(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

@@ -289,6 +289,9 @@ Constants
 
    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

@@ -62,8 +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 _SSLContext, SSLError
 from _ssl import CERT_NONE, CERT_OPTIONAL, CERT_REQUIRED
-from _ssl import (PROTOCOL_SSLv2, PROTOCOL_SSLv3, PROTOCOL_SSLv23,
-                  PROTOCOL_TLSv1)
 from _ssl import OP_ALL, OP_NO_SSLv2, OP_NO_SSLv3, OP_NO_TLSv1
 from _ssl import RAND_status, RAND_egd, RAND_add
 from _ssl import (
@@ -78,6 +76,18 @@ from _ssl import (
     SSL_ERROR_INVALID_ERROR_CODE,
     )
 from _ssl import HAS_SNI
+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
@@ -552,13 +562,4 @@ 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

@@ -21,9 +21,11 @@ import functools
 ssl = support.import_module("ssl")
 
 PROTOCOLS = [
-    ssl.PROTOCOL_SSLv2, ssl.PROTOCOL_SSLv3,
+    ssl.PROTOCOL_SSLv3,
     ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_TLSv1
 ]
+if hasattr(ssl, 'PROTOCOL_SSLv2'):
+    PROTOCOLS.append(ssl.PROTOCOL_SSLv2)
 
 HOST = support.HOST
 
@@ -67,6 +69,7 @@ def no_sslv2_implies_sslv3_hello():
 
 # Issue #9415: Ubuntu hijacks their OpenSSL and forcefully disables SSLv2
 def skip_if_broken_ubuntu_ssl(func):
+    if hasattr(ssl, 'PROTOCOL_SSLv2'):
         @functools.wraps(func)
         def f(*args, **kwargs):
             try:
@@ -77,12 +80,14 @@ 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
@@ -310,6 +315,7 @@ class ContextTests(unittest.TestCase):
 
     @skip_if_broken_ubuntu_ssl
     def test_constructor(self):
+        if hasattr(ssl, 'PROTOCOL_SSLv2'):
             ctx = ssl.SSLContext(ssl.PROTOCOL_SSLv2)
         ctx = ssl.SSLContext(ssl.PROTOCOL_SSLv23)
         ctx = ssl.SSLContext(ssl.PROTOCOL_SSLv3)
@@ -1199,6 +1205,7 @@ else:
                 t.join()
 
         @skip_if_broken_ubuntu_ssl
+        @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:
@@ -1224,6 +1231,7 @@ else:
             """Connecting to an SSLv23 server with various client options"""
             if support.verbose:
                 sys.stdout.write("\n")
+            if hasattr(ssl, 'PROTOCOL_SSLv2'):
                 try:
                     try_protocol_combo(ssl.PROTOCOL_SSLv23, ssl.PROTOCOL_SSLv2, True)
                 except (ssl.SSLError, socket.error) as x:
@@ -1262,6 +1270,7 @@ 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)
@@ -1278,6 +1287,7 @@ 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

@@ -618,6 +618,8 @@ Core and Builtins
 Library
 -------
 
+- Issue #12012: ssl.PROTOCOL_SSLv2 becomes optional.
+
 - Issue #10916: mmap should not segfault when a file is mapped using 0 as length
   and a non-zero offset, and an attempt to read past the end of file is made
   (IndexError is raised instead).  Patch by Ross Lagerwall.

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
 };
@@ -1450,8 +1452,10 @@ context_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
         ctx = SSL_CTX_new(TLSv1_method());
     else if (proto_version == PY_SSL_VERSION_SSL3)
         ctx = SSL_CTX_new(SSLv3_method());
+#ifndef OPENSSL_NO_SSL2
     else if (proto_version == PY_SSL_VERSION_SSL2)
         ctx = SSL_CTX_new(SSLv2_method());
+#endif
     else if (proto_version == PY_SSL_VERSION_SSL23)
         ctx = SSL_CTX_new(SSLv23_method());
     else
@@ -2110,8 +2114,10 @@ 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",