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,
9 EVP_KDF_number, 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_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_number(const EVP_KDF *kdf);
33 int EVP_KDF_is_a(const EVP_KDF *kdf, const char *name);
34 const OSSL_PROVIDER *EVP_KDF_provider(const EVP_KDF *kdf);
35 void EVP_KDF_do_all_provided(OPENSSL_CTX *libctx,
36 void (*fn)(EVP_KDF *kdf, void *arg),
38 void EVP_KDF_names_do_all(const EVP_KDF *kdf,
39 void (*fn)(const char *name, void *data),
41 int EVP_KDF_get_params(EVP_KDF *kdf, OSSL_PARAM params[]);
42 int EVP_KDF_CTX_get_params(EVP_KDF_CTX *ctx, OSSL_PARAM params[]);
43 int EVP_KDF_CTX_set_params(EVP_KDF_CTX *ctx, const OSSL_PARAM params[]);
44 const OSSL_PARAM *EVP_KDF_gettable_params(const EVP_KDF *kdf);
45 const OSSL_PARAM *EVP_KDF_gettable_ctx_params(const EVP_KDF *kdf);
46 const OSSL_PARAM *EVP_KDF_settable_ctx_params(const EVP_KDF *kdf);
47 const OSSL_PROVIDER *EVP_KDF_provider(const EVP_KDF *kdf);
51 The EVP KDF routines are a high level interface to Key Derivation Function
52 algorithms and should be used instead of algorithm-specific functions.
54 After creating a B<EVP_KDF_CTX> for the required algorithm using
55 EVP_KDF_CTX_new(), inputs to the algorithm are supplied
56 using calls to EVP_KDF_CTX_set_params() before
57 calling EVP_KDF_derive() to derive the key.
61 B<EVP_KDF> is a type that holds the implementation of a KDF.
63 B<EVP_KDF_CTX> is a context type that holds the algorithm inputs.
65 =head2 Algorithm implementation fetching
67 EVP_KDF_fetch() fetches an implementation of a KDF I<algorithm>, given
68 a library context I<libctx> and a set of I<properties>.
69 See L<provider(7)/Fetching algorithms> for further information.
71 The returned value must eventually be freed with
74 EVP_KDF_up_ref() increments the reference count of an already fetched
77 EVP_KDF_free() frees a fetched algorithm.
78 NULL is a valid parameter, for which this function is a no-op.
80 =head2 Context manipulation functions
82 EVP_KDF_CTX_new() creates a new context for the KDF implementation I<kdf>.
84 EVP_KDF_CTX_free() frees up the context I<ctx>. If I<ctx> is NULL, nothing
87 EVP_KDF_CTX_kdf() returns the B<EVP_KDF> associated with the context
90 =head2 Computing functions
92 EVP_KDF_reset() resets the context to the default state as if the context
93 had just been created.
95 EVP_KDF_derive() derives I<keylen> bytes of key material and places it in the
96 I<key> buffer. If the algorithm produces a fixed amount of output then an
97 error will occur unless the I<keylen> parameter is equal to that output size,
98 as returned by EVP_KDF_size().
100 EVP_KDF_get_params() retrieves details about the implementation
102 The set of parameters given with I<params> determine exactly what
103 parameters should be retrieved.
104 Note that a parameter that is unknown in the underlying context is
107 EVP_KDF_CTX_get_params() retrieves chosen parameters, given the
108 context I<ctx> and its underlying context.
109 The set of parameters given with I<params> determine exactly what
110 parameters should be retrieved.
111 Note that a parameter that is unknown in the underlying context is
114 EVP_KDF_CTX_set_params() passes chosen parameters to the underlying
115 context, given a context I<ctx>.
116 The set of parameters given with I<params> determine exactly what
117 parameters are passed down.
118 Note that a parameter that is unknown in the underlying context is
120 Also, what happens when a needed parameter isn't passed down is
121 defined by the implementation.
123 EVP_KDF_gettable_params(), EVP_KDF_gettable_ctx_params() and
124 EVP_KDF_settable_ctx_params() get a constant B<OSSL_PARAM> array that
125 decribes the retrievable and settable parameters, i.e. parameters that
126 can be used with EVP_KDF_get_params(), EVP_KDF_CTX_get_params()
127 and EVP_KDF_CTX_set_params(), respectively.
128 See L<OSSL_PARAM(3)> for the use of B<OSSL_PARAM> as parameter descriptor.
130 =head2 Information functions
132 EVP_KDF_size() returns the output size if the algorithm produces a fixed amount
133 of output and B<SIZE_MAX> otherwise. If an error occurs then 0 is returned.
134 For some algorithms an error may result if input parameters necessary to
135 calculate a fixed output size have not yet been supplied.
137 EVP_KDF_is_a() returns 1 if I<kdf> is an implementation of an
138 algorithm that's identifiable with I<name>, otherwise 0.
140 EVP_KDF_provider() returns the provider that holds the implementation
143 EVP_KDF_do_all_provided() traverses all KDF implemented by all activated
144 providers in the given library context I<libctx>, and for each of the
145 implementations, calls the given function I<fn> with the implementation method
146 and the given I<arg> as argument.
148 EVP_KDF_number() returns the internal dynamic number assigned to
151 EVP_KDF_names_do_all() traverses all names for I<kdf>, and calls
152 I<fn> with each name and I<data>.
156 The standard parameter names are:
160 =item "pass" (B<OSSL_KDF_PARAM_PASSWORD>) <octet string>
162 Some KDF implementations require a password.
163 For those KDF implementations that support it, this parameter sets the password.
165 =item "salt" (B<OSSL_KDF_PARAM_SALT>) <octet string>
167 Some KDF implementations can take a salt.
168 For those KDF implementations that support it, this parameter sets the salt.
170 The default value, if any, is implementation dependent.
172 =item "iter" (B<OSSL_KDF_PARAM_ITER>) <unsigned integer>
174 Some KDF implementations require an iteration count.
175 For those KDF implementations that support it, this parameter sets the
178 The default value, if any, is implementation dependent.
180 =item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string>
182 =item "mac" (B<OSSL_KDF_PARAM_MAC>) <UTF8 string>
184 =item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string>
186 =item "cipher" (B<OSSL_KDF_PARAM_CIPHER>) <UTF8 string>
188 For KDF implementations that use an underlying computation MAC, digest or
189 cipher, these parameters set what the algorithm should be.
191 The value is always the name of the intended algorithm,
194 Note that not all algorithms may support all possible underlying
197 =item "key" (B<OSSL_KDF_PARAM_KEY>) <octet string>
199 Some KDF implementations require a key.
200 For those KDF implementations that support it, this octet string parameter
203 =item "maclen" (B<OSSL_KDF_PARAM_MAC_SIZE>) <unsigned integer>
205 Used by implementations that use a MAC with a variable output size (KMAC).
206 For those KDF implementations that support it, this parameter
207 sets the MAC output size.
209 The default value, if any, is implementation dependent.
210 The length must never exceed what can be given with a B<size_t>.
212 =item "maxmem_bytes" (B<OSSL_KDF_PARAM_SCRYPT_MAXMEM>) <unsigned integer>
214 Memory-hard password-based KDF algorithms, such as scrypt, use an amount of
215 memory that depends on the load factors provided as input.
216 For those KDF implementations that support it, this B<uint64_t> parameter sets
217 an upper limit on the amount of memory that may be consumed while performing
219 If this memory usage limit is exceeded because the load factors are chosen
220 too high, the key derivation will fail.
222 The default value is implementation dependent.
223 The memory size must never exceed what can be given with a B<size_t>.
229 EVP_KDF_fetch() returns a pointer to a newly fetched B<EVP_KDF>, or
230 NULL if allocation failed.
232 EVP_KDF_provider() returns a pointer to the provider for the KDF, or
235 EVP_KDF_up_ref() returns 1 on success, 0 on error.
237 EVP_KDF_CTX_new() returns either the newly allocated
238 B<EVP_KDF_CTX> structure or NULL if an error occurred.
240 EVP_KDF_CTX_free() and EVP_KDF_reset() do not return a value.
242 EVP_KDF_size() returns the output size. B<SIZE_MAX> is returned to indicate
243 that the algorithm produces a variable amount of output; 0 to indicate failure.
245 The remaining functions return 1 for success and 0 or a negative value for
246 failure. In particular, a return value of -2 indicates the operation is not
247 supported by the KDF algorithm.
252 L<EVP_KDF-TLS1_PRF(7)>
262 This functionality was added to OpenSSL 3.0.
266 Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
268 Licensed under the Apache License 2.0 (the "License"). You may not use
269 this file except in compliance with the License. You can obtain a copy
270 in the file LICENSE in the source distribution or at
271 L<https://www.openssl.org/source/license.html>.