Multi-thread support

The new module tlock provides the locking callback function the OpenSSL library
requires for the case where multiple threads enter it concurrently. tlock is
now automatically initialized by sslconnection's module startup code, and does
nothing if the executing Python environment does not provide threading.

Note that this does introduce some overhead. For example, during the transfer
of CERTFILE by test_socketserver, about 300 locking callbacks are received.

dtls/openssl.py

@@ -82,6 +82,7 @@ SSL_SESS_CACHE_NO_INTERNAL = \
 SSL_FILE_TYPE_PEM = 1
 GEN_DIRNAME = 4
 NID_subject_alt_name = 85
+CRYPTO_LOCK = 1
 
 #
 # Integer constants - internal
@@ -442,6 +443,8 @@ __all__ = ["BIO_NOCLOSE", "BIO_CLOSE",
            "SSL_SESS_CACHE_NO_INTERNAL_STORE", "SSL_SESS_CACHE_NO_INTERNAL",
            "SSL_FILE_TYPE_PEM",
            "GEN_DIRNAME", "NID_subject_alt_name",
+           "CRYPTO_LOCK",
+           "CRYPTO_set_locking_callback",
            "DTLSv1_get_timeout", "DTLSv1_handle_timeout",
            "DTLSv1_listen",
            "BIO_gets", "BIO_read", "BIO_get_mem_data",
@@ -463,6 +466,9 @@ map(lambda x: _make_function(*x), (
     ("SSL_load_error_strings", libssl, ((None, "ret"),)),
     ("SSLeay", libcrypto, ((c_long_parm, "ret"),)),
     ("SSLeay_version", libcrypto, ((c_char_p, "ret"), (c_int, "t"))),
+    ("CRYPTO_set_locking_callback", libcrypto,
+     ((None, "ret"), (c_void_p, "func")), False),
+    ("CRYPTO_num_locks", libcrypto, ((c_int, "ret"),)),
     ("DTLSv1_server_method", libssl, ((DTLSv1Method, "ret"),)),
     ("DTLSv1_client_method", libssl, ((DTLSv1Method, "ret"),)),
     ("SSL_CTX_new", libssl, ((SSLCTX, "ret"), (DTLSv1Method, "meth"))),
@@ -589,9 +595,18 @@ map(lambda x: _make_function(*x), (
 #
 # Wrappers - functions generally equivalent to OpenSSL library macros
 #
-_rint_voidp_ubytep_uintp = CFUNCTYPE(c_int, c_void_p, POINTER(c_ubyte),
+_rvoid_int_int_charp_int = CFUNCTYPE(None, c_int, c_int, c_char_p, c_int)
-                                     POINTER(c_uint))
+
-_rint_voidp_ubytep_uint = CFUNCTYPE(c_int, c_void_p, POINTER(c_ubyte), c_uint)
+def CRYPTO_set_locking_callback(locking_function):
+    def py_locking_function(mode, n, file, line):
+        try:
+            locking_function(mode, n, file, line)
+        except:
+            _logger.exception("Thread locking failed")
+
+    global _locking_cb  # for keep-alive
+    _locking_cb = _rvoid_int_int_charp_int(py_locking_function)
+    _CRYPTO_set_locking_callback(_locking_cb)
 
 def SSL_CTX_set_session_cache_mode(ctx, mode):
     # Returns the previous value of mode
@@ -601,6 +616,10 @@ def SSL_CTX_set_read_ahead(ctx, m):
     # Returns the previous value of m
     _SSL_CTX_ctrl(ctx, SSL_CTRL_SET_READ_AHEAD, m, None)
 
+_rint_voidp_ubytep_uintp = CFUNCTYPE(c_int, c_void_p, POINTER(c_ubyte),
+                                     POINTER(c_uint))
+_rint_voidp_ubytep_uint = CFUNCTYPE(c_int, c_void_p, POINTER(c_ubyte), c_uint)
+
 def SSL_CTX_set_cookie_cb(ctx, generate, verify):
     def py_generate_cookie_cb(ssl, cookie, cookie_len):
         try:

dtls/sslconnection.py

@@ -35,6 +35,7 @@ from err import SSL_ERROR_WANT_READ, SSL_ERROR_SYSCALL
 from err import ERR_COOKIE_MISMATCH, ERR_NO_CERTS
 from err import ERR_NO_CIPHER, ERR_HANDSHAKE_TIMEOUT, ERR_PORT_UNREACHABLE
 from x509 import _X509, decode_cert
+from tlock import tlock_init
 from openssl import *
 from util import _Rsrc, _BIO
 
@@ -50,6 +51,7 @@ CERT_REQUIRED = 2
 #
 SSL_library_init()
 SSL_load_error_strings()
+tlock_init()
 DTLS_OPENSSL_VERSION_NUMBER = SSLeay()
 DTLS_OPENSSL_VERSION = SSLeay_version(SSLEAY_VERSION)
 DTLS_OPENSSL_VERSION_INFO = (

dtls/tlock.py

@@ -0,0 +1,36 @@
+# TLock: OpenSSL lock support on thread-enabled systems. Written by Ray Brown.
+"""TLock
+
+This module provides the callbacks required by the OpenSSL library in situations
+where it is being entered concurrently by multiple threads. This module is
+enagaged automatically by the PyDTLS package on systems that have Python
+threading support. It does not have client-visible components.
+"""
+
+from logging import getLogger
+from openssl import *
+
+try:
+    import threading
+except ImportError:
+    pass
+
+_logger = getLogger(__name__)
+DO_DEBUG_LOG = False
+
+def tlock_init():
+    if not globals().has_key("threading"):
+        return  # nothing to configure
+    global _locks
+    num_locks = CRYPTO_num_locks()
+    _locks = tuple(threading.Lock() for _ in range(num_locks))
+    CRYPTO_set_locking_callback(_locking_function)
+
+def _locking_function(mode, n, file, line):
+    if DO_DEBUG_LOG:
+        _logger.debug("Thread lock:  mode: %d, n: %d, file: %s, line: %d",
+                      mode, n, file, line)
+    if mode & CRYPTO_LOCK:
+        _locks[n].acquire()
+    else:
+        _locks[n].release()