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Title "PROVIDER-KDF 7" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
provider-kdf - The KDF library <-> provider functions Header "SYNOPSIS" .Vb 2 #include <openssl/core_dispatch.h> #include <openssl/core_names.h> \& /* * 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. */ \& /* Context management */ void *OSSL_FUNC_kdf_newctx(void *provctx); void OSSL_FUNC_kdf_freectx(void *kctx); void *OSSL_FUNC_kdf_dupctx(void *src); \& /* Encryption/decryption */ int OSSL_FUNC_kdf_reset(void *kctx); int OSSL_FUNC_kdf_derive(void *kctx, unsigned char *key, size_t keylen, const OSSL_PARAM params[]); \& /* KDF parameter descriptors */ const OSSL_PARAM *OSSL_FUNC_kdf_gettable_params(void *provctx); const OSSL_PARAM *OSSL_FUNC_kdf_gettable_ctx_params(void *kcxt, void *provctx); const OSSL_PARAM *OSSL_FUNC_kdf_settable_ctx_params(void *kcxt, void *provctx); \& /* KDF parameters */ int OSSL_FUNC_kdf_get_params(OSSL_PARAM params[]); int OSSL_FUNC_kdf_get_ctx_params(void *kctx, OSSL_PARAM params[]); int OSSL_FUNC_kdf_set_ctx_params(void *kctx, const OSSL_PARAM params[]); .Ve Header "DESCRIPTION" This documentation is primarily aimed at provider authors. See provider\|(7) for further information.

The \s-1KDF\s0 operation enables providers to implement \s-1KDF\s0 algorithms and make them available to applications via the \s-1API\s0 functions EVP_KDF_CTX_reset\|(3), and EVP_KDF_derive\|(3).

All \*(L"functions\*(R" mentioned here are passed as function pointers between \fIlibcrypto and the provider in \s-1OSSL_DISPATCH\s0\|(3) arrays via \s-1OSSL_ALGORITHM\s0\|(3) arrays that are returned by the provider's \fBprovider_query_operation() function (see \*(L"Provider Functions\*(R" in provider-base\|(7)).

All these \*(L"functions\*(R" have a corresponding function type definition named OSSL_FUNC_{name}_fn, and a helper function to retrieve the function pointer from an \s-1OSSL_DISPATCH\s0\|(3) element named \fBOSSL_FUNC_{name}. For example, the \*(L"function\*(R" OSSL_FUNC_kdf_newctx() has these:

.Vb 3 typedef void *(OSSL_FUNC_kdf_newctx_fn)(void *provctx); static ossl_inline OSSL_FUNC_kdf_newctx_fn OSSL_FUNC_kdf_newctx(const OSSL_DISPATCH *opf); .Ve

\s-1OSSL_DISPATCH\s0\|(3) array entries are identified by numbers that are provided as macros in openssl-core_dispatch.h\|(7), as follows:

.Vb 3 OSSL_FUNC_kdf_newctx OSSL_FUNC_KDF_NEWCTX OSSL_FUNC_kdf_freectx OSSL_FUNC_KDF_FREECTX OSSL_FUNC_kdf_dupctx OSSL_FUNC_KDF_DUPCTX \& OSSL_FUNC_kdf_reset OSSL_FUNC_KDF_RESET OSSL_FUNC_kdf_derive OSSL_FUNC_KDF_DERIVE \& OSSL_FUNC_kdf_get_params OSSL_FUNC_KDF_GET_PARAMS OSSL_FUNC_kdf_get_ctx_params OSSL_FUNC_KDF_GET_CTX_PARAMS OSSL_FUNC_kdf_set_ctx_params OSSL_FUNC_KDF_SET_CTX_PARAMS \& OSSL_FUNC_kdf_gettable_params OSSL_FUNC_KDF_GETTABLE_PARAMS OSSL_FUNC_kdf_gettable_ctx_params OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS OSSL_FUNC_kdf_settable_ctx_params OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS .Ve

A \s-1KDF\s0 algorithm implementation may not implement all of these functions. In order to be a consistent set of functions, at least the following functions must be implemented: OSSL_FUNC_kdf_newctx(), OSSL_FUNC_kdf_freectx(), \fBOSSL_FUNC_kdf_set_ctx_params(), OSSL_FUNC_kdf_derive(). All other functions are optional.

Subsection "Context Management Functions" \fBOSSL_FUNC_kdf_newctx() should create and return a pointer to a provider side structure for holding context information during a \s-1KDF\s0 operation. A pointer to this context will be passed back in a number of the other \s-1KDF\s0 operation function calls. The parameter provctx is the provider context generated during provider initialisation (see provider\|(7)).

\fBOSSL_FUNC_kdf_freectx() is passed a pointer to the provider side \s-1KDF\s0 context in the kctx parameter. If it receives \s-1NULL\s0 as kctx value, it should not do anything other than return. This function should free any resources associated with that context.

\fBOSSL_FUNC_kdf_dupctx() should duplicate the provider side \s-1KDF\s0 context in the \fIkctx parameter and return the duplicate copy.

Subsection "Encryption/Decryption Functions" \fBOSSL_FUNC_kdf_reset() initialises a \s-1KDF\s0 operation given a provider side \s-1KDF\s0 context in the kctx parameter.

\fBOSSL_FUNC_kdf_derive() performs the \s-1KDF\s0 operation after processing the \fIparams as per OSSL_FUNC_kdf_set_ctx_params(). The kctx parameter contains a pointer to the provider side context. The resulting key of the desired keylen should be written to key. If the algorithm does not support the requested keylen the function must return error.

Subsection "KDF Parameters" See \s-1OSSL_PARAM\s0\|(3) for further details on the parameters structure used by these functions.

\fBOSSL_FUNC_kdf_get_params() gets details of parameter values associated with the provider algorithm and stores them in params.

\fBOSSL_FUNC_kdf_set_ctx_params() sets \s-1KDF\s0 parameters associated with the given provider side \s-1KDF\s0 context kctx to params. Any parameter settings are additional to any that were previously set. Passing \s-1NULL\s0 for params should return true.

\fBOSSL_FUNC_kdf_get_ctx_params() retrieves gettable parameter values associated with the given provider side \s-1KDF\s0 context kctx and stores them in params. Passing \s-1NULL\s0 for params should return true.

\fBOSSL_FUNC_kdf_gettable_params(), OSSL_FUNC_kdf_gettable_ctx_params(), and OSSL_FUNC_kdf_settable_ctx_params() all return constant \s-1OSSL_PARAM\s0\|(3) arrays as descriptors of the parameters that OSSL_FUNC_kdf_get_params(), \fBOSSL_FUNC_kdf_get_ctx_params(), and OSSL_FUNC_kdf_set_ctx_params() can handle, respectively. OSSL_FUNC_kdf_gettable_ctx_params() and \fBOSSL_FUNC_kdf_settable_ctx_params() will return the parameters associated with the provider side context kctx in its current state if it is not \s-1NULL.\s0 Otherwise, they return the parameters associated with the provider side algorithm provctx.

Parameters currently recognised by built-in KDFs are as follows. Not all parameters are relevant to, or are understood by all KDFs: Item "size (OSSL_KDF_PARAM_SIZE) <unsigned integer>" Gets the output size from the associated \s-1KDF\s0 ctx. If the algorithm produces a variable amount of output, \s-1SIZE_MAX\s0 should be returned. If the input parameters required to calculate the fixed output size have not yet been supplied, 0 should be returned indicating an error. Item "key (OSSL_KDF_PARAM_KEY) <octet string>" Sets the key in the associated \s-1KDF\s0 ctx. Item "secret (OSSL_KDF_PARAM_SECRET) <octet string>" Sets the secret in the associated \s-1KDF\s0 ctx. Item "pass (OSSL_KDF_PARAM_PASSWORD) <octet string>" Sets the password in the associated \s-1KDF\s0 ctx. Item "cipher (OSSL_KDF_PARAM_CIPHER) <UTF8 string>"

0 Item "digest (OSSL_KDF_PARAM_DIGEST) <UTF8 string>" Item "mac (OSSL_KDF_PARAM_MAC) <UTF8 string>"

Sets the name of the underlying cipher, digest or \s-1MAC\s0 to be used. It must name a suitable algorithm for the \s-1KDF\s0 that's being used. Item "maclen (OSSL_KDF_PARAM_MAC_SIZE) <octet string>" Sets the length of the \s-1MAC\s0 in the associated \s-1KDF\s0 ctx. Item "properties (OSSL_KDF_PARAM_PROPERTIES) <UTF8 string>" Sets the properties to be queried when trying to fetch the underlying algorithm. This must be given together with the algorithm naming parameter to be considered valid. Item "iter (OSSL_KDF_PARAM_ITER) <unsigned integer>" Sets the number of iterations in the associated \s-1KDF\s0 ctx. Item "mode (OSSL_KDF_PARAM_MODE) <UTF8 string>" Sets the mode in the associated \s-1KDF\s0 ctx. Item "pkcs5 (OSSL_KDF_PARAM_PKCS5) <integer>" Enables or disables the \s-1SP800-132\s0 compliance checks. A mode of 0 enables the compliance checks. .Sp The checks performed are:

Item "ukm (OSSL_KDF_PARAM_UKM) <octet string>"

Sets an optional random string that is provided by the sender called \*(L"partyAInfo\*(R". In \s-1CMS\s0 this is the user keying material. Item "cekalg (OSSL_KDF_PARAM_CEK_ALG) <UTF8 string>" Sets the \s-1CEK\s0 wrapping algorithm name in the associated \s-1KDF\s0 ctx. Item "n (OSSL_KDF_PARAM_SCRYPT_N) <unsigned integer>" Sets the scrypt work factor parameter N in the associated \s-1KDF\s0 ctx. Item "r (OSSL_KDF_PARAM_SCRYPT_R) <unsigned integer>" Sets the scrypt work factor parameter r in the associated \s-1KDF\s0 ctx. Item "p (OSSL_KDF_PARAM_SCRYPT_P) <unsigned integer>" Sets the scrypt work factor parameter p in the associated \s-1KDF\s0 ctx. Item "maxmem_bytes (OSSL_KDF_PARAM_SCRYPT_MAXMEM) <unsigned integer>" Sets the scrypt work factor parameter maxmem in the associated \s-1KDF\s0 ctx. Item "prefix (OSSL_KDF_PARAM_PREFIX) <octet string>" Sets the prefix string using by the \s-1TLS 1.3\s0 version of \s-1HKDF\s0 in the associated \s-1KDF\s0 ctx. Item "label (OSSL_KDF_PARAM_LABEL) <octet string>" Sets the label string using by the \s-1TLS 1.3\s0 version of \s-1HKDF\s0 in the associated \s-1KDF\s0 ctx. Item "data (OSSL_KDF_PARAM_DATA) <octet string>" Sets the context string using by the \s-1TLS 1.3\s0 version of \s-1HKDF\s0 in the associated \s-1KDF\s0 ctx. Item "info (OSSL_KDF_PARAM_INFO) <octet string>" Sets the optional shared info in the associated \s-1KDF\s0 ctx. Item "seed (OSSL_KDF_PARAM_SEED) <octet string>" Sets the \s-1IV\s0 in the associated \s-1KDF\s0 ctx. Item "xcghash (OSSL_KDF_PARAM_SSHKDF_XCGHASH) <octet string>" Sets the xcghash in the associated \s-1KDF\s0 ctx. Item "session_id (OSSL_KDF_PARAM_SSHKDF_SESSION_ID) <octet string>" Sets the session \s-1ID\s0 in the associated \s-1KDF\s0 ctx. Item "type (OSSL_KDF_PARAM_SSHKDF_TYPE) <UTF8 string>" Sets the \s-1SSH KDF\s0 type parameter in the associated \s-1KDF\s0 ctx. There are six supported types:

Item "constant (OSSL_KDF_PARAM_CONSTANT) <octet string>" Sets the constant value in the associated \s-1KDF\s0 ctx. Item "id (OSSL_KDF_PARAM_PKCS12_ID) <integer>" Sets the intended usage of the output bits in the associated \s-1KDF\s0 ctx. It is defined as per \s-1RFC 7292\s0 section B.3. Header "RETURN VALUES" \fBOSSL_FUNC_kdf_newctx() and OSSL_FUNC_kdf_dupctx() should return the newly created provider side \s-1KDF\s0 context, or \s-1NULL\s0 on failure.

\fBOSSL_FUNC_kdf_derive(), OSSL_FUNC_kdf_get_params(), \fBOSSL_FUNC_kdf_get_ctx_params() and OSSL_FUNC_kdf_set_ctx_params() should return 1 for success or 0 on error.

\fBOSSL_FUNC_kdf_gettable_params(), OSSL_FUNC_kdf_gettable_ctx_params() and \fBOSSL_FUNC_kdf_settable_ctx_params() should return a constant \s-1OSSL_PARAM\s0\|(3) array, or \s-1NULL\s0 if none is offered.

Header "NOTES" The \s-1KDF\s0 life-cycle is described in life_cycle-kdf\|(7). Providers should ensure that the various transitions listed there are supported. At some point the \s-1EVP\s0 layer will begin enforcing the listed transitions. Header "SEE ALSO" \fBprovider\|(7), life_cycle-kdf\|(7), \s-1EVP_KDF\s0\|(3). Header "HISTORY" The provider \s-1KDF\s0 interface was introduced in OpenSSL 3.0. Header "COPYRIGHT" Copyright 2020-2023 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the Apache License 2.0 (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.