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- =pod
- =head1 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
- =head1 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);
- =head1 DESCRIPTION
- SSL_CTX_set1_curves() sets the supported curves for B<ctx> to B<clistlen>
- curves in the array B<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 B<ctx> to
- string B<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 B<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 B<curves> parameter can be B<NULL> to simply
- return the number of curves for memory allocation purposes. The
- B<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 B<n> for a server-side
- SSL B<ssl>. If B<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 B<n> is normally set to zero. If the value B<n> is out of range,
- NID_undef is returned.
- SSL_CTX_set_ecdh_auto() and SSL_set_ecdh_auto() set automatic curve
- selection for server B<ctx> or B<ssl> to B<onoff>. If B<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.
- =head1 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.
- =head1 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 B<n> or NID_undef if there
- is no shared curve B<n>; or the total number of shared curves if B<n>
- is -1.
- When called on a client B<ssl>, SSL_get_shared_curve() has no meaning and
- returns -1.
- =head1 SEE ALSO
- L<SSL_CTX_add_extra_chain_cert(3)|SSL_CTX_add_extra_chain_cert(3)>
- =head1 HISTORY
- These functions were first added to OpenSSL 1.0.2.
- =cut
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