=pod =head1 NAME provider-encoder - The ENCODER library E-E provider functions =head1 SYNOPSIS #include /* * None of these are actual functions, but are displayed like this for * the function signatures for functions that are offered as function * pointers in OSSL_DISPATCH arrays. */ /* Functions to construct / destruct / manipulate the encoder context */ void *OSSL_FUNC_encoder_newctx(void *provctx); void OSSL_FUNC_encoder_freectx(void *ctx); int OSSL_FUNC_encoder_set_ctx_params(void *ctx, const OSSL_PARAM params[]); const OSSL_PARAM *OSSL_FUNC_encoder_settable_ctx_params(void *provctx) /* Functions to encode object data */ int OSSL_FUNC_encoder_encode_data(void *ctx, const OSSL_PARAM *data, OSSL_CORE_BIO *out, OSSL_PASSPHRASE_CALLBACK *cb, void *cbarg); int OSSL_FUNC_encoder_encode_object(void *ctx, void *obj, OSSL_CORE_BIO *out, OSSL_PASSPHRASE_CALLBACK *cb, void *cbarg); =head1 DESCRIPTION I The ENCODER is a generic method to encode any set of object data in L array form, or any provider side object into encoded form, and write it to the given OSSL_CORE_BIO. If the caller wants to get the encoded stream to memory, it should provide a L. The encoder doesn't need to know more about the B pointer than being able to pass it to the appropriate BIO upcalls (see L). The encoding using the L array form allows a encoder to be used for data that's been exported from another provider, and thereby allow them to exist independently of each other. The encoding using a provider side object can only be safely used with provider data coming from the same provider, for example keys with the L provider. All "functions" mentioned here are passed as function pointers between F and the provider in B arrays via B arrays that are returned by the provider's provider_query_operation() function (see L). All these "functions" have a corresponding function type definition named B, and a helper function to retrieve the function pointer from a B element named B. For example, the "function" OSSL_FUNC_encoder_encode_data() has these: typedef int (OSSL_FUNC_encoder_encode_data_fn)(void *provctx, const OSSL_PARAM params[], OSSL_CORE_BIO *out); static ossl_inline OSSL_FUNC_encoder_encode_data_fn OSSL_FUNC_encoder_encode_data(const OSSL_DISPATCH *opf); B arrays are indexed by numbers that are provided as macros in L, as follows: OSSL_FUNC_encoder_newctx OSSL_FUNC_ENCODER_NEWCTX OSSL_FUNC_encoder_freectx OSSL_FUNC_ENCODER_FREECTX OSSL_FUNC_encoder_set_ctx_params OSSL_FUNC_ENCODER_SET_CTX_PARAMS OSSL_FUNC_encoder_settable_ctx_params OSSL_FUNC_ENCODER_SETTABLE_CTX_PARAMS OSSL_FUNC_encoder_encode_data OSSL_FUNC_ENCODER_ENCODE_DATA OSSL_FUNC_encoder_encode_object OSSL_FUNC_ENCODER_ENCODE_OBJECT =head2 Names and properties The name of an implementation should match the type of object it handles. For example, an implementation that encodes an RSA key should be named accordingly. To be able to specify exactly what encoding format and what type of data a encoder implementation is expected to handle, two additional properties may be given: =over 4 =item format This property is used to specify what kind of output format the implementation produces. Currently known formats are: =over 4 =item text An implementation with that format property value outputs human readable text, making that implementation suitable for C<-text> output in diverse L commands. =item pem An implementation with that format property value outputs PEM formatted data. =item der An implementation with that format property value outputs DER formatted data. =back =item type With objects that have multiple purposes, this can be used to specify the purpose type. The currently known use cases are asymmetric keys and key parameters, where the type can be one of: =over 4 =item private An implementation with that format property value outputs a private key. =item public An implementation with that format property value outputs a public key. =item parameters An implementation with that format property value outputs key parameters. =back =back The possible values of both these properties is open ended. A provider may very well specify other formats that libcrypto doesn't know anything about. =head2 Context functions OSSL_FUNC_encoder_newctx() returns a context to be used with the rest of the functions. OSSL_FUNC_encoder_freectx() frees the given I, if it was created by OSSL_FUNC_encoder_newctx(). OSSL_FUNC_encoder_set_ctx_params() sets context data according to parameters from I that it recognises. Unrecognised parameters should be ignored. OSSL_FUNC_encoder_settable_ctx_params() returns a constant B array describing the parameters that OSSL_FUNC_encoder_set_ctx_params() can handle. See L for further details on the parameters structure used by OSSL_FUNC_encoder_set_ctx_params() and OSSL_FUNC_encoder_settable_ctx_params(). =head2 Encoding functions =for comment There will be a "Decoding functions" title as well OSSL_FUNC_encoder_encode_data() should take an array of B, I, and if it contains the data necessary for the object type that the implementation handles, it should output the object in encoded form to the B. OSSL_FUNC_encoder_encode_object() should take a pointer to an object that it knows intimately, and output that object in encoded form to the B. The caller I ensure that this function is called with a pointer that the provider of this function is familiar with. It is not suitable to use with object pointers coming from other providers. Both encoding functions also take an B function pointer along with a pointer to application data I, which should be used when a pass phrase prompt is needed. =head2 Encoder parameters Parameters currently recognised by built-in encoders are as follows: =over 4 =item "cipher" (B) The name of the encryption cipher to be used when generating encrypted encoding. This is used when encoding private keys, as well as other objects that need protection. If this name is invalid for the encoding implementation, the implementation should refuse to perform the encoding, i.e. OSSL_FUNC_encoder_encode_data() and OSSL_FUNC_encoder_encode_object() should return an error. =item "properties" (B) The properties to be queried when trying to fetch the algorithm given with the "cipher" parameter. This must be given together with the "cipher" parameter to be considered valid. The encoding implementation isn't obligated to use this value. However, it is recommended that implementations that do not handle property strings return an error on receiving this parameter unless its value NULL or the empty string. =item "passphrase" (B) A pass phrase provided by the application. When this is given, the built-in encoders will not attempt to use the passphrase callback. =back Parameters currently recognised by the built-in pass phrase callback: =over 4 =item "info" (B) A string of information that will become part of the pass phrase prompt. This could be used to give the user information on what kind of object it's being prompted for. =back =head1 RETURN VALUES OSSL_FUNC_encoder_newctx() returns a pointer to a context, or NULL on failure. OSSL_FUNC_encoder_set_ctx_params() returns 1, unless a recognised parameters was invalid or caused an error, for which 0 is returned. OSSL_FUNC_encoder_settable_ctx_params() returns a pointer to an array of constant B elements. OSSL_FUNC_encoder_encode_data() and OSSL_FUNC_encoder_encode_object() return 1 on success, or 0 on failure. =head1 SEE ALSO L =head1 HISTORY The ENCODER interface was introduced in OpenSSL 3.0. =head1 COPYRIGHT Copyright 2019-2020 The OpenSSL Project Authors. All Rights Reserved. Licensed under the Apache License 2.0 (the "License"). You may not use this file except in compliance with the License. You can obtain a copy in the file LICENSE in the source distribution or at L. =cut