Fix OpenFlow3 padding bug (#4440)

secdev · Jun 27, 2024 · 460c989 · 460c989
1 parent 2091f69
commit 460c989
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Showing 2 changed files with 8 additions and 7 deletions.
diff --git a/scapy/contrib/openflow3.py b/scapy/contrib/openflow3.py
@@ -979,10 +979,8 @@ def post_build(self, p, pay):
             zero_bytes = (8 - tmp_len % 8) % 8
             tmp_len = tmp_len + zero_bytes    # add padding length
             p = p[:2] + struct.pack("!H", tmp_len) + p[4:]
-        else:
-            zero_bytes = (8 - tmp_len % 8) % 8
-        # every message will be padded correctly
-        p += b"\x00" * zero_bytes
+            p += b"\x00" * zero_bytes
+        # message with user-defined length will not be automatically padded
         return p + pay
 
     def extract_padding(self, s):
@@ -2697,9 +2695,9 @@ def post_build(self, p, pay):
         if tmp_len is None:
             tmp_len = len(p) + len(pay)
             p = p[:2] + struct.pack("!H", tmp_len) + p[4:]
-        # every message will be padded correctly
-        zero_bytes = (8 - tmp_len % 8) % 8
-        p += b"\x00" * zero_bytes
+            zero_bytes = (8 - tmp_len % 8) % 8
+            p += b"\x00" * zero_bytes
+        # message with user-defined length will not be automatically padded
         return p + pay
 
     def extract_padding(self, s):

diff --git a/test/contrib/openflow3.uts b/test/contrib/openflow3.uts
@@ -74,6 +74,9 @@ assert len(fpti) == 16
 assert fpti.instruction_ids[0].type == 1
 assert fpti.instruction_ids[1].type == 5
 
+fpti.instruction_ids[0] = OFPITGotoTableID()
+assert bytes(fpti) == b'\x00\x00\x00\x0c\x00\x01\x00\x04\x00\x05\x00\x04\x00\x00\x00\x00'
+
 = OFPTPacketIn() containing an Ethernet frame
 ofm = OFPTPacketIn(data=Ether()/IP()/ICMP())
 p = OFPTPacketIn(raw(ofm))