Added parameter to ssl_context hook for constructing default context

Signed-off-by: Tero Saarni <tero.saarni@est.tech>

examples/example_config.py

@@ -215,32 +215,26 @@ def worker_int(worker):
 def worker_abort(worker):
     worker.log.info("worker received SIGABRT signal")
 
-def ssl_context(conf):
+def ssl_context(conf, default_ssl_context_factory):
     import ssl
 
-    def set_defaults(context):
-        context.verify_mode = conf.cert_reqs
-        context.minimum_version = ssl.TLSVersion.TLSv1_3
-        if conf.ciphers:
-            context.set_ciphers(conf.ciphers)
-        if conf.ca_certs:
-            context.load_verify_locations(cafile=conf.ca_certs)
+    # The default SSLContext returned by the factory function is initialized
+    # with the TLS parameters from config, including TLS certificates and other
+    # parameters.
+    context = default_ssl_context_factory()
 
-    # Return different server certificate depending which hostname the client
-    # uses. Requires Python 3.7 or later.
+    # The SSLContext can be further customized, for example by enforcing
+    # minimum TLS version.
+    context.minimum_version = ssl.TLSVersion.TLSv1_3
+
+    # Server can also return different server certificate depending which
+    # hostname the client uses. Requires Python 3.7 or later.
     def sni_callback(socket, server_hostname, context):
         if server_hostname == "foo.127.0.0.1.nip.io":
-            new_context = ssl.SSLContext()
+            new_context = default_ssl_context_factory()
             new_context.load_cert_chain(certfile="foo.pem", keyfile="foo-key.pem")
-            set_defaults(new_context)
             socket.context = new_context
 
-    context = ssl.SSLContext(conf.ssl_version)
     context.sni_callback = sni_callback
-    set_defaults(context)
-
-    # Load fallback certificate that will be returned when there is no match
-    # or client did not set TLS SNI (server_hostname == None)
-    context.load_cert_chain(certfile=conf.certfile, keyfile=conf.keyfile)
 
     return context

gunicorn/config.py

@@ -1970,11 +1970,11 @@ class OnExit(Setting):
 class NewSSLContext(Setting):
     name = "ssl_context"
     section = "Server Hooks"
-    validator = validate_callable(1)
+    validator = validate_callable(2)
     type = callable
 
-    def ssl_context(config):
-        return None
+    def ssl_context(config, default_ssl_context_factory):
+        return default_ssl_context_factory()
 
     default = staticmethod(ssl_context)
     desc = """\
@@ -1983,7 +1983,10 @@ class NewSSLContext(Setting):
         Allows fully customized SSL context to be used in place of the default
         context.
 
-        The callable needs to accept a single instance variable for the Config.
+        The callable needs to accept an instance variable for the Config and
+        a factory function that returns default SSLContext which is initialized
+        with certificates, private key, cert_reqs, and ciphers according to
+        config and can be further customized by the callable.
         The callable needs to return SSLContext object.
         """
 

gunicorn/sock.py

@@ -212,8 +212,7 @@ def close_sockets(listeners, unlink=True):
             os.unlink(sock_name)
 
 def ssl_context(conf):
-    context = conf.ssl_context(conf)
-    if context is None:
+    def default_ssl_context_factory():
         context = ssl.SSLContext(conf.ssl_version)
         context.load_cert_chain(certfile=conf.certfile, keyfile=conf.keyfile)
         context.verify_mode = conf.cert_reqs
@@ -221,8 +220,9 @@ def ssl_context(conf):
             context.set_ciphers(conf.ciphers)
         if conf.ca_certs:
             context.load_verify_locations(cafile=conf.ca_certs)
+        return context
 
-    return context
+    return conf.ssl_context(conf, default_ssl_context_factory)
 
 def ssl_wrap_socket(sock, conf):
     return ssl_context(conf).wrap_socket(sock, server_side=True,