NAME

       OSSL_STORE_CTX, OSSL_STORE_post_process_info_fn, OSSL_STORE_open, OSSL_STORE_open_ex,
       OSSL_STORE_ctrl, OSSL_STORE_load, OSSL_STORE_eof, OSSL_STORE_error, OSSL_STORE_close -
       Types and functions to read objects from a URI

SYNOPSIS

        #include <openssl/store.h>

        typedef struct ossl_store_ctx_st OSSL_STORE_CTX;

        typedef OSSL_STORE_INFO *(*OSSL_STORE_post_process_info_fn)(OSSL_STORE_INFO *,
                                                                    void *);

        OSSL_STORE_CTX *OSSL_STORE_open(const char *uri, const UI_METHOD *ui_method,
                                        void *ui_data,
                                        OSSL_STORE_post_process_info_fn post_process,
                                        void *post_process_data);
        OSSL_STORE_CTX *
        OSSL_STORE_open_ex(const char *uri, OSSL_LIB_CTX *libctx, const char *propq,
                           const UI_METHOD *ui_method, void *ui_data,
                           const OSSL_PARAM params[],
                           OSSL_STORE_post_process_info_fn post_process,
                           void *post_process_data);

        OSSL_STORE_INFO *OSSL_STORE_load(OSSL_STORE_CTX *ctx);
        int OSSL_STORE_eof(OSSL_STORE_CTX *ctx);
        int OSSL_STORE_error(OSSL_STORE_CTX *ctx);
        int OSSL_STORE_close(OSSL_STORE_CTX *ctx);

       The following function has been deprecated since OpenSSL 3.0, and can be hidden entirely
       by defining OPENSSL_API_COMPAT with a suitable version value, see openssl_user_macros(7):

        int OSSL_STORE_ctrl(OSSL_STORE_CTX *ctx, int cmd, ... /* args */);

DESCRIPTION

       These functions help the application to fetch supported objects (see "SUPPORTED OBJECTS"
       in OSSL_STORE_INFO(3) for information on which those are) from a given URI.  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).

   Types
       OSSL_STORE_CTX is a context variable that holds all the internal information for
       OSSL_STORE_open(), OSSL_STORE_open_ex(), OSSL_STORE_load(), OSSL_STORE_eof() and
       OSSL_STORE_close() to work together.

   Functions
       OSSL_STORE_open_ex() 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, a library context libctx with an associated property query propq, and
       opens a channel to the data located at the 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 auxiliary OSSL_PARAM(3) parameters in params can be set to further modify
       the store operation.  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_open() is similar to OSSL_STORE_open_ex() but uses NULL for the params, the
       library context libctx and property query propq.

       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.

       There are also global controls available:

       OSSL_STORE_C_USE_SECMEM
           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 and 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.

NOTES

       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.

RETURN VALUES

       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 or an error occurred, 0
       otherwise.

       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.

SEE ALSO

       ossl_store(7), OSSL_STORE_INFO(3), OSSL_STORE_register_loader(3), passphrase-encoding(7)

HISTORY

       OSSL_STORE_open_ex() was added in OpenSSL 3.0.

       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.

       OSSL_STORE_open_ex() was added in OpenSSL 3.0.

       OSSL_STORE_ctrl() and OSSL_STORE_vctrl() were deprecated in OpenSSL 3.0.

COPYRIGHT

       Copyright 2016-2021 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>.