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<SignatureAlgorithms>
313 This sets the supported signature algorithms for TLSv1.2 and TLSv1.3.
315 value is used directly for the supported signature algorithms extension. For
316 servers it is used to determine which signature algorithms to support.
318 The B<value> argument should be a colon separated list of signature algorithms
319 in order of decreasing preference of the form B<algorithm+hash> or
320 B<signature_scheme>. B<algorithm>
321 is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
322 OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
323 Note: algorithm and hash names are case sensitive.
324 B<signature_scheme> is one of the signature schemes defined in TLSv1.3,
325 specified using the IETF name, e.g., B<ecdsa_secp256r1_sha256>, B<ed25519>,
326 or B<rsa_pss_pss_sha256>.
328 If this option is not set then all signature algorithms supported by the
329 OpenSSL library are permissible.
331 Note: algorithms which specify a PKCS#1 v1.5 signature scheme (either by
332 using B<RSA> as the B<algorithm> or by using one of the B<rsa_pkcs1_*>
333 identifiers) are ignored in TLSv1.3 and will not be negotiated.
335 =item B<ClientSignatureAlgorithms>
337 This sets the supported signature algorithms associated with client
338 authentication for TLSv1.2 and TLSv1.3.
339 For servers the value is used in the
340 B<signature_algorithms> field of a B<CertificateRequest> message.
342 used to determine which signature algorithm to use with the client certificate.
343 If a server does not request a certificate this option has no effect.
345 The syntax of B<value> is identical to B<SignatureAlgorithms>. If not set then
346 the value set for B<SignatureAlgorithms> will be used instead.
350 This sets the supported groups. For clients, the groups are
351 sent using the supported groups extension. For servers, it is used
352 to determine which group to use. This setting affects groups used for
353 signatures (in TLSv1.2 and earlier) and key exchange. The first group listed
354 will also be used for the B<key_share> sent by a client in a TLSv1.3
357 The B<value> argument is a colon separated list of groups. The group can be
358 either the B<NIST> name (e.g. B<P-256>), some other commonly used name where
359 applicable (e.g. B<X25519>) or an OpenSSL OID name (e.g B<prime256v1>). Group
360 names are case sensitive. The list should be in order of preference with the
361 most preferred group first.
365 This is a synonym for the "Groups" command.
369 This sets the minimum supported SSL, TLS or DTLS version.
371 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
372 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
373 The value B<None> will disable the limit.
377 This sets the maximum supported SSL, TLS or DTLS version.
379 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
380 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
381 The value B<None> will disable the limit.
385 This can be used to enable or disable certain versions of the SSL,
386 TLS or DTLS protocol.
388 The B<value> argument is a comma separated list of supported protocols
389 to enable or disable.
390 If a protocol is preceded by B<-> that version is disabled.
392 All protocol versions are enabled by default.
393 You need to disable at least one protocol version for this setting have any
395 Only enabling some protocol versions does not disable the other protocol
398 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
399 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
400 The special value B<ALL> refers to all supported versions.
402 This can't enable protocols that are disabled using B<MinProtocol>
403 or B<MaxProtocol>, but can disable protocols that are still allowed
406 The B<Protocol> command is fragile and deprecated; do not use it.
407 Use B<MinProtocol> and B<MaxProtocol> instead.
408 If you do use B<Protocol>, make sure that the resulting range of enabled
409 protocols has no "holes", e.g. if TLS 1.0 and TLS 1.2 are both enabled, make
410 sure to also leave TLS 1.1 enabled.
414 The B<value> argument is a comma separated list of various flags to set.
415 If a flag string is preceded B<-> it is disabled.
416 See the L<SSL_CTX_set_options(3)> function for more details of
419 Each option is listed below. Where an operation is enabled by default
420 the B<-flag> syntax is needed to disable it.
422 B<SessionTicket>: session ticket support, enabled by default. Inverse of
423 B<SSL_OP_NO_TICKET>: that is B<-SessionTicket> is the same as setting
426 B<Compression>: SSL/TLS compression support, enabled by default. Inverse
427 of B<SSL_OP_NO_COMPRESSION>.
429 B<EmptyFragments>: use empty fragments as a countermeasure against a
430 SSL 3.0/TLS 1.0 protocol vulnerability affecting CBC ciphers. It
431 is set by default. Inverse of B<SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS>.
433 B<Bugs>: enable various bug workarounds. Same as B<SSL_OP_ALL>.
435 B<DHSingle>: enable single use DH keys, set by default. Inverse of
436 B<SSL_OP_DH_SINGLE>. Only used by servers.
438 B<ECDHSingle>: enable single use ECDH keys, set by default. Inverse of
439 B<SSL_OP_ECDH_SINGLE>. Only used by servers.
441 B<ServerPreference>: use server and not client preference order when
442 determining which cipher suite, signature algorithm or elliptic curve
443 to use for an incoming connection. Equivalent to
444 B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
446 B<PrioritizeChaCha>: prioritizes ChaCha ciphers when the client has a
447 ChaCha20 cipher at the top of its preference list. This usually indicates
448 a mobile client is in use. Equivalent to B<SSL_OP_PRIORITIZE_CHACHA>.
449 Only used by servers.
451 B<NoResumptionOnRenegotiation>: set
452 B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> flag. Only used by servers.
454 B<NoRenegotiation>: disables all attempts at renegotiation in TLSv1.2 and
455 earlier, same as setting B<SSL_OP_NO_RENEGOTIATION>.
457 B<UnsafeLegacyRenegotiation>: permits the use of unsafe legacy renegotiation.
458 Equivalent to B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
460 B<UnsafeLegacyServerConnect>: permits the use of unsafe legacy renegotiation
461 for OpenSSL clients only. Equivalent to B<SSL_OP_LEGACY_SERVER_CONNECT>.
464 B<EncryptThenMac>: use encrypt-then-mac extension, enabled by
465 default. Inverse of B<SSL_OP_NO_ENCRYPT_THEN_MAC>: that is,
466 B<-EncryptThenMac> is the same as setting B<SSL_OP_NO_ENCRYPT_THEN_MAC>.
468 B<AllowNoDHEKEX>: In TLSv1.3 allow a non-(ec)dhe based key exchange mode on
469 resumption. This means that there will be no forward secrecy for the resumed
470 session. Equivalent to B<SSL_OP_ALLOW_NO_DHE_KEX>.
472 B<MiddleboxCompat>: If set then dummy Change Cipher Spec (CCS) messages are sent
473 in TLSv1.3. This has the effect of making TLSv1.3 look more like TLSv1.2 so that
474 middleboxes that do not understand TLSv1.3 will not drop the connection. This
475 option is set by default. A future version of OpenSSL may not set this by
476 default. Equivalent to B<SSL_OP_ENABLE_MIDDLEBOX_COMPAT>.
478 B<AntiReplay>: If set then OpenSSL will automatically detect if a session ticket
479 has been used more than once, TLSv1.3 has been negotiated, and early data is
480 enabled on the server. A full handshake is forced if a session ticket is used a
481 second or subsequent time. This option is set by default and is only used by
482 servers. Anti-replay measures are required to comply with the TLSv1.3
483 specification. Some applications may be able to mitigate the replay risks in
484 other ways and in such cases the built-in OpenSSL functionality is not required.
485 Disabling anti-replay is equivalent to setting B<SSL_OP_NO_ANTI_REPLAY>.
487 B<ExtendedMasterSecret>: use extended master secret extension, enabled by
488 default. Inverse of B<SSL_OP_NO_EXTENDED_MASTER_SECRET>: that is,
489 B<-ExtendedMasterSecret> is the same as setting B<SSL_OP_NO_EXTENDED_MASTER_SECRET>.
493 The B<value> argument is a comma separated list of flags to set.
495 B<Peer> enables peer verification: for clients only.
497 B<Request> requests but does not require a certificate from the client.
500 B<Require> requests and requires a certificate from the client: an error
501 occurs if the client does not present a certificate. Servers only.
503 B<Once> requests a certificate from a client only on the initial connection:
504 not when renegotiating. Servers only.
506 B<RequestPostHandshake> configures the connection to support requests but does
507 not require a certificate from the client post-handshake. A certificate will
508 not be requested during the initial handshake. The server application must
509 provide a mechanism to request a certificate post-handshake. Servers only.
512 B<RequiresPostHandshake> configures the connection to support requests and
513 requires a certificate from the client post-handshake: an error occurs if the
514 client does not present a certificate. A certificate will not be requested
515 during the initial handshake. The server application must provide a mechanism
516 to request a certificate post-handshake. Servers only. TLSv1.3 only.
518 =item B<ClientCAFile>, B<ClientCAPath>
520 A file or directory of certificates in PEM format whose names are used as the
521 set of acceptable names for client CAs. Servers only. This option is only
522 supported if certificate operations are permitted.
526 =head1 SUPPORTED COMMAND TYPES
528 The function SSL_CONF_cmd_value_type() currently returns one of the following
533 =item B<SSL_CONF_TYPE_UNKNOWN>
535 The B<cmd> string is unrecognised, this return value can be use to flag
538 =item B<SSL_CONF_TYPE_STRING>
540 The value is a string without any specific structure.
542 =item B<SSL_CONF_TYPE_FILE>
544 The value is a file name.
546 =item B<SSL_CONF_TYPE_DIR>
548 The value is a directory name.
550 =item B<SSL_CONF_TYPE_NONE>
552 The value string is not used e.g. a command line option which doesn't take an
559 The order of operations is significant. This can be used to set either defaults
560 or values which cannot be overridden. For example if an application calls:
562 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
563 SSL_CONF_cmd(ctx, userparam, uservalue);
565 it will disable SSLv3 support by default but the user can override it. If
566 however the call sequence is:
568 SSL_CONF_cmd(ctx, userparam, uservalue);
569 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
571 SSLv3 is B<always> disabled and attempt to override this by the user are
574 By checking the return code of SSL_CONF_cmd() it is possible to query if a
575 given B<cmd> is recognised, this is useful if SSL_CONF_cmd() values are
576 mixed with additional application specific operations.
578 For example an application might call SSL_CONF_cmd() and if it returns
579 -2 (unrecognised command) continue with processing of application specific
582 Applications can also use SSL_CONF_cmd() to process command lines though the
583 utility function SSL_CONF_cmd_argv() is normally used instead. One way
584 to do this is to set the prefix to an appropriate value using
585 SSL_CONF_CTX_set1_prefix(), pass the current argument to B<cmd> and the
586 following argument to B<value> (which may be NULL).
588 In this case if the return value is positive then it is used to skip that
589 number of arguments as they have been processed by SSL_CONF_cmd(). If -2 is
590 returned then B<cmd> is not recognised and application specific arguments
591 can be checked instead. If -3 is returned a required argument is missing
592 and an error is indicated. If 0 is returned some other error occurred and
593 this can be reported back to the user.
595 The function SSL_CONF_cmd_value_type() can be used by applications to
596 check for the existence of a command or to perform additional syntax
597 checking or translation of the command value. For example if the return
598 value is B<SSL_CONF_TYPE_FILE> an application could translate a relative
599 pathname to an absolute pathname.
603 SSL_CONF_cmd() returns 1 if the value of B<cmd> is recognised and B<value> is
604 B<NOT> used and 2 if both B<cmd> and B<value> are used. In other words it
605 returns the number of arguments processed. This is useful when processing
608 A return value of -2 means B<cmd> is not recognised.
610 A return value of -3 means B<cmd> is recognised and the command requires a
611 value but B<value> is NULL.
613 A return code of 0 indicates that both B<cmd> and B<value> are valid but an
614 error occurred attempting to perform the operation: for example due to an
615 error in the syntax of B<value> in this case the error queue may provide
616 additional information.
620 Set supported signature algorithms:
622 SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256");
624 There are various ways to select the supported protocols.
626 This set the minimum protocol version to TLSv1, and so disables SSLv3.
627 This is the recommended way to disable protocols.
629 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1");
631 The following also disables SSLv3:
633 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
635 The following will first enable all protocols, and then disable
637 If no protocol versions were disabled before this has the same effect as
638 "-SSLv3", but if some versions were disables this will re-enable them before
641 SSL_CONF_cmd(ctx, "Protocol", "ALL,-SSLv3");
645 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1.2");
646 SSL_CONF_cmd(ctx, "MaxProtocol", "TLSv1.2");
648 This also only enables TLSv1.2:
650 SSL_CONF_cmd(ctx, "Protocol", "-ALL,TLSv1.2");
652 Disable TLS session tickets:
654 SSL_CONF_cmd(ctx, "Options", "-SessionTicket");
658 SSL_CONF_cmd(ctx, "Options", "Compression");
660 Set supported curves to P-256, P-384:
662 SSL_CONF_cmd(ctx, "Curves", "P-256:P-384");
666 L<SSL_CONF_CTX_new(3)>,
667 L<SSL_CONF_CTX_set_flags(3)>,
668 L<SSL_CONF_CTX_set1_prefix(3)>,
669 L<SSL_CONF_CTX_set_ssl_ctx(3)>,
670 L<SSL_CONF_cmd_argv(3)>,
671 L<SSL_CTX_set_options(3)>
675 The SSL_CONF_cmd() function was added in OpenSSL 1.0.2.
677 The B<SSL_OP_NO_SSL2> option doesn't have effect since 1.1.0, but the macro
678 is retained for backwards compatibility.
680 The B<SSL_CONF_TYPE_NONE> was added in OpenSSL 1.1.0. In earlier versions of
681 OpenSSL passing a command which didn't take an argument would return
682 B<SSL_CONF_TYPE_UNKNOWN>.
684 B<MinProtocol> and B<MaxProtocol> where added in OpenSSL 1.1.0.
686 B<AllowNoDHEKEX> and B<PrioritizeChaCha> were added in OpenSSL 1.1.1.
690 Copyright 2012-2018 The OpenSSL Project Authors. All Rights Reserved.
692 Licensed under the Apache License 2.0 (the "License"). You may not use
693 this file except in compliance with the License. You can obtain a copy
694 in the file LICENSE in the source distribution or at
695 L<https://www.openssl.org/source/license.html>.