(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!

1 files changed, 13 insertions, 12 deletions

diff --git a/Lib/ssl.py b/Lib/ssl.py
index e7c175f063..b12b9fd1e6 100644
--- a/Lib/ssl.py
+++ b/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>')