1RSA_set_method(3)                   OpenSSL                  RSA_set_method(3)
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NAME

6       RSA_set_default_method, RSA_get_default_method, RSA_set_method,
7       RSA_get_method, RSA_PKCS1_SSLeay, RSA_null_method, RSA_flags,
8       RSA_new_method - select RSA method
9

SYNOPSIS

11        #include <openssl/rsa.h>
12
13        void RSA_set_default_method(const RSA_METHOD *meth);
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15        RSA_METHOD *RSA_get_default_method(void);
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17        int RSA_set_method(RSA *rsa, const RSA_METHOD *meth);
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19        RSA_METHOD *RSA_get_method(const RSA *rsa);
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21        RSA_METHOD *RSA_PKCS1_SSLeay(void);
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23        RSA_METHOD *RSA_null_method(void);
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25        int RSA_flags(const RSA *rsa);
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27        RSA *RSA_new_method(RSA_METHOD *method);
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DESCRIPTION

30       An RSA_METHOD specifies the functions that OpenSSL uses for RSA
31       operations. By modifying the method, alternative implementations such
32       as hardware accelerators may be used. IMPORTANT: See the NOTES section
33       for important information about how these RSA API functions are
34       affected by the use of ENGINE API calls.
35
36       Initially, the default RSA_METHOD is the OpenSSL internal
37       implementation, as returned by RSA_PKCS1_SSLeay().
38
39       RSA_set_default_method() makes meth the default method for all RSA
40       structures created later. NB: This is true only whilst no ENGINE has
41       been set as a default for RSA, so this function is no longer
42       recommended.
43
44       RSA_get_default_method() returns a pointer to the current default
45       RSA_METHOD. However, the meaningfulness of this result is dependent on
46       whether the ENGINE API is being used, so this function is no longer
47       recommended.
48
49       RSA_set_method() selects meth to perform all operations using the key
50       rsa. This will replace the RSA_METHOD used by the RSA key and if the
51       previous method was supplied by an ENGINE, the handle to that ENGINE
52       will be released during the change. It is possible to have RSA keys
53       that only work with certain RSA_METHOD implementations (eg. from an
54       ENGINE module that supports embedded hardware-protected keys), and in
55       such cases attempting to change the RSA_METHOD for the key can have
56       unexpected results.
57
58       RSA_get_method() returns a pointer to the RSA_METHOD being used by rsa.
59       This method may or may not be supplied by an ENGINE implementation, but
60       if it is, the return value can only be guaranteed to be valid as long
61       as the RSA key itself is valid and does not have its implementation
62       changed by RSA_set_method().
63
64       RSA_flags() returns the flags that are set for rsa's current
65       RSA_METHOD. See the BUGS section.
66
67       RSA_new_method() allocates and initializes an RSA structure so that
68       engine will be used for the RSA operations. If engine is NULL, the
69       default ENGINE for RSA operations is used, and if no default ENGINE is
70       set, the RSA_METHOD controlled by RSA_set_default_method() is used.
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72       RSA_flags() returns the flags that are set for rsa's current method.
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74       RSA_new_method() allocates and initializes an RSA structure so that
75       method will be used for the RSA operations. If method is NULL, the
76       default method is used.
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THE RSA_METHOD STRUCTURE

79        typedef struct rsa_meth_st
80        {
81            /* name of the implementation */
82               const char *name;
83
84            /* encrypt */
85               int (*rsa_pub_enc)(int flen, unsigned char *from,
86                 unsigned char *to, RSA *rsa, int padding);
87
88            /* verify arbitrary data */
89               int (*rsa_pub_dec)(int flen, unsigned char *from,
90                 unsigned char *to, RSA *rsa, int padding);
91
92            /* sign arbitrary data */
93               int (*rsa_priv_enc)(int flen, unsigned char *from,
94                 unsigned char *to, RSA *rsa, int padding);
95
96            /* decrypt */
97               int (*rsa_priv_dec)(int flen, unsigned char *from,
98                 unsigned char *to, RSA *rsa, int padding);
99
100            /* compute r0 = r0 ^ I mod rsa->n (May be NULL for some
101                                               implementations) */
102               int (*rsa_mod_exp)(BIGNUM *r0, BIGNUM *I, RSA *rsa);
103
104            /* compute r = a ^ p mod m (May be NULL for some implementations) */
105               int (*bn_mod_exp)(BIGNUM *r, BIGNUM *a, const BIGNUM *p,
106                 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
107
108            /* called at RSA_new */
109               int (*init)(RSA *rsa);
110
111            /* called at RSA_free */
112               int (*finish)(RSA *rsa);
113
114            /* RSA_FLAG_EXT_PKEY        - rsa_mod_exp is called for private key
115             *                            operations, even if p,q,dmp1,dmq1,iqmp
116             *                            are NULL
117             * RSA_FLAG_SIGN_VER        - enable rsa_sign and rsa_verify
118             * RSA_METHOD_FLAG_NO_CHECK - don't check pub/private match
119             */
120               int flags;
121
122               char *app_data; /* ?? */
123
124            /* sign. For backward compatibility, this is used only
125             * if (flags & RSA_FLAG_SIGN_VER)
126             */
127               int (*rsa_sign)(int type,
128                       const unsigned char *m, unsigned int m_length,
129                       unsigned char *sigret, unsigned int *siglen, const RSA *rsa);
130            /* verify. For backward compatibility, this is used only
131             * if (flags & RSA_FLAG_SIGN_VER)
132             */
133               int (*rsa_verify)(int dtype,
134                       const unsigned char *m, unsigned int m_length,
135                       const unsigned char *sigbuf, unsigned int siglen,
136                                                                       const RSA *rsa);
137            /* keygen. If NULL builtin RSA key generation will be used */
138               int (*rsa_keygen)(RSA *rsa, int bits, BIGNUM *e, BN_GENCB *cb);
139
140        } RSA_METHOD;
141

RETURN VALUES

143       RSA_PKCS1_SSLeay(), RSA_PKCS1_null_method(), RSA_get_default_method()
144       and RSA_get_method() return pointers to the respective RSA_METHODs.
145
146       RSA_set_default_method() returns no value.
147
148       RSA_set_method() returns a pointer to the old RSA_METHOD implementation
149       that was replaced. However, this return value should probably be
150       ignored because if it was supplied by an ENGINE, the pointer could be
151       invalidated at any time if the ENGINE is unloaded (in fact it could be
152       unloaded as a result of the RSA_set_method() function releasing its
153       handle to the ENGINE). For this reason, the return type may be replaced
154       with a void declaration in a future release.
155
156       RSA_new_method() returns NULL and sets an error code that can be
157       obtained by ERR_get_error(3) if the allocation fails. Otherwise it
158       returns a pointer to the newly allocated structure.
159

NOTES

161       As of version 0.9.7, RSA_METHOD implementations are grouped together
162       with other algorithmic APIs (eg. DSA_METHOD, EVP_CIPHER, etc) into
163       ENGINE modules. If a default ENGINE is specified for RSA functionality
164       using an ENGINE API function, that will override any RSA defaults set
165       using the RSA API (ie.  RSA_set_default_method()). For this reason, the
166       ENGINE API is the recommended way to control default implementations
167       for use in RSA and other cryptographic algorithms.
168

BUGS

170       The behaviour of RSA_flags() is a mis-feature that is left as-is for
171       now to avoid creating compatibility problems. RSA functionality, such
172       as the encryption functions, are controlled by the flags value in the
173       RSA key itself, not by the flags value in the RSA_METHOD attached to
174       the RSA key (which is what this function returns). If the flags element
175       of an RSA key is changed, the changes will be honoured by RSA
176       functionality but will not be reflected in the return value of the
177       RSA_flags() function - in effect RSA_flags() behaves more like an
178       RSA_default_flags() function (which does not currently exist).
179

SEE ALSO

181       rsa(3), RSA_new(3)
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HISTORY

184       RSA_new_method() and RSA_set_default_method() appeared in SSLeay 0.8.
185       RSA_get_default_method(), RSA_set_method() and RSA_get_method() as well
186       as the rsa_sign and rsa_verify components of RSA_METHOD were added in
187       OpenSSL 0.9.4.
188
189       RSA_set_default_openssl_method() and RSA_get_default_openssl_method()
190       replaced RSA_set_default_method() and RSA_get_default_method()
191       respectively, and RSA_set_method() and RSA_new_method() were altered to
192       use ENGINEs rather than RSA_METHODs during development of the engine
193       version of OpenSSL 0.9.6. For 0.9.7, the handling of defaults in the
194       ENGINE API was restructured so that this change was reversed, and
195       behaviour of the other functions resembled more closely the previous
196       behaviour. The behaviour of defaults in the ENGINE API now
197       transparently overrides the behaviour of defaults in the RSA API
198       without requiring changing these function prototypes.
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2021.0.2k                            2017-01-26                 RSA_set_method(3)
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