1PROVIDER-KEYEXCH(7ossl) OpenSSL PROVIDER-KEYEXCH(7ossl)
2
6 provider-keyexch - The keyexch library <-> provider functions
7
9 #include <openssl/core_dispatch.h>
10 #include <openssl/core_names.h>
11 /*
13 * None of these are actual functions, but are displayed like this for
14 * the function signatures for functions that are offered as function
15 * pointers in OSSL_DISPATCH arrays.
16 */
17 /* Context management */
19 void *OSSL_FUNC_keyexch_newctx(void *provctx);
20 void OSSL_FUNC_keyexch_freectx(void *ctx);
21 void *OSSL_FUNC_keyexch_dupctx(void *ctx);
22 /* Shared secret derivation */
24 int OSSL_FUNC_keyexch_init(void *ctx, void *provkey,
25 const OSSL_PARAM params[]);
26 int OSSL_FUNC_keyexch_set_peer(void *ctx, void *provkey);
27 int OSSL_FUNC_keyexch_derive(void *ctx, unsigned char *secret, size_t *secretlen,
28 size_t outlen);
29 /* Key Exchange parameters */
31 int OSSL_FUNC_keyexch_set_ctx_params(void *ctx, const OSSL_PARAM params[]);
32 const OSSL_PARAM *OSSL_FUNC_keyexch_settable_ctx_params(void *ctx,
33 void *provctx);
34 int OSSL_FUNC_keyexch_get_ctx_params(void *ctx, OSSL_PARAM params[]);
35 const OSSL_PARAM *OSSL_FUNC_keyexch_gettable_ctx_params(void *ctx,
36 void *provctx);
37
39 This documentation is primarily aimed at provider authors. See
40 provider(7) for further information.
41 The key exchange (OSSL_OP_KEYEXCH) operation enables providers to
43 implement key exchange algorithms and make them available to
44 applications via EVP_PKEY_derive(3) and other related functions).
45 All "functions" mentioned here are passed as function pointers between
47 libcrypto and the provider in OSSL_DISPATCH arrays via OSSL_ALGORITHM
48 arrays that are returned by the provider's provider_query_operation()
49 function (see "Provider Functions" in provider-base(7)).
50 All these "functions" have a corresponding function type definition
52 named OSSL_FUNC_{name}_fn, and a helper function to retrieve the
53 function pointer from an OSSL_DISPATCH element named OSSL_FUNC_{name}.
54 For example, the "function" OSSL_FUNC_keyexch_newctx() has these:
55 typedef void *(OSSL_FUNC_keyexch_newctx_fn)(void *provctx);
57 static ossl_inline OSSL_FUNC_keyexch_newctx_fn
58 OSSL_FUNC_keyexch_newctx(const OSSL_DISPATCH *opf);
59 OSSL_DISPATCH arrays are indexed by numbers that are provided as macros
61 in openssl-core_dispatch.h(7), as follows:
62 OSSL_FUNC_keyexch_newctx OSSL_FUNC_KEYEXCH_NEWCTX
64 OSSL_FUNC_keyexch_freectx OSSL_FUNC_KEYEXCH_FREECTX
65 OSSL_FUNC_keyexch_dupctx OSSL_FUNC_KEYEXCH_DUPCTX
66 OSSL_FUNC_keyexch_init OSSL_FUNC_KEYEXCH_INIT
68 OSSL_FUNC_keyexch_set_peer OSSL_FUNC_KEYEXCH_SET_PEER
69 OSSL_FUNC_keyexch_derive OSSL_FUNC_KEYEXCH_DERIVE
70 OSSL_FUNC_keyexch_set_ctx_params OSSL_FUNC_KEYEXCH_SET_CTX_PARAMS
72 OSSL_FUNC_keyexch_settable_ctx_params OSSL_FUNC_KEYEXCH_SETTABLE_CTX_PARAMS
73 OSSL_FUNC_keyexch_get_ctx_params OSSL_FUNC_KEYEXCH_GET_CTX_PARAMS
74 OSSL_FUNC_keyexch_gettable_ctx_params OSSL_FUNC_KEYEXCH_GETTABLE_CTX_PARAMS
75 A key exchange algorithm implementation may not implement all of these
77 functions. In order to be a consistent set of functions a provider
78 must implement OSSL_FUNC_keyexch_newctx, OSSL_FUNC_keyexch_freectx,
79 OSSL_FUNC_keyexch_init and OSSL_FUNC_keyexch_derive. All other
80 functions are optional.
81 A key exchange algorithm must also implement some mechanism for
83 generating, loading or importing keys via the key management
84 (OSSL_OP_KEYMGMT) operation. See provider-keymgmt(7) for further
85 details.
86 Context Management Functions
88 OSSL_FUNC_keyexch_newctx() should create and return a pointer to a
89 provider side structure for holding context information during a key
90 exchange operation. A pointer to this context will be passed back in a
91 number of the other key exchange operation function calls. The
92 parameter provctx is the provider context generated during provider
93 initialisation (see provider(7)).
94 OSSL_FUNC_keyexch_freectx() is passed a pointer to the provider side
96 key exchange context in the ctx parameter. This function should free
97 any resources associated with that context.
98 OSSL_FUNC_keyexch_dupctx() should duplicate the provider side key
100 exchange context in the ctx parameter and return the duplicate copy.
101 Shared Secret Derivation Functions
103 OSSL_FUNC_keyexch_init() initialises a key exchange operation given a
104 provider side key exchange context in the ctx parameter, and a pointer
105 to a provider key object in the provkey parameter. The params, if not
106 NULL, should be set on the context in a manner similar to using
107 OSSL_FUNC_keyexch_set_params(). The key object should have been
108 previously generated, loaded or imported into the provider using the
109 key management (OSSL_OP_KEYMGMT) operation (see provider-keymgmt(7)>.
110 OSSL_FUNC_keyexch_set_peer() is called to supply the peer's public key
112 (in the provkey parameter) to be used when deriving the shared secret.
113 It is also passed a previously initialised key exchange context in the
114 ctx parameter. The key object should have been previously generated,
115 loaded or imported into the provider using the key management
116 (OSSL_OP_KEYMGMT) operation (see provider-keymgmt(7)>.
117 OSSL_FUNC_keyexch_derive() performs the actual key exchange itself by
119 deriving a shared secret. A previously initialised key exchange
120 context is passed in the ctx parameter. The derived secret should be
121 written to the location secret which should not exceed outlen bytes.
122 The length of the shared secret should be written to *secretlen. If
123 secret is NULL then the maximum length of the shared secret should be
124 written to *secretlen.
125 Key Exchange Parameters Functions
127 OSSL_FUNC_keyexch_set_ctx_params() sets key exchange parameters
128 associated with the given provider side key exchange context ctx to
129 params, see "Common Key Exchange parameters". Any parameter settings
130 are additional to any that were previously set. Passing NULL for
131 params should return true.
132 OSSL_FUNC_keyexch_get_ctx_params() gets key exchange parameters
134 associated with the given provider side key exchange context ctx into
135 params, see "Common Key Exchange parameters". Passing NULL for params
136 should return true.
137 OSSL_FUNC_keyexch_settable_ctx_params() yields a constant OSSL_PARAM
139 array that describes the settable parameters, i.e. parameters that can
140 be used with OP_signature_set_ctx_params(). If
141 OSSL_FUNC_keyexch_settable_ctx_params() is present,
142 OSSL_FUNC_keyexch_set_ctx_params() must also be present, and vice
143 versa. Similarly, OSSL_FUNC_keyexch_gettable_ctx_params() yields a
144 constant OSSL_PARAM array that describes the gettable parameters, i.e.
145 parameters that can be handled by OP_signature_get_ctx_params(). If
146 OSSL_FUNC_keyexch_gettable_ctx_params() is present,
147 OSSL_FUNC_keyexch_get_ctx_params() must also be present, and vice
148 versa. See OSSL_PARAM(3) for the use of OSSL_PARAM as parameter
149 descriptor.
150 Notice that not all settable parameters are also gettable, and vice
152 versa.
153 Common Key Exchange parameters
155 See OSSL_PARAM(3) for further details on the parameters structure used
156 by the OSSL_FUNC_keyexch_set_ctx_params() and
157 OSSL_FUNC_keyexch_get_ctx_params() functions.
158 Common parameters currently recognised by built-in key exchange
160 algorithms are as follows.
161 "kdf-type" (OSSL_EXCHANGE_PARAM_KDF_TYPE) <UTF8 string>
163 Sets or gets the Key Derivation Function type to apply within the
164 associated key exchange ctx.
165 "kdf-digest" (OSSL_EXCHANGE_PARAM_KDF_DIGEST) <UTF8 string>
167 Sets or gets the Digest algorithm to be used as part of the Key
168 Derivation Function associated with the given key exchange ctx.
169 "kdf-digest-props" (OSSL_EXCHANGE_PARAM_KDF_DIGEST_PROPS) <UTF8 string>
171 Sets properties to be used upon look up of the implementation for
172 the selected Digest algorithm for the Key Derivation Function
173 associated with the given key exchange ctx.
174 "kdf-outlen" (OSSL_EXCHANGE_PARAM_KDF_OUTLEN) <unsigned integer>
176 Sets or gets the desired size for the output of the chosen Key
177 Derivation Function associated with the given key exchange ctx.
178 The length of the "kdf-outlen" parameter should not exceed that of
179 a size_t.
180 "kdf-ukm" (OSSL_EXCHANGE_PARAM_KDF_UKM) <octet string>
182 Sets the User Key Material to be used as part of the selected Key
183 Derivation Function associated with the given key exchange ctx.
184 "kdf-ukm" (OSSL_EXCHANGE_PARAM_KDF_UKM) <octet string ptr>
186 Gets a pointer to the User Key Material to be used as part of the
187 selected Key Derivation Function associated with the given key
188 exchange ctx. Providers usually do not need to support this
189 gettable parameter as its sole purpose is to support functionality
190 of the deprecated EVP_PKEY_CTX_get0_ecdh_kdf_ukm() and
191 EVP_PKEY_CTX_get0_dh_kdf_ukm() functions.
192
194 OSSL_FUNC_keyexch_newctx() and OSSL_FUNC_keyexch_dupctx() should return
195 the newly created provider side key exchange context, or NULL on
196 failure.
197 OSSL_FUNC_keyexch_init(), OSSL_FUNC_keyexch_set_peer(),
199 OSSL_FUNC_keyexch_derive(), OSSL_FUNC_keyexch_set_params(), and
200 OSSL_FUNC_keyexch_get_params() should return 1 for success or 0 on
201 error.
202 OSSL_FUNC_keyexch_settable_ctx_params() and
204 OSSL_FUNC_keyexch_gettable_ctx_params() should always return a constant
205 OSSL_PARAM array.
206
208 provider(7)
209
211 The provider KEYEXCH interface was introduced in OpenSSL 3.0.
212
214 Copyright 2019-2022 The OpenSSL Project Authors. All Rights Reserved.
215 Licensed under the Apache License 2.0 (the "License"). You may not use
217 this file except in compliance with the License. You can obtain a copy
218 in the file LICENSE in the source distribution or at
219 <https://www.openssl.org/source/license.html>.
2203.0.5 2022-07-05 PROVIDER-KEYEXCH(7ossl)