/usr/man/cat.3/SSL_get1_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(3)
See also SSL_CTX_set1_curves_list(3)
See also SSL_CTX_set_ecdh_auto(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)