mirror of
https://github.com/openssl/openssl.git
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224 lines
8.7 KiB
Plaintext
224 lines
8.7 KiB
Plaintext
=pod
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=head1 NAME
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OPENSSL_init_crypto, OPENSSL_cleanup,
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OPENSSL_atexit, OPENSSL_thread_stop - OpenSSL
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initialisation and deinitialisation functions
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=head1 SYNOPSIS
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#include <openssl/crypto.h>
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void OPENSSL_cleanup(void);
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int OPENSSL_init_crypto(uint64_t opts, const OPENSSL_INIT_SETTINGS *settings);
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int OPENSSL_atexit(void (*handler)(void));
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void OPENSSL_thread_stop(void);
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OPENSSL_INIT_SETTINGS *OPENSSL_init_new(void);
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OPENSSL_INIT_set_config_filename(OPENSSL_INIT_SETTINGS *init, const char* name);
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OPENSSL_INIT_free(OPENSSL_INIT_SETTINGS *init);
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=head1 DESCRIPTION
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During normal operation OpenSSL (libcrypto) will allocate various resources at
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start up that must, subsequently, be freed on close down of the library.
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Additionally some resources are allocated on a per thread basis (if the
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application is multi-threaded), and these resources must be freed prior to the
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thread closing.
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As of version 1.1.0 OpenSSL will automatically allocate all resources that it
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needs so no explicit initialisation is required. Similarly it will also
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automatically deinitialise as required.
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However, there way be situations when explicit initialisation is desirable or
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needed, for example when some non-default initialisation is required. The
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function OPENSSL_init_crypto() can be used for this purpose for
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libcrypto (see also L<OPENSSL_init_ssl(3)> for the libssl
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equivalent).
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Numerous internal OpenSSL functions call OPENSSL_init_crypto().
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Therefore, in order to perform non-default initialisation,
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OPENSSL_init_crypto() MUST be called by application code prior to
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any other OpenSSL function calls.
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The B<opts> parameter specifies which aspects of libcrypto should be
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initialised. Valid options are:
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=over 4
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=item OPENSSL_INIT_NO_LOAD_CRYPTO_STRINGS
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Suppress automatic loading of the libcrypto error strings. This option is
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not a default option. Once selected subsequent calls to
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OPENSSL_init_crypto() with the option
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B<OPENSSL_INIT_LOAD_CRYPTO_STRINGS> will be ignored.
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=item OPENSSL_INIT_LOAD_CRYPTO_STRINGS
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Automatic loading of the libcrypto error strings. With this option the
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library will automatically load the libcrypto error strings.
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This option is a default option. Once selected subsequent calls to
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OPENSSL_init_crypto() with the option
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B<OPENSSL_INIT_NO_LOAD_CRYPTO_STRINGS> will be ignored.
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=item OPENSSL_INIT_ADD_ALL_CIPHERS
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With this option the library will automatically load and make available all
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libcrypto ciphers. This option is a default option. Once selected subsequent
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calls to OPENSSL_init_crypto() with the option
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B<OPENSSL_INIT_NO_ADD_ALL_CIPHERS> will be ignored.
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=item OPENSSL_INIT_ADD_ALL_DIGESTS
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With this option the library will automatically load and make available all
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libcrypto digests. This option is a default option. Once selected subsequent
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calls to OPENSSL_init_crypto() with the option
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B<OPENSSL_INIT_NO_ADD_ALL_CIPHERS> will be ignored.
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=item OPENSSL_INIT_NO_ADD_ALL_CIPHERS
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With this option the library will suppress automatic loading of libcrypto
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ciphers. This option is not a default option. Once selected subsequent
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calls to OPENSSL_init_crypto() with the option
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B<OPENSSL_INIT_ADD_ALL_CIPHERS> will be ignored.
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=item OPENSSL_INIT_NO_ADD_ALL_DIGESTS
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With this option the library will suppress automatic loading of libcrypto
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digests. This option is not a default option. Once selected subsequent
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calls to OPENSSL_init_crypto() with the option
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B<OPENSSL_INIT_ADD_ALL_DIGESTS> will be ignored.
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=item OPENSSL_INIT_LOAD_CONFIG
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With this option an OpenSSL configuration file will be automatically loaded and
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used by calling OPENSSL_config(). This is not a default option.
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See the description of OPENSSL_init_new(), below.
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=item OPENSSL_INIT_NO_LOAD_CONFIG
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With this option the loading of OpenSSL configuration files will be suppressed.
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It is the equivalent of calling OPENSSL_no_config(). This is not a default
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option.
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=item OPENSSL_INIT_ASYNC
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With this option the library with automatically initialise the libcrypto async
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sub-library (see L<ASYNC_start_job(3)>). This is a default option.
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=item OPENSSL_INIT_ENGINE_RDRAND
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With this option the library will automatically load and initialise the
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RDRAND engine (if available). This not a default option.
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=item OPENSSL_INIT_ENGINE_DYNAMIC
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With this option the library will automatically load and initialise the
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dynamic engine. This not a default option.
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=item OPENSSL_INIT_ENGINE_OPENSSL
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With this option the library will automatically load and initialise the
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openssl engine. This not a default option.
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=item OPENSSL_INIT_ENGINE_CRYPTODEV
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With this option the library will automatically load and initialise the
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cryptodev engine (if available). This not a default option.
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=item OPENSSL_INIT_ENGINE_CAPI
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With this option the library will automatically load and initialise the
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CAPI engine (if available). This not a default option.
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=item OPENSSL_INIT_ENGINE_PADLOCK
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With this option the library will automatically load and initialise the
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padlock engine (if available). This not a default option.
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=item OPENSSL_INIT_ENGINE_DASYNC
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With this option the library will automatically load and initialise the
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DASYNC engine. This not a default option.
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=item OPENSSL_INIT_ENGINE_ALL_BUILTIN
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With this option the library will automatically load and initialise all the
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built in engines listed above with the exception of the openssl and dasync
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engines. This not a default option.
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=back
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Multiple options may be combined together in a single call to
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OPENSSL_init_crypto(). For example:
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OPENSSL_init_crypto(OPENSSL_INIT_NO_ADD_ALL_CIPHERS
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| OPENSSL_INIT_NO_ADD_ALL_DIGESTS, NULL);
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The OPENSSL_cleanup() function deinitialises OpenSSL (both libcrypto
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and libssl). All resources allocated by OpenSSL are freed. Typically there
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should be no need to call this function directly as it is initiated
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automatically on application exit. This is done via the standard C library
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L<atexit(3)> function. In the event that the application will close in a manner
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that will not call the registered atexit() handlers then the application should
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call OPENSSL_cleanup() directly. Developers of libraries using OpenSSL
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are discouraged from calling this function and should instead, typically, rely
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on auto-deinitialisation. This is to avoid error conditions where both an
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application and a library it depends on both use OpenSSL, and the library
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deinitialises it before the application has finished using it.
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Once OPENSSL_cleanup() has been called the library cannot be reinitialised.
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Attempts to call OPENSSL_init_crypto() will fail and an ERR_R_INIT_FAIL error
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will be added to the error stack. Note that because initialisation has failed
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OpenSSL error strings will not be available, only an error code. This code can
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be put through the openssl errstr command line application to produce a human
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readable error (see L<errstr(1)>).
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The OPENSSL_atexit() function enables the registration of a
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function to be called during OPENSSL_cleanup(). Stop handlers are
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called after deinitialisation of resources local to a thread, but before other
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process wide resources are freed. In the event that multiple stop handlers are
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registered, no guarantees are made about the order of execution.
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The OPENSSL_thread_stop() function deallocates resources associated
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with the current thread. Typically this function will be called automatically by
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the library when the thread exits. This should only be called directly if
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resources should be freed at an earlier time, or under the circumstances
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described in the NOTES section below.
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The B<OPENSSL_INIT_LOAD_CONFIG> flag will load a default configuration
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file. To specify a different file, an B<OPENSSL_INIT_SETTINGS> must
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be created and used. The routines
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OPENSSL_init_new() and OPENSSL_INIT_set_config_filename() can be used to
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allocate the object and set the configuration filename, and then the
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object can be released with OPENSSL_INIT_free() when done.
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=head1 NOTES
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Resources local to a thread are deallocated automatically when the thread exits
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(e.g. in a pthreads environment, when pthread_exit() is called). On Windows
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platforms this is done in response to a DLL_THREAD_DETACH message being sent to
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the libcrypto32.dll entry point. Some windows functions may cause threads to exit
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without sending this message (for example ExitProcess()). If the application
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uses such functions, then the application must free up OpenSSL resources
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directly via a call to OPENSSL_thread_stop(). Similarly this message will
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also not be sent if OpenSSL is linked statically, and therefore applications
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using static linking should also call OPENSSL_thread_stop().
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=head1 RETURN VALUES
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The functions OPENSSL_init_crypto and OPENSSL_atexit() returns 1 on success or
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0 on error.
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=head1 SEE ALSO
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L<OPENSSL_init_ssl(3)>
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=head1 HISTORY
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The OPENSSL_init_crypto(), OPENSSL_cleanup(), OPENSSL_atexit(),
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and OPENSSL_thread_stop() functions were added in OpenSSL 1.1.0.
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=cut
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