Move OpenSSL initialization to a single place, make library usage thread-safe.

While doing some reading about OpenSSL, I noticed a couple of things that
needed to be improved with our usage of OpenSSL.

1) We had initialization of the library done in multiple modules.  This has now
   been moved to a core function that gets executed during Asterisk startup.
   We already link OpenSSL into the core for TCP/TLS functionality, so this
   was the most logical place to do it.

2) OpenSSL is not thread-safe by default.  However, making it thread safe is
   very easy.  We just have to provide a couple of callbacks.  One callback
   returns a thread ID.  The other handles locking.  For more information,
   start with the "Is OpenSSL thread-safe?" question on the FAQ page of
   openssl.org.


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@205120 65c4cc65-6c06-0410-ace0-fbb531ad65f3

main/ssl.c

@@ -0,0 +1,100 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2009, Digium, Inc.
+ *
+ * Russell Bryant <russell@digium.com>
+ *
+ * See http://www.asterisk.org for more information about
+ * the Asterisk project. Please do not directly contact
+ * any of the maintainers of this project for assistance;
+ * the project provides a web site, mailing lists and IRC
+ * channels for your use.
+ *
+ * This program is free software, distributed under the terms of
+ * the GNU General Public License Version 2. See the LICENSE file
+ * at the top of the source tree.
+ */
+
+/*! 
+ * \file
+ * \brief Common OpenSSL support code
+ *
+ * \author Russell Bryant <russell@digium.com>
+ */
+
+#include "asterisk.h"
+
+ASTERISK_FILE_VERSION(__FILE__, "$Revision$")
+
+#ifdef HAVE_OPENSSL
+#include <openssl/ssl.h>
+#include <openssl/err.h>
+#endif
+
+#include "asterisk/_private.h" /* ast_ssl_init() */
+
+#include "asterisk/utils.h"
+#include "asterisk/lock.h"
+
+#ifdef HAVE_OPENSSL
+
+static ast_mutex_t *ssl_locks;
+
+static int ssl_num_locks;
+
+static unsigned long ssl_threadid(void)
+{
+        return pthread_self();
+}
+
+static void ssl_lock(int mode, int n, const char *file, int line)
+{
+        if (n < 0 || n >= ssl_num_locks) {
+                ast_log(LOG_ERROR, "OpenSSL is full of LIES!!! - "
+				"ssl_num_locks '%d' - n '%d'\n",
+                                ssl_num_locks, n);
+                return;
+        }
+
+        if (mode & CRYPTO_LOCK) {
+                ast_mutex_lock(&ssl_locks[n]);
+        } else {
+                ast_mutex_unlock(&ssl_locks[n]);
+        }
+}
+
+#endif /* HAVE_OPENSSL */
+
+/*!
+ * \internal
+ * \brief Common OpenSSL initialization for all of Asterisk.
+ */
+int ast_ssl_init(void)
+{
+#ifdef HAVE_OPENSSL
+        unsigned int i;
+
+        SSL_library_init();
+        SSL_load_error_strings();
+        ERR_load_crypto_strings();
+        ERR_load_BIO_strings();
+        OpenSSL_add_all_algorithms();
+
+        /* Make OpenSSL thread-safe. */
+
+        CRYPTO_set_id_callback(ssl_threadid);
+
+        ssl_num_locks = CRYPTO_num_locks();
+        if (!(ssl_locks = ast_calloc(ssl_num_locks, sizeof(ssl_locks[0])))) {
+                return -1;
+        }
+        for (i = 0; i < ssl_num_locks; i++) {
+                ast_mutex_init(&ssl_locks[i]);
+        }
+        CRYPTO_set_locking_callback(ssl_lock);
+
+#endif /* HAVE_OPENSSL */
+        return 0;
+}
+