.\" $OpenBSD: RSA_set_method.3,v 1.5 2016/12/11 12:21:48 schwarze Exp $ .\" OpenSSL 99d63d46 Oct 26 13:56:48 2016 -0400 .\" .\" This file was written by Ulf Moeller .\" and Geoff Thorpe . .\" Copyright (c) 2000, 2002, 2007, 2014 The OpenSSL Project. .\" All rights reserved. .\" .\" Redistribution and use in source and binary forms, with or without .\" modification, are permitted provided that the following conditions .\" are met: .\" .\" 1. Redistributions of source code must retain the above copyright .\" notice, this list of conditions and the following disclaimer. .\" .\" 2. Redistributions in binary form must reproduce the above copyright .\" notice, this list of conditions and the following disclaimer in .\" the documentation and/or other materials provided with the .\" distribution. .\" .\" 3. All advertising materials mentioning features or use of this .\" software must display the following acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit. (http://www.openssl.org/)" .\" .\" 4. The names "OpenSSL Toolkit" and "OpenSSL Project" must not be used to .\" endorse or promote products derived from this software without .\" prior written permission. For written permission, please contact .\" openssl-core@openssl.org. .\" .\" 5. Products derived from this software may not be called "OpenSSL" .\" nor may "OpenSSL" appear in their names without prior written .\" permission of the OpenSSL Project. .\" .\" 6. Redistributions of any form whatsoever must retain the following .\" acknowledgment: .\" "This product includes software developed by the OpenSSL Project .\" for use in the OpenSSL Toolkit (http://www.openssl.org/)" .\" .\" THIS SOFTWARE IS PROVIDED BY THE OpenSSL PROJECT ``AS IS'' AND ANY .\" EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE .\" IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR .\" PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE OpenSSL PROJECT OR .\" ITS CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, .\" SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; .\" LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) .\" HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, .\" STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) .\" ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED .\" OF THE POSSIBILITY OF SUCH DAMAGE. .\" .Dd $Mdocdate: December 11 2016 $ .Dt RSA_SET_METHOD 3 .Os .Sh NAME .Nm RSA_set_default_method , .Nm RSA_get_default_method , .Nm RSA_set_method , .Nm RSA_get_method , .Nm RSA_PKCS1_SSLeay , .Nm RSA_null_method , .Nm RSA_flags , .Nm RSA_new_method , .Nm RSA_get_default_openssl_method , .Nm RSA_set_default_openssl_method .Nd select RSA method .Sh SYNOPSIS .In openssl/rsa.h .Ft void .Fo RSA_set_default_method .Fa "const RSA_METHOD *meth" .Fc .Ft RSA_METHOD * .Fn RSA_get_default_method void .Ft int .Fo RSA_set_method .Fa "RSA *rsa" .Fa "const RSA_METHOD *meth" .Fc .Ft RSA_METHOD * .Fo RSA_get_method .Fa "const RSA *rsa" .Fc .Ft RSA_METHOD * .Fn RSA_PKCS1_SSLeay void .Ft RSA_METHOD * .Fn RSA_null_method void .Ft int .Fo RSA_flags .Fa "const RSA *rsa" .Fc .Ft RSA * .Fo RSA_new_method .Fa "RSA_METHOD *meth" .Fc .Sh DESCRIPTION An .Vt RSA_METHOD specifies the functions that OpenSSL uses for RSA operations. By modifying the method, alternative implementations such as hardware accelerators may be used. See the .Sx CAVEATS section for how these RSA API functions are affected by the use of .Xr engine 3 API calls. .Pp Initially, the default .Vt RSA_METHOD is the OpenSSL internal implementation, as returned by .Fn RSA_PKCS1_SSLeay . .Pp .Fn RSA_set_default_method makes .Fa meth the default method for all .Vt RSA structures created later. .Sy NB : This is true only whilst no .Vt ENGINE has been set as a default for RSA, so this function is no longer recommended. .Pp .Fn RSA_get_default_method returns a pointer to the current default .Vt RSA_METHOD . However, the meaningfulness of this result is dependent on whether the .Xr engine 3 API is being used, so this function is no longer recommended. .Pp .Fn RSA_set_method selects .Fa meth to perform all operations using the key .Fa rsa . This will replace the .Vt RSA_METHOD used by the RSA key, and if the previous method was supplied by an .Vt ENGINE , the handle to that .Vt ENGINE will be released during the change. It is possible to have RSA keys that only work with certain .Vt RSA_METHOD implementations (e.g. from an .Vt ENGINE module that supports embedded hardware-protected keys), and in such cases attempting to change the .Vt RSA_METHOD for the key can have unexpected results. .Pp .Fn RSA_get_method returns a pointer to the .Vt RSA_METHOD being used by .Fa rsa . This method may or may not be supplied by an .Vt ENGINE implementation but if it is, the return value can only be guaranteed to be valid as long as the RSA key itself is valid and does not have its implementation changed by .Fn RSA_set_method . .Pp .Fn RSA_flags returns the flags that are set for the current .Vt RSA_METHOD of .Fa rsa . See the .Sx BUGS section. .Pp .Fn RSA_new_method allocates and initializes an .Vt RSA structure so that .Fa meth will be used for the RSA operations. If .Sy engine is NULL, the default ENGINE for RSA operations is used and, if no default ENGINE is set, the RSA_METHOD controlled by .Fn RSA_set_default_method is used. .Pp .Fn RSA_flags returns the .Sy flags that are set for .Fa rsa Ns 's current method. .Pp .Fn RSA_new_method allocates and initializes an .Vt RSA structure so that .Fa meth will be used for the RSA operations. If .Fa meth is .Dv NULL , the default method is used. .Sh THE RSA_METHOD STRUCTURE .Bd -literal typedef struct rsa_meth_st { /* name of the implementation */ const char *name; /* encrypt */ int (*rsa_pub_enc)(int flen, unsigned char *from, unsigned char *to, RSA *rsa, int padding); /* verify arbitrary data */ int (*rsa_pub_dec)(int flen, unsigned char *from, unsigned char *to, RSA *rsa, int padding); /* sign arbitrary data */ int (*rsa_priv_enc)(int flen, unsigned char *from, unsigned char *to, RSA *rsa, int padding); /* decrypt */ int (*rsa_priv_dec)(int flen, unsigned char *from, unsigned char *to, RSA *rsa, int padding); /* compute r0 = r0 ^ I mod rsa->n (May be NULL for some implementations) */ int (*rsa_mod_exp)(BIGNUM *r0, BIGNUM *I, RSA *rsa); /* compute r = a ^ p mod m (May be NULL for some implementations) */ int (*bn_mod_exp)(BIGNUM *r, BIGNUM *a, const BIGNUM *p, const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx); /* called at RSA_new */ int (*init)(RSA *rsa); /* called at RSA_free */ int (*finish)(RSA *rsa); /* RSA_FLAG_EXT_PKEY - rsa_mod_exp is called for private key * operations, even if p,q,dmp1,dmq1,iqmp * are NULL * RSA_FLAG_SIGN_VER - enable rsa_sign and rsa_verify * RSA_METHOD_FLAG_NO_CHECK - don't check pub/private match */ int flags; char *app_data; /* ?? */ /* sign. For backward compatibility, this is used only * if (flags & RSA_FLAG_SIGN_VER) */ int (*rsa_sign)(int type, unsigned char *m, unsigned int m_len, unsigned char *sigret, unsigned int *siglen, RSA *rsa); /* verify. For backward compatibility, this is used only * if (flags & RSA_FLAG_SIGN_VER) */ int (*rsa_verify)(int type, unsigned char *m, unsigned int m_len, unsigned char *sigbuf, unsigned int siglen, RSA *rsa); } RSA_METHOD; .Ed .Sh RETURN VALUES .Fn RSA_PKCS1_SSLeay , .Fn RSA_null_method , .Fn RSA_get_default_method and .Fn RSA_get_method return pointers to the respective .Vt RSA_METHOD . .Pp .Fn RSA_set_method returns a pointer to the old .Vt RSA_METHOD implementation that was replaced. However, this return value should probably be ignored because if it was supplied by an .Vt ENGINE , the pointer could be invalidated at any time if the .Vt ENGINE is unloaded. In fact, it could be unloaded as a result of the .Fn RSA_set_method function releasing its handle to the .Vt ENGINE . For this reason, the return type may be replaced with a .Vt void declaration in a future release. .Pp .Fn RSA_new_method returns .Dv NULL and sets an error code that can be obtained by .Xr ERR_get_error 3 if the allocation fails. Otherwise it returns a pointer to the newly allocated structure. .Sh SEE ALSO .Xr RSA_new 3 .Sh HISTORY .Fn RSA_new_method and .Fn RSA_set_default_method appeared in SSLeay 0.8. .Fn RSA_get_default_method , .Fn RSA_set_method , and .Fn RSA_get_method as well as the .Fa rsa_sign and .Fa rsa_verify components of .Vt RSA_METHOD were added in OpenSSL 0.9.4. .Pp .Fn RSA_set_default_openssl_method and .Fn RSA_get_default_openssl_method replaced .Fn RSA_set_default_method and .Fn RSA_get_default_method respectively, and .Fn RSA_set_method and .Fn RSA_new_method were altered to use .Vt ENGINE Ns s rather than .Vt RSA_METHOD Ns s during development of the .Xr engine 3 version of OpenSSL 0.9.6. For 0.9.7, the handling of defaults in the .Xr engine 3 API was restructured so that this change was reversed, and behaviour of the other functions resembled more closely the previous behaviour. The behaviour of defaults in the .Xr engine 3 API now transparently overrides the behaviour of defaults in the RSA API without requiring changing these function prototypes. .Sh CAVEATS As of version 0.9.7, .Vt RSA_METHOD implementations are grouped together with other algorithmic APIs (e.g.\& .Vt DSA_METHOD or .Vt EVP_CIPHER ) into .Vt ENGINE modules. If a default .Vt ENGINE is specified for RSA functionality using an .Xr engine 3 API function, that will override any RSA defaults set using the RSA API, i.e.\& .Fn RSA_set_default_method . For this reason, the .Xr engine 3 API is the recommended way to control default implementations for use in RSA and other cryptographic algorithms. .Sh BUGS The behaviour of .Fn RSA_flags is a misfeature that is left as-is for now to avoid creating compatibility problems. RSA functionality, such as the encryption functions, are controlled by the .Fa flags value in the .Vt RSA key itself, not by the .Fa flags value in the .Vt RSA_METHOD attached to the RSA key (which is what this function returns). If the flags element of an .Vt RSA key is changed, the changes will be honoured by RSA functionality but will not be reflected in the return value of the .Fn RSA_flags function - in effect .Fn RSA_flags behaves more like a RSA_default_flags() function, which does not currently exist.