[Python-checkins] bpo-31399: Let OpenSSL verify hostname and IP address (#3462)

Christian Heimes webhook-mailer at python.org
Sat Jan 27 09:51:41 EST 2018

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---

https://github.com/python/cpython/commit/61d478c71c5341cdc54e6bfb4ace4252852fd972
commit: 61d478c71c5341cdc54e6bfb4ace4252852fd972
branch: master
author: Christian Heimes <christian at python.org>
committer: GitHub <noreply at github.com>
date: 2018年01月27日T15:51:38+01:00
summary:
bpo-31399: Let OpenSSL verify hostname and IP address (#3462)
bpo-31399: Let OpenSSL verify hostname and IP
The ssl module now uses OpenSSL's X509_VERIFY_PARAM_set1_host() and
X509_VERIFY_PARAM_set1_ip() API to verify hostname and IP addresses.
* Remove match_hostname calls
* Check for libssl with set1_host, libssl must provide X509_VERIFY_PARAM_set1_host()
* Add documentation for OpenSSL 1.0.2 requirement
* Don't support OpenSSL special mode with a leading dot, e.g. ".example.org" matches "www.example.org". It's not standard conform.
* Add hostname_checks_common_name
Signed-off-by: Christian Heimes <christian at python.org>
files:
A Misc/NEWS.d/next/Library/2017-09-08-14-05-33.bpo-31399.FtBrrt.rst
M Doc/library/ssl.rst
M Doc/whatsnew/3.7.rst
M Lib/asyncio/sslproto.py
M Lib/http/client.py
M Lib/ssl.py
M Lib/test/test_asyncio/test_events.py
M Lib/test/test_ftplib.py
M Lib/test/test_imaplib.py
M Lib/test/test_poplib.py
M Lib/test/test_ssl.py
M Lib/test/test_urllib2_localnet.py
M Modules/_ssl.c
M PC/pyconfig.h
M setup.py
diff --git a/Doc/library/ssl.rst b/Doc/library/ssl.rst
index 4c44ffa23ac..aa1075d4b02 100644
--- a/Doc/library/ssl.rst
+++ b/Doc/library/ssl.rst
@@ -146,9 +146,10 @@ Functions, Constants, and Exceptions
 
 .. exception:: CertificateError
 
- Raised to signal an error with a certificate (such as mismatching
- hostname). Certificate errors detected by OpenSSL, though, raise
- an :exc:`SSLCertVerificationError`.
+ An alias for :exc:`SSLCertVerificationError`.
+
+ .. versionchanged:: 3.7
+ The exception is now an alias for :exc:`SSLCertVerificationError`.
 
 
 Socket creation
@@ -430,8 +431,14 @@ Certificate handling
 of the certificate, is now supported.
 
 .. versionchanged:: 3.7
+ The function is no longer used to TLS connections. Hostname matching
+ is now performed by OpenSSL.
+
 Allow wildcard when it is the leftmost and the only character
- in that segment.
+ in that segment. Partial wildcards like ``www*.example.com`` are no
+ longer supported.
+
+ .. deprecated:: 3.7
 
 .. function:: cert_time_to_seconds(cert_time)
 
@@ -850,6 +857,14 @@ Constants
 
 .. versionadded:: 3.5
 
+.. data:: HAS_NEVER_CHECK_COMMON_NAME
+
+ Whether the OpenSSL library has built-in support not checking subject
+ common name and :attr:`SSLContext.hostname_checks_common_name` is
+ writeable.
+
+ .. versionadded:: 3.7
+
 .. data:: HAS_ECDH
 
 Whether the OpenSSL library has built-in support for Elliptic Curve-based
@@ -1075,6 +1090,12 @@ SSL sockets also have the following additional methods and attributes:
 The socket timeout is no more reset each time bytes are received or sent.
 The socket timeout is now to maximum total duration of the handshake.
 
+ .. versionchanged:: 3.7
+ Hostname or IP address is matched by OpenSSL during handshake. The
+ function :func:`match_hostname` is no longer used. In case OpenSSL
+ refuses a hostname or IP address, the handshake is aborted early and
+ a TLS alert message is send to the peer.
+
 .. method:: SSLSocket.getpeercert(binary_form=False)
 
 If there is no certificate for the peer on the other end of the connection,
@@ -1730,6 +1751,17 @@ to speed up repeated connections from the same clients.
 The protocol version chosen when constructing the context. This attribute
 is read-only.
 
+.. attribute:: SSLContext.hostname_checks_common_name
+
+ Whether :attr:`~SSLContext.check_hostname` falls back to verify the cert's
+ subject common name in the absence of a subject alternative name
+ extension (default: true).
+
+ .. versionadded:: 3.7
+
+ .. note::
+ Only writeable with OpenSSL 1.1.0 or higher.
+
 .. attribute:: SSLContext.verify_flags
 
 The flags for certificate verification operations. You can set flags like
@@ -2324,6 +2356,10 @@ in this case, the :func:`match_hostname` function can be used. This common
 check is automatically performed when :attr:`SSLContext.check_hostname` is
 enabled.
 
+.. versionchanged:: 3.7
+ Hostname matchings is now performed by OpenSSL. Python no longer uses
+ :func:`match_hostname`.
+
 In server mode, if you want to authenticate your clients using the SSL layer
 (rather than using a higher-level authentication mechanism), you'll also have
 to specify :const:`CERT_REQUIRED` and similarly check the client certificate.
diff --git a/Doc/whatsnew/3.7.rst b/Doc/whatsnew/3.7.rst
index 133975a04dd..1ece6a3befd 100644
--- a/Doc/whatsnew/3.7.rst
+++ b/Doc/whatsnew/3.7.rst
@@ -568,6 +568,32 @@ can be set within the scope of a group.
 ``'^$'`` or ``(?=-)`` that matches an empty string.
 (Contributed by Serhiy Storchaka in :issue:`25054`.)
 
+ssl
+---
+
+The ssl module now uses OpenSSL's builtin API instead of
+:func:`~ssl.match_hostname` to check host name or IP address. Values
+are validated during TLS handshake. Any cert validation error including
+a failing host name match now raises :exc:`~ssl.SSLCertVerificationError` and
+aborts the handshake with a proper TLS Alert message. The new exception
+contains additional information. Host name validation can be customized
+with :attr:`~ssl.SSLContext.host_flags`.
+(Contributed by Christian Heimes in :issue:`31399`.)
+
+.. note::
+ The improved host name check requires an OpenSSL 1.0.2 or 1.1 compatible
+ libssl. OpenSSL 0.9.8 and 1.0.1 are no longer supported. LibreSSL is
+ temporarily not supported until it gains the necessary OpenSSL 1.0.2 APIs.
+
+The ssl module no longer sends IP addresses in SNI TLS extension.
+(Contributed by Christian Heimes in :issue:`32185`.)
+
+:func:`~ssl.match_hostname` no longer supports partial wildcards like
+``www*.example.org``. :attr:`~ssl.SSLContext.host_flags` has partial
+wildcard matching disabled by default.
+(Contributed by Mandeep Singh in :issue:`23033` and Christian Heimes in
+:issue:`31399`.)
+
 string
 ------
 
@@ -1120,6 +1146,12 @@ Other CPython implementation changes
 emitted in the first place), and an explicit ``error::BytesWarning``
 warnings filter added to convert them to exceptions.
 
+* CPython' :mod:`ssl` module requires OpenSSL 1.0.2 or 1.1 compatible libssl.
+ OpenSSL 1.0.1 has reached end of lifetime on 2016年12月31日 and is no longer
+ supported. LibreSSL is temporarily not supported as well. LibreSSL releases
+ up to version 2.6.4 are missing required OpenSSL 1.0.2 APIs.
+
+
 Documentation
 =============
 
diff --git a/Lib/asyncio/sslproto.py b/Lib/asyncio/sslproto.py
index 2d377c4ae39..1130bced8ae 100644
--- a/Lib/asyncio/sslproto.py
+++ b/Lib/asyncio/sslproto.py
@@ -590,12 +590,6 @@ def _on_handshake_complete(self, handshake_exc):
 raise handshake_exc
 
 peercert = sslobj.getpeercert()
- if not hasattr(self._sslcontext, 'check_hostname'):
- # Verify hostname if requested, Python 3.4+ uses check_hostname
- # and checks the hostname in do_handshake()
- if (self._server_hostname and
- self._sslcontext.verify_mode != ssl.CERT_NONE):
- ssl.match_hostname(peercert, self._server_hostname)
 except BaseException as exc:
 if self._loop.get_debug():
 if isinstance(exc, ssl.CertificateError):
diff --git a/Lib/http/client.py b/Lib/http/client.py
index 1a852cd76e4..1292db74784 100644
--- a/Lib/http/client.py
+++ b/Lib/http/client.py
@@ -1375,7 +1375,8 @@ def __init__(self, host, port=None, key_file=None, cert_file=None,
 if key_file or cert_file:
 context.load_cert_chain(cert_file, key_file)
 self._context = context
- self._check_hostname = check_hostname
+ if check_hostname is not None:
+ self._context.check_hostname = check_hostname
 
 def connect(self):
 "Connect to a host on a given (SSL) port."
@@ -1389,13 +1390,6 @@ def connect(self):
 
 self.sock = self._context.wrap_socket(self.sock,
 server_hostname=server_hostname)
- if not self._context.check_hostname and self._check_hostname:
- try:
- ssl.match_hostname(self.sock.getpeercert(), server_hostname)
- except Exception:
- self.sock.shutdown(socket.SHUT_RDWR)
- self.sock.close()
- raise
 
 __all__.append("HTTPSConnection")
 
diff --git a/Lib/ssl.py b/Lib/ssl.py
index 7c4cccf4c0c..5f972e1d3d8 100644
--- a/Lib/ssl.py
+++ b/Lib/ssl.py
@@ -148,7 +148,6 @@
 lambda name: name.startswith('CERT_'),
 source=_ssl)
 
-
 PROTOCOL_SSLv23 = _SSLMethod.PROTOCOL_SSLv23 = _SSLMethod.PROTOCOL_TLS
 _PROTOCOL_NAMES = {value: name for name, value in _SSLMethod.__members__.items()}
 
@@ -172,6 +171,8 @@
 else:
 CHANNEL_BINDING_TYPES = []
 
+HAS_NEVER_CHECK_COMMON_NAME = hasattr(_ssl, 'HOSTFLAG_NEVER_CHECK_SUBJECT')
+
 
 # Disable weak or insecure ciphers by default
 # (OpenSSL's default setting is 'DEFAULT:!aNULL:!eNULL')
@@ -216,9 +217,7 @@
 '!aNULL:!eNULL:!MD5:!DSS:!RC4:!3DES'
 )
 
-
-class CertificateError(ValueError):
- pass
+CertificateError = SSLCertVerificationError
 
 
 def _dnsname_match(dn, hostname):
@@ -473,6 +472,23 @@ def options(self):
 def options(self, value):
 super(SSLContext, SSLContext).options.__set__(self, value)
 
+ if hasattr(_ssl, 'HOSTFLAG_NEVER_CHECK_SUBJECT'):
+ @property
+ def hostname_checks_common_name(self):
+ ncs = self._host_flags & _ssl.HOSTFLAG_NEVER_CHECK_SUBJECT
+ return ncs != _ssl.HOSTFLAG_NEVER_CHECK_SUBJECT
+
+ @hostname_checks_common_name.setter
+ def hostname_checks_common_name(self, value):
+ if value:
+ self._host_flags &= ~_ssl.HOSTFLAG_NEVER_CHECK_SUBJECT
+ else:
+ self._host_flags |= _ssl.HOSTFLAG_NEVER_CHECK_SUBJECT
+ else:
+ @property
+ def hostname_checks_common_name(self):
+ return True
+
 @property
 def verify_flags(self):
 return VerifyFlags(super().verify_flags)
@@ -699,11 +715,6 @@ def pending(self):
 def do_handshake(self):
 """Start the SSL/TLS handshake."""
 self._sslobj.do_handshake()
- if self.context.check_hostname:
- if not self.server_hostname:
- raise ValueError("check_hostname needs server_hostname "
- "argument")
- match_hostname(self.getpeercert(), self.server_hostname)
 
 def unwrap(self):
 """Start the SSL shutdown handshake."""
diff --git a/Lib/test/test_asyncio/test_events.py b/Lib/test/test_asyncio/test_events.py
index e4b053681b4..cf217538a06 100644
--- a/Lib/test/test_asyncio/test_events.py
+++ b/Lib/test/test_asyncio/test_events.py
@@ -1148,11 +1148,13 @@ def test_create_server_ssl_match_failed(self):
 with test_utils.disable_logger():
 with self.assertRaisesRegex(
 ssl.CertificateError,
- "hostname '127.0.0.1' doesn't match 'localhost'"):
+ "IP address mismatch, certificate is not valid for "
+ "'127.0.0.1'"):
 self.loop.run_until_complete(f_c)
 
 # close connection
- proto.transport.close()
+ # transport is None because TLS ALERT aborted the handshake
+ self.assertIsNone(proto.transport)
 server.close()
 
 @support.skip_unless_bind_unix_socket
diff --git a/Lib/test/test_ftplib.py b/Lib/test/test_ftplib.py
index f1b0185b2bf..bb5a67f27e3 100644
--- a/Lib/test/test_ftplib.py
+++ b/Lib/test/test_ftplib.py
@@ -330,6 +330,9 @@ def _do_ssl_handshake(self):
 return
 elif err.args[0] == ssl.SSL_ERROR_EOF:
 return self.handle_close()
+ # TODO: SSLError does not expose alert information
+ elif "SSLV3_ALERT_BAD_CERTIFICATE" in err.args[1]:
+ return self.handle_close()
 raise
 except OSError as err:
 if err.args[0] == errno.ECONNABORTED:
diff --git a/Lib/test/test_imaplib.py b/Lib/test/test_imaplib.py
index 4a45be65724..f16bacd0006 100644
--- a/Lib/test/test_imaplib.py
+++ b/Lib/test/test_imaplib.py
@@ -485,7 +485,8 @@ def test_ssl_raises(self):
 ssl_context.load_verify_locations(CAFILE)
 
 with self.assertRaisesRegex(ssl.CertificateError,
- "hostname '127.0.0.1' doesn't match 'localhost'"):
+ "IP address mismatch, certificate is not valid for "
+ "'127.0.0.1'"):
 _, server = self._setup(SimpleIMAPHandler)
 client = self.imap_class(*server.server_address,
 ssl_context=ssl_context)
@@ -874,7 +875,8 @@ def test_ssl_verified(self):
 
 with self.assertRaisesRegex(
 ssl.CertificateError,
- "hostname '127.0.0.1' doesn't match 'localhost'"):
+ "IP address mismatch, certificate is not valid for "
+ "'127.0.0.1'"):
 with self.reaped_server(SimpleIMAPHandler) as server:
 client = self.imap_class(*server.server_address,
 ssl_context=ssl_context)
diff --git a/Lib/test/test_poplib.py b/Lib/test/test_poplib.py
index 9ba678f2039..4d7a4394086 100644
--- a/Lib/test/test_poplib.py
+++ b/Lib/test/test_poplib.py
@@ -176,6 +176,9 @@ def _do_tls_handshake(self):
 return
 elif err.args[0] == ssl.SSL_ERROR_EOF:
 return self.handle_close()
+ # TODO: SSLError does not expose alert information
+ elif "SSLV3_ALERT_BAD_CERTIFICATE" in err.args[1]:
+ return self.handle_close()
 raise
 except OSError as err:
 if err.args[0] == errno.ECONNABORTED:
diff --git a/Lib/test/test_ssl.py b/Lib/test/test_ssl.py
index e3fa4233ed6..fdf727f788c 100644
--- a/Lib/test/test_ssl.py
+++ b/Lib/test/test_ssl.py
@@ -988,6 +988,19 @@ def test_verify_mode_protocol(self):
 self.assertEqual(ctx.verify_mode, ssl.CERT_REQUIRED)
 self.assertTrue(ctx.check_hostname)
 
+ def test_hostname_checks_common_name(self):
+ ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_CLIENT)
+ self.assertTrue(ctx.hostname_checks_common_name)
+ if ssl.HAS_NEVER_CHECK_COMMON_NAME:
+ ctx.hostname_checks_common_name = True
+ self.assertTrue(ctx.hostname_checks_common_name)
+ ctx.hostname_checks_common_name = False
+ self.assertFalse(ctx.hostname_checks_common_name)
+ ctx.hostname_checks_common_name = True
+ self.assertTrue(ctx.hostname_checks_common_name)
+ else:
+ with self.assertRaises(AttributeError):
+ ctx.hostname_checks_common_name = True
 
 @unittest.skipUnless(have_verify_flags(),
 "verify_flags need OpenSSL > 0.9.8")
@@ -1511,6 +1524,16 @@ def test_bad_idna_in_server_hostname(self):
 ctx.wrap_bio(ssl.MemoryBIO(), ssl.MemoryBIO(),
 server_hostname="xn--.com")
 
+ def test_bad_server_hostname(self):
+ ctx = ssl.create_default_context()
+ with self.assertRaises(ValueError):
+ ctx.wrap_bio(ssl.MemoryBIO(), ssl.MemoryBIO(),
+ server_hostname="")
+ with self.assertRaises(ValueError):
+ ctx.wrap_bio(ssl.MemoryBIO(), ssl.MemoryBIO(),
+ server_hostname=".example.org")
+
+
 class MemoryBIOTests(unittest.TestCase):
 
 def test_read_write(self):
@@ -2536,8 +2559,9 @@ def test_check_hostname(self):
 with server:
 with client_context.wrap_socket(socket.socket(),
 server_hostname="invalid") as s:
- with self.assertRaisesRegex(ssl.CertificateError,
- "hostname 'invalid' doesn't match 'localhost'"):
+ with self.assertRaisesRegex(
+ ssl.CertificateError,
+ "Hostname mismatch, certificate is not valid for 'invalid'."):
 s.connect((HOST, server.port))
 
 # missing server_hostname arg should cause an exception, too
diff --git a/Lib/test/test_urllib2_localnet.py b/Lib/test/test_urllib2_localnet.py
index b2d1e5f9804..52c897af433 100644
--- a/Lib/test/test_urllib2_localnet.py
+++ b/Lib/test/test_urllib2_localnet.py
@@ -573,7 +573,7 @@ def test_https_with_cafile(self):
 cafile=CERT_fakehostname)
 # Good cert, but mismatching hostname
 handler = self.start_https_server(certfile=CERT_fakehostname)
- with self.assertRaises(ssl.CertificateError) as cm:
+ with self.assertRaises(urllib.error.URLError) as cm:
 self.urlopen("https://localhost:%s/bizarre" % handler.port,
 cafile=CERT_fakehostname)
 
diff --git a/Misc/NEWS.d/next/Library/2017-09-08-14-05-33.bpo-31399.FtBrrt.rst b/Misc/NEWS.d/next/Library/2017-09-08-14-05-33.bpo-31399.FtBrrt.rst
new file mode 100644
index 00000000000..e50ce2a1a93
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2017-09-08-14-05-33.bpo-31399.FtBrrt.rst
@@ -0,0 +1,4 @@
+The ssl module now uses OpenSSL's X509_VERIFY_PARAM_set1_host() and
+X509_VERIFY_PARAM_set1_ip() API to verify hostname and IP addresses. Subject
+common name fallback can be disabled with
+SSLContext.hostname_checks_common_name.
diff --git a/Modules/_ssl.c b/Modules/_ssl.c
index c5eec7eded6..ec8c8af54bd 100644
--- a/Modules/_ssl.c
+++ b/Modules/_ssl.c
@@ -64,10 +64,13 @@ static PySocketModule_APIObject PySocketModule;
 #include "openssl/rand.h"
 #include "openssl/bio.h"
 
-/* Set HAVE_X509_VERIFY_PARAM_SET1_HOST for non-autoconf builds */
 #ifndef HAVE_X509_VERIFY_PARAM_SET1_HOST
-# if !defined(LIBRESSL_VERSION_NUMBER) && OPENSSL_VERSION_NUMBER > 0x1000200fL
+# ifdef LIBRESSL_VERSION_NUMBER
+# error "LibreSSL is missing X509_VERIFY_PARAM_set1_host(), see https://github.com/libressl-portable/portable/issues/381"
+# elif OPENSSL_VERSION_NUMBER > 0x1000200fL
 # define HAVE_X509_VERIFY_PARAM_SET1_HOST
+# else
+# error "libssl is too old and does not support X509_VERIFY_PARAM_set1_host()"
 # endif
 #endif
 
@@ -217,11 +220,6 @@ static STACK_OF(X509_OBJECT) *X509_STORE_get0_objects(X509_STORE *store) {
 return store->objs;
 }
 
-static X509_VERIFY_PARAM *X509_STORE_get0_param(X509_STORE *store)
-{
- return store->param;
-}
-
 static int
 SSL_SESSION_has_ticket(const SSL_SESSION *s)
 {
@@ -317,6 +315,10 @@ typedef struct {
 PyObject *set_hostname;
 #endif
 int check_hostname;
+ /* OpenSSL has no API to get hostflags from X509_VERIFY_PARAM* struct.
+ * We have to maintain our own copy. OpenSSL's hostflags default to 0.
+ */
+ unsigned int hostflags;
 } PySSLContext;
 
 typedef struct {
@@ -701,6 +703,74 @@ _setSSLError (const char *errstr, int errcode, const char *filename, int lineno)
 return NULL;
 }
 
+/*
+ * SSL objects
+ */
+
+static int
+_ssl_configure_hostname(PySSLSocket *self, const char* server_hostname)
+{
+ int retval = -1;
+ ASN1_OCTET_STRING *ip;
+ PyObject *hostname;
+ size_t len;
+
+ assert(server_hostname);
+
+ /* Disable OpenSSL's special mode with leading dot in hostname:
+ * When name starts with a dot (e.g ".example.com"), it will be
+ * matched by a certificate valid for any sub-domain of name.
+ */
+ len = strlen(server_hostname);
+ if (len == 0 || *server_hostname == '.') {
+ PyErr_SetString(
+ PyExc_ValueError,
+ "server_hostname cannot be an empty string or start with a "
+ "leading dot.");
+ return retval;
+ }
+
+ /* inet_pton is not available on all platforms. */
+ ip = a2i_IPADDRESS(server_hostname);
+ if (ip == NULL) {
+ ERR_clear_error();
+ }
+
+ hostname = PyUnicode_Decode(server_hostname, len, "idna", "strict");
+ if (hostname == NULL) {
+ goto error;
+ }
+ self->server_hostname = hostname;
+
+ /* Only send SNI extension for non-IP hostnames */
+ if (ip == NULL) {
+ if (!SSL_set_tlsext_host_name(self->ssl, server_hostname)) {
+ _setSSLError(NULL, 0, __FILE__, __LINE__);
+ }
+ }
+ if (self->ctx->check_hostname) {
+ X509_VERIFY_PARAM *param = SSL_get0_param(self->ssl);
+ if (ip == NULL) {
+ if (!X509_VERIFY_PARAM_set1_host(param, server_hostname, 0)) {
+ _setSSLError(NULL, 0, __FILE__, __LINE__);
+ goto error;
+ }
+ } else {
+ if (!X509_VERIFY_PARAM_set1_ip(param, ASN1_STRING_data(ip),
+ ASN1_STRING_length(ip))) {
+ _setSSLError(NULL, 0, __FILE__, __LINE__);
+ goto error;
+ }
+ }
+ }
+ retval = 0;
+ error:
+ if (ip != NULL) {
+ ASN1_OCTET_STRING_free(ip);
+ }
+ return retval;
+}
+
 static PySSLSocket *
 newPySSLSocket(PySSLContext *sslctx, PySocketSockObject *sock,
 enum py_ssl_server_or_client socket_type,
@@ -722,15 +792,6 @@ newPySSLSocket(PySSLContext *sslctx, PySocketSockObject *sock,
 self->shutdown_seen_zero = 0;
 self->owner = NULL;
 self->server_hostname = NULL;
- if (server_hostname != NULL) {
- PyObject *hostname = PyUnicode_Decode(server_hostname, strlen(server_hostname),
- "idna", "strict");
- if (hostname == NULL) {
- Py_DECREF(self);
- return NULL;
- }
- self->server_hostname = hostname;
- }
 self->ssl_errno = 0;
 self->c_errno = 0;
 #ifdef MS_WINDOWS
@@ -761,10 +822,12 @@ newPySSLSocket(PySSLContext *sslctx, PySocketSockObject *sock,
 #endif
 SSL_set_mode(self->ssl, mode);
 
-#if HAVE_SNI
- if (server_hostname != NULL)
- SSL_set_tlsext_host_name(self->ssl, server_hostname);
-#endif
+ if (server_hostname != NULL) {
+ if (_ssl_configure_hostname(self, server_hostname) < 0) {
+ Py_DECREF(self);
+ return NULL;
+ }
+ }
 /* If the socket is in non-blocking mode or timeout mode, set the BIO
 * to non-blocking mode (blocking is the default)
 */
@@ -2711,6 +2774,7 @@ _ssl__SSLContext_impl(PyTypeObject *type, int proto_version)
 PySSLContext *self;
 long options;
 SSL_CTX *ctx = NULL;
+ X509_VERIFY_PARAM *params;
 int result;
 #if defined(SSL_MODE_RELEASE_BUFFERS)
 unsigned long libver;
@@ -2760,6 +2824,7 @@ _ssl__SSLContext_impl(PyTypeObject *type, int proto_version)
 return NULL;
 }
 self->ctx = ctx;
+ self->hostflags = X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS;
 #if defined(OPENSSL_NPN_NEGOTIATED) && !defined(OPENSSL_NO_NEXTPROTONEG)
 self->npn_protocols = NULL;
 #endif
@@ -2858,14 +2923,13 @@ _ssl__SSLContext_impl(PyTypeObject *type, int proto_version)
 sizeof(SID_CTX));
 #undef SID_CTX
 
+ params = SSL_CTX_get0_param(self->ctx);
 #ifdef X509_V_FLAG_TRUSTED_FIRST
- {
- /* Improve trust chain building when cross-signed intermediate
- certificates are present. See https://bugs.python.org/issue23476. */
- X509_STORE *store = SSL_CTX_get_cert_store(self->ctx);
- X509_STORE_set_flags(store, X509_V_FLAG_TRUSTED_FIRST);
- }
+ /* Improve trust chain building when cross-signed intermediate
+ certificates are present. See https://bugs.python.org/issue23476. */
+ X509_VERIFY_PARAM_set_flags(params, X509_V_FLAG_TRUSTED_FIRST);
 #endif
+ X509_VERIFY_PARAM_set_hostflags(params, self->hostflags);
 
 return (PyObject *)self;
 }
@@ -3152,12 +3216,10 @@ set_verify_mode(PySSLContext *self, PyObject *arg, void *c)
 static PyObject *
 get_verify_flags(PySSLContext *self, void *c)
 {
- X509_STORE *store;
 X509_VERIFY_PARAM *param;
 unsigned long flags;
 
- store = SSL_CTX_get_cert_store(self->ctx);
- param = X509_STORE_get0_param(store);
+ param = SSL_CTX_get0_param(self->ctx);
 flags = X509_VERIFY_PARAM_get_flags(param);
 return PyLong_FromUnsignedLong(flags);
 }
@@ -3165,14 +3227,12 @@ get_verify_flags(PySSLContext *self, void *c)
 static int
 set_verify_flags(PySSLContext *self, PyObject *arg, void *c)
 {
- X509_STORE *store;
 X509_VERIFY_PARAM *param;
 unsigned long new_flags, flags, set, clear;
 
 if (!PyArg_Parse(arg, "k", &new_flags))
 return -1;
- store = SSL_CTX_get_cert_store(self->ctx);
- param = X509_STORE_get0_param(store);
+ param = SSL_CTX_get0_param(self->ctx);
 flags = X509_VERIFY_PARAM_get_flags(param);
 clear = flags & ~new_flags;
 set = ~flags & new_flags;
@@ -3220,6 +3280,27 @@ set_options(PySSLContext *self, PyObject *arg, void *c)
 return 0;
 }
 
+static PyObject *
+get_host_flags(PySSLContext *self, void *c)
+{
+ return PyLong_FromUnsignedLong(self->hostflags);
+}
+
+static int
+set_host_flags(PySSLContext *self, PyObject *arg, void *c)
+{
+ X509_VERIFY_PARAM *param;
+ unsigned int new_flags = 0;
+
+ if (!PyArg_Parse(arg, "I", &new_flags))
+ return -1;
+
+ param = SSL_CTX_get0_param(self->ctx);
+ self->hostflags = new_flags;
+ X509_VERIFY_PARAM_set_hostflags(param, new_flags);
+ return 0;
+}
+
 static PyObject *
 get_check_hostname(PySSLContext *self, void *c)
 {
@@ -4104,6 +4185,8 @@ _ssl__SSLContext_get_ca_certs_impl(PySSLContext *self, int binary_form)
 static PyGetSetDef context_getsetlist[] = {
 {"check_hostname", (getter) get_check_hostname,
 (setter) set_check_hostname, NULL},
+ {"_host_flags", (getter) get_host_flags,
+ (setter) set_host_flags, NULL},
 {"options", (getter) get_options,
 (setter) set_options, NULL},
 {"verify_flags", (getter) get_verify_flags,
@@ -5491,6 +5574,31 @@ PyInit__ssl(void)
 SSL_OP_NO_COMPRESSION);
 #endif
 
+#ifdef X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT
+ PyModule_AddIntConstant(m, "HOSTFLAG_ALWAYS_CHECK_SUBJECT",
+ X509_CHECK_FLAG_ALWAYS_CHECK_SUBJECT);
+#endif
+#ifdef X509_CHECK_FLAG_NEVER_CHECK_SUBJECT
+ PyModule_AddIntConstant(m, "HOSTFLAG_NEVER_CHECK_SUBJECT",
+ X509_CHECK_FLAG_NEVER_CHECK_SUBJECT);
+#endif
+#ifdef X509_CHECK_FLAG_NO_WILDCARDS
+ PyModule_AddIntConstant(m, "HOSTFLAG_NO_WILDCARDS",
+ X509_CHECK_FLAG_NO_WILDCARDS);
+#endif
+#ifdef X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS
+ PyModule_AddIntConstant(m, "HOSTFLAG_NO_PARTIAL_WILDCARDS",
+ X509_CHECK_FLAG_NO_PARTIAL_WILDCARDS);
+#endif
+#ifdef X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS
+ PyModule_AddIntConstant(m, "HOSTFLAG_MULTI_LABEL_WILDCARDS",
+ X509_CHECK_FLAG_MULTI_LABEL_WILDCARDS);
+#endif
+#ifdef X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS
+ PyModule_AddIntConstant(m, "HOSTFLAG_SINGLE_LABEL_SUBDOMAINS",
+ X509_CHECK_FLAG_SINGLE_LABEL_SUBDOMAINS);
+#endif
+
 #if HAVE_SNI
 r = Py_True;
 #else
diff --git a/PC/pyconfig.h b/PC/pyconfig.h
index db745dee761..d2a3f5dd39b 100644
--- a/PC/pyconfig.h
+++ b/PC/pyconfig.h
@@ -687,4 +687,7 @@ Py_NO_ENABLE_SHARED to find out. Also support MS_NO_COREDLL for b/w compat */
 /* framework name */
 #define _PYTHONFRAMEWORK ""
 
+/* Define if libssl has X509_VERIFY_PARAM_set1_host and related function */
+#define HAVE_X509_VERIFY_PARAM_SET1_HOST 1
+
 #endif /* !Py_CONFIG_H */
diff --git a/setup.py b/setup.py
index a6f4488cc99..ba0a7624cfc 100644
--- a/setup.py
+++ b/setup.py
@@ -363,6 +363,16 @@ def print_three_column(lst):
 print_three_column(failed)
 print()
 
+ if any('_ssl' in l
+ for l in (missing, self.failed, self.failed_on_import)):
+ print()
+ print("Could not build the ssl module!")
+ print("Python requires an OpenSSL 1.0.2 or 1.1 compatible "
+ "libssl with X509_VERIFY_PARAM_set1_host().")
+ print("LibreSSL 2.6.4 and earlier do not provide the necessary "
+ "APIs, https://github.com/libressl-portable/portable/issues/381")
+ print()
+
 def build_extension(self, ext):
 
 if ext.name == '_ctypes':
@@ -2144,13 +2154,16 @@ def split_var(name, sep):
 if krb5_h:
 ssl_incs.extend(krb5_h)
 
- ssl_ext = Extension(
- '_ssl', ['_ssl.c'],
- include_dirs=openssl_includes,
- library_dirs=openssl_libdirs,
- libraries=openssl_libs,
- depends=['socketmodule.h']
- )
+ if config_vars.get("HAVE_X509_VERIFY_PARAM_SET1_HOST"):
+ ssl_ext = Extension(
+ '_ssl', ['_ssl.c'],
+ include_dirs=openssl_includes,
+ library_dirs=openssl_libdirs,
+ libraries=openssl_libs,
+ depends=['socketmodule.h']
+ )
+ else:
+ ssl_ext = None
 
 hashlib_ext = Extension(
 '_hashlib', ['_hashopenssl.c'],

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