(Merge 3.1) 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

@@ -237,6 +237,9 @@ 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

@@ -62,7 +62,6 @@ import _ssl             # if we can't import it, let the error propagate
 from _ssl import OPENSSL_VERSION_NUMBER, OPENSSL_VERSION_INFO, OPENSSL_VERSION
 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 +73,18 @@ from _ssl import \
      SSL_ERROR_WANT_CONNECT, \
      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 socket, _fileobject, _delegate_methods, error as socket_error
 from socket import getnameinfo as _getnameinfo
@@ -425,16 +436,7 @@ 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>')
 
 
 # a replacement for the old socket.ssl function

Lib/test/test_ssl.py

@@ -58,6 +58,7 @@ class BasicTests(unittest.TestCase):
 
 # Issue #9415: Ubuntu hijacks their OpenSSL and forcefully disables SSLv2
 def skip_if_broken_ubuntu_ssl(func):
+    if hasattr(ssl, 'PROTOCOL_SSLv2'):
         # We need to access the lower-level wrapper in order to create an
         # implicit SSL context without trying to connect or listen.
         try:
@@ -78,12 +79,14 @@ def skip_if_broken_ubuntu_ssl(func):
                     raise unittest.SkipTest("Patched Ubuntu OpenSSL breaks behaviour")
             return func(*args, **kwargs)
         return f
+    else:
+        return func
 
 
 class BasicSocketTests(unittest.TestCase):
 
     def test_constants(self):
-        ssl.PROTOCOL_SSLv2
+        #ssl.PROTOCOL_SSLv2
         ssl.PROTOCOL_SSLv23
         ssl.PROTOCOL_SSLv3
         ssl.PROTOCOL_TLSv1
@@ -1008,6 +1011,7 @@ 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)
+            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)
@@ -1020,6 +1024,7 @@ 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)
+            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

@@ -80,6 +80,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #12012: ssl.PROTOCOL_SSLv2 becomes optional.
+
 - Issue #11164: Remove obsolete allnodes test from minidom test.
 
 - Issue #11927: SMTP_SSL now uses port 465 by default as documented.  Patch

Modules/_ssl.c

@@ -62,8 +62,10 @@ 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
 };
@@ -302,8 +304,10 @@ 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
@@ -1708,8 +1712,10 @@ init_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",