4746f25ac6
[skip ci] Reviewed-by: Matt Caswell <matt@openssl.org> (Merged from https://github.com/openssl/openssl/pull/7829)
240 lines
6.5 KiB
Text
240 lines
6.5 KiB
Text
=pod
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=head1 NAME
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BIO_set_callback_ex, BIO_get_callback_ex, BIO_set_callback, BIO_get_callback,
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BIO_set_callback_arg, BIO_get_callback_arg, BIO_debug_callback,
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BIO_callback_fn_ex, BIO_callback_fn
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- BIO callback functions
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=head1 SYNOPSIS
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#include <openssl/bio.h>
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typedef long (*BIO_callback_fn_ex)(BIO *b, int oper, const char *argp,
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size_t len, int argi,
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long argl, int ret, size_t *processed);
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typedef long (*BIO_callback_fn)(BIO *b, int oper, const char *argp, int argi,
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long argl, long ret);
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void BIO_set_callback_ex(BIO *b, BIO_callback_fn_ex callback);
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BIO_callback_fn_ex BIO_get_callback_ex(const BIO *b);
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void BIO_set_callback(BIO *b, BIO_callback_fn cb);
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BIO_callback_fn BIO_get_callback(BIO *b);
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void BIO_set_callback_arg(BIO *b, char *arg);
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char *BIO_get_callback_arg(const BIO *b);
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long BIO_debug_callback(BIO *bio, int cmd, const char *argp, int argi,
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long argl, long ret);
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=head1 DESCRIPTION
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BIO_set_callback_ex() and BIO_get_callback_ex() set and retrieve the BIO
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callback. The callback is called during most high level BIO operations. It can
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be used for debugging purposes to trace operations on a BIO or to modify its
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operation.
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BIO_set_callback() and BIO_get_callback() set and retrieve the old format BIO
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callback. New code should not use these functions, but they are retained for
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backwards compatibility. Any callback set via BIO_set_callback_ex() will get
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called in preference to any set by BIO_set_callback().
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BIO_set_callback_arg() and BIO_get_callback_arg() are macros which can be
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used to set and retrieve an argument for use in the callback.
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BIO_debug_callback() is a standard debugging callback which prints
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out information relating to each BIO operation. If the callback
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argument is set it is interpreted as a BIO to send the information
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to, otherwise stderr is used.
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BIO_callback_fn_ex() is the type of the callback function and BIO_callback_fn()
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is the type of the old format callback function. The meaning of each argument
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is described below:
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=over 4
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=item B<b>
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The BIO the callback is attached to is passed in B<b>.
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=item B<oper>
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B<oper> is set to the operation being performed. For some operations
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the callback is called twice, once before and once after the actual
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operation, the latter case has B<oper> or'ed with BIO_CB_RETURN.
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=item B<len>
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The length of the data requested to be read or written. This is only useful if
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B<oper> is BIO_CB_READ, BIO_CB_WRITE or BIO_CB_GETS.
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=item B<argp> B<argi> B<argl>
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The meaning of the arguments B<argp>, B<argi> and B<argl> depends on
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the value of B<oper>, that is the operation being performed.
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=item B<processed>
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B<processed> is a pointer to a location which will be updated with the amount of
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data that was actually read or written. Only used for BIO_CB_READ, BIO_CB_WRITE,
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BIO_CB_GETS and BIO_CB_PUTS.
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=item B<ret>
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B<ret> is the return value that would be returned to the
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application if no callback were present. The actual value returned
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is the return value of the callback itself. In the case of callbacks
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called before the actual BIO operation 1 is placed in B<ret>, if
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the return value is not positive it will be immediately returned to
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the application and the BIO operation will not be performed.
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=back
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The callback should normally simply return B<ret> when it has
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finished processing, unless it specifically wishes to modify the
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value returned to the application.
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=head1 CALLBACK OPERATIONS
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In the notes below, B<callback> defers to the actual callback
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function that is called.
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=over 4
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=item B<BIO_free(b)>
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callback_ex(b, BIO_CB_FREE, NULL, 0, 0, 0L, 1L, NULL)
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or
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callback(b, BIO_CB_FREE, NULL, 0L, 0L, 1L)
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is called before the free operation.
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=item B<BIO_read_ex(b, data, dlen, readbytes)>
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callback_ex(b, BIO_CB_READ, data, dlen, 0, 0L, 1L, NULL)
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or
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callback(b, BIO_CB_READ, data, dlen, 0L, 1L)
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is called before the read and
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callback_ex(b, BIO_CB_READ | BIO_CB_RETURN, data, dlen, 0, 0L, retvalue,
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&readbytes)
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or
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callback(b, BIO_CB_READ|BIO_CB_RETURN, data, dlen, 0L, retvalue)
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after.
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=item B<BIO_write(b, data, dlen, written)>
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callback_ex(b, BIO_CB_WRITE, data, dlen, 0, 0L, 1L, NULL)
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or
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callback(b, BIO_CB_WRITE, datat, dlen, 0L, 1L)
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is called before the write and
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callback_ex(b, BIO_CB_WRITE | BIO_CB_RETURN, data, dlen, 0, 0L, retvalue,
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&written)
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or
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callback(b, BIO_CB_WRITE|BIO_CB_RETURN, data, dlen, 0L, retvalue)
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after.
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=item B<BIO_gets(b, buf, size)>
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callback_ex(b, BIO_CB_GETS, buf, size, 0, 0L, 1, NULL, NULL)
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or
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callback(b, BIO_CB_GETS, buf, size, 0L, 1L)
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is called before the operation and
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callback_ex(b, BIO_CB_GETS | BIO_CB_RETURN, buf, size, 0, 0L, retvalue,
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&readbytes)
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or
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callback(b, BIO_CB_GETS|BIO_CB_RETURN, buf, size, 0L, retvalue)
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after.
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=item B<BIO_puts(b, buf)>
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callback_ex(b, BIO_CB_PUTS, buf, 0, 0, 0L, 1L, NULL);
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or
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callback(b, BIO_CB_PUTS, buf, 0, 0L, 1L)
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is called before the operation and
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callback_ex(b, BIO_CB_PUTS | BIO_CB_RETURN, buf, 0, 0, 0L, retvalue, &written)
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or
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callback(b, BIO_CB_PUTS|BIO_CB_RETURN, buf, 0, 0L, retvalue)
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after.
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=item B<BIO_ctrl(BIO *b, int cmd, long larg, void *parg)>
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callback_ex(b, BIO_CB_CTRL, parg, 0, cmd, larg, 1L, NULL)
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or
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callback(b, BIO_CB_CTRL, parg, cmd, larg, 1L)
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is called before the call and
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callback_ex(b, BIO_CB_CTRL | BIO_CB_RETURN, parg, 0, cmd, larg, ret, NULL)
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or
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callback(b, BIO_CB_CTRL|BIO_CB_RETURN, parg, cmd, larg, ret)
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after.
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Note: B<cmd> == B<BIO_CTRL_SET_CALLBACK> is special, because B<parg> is not the
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argument of type B<BIO_info_cb> itself. In this case B<parg> is a pointer to
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the actual call parameter, see B<BIO_callback_ctrl>.
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=back
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=head1 EXAMPLE
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The BIO_debug_callback() function is a good example, its source is
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in crypto/bio/bio_cb.c
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=head1 RETURN VALUES
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BIO_get_callback_ex() and BIO_get_callback() return the callback function
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previously set by a call to BIO_set_callback_ex() and BIO_set_callback()
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respectively.
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BIO_get_callback_arg() returns a B<char> pointer to the value previously set
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via a call to BIO_set_callback_arg().
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BIO_debug_callback() returns 1 or B<ret> if it's called after specific BIO
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operations.
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=head1 COPYRIGHT
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Copyright 2000-2018 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the Apache License 2.0 (the "License"). You may not use
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this file except in compliance with the License. You can obtain a copy
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in the file LICENSE in the source distribution or at
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L<https://www.openssl.org/source/license.html>.
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=cut
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