xref: /freebsd/crypto/openssl/doc/man3/EVP_PKEY_keygen.pod (revision c66ec88fed842fbaad62c30d510644ceb7bd2d71) 
1=pod
2
3=head1 NAME
4
5EVP_PKEY_keygen_init, EVP_PKEY_keygen, EVP_PKEY_paramgen_init,
6EVP_PKEY_paramgen, EVP_PKEY_CTX_set_cb, EVP_PKEY_CTX_get_cb,
7EVP_PKEY_CTX_get_keygen_info, EVP_PKEY_CTX_set_app_data,
8EVP_PKEY_CTX_get_app_data,
9EVP_PKEY_gen_cb, EVP_PKEY_check, EVP_PKEY_public_check,
10EVP_PKEY_param_check
11- key and parameter generation and check functions
12
13=head1 SYNOPSIS
14
15 #include <openssl/evp.h>
16
17 int EVP_PKEY_keygen_init(EVP_PKEY_CTX *ctx);
18 int EVP_PKEY_keygen(EVP_PKEY_CTX *ctx, EVP_PKEY **ppkey);
19 int EVP_PKEY_paramgen_init(EVP_PKEY_CTX *ctx);
20 int EVP_PKEY_paramgen(EVP_PKEY_CTX *ctx, EVP_PKEY **ppkey);
21
22 typedef int EVP_PKEY_gen_cb(EVP_PKEY_CTX *ctx);
23
24 void EVP_PKEY_CTX_set_cb(EVP_PKEY_CTX *ctx, EVP_PKEY_gen_cb *cb);
25 EVP_PKEY_gen_cb *EVP_PKEY_CTX_get_cb(EVP_PKEY_CTX *ctx);
26
27 int EVP_PKEY_CTX_get_keygen_info(EVP_PKEY_CTX *ctx, int idx);
28
29 void EVP_PKEY_CTX_set_app_data(EVP_PKEY_CTX *ctx, void *data);
30 void *EVP_PKEY_CTX_get_app_data(EVP_PKEY_CTX *ctx);
31
32 int EVP_PKEY_check(EVP_PKEY_CTX *ctx);
33 int EVP_PKEY_public_check(EVP_PKEY_CTX *ctx);
34 int EVP_PKEY_param_check(EVP_PKEY_CTX *ctx);
35
36=head1 DESCRIPTION
37
38The EVP_PKEY_keygen_init() function initializes a public key algorithm
39context using key B<pkey> for a key generation operation.
40
41The EVP_PKEY_keygen() function performs a key generation operation, the
42generated key is written to B<ppkey>.
43
44The functions EVP_PKEY_paramgen_init() and EVP_PKEY_paramgen() are similar
45except parameters are generated.
46
47The function EVP_PKEY_set_cb() sets the key or parameter generation callback
48to B<cb>. The function EVP_PKEY_CTX_get_cb() returns the key or parameter
49generation callback.
50
51The function EVP_PKEY_CTX_get_keygen_info() returns parameters associated
52with the generation operation. If B<idx> is -1 the total number of
53parameters available is returned. Any non negative value returns the value of
54that parameter. EVP_PKEY_CTX_gen_keygen_info() with a nonnegative value for
55B<idx> should only be called within the generation callback.
56
57If the callback returns 0 then the key generation operation is aborted and an
58error occurs. This might occur during a time consuming operation where
59a user clicks on a "cancel" button.
60
61The functions EVP_PKEY_CTX_set_app_data() and EVP_PKEY_CTX_get_app_data() set
62and retrieve an opaque pointer. This can be used to set some application
63defined value which can be retrieved in the callback: for example a handle
64which is used to update a "progress dialog".
65
66EVP_PKEY_check() validates the key-pair given by B<ctx>. This function first tries
67to use customized key check method in B<EVP_PKEY_METHOD> if it's present; otherwise
68it calls a default one defined in B<EVP_PKEY_ASN1_METHOD>.
69
70EVP_PKEY_public_check() validates the public component of the key-pair given by B<ctx>.
71This function first tries to use customized key check method in B<EVP_PKEY_METHOD>
72if it's present; otherwise it calls a default one defined in B<EVP_PKEY_ASN1_METHOD>.
73
74EVP_PKEY_param_check() validates the algorithm parameters of the key-pair given by B<ctx>.
75This function first tries to use customized key check method in B<EVP_PKEY_METHOD>
76if it's present; otherwise it calls a default one defined in B<EVP_PKEY_ASN1_METHOD>.
77
78=head1 NOTES
79
80After the call to EVP_PKEY_keygen_init() or EVP_PKEY_paramgen_init() algorithm
81specific control operations can be performed to set any appropriate parameters
82for the operation.
83
84The functions EVP_PKEY_keygen() and EVP_PKEY_paramgen() can be called more than
85once on the same context if several operations are performed using the same
86parameters.
87
88The meaning of the parameters passed to the callback will depend on the
89algorithm and the specific implementation of the algorithm. Some might not
90give any useful information at all during key or parameter generation. Others
91might not even call the callback.
92
93The operation performed by key or parameter generation depends on the algorithm
94used. In some cases (e.g. EC with a supplied named curve) the "generation"
95option merely sets the appropriate fields in an EVP_PKEY structure.
96
97In OpenSSL an EVP_PKEY structure containing a private key also contains the
98public key components and parameters (if any). An OpenSSL private key is
99equivalent to what some libraries call a "key pair". A private key can be used
100in functions which require the use of a public key or parameters.
101
102=head1 RETURN VALUES
103
104EVP_PKEY_keygen_init(), EVP_PKEY_paramgen_init(), EVP_PKEY_keygen() and
105EVP_PKEY_paramgen() return 1 for success and 0 or a negative value for failure.
106In particular a return value of -2 indicates the operation is not supported by
107the public key algorithm.
108
109EVP_PKEY_check(), EVP_PKEY_public_check() and EVP_PKEY_param_check() return 1
110for success or others for failure. They return -2 if the operation is not supported
111for the specific algorithm.
112
113=head1 EXAMPLES
114
115Generate a 2048 bit RSA key:
116
117 #include <openssl/evp.h>
118 #include <openssl/rsa.h>
119
120 EVP_PKEY_CTX *ctx;
121 EVP_PKEY *pkey = NULL;
122
123 ctx = EVP_PKEY_CTX_new_id(EVP_PKEY_RSA, NULL);
124 if (!ctx)
125     /* Error occurred */
126 if (EVP_PKEY_keygen_init(ctx) <= 0)
127     /* Error */
128 if (EVP_PKEY_CTX_set_rsa_keygen_bits(ctx, 2048) <= 0)
129     /* Error */
130
131 /* Generate key */
132 if (EVP_PKEY_keygen(ctx, &pkey) <= 0)
133     /* Error */
134
135Generate a key from a set of parameters:
136
137 #include <openssl/evp.h>
138 #include <openssl/rsa.h>
139
140 EVP_PKEY_CTX *ctx;
141 ENGINE *eng;
142 EVP_PKEY *pkey = NULL, *param;
143
144 /* Assumed param, eng are set up already */
145 ctx = EVP_PKEY_CTX_new(param, eng);
146 if (!ctx)
147     /* Error occurred */
148 if (EVP_PKEY_keygen_init(ctx) <= 0)
149     /* Error */
150
151 /* Generate key */
152 if (EVP_PKEY_keygen(ctx, &pkey) <= 0)
153     /* Error */
154
155Example of generation callback for OpenSSL public key implementations:
156
157 /* Application data is a BIO to output status to */
158
159 EVP_PKEY_CTX_set_app_data(ctx, status_bio);
160
161 static int genpkey_cb(EVP_PKEY_CTX *ctx)
162 {
163     char c = '*';
164     BIO *b = EVP_PKEY_CTX_get_app_data(ctx);
165     int p = EVP_PKEY_CTX_get_keygen_info(ctx, 0);
166
167     if (p == 0)
168         c = '.';
169     if (p == 1)
170         c = '+';
171     if (p == 2)
172         c = '*';
173     if (p == 3)
174         c = '\n';
175     BIO_write(b, &c, 1);
176     (void)BIO_flush(b);
177     return 1;
178 }
179
180=head1 SEE ALSO
181
182L<EVP_PKEY_CTX_new(3)>,
183L<EVP_PKEY_encrypt(3)>,
184L<EVP_PKEY_decrypt(3)>,
185L<EVP_PKEY_sign(3)>,
186L<EVP_PKEY_verify(3)>,
187L<EVP_PKEY_verify_recover(3)>,
188L<EVP_PKEY_derive(3)>
189
190=head1 HISTORY
191
192These functions were added in OpenSSL 1.0.0.
193
194EVP_PKEY_check(), EVP_PKEY_public_check() and EVP_PKEY_param_check() were added
195in OpenSSL 1.1.1.
196
197=head1 COPYRIGHT
198
199Copyright 2006-2020 The OpenSSL Project Authors. All Rights Reserved.
200
201Licensed under the OpenSSL license (the "License").  You may not use
202this file except in compliance with the License.  You can obtain a copy
203in the file LICENSE in the source distribution or at
204L<https://www.openssl.org/source/license.html>.
205
206=cut
207