/usr/man/cat.3/SSL_CTX_set1_curves.3
SSL_CTX_set1_curves(3) OpenSSL SSL_CTX_set1_curves(3)
NAME
SSL_CTX_set1_curves, SSL_CTX_set1_curves_list,
SSL_set1_curves, SSL_set1_curves_list, SSL_get1_curves,
SSL_get_shared_curve, SSL_CTX_set_ecdh_auto,
SSL_set_ecdh_auto - EC supported curve functions
SYNOPSIS
#include <openssl/ssl.h>
int SSL_CTX_set1_curves(SSL_CTX *ctx, int *clist, int clistlen);
int SSL_CTX_set1_curves_list(SSL_CTX *ctx, char *list);
int SSL_set1_curves(SSL *ssl, int *clist, int clistlen);
int SSL_set1_curves_list(SSL *ssl, char *list);
int SSL_get1_curves(SSL *ssl, int *curves);
int SSL_get_shared_curve(SSL *s, int n);
int SSL_CTX_set_ecdh_auto(SSL_CTX *ctx, int onoff);
int SSL_set_ecdh_auto(SSL *s, int onoff);
DESCRIPTION
SSL_CTX_set1_curves() sets the supported curves for ctx to
clistlen curves in the array clist. The array consist of all
NIDs of curves in preference order. For a TLS client the
curves are used directly in the supported curves extension.
For a TLS server the curves are used to determine the set of
shared curves.
SSL_CTX_set1_curves_list() sets the supported curves for ctx
to string list. The string is a colon separated list of
curve NIDs or names, for example "P-521:P-384:P-256".
SSL_set1_curves() and SSL_set1_curves_list() are similar
except they set supported curves for the SSL structure ssl.
SSL_get1_curves() returns the set of supported curves sent
by a client in the supported curves extension. It returns
the total number of supported curves. The curves parameter
can be NULL to simply return the number of curves for memory
allocation purposes. The curves array is in the form of a
set of curve NIDs in preference order. It can return zero if
the client did not send a supported curves extension.
SSL_get_shared_curve() returns shared curve n for a server-
side SSL ssl. If n is -1 then the total number of shared
curves is returned, which may be zero. Other than for
diagnostic purposes, most applications will only be
interested in the first shared curve so n is normally set to
zero. If the value n is out of range, NID_undef is returned.
1.0.2t Last change: 2019-09-10 1
SSL_CTX_set1_curves(3) OpenSSL SSL_CTX_set1_curves(3)
SSL_CTX_set_ecdh_auto() and SSL_set_ecdh_auto() set
automatic curve selection for server ctx or ssl to onoff. If
onoff is 1 then the highest preference curve is
automatically used for ECDH temporary keys used during key
exchange.
All these functions are implemented as macros.
NOTES
If an application wishes to make use of several of these
functions for configuration purposes either on a command
line or in a file it should consider using the SSL_CONF
interface instead of manually parsing options.
The functions SSL_CTX_set_ecdh_auto() and
SSL_set_ecdh_auto() can be used to make a server always
choose the most appropriate curve for a client. If set it
will override any temporary ECDH parameters set by a server.
Previous versions of OpenSSL could effectively only use a
single ECDH curve set using a function such as
SSL_CTX_set_ecdh_tmp(). Newer applications should just call:
SSL_CTX_set_ecdh_auto(ctx, 1);
and they will automatically support ECDH using the most
appropriate shared curve.
RETURN VALUES
SSL_CTX_set1_curves(), SSL_CTX_set1_curves_list(),
SSL_set1_curves(), SSL_set1_curves_list(),
SSL_CTX_set_ecdh_auto() and SSL_set_ecdh_auto() return 1 for
success and 0 for failure.
SSL_get1_curves() returns the number of curves, which may be
zero.
SSL_get_shared_curve() returns the NID of shared curve n or
NID_undef if there is no shared curve n; or the total number
of shared curves if n is -1.
When called on a client ssl, SSL_get_shared_curve() has no
meaning and returns -1.
SEE ALSO
SSL_CTX_add_extra_chain_cert(3)
HISTORY
These functions were first added to OpenSSL 1.0.2.
1.0.2t Last change: 2019-09-10 2
See also SSL_CTX_set1_curves_list(3)
See also SSL_CTX_set_ecdh_auto(3)
See also SSL_get1_curves(3)
See also SSL_get_shared_curve(3)
See also SSL_set1_curves(3)
See also SSL_set1_curves_list(3)
See also SSL_set_ecdh_auto(3)
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