packet lib: don't crash with truncated dhcp packet

Signed-off-by: FUJITA Tomonori <fujita.tomonori@lab.ntt.co.jp>

2 files changed, 12 insertions, 1 deletions

diff --git a/ryu/lib/packet/dhcp.py b/ryu/lib/packet/dhcp.py
index c8fb16a9..5320079a 100644
--- a/ryu/lib/packet/dhcp.py
+++ b/ryu/lib/packet/dhcp.py
@@ -174,7 +174,7 @@ class dhcp(packet_base.PacketBase):
         self.options = options
 
     @classmethod
-    def parser(cls, buf):
+    def _parser(cls, buf):
         (op, htype, hlen) = struct.unpack_from(cls._HLEN_UNPACK_STR, buf)
         buf = buf[cls._HLEN_UNPACK_LEN:]
         unpack_str = cls._DHCP_UNPACK_STR % (hlen,
@@ -195,6 +195,13 @@ class dhcp(packet_base.PacketBase):
                     addrconv.ipv4.bin_to_text(giaddr), sname, boot_file),
                 None, buf[length:])
 
+    @classmethod
+    def parser(cls, buf):
+        try:
+            return cls._parser(buf)
+        except:
+            return None, None, buf
+
     def serialize(self, payload, prev):
         seri_opt = self.options.serialize()
         pack_str = '%s%ds' % (self._DHCP_PACK_STR,
diff --git a/ryu/tests/unit/packet/test_dhcp.py b/ryu/tests/unit/packet/test_dhcp.py
index 2581e7e1..44a10c50 100644
--- a/ryu/tests/unit/packet/test_dhcp.py
+++ b/ryu/tests/unit/packet/test_dhcp.py
@@ -128,6 +128,10 @@ class Test_dhcp_offer(unittest.TestCase):
         eq_(self.boot_file.ljust(128, '\x00'), res.boot_file)
         eq_(str(self.options), str(res.options))
 
+    def test_parser_corrupted(self):
+        buf = self.buf[:128 - (14 + 20 + 8)]
+        _res = self.dh.parser(buf)
+
     def test_serialize(self):
         data = bytearray()
         prev = None