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- =pod
- =head1 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
- =head1 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);
- =head1 DESCRIPTION
- An B<RSA_METHOD> specifies the functions that OpenSSL uses for RSA
- operations. 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 B<ENGINE> API calls.
- Initially, the default RSA_METHOD is the OpenSSL internal implementation,
- as returned by RSA_PKCS1_SSLeay().
- RSA_set_default_method() makes B<meth> the default method for all RSA
- structures created later. B<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 dependent on
- whether the ENGINE API is being used, so this function is no longer
- recommended.
- RSA_set_method() selects B<meth> to perform all operations using the key
- B<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 B<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 B<flags> that are set for B<rsa>'s current
- RSA_METHOD. See the BUGS section.
- RSA_new_method() allocates and initializes an RSA structure so that
- B<engine> will be used for the RSA operations. If B<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 B<flags> that are set for B<rsa>'s current method.
- RSA_new_method() allocates and initializes an B<RSA> structure so that
- B<method> will be used for the RSA operations. If B<method> is B<NULL>,
- the default method is used.
- =head1 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;
- =head1 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 B<void>
- declaration in a future release.
- RSA_new_method() returns NULL and sets an error code that can be obtained
- by L<ERR_get_error(3)|ERR_get_error(3)> if the allocation fails. Otherwise
- it returns a pointer to the newly allocated structure.
- =head1 NOTES
- As of version 0.9.7, RSA_METHOD implementations are grouped together with
- other algorithmic APIs (eg. DSA_METHOD, EVP_CIPHER, etc) into B<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.
- =head1 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 B<flags> value in the RSA key
- itself, not by the B<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).
- =head1 SEE ALSO
- L<rsa(3)|rsa(3)>, L<RSA_new(3)|RSA_new(3)>
- =head1 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()
- respectively, and RSA_set_method() and RSA_new_method() were altered to use
- B<ENGINE>s rather than B<RSA_METHOD>s during development of the engine
- version 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 transparently overrides the
- behaviour of defaults in the RSA API without requiring changing these
- function prototypes.
- =cut
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