OPENSSL_INIT_new, OPENSSL_INIT_set_config_appname, OPENSSL_INIT_free,
OPENSSL_init_crypto, OPENSSL_cleanup, OPENSSL_atexit, 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(void);
OPENSSL_INIT_SETTINGS *OPENSSL_INIT_new(void);
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 way be situations when explicit initialisation is desirable or
needed, for example when some non-default 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 non-default 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_CIPHERS 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 not a default
option for libcrypto. From OpenSSL 1.1.1 this is a default option for
libssl (see OPENSSL_init_ssl(3) for further details about libssl
initialisation). 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.
- OPENSSL_INIT_ENGINE_DYNAMIC
- With this option the library will automatically load and initialise the
dynamic engine. This not a default option.
- OPENSSL_INIT_ENGINE_OPENSSL
- With this option the library will automatically load and initialise the
openssl engine. This not a default option.
- OPENSSL_INIT_ENGINE_CRYPTODEV
- With this option the library will automatically load and initialise the
cryptodev engine (if available). This not a default option.
- OPENSSL_INIT_ENGINE_CAPI
- With this option the library will automatically load and initialise the
CAPI engine (if available). This not a default option.
- OPENSSL_INIT_ENGINE_PADLOCK
- With this option the library will automatically load and initialise the
padlock engine (if available). This not a default option.
- OPENSSL_INIT_ENGINE_AFALG
- With this option the library will automatically load and initialise the
AFALG engine. This not a default option.
- 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.
- OPENSSL_INIT_ATFORK
- With this option the library will register its fork handlers. See
OPENSSL_fork_prepare(3) for details.
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
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() function deallocates resources associated with
the current thread. Typically this function will be called automatically by
the library when the thread exits. This should only be called directly if
resources should be freed at an earlier time, or under the circumstances
described in the NOTES section below.
The
OPENSSL_INIT_LOAD_CONFIG flag will load a default configuration file.
For optional configuration file settings, an
OPENSSL_INIT_SETTINGS must
be created and used. The routines
OPENSSL_init_new() and
OPENSSL_INIT_set_config_appname() can be used to allocate the object
and set the application name, and then 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 2016-2018 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (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>.