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 new_func(void *parent, void *ptr, CRYPTO_EX_DATA *ad, 21 int idx, long argl, void *argp); 22 typedef void free_func(void *parent, void *ptr, CRYPTO_EX_DATA *ad, 23 int idx, long argl, void *argp); 24 typedef int dup_func(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