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NAMECRYPTO_EX_new, CRYPTO_EX_free, CRYPTO_EX_dup, CRYPTO_free_ex_index, CRYPTO_get_ex_new_index, CRYPTO_set_ex_data, CRYPTO_get_ex_data, CRYPTO_free_ex_data, CRYPTO_new_ex_data - functions supporting application-specific data
#include <openssl/crypto.h> int CRYPTO_get_ex_new_index(int class_index, long argl, void *argp, CRYPTO_EX_new *new_func, CRYPTO_EX_dup *dup_func, CRYPTO_EX_free *free_func); typedef void CRYPTO_EX_new(void *parent, void *ptr, CRYPTO_EX_DATA *ad, int idx, long argl, void *argp); typedef void CRYPTO_EX_free(void *parent, void *ptr, CRYPTO_EX_DATA *ad, int idx, long argl, void *argp); typedef int CRYPTO_EX_dup(CRYPTO_EX_DATA *to, const CRYPTO_EX_DATA *from, void *from_d, int idx, long argl, void *argp); int CRYPTO_new_ex_data(int class_index, void *obj, CRYPTO_EX_DATA *ad) int CRYPTO_set_ex_data(CRYPTO_EX_DATA *r, int idx, void *arg); void *CRYPTO_get_ex_data(CRYPTO_EX_DATA *r, int idx); void CRYPTO_free_ex_data(int class_index, void *obj, CRYPTO_EX_DATA *r); int CRYPTO_free_ex_index(int class_index, int idx);
DESCRIPTIONSeveral OpenSSL structures can have application-specific data attached to them, known as ``exdata.'' The specific structures are:
SSL SSL_CTX SSL_SESSION X509 X509_STORE X509_STORE_CTX DH DSA EC_KEY RSA ENGINE UI UI_METHOD BIO
Each is identified by an CRYPTO_EX_INDEX_xxx define in the crypto.h header file. In addition,
Exdata types are identified by an index, an integer guaranteed to be unique within structures for the lifetime of the program. Applications using exdata typically call CRYPTO_get_ex_new_index at startup, and store the result in a global variable, or write a wrapper function to provide lazy evaluation. The class_index should be one of the CRYPTO_EX_INDEX_xxx values. The argl and argp parameters are saved to be passed to the callbacks but are otherwise not used. In order to transparently manipulate exdata, three callbacks must be provided. The semantics of those callbacks are described below.
When copying or releasing objects with exdata, the callback functions are called in increasing order of their index value.
If a dynamic library can be unloaded, it should call CRYPTO_free_ex_index() when this is done. This will replace the callbacks with no-ops so that applications don't crash. Any existing exdata will be leaked.
To set or get the exdata on an object, the appropriate type-specific routine must be used. This is because the containing structure is opaque and the
When setting exdata, the pointer specified with a particular index is saved, and returned on a subsequent ``get'' call. If the application is going to release the data, it must make sure to set a
The function CRYPTO_free_ex_data is used to free all exdata attached to a structure. The appropriate type-specific routine must be used. The class_index identifies the structure type, the obj is be the pointer to the actual structure, and r is a pointer to the structure's exdata field.
Callback FunctionsThis section describes how the callback functions are used. Applications that are defining their own exdata using
When a structure is initially allocated (such as RSA_new()) then the new_func() is called for every defined index. There is no requirement that the entire parent, or containing, structure has been set up. The new_func() is typically used only to allocate memory to store the exdata, and perhaps an ``initialized'' flag within that memory. The exdata value should be set by calling CRYPTO_set_ex_data().
When a structure is free'd (such as SSL_CTX_free()) then the free_func() is called for every defined index. Again, the state of the parent structure is not guaranteed. The free_func() may be called with a
Both new_func() and free_func() take the same parameters. The parent is the pointer to the structure that contains the exdata. The ptr is the current exdata item; for new_func() this will typically be
dup_func() is called when a structure is being copied. This is only done for
RETURN VALUESCRYPTO_get_ex_new_index() returns a new index or -1 on failure; the value 0 is reserved for the legacy ``app_data''
CRYPTO_free_ex_index() and CRYPTO_set_ex_data() return 1 on success or 0 on failure.
CRYPTO_get_ex_data() returns the application data or
dup_func() should return 0 for failure and 1 for success.
COPYRIGHTCopyright 2015-2017 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