.\" $OpenBSD: RSA_set_method.3,v 1.12 2018/04/18 01:07:38 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. 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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: April 18 2018 $ .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_flags , .Nm RSA_new_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 const RSA_METHOD * .Fn RSA_get_default_method void .Ft int .Fo RSA_set_method .Fa "RSA *rsa" .Fa "const RSA_METHOD *meth" .Fc .Ft const RSA_METHOD * .Fo RSA_get_method .Fa "const RSA *rsa" .Fc .Ft const RSA_METHOD * .Fn RSA_PKCS1_SSLeay void .Ft int .Fo RSA_flags .Fa "const RSA *rsa" .Fc .Ft RSA * .Fo RSA_new_method .Fa "ENGINE *engine" .Fc .Sh DESCRIPTION An .Vt RSA_METHOD object contains pointers to the functions used for RSA operations. By default, the internal implementation returned by .Fn RSA_PKCS1_SSLeay is used. By selecting another method, alternative implementations such as hardware accelerators may be used. .Pp .Fn RSA_set_default_method selects .Fa meth as the default method for all .Vt RSA structures created later. If any .Vt ENGINE was registered with .Xr ENGINE_register_RSA 3 that can be successfully initialized, it overrides the default. .Pp .Fn RSA_get_default_method returns a pointer to the current default method, even if it is actually overridded by an .Vt ENGINE . .Pp .Fn RSA_set_method selects .Fa meth to perform all operations using the key .Fa rsa . This replaces the .Vt RSA_METHOD used by the RSA key, and if the previous method was supplied by an .Vt ENGINE , .Xr ENGINE_finish 3 is called on it. 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 engine is used for the RSA operations. If .Fa engine is .Dv NULL , .Xr ENGINE_get_default_RSA 3 is used. If that returns .Dv NULL , the default method controlled by .Fn RSA_set_default_method is used. .Pp The .Dv RSA_METHOD structure is defined as follows: .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_get_default_method , and .Fn RSA_get_method return pointers to the respective .Vt RSA_METHOD . .Pp .Fn RSA_set_method returns 1 on success or 0 on failure. Currently, it cannot fail. .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 ENGINE_get_default_RSA 3 , .Xr ENGINE_register_RSA 3 , .Xr ENGINE_set_default_RSA 3 , .Xr RSA_meth_new 3 , .Xr RSA_new 3 .Sh HISTORY .Fn RSA_set_default_method , .Fn RSA_PKCS1_SSLeay , and .Fn RSA_new_method first appeared in SSLeay 0.8.0. .Fn RSA_flags first appeared in SSLeay 0.9.0. These functions have been available since .Ox 2.4 . .Pp .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 first appeared in OpenSSL 0.9.4 and have been available since .Ox 2.6 . .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.