Ubuntu Manpage: OPENSSL_INIT_new, OPENSSL_INIT_set_config_filename, OPENSSL_INIT_set_config

Provided by: libssl-doc_3.0.13-0ubuntu3.4_all

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.

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.

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 2016-2022 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>.