1 =pod 2 3 =head1 NAME 4 5 provider-keyexch - The keyexch library E<lt>-E<gt> provider functions 6 7 =head1 SYNOPSIS 8 9 =for openssl multiple includes 10 11 #include <openssl/core_dispatch.h> 12 #include <openssl/core_names.h> 13 14 /* 15 * None of these are actual functions, but are displayed like this for 16 * the function signatures for functions that are offered as function 17 * pointers in OSSL_DISPATCH arrays. 18 */ 19 20 /* Context management */ 21 void *OSSL_FUNC_keyexch_newctx(void *provctx); 22 void OSSL_FUNC_keyexch_freectx(void *ctx); 23 void *OSSL_FUNC_keyexch_dupctx(void *ctx); 24 25 /* Shared secret derivation */ 26 int OSSL_FUNC_keyexch_init(void *ctx, void *provkey, 27 const OSSL_PARAM params[]); 28 int OSSL_FUNC_keyexch_set_peer(void *ctx, void *provkey); 29 int OSSL_FUNC_keyexch_derive(void *ctx, unsigned char *secret, size_t *secretlen, 30 size_t outlen); 31 32 /* Key Exchange parameters */ 33 int OSSL_FUNC_keyexch_set_ctx_params(void *ctx, const OSSL_PARAM params[]); 34 const OSSL_PARAM *OSSL_FUNC_keyexch_settable_ctx_params(void *ctx, 35 void *provctx); 36 int OSSL_FUNC_keyexch_get_ctx_params(void *ctx, OSSL_PARAM params[]); 37 const OSSL_PARAM *OSSL_FUNC_keyexch_gettable_ctx_params(void *ctx, 38 void *provctx); 39 40 =head1 DESCRIPTION 41 42 This documentation is primarily aimed at provider authors. See L<provider(7)> 43 for further information. 44 45 The key exchange (OSSL_OP_KEYEXCH) operation enables providers to implement key 46 exchange algorithms and make them available to applications via 47 L<EVP_PKEY_derive(3)> and 48 other related functions). 49 50 All "functions" mentioned here are passed as function pointers between 51 F<libcrypto> and the provider in L<OSSL_DISPATCH(3)> arrays via 52 L<OSSL_ALGORITHM(3)> arrays that are returned by the provider's 53 provider_query_operation() function 54 (see L<provider-base(7)/Provider Functions>). 55 56 All these "functions" have a corresponding function type definition 57 named B<OSSL_FUNC_{name}_fn>, and a helper function to retrieve the 58 function pointer from an L<OSSL_DISPATCH(3)> element named 59 B<OSSL_FUNC_{name}>. 60 For example, the "function" OSSL_FUNC_keyexch_newctx() has these: 61 62 typedef void *(OSSL_FUNC_keyexch_newctx_fn)(void *provctx); 63 static ossl_inline OSSL_FUNC_keyexch_newctx_fn 64 OSSL_FUNC_keyexch_newctx(const OSSL_DISPATCH *opf); 65 66 L<OSSL_DISPATCH(3)> arrays are indexed by numbers that are provided as 67 macros in L<openssl-core_dispatch.h(7)>, as follows: 68 69 OSSL_FUNC_keyexch_newctx OSSL_FUNC_KEYEXCH_NEWCTX 70 OSSL_FUNC_keyexch_freectx OSSL_FUNC_KEYEXCH_FREECTX 71 OSSL_FUNC_keyexch_dupctx OSSL_FUNC_KEYEXCH_DUPCTX 72 73 OSSL_FUNC_keyexch_init OSSL_FUNC_KEYEXCH_INIT 74 OSSL_FUNC_keyexch_set_peer OSSL_FUNC_KEYEXCH_SET_PEER 75 OSSL_FUNC_keyexch_derive OSSL_FUNC_KEYEXCH_DERIVE 76 77 OSSL_FUNC_keyexch_set_ctx_params OSSL_FUNC_KEYEXCH_SET_CTX_PARAMS 78 OSSL_FUNC_keyexch_settable_ctx_params OSSL_FUNC_KEYEXCH_SETTABLE_CTX_PARAMS 79 OSSL_FUNC_keyexch_get_ctx_params OSSL_FUNC_KEYEXCH_GET_CTX_PARAMS 80 OSSL_FUNC_keyexch_gettable_ctx_params OSSL_FUNC_KEYEXCH_GETTABLE_CTX_PARAMS 81 82 A key exchange algorithm implementation may not implement all of these functions. 83 In order to be a consistent set of functions a provider must implement 84 OSSL_FUNC_keyexch_newctx, OSSL_FUNC_keyexch_freectx, OSSL_FUNC_keyexch_init and OSSL_FUNC_keyexch_derive. 85 All other functions are optional. 86 87 A key exchange algorithm must also implement some mechanism for generating, 88 loading or importing keys via the key management (OSSL_OP_KEYMGMT) operation. 89 See L<provider-keymgmt(7)> for further details. 90 91 =head2 Context Management Functions 92 93 OSSL_FUNC_keyexch_newctx() should create and return a pointer to a provider side 94 structure for holding context information during a key exchange operation. 95 A pointer to this context will be passed back in a number of the other key 96 exchange operation function calls. 97 The parameter I<provctx> is the provider context generated during provider 98 initialisation (see L<provider(7)>). 99 100 OSSL_FUNC_keyexch_freectx() is passed a pointer to the provider side key exchange 101 context in the I<ctx> parameter. 102 This function should free any resources associated with that context. 103 104 OSSL_FUNC_keyexch_dupctx() should duplicate the provider side key exchange context in 105 the I<ctx> parameter and return the duplicate copy. 106 107 =head2 Shared Secret Derivation Functions 108 109 OSSL_FUNC_keyexch_init() initialises a key exchange operation given a provider side key 110 exchange context in the I<ctx> parameter, and a pointer to a provider key object 111 in the I<provkey> parameter. 112 The I<params>, if not NULL, should be set on the context in a manner similar to 113 using OSSL_FUNC_keyexch_set_params(). 114 The key object should have been previously 115 generated, loaded or imported into the provider using the key management 116 (OSSL_OP_KEYMGMT) operation (see provider-keymgmt(7)>. 117 118 OSSL_FUNC_keyexch_set_peer() is called to supply the peer's public key (in the 119 I<provkey> parameter) to be used when deriving the shared secret. 120 It is also passed a previously initialised key exchange context in the I<ctx> 121 parameter. 122 The key object should have been previously generated, loaded or imported into 123 the provider using the key management (OSSL_OP_KEYMGMT) operation (see 124 provider-keymgmt(7)>. 125 126 OSSL_FUNC_keyexch_derive() performs the actual key exchange itself by deriving a shared 127 secret. 128 A previously initialised key exchange context is passed in the I<ctx> 129 parameter. 130 The derived secret should be written to the location I<secret> which should not 131 exceed I<outlen> bytes. 132 The length of the shared secret should be written to I<*secretlen>. 133 If I<secret> is NULL then the maximum length of the shared secret should be 134 written to I<*secretlen>. 135 136 =head2 Key Exchange Parameters Functions 137 138 OSSL_FUNC_keyexch_set_ctx_params() sets key exchange parameters associated with the 139 given provider side key exchange context I<ctx> to I<params>, 140 see L</Common Key Exchange parameters>. 141 Any parameter settings are additional to any that were previously set. 142 Passing NULL for I<params> should return true. 143 144 OSSL_FUNC_keyexch_get_ctx_params() gets key exchange parameters associated with the 145 given provider side key exchange context I<ctx> into I<params>, 146 see L</Common Key Exchange parameters>. 147 Passing NULL for I<params> should return true. 148 149 OSSL_FUNC_keyexch_settable_ctx_params() yields a constant L<OSSL_PARAM(3)> array that 150 describes the settable parameters, i.e. parameters that can be used with 151 OP_signature_set_ctx_params(). 152 If OSSL_FUNC_keyexch_settable_ctx_params() is present, OSSL_FUNC_keyexch_set_ctx_params() must 153 also be present, and vice versa. 154 Similarly, OSSL_FUNC_keyexch_gettable_ctx_params() yields a constant L<OSSL_PARAM(3)> 155 array that describes the gettable parameters, i.e. parameters that can be 156 handled by OP_signature_get_ctx_params(). 157 If OSSL_FUNC_keyexch_gettable_ctx_params() is present, OSSL_FUNC_keyexch_get_ctx_params() must 158 also be present, and vice versa. 159 160 Notice that not all settable parameters are also gettable, and vice versa. 161 162 =head2 Common Key Exchange parameters 163 164 See L<OSSL_PARAM(3)> for further details on the parameters structure used by 165 the OSSL_FUNC_keyexch_set_ctx_params() and OSSL_FUNC_keyexch_get_ctx_params() functions. 166 167 Common parameters currently recognised by built-in key exchange algorithms are 168 as follows. 169 170 =over 4 171 172 =item "kdf-type" (B<OSSL_EXCHANGE_PARAM_KDF_TYPE>) <UTF8 string> 173 174 Sets or gets the Key Derivation Function type to apply within the associated key 175 exchange ctx. 176 177 =item "kdf-digest" (B<OSSL_EXCHANGE_PARAM_KDF_DIGEST>) <UTF8 string> 178 179 Sets or gets the Digest algorithm to be used as part of the Key Derivation Function 180 associated with the given key exchange ctx. 181 182 =item "kdf-digest-props" (B<OSSL_EXCHANGE_PARAM_KDF_DIGEST_PROPS>) <UTF8 string> 183 184 Sets properties to be used upon look up of the implementation for the selected 185 Digest algorithm for the Key Derivation Function associated with the given key 186 exchange ctx. 187 188 =item "kdf-outlen" (B<OSSL_EXCHANGE_PARAM_KDF_OUTLEN>) <unsigned integer> 189 190 Sets or gets the desired size for the output of the chosen Key Derivation Function 191 associated with the given key exchange ctx. 192 The length of the "kdf-outlen" parameter should not exceed that of a B<size_t>. 193 194 =item "kdf-ukm" (B<OSSL_EXCHANGE_PARAM_KDF_UKM>) <octet string> 195 196 Sets the User Key Material to be used as part of the selected Key Derivation 197 Function associated with the given key exchange ctx. 198 199 =item "kdf-ukm" (B<OSSL_EXCHANGE_PARAM_KDF_UKM>) <octet string ptr> 200 201 Gets a pointer to the User Key Material to be used as part of the selected 202 Key Derivation Function associated with the given key exchange ctx. Providers 203 usually do not need to support this gettable parameter as its sole purpose 204 is to support functionality of the deprecated EVP_PKEY_CTX_get0_ecdh_kdf_ukm() 205 and EVP_PKEY_CTX_get0_dh_kdf_ukm() functions. 206 207 =back 208 209 =head1 RETURN VALUES 210 211 OSSL_FUNC_keyexch_newctx() and OSSL_FUNC_keyexch_dupctx() should return the newly created 212 provider side key exchange context, or NULL on failure. 213 214 OSSL_FUNC_keyexch_init(), OSSL_FUNC_keyexch_set_peer(), OSSL_FUNC_keyexch_derive(), 215 OSSL_FUNC_keyexch_set_params(), and OSSL_FUNC_keyexch_get_params() should return 1 for success 216 or 0 on error. 217 218 OSSL_FUNC_keyexch_settable_ctx_params() and OSSL_FUNC_keyexch_gettable_ctx_params() should 219 always return a constant L<OSSL_PARAM(3)> array. 220 221 =head1 SEE ALSO 222 223 L<provider(7)> 224 225 =head1 HISTORY 226 227 The provider KEYEXCH interface was introduced in OpenSSL 3.0. 228 229 =head1 COPYRIGHT 230 231 Copyright 2019-2022 The OpenSSL Project Authors. All Rights Reserved. 232 233 Licensed under the Apache License 2.0 (the "License"). You may not use 234 this file except in compliance with the License. You can obtain a copy 235 in the file LICENSE in the source distribution or at 236 L<https://www.openssl.org/source/license.html>. 237 238 =cut 239
Indexes created Wed Mar 04 15:26:31 UTC 2026