OSSL_STORE_CTX, OSSL_STORE_post_process_info_fn, OSSL_STORE_open,
OSSL_STORE_ctrl, OSSL_STORE_load, OSSL_STORE_eof, OSSL_STORE_error,
OSSL_STORE_close - Types and functions to read objects from a URI
These functions help the application to fetch supported objects (see
OSSL_STORE_INFO(3)/SUPPORTED OBJECTS for information on which those are)
from a given URI (see SUPPORTED SCHEMES for more information on
the supported URI schemes).
The general method to do so is to "open" the URI using OSSL_STORE_open(),
read each available and supported object using OSSL_STORE_load() as long as
OSSL_STORE_eof() hasn't been reached, and finish it off with OSSL_STORE_close().
The retrieved information is stored in a OSSL_STORE_INFO, which is further
described in OSSL_STORE_INFO(3).
OSSL_STORE_CTX is a context variable that holds all the internal
information for OSSL_STORE_open(), OSSL_STORE_load(), OSSL_STORE_eof() and
OSSL_STORE_close() to work together.
OSSL_STORE_open() takes a uri or path uri, password UI method
ui_method with associated data ui_data, and post processing
callback post_process with associated data post_process_data,
opens a channel to the data located at that URI and returns a
OSSL_STORE_CTX with all necessary internal information.
The given ui_method and ui_data will be reused by all
functions that use OSSL_STORE_CTX when interaction is needed,
for instance to provide a password.
The given post_process and post_process_data will be reused by
OSSL_STORE_load() to manipulate or drop the value to be returned.
The post_process function drops values by returning NULL, which
will cause OSSL_STORE_load() to start its process over with loading
the next object, until post_process returns something other than
NULL, or the end of data is reached as indicated by OSSL_STORE_eof().
OSSL_STORE_ctrl() takes a OSSL_STORE_CTX, and command number cmd and
more arguments not specified here.
The available loader specific command numbers and arguments they each
take depends on the loader that's used and is documented together with
that loader.
Controls if the loader should attempt to use secure memory for any
allocated OSSL_STORE_INFO and its contents.
This control expects one argument, a pointer to an int that is expected to
have the value 1 (yes) or 0 (no).
Any other value is an error.
OSSL_STORE_load() takes a OSSL_STORE_CTX, tries to load the next available
object and return it wrapped with OSSL_STORE_INFO.
OSSL_STORE_eof() takes a OSSL_STORE_CTX and checks if we've reached the end
of data.
OSSL_STORE_error() takes a OSSL_STORE_CTX and checks if an error occurred in
the last OSSL_STORE_load() call.
Note that it may still be meaningful to try and load more objects, unless
OSSL_STORE_eof() shows that the end of data has been reached.
OSSL_STORE_close() takes a OSSL_STORE_CTX, closes the channel that was opened
by OSSL_STORE_open() and frees all other information that was stored in the
OSSL_STORE_CTX, as well as the OSSL_STORE_CTX itself.
If ctx is NULL it does nothing.
A string without a scheme prefix (that is, a non-URI string) is
implicitly interpreted as using the file: scheme.
There are some tools that can be used together with
OSSL_STORE_open() to determine if any failure is caused by an unparsable
URI, or if it's a different error (such as memory allocation
failures); if the URI was parsable but the scheme unregistered, the
top error will have the reason OSSL_STORE_R_UNREGISTERED_SCHEME.
These functions make no direct assumption regarding the pass phrase received
from the password callback.
The loaders may make assumptions, however.
For example, the file: scheme loader inherits the assumptions made by
OpenSSL functionality that handles the different file types; this is mostly
relevant for PKCS#12 objects.
See passphrase-encoding(7) for further information.
OSSL_STORE_open() returns a pointer to a OSSL_STORE_CTX on success, or
NULL on failure.
OSSL_STORE_load() returns a pointer to a OSSL_STORE_INFO on success, or
NULL on error or when end of data is reached.
Use OSSL_STORE_error() and OSSL_STORE_eof() to determine the meaning of a
returned NULL.
OSSL_STORE_eof() returns 1 if the end of data has been reached, otherwise
0.
OSSL_STORE_error() returns 1 if an error occurred in an OSSL_STORE_load() call,
otherwise 0.
OSSL_STORE_ctrl() and OSSL_STORE_close() returns 1 on success, or 0 on failure.
OSSL_STORE_CTX(), OSSL_STORE_post_process_info_fn(), OSSL_STORE_open(),
OSSL_STORE_ctrl(), OSSL_STORE_load(), OSSL_STORE_eof() and OSSL_STORE_close()
were added in OpenSSL 1.1.1.
Handling of NULL ctx argument for OSSL_STORE_close()
was introduced in OpenSSL 1.1.1h.
Copyright 2016-2020 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the OpenSSL license (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.