1=pod
2
3=head1 NAME
4
5RSA_get_ex_new_index, RSA_set_ex_data, RSA_get_ex_data - add application specific data to RSA structures
6
7=head1 SYNOPSIS
8
9 #include <openssl/rsa.h>
10
11 int RSA_get_ex_new_index(long argl, void *argp,
12		CRYPTO_EX_new *new_func,
13		CRYPTO_EX_dup *dup_func,
14		CRYPTO_EX_free *free_func);
15
16 int RSA_set_ex_data(RSA *r, int idx, void *arg);
17
18 void *RSA_get_ex_data(RSA *r, int idx);
19
20 typedef int CRYPTO_EX_new(void *parent, void *ptr, CRYPTO_EX_DATA *ad,
21                           int idx, long argl, void *argp);
22 typedef void CRYPTO_EX_free(void *parent, void *ptr, CRYPTO_EX_DATA *ad,
23                             int idx, long argl, void *argp);
24 typedef int CRYPTO_EX_dup(CRYPTO_EX_DATA *to, CRYPTO_EX_DATA *from, void *from_d,
25                           int idx, long argl, void *argp);
26
27=head1 DESCRIPTION
28
29Several OpenSSL structures can have application specific data attached to them.
30This has several potential uses, it can be used to cache data associated with
31a structure (for example the hash of some part of the structure) or some
32additional data (for example a handle to the data in an external library).
33
34Since the application data can be anything at all it is passed and retrieved
35as a B<void *> type.
36
37The B<RSA_get_ex_new_index()> function is initially called to "register" some
38new application specific data. It takes three optional function pointers which
39are called when the parent structure (in this case an RSA structure) is
40initially created, when it is copied and when it is freed up. If any or all of
41these function pointer arguments are not used they should be set to NULL. The
42precise manner in which these function pointers are called is described in more
43detail below. B<RSA_get_ex_new_index()> also takes additional long and pointer
44parameters which will be passed to the supplied functions but which otherwise
45have no special meaning. It returns an B<index> which should be stored
46(typically in a static variable) and passed used in the B<idx> parameter in
47the remaining functions. Each successful call to B<RSA_get_ex_new_index()>
48will return an index greater than any previously returned, this is important
49because the optional functions are called in order of increasing index value.
50
51B<RSA_set_ex_data()> is used to set application specific data, the data is
52supplied in the B<arg> parameter and its precise meaning is up to the
53application.
54
55B<RSA_get_ex_data()> is used to retrieve application specific data. The data
56is returned to the application, this will be the same value as supplied to
57a previous B<RSA_set_ex_data()> call.
58
59B<new_func()> is called when a structure is initially allocated (for example
60with B<RSA_new()>. The parent structure members will not have any meaningful
61values at this point. This function will typically be used to allocate any
62application specific structure.
63
64B<free_func()> is called when a structure is being freed up. The dynamic parent
65structure members should not be accessed because they will be freed up when
66this function is called.
67
68B<new_func()> and B<free_func()> take the same parameters. B<parent> is a
69pointer to the parent RSA structure. B<ptr> is a the application specific data
70(this wont be of much use in B<new_func()>. B<ad> is a pointer to the
71B<CRYPTO_EX_DATA> structure from the parent RSA structure: the functions
72B<CRYPTO_get_ex_data()> and B<CRYPTO_set_ex_data()> can be called to manipulate
73it. The B<idx> parameter is the index: this will be the same value returned by
74B<RSA_get_ex_new_index()> when the functions were initially registered. Finally
75the B<argl> and B<argp> parameters are the values originally passed to the same
76corresponding parameters when B<RSA_get_ex_new_index()> was called.
77
78B<dup_func()> is called when a structure is being copied. Pointers to the
79destination and source B<CRYPTO_EX_DATA> structures are passed in the B<to> and
80B<from> parameters respectively. The B<from_d> parameter is passed a pointer to
81the source application data when the function is called, when the function returns
82the value is copied to the destination: the application can thus modify the data
83pointed to by B<from_d> and have different values in the source and destination.
84The B<idx>, B<argl> and B<argp> parameters are the same as those in B<new_func()>
85and B<free_func()>.
86
87=head1 RETURN VALUES
88
89B<RSA_get_ex_new_index()> returns a new index or -1 on failure (note 0 is a valid
90index value).
91
92B<RSA_set_ex_data()> returns 1 on success or 0 on failure.
93
94B<RSA_get_ex_data()> returns the application data or 0 on failure. 0 may also
95be valid application data but currently it can only fail if given an invalid B<idx>
96parameter.
97
98B<new_func()> and B<dup_func()> should return 0 for failure and 1 for success.
99
100On failure an error code can be obtained from L<ERR_get_error(3)|ERR_get_error(3)>.
101
102=head1 BUGS
103
104B<dup_func()> is currently never called.
105
106The return value of B<new_func()> is ignored.
107
108The B<new_func()> function isn't very useful because no meaningful values are
109present in the parent RSA structure when it is called.
110
111=head1 SEE ALSO
112
113L<rsa(3)|rsa(3)>, L<CRYPTO_set_ex_data(3)|CRYPTO_set_ex_data(3)>
114
115=head1 HISTORY
116
117RSA_get_ex_new_index(), RSA_set_ex_data() and RSA_get_ex_data() are
118available since SSLeay 0.9.0.
119
120=cut
121