diff --git a/Lib/ssl.py b/Lib/ssl.py
index 1f3a31a..b54a684 100644
--- a/Lib/ssl.py
+++ b/Lib/ssl.py
@@ -116,6 +116,7 @@ except ImportError:
from _ssl import HAS_SNI, HAS_ECDH, HAS_NPN, HAS_ALPN, HAS_TLSv1_3
+from _ssl import _DEFAULT_CIPHERS
from _ssl import _OPENSSL_API_VERSION
@@ -174,48 +175,7 @@ else:
CHANNEL_BINDING_TYPES = []
-# Disable weak or insecure ciphers by default
-# (OpenSSL's default setting is 'DEFAULT:!aNULL:!eNULL')
-# Enable a better set of ciphers by default
-# This list has been explicitly chosen to:
-# * TLS 1.3 ChaCha20 and AES-GCM cipher suites
-# * Prefer cipher suites that offer perfect forward secrecy (DHE/ECDHE)
-# * Prefer ECDHE over DHE for better performance
-# * Prefer AEAD over CBC for better performance and security
-# * Prefer AES-GCM over ChaCha20 because most platforms have AES-NI
-# (ChaCha20 needs OpenSSL 1.1.0 or patched 1.0.2)
-# * Prefer any AES-GCM and ChaCha20 over any AES-CBC for better
-# performance and security
-# * Then Use HIGH cipher suites as a fallback
-# * Disable NULL authentication, NULL encryption, 3DES and MD5 MACs
-# for security reasons
-_DEFAULT_CIPHERS = (
- 'TLS13-AES-256-GCM-SHA384:TLS13-CHACHA20-POLY1305-SHA256:'
- 'TLS13-AES-128-GCM-SHA256:'
- 'ECDH+AESGCM:ECDH+CHACHA20:DH+AESGCM:DH+CHACHA20:ECDH+AES256:DH+AES256:'
- 'ECDH+AES128:DH+AES:ECDH+HIGH:DH+HIGH:RSA+AESGCM:RSA+AES:RSA+HIGH:'
- '!aNULL:!eNULL:!MD5:!3DES'
- )
-
-# Restricted and more secure ciphers for the server side
-# This list has been explicitly chosen to:
-# * TLS 1.3 ChaCha20 and AES-GCM cipher suites
-# * Prefer cipher suites that offer perfect forward secrecy (DHE/ECDHE)
-# * Prefer ECDHE over DHE for better performance
-# * Prefer AEAD over CBC for better performance and security
-# * Prefer AES-GCM over ChaCha20 because most platforms have AES-NI
-# * Prefer any AES-GCM and ChaCha20 over any AES-CBC for better
-# performance and security
-# * Then Use HIGH cipher suites as a fallback
-# * Disable NULL authentication, NULL encryption, MD5 MACs, DSS, RC4, and
-# 3DES for security reasons
-_RESTRICTED_SERVER_CIPHERS = (
- 'TLS13-AES-256-GCM-SHA384:TLS13-CHACHA20-POLY1305-SHA256:'
- 'TLS13-AES-128-GCM-SHA256:'
- 'ECDH+AESGCM:ECDH+CHACHA20:DH+AESGCM:DH+CHACHA20:ECDH+AES256:DH+AES256:'
- 'ECDH+AES128:DH+AES:ECDH+HIGH:DH+HIGH:RSA+AESGCM:RSA+AES:RSA+HIGH:'
- '!aNULL:!eNULL:!MD5:!DSS:!RC4:!3DES'
-)
+_RESTRICTED_SERVER_CIPHERS = _DEFAULT_CIPHERS
class CertificateError(ValueError):
@@ -389,8 +349,6 @@ class SSLContext(_SSLContext):
def __new__(cls, protocol=PROTOCOL_TLS, *args, **kwargs):
self = _SSLContext.__new__(cls, protocol)
- if protocol != _SSLv2_IF_EXISTS:
- self.set_ciphers(_DEFAULT_CIPHERS)
return self
def __init__(self, protocol=PROTOCOL_TLS):
@@ -505,8 +463,6 @@ def create_default_context(purpose=Purpose.SERVER_AUTH, *, cafile=None,
# verify certs and host name in client mode
context.verify_mode = CERT_REQUIRED
context.check_hostname = True
- elif purpose == Purpose.CLIENT_AUTH:
- context.set_ciphers(_RESTRICTED_SERVER_CIPHERS)
if cafile or capath or cadata:
context.load_verify_locations(cafile, capath, cadata)
diff --git a/Lib/test/test_ssl.py b/Lib/test/test_ssl.py
index 54644e1..799100c 100644
--- a/Lib/test/test_ssl.py
+++ b/Lib/test/test_ssl.py
@@ -18,6 +18,7 @@ import asyncore
import weakref
import platform
import functools
+import sysconfig
try:
import ctypes
except ImportError:
@@ -36,7 +37,7 @@ PROTOCOLS = sorted(ssl._PROTOCOL_NAMES)
HOST = support.HOST
IS_LIBRESSL = ssl.OPENSSL_VERSION.startswith('LibreSSL')
IS_OPENSSL_1_1 = not IS_LIBRESSL and ssl.OPENSSL_VERSION_INFO >= (1, 1, 0)
-
+PY_SSL_DEFAULT_CIPHERS = sysconfig.get_config_var('PY_SSL_DEFAULT_CIPHERS')
def data_file(*name):
return os.path.join(os.path.dirname(__file__), *name)
@@ -889,6 +890,19 @@ class ContextTests(unittest.TestCase):
with self.assertRaisesRegex(ssl.SSLError, "No cipher can be selected"):
ctx.set_ciphers("^$:,;?*'dorothyx")
+ @unittest.skipUnless(PY_SSL_DEFAULT_CIPHERS == 1,
+ "Test applies only to Python default ciphers")
+ def test_python_ciphers(self):
+ ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
+ ciphers = ctx.get_ciphers()
+ for suite in ciphers:
+ name = suite['name']
+ self.assertNotIn("PSK", name)
+ self.assertNotIn("SRP", name)
+ self.assertNotIn("MD5", name)
+ self.assertNotIn("RC4", name)
+ self.assertNotIn("3DES", name)
+
@unittest.skipIf(ssl.OPENSSL_VERSION_INFO < (1, 0, 2, 0, 0), 'OpenSSL too old')
def test_get_ciphers(self):
ctx = ssl.SSLContext(ssl.PROTOCOL_TLSv1)
diff --git a/Modules/_ssl.c b/Modules/_ssl.c
index df8c6a7..e23a569 100644
--- a/Modules/_ssl.c
+++ b/Modules/_ssl.c
@@ -206,6 +206,31 @@ SSL_SESSION_get_ticket_lifetime_hint(const SSL_SESSION *s)
#endif /* OpenSSL < 1.1.0 or LibreSSL */
+/* Default cipher suites */
+#ifndef PY_SSL_DEFAULT_CIPHERS
+#define PY_SSL_DEFAULT_CIPHERS 1
+#endif
+
+#if PY_SSL_DEFAULT_CIPHERS == 0
+ #ifndef PY_SSL_DEFAULT_CIPHER_STRING
+ #error "Py_SSL_DEFAULT_CIPHERS 0 needs Py_SSL_DEFAULT_CIPHER_STRING"
+ #endif
+#elif PY_SSL_DEFAULT_CIPHERS == 1
+/* Python custom selection of sensible ciper suites
+ * DEFAULT: OpenSSL's default cipher list. Since 1.0.2 the list is in sensible order.
+ * !aNULL:!eNULL: really no NULL ciphers
+ * !MD5:!3DES:!DES:!RC4:!IDEA:!SEED: no weak or broken algorithms on old OpenSSL versions.
+ * !aDSS: no authentication with discrete logarithm DSA algorithm
+ * !SRP:!PSK: no secure remote password or pre-shared key authentication
+ */
+ #define PY_SSL_DEFAULT_CIPHER_STRING "DEFAULT:!aNULL:!eNULL:!MD5:!3DES:!DES:!RC4:!IDEA:!SEED:!aDSS:!SRP:!PSK"
+#elif PY_SSL_DEFAULT_CIPHERS == 2
+/* Ignored in SSLContext constructor, only used to as _ssl.DEFAULT_CIPHER_STRING */
+ #define PY_SSL_DEFAULT_CIPHER_STRING SSL_DEFAULT_CIPHER_LIST
+#else
+ #error "Unsupported PY_SSL_DEFAULT_CIPHERS"
+#endif
+
enum py_ssl_error {
/* these mirror ssl.h */
@@ -2739,7 +2764,12 @@ _ssl__SSLContext_impl(PyTypeObject *type, int proto_version)
/* A bare minimum cipher list without completely broken cipher suites.
* It's far from perfect but gives users a better head start. */
if (proto_version != PY_SSL_VERSION_SSL2) {
- result = SSL_CTX_set_cipher_list(ctx, "HIGH:!aNULL:!eNULL:!MD5");
+#if PY_SSL_DEFAULT_CIPHERS == 2
+ /* stick to OpenSSL's default settings */
+ result = 1;
+#else
+ result = SSL_CTX_set_cipher_list(ctx, PY_SSL_DEFAULT_CIPHER_STRING);
+#endif
} else {
/* SSLv2 needs MD5 */
result = SSL_CTX_set_cipher_list(ctx, "HIGH:!aNULL:!eNULL");
@@ -5279,6 +5309,9 @@ PyInit__ssl(void)
(PyObject *)&PySSLSession_Type) != 0)
return NULL;
+ PyModule_AddStringConstant(m, "_DEFAULT_CIPHERS",
+ PY_SSL_DEFAULT_CIPHER_STRING);
+
PyModule_AddIntConstant(m, "SSL_ERROR_ZERO_RETURN",
PY_SSL_ERROR_ZERO_RETURN);
PyModule_AddIntConstant(m, "SSL_ERROR_WANT_READ",
diff --git a/configure.ac b/configure.ac
index 7ea62f8..4b42393 100644
--- a/configure.ac
+++ b/configure.ac
@@ -5555,6 +5555,42 @@ if test "$have_getrandom" = yes; then
[Define to 1 if the getrandom() function is available])
fi
+# ssl module default cipher suite string
+AH_TEMPLATE(PY_SSL_DEFAULT_CIPHERS,
+ [Default cipher suites list for ssl module.
+ 1: Python's preferred selection, 2: leave OpenSSL defaults untouched, 0: custom string])
+AH_TEMPLATE(PY_SSL_DEFAULT_CIPHER_STRING,
+ [Cipher suite string for PY_SSL_DEFAULT_CIPHERS=0]
+)
+AC_MSG_CHECKING(for --with-ssl-default-suites)
+AC_ARG_WITH(ssl-default-suites,
+ AS_HELP_STRING([--with-ssl-default-suites=@<:@python|openssl|STRING@:>@],
+ [Override default cipher suites string,
+ python: use Python's preferred selection (default),
+ openssl: leave OpenSSL's defaults untouched,
+ STRING: use a custom string,
+ PROTOCOL_SSLv2 ignores the setting]),
+[
+AC_MSG_RESULT($withval)
+case "$withval" in
+ python)
+ AC_DEFINE(PY_SSL_DEFAULT_CIPHERS, 1)
+ ;;
+ openssl)
+ AC_DEFINE(PY_SSL_DEFAULT_CIPHERS, 2)
+ ;;
+ *)
+ AC_DEFINE(PY_SSL_DEFAULT_CIPHERS, 0)
+ AC_DEFINE_UNQUOTED(PY_SSL_DEFAULT_CIPHER_STRING, "$withval")
+ ;;
+esac
+],
+[
+AC_MSG_RESULT(python)
+AC_DEFINE(PY_SSL_DEFAULT_CIPHERS, 1)
+])
+
+
# generate output files
AC_CONFIG_FILES(Makefile.pre Modules/Setup.config Misc/python.pc Misc/python-config.sh)
AC_CONFIG_FILES([Modules/ld_so_aix], [chmod +x Modules/ld_so_aix])