Address OpenSSL initialization issues when using third-party libraries.

When Asterisk is used with various third-party libraries (CURL, PostgresSQL,
many others) that have the ability themselves to use OpenSSL, it is possible
for conflicts to arise in how the OpenSSL libraries are initialized and
shutdown. This patch addresses these conflicts by 'wrapping' the important
functions from the OpenSSL libraries in a new shared library that is part
of Asterisk itself, and is loaded in such a way as to ensure that *all*
calls to these functions will be dispatched through the Asterisk wrapper
functions, not the native functions.

This new library is optional, but enabled by default. See the CHANGES file
for documentation on how to disable it.

Along the way, this patch also makes a few other minor changes:

* Changes MODULES_DIR to ASTMODDIR throughout the build system, in order to
  more closely match what is used during run-time configuration.

* Corrects some errors in the configure script where AC_CHECK_TOOLS was used
  instead of AC_PATH_PROG.

* Adds a new variable for linker flags in the build system (DYLINK), used for
  producing true shared libraries (as opposed to the dynamically loadable
  modules that the build system produces for 'regular' Asterisk modules).

* Moves the Makefile bits that handle installation and uninstallation of the
  main Asterisk binary into main/Makefile from the top-level Makefile.

* Moves a couple of useful preprocessor macros from optional_api.h to
  asterisk.h.

Review: https://reviewboard.asterisk.org/r/1006/


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@353317 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 235 insertions, 0 deletions

diff --git a/main/libasteriskssl.c b/main/libasteriskssl.c
new file mode 100644
index 000000000..8b2d8b0a8
--- /dev/null
+++ b/main/libasteriskssl.c
@@ -0,0 +1,235 @@
+/*
+ * Asterisk -- An open source telephony toolkit.
+ *
+ * Copyright (C) 2009-2012, 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 <dlfcn.h>
+
+#include "asterisk/_private.h" /* ast_ssl_init() */
+
+#include "asterisk/utils.h"
+#include "asterisk/lock.h"
+
+#ifdef HAVE_OPENSSL
+
+#define get_OpenSSL_function(func) do { real_##func = dlsym(RTLD_NEXT, __stringify(func)); } while(0)
+
+static int startup_complete;
+
+static ast_mutex_t *ssl_locks;
+
+static int ssl_num_locks;
+
+static unsigned long ssl_threadid(void)
+{
+	return (unsigned long) 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]);
+	}
+}
+
+int SSL_library_init(void)
+{
+#if defined(AST_DEVMODE)
+	if (startup_complete) {
+		ast_debug(1, "Called after startup... ignoring!\n");
+	}
+#endif
+	return 0;
+}
+
+void SSL_load_error_strings(void)
+{
+#if defined(AST_DEVMODE)
+	if (startup_complete) {
+		ast_debug(1, "Called after startup... ignoring!\n");
+	}
+#endif
+}
+
+void ERR_load_SSL_strings(void)
+{
+#if defined(AST_DEVMODE)
+	if (startup_complete) {
+		ast_debug(1, "Called after startup... ignoring!\n");
+	}
+#endif
+}
+
+void ERR_load_crypto_strings(void)
+{
+#if defined(AST_DEVMODE)
+	if (startup_complete) {
+		ast_debug(1, "Called after startup... ignoring!\n");
+	}
+#endif
+}
+
+void ERR_load_BIO_strings(void)
+{
+#if defined(AST_DEVMODE)
+	if (startup_complete) {
+		ast_debug(1, "Called after startup... ignoring!\n");
+	}
+#endif
+}
+
+void CRYPTO_set_id_callback(unsigned long (*func)(void))
+{
+#if defined(AST_DEVMODE)
+	if (startup_complete) {
+		ast_debug(1, "Called after startup... ignoring!\n");
+	}
+#endif
+}
+
+void CRYPTO_set_locking_callback(void (*func)(int mode,int type, const char *file, int line))
+{
+#if defined(AST_DEVMODE)
+	if (startup_complete) {
+		ast_debug(1, "Called after startup... ignoring!\n");
+	}
+#endif
+}
+
+void ERR_free_strings(void)
+{
+	/* we can't allow this to be called, ever */
+}
+
+#endif /* HAVE_OPENSSL */
+
+/*!
+ * \internal
+ * \brief Common OpenSSL initialization for all of Asterisk.
+ */
+int ast_ssl_init(void)
+{
+#ifdef HAVE_OPENSSL
+	unsigned int i;
+	int (*real_SSL_library_init)(void);
+	void (*real_CRYPTO_set_id_callback)(unsigned long (*)(void));
+	void (*real_CRYPTO_set_locking_callback)(void (*)(int, int, const char *, int));
+	void (*real_SSL_load_error_strings)(void);
+	void (*real_ERR_load_SSL_strings)(void);
+	void (*real_ERR_load_crypto_strings)(void);
+	void (*real_ERR_load_BIO_strings)(void);
+	const char *errstr;
+
+	/* clear any previous dynamic linker errors */
+	dlerror();
+	get_OpenSSL_function(SSL_library_init);
+	if ((errstr = dlerror()) != NULL) {
+		ast_debug(1, "unable to get real address of SSL_library_init: %s\n", errstr);
+		/* there is no way to continue in this situation... SSL will
+		 * likely be broken in this process
+		 */
+		return -1;
+	} else {
+		real_SSL_library_init();
+	}
+
+	/* Make OpenSSL usage thread-safe. */
+
+	dlerror();
+	get_OpenSSL_function(CRYPTO_set_id_callback);
+	if ((errstr = dlerror()) != NULL) {
+		ast_debug(1, "unable to get real address of CRYPTO_set_id_callback: %s\n", errstr);
+		/* there is no way to continue in this situation... SSL will
+		 * likely be broken in this process
+		 */
+		return -1;
+	} else {
+		real_CRYPTO_set_id_callback(ssl_threadid);
+	}
+
+	dlerror();
+	get_OpenSSL_function(CRYPTO_set_locking_callback);
+	if ((errstr = dlerror()) != NULL) {
+		ast_debug(1, "unable to get real address of CRYPTO_set_locking_callback: %s\n", errstr);
+		/* there is no way to continue in this situation... SSL will
+		 * likely be broken in this process
+		 */
+		return -1;
+	} else {
+		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]);
+		}
+		real_CRYPTO_set_locking_callback(ssl_lock);
+	}
+
+	/* after this point, we don't check for errors from the dlsym() calls,
+	 * under the assumption that if the ones above were successful, all
+	 * the rest will be too. this assumption holds as long as OpenSSL still
+	 * provides all of these functions.
+	 */
+
+	get_OpenSSL_function(SSL_load_error_strings);
+	real_SSL_load_error_strings();
+
+	get_OpenSSL_function(ERR_load_SSL_strings);
+	real_ERR_load_SSL_strings();
+
+	get_OpenSSL_function(ERR_load_crypto_strings);
+	real_ERR_load_crypto_strings();
+
+	get_OpenSSL_function(ERR_load_BIO_strings);
+	real_ERR_load_BIO_strings();
+
+#if 0
+	/* currently this is just another call to SSL_library_init, so we don't call it */
+	OpenSSL_add_all_algorithms();
+#endif
+
+	startup_complete = 1;
+
+#endif /* HAVE_OPENSSL */
+	return 0;
+}
+