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138.\" ======================================================================
139.\"
140.IX Title "RSA_set_method 3"
141.TH RSA_set_method 3 "0.9.7a" "2003-02-19" "OpenSSL"
142.UC
143.SH "NAME"
144RSA_set_default_method, RSA_get_default_method, RSA_set_method,
145RSA_get_method, RSA_PKCS1_SSLeay, RSA_null_method, RSA_flags,
146RSA_new_method \- select \s-1RSA\s0 method
147.SH "SYNOPSIS"
148.IX Header "SYNOPSIS"
149.Vb 1
150\& #include <openssl/rsa.h>
151.Ve
152.Vb 1
153\& void RSA_set_default_method(const RSA_METHOD *meth);
154.Ve
155.Vb 1
156\& RSA_METHOD *RSA_get_default_method(void);
157.Ve
158.Vb 1
159\& int RSA_set_method(RSA *rsa, const RSA_METHOD *meth);
160.Ve
161.Vb 1
162\& RSA_METHOD *RSA_get_method(const RSA *rsa);
163.Ve
164.Vb 1
165\& RSA_METHOD *RSA_PKCS1_SSLeay(void);
166.Ve
167.Vb 1
168\& RSA_METHOD *RSA_null_method(void);
169.Ve
170.Vb 1
171\& int RSA_flags(const RSA *rsa);
172.Ve
173.Vb 1
174\& RSA *RSA_new_method(RSA_METHOD *method);
175.Ve
176.SH "DESCRIPTION"
177.IX Header "DESCRIPTION"
178An \fB\s-1RSA_METHOD\s0\fR specifies the functions that OpenSSL uses for \s-1RSA\s0
179operations. By modifying the method, alternative implementations such as
180hardware accelerators may be used. \s-1IMPORTANT:\s0 See the \s-1NOTES\s0 section for
181important information about how these \s-1RSA\s0 \s-1API\s0 functions are affected by the
182use of \fB\s-1ENGINE\s0\fR \s-1API\s0 calls.
183.PP
184Initially, the default \s-1RSA_METHOD\s0 is the OpenSSL internal implementation,
185as returned by \fIRSA_PKCS1_SSLeay()\fR.
186.PP
187\&\fIRSA_set_default_method()\fR makes \fBmeth\fR the default method for all \s-1RSA\s0
188structures created later. \fB\s-1NB\s0\fR: This is true only whilst no \s-1ENGINE\s0 has
189been set as a default for \s-1RSA\s0, so this function is no longer recommended.
190.PP
191\&\fIRSA_get_default_method()\fR returns a pointer to the current default
192\&\s-1RSA_METHOD\s0. However, the meaningfulness of this result is dependant on
193whether the \s-1ENGINE\s0 \s-1API\s0 is being used, so this function is no longer
194recommended.
195.PP
196\&\fIRSA_set_method()\fR selects \fBmeth\fR to perform all operations using the key
197\&\fBrsa\fR. This will replace the \s-1RSA_METHOD\s0 used by the \s-1RSA\s0 key and if the
198previous method was supplied by an \s-1ENGINE\s0, the handle to that \s-1ENGINE\s0 will
199be released during the change. It is possible to have \s-1RSA\s0 keys that only
200work with certain \s-1RSA_METHOD\s0 implementations (eg. from an \s-1ENGINE\s0 module
201that supports embedded hardware-protected keys), and in such cases
202attempting to change the \s-1RSA_METHOD\s0 for the key can have unexpected
203results.
204.PP
205\&\fIRSA_get_method()\fR returns a pointer to the \s-1RSA_METHOD\s0 being used by \fBrsa\fR.
206This method may or may not be supplied by an \s-1ENGINE\s0 implementation, but if
207it is, the return value can only be guaranteed to be valid as long as the
208\&\s-1RSA\s0 key itself is valid and does not have its implementation changed by
209\&\fIRSA_set_method()\fR.
210.PP
211\&\fIRSA_flags()\fR returns the \fBflags\fR that are set for \fBrsa\fR's current
212\&\s-1RSA_METHOD\s0. See the \s-1BUGS\s0 section.
213.PP
214\&\fIRSA_new_method()\fR allocates and initializes an \s-1RSA\s0 structure so that
215\&\fBengine\fR will be used for the \s-1RSA\s0 operations. If \fBengine\fR is \s-1NULL\s0, the
216default \s-1ENGINE\s0 for \s-1RSA\s0 operations is used, and if no default \s-1ENGINE\s0 is set,
217the \s-1RSA_METHOD\s0 controlled by \fIRSA_set_default_method()\fR is used.
218.PP
219\&\fIRSA_flags()\fR returns the \fBflags\fR that are set for \fBrsa\fR's current method.
220.PP
221\&\fIRSA_new_method()\fR allocates and initializes an \fB\s-1RSA\s0\fR structure so that
222\&\fBmethod\fR will be used for the \s-1RSA\s0 operations. If \fBmethod\fR is \fB\s-1NULL\s0\fR,
223the default method is used.
224.SH "THE RSA_METHOD STRUCTURE"
225.IX Header "THE RSA_METHOD STRUCTURE"
226.Vb 4
227\& typedef struct rsa_meth_st
228\& {
229\& /* name of the implementation */
230\& const char *name;
231.Ve
232.Vb 3
233\& /* encrypt */
234\& int (*rsa_pub_enc)(int flen, unsigned char *from,
235\& unsigned char *to, RSA *rsa, int padding);
236.Ve
237.Vb 3
238\& /* verify arbitrary data */
239\& int (*rsa_pub_dec)(int flen, unsigned char *from,
240\& unsigned char *to, RSA *rsa, int padding);
241.Ve
242.Vb 3
243\& /* sign arbitrary data */
244\& int (*rsa_priv_enc)(int flen, unsigned char *from,
245\& unsigned char *to, RSA *rsa, int padding);
246.Ve
247.Vb 3
248\& /* decrypt */
249\& int (*rsa_priv_dec)(int flen, unsigned char *from,
250\& unsigned char *to, RSA *rsa, int padding);
251.Ve
252.Vb 3
253\& /* compute r0 = r0 ^ I mod rsa->n (May be NULL for some
254\& implementations) */
255\& int (*rsa_mod_exp)(BIGNUM *r0, BIGNUM *I, RSA *rsa);
256.Ve
257.Vb 3
258\& /* compute r = a ^ p mod m (May be NULL for some implementations) */
259\& int (*bn_mod_exp)(BIGNUM *r, BIGNUM *a, const BIGNUM *p,
260\& const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
261.Ve
262.Vb 2
263\& /* called at RSA_new */
264\& int (*init)(RSA *rsa);
265.Ve
266.Vb 2
267\& /* called at RSA_free */
268\& int (*finish)(RSA *rsa);
269.Ve
270.Vb 7
271\& /* RSA_FLAG_EXT_PKEY - rsa_mod_exp is called for private key
272\& * operations, even if p,q,dmp1,dmq1,iqmp
273\& * are NULL
274\& * RSA_FLAG_SIGN_VER - enable rsa_sign and rsa_verify
275\& * RSA_METHOD_FLAG_NO_CHECK - don't check pub/private match
276\& */
277\& int flags;
278.Ve
279.Vb 1
280\& char *app_data; /* ?? */
281.Ve
282.Vb 5
283\& /* sign. For backward compatibility, this is used only
284\& * if (flags & RSA_FLAG_SIGN_VER)
285\& */
286\& int (*rsa_sign)(int type, unsigned char *m, unsigned int m_len,
287\& unsigned char *sigret, unsigned int *siglen, RSA *rsa);
288.Ve
289.Vb 5
290\& /* verify. For backward compatibility, this is used only
291\& * if (flags & RSA_FLAG_SIGN_VER)
292\& */
293\& int (*rsa_verify)(int type, unsigned char *m, unsigned int m_len,
294\& unsigned char *sigbuf, unsigned int siglen, RSA *rsa);
295.Ve
296.Vb 1
297\& } RSA_METHOD;
298.Ve
299.SH "RETURN VALUES"
300.IX Header "RETURN VALUES"
301\&\fIRSA_PKCS1_SSLeay()\fR, \fIRSA_PKCS1_null_method()\fR, \fIRSA_get_default_method()\fR
302and \fIRSA_get_method()\fR return pointers to the respective RSA_METHODs.
303.PP
304\&\fIRSA_set_default_method()\fR returns no value.
305.PP
306\&\fIRSA_set_method()\fR returns a pointer to the old \s-1RSA_METHOD\s0 implementation
307that was replaced. However, this return value should probably be ignored
308because if it was supplied by an \s-1ENGINE\s0, the pointer could be invalidated
309at any time if the \s-1ENGINE\s0 is unloaded (in fact it could be unloaded as a
310result of the \fIRSA_set_method()\fR function releasing its handle to the
311\&\s-1ENGINE\s0). For this reason, the return type may be replaced with a \fBvoid\fR
312declaration in a future release.
313.PP
314\&\fIRSA_new_method()\fR returns \s-1NULL\s0 and sets an error code that can be obtained
315by ERR_get_error(3) if the allocation fails. Otherwise
316it returns a pointer to the newly allocated structure.
317.SH "NOTES"
318.IX Header "NOTES"
319As of version 0.9.7, \s-1RSA_METHOD\s0 implementations are grouped together with
320other algorithmic APIs (eg. \s-1DSA_METHOD\s0, \s-1EVP_CIPHER\s0, etc) into \fB\s-1ENGINE\s0\fR
321modules. If a default \s-1ENGINE\s0 is specified for \s-1RSA\s0 functionality using an
322\&\s-1ENGINE\s0 \s-1API\s0 function, that will override any \s-1RSA\s0 defaults set using the \s-1RSA\s0
323\&\s-1API\s0 (ie. \fIRSA_set_default_method()\fR). For this reason, the \s-1ENGINE\s0 \s-1API\s0 is the
324recommended way to control default implementations for use in \s-1RSA\s0 and other
325cryptographic algorithms.
326.SH "BUGS"
327.IX Header "BUGS"
328The behaviour of \fIRSA_flags()\fR is a mis-feature that is left as-is for now
329to avoid creating compatibility problems. \s-1RSA\s0 functionality, such as the
330encryption functions, are controlled by the \fBflags\fR value in the \s-1RSA\s0 key
331itself, not by the \fBflags\fR value in the \s-1RSA_METHOD\s0 attached to the \s-1RSA\s0 key
332(which is what this function returns). If the flags element of an \s-1RSA\s0 key
333is changed, the changes will be honoured by \s-1RSA\s0 functionality but will not
334be reflected in the return value of the \fIRSA_flags()\fR function \- in effect
335\&\fIRSA_flags()\fR behaves more like an \fIRSA_default_flags()\fR function (which does
336not currently exist).
337.SH "SEE ALSO"
338.IX Header "SEE ALSO"
339rsa(3), RSA_new(3)
340.SH "HISTORY"
341.IX Header "HISTORY"
342\&\fIRSA_new_method()\fR and \fIRSA_set_default_method()\fR appeared in SSLeay 0.8.
343\&\fIRSA_get_default_method()\fR, \fIRSA_set_method()\fR and \fIRSA_get_method()\fR as
344well as the rsa_sign and rsa_verify components of \s-1RSA_METHOD\s0 were
345added in OpenSSL 0.9.4.
346.PP
347\&\fIRSA_set_default_openssl_method()\fR and \fIRSA_get_default_openssl_method()\fR
348replaced \fIRSA_set_default_method()\fR and \fIRSA_get_default_method()\fR
349respectively, and \fIRSA_set_method()\fR and \fIRSA_new_method()\fR were altered to use
350\&\fB\s-1ENGINE\s0\fRs rather than \fB\s-1RSA_METHOD\s0\fRs during development of the engine
351version of OpenSSL 0.9.6. For 0.9.7, the handling of defaults in the \s-1ENGINE\s0
352\&\s-1API\s0 was restructured so that this change was reversed, and behaviour of the
353other functions resembled more closely the previous behaviour. The
354behaviour of defaults in the \s-1ENGINE\s0 \s-1API\s0 now transparently overrides the
355behaviour of defaults in the \s-1RSA\s0 \s-1API\s0 without requiring changing these
356function prototypes.