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
#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);
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.
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).
The functions OPENSSL_init_crypto,
OPENSSL_atexit() and
OPENSSL_INIT_set_config_appname() return 1 on success or 0 on error.
OPENSSL_init_ssl(3)
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 2016-2022 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>.