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>, B<TLSv1.1>,
151 B<TLSv1.2>, B<TLSv1.3> for TLS; B<DTLSv1>, B<DTLSv1.2> for DTLS, and B<None>
153 If either the lower or upper bound is not specified then only the other bound
154 applies, if specified.
155 If your application supports both TLS and DTLS you can specify any of these
156 options twice, once with a bound for TLS and again with an appropriate bound
158 To restrict the supported protocol versions use these commands rather than the
159 deprecated alternative commands below.
161 =item B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>, B<-no_tls1_3>
163 Disables protocol support for SSLv3, TLSv1.0, TLSv1.1, TLSv1.2 or TLSv1.3 by
164 setting the corresponding options B<SSL_OP_NO_SSLv3>, B<SSL_OP_NO_TLSv1>,
165 B<SSL_OP_NO_TLSv1_1>, B<SSL_OP_NO_TLSv1_2> and B<SSL_OP_NO_TLSv1_3>
166 respectively. These options are deprecated, instead use B<-min_protocol> and
171 Various bug workarounds are set, same as setting B<SSL_OP_ALL>.
175 Enables support for SSL/TLS compression, same as clearing
176 B<SSL_OP_NO_COMPRESSION>.
177 This command was introduced in OpenSSL 1.1.0.
178 As of OpenSSL 1.1.0, compression is off by default.
182 Disables support for SSL/TLS compression, same as setting
183 B<SSL_OP_NO_COMPRESSION>.
184 As of OpenSSL 1.1.0, compression is off by default.
188 Disables support for session tickets, same as setting B<SSL_OP_NO_TICKET>.
192 Use server and not client preference order when determining which cipher suite,
193 signature algorithm or elliptic curve to use for an incoming connection.
194 Equivalent to B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
196 =item B<-prioritize_chacha>
198 Prioritize ChaCha ciphers when the client has a ChaCha20 cipher at the top of
199 its preference list. This usually indicates a client without AES hardware
200 acceleration (e.g. mobile) is in use. Equivalent to B<SSL_OP_PRIORITIZE_CHACHA>.
201 Only used by servers. Requires B<-serverpref>.
203 =item B<-no_resumption_on_reneg>
205 set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag. Only used by servers.
207 =item B<-legacyrenegotiation>
209 permits the use of unsafe legacy renegotiation. Equivalent to setting
210 B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
212 =item B<-legacy_server_connect>, B<-no_legacy_server_connect>
214 permits or prohibits the use of unsafe legacy renegotiation for OpenSSL
215 clients only. Equivalent to setting or clearing B<SSL_OP_LEGACY_SERVER_CONNECT>.
218 =item B<-allow_no_dhe_kex>
220 In TLSv1.3 allow a non-(ec)dhe based key exchange mode on resumption. This means
221 that there will be no forward secrecy for the resumed session.
225 enables strict mode protocol handling. Equivalent to setting
226 B<SSL_CERT_FLAG_TLS_STRICT>.
228 =item B<-anti_replay>, B<-no_anti_replay>
230 Switches replay protection, on or off respectively. With replay protection on,
231 OpenSSL will automatically detect if a session ticket has been used more than
232 once, TLSv1.3 has been negotiated, and early data is enabled on the server. A
233 full handshake is forced if a session ticket is used a second or subsequent
234 time. Anti-Replay is on by default unless overridden by a configuration file and
235 is only used by servers. Anti-replay measures are required for compliance with
236 the TLSv1.3 specification. Some applications may be able to mitigate the replay
237 risks in other ways and in such cases the built-in OpenSSL functionality is not
238 required. Switching off anti-replay is equivalent to B<SSL_OP_NO_ANTI_REPLAY>.
242 =head1 SUPPORTED CONFIGURATION FILE COMMANDS
244 Currently supported B<cmd> names for configuration files (i.e. when the
245 flag B<SSL_CONF_FLAG_FILE> is set) are listed below. All configuration file
246 B<cmd> names are case insensitive so B<signaturealgorithms> is recognised
247 as well as B<SignatureAlgorithms>. Unless otherwise stated the B<value> names
248 are also case insensitive.
250 Note: the command prefix (if set) alters the recognised B<cmd> values.
254 =item B<CipherString>
256 Sets the ciphersuite list for TLSv1.2 and below to B<value>. This list will be
257 combined with any configured TLSv1.3 ciphersuites. Note: syntax
258 checking of B<value> is currently not performed unless an B<SSL> or B<SSL_CTX>
259 structure is associated with B<cctx>.
261 =item B<Ciphersuites>
263 Sets the available ciphersuites for TLSv1.3 to B<value>. This is a simple colon
264 (":") separated list of TLSv1.3 ciphersuite names in order of preference. This
265 list will be combined any configured TLSv1.2 and below ciphersuites.
266 See L<ciphers(1)> for more information.
270 Attempts to use the file B<value> as the certificate for the appropriate
271 context. It currently uses SSL_CTX_use_certificate_chain_file() if an B<SSL_CTX>
272 structure is set or SSL_use_certificate_file() with filetype PEM if an B<SSL>
273 structure is set. This option is only supported if certificate operations
278 Attempts to use the file B<value> as the private key for the appropriate
279 context. This option is only supported if certificate operations
280 are permitted. Note: if no B<PrivateKey> option is set then a private key is
281 not loaded unless the B<SSL_CONF_FLAG_REQUIRE_PRIVATE> is set.
283 =item B<ChainCAFile>, B<ChainCAPath>, B<VerifyCAFile>, B<VerifyCAPath>
285 These options indicate a file or directory used for building certificate
286 chains or verifying certificate chains. These options are only supported
287 if certificate operations are permitted.
289 =item B<RequestCAFile>
291 This option indicates a file containing a set of certificates in PEM form.
292 The subject names of the certificates are sent to the peer in the
293 B<certificate_authorities> extension for TLS 1.3 (in ClientHello or
294 CertificateRequest) or in a certificate request for previous versions or
297 =item B<ServerInfoFile>
299 Attempts to use the file B<value> in the "serverinfo" extension using the
300 function SSL_CTX_use_serverinfo_file.
302 =item B<DHParameters>
304 Attempts to use the file B<value> as the set of temporary DH parameters for
305 the appropriate context. This option is only supported if certificate
306 operations are permitted.
308 =item B<RecordPadding>
310 Attempts to pad TLSv1.3 records so that they are a multiple of B<value> in
311 length on send. A B<value> of 0 or 1 turns off padding. Otherwise, the
312 B<value> must be >1 or <=16384.
314 =item B<SignatureAlgorithms>
316 This sets the supported signature algorithms for TLSv1.2 and TLSv1.3.
318 value is used directly for the supported signature algorithms extension. For
319 servers it is used to determine which signature algorithms to support.
321 The B<value> argument should be a colon separated list of signature algorithms
322 in order of decreasing preference of the form B<algorithm+hash> or
323 B<signature_scheme>. B<algorithm>
324 is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
325 OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
326 Note: algorithm and hash names are case sensitive.
327 B<signature_scheme> is one of the signature schemes defined in TLSv1.3,
328 specified using the IETF name, e.g., B<ecdsa_secp256r1_sha256>, B<ed25519>,
329 or B<rsa_pss_pss_sha256>.
331 If this option is not set then all signature algorithms supported by the
332 OpenSSL library are permissible.
334 Note: algorithms which specify a PKCS#1 v1.5 signature scheme (either by
335 using B<RSA> as the B<algorithm> or by using one of the B<rsa_pkcs1_*>
336 identifiers) are ignored in TLSv1.3 and will not be negotiated.
338 =item B<ClientSignatureAlgorithms>
340 This sets the supported signature algorithms associated with client
341 authentication for TLSv1.2 and TLSv1.3.
342 For servers the value is used in the
343 B<signature_algorithms> field of a B<CertificateRequest> message.
345 used to determine which signature algorithm to use with the client certificate.
346 If a server does not request a certificate this option has no effect.
348 The syntax of B<value> is identical to B<SignatureAlgorithms>. If not set then
349 the value set for B<SignatureAlgorithms> will be used instead.
353 This sets the supported groups. For clients, the groups are
354 sent using the supported groups extension. For servers, it is used
355 to determine which group to use. This setting affects groups used for
356 signatures (in TLSv1.2 and earlier) and key exchange. The first group listed
357 will also be used for the B<key_share> sent by a client in a TLSv1.3
360 The B<value> argument is a colon separated list of groups. The group can be
361 either the B<NIST> name (e.g. B<P-256>), some other commonly used name where
362 applicable (e.g. B<X25519>) or an OpenSSL OID name (e.g. B<prime256v1>). Group
363 names are case sensitive. The list should be in order of preference with the
364 most preferred group first.
368 This is a synonym for the "Groups" command.
372 This sets the minimum supported SSL, TLS or DTLS version.
374 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
375 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
376 The SSL and TLS bounds apply only to TLS-based contexts, while the DTLS bounds
377 apply only to DTLS-based contexts.
378 The command can be repeated with one instance setting a TLS bound, and the
379 other setting a DTLS bound.
380 The value B<None> applies to both types of contexts and disables the limits.
384 This sets the maximum supported SSL, TLS or DTLS version.
386 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
387 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
388 The SSL and TLS bounds apply only to TLS-based contexts, while the DTLS bounds
389 apply only to DTLS-based contexts.
390 The command can be repeated with one instance setting a TLS bound, and the
391 other setting a DTLS bound.
392 The value B<None> applies to both types of contexts and disables the limits.
396 This can be used to enable or disable certain versions of the SSL,
397 TLS or DTLS protocol.
399 The B<value> argument is a comma separated list of supported protocols
400 to enable or disable.
401 If a protocol is preceded by B<-> that version is disabled.
403 All protocol versions are enabled by default.
404 You need to disable at least one protocol version for this setting have any
406 Only enabling some protocol versions does not disable the other protocol
409 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
410 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
411 The special value B<ALL> refers to all supported versions.
413 This can't enable protocols that are disabled using B<MinProtocol>
414 or B<MaxProtocol>, but can disable protocols that are still allowed
417 The B<Protocol> command is fragile and deprecated; do not use it.
418 Use B<MinProtocol> and B<MaxProtocol> instead.
419 If you do use B<Protocol>, make sure that the resulting range of enabled
420 protocols has no "holes", e.g. if TLS 1.0 and TLS 1.2 are both enabled, make
421 sure to also leave TLS 1.1 enabled.
425 The B<value> argument is a comma separated list of various flags to set.
426 If a flag string is preceded B<-> it is disabled.
427 See the L<SSL_CTX_set_options(3)> function for more details of
430 Each option is listed below. Where an operation is enabled by default
431 the B<-flag> syntax is needed to disable it.
433 B<SessionTicket>: session ticket support, enabled by default. Inverse of
434 B<SSL_OP_NO_TICKET>: that is B<-SessionTicket> is the same as setting
437 B<Compression>: SSL/TLS compression support, enabled by default. Inverse
438 of B<SSL_OP_NO_COMPRESSION>.
440 B<EmptyFragments>: use empty fragments as a countermeasure against a
441 SSL 3.0/TLS 1.0 protocol vulnerability affecting CBC ciphers. It
442 is set by default. Inverse of B<SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS>.
444 B<Bugs>: enable various bug workarounds. Same as B<SSL_OP_ALL>.
446 B<DHSingle>: enable single use DH keys, set by default. Inverse of
447 B<SSL_OP_DH_SINGLE>. Only used by servers.
449 B<ECDHSingle>: enable single use ECDH keys, set by default. Inverse of
450 B<SSL_OP_ECDH_SINGLE>. Only used by servers.
452 B<ServerPreference>: use server and not client preference order when
453 determining which cipher suite, signature algorithm or elliptic curve
454 to use for an incoming connection. Equivalent to
455 B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
457 B<PrioritizeChaCha>: prioritizes ChaCha ciphers when the client has a
458 ChaCha20 cipher at the top of its preference list. This usually indicates
459 a mobile client is in use. Equivalent to B<SSL_OP_PRIORITIZE_CHACHA>.
460 Only used by servers.
462 B<NoResumptionOnRenegotiation>: set
463 B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> flag. Only used by servers.
465 B<NoRenegotiation>: disables all attempts at renegotiation in TLSv1.2 and
466 earlier, same as setting B<SSL_OP_NO_RENEGOTIATION>.
468 B<UnsafeLegacyRenegotiation>: permits the use of unsafe legacy renegotiation.
469 Equivalent to B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
471 B<UnsafeLegacyServerConnect>: permits the use of unsafe legacy renegotiation
472 for OpenSSL clients only. Equivalent to B<SSL_OP_LEGACY_SERVER_CONNECT>.
475 B<EncryptThenMac>: use encrypt-then-mac extension, enabled by
476 default. Inverse of B<SSL_OP_NO_ENCRYPT_THEN_MAC>: that is,
477 B<-EncryptThenMac> is the same as setting B<SSL_OP_NO_ENCRYPT_THEN_MAC>.
479 B<AllowNoDHEKEX>: In TLSv1.3 allow a non-(ec)dhe based key exchange mode on
480 resumption. This means that there will be no forward secrecy for the resumed
481 session. Equivalent to B<SSL_OP_ALLOW_NO_DHE_KEX>.
483 B<MiddleboxCompat>: If set then dummy Change Cipher Spec (CCS) messages are sent
484 in TLSv1.3. This has the effect of making TLSv1.3 look more like TLSv1.2 so that
485 middleboxes that do not understand TLSv1.3 will not drop the connection. This
486 option is set by default. A future version of OpenSSL may not set this by
487 default. Equivalent to B<SSL_OP_ENABLE_MIDDLEBOX_COMPAT>.
489 B<AntiReplay>: If set then OpenSSL will automatically detect if a session ticket
490 has been used more than once, TLSv1.3 has been negotiated, and early data is
491 enabled on the server. A full handshake is forced if a session ticket is used a
492 second or subsequent time. This option is set by default and is only used by
493 servers. Anti-replay measures are required to comply with the TLSv1.3
494 specification. Some applications may be able to mitigate the replay risks in
495 other ways and in such cases the built-in OpenSSL functionality is not required.
496 Disabling anti-replay is equivalent to setting B<SSL_OP_NO_ANTI_REPLAY>.
500 The B<value> argument is a comma separated list of flags to set.
502 B<Peer> enables peer verification: for clients only.
504 B<Request> requests but does not require a certificate from the client.
507 B<Require> requests and requires a certificate from the client: an error
508 occurs if the client does not present a certificate. Servers only.
510 B<Once> requests a certificate from a client only on the initial connection:
511 not when renegotiating. Servers only.
513 B<RequestPostHandshake> configures the connection to support requests but does
514 not require a certificate from the client post-handshake. A certificate will
515 not be requested during the initial handshake. The server application must
516 provide a mechanism to request a certificate post-handshake. Servers only.
519 B<RequiresPostHandshake> configures the connection to support requests and
520 requires a certificate from the client post-handshake: an error occurs if the
521 client does not present a certificate. A certificate will not be requested
522 during the initial handshake. The server application must provide a mechanism
523 to request a certificate post-handshake. Servers only. TLSv1.3 only.
525 =item B<ClientCAFile>, B<ClientCAPath>
527 A file or directory of certificates in PEM format whose names are used as the
528 set of acceptable names for client CAs. Servers only. This option is only
529 supported if certificate operations are permitted.
533 =head1 SUPPORTED COMMAND TYPES
535 The function SSL_CONF_cmd_value_type() currently returns one of the following
540 =item B<SSL_CONF_TYPE_UNKNOWN>
542 The B<cmd> string is unrecognised, this return value can be use to flag
545 =item B<SSL_CONF_TYPE_STRING>
547 The value is a string without any specific structure.
549 =item B<SSL_CONF_TYPE_FILE>
551 The value is a filename.
553 =item B<SSL_CONF_TYPE_DIR>
555 The value is a directory name.
557 =item B<SSL_CONF_TYPE_NONE>
559 The value string is not used e.g. a command line option which doesn't take an
566 The order of operations is significant. This can be used to set either defaults
567 or values which cannot be overridden. For example if an application calls:
569 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
570 SSL_CONF_cmd(ctx, userparam, uservalue);
572 it will disable SSLv3 support by default but the user can override it. If
573 however the call sequence is:
575 SSL_CONF_cmd(ctx, userparam, uservalue);
576 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
578 SSLv3 is B<always> disabled and attempt to override this by the user are
581 By checking the return code of SSL_CONF_cmd() it is possible to query if a
582 given B<cmd> is recognised, this is useful if SSL_CONF_cmd() values are
583 mixed with additional application specific operations.
585 For example an application might call SSL_CONF_cmd() and if it returns
586 -2 (unrecognised command) continue with processing of application specific
589 Applications can also use SSL_CONF_cmd() to process command lines though the
590 utility function SSL_CONF_cmd_argv() is normally used instead. One way
591 to do this is to set the prefix to an appropriate value using
592 SSL_CONF_CTX_set1_prefix(), pass the current argument to B<cmd> and the
593 following argument to B<value> (which may be NULL).
595 In this case if the return value is positive then it is used to skip that
596 number of arguments as they have been processed by SSL_CONF_cmd(). If -2 is
597 returned then B<cmd> is not recognised and application specific arguments
598 can be checked instead. If -3 is returned a required argument is missing
599 and an error is indicated. If 0 is returned some other error occurred and
600 this can be reported back to the user.
602 The function SSL_CONF_cmd_value_type() can be used by applications to
603 check for the existence of a command or to perform additional syntax
604 checking or translation of the command value. For example if the return
605 value is B<SSL_CONF_TYPE_FILE> an application could translate a relative
606 pathname to an absolute pathname.
610 SSL_CONF_cmd() returns 1 if the value of B<cmd> is recognised and B<value> is
611 B<NOT> used and 2 if both B<cmd> and B<value> are used. In other words it
612 returns the number of arguments processed. This is useful when processing
615 A return value of -2 means B<cmd> is not recognised.
617 A return value of -3 means B<cmd> is recognised and the command requires a
618 value but B<value> is NULL.
620 A return code of 0 indicates that both B<cmd> and B<value> are valid but an
621 error occurred attempting to perform the operation: for example due to an
622 error in the syntax of B<value> in this case the error queue may provide
623 additional information.
627 Set supported signature algorithms:
629 SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256");
631 There are various ways to select the supported protocols.
633 This set the minimum protocol version to TLSv1, and so disables SSLv3.
634 This is the recommended way to disable protocols.
636 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1");
638 The following also disables SSLv3:
640 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
642 The following will first enable all protocols, and then disable
644 If no protocol versions were disabled before this has the same effect as
645 "-SSLv3", but if some versions were disables this will re-enable them before
648 SSL_CONF_cmd(ctx, "Protocol", "ALL,-SSLv3");
652 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1.2");
653 SSL_CONF_cmd(ctx, "MaxProtocol", "TLSv1.2");
655 This also only enables TLSv1.2:
657 SSL_CONF_cmd(ctx, "Protocol", "-ALL,TLSv1.2");
659 Disable TLS session tickets:
661 SSL_CONF_cmd(ctx, "Options", "-SessionTicket");
665 SSL_CONF_cmd(ctx, "Options", "Compression");
667 Set supported curves to P-256, P-384:
669 SSL_CONF_cmd(ctx, "Curves", "P-256:P-384");
673 L<SSL_CONF_CTX_new(3)>,
674 L<SSL_CONF_CTX_set_flags(3)>,
675 L<SSL_CONF_CTX_set1_prefix(3)>,
676 L<SSL_CONF_CTX_set_ssl_ctx(3)>,
677 L<SSL_CONF_cmd_argv(3)>,
678 L<SSL_CTX_set_options(3)>
682 The SSL_CONF_cmd() function was added in OpenSSL 1.0.2.
684 The B<SSL_OP_NO_SSL2> option doesn't have effect since 1.1.0, but the macro
685 is retained for backwards compatibility.
687 The B<SSL_CONF_TYPE_NONE> was added in OpenSSL 1.1.0. In earlier versions of
688 OpenSSL passing a command which didn't take an argument would return
689 B<SSL_CONF_TYPE_UNKNOWN>.
691 B<MinProtocol> and B<MaxProtocol> where added in OpenSSL 1.1.0.
693 B<AllowNoDHEKEX> and B<PrioritizeChaCha> were added in OpenSSL 1.1.1.
697 Copyright 2012-2020 The OpenSSL Project Authors. All Rights Reserved.
699 Licensed under the OpenSSL license (the "License"). You may not use
700 this file except in compliance with the License. You can obtain a copy
701 in the file LICENSE in the source distribution or at
702 L<https://www.openssl.org/source/license.html>.