206 lines
7.9 KiB
Text
206 lines
7.9 KiB
Text
=pod
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=head1 NAME
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RSA_set_default_method, RSA_get_default_method, RSA_set_method,
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RSA_get_method, RSA_PKCS1_SSLeay, RSA_null_method, RSA_flags,
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RSA_new_method - select RSA method
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=head1 SYNOPSIS
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#include <openssl/rsa.h>
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void RSA_set_default_method(const RSA_METHOD *meth);
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RSA_METHOD *RSA_get_default_method(void);
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int RSA_set_method(RSA *rsa, const RSA_METHOD *meth);
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RSA_METHOD *RSA_get_method(const RSA *rsa);
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RSA_METHOD *RSA_PKCS1_SSLeay(void);
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RSA_METHOD *RSA_null_method(void);
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int RSA_flags(const RSA *rsa);
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RSA *RSA_new_method(RSA_METHOD *method);
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=head1 DESCRIPTION
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An B<RSA_METHOD> specifies the functions that OpenSSL uses for RSA
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operations. By modifying the method, alternative implementations such as
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hardware accelerators may be used. IMPORTANT: See the NOTES section for
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important information about how these RSA API functions are affected by the
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use of B<ENGINE> API calls.
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Initially, the default RSA_METHOD is the OpenSSL internal implementation,
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as returned by RSA_PKCS1_SSLeay().
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RSA_set_default_method() makes B<meth> the default method for all RSA
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structures created later. B<NB>: This is true only whilst no ENGINE has
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been set as a default for RSA, so this function is no longer recommended.
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RSA_get_default_method() returns a pointer to the current default
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RSA_METHOD. However, the meaningfulness of this result is dependent on
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whether the ENGINE API is being used, so this function is no longer
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recommended.
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RSA_set_method() selects B<meth> to perform all operations using the key
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B<rsa>. This will replace the RSA_METHOD used by the RSA key and if the
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previous method was supplied by an ENGINE, the handle to that ENGINE will
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be released during the change. It is possible to have RSA keys that only
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work with certain RSA_METHOD implementations (eg. from an ENGINE module
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that supports embedded hardware-protected keys), and in such cases
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attempting to change the RSA_METHOD for the key can have unexpected
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results.
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RSA_get_method() returns a pointer to the RSA_METHOD being used by B<rsa>.
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This method may or may not be supplied by an ENGINE implementation, but if
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it is, the return value can only be guaranteed to be valid as long as the
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RSA key itself is valid and does not have its implementation changed by
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RSA_set_method().
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RSA_flags() returns the B<flags> that are set for B<rsa>'s current
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RSA_METHOD. See the BUGS section.
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RSA_new_method() allocates and initializes an RSA structure so that
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B<engine> will be used for the RSA operations. If B<engine> is NULL, the
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default ENGINE for RSA operations is used, and if no default ENGINE is set,
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the RSA_METHOD controlled by RSA_set_default_method() is used.
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RSA_flags() returns the B<flags> that are set for B<rsa>'s current method.
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RSA_new_method() allocates and initializes an B<RSA> structure so that
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B<method> will be used for the RSA operations. If B<method> is B<NULL>,
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the default method is used.
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=head1 THE RSA_METHOD STRUCTURE
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typedef struct rsa_meth_st
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{
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/* name of the implementation */
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const char *name;
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/* encrypt */
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int (*rsa_pub_enc)(int flen, unsigned char *from,
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unsigned char *to, RSA *rsa, int padding);
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/* verify arbitrary data */
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int (*rsa_pub_dec)(int flen, unsigned char *from,
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unsigned char *to, RSA *rsa, int padding);
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/* sign arbitrary data */
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int (*rsa_priv_enc)(int flen, unsigned char *from,
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unsigned char *to, RSA *rsa, int padding);
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/* decrypt */
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int (*rsa_priv_dec)(int flen, unsigned char *from,
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unsigned char *to, RSA *rsa, int padding);
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/* compute r0 = r0 ^ I mod rsa->n (May be NULL for some
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implementations) */
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int (*rsa_mod_exp)(BIGNUM *r0, BIGNUM *I, RSA *rsa);
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/* compute r = a ^ p mod m (May be NULL for some implementations) */
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int (*bn_mod_exp)(BIGNUM *r, BIGNUM *a, const BIGNUM *p,
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const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx);
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/* called at RSA_new */
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int (*init)(RSA *rsa);
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/* called at RSA_free */
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int (*finish)(RSA *rsa);
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/* RSA_FLAG_EXT_PKEY - rsa_mod_exp is called for private key
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* operations, even if p,q,dmp1,dmq1,iqmp
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* are NULL
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* RSA_FLAG_SIGN_VER - enable rsa_sign and rsa_verify
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* RSA_METHOD_FLAG_NO_CHECK - don't check pub/private match
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*/
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int flags;
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char *app_data; /* ?? */
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/* sign. For backward compatibility, this is used only
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* if (flags & RSA_FLAG_SIGN_VER)
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*/
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int (*rsa_sign)(int type,
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const unsigned char *m, unsigned int m_length,
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unsigned char *sigret, unsigned int *siglen, const RSA *rsa);
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/* verify. For backward compatibility, this is used only
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* if (flags & RSA_FLAG_SIGN_VER)
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*/
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int (*rsa_verify)(int dtype,
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const unsigned char *m, unsigned int m_length,
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const unsigned char *sigbuf, unsigned int siglen,
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const RSA *rsa);
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/* keygen. If NULL builtin RSA key generation will be used */
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int (*rsa_keygen)(RSA *rsa, int bits, BIGNUM *e, BN_GENCB *cb);
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} RSA_METHOD;
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=head1 RETURN VALUES
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RSA_PKCS1_SSLeay(), RSA_PKCS1_null_method(), RSA_get_default_method()
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and RSA_get_method() return pointers to the respective RSA_METHODs.
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RSA_set_default_method() returns no value.
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RSA_set_method() returns a pointer to the old RSA_METHOD implementation
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that was replaced. However, this return value should probably be ignored
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because if it was supplied by an ENGINE, the pointer could be invalidated
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at any time if the ENGINE is unloaded (in fact it could be unloaded as a
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result of the RSA_set_method() function releasing its handle to the
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ENGINE). For this reason, the return type may be replaced with a B<void>
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declaration in a future release.
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RSA_new_method() returns NULL and sets an error code that can be obtained
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by L<ERR_get_error(3)|ERR_get_error(3)> if the allocation fails. Otherwise
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it returns a pointer to the newly allocated structure.
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=head1 NOTES
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As of version 0.9.7, RSA_METHOD implementations are grouped together with
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other algorithmic APIs (eg. DSA_METHOD, EVP_CIPHER, etc) into B<ENGINE>
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modules. If a default ENGINE is specified for RSA functionality using an
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ENGINE API function, that will override any RSA defaults set using the RSA
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API (ie. RSA_set_default_method()). For this reason, the ENGINE API is the
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recommended way to control default implementations for use in RSA and other
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cryptographic algorithms.
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=head1 BUGS
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The behaviour of RSA_flags() is a mis-feature that is left as-is for now
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to avoid creating compatibility problems. RSA functionality, such as the
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encryption functions, are controlled by the B<flags> value in the RSA key
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itself, not by the B<flags> value in the RSA_METHOD attached to the RSA key
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(which is what this function returns). If the flags element of an RSA key
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is changed, the changes will be honoured by RSA functionality but will not
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be reflected in the return value of the RSA_flags() function - in effect
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RSA_flags() behaves more like an RSA_default_flags() function (which does
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not currently exist).
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=head1 SEE ALSO
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L<rsa(3)|rsa(3)>, L<RSA_new(3)|RSA_new(3)>
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=head1 HISTORY
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RSA_new_method() and RSA_set_default_method() appeared in SSLeay 0.8.
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RSA_get_default_method(), RSA_set_method() and RSA_get_method() as
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well as the rsa_sign and rsa_verify components of RSA_METHOD were
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added in OpenSSL 0.9.4.
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RSA_set_default_openssl_method() and RSA_get_default_openssl_method()
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replaced RSA_set_default_method() and RSA_get_default_method()
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respectively, and RSA_set_method() and RSA_new_method() were altered to use
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B<ENGINE>s rather than B<RSA_METHOD>s during development of the engine
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version of OpenSSL 0.9.6. For 0.9.7, the handling of defaults in the ENGINE
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API was restructured so that this change was reversed, and behaviour of the
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other functions resembled more closely the previous behaviour. The
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behaviour of defaults in the ENGINE API now transparently overrides the
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behaviour of defaults in the RSA API without requiring changing these
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function prototypes.
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=cut
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