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| 1 | =pod | ||
| 2 | |||
| 3 | =head1 NAME | ||
| 4 | |||
| 5 | RSA_set_default_method, RSA_get_default_method, RSA_set_method, | ||
| 6 | RSA_get_method, RSA_PKCS1_SSLeay, RSA_null_method, RSA_flags, | ||
| 7 | RSA_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 | |||
| 31 | An B<RSA_METHOD> specifies the functions that OpenSSL uses for RSA | ||
| 32 | operations. By modifying the method, alternative implementations such as | ||
| 33 | hardware accelerators may be used. IMPORTANT: See the NOTES section for | ||
| 34 | important information about how these RSA API functions are affected by the | ||
| 35 | use of B<ENGINE> API calls. | ||
| 36 | |||
| 37 | Initially, the default RSA_METHOD is the OpenSSL internal implementation, | ||
| 38 | as returned by RSA_PKCS1_SSLeay(). | ||
| 39 | |||
| 40 | RSA_set_default_method() makes B<meth> the default method for all RSA | ||
| 41 | structures created later. B<NB>: This is true only whilst no ENGINE has | ||
| 42 | been set as a default for RSA, so this function is no longer recommended. | ||
| 43 | |||
| 44 | RSA_get_default_method() returns a pointer to the current default | ||
| 45 | RSA_METHOD. However, the meaningfulness of this result is dependent on | ||
| 46 | whether the ENGINE API is being used, so this function is no longer | ||
| 47 | recommended. | ||
| 48 | |||
| 49 | RSA_set_method() selects B<meth> to perform all operations using the key | ||
| 50 | B<rsa>. This will replace the RSA_METHOD used by the RSA key and if the | ||
| 51 | previous method was supplied by an ENGINE, the handle to that ENGINE will | ||
| 52 | be released during the change. It is possible to have RSA keys that only | ||
| 53 | work with certain RSA_METHOD implementations (eg. from an ENGINE module | ||
| 54 | that supports embedded hardware-protected keys), and in such cases | ||
| 55 | attempting to change the RSA_METHOD for the key can have unexpected | ||
| 56 | results. | ||
| 57 | |||
| 58 | RSA_get_method() returns a pointer to the RSA_METHOD being used by B<rsa>. | ||
| 59 | This method may or may not be supplied by an ENGINE implementation, but if | ||
| 60 | it is, the return value can only be guaranteed to be valid as long as the | ||
| 61 | RSA key itself is valid and does not have its implementation changed by | ||
| 62 | RSA_set_method(). | ||
| 63 | |||
| 64 | RSA_flags() returns the B<flags> that are set for B<rsa>'s current | ||
| 65 | RSA_METHOD. See the BUGS section. | ||
| 66 | |||
| 67 | RSA_new_method() allocates and initializes an RSA structure so that | ||
| 68 | B<engine> will be used for the RSA operations. If B<engine> is NULL, the | ||
| 69 | default ENGINE for RSA operations is used, and if no default ENGINE is set, | ||
| 70 | the RSA_METHOD controlled by RSA_set_default_method() is used. | ||
| 71 | |||
| 72 | RSA_flags() returns the B<flags> that are set for B<rsa>'s current method. | ||
| 73 | |||
| 74 | RSA_new_method() allocates and initializes an B<RSA> structure so that | ||
| 75 | B<method> will be used for the RSA operations. If B<method> is B<NULL>, | ||
| 76 | the 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, unsigned char *m, unsigned int m_len, | ||
| 129 | unsigned char *sigret, unsigned int *siglen, RSA *rsa); | ||
| 130 | |||
| 131 | /* verify. For backward compatibility, this is used only | ||
| 132 | * if (flags & RSA_FLAG_SIGN_VER) | ||
| 133 | */ | ||
| 134 | int (*rsa_verify)(int type, unsigned char *m, unsigned int m_len, | ||
| 135 | unsigned char *sigbuf, unsigned int siglen, RSA *rsa); | ||
| 136 | |||
| 137 | } RSA_METHOD; | ||
| 138 | |||
| 139 | =head1 RETURN VALUES | ||
| 140 | |||
| 141 | RSA_PKCS1_SSLeay(), RSA_PKCS1_null_method(), RSA_get_default_method() | ||
| 142 | and RSA_get_method() return pointers to the respective RSA_METHODs. | ||
| 143 | |||
| 144 | RSA_set_default_method() returns no value. | ||
| 145 | |||
| 146 | RSA_set_method() returns a pointer to the old RSA_METHOD implementation | ||
| 147 | that was replaced. However, this return value should probably be ignored | ||
| 148 | because if it was supplied by an ENGINE, the pointer could be invalidated | ||
| 149 | at any time if the ENGINE is unloaded (in fact it could be unloaded as a | ||
| 150 | result of the RSA_set_method() function releasing its handle to the | ||
| 151 | ENGINE). For this reason, the return type may be replaced with a B<void> | ||
| 152 | declaration in a future release. | ||
| 153 | |||
| 154 | RSA_new_method() returns NULL and sets an error code that can be obtained | ||
| 155 | by L<ERR_get_error(3)|ERR_get_error(3)> if the allocation fails. Otherwise | ||
| 156 | it returns a pointer to the newly allocated structure. | ||
| 157 | |||
| 158 | =head1 NOTES | ||
| 159 | |||
| 160 | As of version 0.9.7, RSA_METHOD implementations are grouped together with | ||
| 161 | other algorithmic APIs (eg. DSA_METHOD, EVP_CIPHER, etc) into B<ENGINE> | ||
| 162 | modules. If a default ENGINE is specified for RSA functionality using an | ||
| 163 | ENGINE API function, that will override any RSA defaults set using the RSA | ||
| 164 | API (ie. RSA_set_default_method()). For this reason, the ENGINE API is the | ||
| 165 | recommended way to control default implementations for use in RSA and other | ||
| 166 | cryptographic algorithms. | ||
| 167 | |||
| 168 | =head1 BUGS | ||
| 169 | |||
| 170 | The behaviour of RSA_flags() is a mis-feature that is left as-is for now | ||
| 171 | to avoid creating compatibility problems. RSA functionality, such as the | ||
| 172 | encryption functions, are controlled by the B<flags> value in the RSA key | ||
| 173 | itself, not by the B<flags> value in the RSA_METHOD attached to the RSA key | ||
| 174 | (which is what this function returns). If the flags element of an RSA key | ||
| 175 | is changed, the changes will be honoured by RSA functionality but will not | ||
| 176 | be reflected in the return value of the RSA_flags() function - in effect | ||
| 177 | RSA_flags() behaves more like an RSA_default_flags() function (which does | ||
| 178 | not currently exist). | ||
| 179 | |||
| 180 | =head1 SEE ALSO | ||
| 181 | |||
| 182 | L<rsa(3)|rsa(3)>, L<RSA_new(3)|RSA_new(3)> | ||
| 183 | |||
| 184 | =head1 HISTORY | ||
| 185 | |||
| 186 | RSA_new_method() and RSA_set_default_method() appeared in SSLeay 0.8. | ||
| 187 | RSA_get_default_method(), RSA_set_method() and RSA_get_method() as | ||
| 188 | well as the rsa_sign and rsa_verify components of RSA_METHOD were | ||
| 189 | added in OpenSSL 0.9.4. | ||
| 190 | |||
| 191 | RSA_set_default_openssl_method() and RSA_get_default_openssl_method() | ||
| 192 | replaced RSA_set_default_method() and RSA_get_default_method() | ||
| 193 | respectively, and RSA_set_method() and RSA_new_method() were altered to use | ||
| 194 | B<ENGINE>s rather than B<RSA_METHOD>s during development of the engine | ||
| 195 | version of OpenSSL 0.9.6. For 0.9.7, the handling of defaults in the ENGINE | ||
| 196 | API was restructured so that this change was reversed, and behaviour of the | ||
| 197 | other functions resembled more closely the previous behaviour. The | ||
| 198 | behaviour of defaults in the ENGINE API now transparently overrides the | ||
| 199 | behaviour of defaults in the RSA API without requiring changing these | ||
| 200 | function prototypes. | ||
| 201 | |||
| 202 | =cut | ||
