OPENSSL_INIT_CRYPTO(3SSL) OpenSSL OPENSSL_INIT_CRYPTO(3SSL)
NAME
OPENSSL_INIT_new, OPENSSL_INIT_set_config_filename,
OPENSSL_INIT_set_config_appname, OPENSSL_INIT_set_config_file_flags,
OPENSSL_INIT_free, OPENSSL_init_crypto, OPENSSL_cleanup, OPENSSL_atexit,
OPENSSL_thread_stop_ex, OPENSSL_thread_stop - OpenSSL initialisation and
deinitialisation functions
SYNOPSIS
#include <openssl/crypto.h>
void OPENSSL_cleanup(void);
int OPENSSL_init_crypto(uint64_t opts, const OPENSSL_INIT_SETTINGS *settings);
int OPENSSL_atexit(void (*handler)(void));
void OPENSSL_thread_stop_ex(OSSL_LIB_CTX *ctx);
void OPENSSL_thread_stop(void);
OPENSSL_INIT_SETTINGS *OPENSSL_INIT_new(void);
int OPENSSL_INIT_set_config_filename(OPENSSL_INIT_SETTINGS *init,
const char* filename);
int OPENSSL_INIT_set_config_file_flags(OPENSSL_INIT_SETTINGS *init,
unsigned long flags);
int OPENSSL_INIT_set_config_appname(OPENSSL_INIT_SETTINGS *init,
const char* name);
void OPENSSL_INIT_free(OPENSSL_INIT_SETTINGS *init);
DESCRIPTION
During normal operation OpenSSL (libcrypto) will allocate various
resources at start up that must, subsequently, be freed on close down of
the library. Additionally some resources are allocated on a per thread
basis (if the application is multi-threaded), and these resources must
be freed prior to the thread closing.
As of version 1.1.0 OpenSSL will automatically allocate all resources
that it needs so no explicit initialisation is required. Similarly it
will also automatically deinitialise as required.
However, there may be situations when explicit initialisation is
desirable or needed, for example when some nondefault initialisation is
required. The function OPENSSL_init_crypto() can be used for this
purpose for libcrypto (see also OPENSSL_init_ssl(3) for the libssl
equivalent).
Numerous internal OpenSSL functions call OPENSSL_init_crypto().
Therefore, in order to perform nondefault initialisation,
OPENSSL_init_crypto() MUST be called by application code prior to any
other OpenSSL function calls.
The opts parameter specifies which aspects of libcrypto should be
initialised. Valid options are:
OPENSSL_INIT_NO_LOAD_CRYPTO_STRINGS
Suppress automatic loading of the libcrypto error strings. This
option is not a default option. Once selected subsequent calls to
OPENSSL_init_crypto() with the option
OPENSSL_INIT_LOAD_CRYPTO_STRINGS will be ignored.
OPENSSL_INIT_LOAD_CRYPTO_STRINGS
Automatic loading of the libcrypto error strings. With this option
the library will automatically load the libcrypto error strings.
This option is a default option. Once selected subsequent calls to
OPENSSL_init_crypto() with the option
OPENSSL_INIT_NO_LOAD_CRYPTO_STRINGS will be ignored.
OPENSSL_INIT_ADD_ALL_CIPHERS
With this option the library will automatically load and make
available all libcrypto ciphers. This option is a default option.
Once selected subsequent calls to OPENSSL_init_crypto() with the
option OPENSSL_INIT_NO_ADD_ALL_CIPHERS will be ignored.
OPENSSL_INIT_ADD_ALL_DIGESTS
With this option the library will automatically load and make
available all libcrypto digests. This option is a default option.
Once selected subsequent calls to OPENSSL_init_crypto() with the
option OPENSSL_INIT_NO_ADD_ALL_DIGESTS will be ignored.
OPENSSL_INIT_NO_ADD_ALL_CIPHERS
With this option the library will suppress automatic loading of
libcrypto ciphers. This option is not a default option. Once
selected subsequent calls to OPENSSL_init_crypto() with the option
OPENSSL_INIT_ADD_ALL_CIPHERS will be ignored.
OPENSSL_INIT_NO_ADD_ALL_DIGESTS
With this option the library will suppress automatic loading of
libcrypto digests. This option is not a default option. Once
selected subsequent calls to OPENSSL_init_crypto() with the option
OPENSSL_INIT_ADD_ALL_DIGESTS will be ignored.
OPENSSL_INIT_LOAD_CONFIG
With this option an OpenSSL configuration file will be automatically
loaded and used by calling OPENSSL_config(). This is a default
option. Note that in OpenSSL 1.1.1 this was the default for libssl
but not for libcrypto (see OPENSSL_init_ssl(3) for further details
about libssl initialisation). In OpenSSL 1.1.0 this was a
nondefault option for both libssl and libcrypto. See the
description of OPENSSL_INIT_new(), below.
OPENSSL_INIT_NO_LOAD_CONFIG
With this option the loading of OpenSSL configuration files will be
suppressed. It is the equivalent of calling OPENSSL_no_config().
This is not a default option.
OPENSSL_INIT_ASYNC
With this option the library with automatically initialise the
libcrypto async sub-library (see ASYNC_start_job(3)). This is a
default option.
OPENSSL_INIT_ENGINE_RDRAND
With this option the library will automatically load and initialise
the RDRAND engine (if available). This not a default option and is
deprecated in OpenSSL 3.0.
OPENSSL_INIT_ENGINE_DYNAMIC
With this option the library will automatically load and initialise
the dynamic engine. This not a default option and is deprecated in
OpenSSL 3.0.
OPENSSL_INIT_ENGINE_OPENSSL
With this option the library will automatically load and initialise
the openssl engine. This not a default option and is deprecated in
OpenSSL 3.0.
OPENSSL_INIT_ENGINE_CRYPTODEV
With this option the library will automatically load and initialise
the cryptodev engine (if available). This not a default option and
is deprecated in OpenSSL 3.0.
OPENSSL_INIT_ENGINE_CAPI
With this option the library will automatically load and initialise
the CAPI engine (if available). This not a default option and is
deprecated in OpenSSL 3.0.
OPENSSL_INIT_ENGINE_PADLOCK
With this option the library will automatically load and initialise
the padlock engine (if available). This not a default option and is
deprecated in OpenSSL 3.0.
OPENSSL_INIT_ENGINE_AFALG
With this option the library will automatically load and initialise
the AFALG engine. This not a default option and is deprecated in
OpenSSL 3.0.
OPENSSL_INIT_ENGINE_ALL_BUILTIN
With this option the library will automatically load and initialise
all the built in engines listed above with the exception of the
openssl and afalg engines. This not a default option and is
deprecated in OpenSSL 3.0.
OPENSSL_INIT_ATFORK
With this option the library will register its fork handlers. See
OPENSSL_fork_prepare(3) for details.
OPENSSL_INIT_NO_ATEXIT
By default OpenSSL will attempt to clean itself up when the process
exits via an "atexit" handler. Using this option suppresses that
behaviour. This means that the application will have to clean up
OpenSSL explicitly using OPENSSL_cleanup().
Multiple options may be combined together in a single call to
OPENSSL_init_crypto(). For example:
OPENSSL_init_crypto(OPENSSL_INIT_NO_ADD_ALL_CIPHERS
| OPENSSL_INIT_NO_ADD_ALL_DIGESTS, NULL);
The OPENSSL_cleanup() function deinitialises OpenSSL (both libcrypto and
libssl). All resources allocated by OpenSSL are freed. Typically there
should be no need to call this function directly as it is initiated
automatically on application exit. This is done via the standard C
library atexit() function. In the event that the application will close
in a manner that will not call the registered atexit() handlers then the
application should call OPENSSL_cleanup() directly. Developers of
libraries using OpenSSL are discouraged from calling this function and
should instead, typically, rely on auto-deinitialisation. This is to
avoid error conditions where both an application and a library it
depends on both use OpenSSL, and the library deinitialises it before the
application has finished using it.
Once OPENSSL_cleanup() has been called the library cannot be
reinitialised. Attempts to call OPENSSL_init_crypto() will fail and an
ERR_R_INIT_FAIL error will be added to the error stack. Note that
because initialisation has failed OpenSSL error strings will not be
available, only an error code. This code can be put through the openssl
errstr command line application to produce a human readable error (see
openssl-errstr(1)).
The OPENSSL_atexit() function enables the registration of a function to
be called during OPENSSL_cleanup(). Stop handlers are called after
deinitialisation of resources local to a thread, but before other
process wide resources are freed. In the event that multiple stop
handlers are registered, no guarantees are made about the order of
execution.
The OPENSSL_thread_stop_ex() function deallocates resources associated
with the current thread for the given OSSL_LIB_CTX ctx. The ctx
parameter can be NULL in which case the default OSSL_LIB_CTX is used.
Typically, this function will be called automatically by the library
when the thread exits as long as the OSSL_LIB_CTX has not been freed
before the thread exits. If OSSL_LIB_CTX_free() is called
OPENSSL_thread_stop_ex will be called automatically for the current
thread (but not any other threads that may have used this OSSL_LIB_CTX).
OPENSSL_thread_stop_ex should be called on all threads that will exit
after the OSSL_LIB_CTX is freed. Typically this is not necessary for
the default OSSL_LIB_CTX (because all resources are cleaned up on
library exit) except if thread local resources should be freed before
library exit, or under the circumstances described in the NOTES section
below.
OPENSSL_thread_stop() is the same as OPENSSL_thread_stop_ex() except
that the default OSSL_LIB_CTX is always used.
The OPENSSL_INIT_LOAD_CONFIG flag will load a configuration file, as
with CONF_modules_load_file(3) with NULL filename and application name
and the CONF_MFLAGS_IGNORE_MISSING_FILE, CONF_MFLAGS_IGNORE_RETURN_CODES
and CONF_MFLAGS_DEFAULT_SECTION flags. The filename, application name,
and flags can be customized by providing a non-null
OPENSSL_INIT_SETTINGS object. The object can be allocated via
OPENSSL_INIT_new(). The OPENSSL_INIT_set_config_filename() function can
be used to specify a nondefault filename, which is copied and need not
refer to persistent storage. Similarly,
OPENSSL_INIT_set_config_appname() can be used to specify a nondefault
application name. Finally, OPENSSL_INIT_set_file_flags can be used to
specify nondefault flags. If the CONF_MFLAGS_IGNORE_RETURN_CODES flag
is not included, any errors in the configuration file will cause an
error return from OPENSSL_init_crypto or indirectly OPENSSL_init_ssl(3).
The object can be released with OPENSSL_INIT_free() when done. If the
argument to OPENSSL_INIT_free() is NULL, nothing is done.
NOTES
Resources local to a thread are deallocated automatically when the
thread exits (e.g. in a pthreads environment, when pthread_exit() is
called). On Windows platforms this is done in response to a
DLL_THREAD_DETACH message being sent to the libcrypto32.dll entry point.
Some windows functions may cause threads to exit without sending this
message (for example ExitProcess()). If the application uses such
functions, then the application must free up OpenSSL resources directly
via a call to OPENSSL_thread_stop() on each thread. Similarly this
message will also not be sent if OpenSSL is linked statically, and
therefore applications using static linking should also call
OPENSSL_thread_stop() on each thread. Additionally if OpenSSL is loaded
dynamically via LoadLibrary() and the threads are not destroyed until
after FreeLibrary() is called then each thread should call
OPENSSL_thread_stop() prior to the FreeLibrary() call.
On Linux/Unix where OpenSSL has been loaded via dlopen() and the
application is multi-threaded and if dlclose() is subsequently called
prior to the threads being destroyed then OpenSSL will not be able to
deallocate resources associated with those threads. The application
should either call OPENSSL_thread_stop() on each thread prior to the
dlclose() call, or alternatively the original dlopen() call should use
the RTLD_NODELETE flag (where available on the platform).
RETURN VALUES
The functions OPENSSL_init_crypto, OPENSSL_atexit() and
OPENSSL_INIT_set_config_appname() return 1 on success or 0 on error.
SEE ALSO
OPENSSL_init_ssl(3)
HISTORY
The OPENSSL_init_crypto(), OPENSSL_cleanup(), OPENSSL_atexit(),
OPENSSL_thread_stop(), OPENSSL_INIT_new(),
OPENSSL_INIT_set_config_appname() and OPENSSL_INIT_free() functions were
added in OpenSSL 1.1.0.
COPYRIGHT
Copyright 2016-2024 The OpenSSL Project Authors. 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>.
3.5.7 2026-06-09 OPENSSL_INIT_CRYPTO(3SSL)
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