doc/man3/OSSL_DECODER_CTX.pod

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