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TLS_CONFIG_SET_PRO... DragonFly Library Functions Manual TLS_CONFIG_SET_PRO...


NAME

     tls_config_set_protocols, tls_config_parse_protocols,
     tls_config_set_alpn, tls_config_set_ciphers, tls_config_set_dheparams,
     tls_config_set_ecdhecurves, tls_config_prefer_ciphers_client,
     tls_config_prefer_ciphers_server -- TLS protocol and cipher selection


SYNOPSIS

     #include <tls.h>

     int
     tls_config_set_protocols(struct tls_config *config, uint32_t protocols);

     int
     tls_config_parse_protocols(uint32_t *protocols, const char *protostr);

     int
     tls_config_set_alpn(struct tls_config *config, const char *alpn);

     int
     tls_config_set_ciphers(struct tls_config *config, const char *ciphers);

     int
     tls_config_set_dheparams(struct tls_config *config, const char *params);

     int
     tls_config_set_ecdhecurves(struct tls_config *config,
	 const char *curves);

     void
     tls_config_prefer_ciphers_client(struct tls_config *config);

     void
     tls_config_prefer_ciphers_server(struct tls_config *config);


DESCRIPTION

     These functions modify a configuration by setting parameters.  The con-
     figuration options apply to both clients and servers, unless noted other-
     wise.

     tls_config_set_protocols() specifies which versions of the TLS protocol
     may be used.  Possible values are the bitwise OR of:

	   TLS_PROTOCOL_TLSv1_0
	   TLS_PROTOCOL_TLSv1_1
	   TLS_PROTOCOL_TLSv1_2

     Additionally, the values TLS_PROTOCOL_TLSv1 (TLSv1.0, TLSv1.1 and
     TLSv1.2), TLS_PROTOCOLS_ALL (all supported protocols) and
     TLS_PROTOCOLS_DEFAULT (TLSv1.2 only) may be used.

     The tls_config_parse_protocols() utility function parses a protocol
     string and returns the corresponding value via the protocols argument.
     This value can then be passed to the tls_config_set_protocols() function.
     The protocol string is a comma or colon separated list of keywords.
     Valid keywords are tlsv1.0, tlsv1.1, tlsv1.2, all (all supported proto-
     cols), default (an alias for secure), legacy (an alias for all) and
     secure (currently TLSv1.2 only).  If a value has a negative prefix (in
     the form of a leading exclamation mark) then it is removed from the list
     of available protocols, rather than being added to it.

     tls_config_set_alpn() sets the ALPN protocols that are supported.	The
     alpn string is a comma separated list of protocols, in order of prefer-
     ence.

     tls_config_set_ciphers() sets the list of ciphers that may be used.
     Lists of ciphers are specified by name, and the permitted names are:

	   secure (or alias default)
	   compat
	   legacy
	   insecure (or alias all)

     Alternatively, libssl cipher strings can be specified.  See the CIPHERS
     section of openssl(1) for further information.

     tls_config_set_dheparams() specifies the parameters that will be used
     during Diffie-Hellman Ephemeral (DHE) key exchange.  Possible values are
     "none", "auto" and "legacy".  In "auto" mode, the key size for the
     ephemeral key is automatically selected based on the size of the private
     key being used for signing.  In "legacy" mode, 1024 bit ephemeral keys
     are used.	The default value is "none", which disables DHE key exchange.

     tls_config_set_ecdhecurves() specifies the names of the elliptic curves
     that may be used during Elliptic Curve Diffie-Hellman Ephemeral (ECDHE)
     key exchange.  This is a comma separated list, given in order of prefer-
     ence.  The special value of "default" will use the default curves (cur-
     rently X25519, P-256 and P-384).  This function replaces
     tls_config_set_ecdhecurve(), which is deprecated.

     tls_config_prefer_ciphers_client() prefers ciphers in the client's cipher
     list when selecting a cipher suite (server only).	This is considered to
     be less secure than preferring the server's list.

     tls_config_prefer_ciphers_server() prefers ciphers in the server's cipher
     list when selecting a cipher suite (server only).	This is considered to
     be more secure than preferring the client's list and is the default.


RETURN VALUES

     These functions return 0 on success or -1 on error.


SEE ALSO

     tls_config_ocsp_require_stapling(3), tls_config_set_session_id(3),
     tls_config_verify(3), tls_init(3), tls_load_file(3)


HISTORY

     tls_config_set_ciphers() appeared in OpenBSD 5.6 and got its final name
     in OpenBSD 5.7.

     tls_config_set_protocols(), tls_config_parse_protocols(),
     tls_config_set_dheparams(), and tls_config_set_ecdhecurve() appeared in
     OpenBSD 5.7, tls_config_prefer_ciphers_client() and
     tls_config_prefer_ciphers_server() in OpenBSD 5.9, and
     tls_config_set_alpn() in OpenBSD 6.1.


AUTHORS

     Joel Sing <jsing@openbsd.org> with contributions from
     Ted Unangst <tedu@openbsd.org> (tls_config_set_ciphers()) and
     Reyk Floeter <reyk@openbsd.org> (tls_config_set_ecdhecurve())

DragonFly 5.5			August 12, 2017 		 DragonFly 5.5

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