probe with extensions length smaller than actual data

test to see if implementation verifies the length of extensions array

prober.py

@@ -72,6 +72,9 @@
     CompressOnly(),
     CompressOnly12(),
     CompressOnly12PFS(),
+    ExtensionsUnderflow(),
+    ExtensionsUnderflow12(),
+    ExtensionsUnderflow12PFS(),
     DoubleClientHello(),
     DoubleClientHello12(),
     DoubleClientHello12PFS(),

probes.py

@@ -311,6 +311,35 @@ class InvalidExtLength12PFS(InvalidExtLength, InvalidSessionID12PFS):
     pass
 
 
+class ExtensionsUnderflow(InvalidSessionID):
+    '''Send hello with data length lower than stated size'''
+
+    def make_hello_payload(self, version, cipher_suites):
+        ciphers = struct.pack('>H{0}H'.format(len(cipher_suites)),
+                              len(cipher_suites) * 2, *cipher_suites)
+        hello = (struct.pack('>H32sB',
+                             version,
+                             b'01234567890123456789012345678901',
+                             0) +
+                 ciphers + b'\x01\x00'
+                 b'\x00\x01'  # extensions length, just one byte
+                 b'\xff\x01'  # extension ID - secure renego indication
+                 b'\x00\x01'  # secure renego indication ext length
+                 b'\x00')  # valid payload for extension
+
+        return hello
+
+
+class ExtensionsUnderflow12(ExtensionsUnderflow, InvalidSessionID12):
+    '''As in ExtensionsUnderflow but in TLSv1.2 hello'''
+    pass
+
+
+class ExtensionsUnderflow12PFS(ExtensionsUnderflow, InvalidSessionID12PFS):
+    '''As in ExtensionsUnderflow but in PFS TLSv1.2 hello'''
+    pass
+
+
 class EmptyCompression(InvalidSessionID):
     '''Send hello with no compression methods'''
 

tests/test_probes.py

@@ -430,6 +430,73 @@ def test_test(self):
                           b"\x00"])
 
 
+class TestExtensionsUnderflow(unittest.TestCase):
+    def test_test(self):
+        probe = ExtensionsUnderflow()
+        sock = MockSock()
+
+        probe.test(sock)
+
+        self.assertEqual(sock.sent_data,
+                         [b'\x16\x03\x01\x00@'
+                          b'\x01\x00\x00<'
+                          b'\x03\x01' +
+                          RANDOM_STR +
+                          b'\x00'
+                          b'\x00\x0e' +
+                          DEFAULT_CIPHERS_STR +
+                          b'\x01\x00'
+                          b'\x00\x01'
+                          b'\xff\x01'
+                          b'\x00\x01'
+                          b'\x00'])
+
+
+class TestExtensionsUnderflow12(unittest.TestCase):
+    def test_test(self):
+        probe = ExtensionsUnderflow12()
+        sock = MockSock()
+
+        probe.test(sock)
+
+        self.assertEqual(sock.sent_data,
+                         [b'\x16\x03\x01\x00X'
+                          b'\x01\x00\x00T'
+                          b'\x03\x03' +
+                          RANDOM_STR +
+                          b'\x00'
+                          b'\x00&' +
+                          DEFAULT_12_CIPHERS_STR +
+                          b'\x01\x00'
+                          b'\x00\x01'
+                          b'\xff\x01'
+                          b'\x00\x01'
+                          b'\x00'])
+
+
+class TestExtensionsUnderflow12PFS(unittest.TestCase):
+    def test_test(self):
+        probe = ExtensionsUnderflow12PFS()
+        sock = MockSock()
+
+        probe.test(sock)
+
+        self.maxDiff = None
+        self.assertEqual(sock.sent_data,
+                         [b"\x16\x03\x01\x00\x90"
+                          b"\x01\x00\x00\x8c"
+                          b"\x03\x03" +
+                          RANDOM_STR +
+                          b"\x00"
+                          b"\x00^" +
+                          DEFAULT_PFS_CIPHERS_STR +
+                          b"\x01\x00"
+                          b'\x00\x01'
+                          b'\xff\x01'
+                          b'\x00\x01'
+                          b'\x00'])
+
+
 class TestEmptyCompression(unittest.TestCase):
     def test_test(self):
         probe = EmptyCompression()