OSSL_CALLBACK, OSSL_PASSPHRASE_CALLBACK - OpenSSL Core type to define callbacks
#include <openssl/core.h>
typedef int (OSSL_CALLBACK)(const OSSL_PARAM params[], void *arg);
typedef int (OSSL_PASSPHRASE_CALLBACK)(char *pass, size_t pass_size,
size_t *pass_len,
const OSSL_PARAM params[],
void *arg);
For certain events or activities, provider functionality may need help from the
application or the calling OpenSSL libraries themselves. For example, user
input or direct (possibly optional) user output could be implemented this way.
Callback functions themselves are always provided by or through the calling
OpenSSL libraries, along with a generic pointer to data
arg. As far as
the function receiving the pointer to the function pointer and
arg is
concerned, the data that
arg points at is opaque, and the pointer
should simply be passed back to the callback function when it's called.
- OSSL_CALLBACK
- This is a generic callback function. When calling this
callback function, the caller is expected to build an OSSL_PARAM(3)
array of data it wants or is expected to pass back, and pass that as
params, as well as the opaque data pointer it received, as
arg.
- OSSL_PASSPHRASE_CALLBACK
- This is a specialised callback function, used specifically
to prompt the user for a passphrase. When calling this callback function,
a buffer to store the pass phrase needs to be given with pass, and
its size with pass_size. The length of the prompted pass phrase
will be given back in *pass_len.
Additional parameters can be passed with the OSSL_PARAM(3) array
params,
openssl-core.h(7)
The types described here were added in OpenSSL 3.0.
Copyright 2022 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (the "License"). You may not use
this file except in compliance with the License. You can obtain a copy in the
file LICENSE in the source distribution or at
<
https://www.openssl.org/source/license.html>.