xref: /openssl/doc/man3/OSSL_DECODER_CTX.pod (revision 1e4cef5f) 
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                                OSSL_LIB_CTX *libctx,
52                                const char *propq);
53 int OSSL_DECODER_CTX_get_num_decoders(OSSL_DECODER_CTX *ctx);
54
55 typedef struct ossl_decoder_instance_st OSSL_DECODER_INSTANCE;
56 OSSL_DECODER *
57 OSSL_DECODER_INSTANCE_get_decoder(OSSL_DECODER_INSTANCE *decoder_inst);
58 void *
59 OSSL_DECODER_INSTANCE_get_decoder_ctx(OSSL_DECODER_INSTANCE *decoder_inst);
60 const char *
61 OSSL_DECODER_INSTANCE_get_input_type(OSSL_DECODER_INSTANCE *decoder_inst);
62 OSSL_DECODER_INSTANCE_get_input_structure(OSSL_DECODER_INSTANCE *decoder_inst,
63                                           int *was_set);
64
65 typedef int OSSL_DECODER_CONSTRUCT(OSSL_DECODER_INSTANCE *decoder_inst,
66                                    const OSSL_PARAM *object,
67                                    void *construct_data);
68 typedef void OSSL_DECODER_CLEANUP(void *construct_data);
69
70 int OSSL_DECODER_CTX_set_construct(OSSL_DECODER_CTX *ctx,
71                                    OSSL_DECODER_CONSTRUCT *construct);
72 int OSSL_DECODER_CTX_set_construct_data(OSSL_DECODER_CTX *ctx,
73                                         void *construct_data);
74 int OSSL_DECODER_CTX_set_cleanup(OSSL_DECODER_CTX *ctx,
75                                  OSSL_DECODER_CLEANUP *cleanup);
76 OSSL_DECODER_CONSTRUCT *OSSL_DECODER_CTX_get_construct(OSSL_DECODER_CTX *ctx);
77 void *OSSL_DECODER_CTX_get_construct_data(OSSL_DECODER_CTX *ctx);
78 OSSL_DECODER_CLEANUP *OSSL_DECODER_CTX_get_cleanup(OSSL_DECODER_CTX *ctx);
79
80 int OSSL_DECODER_export(OSSL_DECODER_INSTANCE *decoder_inst,
81                         void *reference, size_t reference_sz,
82                         OSSL_CALLBACK *export_cb, void *export_cbarg);
83
84=head1 DESCRIPTION
85
86The B<OSSL_DECODER_CTX> holds data about multiple decoders, as needed to
87figure out what the input data is and to attempt to unpack it into one of
88several possible related results.  This also includes chaining decoders, so
89the output from one can become the input for another.  This allows having
90generic format decoders such as PEM to DER, as well as more specialized
91decoders like DER to RSA.
92
93The chains may be limited by specifying an input type, which is considered a
94starting point.  This is both considered by OSSL_DECODER_CTX_add_extra(),
95which will stop adding one more decoder implementations when it has already
96added those that take the specified input type, and functions like
97L<OSSL_DECODER_from_bio(3)>, which will only start the decoding process with
98the decoder implementations that take that input type.  For example, if the
99input type is set to C<DER>, a PEM to DER decoder will be ignored.
100
101The input type can also be NULL, which means that the caller doesn't know
102what type of input they have.  In this case, OSSL_DECODER_from_bio() will
103simply try with one decoder implementation after the other, and thereby
104discover what kind of input the caller gave it.
105
106For every decoding done, even an intermediary one, a constructor provided by
107the caller is called to attempt to construct an appropriate type / structure
108that the caller knows how to handle from the current decoding result.
109The constructor is set with OSSL_DECODER_CTX_set_construct().
110
111B<OSSL_DECODER_INSTANCE> is an opaque structure that contains data about the
112decoder that was just used, and that may be useful for the constructor.
113There are some functions to extract data from this type, described further
114down.
115
116=head2 Functions
117
118OSSL_DECODER_CTX_new() creates a new empty B<OSSL_DECODER_CTX>.
119
120OSSL_DECODER_settable_ctx_params() returns an L<OSSL_PARAM(3)> array of
121parameter descriptors.
122
123OSSL_DECODER_CTX_set_params() attempts to set parameters specified with an
124L<OSSL_PARAM(3)> array I<params>.  These parameters are passed to all
125decoders that have been added to the I<ctx> so far.  Parameters that an
126implementation doesn't recognise should be ignored by it.
127
128OSSL_DECODER_CTX_free() frees the given context I<ctx>.
129
130OSSL_DECODER_CTX_add_decoder() populates the B<OSSL_DECODER_CTX> I<ctx> with
131a decoder, to be used to attempt to decode some encoded input.
132
133OSSL_DECODER_CTX_add_extra() finds decoders that generate input for already
134added decoders, and adds them as well.  This is used to build decoder
135chains.
136
137OSSL_DECODER_CTX_set_input_type() sets the starting input type.  This limits
138the decoder chains to be considered, as explained in the general description
139above.
140
141OSSL_DECODER_CTX_set_input_structure() sets the name of the structure that
142the input is expected to have.  This may be used to determines what decoder
143implementations may be used.  NULL is a valid input structure, when it's not
144relevant, or when the decoder implementations are expected to figure it out.
145
146OSSL_DECODER_CTX_get_num_decoders() gets the number of decoders currently
147added to the context I<ctx>.
148
149OSSL_DECODER_CTX_set_construct() sets the constructor I<construct>.
150
151OSSL_DECODER_CTX_set_construct_data() sets the constructor data that is
152passed to the constructor every time it's called.
153
154OSSL_DECODER_CTX_set_cleanup() sets the constructor data I<cleanup>
155function.  This is called by L<OSSL_DECODER_CTX_free(3)>.
156
157OSSL_DECODER_CTX_get_construct(), OSSL_DECODER_CTX_get_construct_data() and
158OSSL_DECODER_CTX_get_cleanup() return the values that have been set by
159OSSL_DECODER_CTX_set_construct(), OSSL_DECODER_CTX_set_construct_data() and
160OSSL_DECODER_CTX_set_cleanup() respectively.
161
162OSSL_DECODER_export() is a fallback function for constructors that cannot
163use the data they get directly for diverse reasons.  It takes the same
164decode instance I<decoder_inst> that the constructor got and an object
165I<reference>, unpacks the object which it refers to, and exports it by
166creating an L<OSSL_PARAM(3)> array that it then passes to I<export_cb>,
167along with I<export_arg>.
168
169=head2 Constructor
170
171A B<OSSL_DECODER_CONSTRUCT> gets the following arguments:
172
173=over 4
174
175=item I<decoder_inst>
176
177The B<OSSL_DECODER_INSTANCE> for the decoder from which the constructor gets
178its data.
179
180=item I<object>
181
182A provider-native object abstraction produced by the decoder.  Further
183information on the provider-native object abstraction can be found in
184L<provider-object(7)>.
185
186=item I<construct_data>
187
188The pointer that was set with OSSL_DECODE_CTX_set_construct_data().
189
190=back
191
192The constructor is expected to return 1 when the data it receives can be
193constructed, otherwise 0.
194
195These utility functions may be used by a constructor:
196
197OSSL_DECODER_INSTANCE_get_decoder() can be used to get the decoder
198implementation from a decoder instance I<decoder_inst>.
199
200OSSL_DECODER_INSTANCE_get_decoder_ctx() can be used to get the decoder
201implementation's provider context from a decoder instance I<decoder_inst>.
202
203OSSL_DECODER_INSTANCE_get_input_type() can be used to get the decoder
204implementation's input type from a decoder instance I<decoder_inst>.
205
206OSSL_DECODER_INSTANCE_get_input_structure() can be used to get the input
207structure for the decoder implementation from a decoder instance
208I<decoder_inst>.
209This may be NULL.
210
211=head1 RETURN VALUES
212
213OSSL_DECODER_CTX_new() returns a pointer to a B<OSSL_DECODER_CTX>, or NULL
214if the context structure couldn't be allocated.
215
216OSSL_DECODER_settable_ctx_params() returns an L<OSSL_PARAM(3)> array, or
217NULL if none is available.
218
219OSSL_DECODER_CTX_set_params() returns 1 if all recognised parameters were
220valid, or 0 if one of them was invalid or caused some other failure in the
221implementation.
222
223OSSL_DECODER_CTX_add_decoder(), OSSL_DECODER_CTX_add_extra(),
224OSSL_DECODER_CTX_set_construct(), OSSL_DECODER_CTX_set_construct_data() and
225OSSL_DECODER_CTX_set_cleanup() return 1 on success, or 0 on failure.
226
227OSSL_DECODER_CTX_get_construct(), OSSL_DECODER_CTX_get_construct_data() and
228OSSL_DECODER_CTX_get_cleanup() return the current pointers to the
229constructor, the constructor data and the cleanup functions, respectively.
230
231OSSL_DECODER_CTX_num_decoders() returns the current number of decoders.  It
232returns 0 if I<ctx> is NULL.
233
234OSSL_DECODER_export() returns 1 on success, or 0 on failure.
235
236OSSL_DECODER_INSTANCE_decoder() returns an B<OSSL_DECODER> pointer on
237success, or NULL on failure.
238
239OSSL_DECODER_INSTANCE_decoder_ctx() returns a provider context pointer on
240success, or NULL on failure.
241
242=head1 SEE ALSO
243
244L<provider(7)>, L<OSSL_DECODER(3)>, L<OSSL_DECODER_from_bio(3)>
245
246=head1 HISTORY
247
248The functions described here were added in OpenSSL 3.0.
249
250=head1 COPYRIGHT
251
252Copyright 2020 The OpenSSL Project Authors. All Rights Reserved.
253
254Licensed under the Apache License 2.0 (the "License").  You may not use
255this file except in compliance with the License.  You can obtain a copy
256in the file LICENSE in the source distribution or at
257L<https://www.openssl.org/source/license.html>.
258
259=cut
260