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SSL_CTX_set1_curves(3)              OpenSSL             SSL_CTX_set1_curves(3)



NAME
       SSL_CTX_set1_groups, SSL_CTX_set1_groups_list, SSL_set1_groups,
       SSL_set1_groups_list, SSL_get1_groups, SSL_get_shared_group,
       SSL_get_negotiated_group, SSL_CTX_set1_curves,
       SSL_CTX_set1_curves_list, SSL_set1_curves, SSL_set1_curves_list,
       SSL_get1_curves, SSL_get_shared_curve - EC supported curve functions

LIBRARY
       libcrypto, -lcrypto

SYNOPSIS
        #include <openssl/ssl.h>

        int SSL_CTX_set1_groups(SSL_CTX *ctx, int *glist, int glistlen);
        int SSL_CTX_set1_groups_list(SSL_CTX *ctx, char *list);

        int SSL_set1_groups(SSL *ssl, int *glist, int glistlen);
        int SSL_set1_groups_list(SSL *ssl, char *list);

        int SSL_get1_groups(SSL *ssl, int *groups);
        int SSL_get_shared_group(SSL *s, int n);
        int SSL_get_negotiated_group(SSL *s);

        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);

DESCRIPTION
       For all of the functions below that set the supported groups there must
       be at least one group in the list. A number of these functions identify
       groups via a unique integer NID value. However, support for some groups
       may be added by external providers. In this case there will be no NID
       assigned for the group.  When setting such groups applications should
       use the "list" form of these functions (i.e. SSL_CTX_set1_groups_list()
       and SSL_set1_groups_list).

       SSL_CTX_set1_groups() sets the supported groups for ctx to glistlen
       groups in the array glist. The array consist of all NIDs of groups in
       preference order. For a TLS client the groups are used directly in the
       supported groups extension. For a TLS server the groups are used to
       determine the set of shared groups. Currently supported groups for
       TLSv1.3 are NID_X9_62_prime256v1, NID_secp384r1, NID_secp521r1,
       NID_X25519, NID_X448, NID_ffdhe2048, NID_ffdhe3072, NID_ffdhe4096,
       NID_ffdhe6144 and NID_ffdhe8192.

       SSL_CTX_set1_groups_list() sets the supported groups for ctx to string
       list. The string is a colon separated list of group NIDs or names, for
       example "P-521:P-384:P-256:X25519:ffdhe2048". Currently supported
       groups for TLSv1.3 are P-256, P-384, P-521, X25519, X448, ffdhe2048,
       ffdhe3072, ffdhe4096, ffdhe6144, ffdhe8192. Support for other groups
       may be added by external providers.

       SSL_set1_groups() and SSL_set1_groups_list() are similar except they
       set supported groups for the SSL structure ssl.

       SSL_get1_groups() returns the set of supported groups sent by a client
       in the supported groups extension. It returns the total number of
       supported groups. The groups parameter can be NULL to simply return the
       number of groups for memory allocation purposes. The groups array is in
       the form of a set of group NIDs in preference order. It can return zero
       if the client did not send a supported groups extension. If a supported
       group NID is unknown then the value is set to the bitwise OR of
       TLSEXT_nid_unknown (0x1000000) and the id of the group.

       SSL_get_shared_group() returns the NID of the shared group n for a
       server-side SSL ssl. If n is -1 then the total number of shared groups
       is returned, which may be zero. Other than for diagnostic purposes,
       most applications will only be interested in the first shared group so
       n is normally set to zero. If the value n is out of range, NID_undef is
       returned. If the NID for the shared group is unknown then the value is
       set to the bitwise OR of TLSEXT_nid_unknown (0x1000000) and the id of
       the group.

       SSL_get_negotiated_group() returns the NID of the negotiated group used
       for the handshake key exchange process.  For TLSv1.3 connections this
       typically reflects the state of the current connection, though in the
       case of PSK-only resumption, the returned value will be from a previous
       connection.  For earlier TLS versions, when a session has been resumed,
       it always reflects the group used for key exchange during the initial
       handshake (otherwise it is from the current, non-resumption,
       connection).  This can be called by either client or server. If the NID
       for the shared group is unknown then the value is set to the bitwise OR
       of TLSEXT_nid_unknown (0x1000000) and the id of the group.

       All these functions are implemented as macros.

       The curve functions are synonyms for the equivalently named group
       functions and are identical in every respect. They exist because, prior
       to TLS1.3, there was only the concept of supported curves. In TLS1.3
       this was renamed to supported groups, and extended to include Diffie
       Hellman groups. The group functions should be used in preference.

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.

RETURN VALUES
       SSL_CTX_set1_groups(), SSL_CTX_set1_groups_list(), SSL_set1_groups()
       and SSL_set1_groups_list(), return 1 for success and 0 for failure.

       SSL_get1_groups() returns the number of groups, which may be zero.

       SSL_get_shared_group() returns the NID of shared group n or NID_undef
       if there is no shared group n; or the total number of shared groups if
       n is -1.

       When called on a client ssl, SSL_get_shared_group() has no meaning and
       returns -1.

       SSL_get_negotiated_group() returns the NID of the negotiated group used
       for key exchange, or NID_undef if there was no negotiated group.

SEE ALSO
       ssl(7), SSL_CTX_add_extra_chain_cert(3)

HISTORY
       The curve functions were added in OpenSSL 1.0.2. The equivalent group
       functions were added in OpenSSL 1.1.1. The SSL_get_negotiated_group()
       function was added in OpenSSL 3.0.0.

COPYRIGHT
       Copyright 2013-2021 The OpenSSL Project Authors. All Rights Reserved.

       Licensed under the Apache License 2.0 (the "License").  You may not use
       this file except in compliance with the License.  You can obtain a copy
       in the file LICENSE in the source distribution or at
       <https://www.openssl.org/source/license.html>.



3.0.12                            2023-05-07            SSL_CTX_set1_curves(3)