1=pod
2
3=head1 NAME
4
5OSSL_STORE_CTX, OSSL_STORE_post_process_info_fn, OSSL_STORE_open,
6OSSL_STORE_ctrl, OSSL_STORE_load, OSSL_STORE_eof, OSSL_STORE_error,
7OSSL_STORE_close - Types and functions to read objects from a URI
8
9=head1 SYNOPSIS
10
11 #include <openssl/store.h>
12
13 typedef struct ossl_store_ctx_st OSSL_STORE_CTX;
14
15 typedef OSSL_STORE_INFO *(*OSSL_STORE_post_process_info_fn)(OSSL_STORE_INFO *,
16                                                             void *);
17
18 OSSL_STORE_CTX *OSSL_STORE_open(const char *uri, const UI_METHOD *ui_method,
19                                 void *ui_data,
20                                 OSSL_STORE_post_process_info_fn post_process,
21                                 void *post_process_data);
22 int OSSL_STORE_ctrl(OSSL_STORE_CTX *ctx, int cmd, ... /* args */);
23 OSSL_STORE_INFO *OSSL_STORE_load(OSSL_STORE_CTX *ctx);
24 int OSSL_STORE_eof(OSSL_STORE_CTX *ctx);
25 int OSSL_STORE_error(OSSL_STORE_CTX *ctx);
26 int OSSL_STORE_close(OSSL_STORE_CTX *ctx);
27
28=head1 DESCRIPTION
29
30These functions help the application to fetch supported objects (see
31L<OSSL_STORE_INFO(3)/SUPPORTED OBJECTS> for information on which those are)
32from a given URI (see L</SUPPORTED SCHEMES> for more information on
33the supported URI schemes).
34The general method to do so is to "open" the URI using OSSL_STORE_open(),
35read each available and supported object using OSSL_STORE_load() as long as
36OSSL_STORE_eof() hasn't been reached, and finish it off with OSSL_STORE_close().
37
38The retrieved information is stored in a B<OSSL_STORE_INFO>, which is further
39described in L<OSSL_STORE_INFO(3)>.
40
41=head2 Types
42
43B<OSSL_STORE_CTX> is a context variable that holds all the internal
44information for OSSL_STORE_open(), OSSL_STORE_load(), OSSL_STORE_eof() and
45OSSL_STORE_close() to work together.
46
47=head2 Functions
48
49OSSL_STORE_open() takes a uri or path B<uri>, password UI method
50B<ui_method> with associated data B<ui_data>, and post processing
51callback B<post_process> with associated data B<post_process_data>,
52opens a channel to the data located at that URI and returns a
53B<OSSL_STORE_CTX> with all necessary internal information.
54The given B<ui_method> and B<ui_data_data> will be reused by all
55functions that use B<OSSL_STORE_CTX> when interaction is needed.
56The given B<post_process> and B<post_process_data> will be reused by
57OSSL_STORE_load() to manipulate or drop the value to be returned.
58The B<post_process> function drops values by returning B<NULL>, which
59will cause OSSL_STORE_load() to start its process over with loading
60the next object, until B<post_process> returns something other than
61B<NULL>, or the end of data is reached as indicated by OSSL_STORE_eof().
62
63OSSL_STORE_ctrl() takes a B<OSSL_STORE_CTX>, and command number B<cmd> and
64more arguments not specified here.
65The available loader specific command numbers and arguments they each
66take depends on the loader that's used and is documented together with
67that loader.
68
69There are also global controls available:
70
71=over 4
72
73=item B<OSSL_STORE_C_USE_SECMEM>
74
75Controls if the loader should attempt to use secure memory for any
76allocated B<OSSL_STORE_INFO> and its contents.
77This control expects one argument, a pointer to an B<int> that is expected to
78have the value 1 (yes) or 0 (no).
79Any other value is an error.
80
81=back
82
83OSSL_STORE_load() takes a B<OSSL_STORE_CTX>, tries to load the next available
84object and return it wrapped with  B<OSSL_STORE_INFO>.
85
86OSSL_STORE_eof() takes a B<OSSL_STORE_CTX> and checks if we've reached the end
87of data.
88
89OSSL_STORE_error() takes a B<OSSL_STORE_CTX> and checks if an error occurred in
90the last OSSL_STORE_load() call.
91Note that it may still be meaningful to try and load more objects, unless
92OSSL_STORE_eof() shows that the end of data has been reached.
93
94OSSL_STORE_close() takes a B<OSSL_STORE_CTX>, closes the channel that was opened
95by OSSL_STORE_open() and frees all other information that was stored in the
96B<OSSL_STORE_CTX>, as well as the B<OSSL_STORE_CTX> itself.
97
98=head1 SUPPORTED SCHEMES
99
100The basic supported scheme is B<file:>.
101Any other scheme can be added dynamically, using
102OSSL_STORE_register_loader().
103
104=head1 NOTES
105
106A string without a scheme prefix (that is, a non-URI string) is
107implicitly interpreted as using the F<file:> scheme.
108
109There are some tools that can be used together with
110OSSL_STORE_open() to determine if any failure is caused by an unparsable
111URI, or if it's a different error (such as memory allocation
112failures); if the URI was parsable but the scheme unregistered, the
113top error will have the reason C<OSSL_STORE_R_UNREGISTERED_SCHEME>.
114
115These functions make no direct assumption regarding the pass phrase received
116from the password callback.
117The loaders may make assumptions, however.
118For example, the B<file:> scheme loader inherits the assumptions made by
119OpenSSL functionality that handles the different file types; this is mostly
120relevant for PKCS#12 objects.
121See L<passphrase-encoding(7)> for further information.
122
123=head1 RETURN VALUES
124
125OSSL_STORE_open() returns a pointer to a B<OSSL_STORE_CTX> on success, or
126B<NULL> on failure.
127
128OSSL_STORE_load() returns a pointer to a B<OSSL_STORE_INFO> on success, or
129B<NULL> on error or when end of data is reached.
130Use OSSL_STORE_error() and OSSL_STORE_eof() to determine the meaning of a
131returned B<NULL>.
132
133OSSL_STORE_eof() returns 1 if the end of data has been reached, otherwise
1340.
135
136OSSL_STORE_error() returns 1 if an error occurred in an OSSL_STORE_load() call,
137otherwise 0.
138
139OSSL_STORE_ctrl() and OSSL_STORE_close() returns 1 on success, or 0 on failure.
140
141=head1 SEE ALSO
142
143L<ossl_store(7)>, L<OSSL_STORE_INFO(3)>, L<OSSL_STORE_register_loader(3)>,
144L<passphrase-encoding(7)>
145
146=head1 HISTORY
147
148OSSL_STORE_CTX(), OSSL_STORE_post_process_info_fn(), OSSL_STORE_open(),
149OSSL_STORE_ctrl(), OSSL_STORE_load(), OSSL_STORE_eof() and OSSL_STORE_close()
150were added in OpenSSL 1.1.1.
151
152=head1 COPYRIGHT
153
154Copyright 2016-2018 The OpenSSL Project Authors. All Rights Reserved.
155
156Licensed under the OpenSSL license (the "License").  You may not use
157this file except in compliance with the License.  You can obtain a copy
158in the file LICENSE in the source distribution or at
159L<https://www.openssl.org/source/license.html>.
160
161=cut
162