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>
 #include <openssl/engine.h>
 void RSA_set_default_openssl_method(RSA_METHOD *meth);
 RSA_METHOD *RSA_get_default_openssl_method(void);
 int RSA_set_method(RSA *rsa, ENGINE *engine);
 RSA_METHOD *RSA_get_method(RSA *rsa);
 RSA_METHOD *RSA_PKCS1_SSLeay(void);
 RSA_METHOD *RSA_null_method(void);
 int RSA_flags(RSA *rsa);
 RSA *RSA_new_method(ENGINE *engine);

DESCRIPTION
An RSA_METHOD specifies the functions that OpenSSL uses for RSA operations. By modifying the method, alternative implementations such as hardware accelerators may be used.

Initially, the default is to use the OpenSSL internal implementation. RSA_PKCS1_SSLeay() returns a pointer to that method.

RSA_set_default_openssl_method() makes meth the default method for all RSA structures created later. NB: This is true only whilst the default engine for RSA operations remains as "openssl". ENGINEs provide an encapsulation for implementations of one or more algorithms at a time, and all the RSA functions mentioned here operate within the scope of the default "openssl" engine.

RSA_get_default_openssl_method() returns a pointer to the current default method for the "openssl" engine.

RSA_set_method() selects engine for all operations using the key rsa.

RSA_get_method() returns a pointer to the RSA_METHOD from the currently selected ENGINE for rsa.

RSA_flags() returns the flags that are set for rsa's current method.

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.

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_openssl_method() and RSA_get_method() return pointers to the respective RSA_METHODs.

RSA_set_default_openssl_method() returns no value.

RSA_set_method() selects engine as the engine that will be responsible for all operations using the structure rsa. If this function completes successfully, then the rsa structure will have its own functional reference of engine, so the caller should remember to free their own reference to engine when they are finished with it. NB: An ENGINE's RSA_METHOD can be retrieved (or set) by ENGINE_get_RSA() or ENGINE_set_RSA().

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.

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() respectively, and RSA_set_method() and RSA_new_method() were altered to use ENGINEs rather than RSA_METHODs during development of OpenSSL 0.9.6.