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_reset, EVP_KDF_derive,
8 EVP_KDF_size, EVP_KDF_provider, EVP_KDF_CTX_kdf, EVP_KDF_is_a,
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_reset(EVP_KDF_CTX *ctx);
26 size_t EVP_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(OPENSSL_CTX *libctx, const char *algorithm,
31 const char *properties);
32 int EVP_KDF_is_a(const EVP_KDF *kdf, const char *name);
33 const OSSL_PROVIDER *EVP_KDF_provider(const EVP_KDF *kdf);
34 void EVP_KDF_do_all_provided(OPENSSL_CTX *libctx,
35 void (*fn)(EVP_KDF *kdf, void *arg),
37 void EVP_KDF_names_do_all(const EVP_KDF *kdf,
38 void (*fn)(const char *name, void *data),
40 int EVP_KDF_get_params(EVP_KDF *kdf, OSSL_PARAM params[]);
41 int EVP_KDF_CTX_get_params(EVP_KDF_CTX *ctx, OSSL_PARAM params[]);
42 int EVP_KDF_CTX_set_params(EVP_KDF_CTX *ctx, const OSSL_PARAM params[]);
43 const OSSL_PARAM *EVP_KDF_gettable_params(const EVP_KDF *kdf);
44 const OSSL_PARAM *EVP_KDF_gettable_ctx_params(const EVP_KDF *kdf);
45 const OSSL_PARAM *EVP_KDF_settable_ctx_params(const EVP_KDF *kdf);
46 const OSSL_PROVIDER *EVP_KDF_provider(const EVP_KDF *kdf);
50 The EVP KDF routines are a high level interface to Key Derivation Function
51 algorithms and should be used instead of algorithm-specific functions.
53 After creating a B<EVP_KDF_CTX> for the required algorithm using
54 EVP_KDF_CTX_new(), inputs to the algorithm are supplied
55 using calls to EVP_KDF_CTX_set_params() before
56 calling EVP_KDF_derive() to derive the key.
60 B<EVP_KDF> is a type that holds the implementation of a KDF.
62 B<EVP_KDF_CTX> is a context type that holds the algorithm inputs.
64 =head2 Algorithm implementation fetching
66 EVP_KDF_fetch() fetches an implementation of a KDF I<algorithm>, given
67 a library context I<libctx> and a set of I<properties>.
68 See L<provider(7)/Fetching algorithms> for further information.
70 The returned value must eventually be freed with
73 EVP_KDF_up_ref() increments the reference count of an already fetched
76 EVP_KDF_free() frees a fetched algorithm.
77 NULL is a valid parameter, for which this function is a no-op.
79 =head2 Context manipulation functions
81 EVP_KDF_CTX_new() creates a new context for the KDF implementation I<kdf>.
83 EVP_KDF_CTX_free() frees up the context I<ctx>. If I<ctx> is NULL, nothing
86 EVP_KDF_CTX_kdf() returns the B<EVP_KDF> associated with the context
89 =head2 Computing functions
91 EVP_KDF_reset() resets the context to the default state as if the context
92 had just been created.
94 EVP_KDF_derive() derives I<keylen> bytes of key material and places it in the
95 I<key> buffer. If the algorithm produces a fixed amount of output then an
96 error will occur unless the I<keylen> parameter is equal to that output size,
97 as returned by EVP_KDF_size().
99 EVP_KDF_get_params() retrieves details about the implementation
101 The set of parameters given with I<params> determine exactly what
102 parameters should be retrieved.
103 Note that a parameter that is unknown in the underlying context is
106 EVP_KDF_CTX_get_params() retrieves chosen parameters, given the
107 context I<ctx> and its underlying context.
108 The set of parameters given with I<params> determine exactly what
109 parameters should be retrieved.
110 Note that a parameter that is unknown in the underlying context is
113 EVP_KDF_CTX_set_params() passes chosen parameters to the underlying
114 context, given a context I<ctx>.
115 The set of parameters given with I<params> determine exactly what
116 parameters are passed down.
117 Note that a parameter that is unknown in the underlying context is
119 Also, what happens when a needed parameter isn't passed down is
120 defined by the implementation.
122 EVP_KDF_gettable_params(), EVP_KDF_gettable_ctx_params() and
123 EVP_KDF_settable_ctx_params() get a constant B<OSSL_PARAM> array that
124 decribes the retrievable and settable parameters, i.e. parameters that
125 can be used with EVP_KDF_get_params(), EVP_KDF_CTX_get_params()
126 and EVP_KDF_CTX_set_params(), respectively.
127 See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as parameter descriptor.
129 =head2 Information functions
131 EVP_KDF_size() returns the output size if the algorithm produces a fixed amount
132 of output and B<SIZE_MAX> otherwise. If an error occurs then 0 is returned.
133 For some algorithms an error may result if input parameters necessary to
134 calculate a fixed output size have not yet been supplied.
136 EVP_KDF_is_a() returns 1 if I<kdf> is an implementation of an
137 algorithm that's identifiable with I<name>, otherwise 0.
139 EVP_KDF_provider() returns the provider that holds the implementation
142 EVP_KDF_do_all_provided() traverses all KDF implemented by all activated
143 providers in the given library context I<libctx>, and for each of the
144 implementations, calls the given function I<fn> with the implementation method
145 and the given I<arg> as argument.
147 EVP_KDF_names_do_all() traverses all names for I<kdf>, and calls
148 I<fn> with each name and I<data>.
152 The standard parameter names are:
156 =item "pass" (B<OSSL_KDF_PARAM_PASSWORD>) <octet string>
158 Some KDF implementations require a password.
159 For those KDF implementations that support it, this parameter sets the password.
161 =item "salt" (B<OSSL_KDF_PARAM_SALT>) <octet string>
163 Some KDF implementations can take a salt.
164 For those KDF implementations that support it, this parameter sets the salt.
166 The default value, if any, is implementation dependent.
168 =item "iter" (B<OSSL_KDF_PARAM_ITER>) <unsigned integer>
170 Some KDF implementations require an iteration count.
171 For those KDF implementations that support it, this parameter sets the
174 The default value, if any, is implementation dependent.
176 =item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string>
178 =item "mac" (B<OSSL_KDF_PARAM_MAC>) <UTF8 string>
180 =item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string>
182 For KDF implementations that use an underlying computation MAC or
183 digest, these parameters set what the algorithm should be.
185 The value is always the name of the intended algorithm,
188 Note that not all algorithms may support all possible underlying
191 =item "key" (B<OSSL_KDF_PARAM_KEY>) <octet string>
193 Some KDF implementations require a key.
194 For those KDF implementations that support it, this octet string parameter
197 =item "maclen" (B<OSSL_KDF_PARAM_MAC_SIZE>) <unsigned integer>
199 Used by implementations that use a MAC with a variable output size (KMAC).
200 For those KDF implementations that support it, this parameter
201 sets the MAC output size.
203 The default value, if any, is implementation dependent.
204 The length must never exceed what can be given with a B<size_t>.
206 =item "maxmem_bytes" (B<OSSL_KDF_PARAM_SCRYPT_MAXMEM>) <unsigned integer>
208 Memory-hard password-based KDF algorithms, such as scrypt, use an amount of
209 memory that depends on the load factors provided as input.
210 For those KDF implementations that support it, this B<uint64_t> parameter sets
211 an upper limit on the amount of memory that may be consumed while performing
213 If this memory usage limit is exceeded because the load factors are chosen
214 too high, the key derivation will fail.
216 The default value is implementation dependent.
217 The memory size must never exceed what can be given with a B<size_t>.
223 EVP_KDF_fetch() returns a pointer to a newly fetched B<EVP_KDF>, or
224 NULL if allocation failed.
226 EVP_KDF_provider() returns a pointer to the provider for the KDF, or
229 EVP_KDF_up_ref() returns 1 on success, 0 on error.
231 EVP_KDF_CTX_new() returns either the newly allocated
232 B<EVP_KDF_CTX> structure or NULL if an error occurred.
234 EVP_KDF_CTX_free() and EVP_KDF_reset() do not return a value.
236 EVP_KDF_size() returns the output size. B<SIZE_MAX> is returned to indicate
237 that the algorithm produces a variable amount of output; 0 to indicate failure.
239 The remaining functions return 1 for success and 0 or a negative value for
240 failure. In particular, a return value of -2 indicates the operation is not
241 supported by the KDF algorithm.
246 L<EVP_KDF-TLS1_PRF(7)>
256 This functionality was added to OpenSSL 3.0.
260 Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
262 Licensed under the Apache License 2.0 (the "License"). You may not use
263 this file except in compliance with the License. You can obtain a copy
264 in the file LICENSE in the source distribution or at
265 L<https://www.openssl.org/source/license.html>.