5 RSA_get_ex_new_index, RSA_set_ex_data, RSA_get_ex_data - add application specific data to RSA structures
9 #include <openssl/rsa.h>
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);
16 int RSA_set_ex_data(RSA *r, int idx, void *arg);
18 void *RSA_get_ex_data(RSA *r, int idx);
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);
29 Several OpenSSL structures can have application specific data attached to them.
30 This has several potential uses, it can be used to cache data associated with
31 a structure (for example the hash of some part of the structure) or some
32 additional data (for example a handle to the data in an external library).
34 Since the application data can be anything at all it is passed and retrieved
37 The RSA_get_ex_new_index() function is initially called to "register" some
38 new application specific data. It takes three optional function pointers which
39 are called when the parent structure (in this case an RSA structure) is
40 initially created, when it is copied and when it is freed up. If any or all of
41 these function pointer arguments are not used they should be set to NULL. The
42 precise manner in which these function pointers are called is described in more
43 detail below. RSA_get_ex_new_index() also takes additional long and pointer
44 parameters which will be passed to the supplied functions but which otherwise
45 have 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
47 the remaining functions. Each successful call to RSA_get_ex_new_index()
48 will return an index greater than any previously returned, this is important
49 because the optional functions are called in order of increasing index value.
51 RSA_set_ex_data() is used to set application specific data, the data is
52 supplied in the B<arg> parameter and its precise meaning is up to the
55 RSA_get_ex_data() is used to retrieve application specific data. The data
56 is returned to the application, this will be the same value as supplied to
57 a previous RSA_set_ex_data() call.
59 new_func() is called when a structure is initially allocated (for example
60 with RSA_new(). The parent structure members will not have any meaningful
61 values at this point. This function will typically be used to allocate any
62 application specific structure.
64 free_func() is called when a structure is being freed up. The dynamic parent
65 structure members should not be accessed because they will be freed up when
66 this function is called.
68 new_func() and free_func() take the same parameters. B<parent> is a
69 pointer to the parent RSA structure. B<ptr> is a the application specific data
70 (this wont be of much use in new_func(). B<ad> is a pointer to the
71 B<CRYPTO_EX_DATA> structure from the parent RSA structure: the functions
72 CRYPTO_get_ex_data() and CRYPTO_set_ex_data() can be called to manipulate
73 it. The B<idx> parameter is the index: this will be the same value returned by
74 RSA_get_ex_new_index() when the functions were initially registered. Finally
75 the B<argl> and B<argp> parameters are the values originally passed to the same
76 corresponding parameters when RSA_get_ex_new_index() was called.
78 dup_func() is called when a structure is being copied. Pointers to the
79 destination and source B<CRYPTO_EX_DATA> structures are passed in the B<to> and
80 B<from> parameters respectively. The B<from_d> parameter is passed a pointer to
81 the source application data when the function is called, when the function returns
82 the value is copied to the destination: the application can thus modify the data
83 pointed to by B<from_d> and have different values in the source and destination.
84 The B<idx>, B<argl> and B<argp> parameters are the same as those in new_func()
89 RSA_get_ex_new_index() returns a new index or -1 on failure (note 0 is a valid
92 RSA_set_ex_data() returns 1 on success or 0 on failure.
94 RSA_get_ex_data() returns the application data or 0 on failure. 0 may also
95 be valid application data but currently it can only fail if given an invalid B<idx>
98 new_func() and dup_func() should return 0 for failure and 1 for success.
100 On failure an error code can be obtained from L<ERR_get_error(3)>.
104 dup_func() is currently never called.
106 The return value of new_func() is ignored.
108 The new_func() function isn't very useful because no meaningful values are
109 present in the parent RSA structure when it is called.
113 L<rsa(3)>, L<CRYPTO_set_ex_data(3)>