2 files changed, 51 insertions, 1 deletions
diff --git a/cryptography/hazmat/bindings/openssl/binding.py b/cryptography/hazmat/bindings/openssl/binding.py
index 1c17a5b2..cde3bdbd 100644
--- a/cryptography/hazmat/bindings/openssl/binding.py
+++ b/cryptography/hazmat/bindings/openssl/binding.py
@@ -14,6 +14,7 @@
 from __future__ import absolute_import, division, print_function
 
 import sys
+import threading
 
 from cryptography.hazmat.bindings.utils import build_ffi
 
@@ -70,6 +71,10 @@ class Binding(object):
         "x509v3",
     ]
 
+    _locks = None
+    _lock_cb_handle = None
+    _lock_init_lock = threading.Lock()
+
     ffi = None
     lib = None
 
@@ -95,3 +100,43 @@ class Binding(object):
     def is_available(cls):
         # OpenSSL is the only binding so for now it must always be available
         return True
+
+    @classmethod
+    def init_static_locks(cls):
+        with cls._lock_init_lock:
+            cls._ensure_ffi_initialized()
+
+            if not cls._lock_cb_handle:
+                cls._lock_cb_handle = cls.ffi.callback(
+                    "void(int, int, const char *, int)",
+                    cls._lock_cb
+                )
+
+            # use Python's implementation if available
+
+            __import__("_ssl")
+
+            if cls.lib.CRYPTO_get_locking_callback() != cls.ffi.NULL:
+                return
+
+            # otherwise setup our version
+
+            num_locks = cls.lib.CRYPTO_num_locks()
+            cls._locks = [threading.Lock() for n in range(num_locks)]
+
+            cls.lib.CRYPTO_set_locking_callback(cls._lock_cb_handle)
+
+    @classmethod
+    def _lock_cb(cls, mode, n, file, line):
+        lock = cls._locks[n]
+
+        if mode & cls.lib.CRYPTO_LOCK:
+            lock.acquire()
+        elif mode & cls.lib.CRYPTO_UNLOCK:
+            lock.release()
+        else:
+            raise RuntimeError(
+                "Unknown lock mode {0}: lock={1}, file={2}, line={3}".format(
+                    mode, n, file, line
+                )
+            )
diff --git a/cryptography/hazmat/bindings/openssl/crypto.py b/cryptography/hazmat/bindings/openssl/crypto.py
index 40d91bf2..81d13b73 100644
--- a/cryptography/hazmat/bindings/openssl/crypto.py
+++ b/cryptography/hazmat/bindings/openssl/crypto.py
@@ -27,6 +27,11 @@ static const int CRYPTO_MEM_CHECK_ON;
 static const int CRYPTO_MEM_CHECK_OFF;
 static const int CRYPTO_MEM_CHECK_ENABLE;
 static const int CRYPTO_MEM_CHECK_DISABLE;
+static const int CRYPTO_LOCK;
+static const int CRYPTO_UNLOCK;
+static const int CRYPTO_READ;
+static const int CRYPTO_WRITE;
+static const int CRYPTO_LOCK_SSL;
 """
 
 FUNCTIONS = """
@@ -43,6 +48,7 @@ void CRYPTO_set_locking_callback(void(*)(int, int, const char *, int));
 void CRYPTO_set_id_callback(unsigned long (*)(void));
 unsigned long (*CRYPTO_get_id_callback(void))(void);
 void (*CRYPTO_get_locking_callback(void))(int, int, const char *, int);
+void CRYPTO_lock(int, int, const char *, int);
 
 void OPENSSL_free(void *);
 """
@@ -51,7 +57,6 @@ MACROS = """
 void CRYPTO_add(int *, int, int);
 void CRYPTO_malloc_init(void);
 void CRYPTO_malloc_debug_init(void);
-
 """
 
 CUSTOMIZATIONS = """