]> git.ipfire.org Git - thirdparty/openssl.git/blob - doc/man3/EVP_KDF.pod
Don't hold a lock when calling a callback in ossl_namemap_doall_names
[thirdparty/openssl.git] / doc / man3 / EVP_KDF.pod
1 =pod
2
3 =head1 NAME
4
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
13
14 =head1 SYNOPSIS
15
16 #include <openssl/kdf.h>
17
18 typedef struct evp_kdf_st EVP_KDF;
19 typedef struct evp_kdf_ctx_st EVP_KDF_CTX;
20
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),
38 void *arg);
39 int EVP_KDF_names_do_all(const EVP_KDF *kdf,
40 void (*fn)(const char *name, void *data),
41 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);
49
50 =head1 DESCRIPTION
51
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.
54
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.
59
60 =head2 Types
61
62 B<EVP_KDF> is a type that holds the implementation of a KDF.
63
64 B<EVP_KDF_CTX> is a context type that holds the algorithm inputs.
65
66 =head2 Algorithm implementation fetching
67
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.
71
72 See L<OSSL_PROVIDER-default(7)/Key Derivation Function (KDF)> for the lists of
73 algorithms supported by the default provider.
74
75 The returned value must eventually be freed with
76 L<EVP_KDF_free(3)>.
77
78 EVP_KDF_up_ref() increments the reference count of an already fetched
79 KDF.
80
81 EVP_KDF_free() frees a fetched algorithm.
82 NULL is a valid parameter, for which this function is a no-op.
83
84 =head2 Context manipulation functions
85
86 EVP_KDF_CTX_new() creates a new context for the KDF implementation I<kdf>.
87
88 EVP_KDF_CTX_free() frees up the context I<ctx>. If I<ctx> is NULL, nothing
89 is done.
90
91 EVP_KDF_CTX_kdf() returns the B<EVP_KDF> associated with the context
92 I<ctx>.
93
94 =head2 Computing functions
95
96 EVP_KDF_CTX_reset() resets the context to the default state as if the context
97 had just been created.
98
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().
103
104 EVP_KDF_get_params() retrieves details about the implementation
105 I<kdf>.
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
109 simply ignored.
110
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
116 simply ignored.
117
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
123 simply ignored.
124 Also, what happens when a needed parameter isn't passed down is
125 defined by the implementation.
126
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.
133
134 =head2 Information functions
135
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.
140
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.
143
144 EVP_KDF_provider() returns the provider that holds the implementation
145 of the given I<kdf>.
146
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.
151
152 EVP_KDF_number() returns the internal dynamic number assigned to
153 I<kdf>.
154
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.
158
159 EVP_KDF_names_do_all() traverses all names for I<kdf>, and calls
160 I<fn> with each name and I<data>.
161
162 =head1 PARAMETERS
163
164 The standard parameter names are:
165
166 =over 4
167
168 =item "pass" (B<OSSL_KDF_PARAM_PASSWORD>) <octet string>
169
170 Some KDF implementations require a password.
171 For those KDF implementations that support it, this parameter sets the password.
172
173 =item "salt" (B<OSSL_KDF_PARAM_SALT>) <octet string>
174
175 Some KDF implementations can take a salt.
176 For those KDF implementations that support it, this parameter sets the salt.
177
178 The default value, if any, is implementation dependent.
179
180 =item "iter" (B<OSSL_KDF_PARAM_ITER>) <unsigned integer>
181
182 Some KDF implementations require an iteration count.
183 For those KDF implementations that support it, this parameter sets the
184 iteration count.
185
186 The default value, if any, is implementation dependent.
187
188 =item "properties" (B<OSSL_KDF_PARAM_PROPERTIES>) <UTF8 string>
189
190 =item "mac" (B<OSSL_KDF_PARAM_MAC>) <UTF8 string>
191
192 =item "digest" (B<OSSL_KDF_PARAM_DIGEST>) <UTF8 string>
193
194 =item "cipher" (B<OSSL_KDF_PARAM_CIPHER>) <UTF8 string>
195
196 For KDF implementations that use an underlying computation MAC, digest or
197 cipher, these parameters set what the algorithm should be.
198
199 The value is always the name of the intended algorithm,
200 or the properties.
201
202 Note that not all algorithms may support all possible underlying
203 implementations.
204
205 =item "key" (B<OSSL_KDF_PARAM_KEY>) <octet string>
206
207 Some KDF implementations require a key.
208 For those KDF implementations that support it, this octet string parameter
209 sets the key.
210
211 =item "maclen" (B<OSSL_KDF_PARAM_MAC_SIZE>) <unsigned integer>
212
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.
216
217 The default value, if any, is implementation dependent.
218 The length must never exceed what can be given with a B<size_t>.
219
220 =item "maxmem_bytes" (B<OSSL_KDF_PARAM_SCRYPT_MAXMEM>) <unsigned integer>
221
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
226 a key derivation.
227 If this memory usage limit is exceeded because the load factors are chosen
228 too high, the key derivation will fail.
229
230 The default value is implementation dependent.
231 The memory size must never exceed what can be given with a B<size_t>.
232
233 =back
234
235 =head1 RETURN VALUES
236
237 EVP_KDF_fetch() returns a pointer to a newly fetched B<EVP_KDF>, or
238 NULL if allocation failed.
239
240 EVP_KDF_provider() returns a pointer to the provider for the KDF, or
241 NULL on error.
242
243 EVP_KDF_up_ref() returns 1 on success, 0 on error.
244
245 EVP_KDF_CTX_new() returns either the newly allocated
246 B<EVP_KDF_CTX> structure or NULL if an error occurred.
247
248 EVP_KDF_CTX_free() and EVP_KDF_CTX_reset() do not return a value.
249
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.
252
253 EVP_KDF_name() returns the name of the KDF, or NULL on error.
254
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.
257
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.
261
262 =head1 SEE ALSO
263
264 L<OSSL_PROVIDER-default(7)/Key Derivation Function (KDF)>
265
266 =head1 HISTORY
267
268 This functionality was added to OpenSSL 3.0.
269
270 =head1 COPYRIGHT
271
272 Copyright 2019-2020 The OpenSSL Project Authors. All Rights Reserved.
273
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>.
278
279 =cut