1OSSL_STORE_OPEN(3)                  OpenSSL                 OSSL_STORE_OPEN(3)
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NAME

6       OSSL_STORE_CTX, OSSL_STORE_post_process_info_fn, OSSL_STORE_open,
7       OSSL_STORE_ctrl, OSSL_STORE_load, OSSL_STORE_eof, OSSL_STORE_error,
8       OSSL_STORE_close - Types and functions to read objects from a URI
9

SYNOPSIS

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

DESCRIPTION

29       These functions help the application to fetch supported objects (see
30       "SUPPORTED OBJECTS" in OSSL_STORE_INFO(3) for information on which
31       those are) from a given URI (see "SUPPORTED SCHEMES" for more
32       information on the supported URI schemes).  The general method to do so
33       is to "open" the URI using OSSL_STORE_open(), read each available and
34       supported object using OSSL_STORE_load() as long as OSSL_STORE_eof()
35       hasn't been reached, and finish it off with OSSL_STORE_close().
36
37       The retrieved information is stored in a OSSL_STORE_INFO, which is
38       further described in OSSL_STORE_INFO(3).
39
40   Types
41       OSSL_STORE_CTX is a context variable that holds all the internal
42       information for OSSL_STORE_open(), OSSL_STORE_load(), OSSL_STORE_eof()
43       and OSSL_STORE_close() to work together.
44
45   Functions
46       OSSL_STORE_open() takes a uri or path uri, password UI method ui_method
47       with associated data ui_data, and post processing callback post_process
48       with associated data post_process_data, opens a channel to the data
49       located at that URI and returns a OSSL_STORE_CTX with all necessary
50       internal information.  The given ui_method and ui_data will be reused
51       by all functions that use OSSL_STORE_CTX when interaction is needed,
52       for instance to provide a password.  The given post_process and
53       post_process_data will be reused by OSSL_STORE_load() to manipulate or
54       drop the value to be returned.  The post_process function drops values
55       by returning NULL, which will cause OSSL_STORE_load() to start its
56       process over with loading the next object, until post_process returns
57       something other than NULL, or the end of data is reached as indicated
58       by OSSL_STORE_eof().
59
60       OSSL_STORE_ctrl() takes a OSSL_STORE_CTX, and command number cmd and
61       more arguments not specified here.  The available loader specific
62       command numbers and arguments they each take depends on the loader
63       that's used and is documented together with that loader.
64
65       There are also global controls available:
66
67       OSSL_STORE_C_USE_SECMEM
68           Controls if the loader should attempt to use secure memory for any
69           allocated OSSL_STORE_INFO and its contents.  This control expects
70           one argument, a pointer to an int that is expected to have the
71           value 1 (yes) or 0 (no).  Any other value is an error.
72
73       OSSL_STORE_load() takes a OSSL_STORE_CTX, tries to load the next
74       available object and return it wrapped with  OSSL_STORE_INFO.
75
76       OSSL_STORE_eof() takes a OSSL_STORE_CTX and checks if we've reached the
77       end of data.
78
79       OSSL_STORE_error() takes a OSSL_STORE_CTX and checks if an error
80       occurred in the last OSSL_STORE_load() call.  Note that it may still be
81       meaningful to try and load more objects, unless OSSL_STORE_eof() shows
82       that the end of data has been reached.
83
84       OSSL_STORE_close() takes a OSSL_STORE_CTX, closes the channel that was
85       opened by OSSL_STORE_open() and frees all other information that was
86       stored in the OSSL_STORE_CTX, as well as the OSSL_STORE_CTX itself.  If
87       ctx is NULL it does nothing.
88

SUPPORTED SCHEMES

90       The basic supported scheme is file:.  Any other scheme can be added
91       dynamically, using OSSL_STORE_register_loader().
92

NOTES

94       A string without a scheme prefix (that is, a non-URI string) is
95       implicitly interpreted as using the file: scheme.
96
97       There are some tools that can be used together with OSSL_STORE_open()
98       to determine if any failure is caused by an unparsable URI, or if it's
99       a different error (such as memory allocation failures); if the URI was
100       parsable but the scheme unregistered, the top error will have the
101       reason "OSSL_STORE_R_UNREGISTERED_SCHEME".
102
103       These functions make no direct assumption regarding the pass phrase
104       received from the password callback.  The loaders may make assumptions,
105       however.  For example, the file: scheme loader inherits the assumptions
106       made by OpenSSL functionality that handles the different file types;
107       this is mostly relevant for PKCS#12 objects.  See
108       passphrase-encoding(7) for further information.
109

RETURN VALUES

111       OSSL_STORE_open() returns a pointer to a OSSL_STORE_CTX on success, or
112       NULL on failure.
113
114       OSSL_STORE_load() returns a pointer to a OSSL_STORE_INFO on success, or
115       NULL on error or when end of data is reached.  Use OSSL_STORE_error()
116       and OSSL_STORE_eof() to determine the meaning of a returned NULL.
117
118       OSSL_STORE_eof() returns 1 if the end of data has been reached,
119       otherwise 0.
120
121       OSSL_STORE_error() returns 1 if an error occurred in an
122       OSSL_STORE_load() call, otherwise 0.
123
124       OSSL_STORE_ctrl() and OSSL_STORE_close() returns 1 on success, or 0 on
125       failure.
126

SEE ALSO

128       ossl_store(7), OSSL_STORE_INFO(3), OSSL_STORE_register_loader(3),
129       passphrase-encoding(7)
130

HISTORY

132       OSSL_STORE_CTX(), OSSL_STORE_post_process_info_fn(), OSSL_STORE_open(),
133       OSSL_STORE_ctrl(), OSSL_STORE_load(), OSSL_STORE_eof() and
134       OSSL_STORE_close() were added in OpenSSL 1.1.1.
135
136       Handling of NULL ctx argument for OSSL_STORE_close() was introduced in
137       OpenSSL 1.1.1h.
138
140       Copyright 2016-2020 The OpenSSL Project Authors. All Rights Reserved.
141
142       Licensed under the OpenSSL license (the "License").  You may not use
143       this file except in compliance with the License.  You can obtain a copy
144       in the file LICENSE in the source distribution or at
145       <https://www.openssl.org/source/license.html>.
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1491.1.1k                            2021-03-26                OSSL_STORE_OPEN(3)
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