1=pod 2 3=head1 NAME 4 5provider-encoder - The OSSL_ENCODER library E<lt>-E<gt> provider functions 6 7=head1 SYNOPSIS 8 9 #include <openssl/core_dispatch.h> 10 11 /* 12 * None of these are actual functions, but are displayed like this for 13 * the function signatures for functions that are offered as function 14 * pointers in OSSL_DISPATCH arrays. 15 */ 16 17 /* Encoder parameter accessor and descriptor */ 18 const OSSL_PARAM *OSSL_FUNC_encoder_gettable_params(void *provctx); 19 int OSSL_FUNC_encoder_get_params(OSSL_PARAM params[]); 20 21 /* Functions to construct / destruct / manipulate the encoder context */ 22 void *OSSL_FUNC_encoder_newctx(void *provctx); 23 void OSSL_FUNC_encoder_freectx(void *ctx); 24 int OSSL_FUNC_encoder_set_ctx_params(void *ctx, const OSSL_PARAM params[]); 25 const OSSL_PARAM *OSSL_FUNC_encoder_settable_ctx_params(void *provctx); 26 27 /* Functions to check selection support */ 28 int OSSL_FUNC_encoder_does_selection(void *provctx, int selection); 29 30 /* Functions to encode object data */ 31 int OSSL_FUNC_encoder_encode(void *ctx, OSSL_CORE_BIO *out, 32 const void *obj_raw, 33 const OSSL_PARAM obj_abstract[], 34 int selection, 35 OSSL_PASSPHRASE_CALLBACK *cb, 36 void *cbarg); 37 38 /* Functions to import and free a temporary object to be encoded */ 39 void *OSSL_FUNC_encoder_import_object(void *ctx, int selection, 40 const OSSL_PARAM params[]); 41 void OSSL_FUNC_encoder_free_object(void *obj); 42 43 44=head1 DESCRIPTION 45 46I<We use the wide term "encode" in this manual. This includes but is 47not limited to serialization.> 48 49The ENCODER operation is a generic method to encode a provider-native 50object (I<obj_raw>) or an object abstraction (I<object_abstract>, see 51L<provider-object(7)>) into an encoded form, and write the result to 52the given OSSL_CORE_BIO. If the caller wants to get the encoded 53stream to memory, it should provide a L<BIO_s_mem(3)> B<BIO>. 54 55The encoder doesn't need to know more about the B<OSSL_CORE_BIO> 56pointer than being able to pass it to the appropriate BIO upcalls (see 57L<provider-base(7)/Core functions>). 58 59The ENCODER implementation may be part of a chain, where data is 60passed from one to the next. For example, there may be an 61implementation to encode an object to DER (that object is assumed to 62be provider-native and thereby passed via I<obj_raw>), and another one 63that encodes DER to PEM (that one would receive the DER encoding via 64I<obj_abstract>). 65 66=begin comment 67 68Having the DER encoding passed via I<obj_abstract> may seem 69complicated. However, there may be associated meta-data, such as the 70original data type, that need to be passed alongside it, and since 71L<provider-object(7)> already defines a way to pass such data, 72inventing another way to do it makes things even more complicated. 73 74=end comment 75 76The encoding using the L<OSSL_PARAM(3)> array form allows a 77encoder to be used for data that's been exported from another 78provider, and thereby allow them to exist independently of each 79other. 80 81The encoding using a provider side object can only be safely used 82with provider data coming from the same provider, for example keys 83with the L<KEYMGMT|provider-keymgmt(7)> provider. 84 85All "functions" mentioned here are passed as function pointers between 86F<libcrypto> and the provider in L<OSSL_DISPATCH(3)> arrays via 87L<OSSL_ALGORITHM(3)> arrays that are returned by the provider's 88provider_query_operation() function 89(see L<provider-base(7)/Provider Functions>). 90 91All these "functions" have a corresponding function type definition 92named B<OSSL_FUNC_{name}_fn>, and a helper function to retrieve the 93function pointer from an L<OSSL_DISPATCH(3)> element named 94B<OSSL_FUNC_{name}>. 95For example, the "function" OSSL_FUNC_encoder_encode() has these: 96 97 typedef int 98 (OSSL_FUNC_encoder_encode_fn)(void *ctx, OSSL_CORE_BIO *out, 99 const void *obj_raw, 100 const OSSL_PARAM obj_abstract[], 101 int selection, 102 OSSL_PASSPHRASE_CALLBACK *cb, void *cbarg); 103 static ossl_inline OSSL_FUNC_encoder_encode_fn 104 OSSL_FUNC_encoder_encode(const OSSL_DISPATCH *opf); 105 106L<OSSL_DISPATCH(3)> arrays are indexed by numbers that are provided as 107macros in L<openssl-core_dispatch.h(7)>, as follows: 108 109 OSSL_FUNC_encoder_get_params OSSL_FUNC_ENCODER_GET_PARAMS 110 OSSL_FUNC_encoder_gettable_params OSSL_FUNC_ENCODER_GETTABLE_PARAMS 111 112 OSSL_FUNC_encoder_newctx OSSL_FUNC_ENCODER_NEWCTX 113 OSSL_FUNC_encoder_freectx OSSL_FUNC_ENCODER_FREECTX 114 OSSL_FUNC_encoder_set_ctx_params OSSL_FUNC_ENCODER_SET_CTX_PARAMS 115 OSSL_FUNC_encoder_settable_ctx_params OSSL_FUNC_ENCODER_SETTABLE_CTX_PARAMS 116 117 OSSL_FUNC_encoder_does_selection OSSL_FUNC_ENCODER_DOES_SELECTION 118 119 OSSL_FUNC_encoder_encode OSSL_FUNC_ENCODER_ENCODE 120 121 OSSL_FUNC_encoder_import_object OSSL_FUNC_ENCODER_IMPORT_OBJECT 122 OSSL_FUNC_encoder_free_object OSSL_FUNC_ENCODER_FREE_OBJECT 123 124=head2 Names and properties 125 126The name of an implementation should match the type of object it handles. 127For example, an implementation that encodes an RSA key should be named "RSA". 128Likewise, an implementation that further encodes DER should be named "DER". 129 130Properties can be used to further specify details about an implementation: 131 132=over 4 133 134=item output 135 136This property is used to specify what type of output the implementation 137produces. 138 139This property is I<mandatory>. 140 141OpenSSL providers recognize the following output types: 142 143=over 4 144 145=item text 146 147An implementation with that output type outputs human readable text, making 148that implementation suitable for C<-text> output in diverse L<openssl(1)> 149commands. 150 151=item pem 152 153An implementation with that output type outputs PEM formatted data. 154 155=item der 156 157An implementation with that output type outputs DER formatted data. 158 159=item msblob 160 161An implementation with that output type outputs MSBLOB formatted data. 162 163=item pvk 164 165An implementation with that output type outputs PVK formatted data. 166 167=back 168 169=item structure 170 171This property is used to specify the structure that is used for the encoded 172object. An example could be C<pkcs8>, to specify explicitly that an object 173(presumably an asymmetric key pair, in this case) will be wrapped in a 174PKCS#8 structure as part of the encoding. 175 176This property is I<optional>. 177 178=back 179 180The possible values of both these properties is open ended. A provider may 181very well specify output types and structures that libcrypto doesn't know 182anything about. 183 184=head2 Subset selections 185 186Sometimes, an object has more than one subset of data that is interesting to 187treat separately or together. It's possible to specify what subsets are to 188be encoded, with a set of bits I<selection> that are passed in an B<int>. 189 190This set of bits depend entirely on what kind of provider-side object is 191passed. For example, those bits are assumed to be the same as those used 192with L<provider-keymgmt(7)> (see L<provider-keymgmt(7)/Key Objects>) when 193the object is an asymmetric keypair. 194 195ENCODER implementations are free to regard the I<selection> as a set of 196hints, but must do so with care. In the end, the output must make sense, 197and if there's a corresponding decoder, the resulting decoded object must 198match the original object that was encoded. 199 200OSSL_FUNC_encoder_does_selection() should tell if a particular implementation 201supports any of the combinations given by I<selection>. 202 203=head2 Context functions 204 205OSSL_FUNC_encoder_newctx() returns a context to be used with the rest of 206the functions. 207 208OSSL_FUNC_encoder_freectx() frees the given I<ctx>, if it was created by 209OSSL_FUNC_encoder_newctx(). 210 211OSSL_FUNC_encoder_set_ctx_params() sets context data according to parameters 212from I<params> that it recognises. Unrecognised parameters should be 213ignored. 214Passing NULL for I<params> should return true. 215 216OSSL_FUNC_encoder_settable_ctx_params() returns a constant L<OSSL_PARAM(3)> 217array describing the parameters that OSSL_FUNC_encoder_set_ctx_params() 218can handle. 219 220See L<OSSL_PARAM(3)> for further details on the parameters structure used by 221OSSL_FUNC_encoder_set_ctx_params() and OSSL_FUNC_encoder_settable_ctx_params(). 222 223=head2 Import functions 224 225A provider-native object may be associated with a foreign provider, and may 226therefore be unsuitable for direct use with a given ENCODER implementation. 227Provided that the foreign provider's implementation to handle the object has 228a function to export that object in L<OSSL_PARAM(3)> array form, the ENCODER 229implementation should be able to import that array and create a suitable 230object to be passed to OSSL_FUNC_encoder_encode()'s I<obj_raw>. 231 232OSSL_FUNC_encoder_import_object() should import the subset of I<params> 233given with I<selection> to create a provider-native object that can be 234passed as I<obj_raw> to OSSL_FUNC_encoder_encode(). 235 236OSSL_FUNC_encoder_free_object() should free the object that was created with 237OSSL_FUNC_encoder_import_object(). 238 239=head2 Encoding functions 240 241OSSL_FUNC_encoder_encode() should take a provider-native object (in 242I<obj_raw>) or an object abstraction (in I<obj_abstract>), and should output 243the object in encoded form to the B<OSSL_CORE_BIO>. The I<selection> bits, 244if relevant, should determine in greater detail what will be output. 245The encoding functions also take an L<OSSL_PASSPHRASE_CALLBACK(3)> function 246pointer along with a pointer to application data I<cbarg>, which should be 247used when a pass phrase prompt is needed. 248 249=head2 Encoder operation parameters 250 251Operation parameters currently recognised by built-in encoders are as 252follows: 253 254=over 4 255 256=item "cipher" (B<OSSL_ENCODER_PARAM_CIPHER>) <UTF8 string> 257 258The name of the encryption cipher to be used when generating encrypted 259encoding. This is used when encoding private keys, as well as 260other objects that need protection. 261 262If this name is invalid for the encoding implementation, the 263implementation should refuse to perform the encoding, i.e. 264OSSL_FUNC_encoder_encode_data() and OSSL_FUNC_encoder_encode_object() 265should return an error. 266 267=item "properties" (B<OSSL_ENCODER_PARAM_PROPERTIES>) <UTF8 string> 268 269The properties to be queried when trying to fetch the algorithm given 270with the "cipher" parameter. 271This must be given together with the "cipher" parameter to be 272considered valid. 273 274The encoding implementation isn't obligated to use this value. 275However, it is recommended that implementations that do not handle 276property strings return an error on receiving this parameter unless 277its value NULL or the empty string. 278 279=item "save-parameters" (B<OSSL_ENCODER_PARAM_SAVE_PARAMETERS>) <integer> 280 281If set to 0 disables saving of key domain parameters. Default is 1. 282It currently has an effect only on DSA keys. 283 284=back 285 286Parameters currently recognised by the built-in pass phrase callback: 287 288=over 4 289 290=item "info" (B<OSSL_PASSPHRASE_PARAM_INFO>) <UTF8 string> 291 292A string of information that will become part of the pass phrase 293prompt. This could be used to give the user information on what kind 294of object it's being prompted for. 295 296=back 297 298=head1 RETURN VALUES 299 300OSSL_FUNC_encoder_newctx() returns a pointer to a context, or NULL on 301failure. 302 303OSSL_FUNC_encoder_set_ctx_params() returns 1, unless a recognised 304parameter was invalid or caused an error, for which 0 is returned. 305 306OSSL_FUNC_encoder_settable_ctx_params() returns a pointer to an array of 307constant L<OSSL_PARAM(3)> elements. 308 309OSSL_FUNC_encoder_does_selection() returns 1 if the encoder implementation 310supports any of the I<selection> bits, otherwise 0. 311 312OSSL_FUNC_encoder_encode() returns 1 on success, or 0 on failure. 313 314=head1 SEE ALSO 315 316L<provider(7)> 317 318=head1 HISTORY 319 320The ENCODER interface was introduced in OpenSSL 3.0. 321 322=head1 COPYRIGHT 323 324Copyright 2019-2021 The OpenSSL Project Authors. All Rights Reserved. 325 326Licensed under the Apache License 2.0 (the "License"). You may not use 327this file except in compliance with the License. You can obtain a copy 328in the file LICENSE in the source distribution or at 329L<https://www.openssl.org/source/license.html>. 330 331=cut 332