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 I<uri>, password UI method
50I<ui_method> with associated data I<ui_data>, and post processing
51callback I<post_process> with associated data I<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 I<ui_method> and I<ui_data> will be reused by all
55functions that use B<OSSL_STORE_CTX> when interaction is needed,
56for instance to provide a password.
57The given I<post_process> and I<post_process_data> will be reused by
58OSSL_STORE_load() to manipulate or drop the value to be returned.
59The I<post_process> function drops values by returning NULL, which
60will cause OSSL_STORE_load() to start its process over with loading
61the next object, until I<post_process> returns something other than
62NULL, or the end of data is reached as indicated by OSSL_STORE_eof().
63
64OSSL_STORE_ctrl() takes a B<OSSL_STORE_CTX>, and command number I<cmd> and
65more arguments not specified here.
66The available loader specific command numbers and arguments they each
67take depends on the loader that's used and is documented together with
68that loader.
69
70There are also global controls available:
71
72=over 4
73
74=item B<OSSL_STORE_C_USE_SECMEM>
75
76Controls if the loader should attempt to use secure memory for any
77allocated B<OSSL_STORE_INFO> and its contents.
78This control expects one argument, a pointer to an B<int> that is expected to
79have the value 1 (yes) or 0 (no).
80Any other value is an error.
81
82=back
83
84OSSL_STORE_load() takes a B<OSSL_STORE_CTX>, tries to load the next available
85object and return it wrapped with  B<OSSL_STORE_INFO>.
86
87OSSL_STORE_eof() takes a B<OSSL_STORE_CTX> and checks if we've reached the end
88of data.
89
90OSSL_STORE_error() takes a B<OSSL_STORE_CTX> and checks if an error occurred in
91the last OSSL_STORE_load() call.
92Note that it may still be meaningful to try and load more objects, unless
93OSSL_STORE_eof() shows that the end of data has been reached.
94
95OSSL_STORE_close() takes a B<OSSL_STORE_CTX>, closes the channel that was opened
96by OSSL_STORE_open() and frees all other information that was stored in the
97B<OSSL_STORE_CTX>, as well as the B<OSSL_STORE_CTX> itself.
98If I<ctx> is NULL it does nothing.
99
100=head1 SUPPORTED SCHEMES
101
102The basic supported scheme is B<file:>.
103Any other scheme can be added dynamically, using
104OSSL_STORE_register_loader().
105
106=head1 NOTES
107
108A string without a scheme prefix (that is, a non-URI string) is
109implicitly interpreted as using the F<file:> scheme.
110
111There are some tools that can be used together with
112OSSL_STORE_open() to determine if any failure is caused by an unparsable
113URI, or if it's a different error (such as memory allocation
114failures); if the URI was parsable but the scheme unregistered, the
115top error will have the reason C<OSSL_STORE_R_UNREGISTERED_SCHEME>.
116
117These functions make no direct assumption regarding the pass phrase received
118from the password callback.
119The loaders may make assumptions, however.
120For example, the B<file:> scheme loader inherits the assumptions made by
121OpenSSL functionality that handles the different file types; this is mostly
122relevant for PKCS#12 objects.
123See L<passphrase-encoding(7)> for further information.
124
125=head1 RETURN VALUES
126
127OSSL_STORE_open() returns a pointer to a B<OSSL_STORE_CTX> on success, or
128NULL on failure.
129
130OSSL_STORE_load() returns a pointer to a B<OSSL_STORE_INFO> on success, or
131NULL on error or when end of data is reached.
132Use OSSL_STORE_error() and OSSL_STORE_eof() to determine the meaning of a
133returned NULL.
134
135OSSL_STORE_eof() returns 1 if the end of data has been reached, otherwise
1360.
137
138OSSL_STORE_error() returns 1 if an error occurred in an OSSL_STORE_load() call,
139otherwise 0.
140
141OSSL_STORE_ctrl() and OSSL_STORE_close() returns 1 on success, or 0 on failure.
142
143=head1 SEE ALSO
144
145L<ossl_store(7)>, L<OSSL_STORE_INFO(3)>, L<OSSL_STORE_register_loader(3)>,
146L<passphrase-encoding(7)>
147
148=head1 HISTORY
149
150OSSL_STORE_CTX(), OSSL_STORE_post_process_info_fn(), OSSL_STORE_open(),
151OSSL_STORE_ctrl(), OSSL_STORE_load(), OSSL_STORE_eof() and OSSL_STORE_close()
152were added in OpenSSL 1.1.1.
153
154Handling of NULL I<ctx> argument for OSSL_STORE_close()
155was introduced in OpenSSL 1.1.1h.
156
157=head1 COPYRIGHT
158
159Copyright 2016-2020 The OpenSSL Project Authors. All Rights Reserved.
160
161Licensed under the OpenSSL license (the "License").  You may not use
162this file except in compliance with the License.  You can obtain a copy
163in the file LICENSE in the source distribution or at
164L<https://www.openssl.org/source/license.html>.
165
166=cut
167