Issue #12012: ssl.PROTOCOL_SSLv2 becomes optional

OpenSSL is now compiled with OPENSSL_NO_SSL2 defined (without the SSLv2
protocol) on Debian: fix the ssl module on Debian Testing and Debian Sid.

Optimize also ssl.get_protocol_name(): speed does matter!

Doc/library/ssl.rst

@@ -219,6 +219,9 @@ Functions, Constants, and Exceptions
 
    Selects SSL version 2 as the channel encryption protocol.
 
+   This protocol is not available if OpenSSL is compiled with OPENSSL_NO_SSL2
+   flag.
+
    .. warning::
 
       SSL version 2 is insecure.  Its use is highly discouraged.

Lib/ssl.py

@@ -60,8 +60,6 @@ import _ssl             # if we can't import it, let the error propagate
 
 from _ssl import SSLError
 from _ssl import CERT_NONE, CERT_OPTIONAL, CERT_REQUIRED
-from _ssl import (PROTOCOL_SSLv2, PROTOCOL_SSLv3, PROTOCOL_SSLv23,
-                  PROTOCOL_TLSv1)
 from _ssl import RAND_status, RAND_egd, RAND_add
 from _ssl import (
     SSL_ERROR_ZERO_RETURN,
@@ -74,6 +72,18 @@ from _ssl import (
     SSL_ERROR_EOF,
     SSL_ERROR_INVALID_ERROR_CODE,
     )
+from _ssl import PROTOCOL_SSLv3, PROTOCOL_SSLv23, PROTOCOL_TLSv1
+_PROTOCOL_NAMES = {
+    PROTOCOL_TLSv1: "TLSv1",
+    PROTOCOL_SSLv23: "SSLv23",
+    PROTOCOL_SSLv3: "SSLv3",
+}
+try:
+    from _ssl import PROTOCOL_SSLv2
+except ImportError:
+    pass
+else:
+    _PROTOCOL_NAMES[PROTOCOL_SSLv2] = "SSLv2"
 
 from socket import getnameinfo as _getnameinfo
 from socket import error as socket_error
@@ -427,13 +437,4 @@ def get_server_certificate(addr, ssl_version=PROTOCOL_SSLv3, ca_certs=None):
     return DER_cert_to_PEM_cert(dercert)
 
 def get_protocol_name(protocol_code):
-    if protocol_code == PROTOCOL_TLSv1:
-        return "TLSv1"
-    elif protocol_code == PROTOCOL_SSLv23:
-        return "SSLv23"
-    elif protocol_code == PROTOCOL_SSLv2:
-        return "SSLv2"
-    elif protocol_code == PROTOCOL_SSLv3:
-        return "SSLv3"
-    else:
-        return "<unknown>"
+    return _PROTOCOL_NAMES.get(protocol_code, '<unknown>')

Lib/test/test_ssl.py

@@ -40,7 +40,7 @@ def handle_error(prefix):
 class BasicTests(unittest.TestCase):
 
     def test_constants(self):
-        ssl.PROTOCOL_SSLv2
+        #ssl.PROTOCOL_SSLv2
         ssl.PROTOCOL_SSLv23
         ssl.PROTOCOL_SSLv3
         ssl.PROTOCOL_TLSv1
@@ -838,6 +838,7 @@ else:
             finally:
                 t.join()
 
+        @unittest.skipUnless(hasattr(ssl, 'PROTOCOL_SSLv2'), "need SSLv2")
         def test_protocol_sslv2(self):
             """Connecting to an SSLv2 server with various client options"""
             if support.verbose:
@@ -857,14 +858,15 @@ else:
                 sys.stdout.write("\ntest_protocol_sslv23 disabled, "
                                  "as it fails on OpenSSL 1.0.0+")
             return
-            try:
-                try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv2, True)
-            except (ssl.SSLError, socket.error) as x:
-                # this fails on some older versions of OpenSSL (0.9.7l, for instance)
-                if support.verbose:
-                    sys.stdout.write(
-                        " SSL2 client to SSL23 server test unexpectedly failed:\n %s\n"
-                        % str(x))
+            if hasattr(ssl, 'PROTOCOL_SSLv2'):
+                try:
+                    try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv2, True)
+                except (ssl.SSLError, socket.error) as x:
+                    # this fails on some older versions of OpenSSL (0.9.7l, for instance)
+                    if support.verbose:
+                        sys.stdout.write(
+                            " SSL2 client to SSL23 server test unexpectedly failed:\n %s\n"
+                            % str(x))
             try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv3, True)
             try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv23, True)
             try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_TLSv1, True)
@@ -886,7 +888,8 @@ else:
             try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv3, True)
             try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv3, True, ssl.CERT_OPTIONAL)
             try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv3, True, ssl.CERT_REQUIRED)
-            try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv2, False)
+            if hasattr(ssl, 'PROTOCOL_SSLv2'):
+                try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv2, False)
             try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_SSLv23, False)
             try_protocol_combo(ssl.PROTOCOL_SSLv3, ssl.PROTOCOL_TLSv1, False)
 
@@ -899,7 +902,8 @@ else:
             try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_TLSv1, True)
             try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_TLSv1, True, ssl.CERT_OPTIONAL)
             try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_TLSv1, True, ssl.CERT_REQUIRED)
-            try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_SSLv2, False)
+            if hasattr(ssl, 'PROTOCOL_SSLv2'):
+                try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_SSLv2, False)
             try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_SSLv3, False)
             try_protocol_combo(ssl.PROTOCOL_TLSv1, ssl.PROTOCOL_SSLv23, False)
 

Misc/NEWS

@@ -69,6 +69,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #12012: ssl.PROTOCOL_SSLv2 becomes optional.
+
 - Issue #11164: Stop trying to use _xmlplus in the xml module.
 
 - Issue #11927: SMTP_SSL now uses port 465 by default as documented.  Patch

Modules/_ssl.c

@@ -63,8 +63,10 @@ enum py_ssl_cert_requirements {
 };
 
 enum py_ssl_version {
+#ifndef OPENSSL_NO_SSL2
     PY_SSL_VERSION_SSL2,
-    PY_SSL_VERSION_SSL3,
+#endif
+    PY_SSL_VERSION_SSL3=1,
     PY_SSL_VERSION_SSL23,
     PY_SSL_VERSION_TLS1
 };
@@ -306,8 +308,10 @@ newPySSLObject(PySocketSockObject *Sock, char *key_file, char *cert_file,
         self->ctx = SSL_CTX_new(TLSv1_method()); /* Set up context */
     else if (proto_version == PY_SSL_VERSION_SSL3)
         self->ctx = SSL_CTX_new(SSLv3_method()); /* Set up context */
+#ifndef OPENSSL_NO_SSL2
     else if (proto_version == PY_SSL_VERSION_SSL2)
         self->ctx = SSL_CTX_new(SSLv2_method()); /* Set up context */
+#endif
     else if (proto_version == PY_SSL_VERSION_SSL23)
         self->ctx = SSL_CTX_new(SSLv23_method()); /* Set up context */
     PySSL_END_ALLOW_THREADS
@@ -1787,8 +1791,10 @@ PyInit__ssl(void)
                             PY_SSL_CERT_REQUIRED);
 
     /* protocol versions */
+#ifndef OPENSSL_NO_SSL2
     PyModule_AddIntConstant(m, "PROTOCOL_SSLv2",
                             PY_SSL_VERSION_SSL2);
+#endif
     PyModule_AddIntConstant(m, "PROTOCOL_SSLv3",
                             PY_SSL_VERSION_SSL3);
     PyModule_AddIntConstant(m, "PROTOCOL_SSLv23",