xref: /openssl/doc/man3/EVP_PKEY_is_a.pod (revision 317ed1b4) 
1=pod
2
3=head1 NAME
4
5EVP_PKEY_is_a, EVP_PKEY_can_sign, EVP_PKEY_type_names_do_all,
6EVP_PKEY_get0_type_name, EVP_PKEY_get0_description, EVP_PKEY_get0_provider
7- key type and capabilities functions
8
9=head1 SYNOPSIS
10
11 #include <openssl/evp.h>
12
13 int EVP_PKEY_is_a(const EVP_PKEY *pkey, const char *name);
14 int EVP_PKEY_can_sign(const EVP_PKEY *pkey);
15 int EVP_PKEY_type_names_do_all(const EVP_PKEY *pkey,
16                                void (*fn)(const char *name, void *data),
17                                void *data);
18 const char *EVP_PKEY_get0_type_name(const EVP_PKEY *key);
19 const char *EVP_PKEY_get0_description(const EVP_PKEY *key);
20 const OSSL_PROVIDER *EVP_PKEY_get0_provider(const EVP_PKEY *key);
21
22=head1 DESCRIPTION
23
24EVP_PKEY_is_a() checks if the key type of I<pkey> is I<name>.
25
26EVP_PKEY_can_sign() checks if the functionality for the key type of
27I<pkey> supports signing.  No other check is done, such as whether
28I<pkey> contains a private key.
29
30EVP_PKEY_type_names_do_all() traverses all names for I<pkey>'s key type, and
31calls I<fn> with each name and I<data>.  For example, an RSA B<EVP_PKEY> may
32be named both C<RSA> and C<rsaEncryption>.
33The order of the names depends on the provider implementation that holds
34the key.
35
36EVP_PKEY_get0_type_name() returns the first key type name that is found
37for the given I<pkey>. Note that the I<pkey> may have multiple synonyms
38associated with it. In this case it depends on the provider implementation
39that holds the key which one will be returned.
40Ownership of the returned string is retained by the I<pkey> object and should
41not be freed by the caller.
42
43EVP_PKEY_get0_description() returns a description of the type of B<EVP_PKEY>,
44meant for display and human consumption.  The description is at the
45discretion of the key type implementation.
46
47EVP_PKEY_get0_provider() returns the provider of the B<EVP_PKEY>'s
48L<EVP_KEYMGMT(3)>.
49
50=head1 RETURN VALUES
51
52EVP_PKEY_is_a() returns 1 if I<pkey> has the key type I<name>,
53otherwise 0.
54
55EVP_PKEY_can_sign() returns 1 if the I<pkey> key type functionality
56supports signing, otherwise 0.
57
58EVP_PKEY_get0_type_name() returns the name that is found or NULL on error.
59
60EVP_PKEY_get0_description() returns the description if found or NULL if not.
61
62EVP_PKEY_get0_provider() returns the provider if found or NULL if not.
63
64EVP_PKEY_type_names_do_all() returns 1 if the callback was called for all
65names. A return value of 0 means that the callback was not called for any
66names.
67
68=head1 EXAMPLES
69
70=head2 EVP_PKEY_is_a()
71
72The loaded providers and what key types they support will ultimately
73determine what I<name> is possible to use with EVP_PKEY_is_a().  We do know
74that the default provider supports RSA, DH, DSA and EC keys, so we can use
75this as an crude example:
76
77 #include <openssl/evp.h>
78
79 ...
80     /* |pkey| is an EVP_PKEY* */
81     if (EVP_PKEY_is_a(pkey, "RSA")) {
82         BIGNUM *modulus = NULL;
83         if (EVP_PKEY_get_bn_param(pkey, "n", &modulus))
84             /* do whatever with the modulus */
85         BN_free(modulus);
86     }
87
88=head2 EVP_PKEY_can_sign()
89
90 #include <openssl/evp.h>
91
92 ...
93     /* |pkey| is an EVP_PKEY* */
94     if (!EVP_PKEY_can_sign(pkey)) {
95         fprintf(stderr, "Not a signing key!");
96         exit(1);
97     }
98     /* Sign something... */
99
100=head1 HISTORY
101
102The functions described here were added in OpenSSL 3.0.
103
104=head1 COPYRIGHT
105
106Copyright 2020-2021 The OpenSSL Project Authors. All Rights Reserved.
107
108Licensed under the Apache License 2.0 (the "License").  You may not use
109this file except in compliance with the License.  You can obtain a copy
110in the file LICENSE in the source distribution or at
111L<https://www.openssl.org/source/license.html>.
112
113=cut
114