5 SSL_CONF_cmd_value_type,
6 SSL_CONF_cmd - send configuration command
10 #include <openssl/ssl.h>
12 int SSL_CONF_cmd(SSL_CONF_CTX *cctx, const char *cmd, const char *value);
13 int SSL_CONF_cmd_value_type(SSL_CONF_CTX *cctx, const char *cmd);
17 The function SSL_CONF_cmd() performs configuration operation B<cmd> with
18 optional parameter B<value> on B<ctx>. Its purpose is to simplify application
19 configuration of B<SSL_CTX> or B<SSL> structures by providing a common
20 framework for command line options or configuration files.
22 SSL_CONF_cmd_value_type() returns the type of value that B<cmd> refers to.
24 =head1 SUPPORTED COMMAND LINE COMMANDS
26 Currently supported B<cmd> names for command lines (i.e. when the
27 flag B<SSL_CONF_CMDLINE> is set) are listed below. Note: all B<cmd> names
28 are case sensitive. Unless otherwise stated commands can be used by
29 both clients and servers and the B<value> parameter is not used. The default
30 prefix for command line commands is B<-> and that is reflected below.
36 This sets the supported signature algorithms for TLSv1.2 and TLSv1.3.
38 value is used directly for the supported signature algorithms extension. For
39 servers it is used to determine which signature algorithms to support.
41 The B<value> argument should be a colon separated list of signature algorithms
42 in order of decreasing preference of the form B<algorithm+hash> or
43 B<signature_scheme>. B<algorithm>
44 is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
45 OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
46 Note: algorithm and hash names are case sensitive.
47 B<signature_scheme> is one of the signature schemes defined in TLSv1.3,
48 specified using the IETF name, e.g., B<ecdsa_secp256r1_sha256>, B<ed25519>,
49 or B<rsa_pss_pss_sha256>.
51 If this option is not set then all signature algorithms supported by the
52 OpenSSL library are permissible.
54 Note: algorithms which specify a PKCS#1 v1.5 signature scheme (either by
55 using B<RSA> as the B<algorithm> or by using one of the B<rsa_pkcs1_*>
56 identifiers) are ignored in TLSv1.3 and will not be negotiated.
58 =item B<-client_sigalgs>
60 This sets the supported signature algorithms associated with client
61 authentication for TLSv1.2 and TLSv1.3.
62 For servers the value is used in the
63 B<signature_algorithms> field of a B<CertificateRequest> message.
65 used to determine which signature algorithm to use with the client certificate.
66 If a server does not request a certificate this option has no effect.
68 The syntax of B<value> is identical to B<-sigalgs>. If not set then
69 the value set for B<-sigalgs> will be used instead.
73 This sets the supported groups. For clients, the groups are
74 sent using the supported groups extension. For servers, it is used
75 to determine which group to use. This setting affects groups used for
76 signatures (in TLSv1.2 and earlier) and key exchange. The first group listed
77 will also be used for the B<key_share> sent by a client in a TLSv1.3
80 The B<value> argument is a colon separated list of groups. The group can be
81 either the B<NIST> name (e.g. B<P-256>), some other commonly used name where
82 applicable (e.g. B<X25519>) or an OpenSSL OID name (e.g B<prime256v1>). Group
83 names are case sensitive. The list should be in order of preference with the
84 most preferred group first.
88 This is a synonym for the "-groups" command.
92 This sets the temporary curve used for ephemeral ECDH modes. Only used by
95 The B<value> argument is a curve name or the special value B<auto> which
96 picks an appropriate curve based on client and server preferences. The curve
97 can be either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name
98 (e.g B<prime256v1>). Curve names are case sensitive.
102 Sets the TLSv1.2 and below ciphersuite list to B<value>. This list will be
103 combined with any configured TLSv1.3 ciphersuites. Note: syntax checking
104 of B<value> is currently not performed unless a B<SSL> or B<SSL_CTX> structure is
105 associated with B<cctx>.
107 =item B<-ciphersuites>
109 Sets the available ciphersuites for TLSv1.3 to value. This is a simple colon
110 (":") separated list of TLSv1.3 ciphersuite names in order of preference. This
111 list will be combined any configured TLSv1.2 and below ciphersuites.
112 See L<ciphers(1)> for more information.
117 Attempts to use the file B<value> as the certificate for the appropriate
118 context. It currently uses SSL_CTX_use_certificate_chain_file() if an B<SSL_CTX>
119 structure is set or SSL_use_certificate_file() with filetype PEM if an B<SSL>
120 structure is set. This option is only supported if certificate operations
125 Attempts to use the file B<value> as the private key for the appropriate
126 context. This option is only supported if certificate operations
127 are permitted. Note: if no B<-key> option is set then a private key is
128 not loaded unless the flag B<SSL_CONF_FLAG_REQUIRE_PRIVATE> is set.
132 Attempts to use the file B<value> as the set of temporary DH parameters for
133 the appropriate context. This option is only supported if certificate
134 operations are permitted.
136 =item B<-record_padding>
138 Attempts to pad TLSv1.3 records so that they are a multiple of B<value> in
139 length on send. A B<value> of 0 or 1 turns off padding. Otherwise, the
140 B<value> must be >1 or <=16384.
142 =item B<-no_renegotiation>
144 Disables all attempts at renegotiation in TLSv1.2 and earlier, same as setting
145 B<SSL_OP_NO_RENEGOTIATION>.
147 =item B<-min_protocol>, B<-max_protocol>
149 Sets the minimum and maximum supported protocol.
150 Currently supported protocol values are B<SSLv3>, B<TLSv1>,
151 B<TLSv1.1>, B<TLSv1.2>, B<TLSv1.3> for TLS and B<DTLSv1>, B<DTLSv1.2> for DTLS,
152 and B<None> for no limit.
153 If either bound is not specified then only the other bound applies,
155 To restrict the supported protocol versions use these commands rather
156 than the deprecated alternative commands below.
158 =item B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>, B<-no_tls1_3>
160 Disables protocol support for SSLv3, TLSv1.0, TLSv1.1, TLSv1.2 or TLSv1.3 by
161 setting the corresponding options B<SSL_OP_NO_SSLv3>, B<SSL_OP_NO_TLSv1>,
162 B<SSL_OP_NO_TLSv1_1>, B<SSL_OP_NO_TLSv1_2> and B<SSL_OP_NO_TLSv1_3>
163 respectively. These options are deprecated, instead use B<-min_protocol> and
168 Various bug workarounds are set, same as setting B<SSL_OP_ALL>.
172 Enables support for SSL/TLS compression, same as clearing
173 B<SSL_OP_NO_COMPRESSION>.
174 This command was introduced in OpenSSL 1.1.0.
175 As of OpenSSL 1.1.0, compression is off by default.
179 Disables support for SSL/TLS compression, same as setting
180 B<SSL_OP_NO_COMPRESSION>.
181 As of OpenSSL 1.1.0, compression is off by default.
185 Disables support for session tickets, same as setting B<SSL_OP_NO_TICKET>.
189 Use server and not client preference order when determining which cipher suite,
190 signature algorithm or elliptic curve to use for an incoming connection.
191 Equivalent to B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
193 =item B<-prioritize_chacha>
195 Prioritize ChaCha ciphers when the client has a ChaCha20 cipher at the top of
196 its preference list. This usually indicates a client without AES hardware
197 acceleration (e.g. mobile) is in use. Equivalent to B<SSL_OP_PRIORITIZE_CHACHA>.
198 Only used by servers. Requires B<-serverpref>.
200 =item B<-no_resumption_on_reneg>
202 set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag. Only used by servers.
204 =item B<-legacyrenegotiation>
206 permits the use of unsafe legacy renegotiation. Equivalent to setting
207 B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
209 =item B<-legacy_server_connect>, B<-no_legacy_server_connect>
211 permits or prohibits the use of unsafe legacy renegotiation for OpenSSL
212 clients only. Equivalent to setting or clearing B<SSL_OP_LEGACY_SERVER_CONNECT>.
215 =item B<-allow_no_dhe_kex>
217 In TLSv1.3 allow a non-(ec)dhe based key exchange mode on resumption. This means
218 that there will be no forward secrecy for the resumed session.
222 enables strict mode protocol handling. Equivalent to setting
223 B<SSL_CERT_FLAG_TLS_STRICT>.
225 =item B<-anti_replay>, B<-no_anti_replay>
227 Switches replay protection, on or off respectively. With replay protection on,
228 OpenSSL will automatically detect if a session ticket has been used more than
229 once, TLSv1.3 has been negotiated, and early data is enabled on the server. A
230 full handshake is forced if a session ticket is used a second or subsequent
231 time. Anti-Replay is on by default unless overridden by a configuration file and
232 is only used by servers. Anti-replay measures are required for compliance with
233 the TLSv1.3 specification. Some applications may be able to mitigate the replay
234 risks in other ways and in such cases the built-in OpenSSL functionality is not
235 required. Switching off anti-replay is equivalent to B<SSL_OP_NO_ANTI_REPLAY>.
239 =head1 SUPPORTED CONFIGURATION FILE COMMANDS
241 Currently supported B<cmd> names for configuration files (i.e. when the
242 flag B<SSL_CONF_FLAG_FILE> is set) are listed below. All configuration file
243 B<cmd> names are case insensitive so B<signaturealgorithms> is recognised
244 as well as B<SignatureAlgorithms>. Unless otherwise stated the B<value> names
245 are also case insensitive.
247 Note: the command prefix (if set) alters the recognised B<cmd> values.
251 =item B<CipherString>
253 Sets the ciphersuite list for TLSv1.2 and below to B<value>. This list will be
254 combined with any configured TLSv1.3 ciphersuites. Note: syntax
255 checking of B<value> is currently not performed unless an B<SSL> or B<SSL_CTX>
256 structure is associated with B<cctx>.
258 =item B<Ciphersuites>
260 Sets the available ciphersuites for TLSv1.3 to B<value>. This is a simple colon
261 (":") separated list of TLSv1.3 ciphersuite names in order of preference. This
262 list will be combined any configured TLSv1.2 and below ciphersuites.
263 See L<ciphers(1)> for more information.
267 Attempts to use the file B<value> as the certificate for the appropriate
268 context. It currently uses SSL_CTX_use_certificate_chain_file() if an B<SSL_CTX>
269 structure is set or SSL_use_certificate_file() with filetype PEM if an B<SSL>
270 structure is set. This option is only supported if certificate operations
275 Attempts to use the file B<value> as the private key for the appropriate
276 context. This option is only supported if certificate operations
277 are permitted. Note: if no B<PrivateKey> option is set then a private key is
278 not loaded unless the B<SSL_CONF_FLAG_REQUIRE_PRIVATE> is set.
280 =item B<ChainCAFile>, B<ChainCAPath>, B<VerifyCAFile>, B<VerifyCAPath>
282 These options indicate a file or directory used for building certificate
283 chains or verifying certificate chains. These options are only supported
284 if certificate operations are permitted.
286 =item B<RequestCAFile>
288 This option indicates a file containing a set of certificates in PEM form.
289 The subject names of the certificates are sent to the peer in the
290 B<certificate_authorities> extension for TLS 1.3 (in ClientHello or
291 CertificateRequest) or in a certificate request for previous versions or
294 =item B<ServerInfoFile>
296 Attempts to use the file B<value> in the "serverinfo" extension using the
297 function SSL_CTX_use_serverinfo_file.
299 =item B<DHParameters>
301 Attempts to use the file B<value> as the set of temporary DH parameters for
302 the appropriate context. This option is only supported if certificate
303 operations are permitted.
305 =item B<RecordPadding>
307 Attempts to pad TLSv1.3 records so that they are a multiple of B<value> in
308 length on send. A B<value> of 0 or 1 turns off padding. Otherwise, the
309 B<value> must be >1 or <=16384.
311 =item B<NoRenegotiation>
313 Disables all attempts at renegotiation in TLSv1.2 and earlier, same as setting
314 B<SSL_OP_NO_RENEGOTIATION>.
316 =item B<SignatureAlgorithms>
318 This sets the supported signature algorithms for TLSv1.2 and TLSv1.3.
320 value is used directly for the supported signature algorithms extension. For
321 servers it is used to determine which signature algorithms to support.
323 The B<value> argument should be a colon separated list of signature algorithms
324 in order of decreasing preference of the form B<algorithm+hash> or
325 B<signature_scheme>. B<algorithm>
326 is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
327 OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
328 Note: algorithm and hash names are case sensitive.
329 B<signature_scheme> is one of the signature schemes defined in TLSv1.3,
330 specified using the IETF name, e.g., B<ecdsa_secp256r1_sha256>, B<ed25519>,
331 or B<rsa_pss_pss_sha256>.
333 If this option is not set then all signature algorithms supported by the
334 OpenSSL library are permissible.
336 Note: algorithms which specify a PKCS#1 v1.5 signature scheme (either by
337 using B<RSA> as the B<algorithm> or by using one of the B<rsa_pkcs1_*>
338 identifiers) are ignored in TLSv1.3 and will not be negotiated.
340 =item B<ClientSignatureAlgorithms>
342 This sets the supported signature algorithms associated with client
343 authentication for TLSv1.2 and TLSv1.3.
344 For servers the value is used in the
345 B<signature_algorithms> field of a B<CertificateRequest> message.
347 used to determine which signature algorithm to use with the client certificate.
348 If a server does not request a certificate this option has no effect.
350 The syntax of B<value> is identical to B<SignatureAlgorithms>. If not set then
351 the value set for B<SignatureAlgorithms> will be used instead.
355 This sets the supported groups. For clients, the groups are
356 sent using the supported groups extension. For servers, it is used
357 to determine which group to use. This setting affects groups used for
358 signatures (in TLSv1.2 and earlier) and key exchange. The first group listed
359 will also be used for the B<key_share> sent by a client in a TLSv1.3
362 The B<value> argument is a colon separated list of groups. The group can be
363 either the B<NIST> name (e.g. B<P-256>), some other commonly used name where
364 applicable (e.g. B<X25519>) or an OpenSSL OID name (e.g B<prime256v1>). Group
365 names are case sensitive. The list should be in order of preference with the
366 most preferred group first.
370 This is a synonym for the "Groups" command.
374 This sets the minimum supported SSL, TLS or DTLS version.
376 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
377 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
378 The value B<None> will disable the limit.
382 This sets the maximum supported SSL, TLS or DTLS version.
384 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
385 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
386 The value B<None> will disable the limit.
390 This can be used to enable or disable certain versions of the SSL,
391 TLS or DTLS protocol.
393 The B<value> argument is a comma separated list of supported protocols
394 to enable or disable.
395 If a protocol is preceded by B<-> that version is disabled.
397 All protocol versions are enabled by default.
398 You need to disable at least one protocol version for this setting have any
400 Only enabling some protocol versions does not disable the other protocol
403 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
404 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
405 The special value B<ALL> refers to all supported versions.
407 This can't enable protocols that are disabled using B<MinProtocol>
408 or B<MaxProtocol>, but can disable protocols that are still allowed
411 The B<Protocol> command is fragile and deprecated; do not use it.
412 Use B<MinProtocol> and B<MaxProtocol> instead.
413 If you do use B<Protocol>, make sure that the resulting range of enabled
414 protocols has no "holes", e.g. if TLS 1.0 and TLS 1.2 are both enabled, make
415 sure to also leave TLS 1.1 enabled.
419 The B<value> argument is a comma separated list of various flags to set.
420 If a flag string is preceded B<-> it is disabled.
421 See the L<SSL_CTX_set_options(3)> function for more details of
424 Each option is listed below. Where an operation is enabled by default
425 the B<-flag> syntax is needed to disable it.
427 B<SessionTicket>: session ticket support, enabled by default. Inverse of
428 B<SSL_OP_NO_TICKET>: that is B<-SessionTicket> is the same as setting
431 B<Compression>: SSL/TLS compression support, enabled by default. Inverse
432 of B<SSL_OP_NO_COMPRESSION>.
434 B<EmptyFragments>: use empty fragments as a countermeasure against a
435 SSL 3.0/TLS 1.0 protocol vulnerability affecting CBC ciphers. It
436 is set by default. Inverse of B<SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS>.
438 B<Bugs>: enable various bug workarounds. Same as B<SSL_OP_ALL>.
440 B<DHSingle>: enable single use DH keys, set by default. Inverse of
441 B<SSL_OP_DH_SINGLE>. Only used by servers.
443 B<ECDHSingle>: enable single use ECDH keys, set by default. Inverse of
444 B<SSL_OP_ECDH_SINGLE>. Only used by servers.
446 B<ServerPreference>: use server and not client preference order when
447 determining which cipher suite, signature algorithm or elliptic curve
448 to use for an incoming connection. Equivalent to
449 B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
451 B<PrioritizeChaCha>: prioritizes ChaCha ciphers when the client has a
452 ChaCha20 cipher at the top of its preference list. This usually indicates
453 a mobile client is in use. Equivalent to B<SSL_OP_PRIORITIZE_CHACHA>.
454 Only used by servers.
456 B<NoResumptionOnRenegotiation>: set
457 B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> flag. Only used by servers.
459 B<UnsafeLegacyRenegotiation>: permits the use of unsafe legacy renegotiation.
460 Equivalent to B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
462 B<UnsafeLegacyServerConnect>: permits the use of unsafe legacy renegotiation
463 for OpenSSL clients only. Equivalent to B<SSL_OP_LEGACY_SERVER_CONNECT>.
466 B<EncryptThenMac>: use encrypt-then-mac extension, enabled by
467 default. Inverse of B<SSL_OP_NO_ENCRYPT_THEN_MAC>: that is,
468 B<-EncryptThenMac> is the same as setting B<SSL_OP_NO_ENCRYPT_THEN_MAC>.
470 B<AllowNoDHEKEX>: In TLSv1.3 allow a non-(ec)dhe based key exchange mode on
471 resumption. This means that there will be no forward secrecy for the resumed
472 session. Equivalent to B<SSL_OP_ALLOW_NO_DHE_KEX>.
474 B<MiddleboxCompat>: If set then dummy Change Cipher Spec (CCS) messages are sent
475 in TLSv1.3. This has the effect of making TLSv1.3 look more like TLSv1.2 so that
476 middleboxes that do not understand TLSv1.3 will not drop the connection. This
477 option is set by default. A future version of OpenSSL may not set this by
478 default. Equivalent to B<SSL_OP_ENABLE_MIDDLEBOX_COMPAT>.
480 B<AntiReplay>: If set then OpenSSL will automatically detect if a session ticket
481 has been used more than once, TLSv1.3 has been negotiated, and early data is
482 enabled on the server. A full handshake is forced if a session ticket is used a
483 second or subsequent time. This option is set by default and is only used by
484 servers. Anti-replay measures are required to comply with the TLSv1.3
485 specification. Some applications may be able to mitigate the replay risks in
486 other ways and in such cases the built-in OpenSSL functionality is not required.
487 Disabling anti-replay is equivalent to setting B<SSL_OP_NO_ANTI_REPLAY>.
491 The B<value> argument is a comma separated list of flags to set.
493 B<Peer> enables peer verification: for clients only.
495 B<Request> requests but does not require a certificate from the client.
498 B<Require> requests and requires a certificate from the client: an error
499 occurs if the client does not present a certificate. Servers only.
501 B<Once> requests a certificate from a client only on the initial connection:
502 not when renegotiating. Servers only.
504 B<RequestPostHandshake> configures the connection to support requests but does
505 not require a certificate from the client post-handshake. A certificate will
506 not be requested during the initial handshake. The server application must
507 provide a mechanism to request a certificate post-handshake. Servers only.
510 B<RequiresPostHandshake> configures the connection to support requests and
511 requires a certificate from the client post-handshake: an error occurs if the
512 client does not present a certificate. A certificate will not be requested
513 during the initial handshake. The server application must provide a mechanism
514 to request a certificate post-handshake. Servers only. TLSv1.3 only.
516 =item B<ClientCAFile>, B<ClientCAPath>
518 A file or directory of certificates in PEM format whose names are used as the
519 set of acceptable names for client CAs. Servers only. This option is only
520 supported if certificate operations are permitted.
524 =head1 SUPPORTED COMMAND TYPES
526 The function SSL_CONF_cmd_value_type() currently returns one of the following
531 =item B<SSL_CONF_TYPE_UNKNOWN>
533 The B<cmd> string is unrecognised, this return value can be use to flag
536 =item B<SSL_CONF_TYPE_STRING>
538 The value is a string without any specific structure.
540 =item B<SSL_CONF_TYPE_FILE>
542 The value is a file name.
544 =item B<SSL_CONF_TYPE_DIR>
546 The value is a directory name.
548 =item B<SSL_CONF_TYPE_NONE>
550 The value string is not used e.g. a command line option which doesn't take an
557 The order of operations is significant. This can be used to set either defaults
558 or values which cannot be overridden. For example if an application calls:
560 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
561 SSL_CONF_cmd(ctx, userparam, uservalue);
563 it will disable SSLv3 support by default but the user can override it. If
564 however the call sequence is:
566 SSL_CONF_cmd(ctx, userparam, uservalue);
567 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
569 SSLv3 is B<always> disabled and attempt to override this by the user are
572 By checking the return code of SSL_CONF_cmd() it is possible to query if a
573 given B<cmd> is recognised, this is useful if SSL_CONF_cmd() values are
574 mixed with additional application specific operations.
576 For example an application might call SSL_CONF_cmd() and if it returns
577 -2 (unrecognised command) continue with processing of application specific
580 Applications can also use SSL_CONF_cmd() to process command lines though the
581 utility function SSL_CONF_cmd_argv() is normally used instead. One way
582 to do this is to set the prefix to an appropriate value using
583 SSL_CONF_CTX_set1_prefix(), pass the current argument to B<cmd> and the
584 following argument to B<value> (which may be NULL).
586 In this case if the return value is positive then it is used to skip that
587 number of arguments as they have been processed by SSL_CONF_cmd(). If -2 is
588 returned then B<cmd> is not recognised and application specific arguments
589 can be checked instead. If -3 is returned a required argument is missing
590 and an error is indicated. If 0 is returned some other error occurred and
591 this can be reported back to the user.
593 The function SSL_CONF_cmd_value_type() can be used by applications to
594 check for the existence of a command or to perform additional syntax
595 checking or translation of the command value. For example if the return
596 value is B<SSL_CONF_TYPE_FILE> an application could translate a relative
597 pathname to an absolute pathname.
601 Set supported signature algorithms:
603 SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256");
605 There are various ways to select the supported protocols.
607 This set the minimum protocol version to TLSv1, and so disables SSLv3.
608 This is the recommended way to disable protocols.
610 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1");
612 The following also disables SSLv3:
614 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
616 The following will first enable all protocols, and then disable
618 If no protocol versions were disabled before this has the same effect as
619 "-SSLv3", but if some versions were disables this will re-enable them before
622 SSL_CONF_cmd(ctx, "Protocol", "ALL,-SSLv3");
626 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1.2");
627 SSL_CONF_cmd(ctx, "MaxProtocol", "TLSv1.2");
629 This also only enables TLSv1.2:
631 SSL_CONF_cmd(ctx, "Protocol", "-ALL,TLSv1.2");
633 Disable TLS session tickets:
635 SSL_CONF_cmd(ctx, "Options", "-SessionTicket");
639 SSL_CONF_cmd(ctx, "Options", "Compression");
641 Set supported curves to P-256, P-384:
643 SSL_CONF_cmd(ctx, "Curves", "P-256:P-384");
647 SSL_CONF_cmd() returns 1 if the value of B<cmd> is recognised and B<value> is
648 B<NOT> used and 2 if both B<cmd> and B<value> are used. In other words it
649 returns the number of arguments processed. This is useful when processing
652 A return value of -2 means B<cmd> is not recognised.
654 A return value of -3 means B<cmd> is recognised and the command requires a
655 value but B<value> is NULL.
657 A return code of 0 indicates that both B<cmd> and B<value> are valid but an
658 error occurred attempting to perform the operation: for example due to an
659 error in the syntax of B<value> in this case the error queue may provide
660 additional information.
664 L<SSL_CONF_CTX_new(3)>,
665 L<SSL_CONF_CTX_set_flags(3)>,
666 L<SSL_CONF_CTX_set1_prefix(3)>,
667 L<SSL_CONF_CTX_set_ssl_ctx(3)>,
668 L<SSL_CONF_cmd_argv(3)>,
669 L<SSL_CTX_set_options(3)>
673 SSL_CONF_cmd() was first added to OpenSSL 1.0.2
675 B<SSL_OP_NO_SSL2> doesn't have effect since 1.1.0, but the macro is retained
676 for backwards compatibility.
678 B<SSL_CONF_TYPE_NONE> was first added to OpenSSL 1.1.0. In earlier versions of
679 OpenSSL passing a command which didn't take an argument would return
680 B<SSL_CONF_TYPE_UNKNOWN>.
682 B<MinProtocol> and B<MaxProtocol> where added in OpenSSL 1.1.0.
684 B<AllowNoDHEKEX> and B<PrioritizeChaCha> were added in OpenSSL 1.1.1.
688 Copyright 2012-2018 The OpenSSL Project Authors. All Rights Reserved.
690 Licensed under the OpenSSL license (the "License"). You may not use
691 this file except in compliance with the License. You can obtain a copy
692 in the file LICENSE in the source distribution or at
693 L<https://www.openssl.org/source/license.html>.