RSA_get_method
RSA_set_method(3) OpenSSL RSA_set_method(3)
NAME
RSA_set_default_method, RSA_get_default_method, RSA_set_method,
RSA_get_method, RSA_PKCS1_SSLeay, RSA_null_method, RSA_flags,
RSA_new_method - select RSA method
SYNOPSIS
#include <openssl/rsa.h>
void RSA_set_default_method(const RSA_METHOD *meth);
RSA_METHOD *RSA_get_default_method(void);
int RSA_set_method(RSA *rsa, const RSA_METHOD *meth);
RSA_METHOD *RSA_get_method(const RSA *rsa);
RSA_METHOD *RSA_PKCS1_SSLeay(void);
RSA_METHOD *RSA_null_method(void);
int RSA_flags(const RSA *rsa);
RSA *RSA_new_method(RSA_METHOD *method);
DESCRIPTION
An RSA_METHOD specifies the functions that OpenSSL uses for RSA opera-
tions. By modifying the method, alternative implementations such as
hardware accelerators may be used. IMPORTANT: See the NOTES section for
important information about how these RSA API functions are affected by
the use of ENGINE API calls.
Initially, the default RSA_METHOD is the OpenSSL internal implementa-
tion, as returned by RSA_PKCS1_SSLeay().
RSA_set_default_method() makes meth the default method for all RSA
structures created later. NB: This is true only whilst no ENGINE has
been set as a default for RSA, so this function is no longer recom-
mended.
RSA_get_default_method() returns a pointer to the current default
RSA_METHOD. However, the meaningfulness of this result is dependant on
whether the ENGINE API is being used, so this function is no longer
recommended.
RSA_set_method() selects meth to perform all operations using the key
rsa. This will replace the RSA_METHOD used by the RSA key and if the
previous method was supplied by an ENGINE, the handle to that ENGINE
will be released during the change. It is possible to have RSA keys
that only work with certain RSA_METHOD implementations (eg. from an
ENGINE module that supports embedded hardware-protected keys), and in
such cases attempting to change the RSA_METHOD for the key can have
unexpected results.
RSA_get_method() returns a pointer to the RSA_METHOD being used by rsa.
This method may or may not be supplied by an 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 RSA_set_method().
RSA_flags() returns the flags that are set for rsa's current
RSA_METHOD. See the BUGS section.
RSA_new_method() allocates and initializes an RSA structure so that
engine will be used for the RSA operations. If engine is NULL, the
default ENGINE for RSA operations is used, and if no default ENGINE is
set, the RSA_METHOD controlled by RSA_set_default_method() is used.
RSA_flags() returns the flags that are set for rsa's current method.
RSA_new_method() allocates and initializes an RSA structure so that
method will be used for the RSA operations. If method is NULL, the
default method is used.
THE RSA_METHOD STRUCTURE
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;
RETURN VALUES
RSA_PKCS1_SSLeay(), RSA_PKCS1_null_method(), RSA_get_default_method()
and RSA_get_method() return pointers to the respective RSA_METHODs.
RSA_set_default_method() returns no value.
RSA_set_method() returns a pointer to the old RSA_METHOD implementation
that was replaced. However, this return value should probably be
ignored because if it was supplied by an ENGINE, the pointer could be
invalidated at any time if the ENGINE is unloaded (in fact it could be
unloaded as a result of the RSA_set_method() function releasing its
handle to the ENGINE). For this reason, the return type may be replaced
with a void declaration in a future release.
RSA_new_method() returns NULL and sets an error code that can be
obtained by ERR_get_error(3) if the allocation fails. Otherwise it
returns a pointer to the newly allocated structure.
NOTES
As of version 0.9.7, RSA_METHOD implementations are grouped together
with other algorithmic APIs (eg. DSA_METHOD, EVP_CIPHER, etc) into
ENGINE modules. If a default ENGINE is specified for RSA functionality
using an ENGINE API function, that will override any RSA defaults set
using the RSA API (ie. RSA_set_default_method()). For this reason, the
ENGINE API is the recommended way to control default implementations
for use in RSA and other cryptographic algorithms.
BUGS
The behaviour of RSA_flags() is a mis-feature that is left as-is for
now to avoid creating compatibility problems. RSA functionality, such
as the encryption functions, are controlled by the flags value in the
RSA key itself, not by the flags value in the RSA_METHOD attached to
the RSA key (which is what this function returns). If the flags element
of an RSA key is changed, the changes will be honoured by RSA function-
ality but will not be reflected in the return value of the RSA_flags()
function - in effect RSA_flags() behaves more like an
RSA_default_flags() function (which does not currently exist).
SEE ALSO
rsa(3), RSA_new(3)
HISTORY
RSA_new_method() and RSA_set_default_method() appeared in SSLeay 0.8.
RSA_get_default_method(), RSA_set_method() and RSA_get_method() as well
as the rsa_sign and rsa_verify components of RSA_METHOD were added in
OpenSSL 0.9.4.
RSA_set_default_openssl_method() and RSA_get_default_openssl_method()
replaced RSA_set_default_method() and RSA_get_default_method() respec-
tively, and RSA_set_method() and RSA_new_method() were altered to use
ENGINEs rather than RSA_METHODs during development of the engine ver-
sion of OpenSSL 0.9.6. For 0.9.7, the handling of defaults in the
ENGINE 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 ENGINE API now transpar-
ently overrides the behaviour of defaults in the RSA API without
requiring changing these function prototypes.
0.9.7a 2002-09-25 RSA_set_method(3)
