1=pod 2 3=head1 NAME 4 5EVP_KDF, EVP_KDF_fetch, EVP_KDF_free, EVP_KDF_up_ref, 6EVP_KDF_CTX, EVP_KDF_CTX_new, EVP_KDF_CTX_free, EVP_KDF_CTX_dup, 7EVP_KDF_CTX_reset, EVP_KDF_derive, 8EVP_KDF_CTX_get_kdf_size, 9EVP_KDF_get0_provider, EVP_KDF_CTX_kdf, EVP_KDF_is_a, 10EVP_KDF_get0_name, EVP_KDF_names_do_all, EVP_KDF_get0_description, 11EVP_KDF_CTX_get_params, EVP_KDF_CTX_set_params, EVP_KDF_do_all_provided, 12EVP_KDF_get_params, EVP_KDF_gettable_params, 13EVP_KDF_gettable_ctx_params, EVP_KDF_settable_ctx_params, 14EVP_KDF_CTX_gettable_params, EVP_KDF_CTX_settable_params - EVP KDF routines 15 16=head1 SYNOPSIS 17 18 #include <openssl/kdf.h> 19 20 typedef struct evp_kdf_st EVP_KDF; 21 typedef struct evp_kdf_ctx_st EVP_KDF_CTX; 22 23 EVP_KDF_CTX *EVP_KDF_CTX_new(const EVP_KDF *kdf); 24 const EVP_KDF *EVP_KDF_CTX_kdf(EVP_KDF_CTX *ctx); 25 void EVP_KDF_CTX_free(EVP_KDF_CTX *ctx); 26 EVP_KDF_CTX *EVP_KDF_CTX_dup(const EVP_KDF_CTX *src); 27 void EVP_KDF_CTX_reset(EVP_KDF_CTX *ctx); 28 size_t EVP_KDF_CTX_get_kdf_size(EVP_KDF_CTX *ctx); 29 int EVP_KDF_derive(EVP_KDF_CTX *ctx, unsigned char *key, size_t keylen, 30 const OSSL_PARAM params[]); 31 int EVP_KDF_up_ref(EVP_KDF *kdf); 32 void EVP_KDF_free(EVP_KDF *kdf); 33 EVP_KDF *EVP_KDF_fetch(OSSL_LIB_CTX *libctx, const char *algorithm, 34 const char *properties); 35 int EVP_KDF_is_a(const EVP_KDF *kdf, const char *name); 36 const char *EVP_KDF_get0_name(const EVP_KDF *kdf); 37 const char *EVP_KDF_get0_description(const EVP_KDF *kdf); 38 const OSSL_PROVIDER *EVP_KDF_get0_provider(const EVP_KDF *kdf); 39 void EVP_KDF_do_all_provided(OSSL_LIB_CTX *libctx, 40 void (*fn)(EVP_KDF *kdf, void *arg), 41 void *arg); 42 int EVP_KDF_names_do_all(const EVP_KDF *kdf, 43 void (*fn)(const char *name, void *data), 44 void *data); 45 int EVP_KDF_get_params(EVP_KDF *kdf, OSSL_PARAM params[]); 46 int EVP_KDF_CTX_get_params(EVP_KDF_CTX *ctx, OSSL_PARAM params[]); 47 int EVP_KDF_CTX_set_params(EVP_KDF_CTX *ctx, const OSSL_PARAM params[]); 48 const OSSL_PARAM *EVP_KDF_gettable_params(const EVP_KDF *kdf); 49 const OSSL_PARAM *EVP_KDF_gettable_ctx_params(const EVP_KDF *kdf); 50 const OSSL_PARAM *EVP_KDF_settable_ctx_params(const EVP_KDF *kdf); 51 const OSSL_PARAM *EVP_KDF_CTX_gettable_params(const EVP_KDF *kdf); 52 const OSSL_PARAM *EVP_KDF_CTX_settable_params(const EVP_KDF *kdf); 53 const OSSL_PROVIDER *EVP_KDF_get0_provider(const EVP_KDF *kdf); 54 55=head1 DESCRIPTION 56 57The EVP KDF routines are a high-level interface to Key Derivation Function 58algorithms and should be used instead of algorithm-specific functions. 59 60After creating a B<EVP_KDF_CTX> for the required algorithm using 61EVP_KDF_CTX_new(), inputs to the algorithm are supplied either by 62passing them as part of the EVP_KDF_derive() call or using calls 63to EVP_KDF_CTX_set_params() before calling EVP_KDF_derive() to derive 64the key. 65 66=head2 Types 67 68B<EVP_KDF> is a type that holds the implementation of a KDF. 69 70B<EVP_KDF_CTX> is a context type that holds the algorithm inputs. 71 72=head2 Algorithm implementation fetching 73 74EVP_KDF_fetch() fetches an implementation of a KDF I<algorithm>, given 75a library context I<libctx> and a set of I<properties>. 76See L<crypto(7)/ALGORITHM FETCHING> for further information. 77 78See L<OSSL_PROVIDER-default(7)/Key Derivation Function (KDF)> for the lists of 79algorithms supported by the default provider. 80 81The returned value must eventually be freed with 82L<EVP_KDF_free(3)>. 83 84EVP_KDF_up_ref() increments the reference count of an already fetched 85KDF. 86 87EVP_KDF_free() frees a fetched algorithm. 88NULL is a valid parameter, for which this function is a no-op. 89 90=head2 Context manipulation functions 91 92EVP_KDF_CTX_new() creates a new context for the KDF implementation I<kdf>. 93 94EVP_KDF_CTX_free() frees up the context I<ctx>. If I<ctx> is NULL, nothing 95is done. 96 97EVP_KDF_CTX_kdf() returns the B<EVP_KDF> associated with the context 98I<ctx>. 99 100=head2 Computing functions 101 102EVP_KDF_CTX_reset() resets the context to the default state as if the context 103had just been created. 104 105EVP_KDF_derive() processes any parameters in I<Params> and then derives 106I<keylen> bytes of key material and places it in the I<key> buffer. 107If the algorithm produces a fixed amount of output then an error will 108occur unless the I<keylen> parameter is equal to that output size, 109as returned by EVP_KDF_CTX_get_kdf_size(). 110 111EVP_KDF_get_params() retrieves details about the implementation 112I<kdf>. 113The set of parameters given with I<params> determine exactly what 114parameters should be retrieved. 115Note that a parameter that is unknown in the underlying context is 116simply ignored. 117 118EVP_KDF_CTX_get_params() retrieves chosen parameters, given the 119context I<ctx> and its underlying context. 120The set of parameters given with I<params> determine exactly what 121parameters should be retrieved. 122Note that a parameter that is unknown in the underlying context is 123simply ignored. 124 125EVP_KDF_CTX_set_params() passes chosen parameters to the underlying 126context, given a context I<ctx>. 127The set of parameters given with I<params> determine exactly what 128parameters are passed down. 129Note that a parameter that is unknown in the underlying context is 130simply ignored. 131Also, what happens when a needed parameter isn't passed down is 132defined by the implementation. 133 134EVP_KDF_gettable_params() returns an B<OSSL_PARAM> array that describes 135the retrievable and settable parameters. EVP_KDF_gettable_params() 136returns parameters that can be used with EVP_KDF_get_params(). 137See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as a parameter descriptor. 138 139EVP_KDF_gettable_ctx_params() and EVP_KDF_CTX_gettable_params() 140return constant B<OSSL_PARAM> arrays that describe the retrievable 141parameters that can be used with EVP_KDF_CTX_get_params(). 142EVP_KDF_gettable_ctx_params() returns the parameters that can be retrieved 143from the algorithm, whereas EVP_KDF_CTX_gettable_params() returns 144the parameters that can be retrieved in the context's current state. 145See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as a parameter descriptor. 146 147EVP_KDF_settable_ctx_params() and EVP_KDF_CTX_settable_params() return 148constant B<OSSL_PARAM> arrays that describe the settable parameters that 149can be used with EVP_KDF_CTX_set_params(). EVP_KDF_settable_ctx_params() 150returns the parameters that can be retrieved from the algorithm, 151whereas EVP_KDF_CTX_settable_params() returns the parameters that can 152be retrieved in the context's current state. See L<OSSL_PARAM(3)> 153for the use of B<OSSL_PARAM> as a parameter descriptor. 154 155=head2 Information functions 156 157EVP_KDF_CTX_get_kdf_size() returns the output size if the algorithm produces a fixed amount 158of output and B<SIZE_MAX> otherwise. If an error occurs then 0 is returned. 159For some algorithms an error may result if input parameters necessary to 160calculate a fixed output size have not yet been supplied. 161 162EVP_KDF_is_a() returns 1 if I<kdf> is an implementation of an 163algorithm that's identifiable with I<name>, otherwise 0. 164 165EVP_KDF_get0_provider() returns the provider that holds the implementation 166of the given I<kdf>. 167 168EVP_KDF_do_all_provided() traverses all KDF implemented by all activated 169providers in the given library context I<libctx>, and for each of the 170implementations, calls the given function I<fn> with the implementation method 171and the given I<arg> as argument. 172 173EVP_KDF_get0_name() return the name of the given KDF. For fetched KDFs 174with multiple names, only one of them is returned; it's 175recommended to use EVP_KDF_names_do_all() instead. 176 177EVP_KDF_names_do_all() traverses all names for I<kdf>, and calls 178I<fn> with each name and I<data>. 179 180EVP_KDF_get0_description() returns a description of the I<kdf>, meant for 181display and human consumption. The description is at the discretion of 182the I<kdf> implementation. 183 184=head1 PARAMETERS 185 186The standard parameter names are: 187 188=over 4 189 190=item "pass" (B<OSSL_KDF_PARAM_PASSWORD>) <octet string> 191 192Some KDF implementations require a password. 193For those KDF implementations that support it, this parameter sets the password. 194 195=item "salt" (B<OSSL_KDF_PARAM_SALT>) <octet string> 196 197Some KDF implementations can take a salt. 198For those KDF implementations that support it, this parameter sets the salt. 199 200The default value, if any, is implementation dependent. 201 202=item "iter" (B<OSSL_KDF_PARAM_ITER>) <unsigned integer> 203 204Some KDF implementations require an iteration count. 205For those KDF implementations that support it, this parameter sets the 206iteration count. 207 208The default value, if any, is implementation dependent. 209 210=item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string> 211 212=item "mac" (B<OSSL_KDF_PARAM_MAC>) <UTF8 string> 213 214=item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string> 215 216=item "cipher" (B<OSSL_KDF_PARAM_CIPHER>) <UTF8 string> 217 218For KDF implementations that use an underlying computation MAC, digest or 219cipher, these parameters set what the algorithm should be. 220 221The value is always the name of the intended algorithm, 222or the properties. 223 224Note that not all algorithms may support all possible underlying 225implementations. 226 227=item "key" (B<OSSL_KDF_PARAM_KEY>) <octet string> 228 229Some KDF implementations require a key. 230For those KDF implementations that support it, this octet string parameter 231sets the key. 232 233=item "maclen" (B<OSSL_KDF_PARAM_MAC_SIZE>) <unsigned integer> 234 235Used by implementations that use a MAC with a variable output size (KMAC). 236For those KDF implementations that support it, this parameter 237sets the MAC output size. 238 239The default value, if any, is implementation dependent. 240The length must never exceed what can be given with a B<size_t>. 241 242=item "maxmem_bytes" (B<OSSL_KDF_PARAM_SCRYPT_MAXMEM>) <unsigned integer> 243 244Memory-hard password-based KDF algorithms, such as scrypt, use an amount of 245memory that depends on the load factors provided as input. 246For those KDF implementations that support it, this B<uint64_t> parameter sets 247an upper limit on the amount of memory that may be consumed while performing 248a key derivation. 249If this memory usage limit is exceeded because the load factors are chosen 250too high, the key derivation will fail. 251 252The default value is implementation dependent. 253The memory size must never exceed what can be given with a B<size_t>. 254 255=back 256 257=head1 RETURN VALUES 258 259EVP_KDF_fetch() returns a pointer to a newly fetched B<EVP_KDF>, or 260NULL if allocation failed. 261 262EVP_KDF_get0_provider() returns a pointer to the provider for the KDF, or 263NULL on error. 264 265EVP_KDF_up_ref() returns 1 on success, 0 on error. 266 267EVP_KDF_CTX_new() returns either the newly allocated 268B<EVP_KDF_CTX> structure or NULL if an error occurred. 269 270EVP_KDF_CTX_free() and EVP_KDF_CTX_reset() do not return a value. 271 272EVP_KDF_CTX_get_kdf_size() returns the output size. B<SIZE_MAX> is returned to indicate 273that the algorithm produces a variable amount of output; 0 to indicate failure. 274 275EVP_KDF_get0_name() returns the name of the KDF, or NULL on error. 276 277EVP_KDF_names_do_all() returns 1 if the callback was called for all names. A 278return value of 0 means that the callback was not called for any names. 279 280The remaining functions return 1 for success and 0 or a negative value for 281failure. In particular, a return value of -2 indicates the operation is not 282supported by the KDF algorithm. 283 284=head1 NOTES 285 286The KDF life-cycle is described in L<life_cycle-kdf(7)>. In the future, 287the transitions described there will be enforced. When this is done, it will 288not be considered a breaking change to the API. 289 290=head1 SEE ALSO 291 292L<OSSL_PROVIDER-default(7)/Key Derivation Function (KDF)>, 293L<life_cycle-kdf(7)>. 294 295=head1 HISTORY 296 297This functionality was added to OpenSSL 3.0. 298 299=head1 COPYRIGHT 300 301Copyright 2019-2021 The OpenSSL Project Authors. All Rights Reserved. 302 303Licensed under the Apache License 2.0 (the "License"). You may not use 304this file except in compliance with the License. You can obtain a copy 305in the file LICENSE in the source distribution or at 306L<https://www.openssl.org/source/license.html>. 307 308=cut 309
