESP].data += mac.finalize()[:self.icv_size]
 
         elif pkt.haslayer(AH):
-            clone = zero_mutable_fields(pkt.copy(), sending=True)
+            mac.update(bytes(zero_mutable_fields(pkt.copy(), sending=True)))
             if esn_en:
-                temp = raw(clone) + struct.pack('!L', esn)
-            else:
-                temp = raw(clone)
-            mac.update(temp)
+                # RFC4302 sect 2.5.1
+                mac.update(struct.pack('!L', esn))
             pkt[AH].icv = mac.finalize()[:self.icv_size]
 
         return pkt
@@ -712,7 +713,10 @@ def verify(self, pkt, key, esn_en=False, esn=0):
             pkt_icv = pkt.data[len(pkt.data) - self.icv_size:]
             clone = pkt.copy()
             clone.data = clone.data[:len(clone.data) - self.icv_size]
-            temp = raw(clone)
+            mac.update(bytes(clone))
+            if esn_en:
+                # RFC4303 sect 2.2.1
+                mac.update(struct.pack('!L', esn))
 
         elif pkt.haslayer(AH):
             if len(pkt[AH].icv) != self.icv_size:
@@ -721,12 +725,11 @@ def verify(self, pkt, key, esn_en=False, esn=0):
                 pkt[AH].icv = pkt[AH].icv[:self.icv_size]
             pkt_icv = pkt[AH].icv
             clone = zero_mutable_fields(pkt.copy(), sending=False)
+            mac.update(bytes(clone))
             if esn_en:
-                temp = raw(clone) + struct.pack('!L', esn)
-            else:
-                temp = raw(clone)
+                # RFC4302 sect 2.5.1
+                mac.update(struct.pack('!L', esn))
 
-        mac.update(temp)
         computed_icv = mac.finalize()[:self.icv_size]
 
         # XXX: Cannot use mac.verify because the ICV can be truncated
@@ -1033,7 +1036,10 @@ def _encrypt_esp(self, pkt, seq_num=None, iv=None, esn_en=None, esn=None):
                                       esn_en=esn_en or self.esn_en,
                                       esn=esn or self.esn)
 
-        self.auth_algo.sign(esp, self.auth_key)
+        self.auth_algo.sign(esp,
+                            self.auth_key,
+                            esn_en=esn_en or self.esn_en,
+                            esn=esn or self.esn)
 
         if self.nat_t_header:
             nat_t_header = self.nat_t_header.copy()
@@ -1144,7 +1150,9 @@ def _decrypt_esp(self, pkt, verify=True, esn_en=None, esn=None):
 
         if verify:
             self.check_spi(pkt)
-            self.auth_algo.verify(encrypted, self.auth_key)
+            self.auth_algo.verify(encrypted, self.auth_key,
+                                  esn_en=esn_en or self.esn_en,
+                                  esn=esn or self.esn)
 
         esp = self.crypt_algo.decrypt(self, encrypted, self.crypt_key,
                                       self.crypt_icv_size or

test/scapy/layers/ipsec.uts

@@ -1506,6 +1506,31 @@ try:
 except IPSecIntegrityError as err:
     err
 
+#######################################
+= IPv4 / ESP - Transport - AES-CBC - HMAC-SHA2-256-128 -- ESN
+
+p = IP(src='1.1.1.1', dst='2.2.2.2')
+p /= TCP(sport=45012, dport=80)
+p /= Raw('hello world')
+p = IP(raw(p))
+p
+
+enc_key = bytes.fromhex("85ee354b4675a9c5d16e3d6f4118043b")
+auth_key = bytes.fromhex("6f79bf94da7dde3c86009934d9258f1b3fc2f5382aca9c9cb8e216eed235f34c")
+
+sa = SecurityAssociation(ESP, spi=0xcf54ccdf, crypt_algo='AES-CBC',
+                         crypt_key=enc_key,
+                         auth_algo='SHA2-256-128', auth_key=auth_key,
+                         esn_en=True, esn=68)
+e = sa.encrypt(p, iv=bytes.fromhex("11223344112233441122334411223344"))
+
+
+assert bytes(e) == bytes.fromhex("4500006c000100004032745a0101010102020202cf54ccdf0000000111223344112233441122334411223344f5bda519c9ae64f283f0fc18a8d253eca8b34c2120c8958a97ec9d8e67756da2523fce9b5541c57fddf090afc2bfd97e8703203953f853eb61482e4c1384d4c8")
+
+* integrity verification should pass
+d = sa.decrypt(e)
+d
+
 #######################################
 = IPv4 / ESP - Transport - AES-GCM - NULL