1=pod 2 3=head1 NAME 4 5RSA_set_default_method, RSA_get_default_method, RSA_set_method, 6RSA_get_method, RSA_PKCS1_SSLeay, RSA_null_method, RSA_flags, 7RSA_new_method - select RSA method 8 9=head1 SYNOPSIS 10 11 #include <openssl/rsa.h> 12 13 void RSA_set_default_method(const RSA_METHOD *meth); 14 15 RSA_METHOD *RSA_get_default_method(void); 16 17 int RSA_set_method(RSA *rsa, const RSA_METHOD *meth); 18 19 RSA_METHOD *RSA_get_method(const RSA *rsa); 20 21 RSA_METHOD *RSA_PKCS1_SSLeay(void); 22 23 RSA_METHOD *RSA_null_method(void); 24 25 int RSA_flags(const RSA *rsa); 26 27 RSA *RSA_new_method(RSA_METHOD *method); 28 29=head1 DESCRIPTION 30 31An B<RSA_METHOD> specifies the functions that OpenSSL uses for RSA 32operations. By modifying the method, alternative implementations such as 33hardware accelerators may be used. IMPORTANT: See the NOTES section for 34important information about how these RSA API functions are affected by the 35use of B<ENGINE> API calls. 36 37Initially, the default RSA_METHOD is the OpenSSL internal implementation, 38as returned by RSA_PKCS1_SSLeay(). 39 40RSA_set_default_method() makes B<meth> the default method for all RSA 41structures created later. B<NB>: This is true only whilst no ENGINE has 42been set as a default for RSA, so this function is no longer recommended. 43 44RSA_get_default_method() returns a pointer to the current default 45RSA_METHOD. However, the meaningfulness of this result is dependent on 46whether the ENGINE API is being used, so this function is no longer 47recommended. 48 49RSA_set_method() selects B<meth> to perform all operations using the key 50B<rsa>. This will replace the RSA_METHOD used by the RSA key and if the 51previous method was supplied by an ENGINE, the handle to that ENGINE will 52be released during the change. It is possible to have RSA keys that only 53work with certain RSA_METHOD implementations (eg. from an ENGINE module 54that supports embedded hardware-protected keys), and in such cases 55attempting to change the RSA_METHOD for the key can have unexpected 56results. 57 58RSA_get_method() returns a pointer to the RSA_METHOD being used by B<rsa>. 59This method may or may not be supplied by an ENGINE implementation, but if 60it is, the return value can only be guaranteed to be valid as long as the 61RSA key itself is valid and does not have its implementation changed by 62RSA_set_method(). 63 64RSA_flags() returns the B<flags> that are set for B<rsa>'s current 65RSA_METHOD. See the BUGS section. 66 67RSA_new_method() allocates and initializes an RSA structure so that 68B<engine> will be used for the RSA operations. If B<engine> is NULL, the 69default ENGINE for RSA operations is used, and if no default ENGINE is set, 70the RSA_METHOD controlled by RSA_set_default_method() is used. 71 72RSA_flags() returns the B<flags> that are set for B<rsa>'s current method. 73 74RSA_new_method() allocates and initializes an B<RSA> structure so that 75B<method> will be used for the RSA operations. If B<method> is B<NULL>, 76the default method is used. 77 78=head1 THE RSA_METHOD STRUCTURE 79 80 typedef struct rsa_meth_st 81 { 82 /* name of the implementation */ 83 const char *name; 84 85 /* encrypt */ 86 int (*rsa_pub_enc)(int flen, unsigned char *from, 87 unsigned char *to, RSA *rsa, int padding); 88 89 /* verify arbitrary data */ 90 int (*rsa_pub_dec)(int flen, unsigned char *from, 91 unsigned char *to, RSA *rsa, int padding); 92 93 /* sign arbitrary data */ 94 int (*rsa_priv_enc)(int flen, unsigned char *from, 95 unsigned char *to, RSA *rsa, int padding); 96 97 /* decrypt */ 98 int (*rsa_priv_dec)(int flen, unsigned char *from, 99 unsigned char *to, RSA *rsa, int padding); 100 101 /* compute r0 = r0 ^ I mod rsa->n (May be NULL for some 102 implementations) */ 103 int (*rsa_mod_exp)(BIGNUM *r0, BIGNUM *I, RSA *rsa); 104 105 /* compute r = a ^ p mod m (May be NULL for some implementations) */ 106 int (*bn_mod_exp)(BIGNUM *r, BIGNUM *a, const BIGNUM *p, 107 const BIGNUM *m, BN_CTX *ctx, BN_MONT_CTX *m_ctx); 108 109 /* called at RSA_new */ 110 int (*init)(RSA *rsa); 111 112 /* called at RSA_free */ 113 int (*finish)(RSA *rsa); 114 115 /* RSA_FLAG_EXT_PKEY - rsa_mod_exp is called for private key 116 * operations, even if p,q,dmp1,dmq1,iqmp 117 * are NULL 118 * RSA_FLAG_SIGN_VER - enable rsa_sign and rsa_verify 119 * RSA_METHOD_FLAG_NO_CHECK - don't check pub/private match 120 */ 121 int flags; 122 123 char *app_data; /* ?? */ 124 125 /* sign. For backward compatibility, this is used only 126 * if (flags & RSA_FLAG_SIGN_VER) 127 */ 128 int (*rsa_sign)(int type, 129 const unsigned char *m, unsigned int m_length, 130 unsigned char *sigret, unsigned int *siglen, const RSA *rsa); 131 /* verify. For backward compatibility, this is used only 132 * if (flags & RSA_FLAG_SIGN_VER) 133 */ 134 int (*rsa_verify)(int dtype, 135 const unsigned char *m, unsigned int m_length, 136 const unsigned char *sigbuf, unsigned int siglen, 137 const RSA *rsa); 138 /* keygen. If NULL builtin RSA key generation will be used */ 139 int (*rsa_keygen)(RSA *rsa, int bits, BIGNUM *e, BN_GENCB *cb); 140 141 } RSA_METHOD; 142 143=head1 RETURN VALUES 144 145RSA_PKCS1_SSLeay(), RSA_PKCS1_null_method(), RSA_get_default_method() 146and RSA_get_method() return pointers to the respective RSA_METHODs. 147 148RSA_set_default_method() returns no value. 149 150RSA_set_method() returns a pointer to the old RSA_METHOD implementation 151that was replaced. However, this return value should probably be ignored 152because if it was supplied by an ENGINE, the pointer could be invalidated 153at any time if the ENGINE is unloaded (in fact it could be unloaded as a 154result of the RSA_set_method() function releasing its handle to the 155ENGINE). For this reason, the return type may be replaced with a B<void> 156declaration in a future release. 157 158RSA_new_method() returns NULL and sets an error code that can be obtained 159by L<ERR_get_error(3)|ERR_get_error(3)> if the allocation fails. Otherwise 160it returns a pointer to the newly allocated structure. 161 162=head1 NOTES 163 164As of version 0.9.7, RSA_METHOD implementations are grouped together with 165other algorithmic APIs (eg. DSA_METHOD, EVP_CIPHER, etc) into B<ENGINE> 166modules. If a default ENGINE is specified for RSA functionality using an 167ENGINE API function, that will override any RSA defaults set using the RSA 168API (ie. RSA_set_default_method()). For this reason, the ENGINE API is the 169recommended way to control default implementations for use in RSA and other 170cryptographic algorithms. 171 172=head1 BUGS 173 174The behaviour of RSA_flags() is a mis-feature that is left as-is for now 175to avoid creating compatibility problems. RSA functionality, such as the 176encryption functions, are controlled by the B<flags> value in the RSA key 177itself, not by the B<flags> value in the RSA_METHOD attached to the RSA key 178(which is what this function returns). If the flags element of an RSA key 179is changed, the changes will be honoured by RSA functionality but will not 180be reflected in the return value of the RSA_flags() function - in effect 181RSA_flags() behaves more like an RSA_default_flags() function (which does 182not currently exist). 183 184=head1 SEE ALSO 185 186L<rsa(3)|rsa(3)>, L<RSA_new(3)|RSA_new(3)> 187 188=head1 HISTORY 189 190RSA_new_method() and RSA_set_default_method() appeared in SSLeay 0.8. 191RSA_get_default_method(), RSA_set_method() and RSA_get_method() as 192well as the rsa_sign and rsa_verify components of RSA_METHOD were 193added in OpenSSL 0.9.4. 194 195RSA_set_default_openssl_method() and RSA_get_default_openssl_method() 196replaced RSA_set_default_method() and RSA_get_default_method() 197respectively, and RSA_set_method() and RSA_new_method() were altered to use 198B<ENGINE>s rather than B<RSA_METHOD>s during development of the engine 199version of OpenSSL 0.9.6. For 0.9.7, the handling of defaults in the ENGINE 200API was restructured so that this change was reversed, and behaviour of the 201other functions resembled more closely the previous behaviour. The 202behaviour of defaults in the ENGINE API now transparently overrides the 203behaviour of defaults in the RSA API without requiring changing these 204function prototypes. 205 206=cut 207