xref: /openssl/doc/man3/EVP_SIGNATURE.pod (revision 7ed6de99) 
1=pod
2
3=head1 NAME
4
5EVP_SIGNATURE,
6EVP_SIGNATURE_fetch, EVP_SIGNATURE_free, EVP_SIGNATURE_up_ref,
7EVP_SIGNATURE_is_a, EVP_SIGNATURE_get0_provider,
8EVP_SIGNATURE_do_all_provided, EVP_SIGNATURE_names_do_all,
9EVP_SIGNATURE_get0_name, EVP_SIGNATURE_get0_description,
10EVP_SIGNATURE_gettable_ctx_params, EVP_SIGNATURE_settable_ctx_params
11- Functions to manage EVP_SIGNATURE algorithm objects
12
13=head1 SYNOPSIS
14
15 #include <openssl/evp.h>
16
17 typedef struct evp_signature_st EVP_SIGNATURE;
18
19 EVP_SIGNATURE *EVP_SIGNATURE_fetch(OSSL_LIB_CTX *ctx, const char *algorithm,
20                                    const char *properties);
21 void EVP_SIGNATURE_free(EVP_SIGNATURE *signature);
22 int EVP_SIGNATURE_up_ref(EVP_SIGNATURE *signature);
23 const char *EVP_SIGNATURE_get0_name(const EVP_SIGNATURE *signature);
24 int EVP_SIGNATURE_is_a(const EVP_SIGNATURE *signature, const char *name);
25 OSSL_PROVIDER *EVP_SIGNATURE_get0_provider(const EVP_SIGNATURE *signature);
26 void EVP_SIGNATURE_do_all_provided(OSSL_LIB_CTX *libctx,
27                                    void (*fn)(EVP_SIGNATURE *signature,
28                                               void *arg),
29                                    void *arg);
30 int EVP_SIGNATURE_names_do_all(const EVP_SIGNATURE *signature,
31                                void (*fn)(const char *name, void *data),
32                                void *data);
33 const char *EVP_SIGNATURE_get0_name(const EVP_SIGNATURE *signature);
34 const char *EVP_SIGNATURE_get0_description(const EVP_SIGNATURE *signature);
35 const OSSL_PARAM *EVP_SIGNATURE_gettable_ctx_params(const EVP_SIGNATURE *sig);
36 const OSSL_PARAM *EVP_SIGNATURE_settable_ctx_params(const EVP_SIGNATURE *sig);
37
38=head1 DESCRIPTION
39
40EVP_SIGNATURE_fetch() fetches the implementation for the given
41B<algorithm> from any provider offering it, within the criteria given
42by the B<properties>.
43The algorithm will be one offering functions for performing signature related
44tasks such as signing and verifying.
45See L<crypto(7)/ALGORITHM FETCHING> for further information.
46
47The returned value must eventually be freed with EVP_SIGNATURE_free().
48
49EVP_SIGNATURE_free() decrements the reference count for the B<EVP_SIGNATURE>
50structure. Typically this structure will have been obtained from an earlier call
51to EVP_SIGNATURE_fetch(). If the reference count drops to 0 then the
52structure is freed. If the argument is NULL, nothing is done.
53
54EVP_SIGNATURE_up_ref() increments the reference count for an B<EVP_SIGNATURE>
55structure.
56
57EVP_SIGNATURE_is_a() returns 1 if I<signature> is an implementation of an
58algorithm that's identifiable with I<name>, otherwise 0.
59
60EVP_SIGNATURE_get0_provider() returns the provider that I<signature> was
61fetched from.
62
63EVP_SIGNATURE_do_all_provided() traverses all SIGNATURE implemented by all
64activated providers in the given library context I<libctx>, and for each of the
65implementations, calls the given function I<fn> with the implementation method
66and the given I<arg> as argument.
67
68EVP_SIGNATURE_get0_name() returns the algorithm name from the provided
69implementation for the given I<signature>. Note that the I<signature> may have
70multiple synonyms associated with it. In this case the first name from the
71algorithm definition is returned. Ownership of the returned string is retained
72by the I<signature> object and should not be freed by the caller.
73
74EVP_SIGNATURE_names_do_all() traverses all names for I<signature>, and calls
75I<fn> with each name and I<data>.
76
77EVP_SIGNATURE_get0_description() returns a description of the I<signature>,
78meant for display and human consumption.  The description is at the
79discretion of the I<signature> implementation.
80
81EVP_SIGNATURE_gettable_ctx_params() and EVP_SIGNATURE_settable_ctx_params()
82return a constant L<OSSL_PARAM(3)> array that describes the names and types of key
83parameters that can be retrieved or set by a signature algorithm using
84L<EVP_PKEY_CTX_get_params(3)> and L<EVP_PKEY_CTX_set_params(3)>.
85
86=head1 RETURN VALUES
87
88EVP_SIGNATURE_fetch() returns a pointer to an B<EVP_SIGNATURE> for success
89or B<NULL> for failure.
90
91EVP_SIGNATURE_up_ref() returns 1 for success or 0 otherwise.
92
93EVP_SIGNATURE_names_do_all() returns 1 if the callback was called for all names.
94A return value of 0 means that the callback was not called for any names.
95
96EVP_SIGNATURE_gettable_ctx_params() and EVP_SIGNATURE_settable_ctx_params()
97return a constant L<OSSL_PARAM(3)> array or NULL on error.
98
99=head1 SEE ALSO
100
101L<crypto(7)/ALGORITHM FETCHING>, L<OSSL_PROVIDER(3)>
102
103=head1 HISTORY
104
105The functions described here were added in OpenSSL 3.0.
106
107=head1 COPYRIGHT
108
109Copyright 2019-2024 The OpenSSL Project Authors. All Rights Reserved.
110
111Licensed under the Apache License 2.0 (the "License").  You may not use
112this file except in compliance with the License.  You can obtain a copy
113in the file LICENSE in the source distribution or at
114L<https://www.openssl.org/source/license.html>.
115
116=cut
117