crypto: Make unloading of crypto safer

Facts:
crypto nif-lib registers callback functions that openssl uses
for memory management and thread synchronization. The callback
functions can only be set once, openssl does not allow changing the
callback functions.

Problem:
If openssl is dynamicly linked to crypto, you might get s scenario
where the crypto lib is unloaded while leaving openssl loaded
with its old pointers to the unloaded crypto code intact.
If crypto is then reloaded (by init:restart() for example), the crypto
nif-lib might get relocated at a different address. crypto calls
openssl which in turn calls the old invalid callback functions...kaboom.

Solution:
Break apart the callback functions into a separate dynamic lib that
crypto loads with dlopen. When crypto is unloaded the callback lib is
left in place to be reused if/when crypto is loaded again.

1 files changed, 42 insertions, 0 deletions

diff --git a/lib/crypto/c_src/crypto_callback.h b/lib/crypto/c_src/crypto_callback.h
new file mode 100644
index 0000000000..a0c828b502
--- /dev/null
+++ b/lib/crypto/c_src/crypto_callback.h
@@ -0,0 +1,42 @@
+/* 
+ * %CopyrightBegin%
+ *
+ * Copyright Ericsson AB 2012. All Rights Reserved.
+ *
+ * The contents of this file are subject to the Erlang Public License,
+ * Version 1.1, (the "License"); you may not use this file except in
+ * compliance with the License. You should have received a copy of the
+ * Erlang Public License along with this software. If not, it can be
+ * retrieved online at http://www.erlang.org/.
+ *
+ * Software distributed under the License is distributed on an "AS IS"
+ * basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
+ * the License for the specific language governing rights and limitations
+ * under the License.
+ *
+ * %CopyrightEnd%
+ */
+
+struct crypto_callbacks
+{
+    size_t sizeof_me;
+
+    void* (*crypto_alloc)(size_t size);
+    void* (*crypto_realloc)(void* ptr, size_t size);
+    void (*crypto_free)(void* ptr);
+
+    /* openssl callbacks */
+  #ifdef OPENSSL_THREADS
+    void (*locking_function)(int mode, int n, const char *file, int line);
+    unsigned long (*id_function)(void);
+    struct CRYPTO_dynlock_value* (*dyn_create_function)(const char *file,
+							int line);
+    void (*dyn_lock_function)(int mode, struct CRYPTO_dynlock_value* ptr,
+			      const char *file, int line);
+    void (*dyn_destroy_function)(struct CRYPTO_dynlock_value *ptr,
+				 const char *file, int line);
+  #endif /* OPENSSL_THREADS */
+};
+
+typedef struct crypto_callbacks* get_crypto_callbacks_t(int nlocks);
+