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:
59 tlsv1.0
61 tlsv1.1
62 tlsv1.2
63 tlsv1.3
64 all (all supported protocols)
65 default (an alias for secure)
66 legacy (an alias for all)
67 secure (currently TLSv1.2 and TLSv1.3)
68 If a value has a negative prefix (in the form of a leading exclamation
70 mark) then it is removed from the list of available protocols, rather
71 than being added to it.
72 tls_config_set_alpn() sets the ALPN protocols that are supported. The
74 alpn string is a comma separated list of protocols, in order of prefer‐
75 ence.
76 tls_config_set_ciphers() sets the list of ciphers that may be used.
78 Lists of ciphers are specified by name, and the permitted names are:
79 secure (or alias default)
81 compat
82 legacy
83 insecure (or alias all)
84 Alternatively, libssl cipher strings can be specified. See the CIPHERS
86 section of openssl(1) for further information.
87 tls_config_set_dheparams() specifies the parameters that will be used
89 during Diffie-Hellman Ephemeral (DHE) key exchange. Possible values are:
90 none
92 auto
93 legacy
94 In auto mode, the key size for the ephemeral key is automatically se‐
96 lected based on the size of the private key being used for signing. In
97 legacy mode, 1024 bit ephemeral keys are used. The default value is
98 none, which disables DHE key exchange.
99 tls_config_set_ecdhecurves() specifies the names of the elliptic curves
101 that may be used during Elliptic Curve Diffie-Hellman Ephemeral (ECDHE)
102 key exchange. This is a comma separated list, given in order of prefer‐
103 ence. The special value of "default" will use the default curves (cur‐
104 rently X25519, P-256 and P-384). This function replaces
105 tls_config_set_ecdhecurve(), which is deprecated.
106 tls_config_prefer_ciphers_client() prefers ciphers in the client's cipher
108 list when selecting a cipher suite (server only). This is considered to
109 be less secure than preferring the server's list.
110 tls_config_prefer_ciphers_server() prefers ciphers in the server's cipher
112 list when selecting a cipher suite (server only). This is considered to
113 be more secure than preferring the client's list and is the default.
114
116 These functions return 0 on success or -1 on error.
117
119 tls_config_ocsp_require_stapling(3), tls_config_set_session_id(3),
120 tls_config_verify(3), tls_init(3), tls_load_file(3)
121
123 tls_config_set_ciphers() appeared in OpenBSD 5.6 and got its final name
124 in OpenBSD 5.7.
125 tls_config_set_protocols(), tls_config_parse_protocols(),
127 tls_config_set_dheparams(), and tls_config_set_ecdhecurve() appeared in
128 OpenBSD 5.7, tls_config_prefer_ciphers_client() and
129 tls_config_prefer_ciphers_server() in OpenBSD 5.9, and
130 tls_config_set_alpn() in OpenBSD 6.1.
131
133 Joel Sing <jsing@openbsd.org> with contributions from
134 Ted Unangst <tedu@openbsd.org> (tls_config_set_ciphers()) and
135 Reyk Floeter <reyk@openbsd.org> (tls_config_set_ecdhecurve())
136BSD January 2, 2021 BSD