1TLS_CONFIG_SET_PROTOC... BSD Library Functions Manual TLS_CONFIG_SET_PROTOC...
2
4 tls_config_set_protocols, tls_config_parse_protocols,
5 tls_config_set_alpn, tls_config_set_ciphers, tls_config_set_dheparams,
6 tls_config_set_ecdhecurves, tls_config_prefer_ciphers_client,
7 tls_config_prefer_ciphers_server — TLS protocol and cipher selection
8
10 #include <tls.h>
11 int
13 tls_config_set_protocols(struct tls_config *config, uint32_t protocols);
14 int
16 tls_config_parse_protocols(uint32_t *protocols, const char *protostr);
17 int
19 tls_config_set_alpn(struct tls_config *config, const char *alpn);
20 int
22 tls_config_set_ciphers(struct tls_config *config, const char *ciphers);
23 int
25 tls_config_set_dheparams(struct tls_config *config, const char *params);
26 int
28 tls_config_set_ecdhecurves(struct tls_config *config,
29 const char *curves);
30 void
32 tls_config_prefer_ciphers_client(struct tls_config *config);
33 void
35 tls_config_prefer_ciphers_server(struct tls_config *config);
36
38 These functions modify a configuration by setting parameters. The con‐
39 figuration options apply to both clients and servers, unless noted other‐
40 wise.
41 tls_config_set_protocols() specifies which versions of the TLS protocol
43 may be used. Possible values are the bitwise OR of:
44 TLS_PROTOCOL_TLSv1_0
46 TLS_PROTOCOL_TLSv1_1
47 TLS_PROTOCOL_TLSv1_2
48 TLS_PROTOCOL_TLSv1_3
49 Additionally, the values TLS_PROTOCOL_TLSv1 (TLSv1.0, TLSv1.1, TLSv1.2,
51 TLSv1.3), TLS_PROTOCOLS_ALL (all supported protocols) and
52 TLS_PROTOCOLS_DEFAULT (TLSv1.2 and TLSv1.3) may be used.
53 The tls_config_parse_protocols() utility function parses a protocol
55 string and returns the corresponding value via the protocols argument.
56 This value can then be passed to the tls_config_set_protocols() function.
57 The protocol string is a comma or colon separated list of keywords.
58 Valid keywords are tlsv1.0, tlsv1.1, tlsv1.2, tlsv1.3, all (all supported
59 protocols), default (an alias for secure), legacy (an alias for all) and
60 secure (currently TLSv1.2 and TLSv1.3). If a value has a negative prefix
61 (in the form of a leading exclamation mark) then it is removed from the
62 list of available protocols, rather than being added to it.
63 tls_config_set_alpn() sets the ALPN protocols that are supported. The
65 alpn string is a comma separated list of protocols, in order of prefer‐
66 ence.
67 tls_config_set_ciphers() sets the list of ciphers that may be used.
69 Lists of ciphers are specified by name, and the permitted names are:
70 secure (or alias default)
72 compat
73 legacy
74 insecure (or alias all)
75 Alternatively, libssl cipher strings can be specified. See the CIPHERS
77 section of openssl(1) for further information.
78 tls_config_set_dheparams() specifies the parameters that will be used
80 during Diffie-Hellman Ephemeral (DHE) key exchange. Possible values are
81 "none", "auto" and "legacy". In "auto" mode, the key size for the
82 ephemeral key is automatically selected based on the size of the private
83 key being used for signing. In "legacy" mode, 1024 bit ephemeral keys
84 are used. The default value is "none", which disables DHE key exchange.
85 tls_config_set_ecdhecurves() specifies the names of the elliptic curves
87 that may be used during Elliptic Curve Diffie-Hellman Ephemeral (ECDHE)
88 key exchange. This is a comma separated list, given in order of prefer‐
89 ence. The special value of "default" will use the default curves (cur‐
90 rently X25519, P-256 and P-384). This function replaces
91 tls_config_set_ecdhecurve(), which is deprecated.
92 tls_config_prefer_ciphers_client() prefers ciphers in the client's cipher
94 list when selecting a cipher suite (server only). This is considered to
95 be less secure than preferring the server's list.
96 tls_config_prefer_ciphers_server() prefers ciphers in the server's cipher
98 list when selecting a cipher suite (server only). This is considered to
99 be more secure than preferring the client's list and is the default.
100
102 These functions return 0 on success or -1 on error.
103
105 tls_config_ocsp_require_stapling(3), tls_config_set_session_id(3),
106 tls_config_verify(3), tls_init(3), tls_load_file(3)
107
109 tls_config_set_ciphers() appeared in OpenBSD 5.6 and got its final name
110 in OpenBSD 5.7.
111 tls_config_set_protocols(), tls_config_parse_protocols(),
113 tls_config_set_dheparams(), and tls_config_set_ecdhecurve() appeared in
114 OpenBSD 5.7, tls_config_prefer_ciphers_client() and
115 tls_config_prefer_ciphers_server() in OpenBSD 5.9, and
116 tls_config_set_alpn() in OpenBSD 6.1.
117
119 Joel Sing <jsing@openbsd.org> with contributions from
120 Ted Unangst <tedu@openbsd.org> (tls_config_set_ciphers()) and
121 Reyk Floeter <reyk@openbsd.org> (tls_config_set_ecdhecurve())
122BSD January 22, 2020 BSD