| 1 | =pod
|
|---|
| 2 |
|
|---|
| 3 | =head1 NAME
|
|---|
| 4 |
|
|---|
| 5 | SSL_CTX_set_async_callback,
|
|---|
| 6 | SSL_CTX_set_async_callback_arg,
|
|---|
| 7 | SSL_set_async_callback,
|
|---|
| 8 | SSL_set_async_callback_arg,
|
|---|
| 9 | SSL_get_async_status,
|
|---|
| 10 | SSL_async_callback_fn
|
|---|
| 11 | - manage asynchronous operations
|
|---|
| 12 |
|
|---|
| 13 | =head1 SYNOPSIS
|
|---|
| 14 |
|
|---|
| 15 | =for openssl multiple includes
|
|---|
| 16 |
|
|---|
| 17 | #include <openssl/ssl.h>
|
|---|
| 18 |
|
|---|
| 19 | typedef int (*SSL_async_callback_fn)(SSL *s, void *arg);
|
|---|
| 20 | int SSL_CTX_set_async_callback(SSL_CTX *ctx, SSL_async_callback_fn callback);
|
|---|
| 21 | int SSL_CTX_set_async_callback_arg(SSL_CTX *ctx, void *arg);
|
|---|
| 22 | int SSL_set_async_callback(SSL *s, SSL_async_callback_fn callback);
|
|---|
| 23 | int SSL_set_async_callback_arg(SSL *s, void *arg);
|
|---|
| 24 | int SSL_get_async_status(SSL *s, int *status);
|
|---|
| 25 |
|
|---|
| 26 | =head1 DESCRIPTION
|
|---|
| 27 |
|
|---|
| 28 | SSL_CTX_set_async_callback() sets an asynchronous callback function. All B<SSL>
|
|---|
| 29 | objects generated based on this B<SSL_CTX> will get this callback. If an engine
|
|---|
| 30 | supports the callback mechanism, it will be automatically called if
|
|---|
| 31 | B<SSL_MODE_ASYNC> has been set and an asynchronous capable engine completes a
|
|---|
| 32 | cryptography operation to notify the application to resume the paused work flow.
|
|---|
| 33 |
|
|---|
| 34 | SSL_CTX_set_async_callback_arg() sets the callback argument.
|
|---|
| 35 |
|
|---|
| 36 | SSL_set_async_callback() allows an application to set a callback in an
|
|---|
| 37 | asynchronous B<SSL> object, so that when an engine completes a cryptography
|
|---|
| 38 | operation, the callback will be called to notify the application to resume the
|
|---|
| 39 | paused work flow.
|
|---|
| 40 |
|
|---|
| 41 | SSL_set_async_callback_arg() sets an argument for the B<SSL> object when the
|
|---|
| 42 | above callback is called.
|
|---|
| 43 |
|
|---|
| 44 | SSL_get_async_status() returns the engine status. This function facilitates the
|
|---|
| 45 | communication from the engine to the application. During an SSL session,
|
|---|
| 46 | cryptographic operations are dispatched to an engine. The engine status is very
|
|---|
| 47 | useful for an application to know if the operation has been successfully
|
|---|
| 48 | dispatched. If the engine does not support this additional callback method,
|
|---|
| 49 | B<ASYNC_STATUS_UNSUPPORTED> will be returned. See ASYNC_WAIT_CTX_set_status()
|
|---|
| 50 | for a description of all of the status values.
|
|---|
| 51 |
|
|---|
| 52 | An example of the above functions would be the following:
|
|---|
| 53 |
|
|---|
| 54 | =over 4
|
|---|
| 55 |
|
|---|
| 56 | =item 1.
|
|---|
| 57 |
|
|---|
| 58 | Application sets the async callback and callback data on an SSL connection
|
|---|
| 59 | by calling SSL_set_async_callback().
|
|---|
| 60 |
|
|---|
| 61 | =item 2.
|
|---|
| 62 |
|
|---|
| 63 | Application sets B<SSL_MODE_ASYNC> and makes an asynchronous SSL call
|
|---|
| 64 |
|
|---|
| 65 | =item 3.
|
|---|
| 66 |
|
|---|
| 67 | OpenSSL submits the asynchronous request to the engine. If a retry occurs at
|
|---|
| 68 | this point then the status within the B<ASYNC_WAIT_CTX> would be set and the
|
|---|
| 69 | async callback function would be called (goto Step 7).
|
|---|
| 70 |
|
|---|
| 71 | =item 4.
|
|---|
| 72 |
|
|---|
| 73 | The OpenSSL engine pauses the current job and returns, so that the
|
|---|
| 74 | application can continue processing other connections.
|
|---|
| 75 |
|
|---|
| 76 | =item 5.
|
|---|
| 77 |
|
|---|
| 78 | At a future point in time (probably via a polling mechanism or via an
|
|---|
| 79 | interrupt) the engine will become aware that the asynchronous request has
|
|---|
| 80 | finished processing.
|
|---|
| 81 |
|
|---|
| 82 | =item 6.
|
|---|
| 83 |
|
|---|
| 84 | The engine will call the application's callback passing the callback data as
|
|---|
| 85 | a parameter.
|
|---|
| 86 |
|
|---|
| 87 | =item 7.
|
|---|
| 88 |
|
|---|
| 89 | The callback function should then run. Note: it is a requirement that the
|
|---|
| 90 | callback function is small and nonblocking as it will be run in the context of
|
|---|
| 91 | a polling mechanism or an interrupt.
|
|---|
| 92 |
|
|---|
| 93 | =item 8.
|
|---|
| 94 |
|
|---|
| 95 | It is the application's responsibility via the callback function to schedule
|
|---|
| 96 | recalling the OpenSSL asynchronous function and to continue processing.
|
|---|
| 97 |
|
|---|
| 98 | =item 9.
|
|---|
| 99 |
|
|---|
| 100 | The callback function has the option to check the status returned via
|
|---|
| 101 | SSL_get_async_status() to determine whether a retry happened instead of the
|
|---|
| 102 | request being submitted, allowing different processing if required.
|
|---|
| 103 |
|
|---|
| 104 | =back
|
|---|
| 105 |
|
|---|
| 106 | =head1 RETURN VALUES
|
|---|
| 107 |
|
|---|
| 108 | SSL_CTX_set_async_callback(), SSL_set_async_callback(),
|
|---|
| 109 | SSL_CTX_set_async_callback_arg(), SSL_CTX_set_async_callback_arg() and
|
|---|
| 110 | SSL_get_async_status() return 1 on success or 0 on error.
|
|---|
| 111 |
|
|---|
| 112 | =head1 SEE ALSO
|
|---|
| 113 |
|
|---|
| 114 | L<ssl(7)>
|
|---|
| 115 |
|
|---|
| 116 | =head1 HISTORY
|
|---|
| 117 |
|
|---|
| 118 | SSL_CTX_set_async_callback(), SSL_CTX_set_async_callback_arg(),
|
|---|
| 119 | SSL_set_async_callback(), SSL_set_async_callback_arg() and
|
|---|
| 120 | SSL_get_async_status() were first added to OpenSSL 3.0.
|
|---|
| 121 |
|
|---|
| 122 | =head1 COPYRIGHT
|
|---|
| 123 |
|
|---|
| 124 | Copyright 2019-2021 The OpenSSL Project Authors. All Rights Reserved.
|
|---|
| 125 |
|
|---|
| 126 | Licensed under the Apache License 2.0 (the "License"). You may not use
|
|---|
| 127 | this file except in compliance with the License. You can obtain a copy
|
|---|
| 128 | in the file LICENSE in the source distribution or at
|
|---|
| 129 | L<https://www.openssl.org/source/license.html>.
|
|---|
| 130 |
|
|---|
| 131 | =cut
|
|---|
