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131 .IX Title "RSA_set_method 3"
132 .TH RSA_set_method 3 "2009-07-23" "0.9.8k" "OpenSSL"
133 .SH "NAME"
134 RSA_set_default_method, RSA_get_default_method, RSA_set_method,
135 RSA_get_method, RSA_PKCS1_SSLeay, RSA_null_method, RSA_flags,
136 RSA_new_method \- select RSA method
137 .SH "SYNOPSIS"
138 .IX Header "SYNOPSIS"
139 .Vb 1
140 \& #include <openssl/rsa.h>
141 .Ve
142 .PP
143 .Vb 1
144 \& void RSA_set_default_method(const RSA_METHOD *meth);
145 .Ve
146 .PP
147 .Vb 1
148 \& RSA_METHOD *RSA_get_default_method(void);
149 .Ve
150 .PP
151 .Vb 1
152 \& int RSA_set_method(RSA *rsa, const RSA_METHOD *meth);
153 .Ve
154 .PP
155 .Vb 1
156 \& RSA_METHOD *RSA_get_method(const RSA *rsa);
157 .Ve
158 .PP
159 .Vb 1
160 \& RSA_METHOD *RSA_PKCS1_SSLeay(void);
161 .Ve
162 .PP
163 .Vb 1
164 \& RSA_METHOD *RSA_null_method(void);
165 .Ve
166 .PP
167 .Vb 1
168 \& int RSA_flags(const RSA *rsa);
169 .Ve
170 .PP
171 .Vb 1
172 \& RSA *RSA_new_method(RSA_METHOD *method);
173 .Ve
174 .SH "DESCRIPTION"
175 .IX Header "DESCRIPTION"
176 An \fB\s-1RSA_METHOD\s0\fR specifies the functions that OpenSSL uses for \s-1RSA\s0
177 operations. By modifying the method, alternative implementations such as
178 hardware accelerators may be used. \s-1IMPORTANT:\s0 See the \s-1NOTES\s0 section for
179 important information about how these \s-1RSA\s0 \s-1API\s0 functions are affected by the
180 use of \fB\s-1ENGINE\s0\fR \s-1API\s0 calls.
181 .PP
182 Initially, the default \s-1RSA_METHOD\s0 is the OpenSSL internal implementation,
183 as returned by \fIRSA_PKCS1_SSLeay()\fR.
184 .PP
185 \&\fIRSA_set_default_method()\fR makes \fBmeth\fR the default method for all \s-1RSA\s0
186 structures created later. \fB\s-1NB\s0\fR: This is true only whilst no \s-1ENGINE\s0 has
187 been set as a default for \s-1RSA\s0, so this function is no longer recommended.
188 .PP
189 \&\fIRSA_get_default_method()\fR returns a pointer to the current default
190 \&\s-1RSA_METHOD\s0. However, the meaningfulness of this result is dependent on
191 whether the \s-1ENGINE\s0 \s-1API\s0 is being used, so this function is no longer
192 recommended.
193 .PP
194 \&\fIRSA_set_method()\fR selects \fBmeth\fR to perform all operations using the key
195 \&\fBrsa\fR. This will replace the \s-1RSA_METHOD\s0 used by the \s-1RSA\s0 key and if the
196 previous method was supplied by an \s-1ENGINE\s0, the handle to that \s-1ENGINE\s0 will
197 be released during the change. It is possible to have \s-1RSA\s0 keys that only
198 work with certain \s-1RSA_METHOD\s0 implementations (eg. from an \s-1ENGINE\s0 module
199 that supports embedded hardware-protected keys), and in such cases
200 attempting to change the \s-1RSA_METHOD\s0 for the key can have unexpected
201 results.
202 .PP
203 \&\fIRSA_get_method()\fR returns a pointer to the \s-1RSA_METHOD\s0 being used by \fBrsa\fR.
204 This method may or may not be supplied by an \s-1ENGINE\s0 implementation, but if
205 it is, the return value can only be guaranteed to be valid as long as the
206 \&\s-1RSA\s0 key itself is valid and does not have its implementation changed by
207 \&\fIRSA_set_method()\fR.
208 .PP
209 \&\fIRSA_flags()\fR returns the \fBflags\fR that are set for \fBrsa\fR's current
210 \&\s-1RSA_METHOD\s0. See the \s-1BUGS\s0 section.
211 .PP
212 \&\fIRSA_new_method()\fR allocates and initializes an \s-1RSA\s0 structure so that
213 \&\fBengine\fR will be used for the \s-1RSA\s0 operations. If \fBengine\fR is \s-1NULL\s0, the
214 default \s-1ENGINE\s0 for \s-1RSA\s0 operations is used, and if no default \s-1ENGINE\s0 is set,
215 the \s-1RSA_METHOD\s0 controlled by \fIRSA_set_default_method()\fR is used.
216 .PP
217 \&\fIRSA_flags()\fR returns the \fBflags\fR that are set for \fBrsa\fR's current method.
218 .PP
219 \&\fIRSA_new_method()\fR allocates and initializes an \fB\s-1RSA\s0\fR structure so that
220 \&\fBmethod\fR will be used for the \s-1RSA\s0 operations. If \fBmethod\fR is \fB\s-1NULL\s0\fR,
221 the default method is used.
222 .SH "THE RSA_METHOD STRUCTURE"
223 .IX Header "THE RSA_METHOD STRUCTURE"
224 .Vb 4
225 \& typedef struct rsa_meth_st
226 \& {
227 \& /* name of the implementation */
228 \& const char *name;
229 .Ve
230 .PP
231 .Vb 3
232 \& /* encrypt */
233 \& int (*rsa_pub_enc)(int flen, unsigned char *from,
234 \& unsigned char *to, RSA *rsa, int padding);
235 .Ve
236 .PP
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 .PP
243 .Vb 3
244 \& /* sign arbitrary data */
245 \& int (*rsa_priv_enc)(int flen, unsigned char *from,
246 \& unsigned char *to, RSA *rsa, int padding);
247 .Ve
248 .PP
249 .Vb 3
250 \& /* decrypt */
251 \& int (*rsa_priv_dec)(int flen, unsigned char *from,
252 \& unsigned char *to, RSA *rsa, int padding);
253 .Ve
254 .PP
255 .Vb 3
256 \& /* compute r0 = r0 ^ I mod rsa->n (May be NULL for some
257 \& implementations) */
258 \& int (*rsa_mod_exp)(BIGNUM *r0, BIGNUM *I, RSA *rsa);
259 .Ve
260 .PP
261 .Vb 3
262 \& /* compute r = a ^ p mod m (May be NULL for some implementations) */
263 \& int (*bn_mod_exp)(BIGNUM *r, BIGNUM *a, const BIGNUM *p,
264 \& const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
265 .Ve
266 .PP
267 .Vb 2
268 \& /* called at RSA_new */
269 \& int (*init)(RSA *rsa);
270 .Ve
271 .PP
272 .Vb 2
273 \& /* called at RSA_free */
274 \& int (*finish)(RSA *rsa);
275 .Ve
276 .PP
277 .Vb 7
278 \& /* RSA_FLAG_EXT_PKEY - rsa_mod_exp is called for private key
279 \& * operations, even if p,q,dmp1,dmq1,iqmp
280 \& * are NULL
281 \& * RSA_FLAG_SIGN_VER - enable rsa_sign and rsa_verify
282 \& * RSA_METHOD_FLAG_NO_CHECK - don't check pub/private match
283 \& */
284 \& int flags;
285 .Ve
286 .PP
287 .Vb 1
288 \& char *app_data; /* ?? */
289 .Ve
290 .PP
291 .Vb 5
292 \& /* sign. For backward compatibility, this is used only
293 \& * if (flags & RSA_FLAG_SIGN_VER)
294 \& */
295 \& int (*rsa_sign)(int type, unsigned char *m, unsigned int m_len,
296 \& unsigned char *sigret, unsigned int *siglen, RSA *rsa);
297 .Ve
298 .PP
299 .Vb 5
300 \& /* verify. For backward compatibility, this is used only
301 \& * if (flags & RSA_FLAG_SIGN_VER)
302 \& */
303 \& int (*rsa_verify)(int type, unsigned char *m, unsigned int m_len,
304 \& unsigned char *sigbuf, unsigned int siglen, RSA *rsa);
305 .Ve
306 .PP
307 .Vb 1
308 \& } RSA_METHOD;
309 .Ve
310 .SH "RETURN VALUES"
311 .IX Header "RETURN VALUES"
312 \&\fIRSA_PKCS1_SSLeay()\fR, \fIRSA_PKCS1_null_method()\fR, \fIRSA_get_default_method()\fR
313 and \fIRSA_get_method()\fR return pointers to the respective RSA_METHODs.
314 .PP
315 \&\fIRSA_set_default_method()\fR returns no value.
316 .PP
317 \&\fIRSA_set_method()\fR returns a pointer to the old \s-1RSA_METHOD\s0 implementation
318 that was replaced. However, this return value should probably be ignored
319 because if it was supplied by an \s-1ENGINE\s0, the pointer could be invalidated
320 at any time if the \s-1ENGINE\s0 is unloaded (in fact it could be unloaded as a
321 result of the \fIRSA_set_method()\fR function releasing its handle to the
322 \&\s-1ENGINE\s0). For this reason, the return type may be replaced with a \fBvoid\fR
323 declaration in a future release.
324 .PP
325 \&\fIRSA_new_method()\fR returns \s-1NULL\s0 and sets an error code that can be obtained
326 by \fIERR_get_error\fR\|(3) if the allocation fails. Otherwise
327 it returns a pointer to the newly allocated structure.
328 .SH "NOTES"
329 .IX Header "NOTES"
330 As of version 0.9.7, \s-1RSA_METHOD\s0 implementations are grouped together with
331 other algorithmic APIs (eg. \s-1DSA_METHOD\s0, \s-1EVP_CIPHER\s0, etc) into \fB\s-1ENGINE\s0\fR
332 modules. If a default \s-1ENGINE\s0 is specified for \s-1RSA\s0 functionality using an
333 \&\s-1ENGINE\s0 \s-1API\s0 function, that will override any \s-1RSA\s0 defaults set using the \s-1RSA\s0
334 \&\s-1API\s0 (ie. \fIRSA_set_default_method()\fR). For this reason, the \s-1ENGINE\s0 \s-1API\s0 is the
335 recommended way to control default implementations for use in \s-1RSA\s0 and other
336 cryptographic algorithms.
337 .SH "BUGS"
338 .IX Header "BUGS"
339 The behaviour of \fIRSA_flags()\fR is a mis-feature that is left as-is for now
340 to avoid creating compatibility problems. \s-1RSA\s0 functionality, such as the
341 encryption functions, are controlled by the \fBflags\fR value in the \s-1RSA\s0 key
342 itself, not by the \fBflags\fR value in the \s-1RSA_METHOD\s0 attached to the \s-1RSA\s0 key
343 (which is what this function returns). If the flags element of an \s-1RSA\s0 key
344 is changed, the changes will be honoured by \s-1RSA\s0 functionality but will not
345 be reflected in the return value of the \fIRSA_flags()\fR function \- in effect
346 \&\fIRSA_flags()\fR behaves more like an \fIRSA_default_flags()\fR function (which does
347 not currently exist).
348 .SH "SEE ALSO"
349 .IX Header "SEE ALSO"
350 \&\fIrsa\fR\|(3), \fIRSA_new\fR\|(3)
351 .SH "HISTORY"
352 .IX Header "HISTORY"
353 \&\fIRSA_new_method()\fR and \fIRSA_set_default_method()\fR appeared in SSLeay 0.8.
354 \&\fIRSA_get_default_method()\fR, \fIRSA_set_method()\fR and \fIRSA_get_method()\fR as
355 well as the rsa_sign and rsa_verify components of \s-1RSA_METHOD\s0 were
356 added in OpenSSL 0.9.4.
357 .PP
358 \&\fIRSA_set_default_openssl_method()\fR and \fIRSA_get_default_openssl_method()\fR
359 replaced \fIRSA_set_default_method()\fR and \fIRSA_get_default_method()\fR
360 respectively, and \fIRSA_set_method()\fR and \fIRSA_new_method()\fR were altered to use
361 \&\fB\s-1ENGINE\s0\fRs rather than \fB\s-1RSA_METHOD\s0\fRs during development of the engine
362 version of OpenSSL 0.9.6. For 0.9.7, the handling of defaults in the \s-1ENGINE\s0
363 \&\s-1API\s0 was restructured so that this change was reversed, and behaviour of the
364 other functions resembled more closely the previous behaviour. The
365 behaviour of defaults in the \s-1ENGINE\s0 \s-1API\s0 now transparently overrides the
366 behaviour of defaults in the \s-1RSA\s0 \s-1API\s0 without requiring changing these
367 function prototypes.