mirror of https://github.com/openssl/openssl.git
167 lines
6.2 KiB
Plaintext
167 lines
6.2 KiB
Plaintext
=pod
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=head1 NAME
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OSSL_STORE_CTX, OSSL_STORE_post_process_info_fn, OSSL_STORE_open,
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OSSL_STORE_ctrl, OSSL_STORE_load, OSSL_STORE_eof, OSSL_STORE_error,
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OSSL_STORE_close - Types and functions to read objects from a URI
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=head1 SYNOPSIS
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#include <openssl/store.h>
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typedef struct ossl_store_ctx_st OSSL_STORE_CTX;
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typedef OSSL_STORE_INFO *(*OSSL_STORE_post_process_info_fn)(OSSL_STORE_INFO *,
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void *);
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OSSL_STORE_CTX *OSSL_STORE_open(const char *uri, const UI_METHOD *ui_method,
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void *ui_data,
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OSSL_STORE_post_process_info_fn post_process,
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void *post_process_data);
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int OSSL_STORE_ctrl(OSSL_STORE_CTX *ctx, int cmd, ... /* args */);
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OSSL_STORE_INFO *OSSL_STORE_load(OSSL_STORE_CTX *ctx);
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int OSSL_STORE_eof(OSSL_STORE_CTX *ctx);
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int OSSL_STORE_error(OSSL_STORE_CTX *ctx);
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int OSSL_STORE_close(OSSL_STORE_CTX *ctx);
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=head1 DESCRIPTION
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These functions help the application to fetch supported objects (see
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L<OSSL_STORE_INFO(3)/SUPPORTED OBJECTS> for information on which those are)
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from a given URI (see L</SUPPORTED SCHEMES> for more information on
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the supported URI schemes).
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The general method to do so is to "open" the URI using OSSL_STORE_open(),
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read each available and supported object using OSSL_STORE_load() as long as
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OSSL_STORE_eof() hasn't been reached, and finish it off with OSSL_STORE_close().
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The retrieved information is stored in a B<OSSL_STORE_INFO>, which is further
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described in L<OSSL_STORE_INFO(3)>.
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=head2 Types
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B<OSSL_STORE_CTX> is a context variable that holds all the internal
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information for OSSL_STORE_open(), OSSL_STORE_load(), OSSL_STORE_eof() and
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OSSL_STORE_close() to work together.
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=head2 Functions
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OSSL_STORE_open() takes a uri or path I<uri>, password UI method
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I<ui_method> with associated data I<ui_data>, and post processing
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callback I<post_process> with associated data I<post_process_data>,
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opens a channel to the data located at that URI and returns a
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B<OSSL_STORE_CTX> with all necessary internal information.
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The given I<ui_method> and I<ui_data> will be reused by all
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functions that use B<OSSL_STORE_CTX> when interaction is needed,
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for instance to provide a password.
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The given I<post_process> and I<post_process_data> will be reused by
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OSSL_STORE_load() to manipulate or drop the value to be returned.
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The I<post_process> function drops values by returning NULL, which
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will cause OSSL_STORE_load() to start its process over with loading
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the next object, until I<post_process> returns something other than
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NULL, or the end of data is reached as indicated by OSSL_STORE_eof().
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OSSL_STORE_ctrl() takes a B<OSSL_STORE_CTX>, and command number I<cmd> and
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more arguments not specified here.
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The available loader specific command numbers and arguments they each
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take depends on the loader that's used and is documented together with
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that loader.
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There are also global controls available:
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=over 4
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=item B<OSSL_STORE_C_USE_SECMEM>
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Controls if the loader should attempt to use secure memory for any
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allocated B<OSSL_STORE_INFO> and its contents.
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This control expects one argument, a pointer to an B<int> that is expected to
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have the value 1 (yes) or 0 (no).
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Any other value is an error.
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=back
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OSSL_STORE_load() takes a B<OSSL_STORE_CTX>, tries to load the next available
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object and return it wrapped with B<OSSL_STORE_INFO>.
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OSSL_STORE_eof() takes a B<OSSL_STORE_CTX> and checks if we've reached the end
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of data.
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OSSL_STORE_error() takes a B<OSSL_STORE_CTX> and checks if an error occurred in
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the last OSSL_STORE_load() call.
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Note that it may still be meaningful to try and load more objects, unless
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OSSL_STORE_eof() shows that the end of data has been reached.
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OSSL_STORE_close() takes a B<OSSL_STORE_CTX>, closes the channel that was opened
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by OSSL_STORE_open() and frees all other information that was stored in the
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B<OSSL_STORE_CTX>, as well as the B<OSSL_STORE_CTX> itself.
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If I<ctx> is NULL it does nothing.
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=head1 SUPPORTED SCHEMES
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The basic supported scheme is B<file:>.
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Any other scheme can be added dynamically, using
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OSSL_STORE_register_loader().
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=head1 NOTES
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A string without a scheme prefix (that is, a non-URI string) is
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implicitly interpreted as using the F<file:> scheme.
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There are some tools that can be used together with
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OSSL_STORE_open() to determine if any failure is caused by an unparsable
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URI, or if it's a different error (such as memory allocation
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failures); if the URI was parsable but the scheme unregistered, the
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top error will have the reason C<OSSL_STORE_R_UNREGISTERED_SCHEME>.
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These functions make no direct assumption regarding the pass phrase received
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from the password callback.
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The loaders may make assumptions, however.
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For example, the B<file:> scheme loader inherits the assumptions made by
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OpenSSL functionality that handles the different file types; this is mostly
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relevant for PKCS#12 objects.
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See L<passphrase-encoding(7)> for further information.
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=head1 RETURN VALUES
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OSSL_STORE_open() returns a pointer to a B<OSSL_STORE_CTX> on success, or
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NULL on failure.
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OSSL_STORE_load() returns a pointer to a B<OSSL_STORE_INFO> on success, or
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NULL on error or when end of data is reached.
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Use OSSL_STORE_error() and OSSL_STORE_eof() to determine the meaning of a
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returned NULL.
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OSSL_STORE_eof() returns 1 if the end of data has been reached, otherwise
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0.
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OSSL_STORE_error() returns 1 if an error occurred in an OSSL_STORE_load() call,
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otherwise 0.
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OSSL_STORE_ctrl() and OSSL_STORE_close() returns 1 on success, or 0 on failure.
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=head1 SEE ALSO
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L<ossl_store(7)>, L<OSSL_STORE_INFO(3)>, L<OSSL_STORE_register_loader(3)>,
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L<passphrase-encoding(7)>
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=head1 HISTORY
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OSSL_STORE_CTX(), OSSL_STORE_post_process_info_fn(), OSSL_STORE_open(),
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OSSL_STORE_ctrl(), OSSL_STORE_load(), OSSL_STORE_eof() and OSSL_STORE_close()
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were added in OpenSSL 1.1.1.
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Handling of NULL I<ctx> argument for OSSL_STORE_close()
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was introduced in OpenSSL 1.1.1h.
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=head1 COPYRIGHT
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Copyright 2016-2020 The OpenSSL Project Authors. All Rights Reserved.
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Licensed under the OpenSSL license (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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