NAME¶
RSA_get_ex_new_index, RSA_set_ex_data, RSA_get_ex_data - add application
specific data to RSA structures
SYNOPSIS¶
#include <openssl/rsa.h>
int RSA_get_ex_new_index(long argl, void *argp,
CRYPTO_EX_new *new_func,
CRYPTO_EX_dup *dup_func,
CRYPTO_EX_free *free_func);
int RSA_set_ex_data(RSA *r, int idx, void *arg);
void *RSA_get_ex_data(RSA *r, int idx);
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, CRYPTO_EX_DATA *from, void *from_d,
int idx, long argl, void *argp);
DESCRIPTION¶
Several OpenSSL structures can have application specific data attached to them.
This has several potential uses, it can be used to cache data associated with
a structure (for example the hash of some part of the structure) or some
additional data (for example a handle to the data in an external library).
Since the application data can be anything at all it is passed and retrieved as
a
void * type.
The
RSA_get_ex_new_index() function is initially
called to "register" some new application specific data. It takes
three optional function pointers which are called when the parent structure
(in this case an RSA structure) is initially created, when it is copied and
when it is freed up. If any or all of these function pointer arguments are not
used they should be set to NULL. The precise manner in which these function
pointers are called is described in more detail below.
RSA_get_ex_new_index() also takes additional long
and pointer parameters which will be passed to the supplied functions but
which otherwise have no special meaning. It returns an
index which
should be stored (typically in a static variable) and passed used in the
idx parameter in the remaining functions. Each successful call to
RSA_get_ex_new_index() will return an index
greater than any previously returned, this is important because the optional
functions are called in order of increasing index value.
RSA_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.
RSA_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
RSA_set_ex_data()
call.
new_func() is called when a structure is initially
allocated (for example with
RSA_new(). The parent
structure members will not have any meaningful values at this point. This
function will typically be used to allocate any application specific
structure.
free_func() is called when a structure is being
freed up. The dynamic parent structure members should not be accessed because
they will be freed up when this function is called.
new_func() and
free_func() take the same parameters.
parent is a pointer to the parent RSA structure.
ptr is a the
application specific data (this wont be of much use in
new_func() .
ad is a pointer to the
CRYPTO_EX_DATA structure from the parent RSA structure: the functions
CRYPTO_get_ex_data() and
CRYPTO_set_ex_data() can be called to manipulate
it. The
idx parameter is the index: this will be the same value
returned by
RSA_get_ex_new_index() when the
functions were initially registered. Finally the
argl and
argp
parameters are the values originally passed to the same corresponding
parameters when
RSA_get_ex_new_index() was called.
dup_func() is called when a structure is being
copied. Pointers to the destination and source
CRYPTO_EX_DATA
structures are passed in the
to and
from parameters
respectively. The
from_d parameter is passed a pointer to the source
application data when the function is called, when the function returns the
value is copied to the destination: the application can thus modify the data
pointed to by
from_d and have different values in the source and
destination. The
idx,
argl and
argp parameters are the
same as those in
new_func() and
free_func() .
RETURN VALUES¶
RSA_get_ex_new_index() returns a new index or -1 on
failure (note 0 is a valid index value).
RSA_set_ex_data() returns 1 on success or 0 on
failure.
RSA_get_ex_data() returns the application data or 0
on failure. 0 may also be valid application data but currently it can only
fail if given an invalid
idx parameter.
new_func() and
dup_func() should return 0 for failure and 1 for
success.
On failure an error code can be obtained from
ERR_get_error(3).
BUGS¶
dup_func() is currently never called.
The return value of
new_func() is ignored.
The
new_func() function isn't very useful because no
meaningful values are present in the parent RSA structure when it is called.
SEE ALSO¶
rsa(3),
CRYPTO_set_ex_data(3)
HISTORY¶
RSA_get_ex_new_index(),
RSA_set_ex_data() and
RSA_get_ex_data() are available since SSLeay 0.9.0.