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$NetBSD: RSA_set_method.3,v 1.1.1.2 2023/04/18 14:19:14 christos Exp $

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Title "RSA_set_method 3" For nroff, turn off justification. Always turn off hyphenation; it makes
way too many mistakes in technical documents.
.nh RSA_set_default_method, RSA_get_default_method, RSA_set_method, RSA_get_method, RSA_PKCS1_OpenSSL, RSA_flags, RSA_new_method - select RSA method libcrypto, -lcrypto 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_OpenSSL(void); \& int RSA_flags(const RSA *rsa); \& RSA *RSA_new_method(ENGINE *engine); .Ve Header "DESCRIPTION" An \s-1RSA_METHOD\s0 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 \s-1ENGINE\s0 \s-1API\s0 calls.

Initially, the default \s-1RSA_METHOD\s0 is the OpenSSL internal implementation, as returned by RSA_PKCS1_OpenSSL().

\fBRSA_set_default_method() makes meth the default method for all \s-1RSA\s0 structures created later. \fB\s-1NB\s0: 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. This function is not thread-safe and should not be called at the same time as other OpenSSL functions.

\fBRSA_get_default_method() 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.

\fBRSA_set_method() selects meth to perform all operations using the key \fBrsa. 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 (e.g. 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.

\fBRSA_get_method() returns a pointer to the \s-1RSA_METHOD\s0 being used by rsa. 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().

\fBRSA_flags() returns the flags that are set for rsa's current \s-1RSA_METHOD.\s0 See the \s-1BUGS\s0 section.

\fBRSA_new_method() allocates and initializes an \s-1RSA\s0 structure so that \fBengine will be used for the \s-1RSA\s0 operations. If engine 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 RSA_set_default_method() is used.

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

\fBRSA_new_method() allocates and initializes an \s-1RSA\s0 structure so that \fBmethod will be used for the \s-1RSA\s0 operations. If method is \s-1NULL\s0, the default method is used.

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_METHOD_FLAG_NO_CHECK - don\*(Aqt check pub/private match */ int flags; \& char *app_data; /* ?? */ \& int (*rsa_sign)(int type, const unsigned char *m, unsigned int m_length, unsigned char *sigret, unsigned int *siglen, const RSA *rsa); 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 Header "RETURN VALUES" \fBRSA_PKCS1_OpenSSL(), RSA_PKCS1_null_method(), RSA_get_default_method() and RSA_get_method() return pointers to the respective RSA_METHODs.

\fBRSA_set_default_method() returns no value.

\fBRSA_set_method() 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 RSA_set_method() function releasing its handle to the \s-1ENGINE\s0). For this reason, the return type may be replaced with a void declaration in a future release.

\fBRSA_new_method() returns \s-1NULL\s0 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.

Header "BUGS" The behaviour of RSA_flags() 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 flags value in the \s-1RSA\s0 key itself, not by the flags 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 RSA_flags() function - in effect \fBRSA_flags() behaves more like an RSA_default_flags() function (which does not currently exist). Header "SEE ALSO" \fBRSA_new\|(3) Header "HISTORY" The RSA_null_method(), which was a partial attempt to avoid patent issues, was replaced to always return \s-1NULL\s0 in OpenSSL 1.1.1. Header "COPYRIGHT" Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.

Licensed under the OpenSSL license (the \*(L"License\*(R"). You may not use this file except in compliance with the License. You can obtain a copy in the file \s-1LICENSE\s0 in the source distribution or at <https://www.openssl.org/source/license.html>.

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