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121 lines
5.1 KiB
Plaintext
121 lines
5.1 KiB
Plaintext
=pod
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=head1 NAME
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RSA_get_ex_new_index, RSA_set_ex_data, RSA_get_ex_data - add application specific data to RSA structures
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=head1 SYNOPSIS
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#include <openssl/rsa.h>
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int RSA_get_ex_new_index(long argl, void *argp,
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CRYPTO_EX_new *new_func,
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CRYPTO_EX_dup *dup_func,
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CRYPTO_EX_free *free_func);
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int RSA_set_ex_data(RSA *r, int idx, void *arg);
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void *RSA_get_ex_data(RSA *r, int idx);
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typedef int CRYPTO_EX_new(void *parent, void *ptr, CRYPTO_EX_DATA *ad,
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int idx, long argl, void *argp);
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typedef void CRYPTO_EX_free(void *parent, void *ptr, CRYPTO_EX_DATA *ad,
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int idx, long argl, void *argp);
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typedef int CRYPTO_EX_dup(CRYPTO_EX_DATA *to, CRYPTO_EX_DATA *from, void *from_d,
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int idx, long argl, void *argp);
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=head1 DESCRIPTION
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Several OpenSSL structures can have application specific data attached to them.
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This has several potential uses, it can be used to cache data associated with
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a structure (for example the hash of some part of the structure) or some
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additional data (for example a handle to the data in an external library).
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Since the application data can be anything at all it is passed and retrieved
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as a B<void *> type.
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The B<RSA_get_ex_new_index()> function is initially called to "register" some
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new application specific data. It takes three optional function pointers which
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are called when the parent structure (in this case an RSA structure) is
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initially created, when it is copied and when it is freed up. If any or all of
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these function pointer arguments are not used they should be set to NULL. The
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precise manner in which these function pointers are called is described in more
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detail below. B<RSA_get_ex_new_index()> also takes additional long and pointer
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parameters which will be passed to the supplied functions but which otherwise
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have no special meaning. It returns an B<index> which should be stored
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(typically in a static variable) and passed used in the B<idx> parameter in
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the remaining functions. Each successful call to B<RSA_get_ex_new_index()>
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will return an index greater than any previously returned, this is important
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because the optional functions are called in order of increasing index value.
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B<RSA_set_ex_data()> is used to set application specific data, the data is
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supplied in the B<arg> parameter and its precise meaning is up to the
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application.
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B<RSA_get_ex_data()> is used to retrieve application specific data. The data
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is returned to the application, this will be the same value as supplied to
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a previous B<RSA_set_ex_data()> call.
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B<new_func()> is called when a structure is initially allocated (for example
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with B<RSA_new()>. The parent structure members will not have any meaningful
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values at this point. This function will typically be used to allocate any
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application specific structure.
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B<free_func()> is called when a structure is being freed up. The dynamic parent
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structure members should not be accessed because they will be freed up when
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this function is called.
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B<new_func()> and B<free_func()> take the same parameters. B<parent> is a
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pointer to the parent RSA structure. B<ptr> is a the application specific data
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(this wont be of much use in B<new_func()>. B<ad> is a pointer to the
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B<CRYPTO_EX_DATA> structure from the parent RSA structure: the functions
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B<CRYPTO_get_ex_data()> and B<CRYPTO_set_ex_data()> can be called to manipulate
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it. The B<idx> parameter is the index: this will be the same value returned by
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B<RSA_get_ex_new_index()> when the functions were initially registered. Finally
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the B<argl> and B<argp> parameters are the values originally passed to the same
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corresponding parameters when B<RSA_get_ex_new_index()> was called.
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B<dup_func()> is called when a structure is being copied. Pointers to the
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destination and source B<CRYPTO_EX_DATA> structures are passed in the B<to> and
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B<from> parameters respectively. The B<from_d> parameter is passed a pointer to
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the source application data when the function is called, when the function returns
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the value is copied to the destination: the application can thus modify the data
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pointed to by B<from_d> and have different values in the source and destination.
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The B<idx>, B<argl> and B<argp> parameters are the same as those in B<new_func()>
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and B<free_func()>.
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=head1 RETURN VALUES
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B<RSA_get_ex_new_index()> returns a new index or -1 on failure (note 0 is a valid
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index value).
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B<RSA_set_ex_data()> returns 1 on success or 0 on failure.
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B<RSA_get_ex_data()> returns the application data or 0 on failure. 0 may also
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be valid application data but currently it can only fail if given an invalid B<idx>
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parameter.
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B<new_func()> and B<dup_func()> should return 0 for failure and 1 for success.
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On failure an error code can be obtained from L<ERR_get_error(3)|ERR_get_error(3)>.
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=head1 BUGS
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B<dup_func()> is currently never called.
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The return value of B<new_func()> is ignored.
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The B<new_func()> function isn't very useful because no meaningful values are
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present in the parent RSA structure when it is called.
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=head1 SEE ALSO
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L<rsa(3)|rsa(3)>, L<CRYPTO_set_ex_data(3)|CRYPTO_set_ex_data(3)>
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=head1 HISTORY
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RSA_get_ex_new_index(), RSA_set_ex_data() and RSA_get_ex_data() are
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available since SSLeay 0.9.0.
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=cut
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