5 EVP_KDF, EVP_KDF_fetch, EVP_KDF_free, EVP_KDF_up_ref,
6 EVP_KDF_CTX, EVP_KDF_CTX_new, EVP_KDF_CTX_free, EVP_KDF_CTX_dup,
7 EVP_KDF_CTX_reset, EVP_KDF_derive,
8 EVP_KDF_CTX_get_kdf_size, EVP_KDF_provider, EVP_KDF_CTX_kdf, EVP_KDF_is_a,
9 EVP_KDF_number, EVP_KDF_name, EVP_KDF_names_do_all,
10 EVP_KDF_CTX_get_params, EVP_KDF_CTX_set_params, EVP_KDF_do_all_provided,
11 EVP_KDF_get_params, EVP_KDF_gettable_ctx_params, EVP_KDF_settable_ctx_params,
12 EVP_KDF_gettable_params - EVP KDF routines
16 #include <openssl/kdf.h>
18 typedef struct evp_kdf_st EVP_KDF;
19 typedef struct evp_kdf_ctx_st EVP_KDF_CTX;
21 EVP_KDF_CTX *EVP_KDF_CTX_new(const EVP_KDF *kdf);
22 const EVP_KDF *EVP_KDF_CTX_kdf(EVP_KDF_CTX *ctx);
23 void EVP_KDF_CTX_free(EVP_KDF_CTX *ctx);
24 EVP_KDF_CTX *EVP_KDF_CTX_dup(const EVP_KDF_CTX *src);
25 void EVP_KDF_CTX_reset(EVP_KDF_CTX *ctx);
26 size_t EVP_KDF_CTX_get_kdf_size(EVP_KDF_CTX *ctx);
27 int EVP_KDF_derive(EVP_KDF_CTX *ctx, unsigned char *key, size_t keylen);
28 int EVP_KDF_up_ref(EVP_KDF *kdf);
29 void EVP_KDF_free(EVP_KDF *kdf);
30 EVP_KDF *EVP_KDF_fetch(OSSL_LIB_CTX *libctx, const char *algorithm,
31 const char *properties);
32 int EVP_KDF_number(const EVP_KDF *kdf);
33 int EVP_KDF_is_a(const EVP_KDF *kdf, const char *name);
34 const char *EVP_KDF_name(const EVP_KDF *kdf);
35 const OSSL_PROVIDER *EVP_KDF_provider(const EVP_KDF *kdf);
36 void EVP_KDF_do_all_provided(OSSL_LIB_CTX *libctx,
37 void (*fn)(EVP_KDF *kdf, void *arg),
39 int EVP_KDF_names_do_all(const EVP_KDF *kdf,
40 void (*fn)(const char *name, void *data),
42 int EVP_KDF_get_params(EVP_KDF *kdf, OSSL_PARAM params[]);
43 int EVP_KDF_CTX_get_params(EVP_KDF_CTX *ctx, OSSL_PARAM params[]);
44 int EVP_KDF_CTX_set_params(EVP_KDF_CTX *ctx, const OSSL_PARAM params[]);
45 const OSSL_PARAM *EVP_KDF_gettable_params(const EVP_KDF *kdf);
46 const OSSL_PARAM *EVP_KDF_gettable_ctx_params(const EVP_KDF *kdf);
47 const OSSL_PARAM *EVP_KDF_settable_ctx_params(const EVP_KDF *kdf);
48 const OSSL_PROVIDER *EVP_KDF_provider(const EVP_KDF *kdf);
52 The EVP KDF routines are a high-level interface to Key Derivation Function
53 algorithms and should be used instead of algorithm-specific functions.
55 After creating a B<EVP_KDF_CTX> for the required algorithm using
56 EVP_KDF_CTX_new(), inputs to the algorithm are supplied
57 using calls to EVP_KDF_CTX_set_params() before
58 calling EVP_KDF_derive() to derive the key.
62 B<EVP_KDF> is a type that holds the implementation of a KDF.
64 B<EVP_KDF_CTX> is a context type that holds the algorithm inputs.
66 =head2 Algorithm implementation fetching
68 EVP_KDF_fetch() fetches an implementation of a KDF I<algorithm>, given
69 a library context I<libctx> and a set of I<properties>.
70 See L<provider(7)/Fetching algorithms> for further information.
72 See L<OSSL_PROVIDER-default(7)/Key Derivation Function (KDF)> for the lists of
73 algorithms supported by the default provider.
75 The returned value must eventually be freed with
78 EVP_KDF_up_ref() increments the reference count of an already fetched
81 EVP_KDF_free() frees a fetched algorithm.
82 NULL is a valid parameter, for which this function is a no-op.
84 =head2 Context manipulation functions
86 EVP_KDF_CTX_new() creates a new context for the KDF implementation I<kdf>.
88 EVP_KDF_CTX_free() frees up the context I<ctx>. If I<ctx> is NULL, nothing
91 EVP_KDF_CTX_kdf() returns the B<EVP_KDF> associated with the context
94 =head2 Computing functions
96 EVP_KDF_CTX_reset() resets the context to the default state as if the context
97 had just been created.
99 EVP_KDF_derive() derives I<keylen> bytes of key material and places it in the
100 I<key> buffer. If the algorithm produces a fixed amount of output then an
101 error will occur unless the I<keylen> parameter is equal to that output size,
102 as returned by EVP_KDF_CTX_get_kdf_size().
104 EVP_KDF_get_params() retrieves details about the implementation
106 The set of parameters given with I<params> determine exactly what
107 parameters should be retrieved.
108 Note that a parameter that is unknown in the underlying context is
111 EVP_KDF_CTX_get_params() retrieves chosen parameters, given the
112 context I<ctx> and its underlying context.
113 The set of parameters given with I<params> determine exactly what
114 parameters should be retrieved.
115 Note that a parameter that is unknown in the underlying context is
118 EVP_KDF_CTX_set_params() passes chosen parameters to the underlying
119 context, given a context I<ctx>.
120 The set of parameters given with I<params> determine exactly what
121 parameters are passed down.
122 Note that a parameter that is unknown in the underlying context is
124 Also, what happens when a needed parameter isn't passed down is
125 defined by the implementation.
127 EVP_KDF_gettable_params(), EVP_KDF_gettable_ctx_params() and
128 EVP_KDF_settable_ctx_params() get a constant B<OSSL_PARAM> array that
129 describes the retrievable and settable parameters, i.e. parameters that
130 can be used with EVP_KDF_get_params(), EVP_KDF_CTX_get_params()
131 and EVP_KDF_CTX_set_params(), respectively.
132 See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as parameter descriptor.
134 =head2 Information functions
136 EVP_KDF_CTX_get_kdf_size() returns the output size if the algorithm produces a fixed amount
137 of output and B<SIZE_MAX> otherwise. If an error occurs then 0 is returned.
138 For some algorithms an error may result if input parameters necessary to
139 calculate a fixed output size have not yet been supplied.
141 EVP_KDF_is_a() returns 1 if I<kdf> is an implementation of an
142 algorithm that's identifiable with I<name>, otherwise 0.
144 EVP_KDF_provider() returns the provider that holds the implementation
147 EVP_KDF_do_all_provided() traverses all KDF implemented by all activated
148 providers in the given library context I<libctx>, and for each of the
149 implementations, calls the given function I<fn> with the implementation method
150 and the given I<arg> as argument.
152 EVP_KDF_number() returns the internal dynamic number assigned to
155 EVP_KDF_name() return the name of the given KDF. For fetched KDFs
156 with multiple names, only one of them is returned; it's
157 recommended to use EVP_KDF_names_do_all() instead.
159 EVP_KDF_names_do_all() traverses all names for I<kdf>, and calls
160 I<fn> with each name and I<data>.
164 The standard parameter names are:
168 =item "pass" (B<OSSL_KDF_PARAM_PASSWORD>) <octet string>
170 Some KDF implementations require a password.
171 For those KDF implementations that support it, this parameter sets the password.
173 =item "salt" (B<OSSL_KDF_PARAM_SALT>) <octet string>
175 Some KDF implementations can take a salt.
176 For those KDF implementations that support it, this parameter sets the salt.
178 The default value, if any, is implementation dependent.
180 =item "iter" (B<OSSL_KDF_PARAM_ITER>) <unsigned integer>
182 Some KDF implementations require an iteration count.
183 For those KDF implementations that support it, this parameter sets the
186 The default value, if any, is implementation dependent.
188 =item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string>
190 =item "mac" (B<OSSL_KDF_PARAM_MAC>) <UTF8 string>
192 =item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string>
194 =item "cipher" (B<OSSL_KDF_PARAM_CIPHER>) <UTF8 string>
196 For KDF implementations that use an underlying computation MAC, digest or
197 cipher, these parameters set what the algorithm should be.
199 The value is always the name of the intended algorithm,
202 Note that not all algorithms may support all possible underlying
205 =item "key" (B<OSSL_KDF_PARAM_KEY>) <octet string>
207 Some KDF implementations require a key.
208 For those KDF implementations that support it, this octet string parameter
211 =item "maclen" (B<OSSL_KDF_PARAM_MAC_SIZE>) <unsigned integer>
213 Used by implementations that use a MAC with a variable output size (KMAC).
214 For those KDF implementations that support it, this parameter
215 sets the MAC output size.
217 The default value, if any, is implementation dependent.
218 The length must never exceed what can be given with a B<size_t>.
220 =item "maxmem_bytes" (B<OSSL_KDF_PARAM_SCRYPT_MAXMEM>) <unsigned integer>
222 Memory-hard password-based KDF algorithms, such as scrypt, use an amount of
223 memory that depends on the load factors provided as input.
224 For those KDF implementations that support it, this B<uint64_t> parameter sets
225 an upper limit on the amount of memory that may be consumed while performing
227 If this memory usage limit is exceeded because the load factors are chosen
228 too high, the key derivation will fail.
230 The default value is implementation dependent.
231 The memory size must never exceed what can be given with a B<size_t>.
237 EVP_KDF_fetch() returns a pointer to a newly fetched B<EVP_KDF>, or
238 NULL if allocation failed.
240 EVP_KDF_provider() returns a pointer to the provider for the KDF, or
243 EVP_KDF_up_ref() returns 1 on success, 0 on error.
245 EVP_KDF_CTX_new() returns either the newly allocated
246 B<EVP_KDF_CTX> structure or NULL if an error occurred.
248 EVP_KDF_CTX_free() and EVP_KDF_CTX_reset() do not return a value.
250 EVP_KDF_CTX_get_kdf_size() returns the output size. B<SIZE_MAX> is returned to indicate
251 that the algorithm produces a variable amount of output; 0 to indicate failure.
253 EVP_KDF_name() returns the name of the KDF, or NULL on error.
255 EVP_KDF_names_do_all() returns 1 if the callback was called for all names. A
256 return value of 0 means that the callback was not called for any names.
258 The remaining functions return 1 for success and 0 or a negative value for
259 failure. In particular, a return value of -2 indicates the operation is not
260 supported by the KDF algorithm.
264 L<OSSL_PROVIDER-default(7)/Key Derivation Function (KDF)>
268 This functionality was added to OpenSSL 3.0.
272 Copyright 2019-2020 The OpenSSL Project Authors. All Rights Reserved.
274 Licensed under the Apache License 2.0 (the "License"). You may not use
275 this file except in compliance with the License. You can obtain a copy
276 in the file LICENSE in the source distribution or at
277 L<https://www.openssl.org/source/license.html>.