crypto: add preemptive threading support

Some primitives are designed to be used in a multi-threaded environment,
if supported, e.g., Argon2.

This patch adds support for preemptive threading and basic synchronization
primitives for platforms compliant with POSIX threads or Windows CRT.
Native functions are wrapped to provide a common (internal) API.

Threading support can be disabled at compile time. If enabled, threading
is disabled by default and needs to be explicitly enabled by the user.

Thread enablement requires an explicit limit on the number of threads that
OpenSSL may spawn (non-negative integer/infinity). The limit may be changed.

Signed-off-by: Čestmír Kalina <ckalina@redhat.com>

Reviewed-by: Hugo Landau <hlandau@openssl.org>
Reviewed-by: Matt Caswell <matt@openssl.org>
(Merged from https://github.com/openssl/openssl/pull/12255)

1 files changed, 23 insertions, 0 deletions

diff --git a/include/openssl/thread.h b/include/openssl/thread.h
new file mode 100644
index 0000000000..68ecf9c4c4
--- /dev/null
+++ b/include/openssl/thread.h
@@ -0,0 +1,23 @@
+/*
+ * Copyright 1995-2022 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright (c) 2002, Oracle and/or its affiliates. All rights reserved
+ *
+ * Licensed under the Apache License 2.0 (the "License").  You may not use
+ * this file except in compliance with the License.  You can obtain a copy
+ * in the file LICENSE in the source distribution or at
+ * https://www.openssl.org/source/license.html
+ */
+
+#ifndef OPENSSL_THREAD_H
+# define OPENSSL_THREAD_H
+
+# define OSSL_THREAD_SUPPORT_FLAG_THREAD_POOL (1U<<0)
+# define OSSL_THREAD_SUPPORT_FLAG_DEFAULT_SPAWN (1U<<1)
+
+# include <openssl/types.h>
+
+uint32_t OSSL_get_thread_support_flags(void);
+int OSSL_set_max_threads(OSSL_LIB_CTX *ctx, uint64_t max_threads);
+uint64_t OSSL_get_max_threads(OSSL_LIB_CTX *ctx);
+
+#endif /* OPENSSL_THREAD_H */