1=pod
2
3=head1 NAME
4
5OSSL_DECODER_CTX,
6OSSL_DECODER_CTX_new,
7OSSL_DECODER_settable_ctx_params,
8OSSL_DECODER_CTX_set_params,
9OSSL_DECODER_CTX_free,
10OSSL_DECODER_CTX_set_selection,
11OSSL_DECODER_CTX_set_input_type,
12OSSL_DECODER_CTX_set_input_structure,
13OSSL_DECODER_CTX_add_decoder,
14OSSL_DECODER_CTX_add_extra,
15OSSL_DECODER_CTX_get_num_decoders,
16OSSL_DECODER_INSTANCE,
17OSSL_DECODER_CONSTRUCT,
18OSSL_DECODER_CLEANUP,
19OSSL_DECODER_CTX_set_construct,
20OSSL_DECODER_CTX_set_construct_data,
21OSSL_DECODER_CTX_set_cleanup,
22OSSL_DECODER_CTX_get_construct,
23OSSL_DECODER_CTX_get_construct_data,
24OSSL_DECODER_CTX_get_cleanup,
25OSSL_DECODER_export,
26OSSL_DECODER_INSTANCE_get_decoder,
27OSSL_DECODER_INSTANCE_get_decoder_ctx,
28OSSL_DECODER_INSTANCE_get_input_type,
29OSSL_DECODER_INSTANCE_get_input_structure
30- Decoder context routines
31
32=head1 SYNOPSIS
33
34 #include <openssl/decoder.h>
35
36 typedef struct ossl_decoder_ctx_st OSSL_DECODER_CTX;
37
38 OSSL_DECODER_CTX *OSSL_DECODER_CTX_new(void);
39 const OSSL_PARAM *OSSL_DECODER_settable_ctx_params(OSSL_DECODER *decoder);
40 int OSSL_DECODER_CTX_set_params(OSSL_DECODER_CTX *ctx,
41                                 const OSSL_PARAM params[]);
42 void OSSL_DECODER_CTX_free(OSSL_DECODER_CTX *ctx);
43
44 int OSSL_DECODER_CTX_set_selection(OSSL_DECODER_CTX *ctx, int selection);
45 int OSSL_DECODER_CTX_set_input_type(OSSL_DECODER_CTX *ctx,
46                                     const char *input_type);
47 int OSSL_DECODER_CTX_set_input_structure(OSSL_DECODER_CTX *ctx,
48                                          const char *input_structure);
49 int OSSL_DECODER_CTX_add_decoder(OSSL_DECODER_CTX *ctx, OSSL_DECODER *decoder);
50 int OSSL_DECODER_CTX_add_extra(OSSL_DECODER_CTX *ctx);
51 int OSSL_DECODER_CTX_get_num_decoders(OSSL_DECODER_CTX *ctx);
52
53 typedef struct ossl_decoder_instance_st OSSL_DECODER_INSTANCE;
54 OSSL_DECODER *
55 OSSL_DECODER_INSTANCE_get_decoder(OSSL_DECODER_INSTANCE *decoder_inst);
56 void *
57 OSSL_DECODER_INSTANCE_get_decoder_ctx(OSSL_DECODER_INSTANCE *decoder_inst);
58 const char *
59 OSSL_DECODER_INSTANCE_get_input_type(OSSL_DECODER_INSTANCE *decoder_inst);
60 OSSL_DECODER_INSTANCE_get_input_structure(OSSL_DECODER_INSTANCE *decoder_inst,
61                                           int *was_set);
62
63 typedef int OSSL_DECODER_CONSTRUCT(OSSL_DECODER_INSTANCE *decoder_inst,
64                                    const OSSL_PARAM *object,
65                                    void *construct_data);
66 typedef void OSSL_DECODER_CLEANUP(void *construct_data);
67
68 int OSSL_DECODER_CTX_set_construct(OSSL_DECODER_CTX *ctx,
69                                    OSSL_DECODER_CONSTRUCT *construct);
70 int OSSL_DECODER_CTX_set_construct_data(OSSL_DECODER_CTX *ctx,
71                                         void *construct_data);
72 int OSSL_DECODER_CTX_set_cleanup(OSSL_DECODER_CTX *ctx,
73                                  OSSL_DECODER_CLEANUP *cleanup);
74 OSSL_DECODER_CONSTRUCT *OSSL_DECODER_CTX_get_construct(OSSL_DECODER_CTX *ctx);
75 void *OSSL_DECODER_CTX_get_construct_data(OSSL_DECODER_CTX *ctx);
76 OSSL_DECODER_CLEANUP *OSSL_DECODER_CTX_get_cleanup(OSSL_DECODER_CTX *ctx);
77
78 int OSSL_DECODER_export(OSSL_DECODER_INSTANCE *decoder_inst,
79                         void *reference, size_t reference_sz,
80                         OSSL_CALLBACK *export_cb, void *export_cbarg);
81
82=head1 DESCRIPTION
83
84The B<OSSL_DECODER_CTX> holds data about multiple decoders, as needed to
85figure out what the input data is and to attempt to unpack it into one of
86several possible related results.  This also includes chaining decoders, so
87the output from one can become the input for another.  This allows having
88generic format decoders such as PEM to DER, as well as more specialized
89decoders like DER to RSA.
90
91The chains may be limited by specifying an input type, which is considered a
92starting point.  This is both considered by OSSL_DECODER_CTX_add_extra(),
93which will stop adding one more decoder implementations when it has already
94added those that take the specified input type, and functions like
95L<OSSL_DECODER_from_bio(3)>, which will only start the decoding process with
96the decoder implementations that take that input type.  For example, if the
97input type is set to C<DER>, a PEM to DER decoder will be ignored.
98
99The input type can also be NULL, which means that the caller doesn't know
100what type of input they have.  In this case, OSSL_DECODER_from_bio() will
101simply try with one decoder implementation after the other, and thereby
102discover what kind of input the caller gave it.
103
104For every decoding done, even an intermediary one, a constructor provided by
105the caller is called to attempt to construct an appropriate type / structure
106that the caller knows how to handle from the current decoding result.
107The constructor is set with OSSL_DECODER_CTX_set_construct().
108
109B<OSSL_DECODER_INSTANCE> is an opaque structure that contains data about the
110decoder that was just used, and that may be useful for the constructor.
111There are some functions to extract data from this type, described further
112down.
113
114=head2 Functions
115
116OSSL_DECODER_CTX_new() creates a new empty B<OSSL_DECODER_CTX>.
117
118OSSL_DECODER_settable_ctx_params() returns an L<OSSL_PARAM(3)> array of
119parameter descriptors.
120
121OSSL_DECODER_CTX_set_params() attempts to set parameters specified with an
122L<OSSL_PARAM(3)> array I<params>.  These parameters are passed to all
123decoders that have been added to the I<ctx> so far.  Parameters that an
124implementation doesn't recognise should be ignored by it.
125
126OSSL_DECODER_CTX_free() frees the given context I<ctx>.
127
128OSSL_DECODER_CTX_add_decoder() populates the B<OSSL_DECODER_CTX> I<ctx> with
129a decoder, to be used to attempt to decode some encoded input.
130
131OSSL_DECODER_CTX_add_extra() finds decoders that generate input for already
132added decoders, and adds them as well.  This is used to build decoder
133chains.
134
135OSSL_DECODER_CTX_set_input_type() sets the starting input type.  This limits
136the decoder chains to be considered, as explained in the general description
137above.
138
139OSSL_DECODER_CTX_set_input_structure() sets the name of the structure that
140the input is expected to have.  This may be used to determines what decoder
141implementations may be used.  NULL is a valid input structure, when it's not
142relevant, or when the decoder implementations are expected to figure it out.
143
144OSSL_DECODER_CTX_get_num_decoders() gets the number of decoders currently
145added to the context I<ctx>.
146
147OSSL_DECODER_CTX_set_construct() sets the constructor I<construct>.
148
149OSSL_DECODER_CTX_set_construct_data() sets the constructor data that is
150passed to the constructor every time it's called.
151
152OSSL_DECODER_CTX_set_cleanup() sets the constructor data I<cleanup>
153function.  This is called by L<OSSL_DECODER_CTX_free(3)>.
154
155OSSL_DECODER_CTX_get_construct(), OSSL_DECODER_CTX_get_construct_data() and
156OSSL_DECODER_CTX_get_cleanup() return the values that have been set by
157OSSL_DECODER_CTX_set_construct(), OSSL_DECODER_CTX_set_construct_data() and
158OSSL_DECODER_CTX_set_cleanup() respectively.
159
160OSSL_DECODER_export() is a fallback function for constructors that cannot
161use the data they get directly for diverse reasons.  It takes the same
162decode instance I<decoder_inst> that the constructor got and an object
163I<reference>, unpacks the object which it refers to, and exports it by
164creating an L<OSSL_PARAM(3)> array that it then passes to I<export_cb>,
165along with I<export_arg>.
166
167=head2 Constructor
168
169A B<OSSL_DECODER_CONSTRUCT> gets the following arguments:
170
171=over 4
172
173=item I<decoder_inst>
174
175The B<OSSL_DECODER_INSTANCE> for the decoder from which the constructor gets
176its data.
177
178=item I<object>
179
180A provider-native object abstraction produced by the decoder.  Further
181information on the provider-native object abstraction can be found in
182L<provider-object(7)>.
183
184=item I<construct_data>
185
186The pointer that was set with OSSL_DECODE_CTX_set_construct_data().
187
188=back
189
190The constructor is expected to return 1 when the data it receives can be
191constructed, otherwise 0.
192
193These utility functions may be used by a constructor:
194
195OSSL_DECODER_INSTANCE_get_decoder() can be used to get the decoder
196implementation from a decoder instance I<decoder_inst>.
197
198OSSL_DECODER_INSTANCE_get_decoder_ctx() can be used to get the decoder
199implementation's provider context from a decoder instance I<decoder_inst>.
200
201OSSL_DECODER_INSTANCE_get_input_type() can be used to get the decoder
202implementation's input type from a decoder instance I<decoder_inst>.
203
204OSSL_DECODER_INSTANCE_get_input_structure() can be used to get the input
205structure for the decoder implementation from a decoder instance
206I<decoder_inst>.
207This may be NULL.
208
209=head1 RETURN VALUES
210
211OSSL_DECODER_CTX_new() returns a pointer to a B<OSSL_DECODER_CTX>, or NULL
212if the context structure couldn't be allocated.
213
214OSSL_DECODER_settable_ctx_params() returns an L<OSSL_PARAM(3)> array, or
215NULL if none is available.
216
217OSSL_DECODER_CTX_set_params() returns 1 if all recognised parameters were
218valid, or 0 if one of them was invalid or caused some other failure in the
219implementation.
220
221OSSL_DECODER_CTX_add_decoder(), OSSL_DECODER_CTX_add_extra(),
222OSSL_DECODER_CTX_set_construct(), OSSL_DECODER_CTX_set_construct_data() and
223OSSL_DECODER_CTX_set_cleanup() return 1 on success, or 0 on failure.
224
225OSSL_DECODER_CTX_get_construct(), OSSL_DECODER_CTX_get_construct_data() and
226OSSL_DECODER_CTX_get_cleanup() return the current pointers to the
227constructor, the constructor data and the cleanup functions, respectively.
228
229OSSL_DECODER_CTX_num_decoders() returns the current number of decoders.  It
230returns 0 if I<ctx> is NULL.
231
232OSSL_DECODER_export() returns 1 on success, or 0 on failure.
233
234OSSL_DECODER_INSTANCE_decoder() returns an B<OSSL_DECODER> pointer on
235success, or NULL on failure.
236
237OSSL_DECODER_INSTANCE_decoder_ctx() returns a provider context pointer on
238success, or NULL on failure.
239
240=head1 SEE ALSO
241
242L<provider(7)>, L<OSSL_DECODER(3)>, L<OSSL_DECODER_from_bio(3)>
243
244=head1 HISTORY
245
246The functions described here were added in OpenSSL 3.0.
247
248=head1 COPYRIGHT
249
250Copyright 2020 The OpenSSL Project Authors. All Rights Reserved.
251
252Licensed under the Apache License 2.0 (the "License").  You may not use
253this file except in compliance with the License.  You can obtain a copy
254in the file LICENSE in the source distribution or at
255L<https://www.openssl.org/source/license.html>.
256
257=cut
258