5 provider - OpenSSL operation implementation providers
11 #include <openssl/provider.h>
17 A I<provider>, in OpenSSL terms, is a unit of code that provides one
18 or more implementations for various operations for diverse algorithms
19 that one might want to perform.
21 An I<operation> is something one wants to do, such as encryption and
22 decryption, key derivation, MAC calculation, signing and verification,
25 An I<algorithm> is a named method to perform an operation.
26 Very often, the algorithms revolve around cryptographic operations,
27 but may also revolve around other types of operation, such as managing
28 certain types of objects.
32 I<NOTE: This section is mostly interesting for provider authors.>
34 A I<provider> offers an initialization function, as a set of base
35 functions in the form of an B<OSSL_DISPATCH> array, and by extension,
36 a set of B<OSSL_ALGORITHM>s (see L<openssl-core.h(7)>).
37 It may be a dynamically loadable module, or may be built-in, in
38 OpenSSL libraries or in the application.
39 If it's a dynamically loadable module, the initialization function
40 must be named C<OSSL_provider_init> and must be exported.
41 If it's built-in, the initialization function may have any name.
43 The initialization function must have the following signature:
45 int NAME(const OSSL_PROVIDER *provider,
46 const OSSL_DISPATCH *in, const OSSL_DISPATCH **out,
49 I<provider> is the OpenSSL library object for the provider, and works
50 as a handle for everything the OpenSSL libraries need to know about
52 For the provider itself, it may hold some interesting information,
53 and is also passed to some of the functions given in the dispatch
56 I<in> is a dispatch array of base functions offered by the OpenSSL
57 libraries, and the available functions are further described in
60 I<*out> must be assigned a dispatch array of base functions that the
61 provider offers to the OpenSSL libraries.
62 The functions that may be offered are further described in
63 L<provider-base(7)>, and they are the central means of communication
64 between the OpenSSL libraries and the provider.
66 I<*provctx> should be assigned a provider specific context to allow
67 the provider multiple simultaneous uses.
68 This pointer will be passed to various operation functions offered by
71 One of the functions the provider offers to the OpenSSL libraries is
72 the central mechanism for the OpenSSL libraries to get access to
73 operation implementations for diverse algorithms.
74 Its referred to with the number B<OSSL_FUNC_PROVIDER_QUERY_OPERATION>
75 and has the following signature:
77 const OSSL_ALGORITHM *provider_query_operation(void *provctx,
81 I<provctx> is the provider specific context that was passed back by
82 the initialization function.
84 I<operation_id> is an operation identity (see L</Operations> below).
86 I<no_store> is a flag back to the OpenSSL libraries which, when
87 nonzero, signifies that the OpenSSL libraries will not store a
88 reference to the returned data in their internal store of
91 The returned B<OSSL_ALGORITHM> is the foundation of any OpenSSL
92 library API that uses providers for their implementation, most
93 commonly in the I<fetching> type of functions
94 (see L</Fetching algorithms> below).
98 I<NOTE: This section is mostly interesting for provider authors.>
100 Operations are referred to with numbers, via macros with names
101 starting with C<OSSL_OP_>.
103 With each operation comes a set of defined function types that a
104 provider may or may not offer, depending on its needs.
106 Currently available operations are:
112 In the OpenSSL libraries, the corresponding method object is
114 The number for this operation is B<OSSL_OP_DIGEST>.
115 The functions the provider can offer are described in
116 L<provider-digest(7)>
118 =item Symmetric ciphers
120 In the OpenSSL libraries, the corresponding method object is
122 The number for this operation is B<OSSL_OP_CIPHER>.
123 The functions the provider can offer are described in
124 L<provider-cipher(7)>
126 =item Message Authentication Code (MAC)
128 In the OpenSSL libraries, the corresponding method object is
130 The number for this operation is B<OSSL_OP_MAC>.
131 The functions the provider can offer are described in
134 =item Key Derivation Function (KDF)
136 In the OpenSSL libraries, the corresponding method object is
138 The number for this operation is B<OSSL_OP_KDF>.
139 The functions the provider can offer are described in
144 In the OpenSSL libraries, the corresponding method object is
146 The number for this operation is B<OSSL_OP_KEYEXCH>.
147 The functions the provider can offer are described in
148 L<provider-keyexch(7)>
152 =head2 Fetching algorithms
154 =head3 Explicit fetch
156 I<NOTE: This section is mostly interesting to OpenSSL users.>
158 Users of the OpenSSL libraries never query the provider directly for
159 its diverse implementations and dispatch tables.
160 Instead, the diverse OpenSSL APIs often have fetching functions that
161 do the work, and they return an appropriate method object back to the
163 These functions usually have the name C<APINAME_fetch>, where
164 C<APINAME> is the name of the API, for example L<EVP_MD_fetch(3)>.
166 These fetching functions follow a fairly common pattern, where three
167 arguments are passed:
171 =item The library context
173 See L<OPENSSL_CTX(3)> for a more detailed description.
174 This may be NULL to signify the default (global) library context, or a
175 context created by the user.
176 Only providers loaded in this library context (see
177 L<OSSL_PROVIDER_load(3)>) will be considered by the fetching
182 This is most commonly an algorithm name (this is the case for all EVP
183 methods), but may also be called something else.
185 =for comment For example, an OSSL_STORE implementation would use the
186 URI scheme as an identifier.
188 =item A property query string
190 See L<property(7)> for a more detailed description.
191 This is used to select more exactly which providers will get to offer
196 The method object that is fetched can then be used with diverse other
197 functions that use them, for example L<EVP_DigestInit_ex(3)>.
199 =head3 Implicit fetch
201 I<NOTE: This section is mostly interesting to OpenSSL users.>
203 OpenSSL has a number of functions that return a method object with no
204 associated implementation, such as L<EVP_sha256(3)>,
205 L<EVP_blake2b512(3)> or L<EVP_aes_128_cbc(3)>, which are present for
206 compatibility with OpenSSL before version 3.0.
208 When they are used with functions like L<EVP_DigestInit_ex(3)> or
209 L<EVP_CipherInit_ex(3)>, the actual implementation to be used is
210 fetched implicitly using default search criteria.
212 Implicit fetching can also occur with functions such as
213 L<EVP_PKEY_CTX_derive_init_ex(3)> where a NULL algorithm parameter is
215 In this case an algorithm implementation is implicitly fetched using
216 default search criteria and an algorithm name that is consistent with
217 the type of EVP_PKEY being used.
219 =head1 OPENSSL PROVIDERS
221 OpenSSL comes with a set of providers.
222 All the algorithm names mentioned can be used as an algorithm
223 identifier to the appropriate fetching function.
225 =head2 Default provider
227 The default provider is built in as part of the F<libcrypto> library.
228 Should it be needed (if other providers are loaded and offer
229 implementations of the same algorithms), the property "default=yes"
230 can be used as a search criterion for these implementations.
232 It currently offers the following named algorithms:
238 SHA1, SHA224, SHA256, SHA384, SHA512, SHA512-224, SHA512-256,
239 SHA3-224, SHA3-256, SHA3-384, SHA3-512, SHAKE128, SHAKE256, SM3,
240 BLAKE2b512, BLAKE2s256, KMAC128, KMAC256, MD5, MD5-SHA1
242 =item Symmetric ciphers
244 AES-256-ECB, AES-192-ECB, AES-128-ECB, AES-256-CBC, AES-192-CBC,
245 AES-128-CBC, AES-256-OFB, AES-192-OFB, AES-128-OFB, AES-256-CFB,
246 AES-192-CFB, AES-128-CFB, AES-256-CFB1, AES-192-CFB1, AES-128-CFB1,
247 AES-256-CFB8, AES-192-CFB8, AES-128-CFB8, AES-256-CTR, AES-192-CTR,
248 AES-128-CTR, id-aes256-GCM, id-aes192-GCM, id-aes128-GCM
258 The FIPS provider is a dynamically loadable module, and must therefore
259 be loaded explicitly, either in code or through OpenSSL configuration
261 Should it be needed (if other providers are loaded and offer
262 implementations of the same algorithms), the property "fips=yes" can
263 be used as a search criterion for these implementations.
265 It currently offers the following FIPS approved named algorithms:
271 SHA1, SHA224, SHA256, SHA384, SHA512, SHA512-224, SHA512-256,
272 SHA3-224, SHA3-256, SHA3-384, SHA3-512, KMAC128, KMAC256
274 =item Symmetric ciphers
276 AES-256-ECB, AES-192-ECB, AES-128-ECB, AES-256-CBC, AES-192-CBC,
277 AES-128-CBC, AES-256-CTR, AES-192-CTR, AES-128-CTR
281 =head2 Legacy provider
283 The legacy provider is a dynamically loadable module, and must therefore
284 be loaded explicitly, either in code or through OpenSSL configuration
286 Should it be needed (if other providers are loaded and offer
287 implementations of the same algorithms), the property "legacy=yes" can be
288 used as a search criterion for these implementations.
290 It currently offers the following named algorithms:
294 =item Digest algorithms:
296 RIPEMD160, MD2, MD4, MDC2, whirlpool.
304 Fetch any available implementation of SHA256 in the default context:
306 EVP_MD *md = EVP_MD_fetch(NULL, "SHA256", NULL);
308 EVP_MD_meth_free(md);
310 Fetch any available implementation of AES-128-CBC in the default context:
312 EVP_CIPHER *cipher = EVP_CIPHER_fetch(NULL, "AES-128-CBC", NULL);
314 EVP_CIPHER_meth_free(cipher);
316 Fetch an implementation of SHA256 from the default provider in the default
319 EVP_MD *md = EVP_MD_fetch(NULL, "SHA256", "default=yes");
321 EVP_MD_meth_free(md);
323 Fetch an implementation of SHA256 that is not from the default provider in the
326 EVP_MD *md = EVP_MD_fetch(NULL, "SHA256", "default=no");
328 EVP_MD_meth_free(md);
330 Fetch an implementation of SHA256 from the default provider in the specified
333 EVP_MD *md = EVP_MD_fetch(ctx, "SHA256", "default=yes");
335 EVP_MD_meth_free(md);
337 Load the legacy provider into the default context and then fetch an
338 implementation of whirlpool from it:
340 /* This only needs to be done once - usually at application start up */
341 OSSL_PROVIDER *legacy = OSSL_PROVIDER_load(NULL, "legacy");
343 EVP_MD *md = EVP_MD_fetch(NULL, "whirlpool", "legacy=yes");
345 EVP_MD_meth_free(md);
347 Note that in the above example the property string "legacy=yes" is optional
348 since, assuming no other providers have been loaded, the only implementation of
349 the "whirlpool" algorithm is in the "legacy" provider. Also note that the
350 default provider should be explicitly loaded if it is required in addition to
353 /* This only needs to be done once - usually at application start up */
354 OSSL_PROVIDER *legacy = OSSL_PROVIDER_load(NULL, "legacy");
355 OSSL_PROVIDER *default = OSSL_PROVIDER_load(NULL, "default");
357 EVP_MD *md_whirlpool = EVP_MD_fetch(NULL, "whirlpool", NULL);
358 EVP_MD *md_sha256 = EVP_MD_fetch(NULL, "SHA256", NULL);
360 EVP_MD_meth_free(md_whirlpool);
361 EVP_MD_meth_free(md_sha256);
366 L<EVP_DigestInit_ex(3)>, L<EVP_EncryptInit_ex(3)>,
367 L<EVP_PKEY_derive_init_ex(3)>,
369 L<EVP_set_default_properties(3)>,
371 L<EVP_CIPHER_fetch(3)>,
372 L<EVP_KEYMGMT_fetch(3)>,
373 L<openssl-core.h(7)>,
375 L<provider-digest(7)>,
376 L<provider-cipher(7)>,
377 L<provider-keyexch(7)>
381 The concept of providers and everything surrounding them was
382 introduced in OpenSSL 3.0.
386 Copyright 2019 The OpenSSL Project Authors. All Rights Reserved.
388 Licensed under the Apache License 2.0 (the "License"). You may not use
389 this file except in compliance with the License. You can obtain a copy
390 in the file LICENSE in the source distribution or at
391 L<https://www.openssl.org/source/license.html>.