Edit File: RSA_set_method.3
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Always turn off hyphenation; it makes .\" way too many mistakes in technical documents. .if n .ad l .nh .SH "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 .SH "SYNOPSIS" .IX Header "SYNOPSIS" .Vb 1 \& #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); .Ve .SH "DESCRIPTION" .IX Header "DESCRIPTION" An \fB\s-1RSA_METHOD\s0\fR specifies the functions that OpenSSL uses for \s-1RSA\s0 operations. By modifying the method, alternative implementations such as hardware accelerators may be used. \s-1IMPORTANT:\s0 See the \s-1NOTES\s0 section for important information about how these \s-1RSA API\s0 functions are affected by the use of \fB\s-1ENGINE\s0\fR \s-1API\s0 calls. .PP Initially, the default \s-1RSA_METHOD\s0 is the OpenSSL internal implementation, as returned by \fBRSA_PKCS1_SSLeay()\fR. .PP \&\fBRSA_set_default_method()\fR makes \fBmeth\fR the default method for all \s-1RSA\s0 structures created later. \fB\s-1NB\s0\fR: This is true only whilst no \s-1ENGINE\s0 has been set as a default for \s-1RSA,\s0 so this function is no longer recommended. .PP \&\fBRSA_get_default_method()\fR returns a pointer to the current default \&\s-1RSA_METHOD.\s0 However, the meaningfulness of this result is dependent on whether the \s-1ENGINE API\s0 is being used, so this function is no longer recommended. .PP \&\fBRSA_set_method()\fR selects \fBmeth\fR to perform all operations using the key \&\fBrsa\fR. This will replace the \s-1RSA_METHOD\s0 used by the \s-1RSA\s0 key and if the previous method was supplied by an \s-1ENGINE,\s0 the handle to that \s-1ENGINE\s0 will be released during the change. It is possible to have \s-1RSA\s0 keys that only work with certain \s-1RSA_METHOD\s0 implementations (eg. from an \s-1ENGINE\s0 module that supports embedded hardware-protected keys), and in such cases attempting to change the \s-1RSA_METHOD\s0 for the key can have unexpected results. .PP \&\fBRSA_get_method()\fR returns a pointer to the \s-1RSA_METHOD\s0 being used by \fBrsa\fR. This method may or may not be supplied by an \s-1ENGINE\s0 implementation, but if it is, the return value can only be guaranteed to be valid as long as the \&\s-1RSA\s0 key itself is valid and does not have its implementation changed by \&\fBRSA_set_method()\fR. .PP \&\fBRSA_flags()\fR returns the \fBflags\fR that are set for \fBrsa\fR's current \&\s-1RSA_METHOD.\s0 See the \s-1BUGS\s0 section. .PP \&\fBRSA_new_method()\fR allocates and initializes an \s-1RSA\s0 structure so that \&\fBengine\fR will be used for the \s-1RSA\s0 operations. If \fBengine\fR is \s-1NULL,\s0 the default \s-1ENGINE\s0 for \s-1RSA\s0 operations is used, and if no default \s-1ENGINE\s0 is set, the \s-1RSA_METHOD\s0 controlled by \fBRSA_set_default_method()\fR is used. .PP \&\fBRSA_flags()\fR returns the \fBflags\fR that are set for \fBrsa\fR's current method. .PP \&\fBRSA_new_method()\fR allocates and initializes an \fB\s-1RSA\s0\fR structure so that \&\fBmethod\fR will be used for the \s-1RSA\s0 operations. If \fBmethod\fR is \fB\s-1NULL\s0\fR, the default method is used. .SH "THE RSA_METHOD STRUCTURE" .IX Header "THE RSA_METHOD STRUCTURE" .Vb 4 \& 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\*(Aqt 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, \& const unsigned char *m, unsigned int m_length, \& unsigned char *sigret, unsigned int *siglen, const RSA *rsa); \& /* verify. For backward compatibility, this is used only \& * if (flags & RSA_FLAG_SIGN_VER) \& */ \& int (*rsa_verify)(int dtype, \& const unsigned char *m, unsigned int m_length, \& const unsigned char *sigbuf, unsigned int siglen, \& const RSA *rsa); \& /* keygen. If NULL builtin RSA key generation will be used */ \& int (*rsa_keygen)(RSA *rsa, int bits, BIGNUM *e, BN_GENCB *cb); \& \& } RSA_METHOD; .Ve .SH "RETURN VALUES" .IX Header "RETURN VALUES" \&\fBRSA_PKCS1_SSLeay()\fR, \fBRSA_PKCS1_null_method()\fR, \fBRSA_get_default_method()\fR and \fBRSA_get_method()\fR return pointers to the respective RSA_METHODs. .PP \&\fBRSA_set_default_method()\fR returns no value. .PP \&\fBRSA_set_method()\fR returns a pointer to the old \s-1RSA_METHOD\s0 implementation that was replaced. However, this return value should probably be ignored because if it was supplied by an \s-1ENGINE,\s0 the pointer could be invalidated at any time if the \s-1ENGINE\s0 is unloaded (in fact it could be unloaded as a result of the \fBRSA_set_method()\fR function releasing its handle to the \&\s-1ENGINE\s0). For this reason, the return type may be replaced with a \fBvoid\fR declaration in a future release. .PP \&\fBRSA_new_method()\fR returns \s-1NULL\s0 and sets an error code that can be obtained by \fBERR_get_error\fR\|(3) if the allocation fails. Otherwise it returns a pointer to the newly allocated structure. .SH "NOTES" .IX Header "NOTES" As of version 0.9.7, \s-1RSA_METHOD\s0 implementations are grouped together with other algorithmic APIs (eg. \s-1DSA_METHOD, EVP_CIPHER,\s0 etc) into \fB\s-1ENGINE\s0\fR modules. If a default \s-1ENGINE\s0 is specified for \s-1RSA\s0 functionality using an \&\s-1ENGINE API\s0 function, that will override any \s-1RSA\s0 defaults set using the \s-1RSA API\s0 (ie. \fBRSA_set_default_method()\fR). For this reason, the \s-1ENGINE API\s0 is the recommended way to control default implementations for use in \s-1RSA\s0 and other cryptographic algorithms. .SH "BUGS" .IX Header "BUGS" The behaviour of \fBRSA_flags()\fR is a mis-feature that is left as-is for now to avoid creating compatibility problems. \s-1RSA\s0 functionality, such as the encryption functions, are controlled by the \fBflags\fR value in the \s-1RSA\s0 key itself, not by the \fBflags\fR value in the \s-1RSA_METHOD\s0 attached to the \s-1RSA\s0 key (which is what this function returns). If the flags element of an \s-1RSA\s0 key is changed, the changes will be honoured by \s-1RSA\s0 functionality but will not be reflected in the return value of the \fBRSA_flags()\fR function \- in effect \&\fBRSA_flags()\fR behaves more like an \fBRSA_default_flags()\fR function (which does not currently exist). .SH "SEE ALSO" .IX Header "SEE ALSO" \&\fBrsa\fR\|(3), \fBRSA_new\fR\|(3) .SH "HISTORY" .IX Header "HISTORY" \&\fBRSA_new_method()\fR and \fBRSA_set_default_method()\fR appeared in SSLeay 0.8. \&\fBRSA_get_default_method()\fR, \fBRSA_set_method()\fR and \fBRSA_get_method()\fR as well as the rsa_sign and rsa_verify components of \s-1RSA_METHOD\s0 were added in OpenSSL 0.9.4. .PP \&\fBRSA_set_default_openssl_method()\fR and \fBRSA_get_default_openssl_method()\fR replaced \fBRSA_set_default_method()\fR and \fBRSA_get_default_method()\fR respectively, and \fBRSA_set_method()\fR and \fBRSA_new_method()\fR were altered to use \&\fB\s-1ENGINE\s0\fRs rather than \fB\s-1RSA_METHOD\s0\fRs during development of the engine version of OpenSSL 0.9.6. For 0.9.7, the handling of defaults in the \s-1ENGINE API\s0 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 \s-1ENGINE API\s0 now transparently overrides the behaviour of defaults in the \s-1RSA API\s0 without requiring changing these function prototypes.