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 operations. By modifying the method, alternative imple-
mentations such as hardware accelerators may be used. IMPOR-
TANT: 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
implementation, 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 recommended.
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
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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 con-
trolled 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);
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RSA_SET_METHOD(3) OpenSSL RSA_SET_METHOD(3)
/* 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 VALUESRSA_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.
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Otherwise it returns a pointer to the newly allocated struc-
ture.
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 func-
tion, 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 imple-
mentations for use in RSA and other cryptographic algo-
rithms.
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 con-
trolled 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
functionality 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 ALSOrsa(3), RSA_new(3)HISTORYRSA_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 com-
ponents 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()
respectively, and RSA_set_method() and RSA_new_method() were
altered to use ENGINEs rather than RSA_METHODs during
development of the engine version of OpenSSL 0.9.6. For
0.9.7, the handling of defaults in the ENGINE API was res-
tructured 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
transparently overrides the behaviour of defaults in the RSA
API without requiring changing these function prototypes.
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