xref: /openssl/doc/man3/RSA_set_method.pod (revision 3dbf8243) 
1=pod
2
3=head1 NAME
4
5RSA_set_default_method, RSA_get_default_method, RSA_set_method,
6RSA_get_method, RSA_PKCS1_OpenSSL, RSA_flags,
7RSA_new_method - select RSA method
8
9=head1 SYNOPSIS
10
11 #include <openssl/rsa.h>
12
13The following functions have been deprecated since OpenSSL 3.0, and can be
14hidden entirely by defining B<OPENSSL_API_COMPAT> with a suitable version value,
15see L<openssl_user_macros(7)>:
16
17 void RSA_set_default_method(const RSA_METHOD *meth);
18
19 const RSA_METHOD *RSA_get_default_method(void);
20
21 int RSA_set_method(RSA *rsa, const RSA_METHOD *meth);
22
23 const RSA_METHOD *RSA_get_method(const RSA *rsa);
24
25 const RSA_METHOD *RSA_PKCS1_OpenSSL(void);
26
27 int RSA_flags(const RSA *rsa);
28
29 RSA *RSA_new_method(ENGINE *engine);
30
31=head1 DESCRIPTION
32
33All of the functions described on this page are deprecated.
34Applications should instead use the OSSL_PROVIDER APIs.
35
36An B<RSA_METHOD> specifies the functions that OpenSSL uses for RSA
37operations. By modifying the method, alternative implementations such as
38hardware accelerators may be used. IMPORTANT: See the NOTES section for
39important information about how these RSA API functions are affected by the
40use of B<ENGINE> API calls.
41
42Initially, the default RSA_METHOD is the OpenSSL internal implementation,
43as returned by RSA_PKCS1_OpenSSL().
44
45RSA_set_default_method() makes B<meth> the default method for all RSA
46structures created later.
47B<NB>: This is true only whilst no ENGINE has
48been set as a default for RSA, so this function is no longer recommended.
49This function is not thread-safe and should not be called at the same time
50as other OpenSSL functions.
51
52RSA_get_default_method() returns a pointer to the current default
53RSA_METHOD. However, the meaningfulness of this result is dependent on
54whether the ENGINE API is being used, so this function is no longer
55recommended.
56
57RSA_set_method() selects B<meth> to perform all operations using the key
58B<rsa>. This will replace the RSA_METHOD used by the RSA key and if the
59previous method was supplied by an ENGINE, the handle to that ENGINE will
60be released during the change. It is possible to have RSA keys that only
61work with certain RSA_METHOD implementations (e.g. from an ENGINE module
62that supports embedded hardware-protected keys), and in such cases
63attempting to change the RSA_METHOD for the key can have unexpected
64results.
65
66RSA_get_method() returns a pointer to the RSA_METHOD being used by B<rsa>.
67This method may or may not be supplied by an ENGINE implementation, but if
68it is, the return value can only be guaranteed to be valid as long as the
69RSA key itself is valid and does not have its implementation changed by
70RSA_set_method().
71
72RSA_flags() returns the B<flags> that are set for B<rsa>'s current
73RSA_METHOD. See the BUGS section.
74
75RSA_new_method() allocates and initializes an RSA structure so that
76B<engine> will be used for the RSA operations. If B<engine> is NULL, the
77default ENGINE for RSA operations is used, and if no default ENGINE is set,
78the RSA_METHOD controlled by RSA_set_default_method() is used.
79
80RSA_flags() returns the B<flags> that are set for B<rsa>'s current method.
81
82RSA_new_method() allocates and initializes an B<RSA> structure so that
83B<method> will be used for the RSA operations. If B<method> is B<NULL>,
84the default method is used.
85
86=head1 THE RSA_METHOD STRUCTURE
87
88 typedef struct rsa_meth_st
89 {
90     /* name of the implementation */
91     const char *name;
92
93     /* encrypt */
94     int (*rsa_pub_enc)(int flen, unsigned char *from,
95                        unsigned char *to, RSA *rsa, int padding);
96
97     /* verify arbitrary data */
98     int (*rsa_pub_dec)(int flen, unsigned char *from,
99                        unsigned char *to, RSA *rsa, int padding);
100
101     /* sign arbitrary data */
102     int (*rsa_priv_enc)(int flen, unsigned char *from,
103                         unsigned char *to, RSA *rsa, int padding);
104
105     /* decrypt */
106     int (*rsa_priv_dec)(int flen, unsigned char *from,
107                         unsigned char *to, RSA *rsa, int padding);
108
109     /* compute r0 = r0 ^ I mod rsa->n (May be NULL for some implementations) */
110     int (*rsa_mod_exp)(BIGNUM *r0, BIGNUM *I, RSA *rsa);
111
112     /* compute r = a ^ p mod m (May be NULL for some implementations) */
113     int (*bn_mod_exp)(BIGNUM *r, BIGNUM *a, const BIGNUM *p,
114                       const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
115
116     /* called at RSA_new */
117     int (*init)(RSA *rsa);
118
119     /* called at RSA_free */
120     int (*finish)(RSA *rsa);
121
122     /*
123      * RSA_FLAG_EXT_PKEY        - rsa_mod_exp is called for private key
124      *                            operations, even if p,q,dmp1,dmq1,iqmp
125      *                            are NULL
126      * RSA_METHOD_FLAG_NO_CHECK - don't check pub/private match
127      */
128     int flags;
129
130     char *app_data; /* ?? */
131
132     int (*rsa_sign)(int type,
133                     const unsigned char *m, unsigned int m_length,
134                     unsigned char *sigret, unsigned int *siglen, const RSA *rsa);
135     int (*rsa_verify)(int dtype,
136                       const unsigned char *m, unsigned int m_length,
137                       const unsigned char *sigbuf, unsigned int siglen,
138                       const RSA *rsa);
139     /* keygen. If NULL built-in RSA key generation will be used */
140     int (*rsa_keygen)(RSA *rsa, int bits, BIGNUM *e, BN_GENCB *cb);
141
142 } RSA_METHOD;
143
144=head1 RETURN VALUES
145
146RSA_PKCS1_OpenSSL(), RSA_PKCS1_null_method(), RSA_get_default_method()
147and RSA_get_method() return pointers to the respective RSA_METHODs.
148
149RSA_set_default_method() returns no value.
150
151RSA_set_method() returns a pointer to the old RSA_METHOD implementation
152that was replaced. However, this return value should probably be ignored
153because if it was supplied by an ENGINE, the pointer could be invalidated
154at any time if the ENGINE is unloaded (in fact it could be unloaded as a
155result of the RSA_set_method() function releasing its handle to the
156ENGINE). For this reason, the return type may be replaced with a B<void>
157declaration in a future release.
158
159RSA_new_method() returns NULL and sets an error code that can be obtained
160by L<ERR_get_error(3)> if the allocation fails. Otherwise
161it returns a pointer to the newly allocated structure.
162
163=head1 BUGS
164
165The behaviour of RSA_flags() is a mis-feature that is left as-is for now
166to avoid creating compatibility problems. RSA functionality, such as the
167encryption functions, are controlled by the B<flags> value in the RSA key
168itself, not by the B<flags> value in the RSA_METHOD attached to the RSA key
169(which is what this function returns). If the flags element of an RSA key
170is changed, the changes will be honoured by RSA functionality but will not
171be reflected in the return value of the RSA_flags() function - in effect
172RSA_flags() behaves more like an RSA_default_flags() function (which does
173not currently exist).
174
175=head1 SEE ALSO
176
177L<RSA_new(3)>
178
179=head1 HISTORY
180
181All of these functions were deprecated in OpenSSL 3.0.
182
183The RSA_null_method(), which was a partial attempt to avoid patent issues,
184was replaced to always return NULL in OpenSSL 1.1.1.
185
186=head1 COPYRIGHT
187
188Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
189
190Licensed under the Apache License 2.0 (the "License").  You may not use
191this file except in compliance with the License.  You can obtain a copy
192in the file LICENSE in the source distribution or at
193L<https://www.openssl.org/source/license.html>.
194
195=cut
196