xref: /openbsd-src/lib/libcrypto/man/RSA_set_method.3 (revision b7274ba6d22991e910900ca5e330d872dcc276c8)

.\"	$OpenBSD: RSA_set_method.3,v 1.18 2023/11/19 10:34:26 tb Exp $
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.Dd $Mdocdate: November 19 2023 $
.Dt RSA_SET_METHOD 3
.Os
.Sh NAME
.Nm RSA_set_default_method ,
.Nm RSA_get_default_method ,
.Nm RSA_set_method ,
.Nm RSA_get_method ,
.Nm RSA_PKCS1_SSLeay ,
.Nm RSA_flags ,
.Nm RSA_new_method
.Nd select RSA method
.Sh SYNOPSIS
.In openssl/rsa.h
.Ft void
.Fo RSA_set_default_method
.Fa "const RSA_METHOD *meth"
.Fc
.Ft const RSA_METHOD *
.Fn RSA_get_default_method void
.Ft int
.Fo RSA_set_method
.Fa "RSA *rsa"
.Fa "const RSA_METHOD *meth"
.Fc
.Ft const RSA_METHOD *
.Fo RSA_get_method
.Fa "const RSA *rsa"
.Fc
.Ft const RSA_METHOD *
.Fn RSA_PKCS1_SSLeay void
.Ft int
.Fo RSA_flags
.Fa "const RSA *rsa"
.Fc
.Ft RSA *
.Fo RSA_new_method
.Fa "ENGINE *engine"
.Fc
.Sh DESCRIPTION
An
.Vt RSA_METHOD
object contains pointers to the functions used for RSA operations.
By default, the internal implementation returned by
.Fn RSA_PKCS1_SSLeay
is used.
By selecting another method, alternative implementations
such as hardware accelerators may be used.
.Pp
.Fn RSA_set_default_method
selects
.Fa meth
as the default method for all
.Vt RSA
structures created later.
.Pp
.Fn RSA_get_default_method
returns a pointer to the current default method.
.Pp
.Fn RSA_set_method
selects
.Fa meth
to perform all operations using the key
.Fa rsa .
This replaces the previous
.Vt RSA_METHOD
used by the RSA key, calling the
.Fa finish
function set up with
.Xr RSA_meth_set_finish 3
if any.
If
.Fa meth
contains an
.Fa init
function set up with
.Xr RSA_meth_set_init 3 ,
that function is called just before returning from
.Fn RSA_set_method .
.Pp
It is possible to have RSA keys that only work with certain
.Vt RSA_METHOD
implementations,
and in such cases attempting to change the
.Vt RSA_METHOD
for the key can have unexpected results.
.Pp
.Fn RSA_get_method
returns a pointer to the
.Vt RSA_METHOD
being used by
.Fa rsa .
.Pp
The misleadingly named function
.Fn RSA_flags
returns the flags that are set for the current
.Vt RSA_METHOD
of
.Fa rsa .
The flags used by
.Fa rsa
itself can instead be tested with
.Xr RSA_test_flags 3 .
See the
.Sx BUGS
section for more details.
.Pp
.Fn RSA_new_method
allocates and initializes an
.Vt RSA
structure.
The
.Fa engine
argument is ignored and
the default method controlled by
.Fn RSA_set_default_method
is used.
.Pp
The initial
.Fa flags
are copied from the
.Vt RSA_METHOD
object used and will not be affected by later changes to that object,
but may be modified by the optional
.Fa init
function which may have been set up with
.Xr RSA_meth_set_init 3
and which is called just before returning from
.Fn RSA_new_method .
.Sh RETURN VALUES
.Fn RSA_PKCS1_SSLeay ,
.Fn RSA_get_default_method ,
and
.Fn RSA_get_method
return pointers to the respective
.Vt RSA_METHOD .
.Pp
.Fn RSA_set_method
returns 1 on success or 0 on failure.
Currently, it cannot fail.
.Pp
.Fn RSA_new_method
returns
.Dv NULL
and sets an error code that can be obtained by
.Xr ERR_get_error 3
if the allocation fails.
Otherwise it returns a pointer to the newly allocated structure.
.Sh SEE ALSO
.Xr RSA_meth_new 3 ,
.Xr RSA_new 3
.Sh HISTORY
.Fn RSA_set_default_method ,
.Fn RSA_PKCS1_SSLeay ,
and
.Fn RSA_new_method
first appeared in SSLeay 0.8.0.
.Fn RSA_flags
first appeared in SSLeay 0.9.0.
These functions have been available since
.Ox 2.4 .
.Pp
.Fn RSA_get_default_method ,
.Fn RSA_set_method ,
and
.Fn RSA_get_method
as well as the
.Fa rsa_sign
and
.Fa rsa_verify
components of
.Vt RSA_METHOD
first appeared in OpenSSL 0.9.4 and have been available since
.Ox 2.6 .
.Sh BUGS
The behaviour of
.Fn RSA_flags
is a misfeature that is left as-is for now to avoid creating
compatibility problems.
RSA functionality, such as the encryption functions, are controlled by
the
.Fa flags
value in the
.Vt RSA
key itself, not by the
.Fa flags
value in the
.Vt RSA_METHOD
attached to the RSA key (which is what this function returns).
If the flags element of an
.Vt RSA
key is changed, the changes will be honoured by RSA functionality
but will not be reflected in the return value of the
.Fn RSA_flags
function - in effect
.Fn RSA_flags
behaves more like an
.Fn RSA_default_flags
function, which does not
currently exist.