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CRYPTO_SET_EX_DATA(3) | Library Functions Manual | CRYPTO_SET_EX_DATA(3) |
NAME
CRYPTO_EX_new
,
CRYPTO_EX_free
,
CRYPTO_EX_dup
,
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
SYNOPSIS
#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 int
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);
DESCRIPTION
Several OpenSSL structures can have application specific data attached to them, known as "exdata". The specific structures are:BIO DH DSA EC_KEY ECDH ECDSA ENGINE RSA SSL SSL_CTX SSL_SESSION UI X509 X509_STORE X509_STORE_CTX
CRYPTO_EX_INDEX_*
constant defined in the
<openssl/crypto.h>
header file.
The API described here is used by OpenSSL to manipulate exdata for specific
structures. Since the application data can be anything at all, it is passed
and retrieved as a void * type.
The CRYPTO_EX_DATA type is opaque. To
initialize the exdata part of a structure, call
CRYPTO_new_ex_data
().
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_*
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.
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
CRYPTO_EX_DATA field is not accessible. In
both APIs, the idx parameter should be an
already-created index value.
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
NULL
value at the index, to avoid likely
double-free crashes.
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 a pointer to the
actual structure, and r is a pointer to the
structure's exdata field.
The callback functions are used as follows.
When a structure is initially allocated (such as by
RSA_new(3)), then
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 by
SSL_CTX_free(3)),
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
NULL
pointer.
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 NULL
. The
r parameter is a pointer to the exdata field
of the object. The idx is the index and is
the value returned when the callbacks were initially registered via
CRYPTO_get_ex_new_index
() and can be used
if the same callback handles different types of exdata.
dup_func is called when a structure is being
copied. This is only done for SSL and
SSL_SESSION objects. The
to and from
parameters are pointers to the destination and source
CRYPTO_EX_DATA structures, respectively. The
from_d parameter is a pointer to the source
exdata. When dup_func returns, the value in
from_d is copied to the destination ex_data.
If the pointer contained in from_d is not
modified by the dup_func, then both
to and from
will point to the same data. The idx,
argl and
argp parameters are as described for the
other two callbacks.
CRYPTO_set_ex_data
() is used to set
application specific data. The data is supplied in the
arg parameter and its precise meaning is up
to the application.
CRYPTO_get_ex_data
() is used to retrieve
application specific data. The data is returned to the application; this will
be the same value as supplied to a previous
CRYPTO_set_ex_data
() call.
RETURN VALUES
CRYPTO_get_ex_new_index
() returns a new index
or -1 on failure; the value 0 is reserved for the legacy "app_data"
APIs.
CRYPTO_set_ex_data
() returns 1 on success or
0 on failure.
CRYPTO_get_ex_data
() returns the application
data or NULL
on failure; note that
NULL
may be a valid value.
dup_func should return 0 for failure and 1 for
success.
On failure an error code can be obtained from
ERR_get_error(3).
SEE ALSO
BIO_get_ex_new_index(3), DH_get_ex_new_index(3), DSA_get_ex_new_index(3), RSA_get_ex_new_index(3), SSL_CTX_get_ex_new_index(3), SSL_get_ex_new_index(3), SSL_SESSION_get_ex_new_index(3), X509_STORE_CTX_get_ex_new_index(3), X509_STORE_get_ex_new_index(3)HISTORY
CRYPTO_get_ex_new_index
(),
CRYPTO_set_ex_data
(),
CRYPTO_get_ex_data
(),
CRYPTO_free_ex_data
(), and
CRYPTO_new_ex_data
() first appeared in
SSLeay 0.9.0 and have been available since OpenBSD
2.4.
CRYPTO_EX_new
(),
CRYPTO_EX_free
(), and
CRYPTO_EX_dup
() first appeared in OpenSSL
0.9.5 and have been available since OpenBSD 2.7.March 31, 2022 | Debian |