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 *ctx, const char *option, const char *value);
13 int SSL_CONF_cmd_value_type(SSL_CONF_CTX *ctx, const char *option);
17 The function SSL_CONF_cmd() performs configuration operation B<option> 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<option> refers to.
24 =head1 SUPPORTED COMMAND LINE COMMANDS
26 Currently supported B<option> names for command lines (i.e. when the
27 flag B<SSL_CONF_CMDLINE> is set) are listed below. Note: all B<option> 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 Various bug workarounds are set, same as setting B<SSL_OP_ALL>.
40 Disables support for SSL/TLS compression, same as setting
41 B<SSL_OP_NO_COMPRESSION>.
42 As of OpenSSL 1.1.0, compression is off by default.
46 Enables support for SSL/TLS compression, same as clearing
47 B<SSL_OP_NO_COMPRESSION>.
48 This command was introduced in OpenSSL 1.1.0.
49 As of OpenSSL 1.1.0, compression is off by default.
53 Disables support for session tickets, same as setting B<SSL_OP_NO_TICKET>.
57 Use server and not client preference order when determining which cipher suite,
58 signature algorithm or elliptic curve to use for an incoming connection.
59 Equivalent to B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
61 =item B<-legacyrenegotiation>
63 permits the use of unsafe legacy renegotiation. Equivalent to setting
64 B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
66 =item B<-no_renegotiation>
68 Disables all attempts at renegotiation in TLSv1.2 and earlier, same as setting
69 B<SSL_OP_NO_RENEGOTIATION>.
71 =item B<-no_resumption_on_reneg>
73 set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag. Only used by servers.
75 =item B<-legacy_server_connect>, B<-no_legacy_server_connect>
77 permits or prohibits the use of unsafe legacy renegotiation for OpenSSL
78 clients only. Equivalent to setting or clearing B<SSL_OP_LEGACY_SERVER_CONNECT>.
81 =item B<-prioritize_chacha>
83 Prioritize ChaCha ciphers when the client has a ChaCha20 cipher at the top of
84 its preference list. This usually indicates a client without AES hardware
85 acceleration (e.g. mobile) is in use. Equivalent to B<SSL_OP_PRIORITIZE_CHACHA>.
86 Only used by servers. Requires B<-serverpref>.
88 =item B<-allow_no_dhe_kex>
90 In TLSv1.3 allow a non-(ec)dhe based key exchange mode on resumption. This means
91 that there will be no forward secrecy for the resumed session.
95 enables strict mode protocol handling. Equivalent to setting
96 B<SSL_CERT_FLAG_TLS_STRICT>.
98 =item B<-sigalgs> I<algs>
100 This sets the supported signature algorithms for TLSv1.2 and TLSv1.3.
101 For clients this value is used directly for the supported signature
102 algorithms extension. For servers it is used to determine which signature
103 algorithms to support.
105 The B<algs> argument should be a colon separated list of signature
106 algorithms in order of decreasing preference of the form B<algorithm+hash>
107 or B<signature_scheme>. B<algorithm> is one of B<RSA>, B<DSA> or B<ECDSA> and
108 B<hash> is a supported algorithm OID short name such as B<SHA1>, B<SHA224>,
109 B<SHA256>, B<SHA384> of B<SHA512>. Note: algorithm and hash names are case
110 sensitive. B<signature_scheme> is one of the signature schemes defined in
111 TLSv1.3, specified using the IETF name, e.g., B<ecdsa_secp256r1_sha256>,
112 B<ed25519>, or B<rsa_pss_pss_sha256>.
114 If this option is not set then all signature algorithms supported by the
115 OpenSSL library are permissible.
117 Note: algorithms which specify a PKCS#1 v1.5 signature scheme (either by
118 using B<RSA> as the B<algorithm> or by using one of the B<rsa_pkcs1_*>
119 identifiers) are ignored in TLSv1.3 and will not be negotiated.
121 =item B<-client_sigalgs> I<algs>
123 This sets the supported signature algorithms associated with client
124 authentication for TLSv1.2 and TLSv1.3. For servers the B<algs> is used
125 in the B<signature_algorithms> field of a B<CertificateRequest> message.
126 For clients it is used to determine which signature algorithm to use with
127 the client certificate. If a server does not request a certificate this
128 option has no effect.
130 The syntax of B<algs> is identical to B<-sigalgs>. If not set, then the
131 value set for B<-sigalgs> will be used instead.
133 =item B<-groups> I<groups>
135 This sets the supported groups. For clients, the groups are sent using
136 the supported groups extension. For servers, it is used to determine which
137 group to use. This setting affects groups used for signatures (in TLSv1.2
138 and earlier) and key exchange. The first group listed will also be used
139 for the B<key_share> sent by a client in a TLSv1.3 B<ClientHello>.
141 The B<groups> argument is a colon separated list of groups. The group can
142 be either the B<NIST> name (e.g. B<P-256>), some other commonly used name
143 where applicable (e.g. B<X25519>, B<ffdhe2048>) or an OpenSSL OID name
144 (e.g. B<prime256v1>). Group names are case sensitive. The list should be
145 in order of preference with the most preferred group first.
147 Currently supported groups for B<TLSv1.3> are B<P-256>, B<P-384>, B<P-521>,
148 B<X25519>, B<X448>, B<ffdhe2048>, B<ffdhe3072>, B<ffdhe4096>, B<ffdhe6144>,
151 =item B<-curves> I<groups>
153 This is a synonym for the B<-groups> command.
155 =item B<-named_curve> I<curve>
157 This sets the temporary curve used for ephemeral ECDH modes. Only used
160 The B<groups> argument is a curve name or the special value B<auto> which
161 picks an appropriate curve based on client and server preferences. The
162 curve can be either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name
163 (e.g. B<prime256v1>). Curve names are case sensitive.
165 =item B<-cipher> I<ciphers>
167 Sets the TLSv1.2 and below ciphersuite list to B<ciphers>. This list will be
168 combined with any configured TLSv1.3 ciphersuites. Note: syntax checking
169 of B<ciphers> is currently not performed unless a B<SSL> or B<SSL_CTX>
170 structure is associated with B<ctx>.
172 =item B<-ciphersuites> I<1.3ciphers>
174 Sets the available ciphersuites for TLSv1.3 to value. This is a
175 colon-separated list of TLSv1.3 ciphersuite names in order of preference. This
176 list will be combined any configured TLSv1.2 and below ciphersuites.
177 See L<openssl-ciphers(1)> for more information.
179 =item B<-min_protocol> I<minprot>, B<-max_protocol> I<maxprot>
181 Sets the minimum and maximum supported protocol.
182 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
183 B<TLSv1.2>, B<TLSv1.3> for TLS; B<DTLSv1>, B<DTLSv1.2> for DTLS, and B<None>
185 If either the lower or upper bound is not specified then only the other bound
186 applies, if specified.
187 If your application supports both TLS and DTLS you can specify any of these
188 options twice, once with a bound for TLS and again with an appropriate bound
190 To restrict the supported protocol versions use these commands rather than the
191 deprecated alternative commands below.
193 =item B<-record_padding> I<padding>
195 Attempts to pad TLSv1.3 records so that they are a multiple of B<padding>
196 in length on send. A B<padding> of 0 or 1 turns off padding. Otherwise,
197 the B<padding> must be >1 or <=16384.
199 =item B<-debug_broken_protocol>
203 =item B<-no_middlebox>
205 Turn off "middlebox compatibility", as described below.
209 =head2 Additional Options
211 The following options are accepted by SSL_CONF_cmd(), but are not
212 processed by the OpenSSL commands.
216 =item B<-cert> I<file>
218 Attempts to use B<file> as the certificate for the appropriate context. It
219 currently uses SSL_CTX_use_certificate_chain_file() if an B<SSL_CTX>
220 structure is set or SSL_use_certificate_file() with filetype PEM if an
221 B<SSL> structure is set. This option is only supported if certificate
222 operations are permitted.
224 =item B<-key> I<file>
226 Attempts to use B<file> as the private key for the appropriate context. This
227 option is only supported if certificate operations are permitted. Note:
228 if no B<-key> option is set then a private key is not loaded unless the
229 flag B<SSL_CONF_FLAG_REQUIRE_PRIVATE> is set.
231 =item B<-dhparam> I<file>
233 Attempts to use B<file> as the set of temporary DH parameters for
234 the appropriate context. This option is only supported if certificate
235 operations are permitted.
237 =item B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>, B<-no_tls1_3>
239 Disables protocol support for SSLv3, TLSv1.0, TLSv1.1, TLSv1.2 or TLSv1.3 by
240 setting the corresponding options B<SSL_OP_NO_SSLv3>, B<SSL_OP_NO_TLSv1>,
241 B<SSL_OP_NO_TLSv1_1>, B<SSL_OP_NO_TLSv1_2> and B<SSL_OP_NO_TLSv1_3>
242 respectively. These options are deprecated, use B<-min_protocol> and
243 B<-max_protocol> instead.
245 =item B<-anti_replay>, B<-no_anti_replay>
247 Switches replay protection, on or off respectively. With replay protection on,
248 OpenSSL will automatically detect if a session ticket has been used more than
249 once, TLSv1.3 has been negotiated, and early data is enabled on the server. A
250 full handshake is forced if a session ticket is used a second or subsequent
251 time. Anti-Replay is on by default unless overridden by a configuration file and
252 is only used by servers. Anti-replay measures are required for compliance with
253 the TLSv1.3 specification. Some applications may be able to mitigate the replay
254 risks in other ways and in such cases the built-in OpenSSL functionality is not
255 required. Switching off anti-replay is equivalent to B<SSL_OP_NO_ANTI_REPLAY>.
259 =head1 SUPPORTED CONFIGURATION FILE COMMANDS
261 Currently supported B<option> names for configuration files (i.e., when the
262 flag B<SSL_CONF_FLAG_FILE> is set) are listed below. All configuration file
263 B<option> names are case insensitive so B<signaturealgorithms> is recognised
264 as well as B<SignatureAlgorithms>. Unless otherwise stated the B<value> names
265 are also case insensitive.
267 Note: the command prefix (if set) alters the recognised B<option> values.
271 =item B<CipherString>
273 Sets the ciphersuite list for TLSv1.2 and below to B<value>. This list will be
274 combined with any configured TLSv1.3 ciphersuites. Note: syntax
275 checking of B<value> is currently not performed unless an B<SSL> or B<SSL_CTX>
276 structure is associated with B<ctx>.
278 =item B<Ciphersuites>
280 Sets the available ciphersuites for TLSv1.3 to B<value>. This is a
281 colon-separated list of TLSv1.3 ciphersuite names in order of preference. This
282 list will be combined any configured TLSv1.2 and below ciphersuites.
283 See L<openssl-ciphers(1)> for more information.
287 Attempts to use the file B<value> as the certificate for the appropriate
288 context. It currently uses SSL_CTX_use_certificate_chain_file() if an B<SSL_CTX>
289 structure is set or SSL_use_certificate_file() with filetype PEM if an B<SSL>
290 structure is set. This option is only supported if certificate operations
295 Attempts to use the file B<value> as the private key for the appropriate
296 context. This option is only supported if certificate operations
297 are permitted. Note: if no B<PrivateKey> option is set then a private key is
298 not loaded unless the B<SSL_CONF_FLAG_REQUIRE_PRIVATE> is set.
300 =item B<ChainCAFile>, B<ChainCAPath>, B<VerifyCAFile>, B<VerifyCAPath>
302 These options indicate a file or directory used for building certificate
303 chains or verifying certificate chains. These options are only supported
304 if certificate operations are permitted.
306 =item B<RequestCAFile>
308 This option indicates a file containing a set of certificates in PEM form.
309 The subject names of the certificates are sent to the peer in the
310 B<certificate_authorities> extension for TLS 1.3 (in ClientHello or
311 CertificateRequest) or in a certificate request for previous versions or
314 =item B<ServerInfoFile>
316 Attempts to use the file B<value> in the "serverinfo" extension using the
317 function SSL_CTX_use_serverinfo_file.
319 =item B<DHParameters>
321 Attempts to use the file B<value> as the set of temporary DH parameters for
322 the appropriate context. This option is only supported if certificate
323 operations are permitted.
325 =item B<RecordPadding>
327 Attempts to pad TLSv1.3 records so that they are a multiple of B<value> in
328 length on send. A B<value> of 0 or 1 turns off padding. Otherwise, the
329 B<value> must be >1 or <=16384.
331 =item B<SignatureAlgorithms>
333 This sets the supported signature algorithms for TLSv1.2 and TLSv1.3.
335 value is used directly for the supported signature algorithms extension. For
336 servers it is used to determine which signature algorithms to support.
338 The B<value> argument should be a colon separated list of signature algorithms
339 in order of decreasing preference of the form B<algorithm+hash> or
340 B<signature_scheme>. B<algorithm>
341 is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
342 OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
343 Note: algorithm and hash names are case sensitive.
344 B<signature_scheme> is one of the signature schemes defined in TLSv1.3,
345 specified using the IETF name, e.g., B<ecdsa_secp256r1_sha256>, B<ed25519>,
346 or B<rsa_pss_pss_sha256>.
348 If this option is not set then all signature algorithms supported by the
349 OpenSSL library are permissible.
351 Note: algorithms which specify a PKCS#1 v1.5 signature scheme (either by
352 using B<RSA> as the B<algorithm> or by using one of the B<rsa_pkcs1_*>
353 identifiers) are ignored in TLSv1.3 and will not be negotiated.
355 =item B<ClientSignatureAlgorithms>
357 This sets the supported signature algorithms associated with client
358 authentication for TLSv1.2 and TLSv1.3.
359 For servers the value is used in the
360 B<signature_algorithms> field of a B<CertificateRequest> message.
362 used to determine which signature algorithm to use with the client certificate.
363 If a server does not request a certificate this option has no effect.
365 The syntax of B<value> is identical to B<SignatureAlgorithms>. If not set then
366 the value set for B<SignatureAlgorithms> will be used instead.
370 This sets the supported groups. For clients, the groups are
371 sent using the supported groups extension. For servers, it is used
372 to determine which group to use. This setting affects groups used for
373 signatures (in TLSv1.2 and earlier) and key exchange. The first group listed
374 will also be used for the B<key_share> sent by a client in a TLSv1.3
377 The B<value> argument is a colon separated list of groups. The group can be
378 either the B<NIST> name (e.g. B<P-256>), some other commonly used name where
379 applicable (e.g. B<X25519>, B<ffdhe2048>) or an OpenSSL OID name
380 (e.g. B<prime256v1>). Group names are case sensitive. The list should be in
381 order of preference with the most preferred group first.
383 Currently supported groups for B<TLSv1.3> are B<P-256>, B<P-384>, B<P-521>,
384 B<X25519>, B<X448>, B<ffdhe2048>, B<ffdhe3072>, B<ffdhe4096>, B<ffdhe6144>,
389 This is a synonym for the "Groups" command.
393 This sets the minimum supported SSL, TLS or DTLS version.
395 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
396 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
397 The SSL and TLS bounds apply only to TLS-based contexts, while the DTLS bounds
398 apply only to DTLS-based contexts.
399 The command can be repeated with one instance setting a TLS bound, and the
400 other setting a DTLS bound.
401 The value B<None> applies to both types of contexts and disables the limits.
405 This sets the maximum supported SSL, TLS or DTLS version.
407 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
408 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
409 The SSL and TLS bounds apply only to TLS-based contexts, while the DTLS bounds
410 apply only to DTLS-based contexts.
411 The command can be repeated with one instance setting a TLS bound, and the
412 other setting a DTLS bound.
413 The value B<None> applies to both types of contexts and disables the limits.
417 This can be used to enable or disable certain versions of the SSL,
418 TLS or DTLS protocol.
420 The B<value> argument is a comma separated list of supported protocols
421 to enable or disable.
422 If a protocol is preceded by B<-> that version is disabled.
424 All protocol versions are enabled by default.
425 You need to disable at least one protocol version for this setting have any
427 Only enabling some protocol versions does not disable the other protocol
430 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
431 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
432 The special value B<ALL> refers to all supported versions.
434 This can't enable protocols that are disabled using B<MinProtocol>
435 or B<MaxProtocol>, but can disable protocols that are still allowed
438 The B<Protocol> command is fragile and deprecated; do not use it.
439 Use B<MinProtocol> and B<MaxProtocol> instead.
440 If you do use B<Protocol>, make sure that the resulting range of enabled
441 protocols has no "holes", e.g. if TLS 1.0 and TLS 1.2 are both enabled, make
442 sure to also leave TLS 1.1 enabled.
446 The B<value> argument is a comma separated list of various flags to set.
447 If a flag string is preceded B<-> it is disabled.
448 See the L<SSL_CTX_set_options(3)> function for more details of
451 Each option is listed below. Where an operation is enabled by default
452 the B<-flag> syntax is needed to disable it.
454 B<SessionTicket>: session ticket support, enabled by default. Inverse of
455 B<SSL_OP_NO_TICKET>: that is B<-SessionTicket> is the same as setting
458 B<Compression>: SSL/TLS compression support, enabled by default. Inverse
459 of B<SSL_OP_NO_COMPRESSION>.
461 B<EmptyFragments>: use empty fragments as a countermeasure against a
462 SSL 3.0/TLS 1.0 protocol vulnerability affecting CBC ciphers. It
463 is set by default. Inverse of B<SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS>.
465 B<Bugs>: enable various bug workarounds. Same as B<SSL_OP_ALL>.
467 B<DHSingle>: enable single use DH keys, set by default. Inverse of
468 B<SSL_OP_DH_SINGLE>. Only used by servers.
470 B<ECDHSingle>: enable single use ECDH keys, set by default. Inverse of
471 B<SSL_OP_ECDH_SINGLE>. Only used by servers.
473 B<ServerPreference>: use server and not client preference order when
474 determining which cipher suite, signature algorithm or elliptic curve
475 to use for an incoming connection. Equivalent to
476 B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
478 B<PrioritizeChaCha>: prioritizes ChaCha ciphers when the client has a
479 ChaCha20 cipher at the top of its preference list. This usually indicates
480 a mobile client is in use. Equivalent to B<SSL_OP_PRIORITIZE_CHACHA>.
481 Only used by servers.
483 B<NoResumptionOnRenegotiation>: set
484 B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> flag. Only used by servers.
486 B<NoRenegotiation>: disables all attempts at renegotiation in TLSv1.2 and
487 earlier, same as setting B<SSL_OP_NO_RENEGOTIATION>.
489 B<UnsafeLegacyRenegotiation>: permits the use of unsafe legacy renegotiation.
490 Equivalent to B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
492 B<UnsafeLegacyServerConnect>: permits the use of unsafe legacy renegotiation
493 for OpenSSL clients only. Equivalent to B<SSL_OP_LEGACY_SERVER_CONNECT>.
496 B<EncryptThenMac>: use encrypt-then-mac extension, enabled by
497 default. Inverse of B<SSL_OP_NO_ENCRYPT_THEN_MAC>: that is,
498 B<-EncryptThenMac> is the same as setting B<SSL_OP_NO_ENCRYPT_THEN_MAC>.
500 B<AllowNoDHEKEX>: In TLSv1.3 allow a non-(ec)dhe based key exchange mode on
501 resumption. This means that there will be no forward secrecy for the resumed
502 session. Equivalent to B<SSL_OP_ALLOW_NO_DHE_KEX>.
504 B<MiddleboxCompat>: If set then dummy Change Cipher Spec (CCS) messages are sent
505 in TLSv1.3. This has the effect of making TLSv1.3 look more like TLSv1.2 so that
506 middleboxes that do not understand TLSv1.3 will not drop the connection. This
507 option is set by default. A future version of OpenSSL may not set this by
508 default. Equivalent to B<SSL_OP_ENABLE_MIDDLEBOX_COMPAT>.
510 B<AntiReplay>: If set then OpenSSL will automatically detect if a session ticket
511 has been used more than once, TLSv1.3 has been negotiated, and early data is
512 enabled on the server. A full handshake is forced if a session ticket is used a
513 second or subsequent time. This option is set by default and is only used by
514 servers. Anti-replay measures are required to comply with the TLSv1.3
515 specification. Some applications may be able to mitigate the replay risks in
516 other ways and in such cases the built-in OpenSSL functionality is not required.
517 Disabling anti-replay is equivalent to setting B<SSL_OP_NO_ANTI_REPLAY>.
519 B<ExtendedMasterSecret>: use extended master secret extension, enabled by
520 default. Inverse of B<SSL_OP_NO_EXTENDED_MASTER_SECRET>: that is,
521 B<-ExtendedMasterSecret> is the same as setting B<SSL_OP_NO_EXTENDED_MASTER_SECRET>.
523 B<CANames>: use CA names extension, enabled by
524 default. Inverse of B<SSL_OP_DISABLE_TLSEXT_CA_NAMES>: that is,
525 B<-CANames> is the same as setting B<SSL_OP_DISABLE_TLSEXT_CA_NAMES>.
527 B<KTLS>: Enables kernel TLS if support has been compiled in, and it is supported
528 by the negotiated ciphersuites and extensions. Equivalent to
529 B<SSL_OP_ENABLE_KTLS>.
533 The B<value> argument is a comma separated list of flags to set.
535 B<Peer> enables peer verification: for clients only.
537 B<Request> requests but does not require a certificate from the client.
540 B<Require> requests and requires a certificate from the client: an error
541 occurs if the client does not present a certificate. Servers only.
543 B<Once> requests a certificate from a client only on the initial connection:
544 not when renegotiating. Servers only.
546 B<RequestPostHandshake> configures the connection to support requests but does
547 not require a certificate from the client post-handshake. A certificate will
548 not be requested during the initial handshake. The server application must
549 provide a mechanism to request a certificate post-handshake. Servers only.
552 B<RequiresPostHandshake> configures the connection to support requests and
553 requires a certificate from the client post-handshake: an error occurs if the
554 client does not present a certificate. A certificate will not be requested
555 during the initial handshake. The server application must provide a mechanism
556 to request a certificate post-handshake. Servers only. TLSv1.3 only.
558 =item B<ClientCAFile>, B<ClientCAPath>
560 A file or directory of certificates in PEM format whose names are used as the
561 set of acceptable names for client CAs. Servers only. This option is only
562 supported if certificate operations are permitted.
566 =head1 SUPPORTED COMMAND TYPES
568 The function SSL_CONF_cmd_value_type() currently returns one of the following
573 =item B<SSL_CONF_TYPE_UNKNOWN>
575 The B<option> string is unrecognised, this return value can be use to flag
578 =item B<SSL_CONF_TYPE_STRING>
580 The value is a string without any specific structure.
582 =item B<SSL_CONF_TYPE_FILE>
584 The value is a filename.
586 =item B<SSL_CONF_TYPE_DIR>
588 The value is a directory name.
590 =item B<SSL_CONF_TYPE_NONE>
592 The value string is not used e.g. a command line option which doesn't take an
599 The order of operations is significant. This can be used to set either defaults
600 or values which cannot be overridden. For example if an application calls:
602 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
603 SSL_CONF_cmd(ctx, userparam, uservalue);
605 it will disable SSLv3 support by default but the user can override it. If
606 however the call sequence is:
608 SSL_CONF_cmd(ctx, userparam, uservalue);
609 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
611 SSLv3 is B<always> disabled and attempt to override this by the user are
614 By checking the return code of SSL_CONF_cmd() it is possible to query if a
615 given B<option> is recognised, this is useful if SSL_CONF_cmd() values are
616 mixed with additional application specific operations.
618 For example an application might call SSL_CONF_cmd() and if it returns
619 -2 (unrecognised command) continue with processing of application specific
622 Applications can also use SSL_CONF_cmd() to process command lines though the
623 utility function SSL_CONF_cmd_argv() is normally used instead. One way
624 to do this is to set the prefix to an appropriate value using
625 SSL_CONF_CTX_set1_prefix(), pass the current argument to B<option> and the
626 following argument to B<value> (which may be NULL).
628 In this case if the return value is positive then it is used to skip that
629 number of arguments as they have been processed by SSL_CONF_cmd(). If -2 is
630 returned then B<option> is not recognised and application specific arguments
631 can be checked instead. If -3 is returned a required argument is missing
632 and an error is indicated. If 0 is returned some other error occurred and
633 this can be reported back to the user.
635 The function SSL_CONF_cmd_value_type() can be used by applications to
636 check for the existence of a command or to perform additional syntax
637 checking or translation of the command value. For example if the return
638 value is B<SSL_CONF_TYPE_FILE> an application could translate a relative
639 pathname to an absolute pathname.
643 SSL_CONF_cmd() returns 1 if the value of B<option> is recognised and B<value> is
644 B<NOT> used and 2 if both B<option> and B<value> are used. In other words it
645 returns the number of arguments processed. This is useful when processing
648 A return value of -2 means B<option> is not recognised.
650 A return value of -3 means B<option> is recognised and the command requires a
651 value but B<value> is NULL.
653 A return code of 0 indicates that both B<option> and B<value> are valid but an
654 error occurred attempting to perform the operation: for example due to an
655 error in the syntax of B<value> in this case the error queue may provide
656 additional information.
660 Set supported signature algorithms:
662 SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256");
664 There are various ways to select the supported protocols.
666 This set the minimum protocol version to TLSv1, and so disables SSLv3.
667 This is the recommended way to disable protocols.
669 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1");
671 The following also disables SSLv3:
673 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
675 The following will first enable all protocols, and then disable
677 If no protocol versions were disabled before this has the same effect as
678 "-SSLv3", but if some versions were disables this will re-enable them before
681 SSL_CONF_cmd(ctx, "Protocol", "ALL,-SSLv3");
685 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1.2");
686 SSL_CONF_cmd(ctx, "MaxProtocol", "TLSv1.2");
688 This also only enables TLSv1.2:
690 SSL_CONF_cmd(ctx, "Protocol", "-ALL,TLSv1.2");
692 Disable TLS session tickets:
694 SSL_CONF_cmd(ctx, "Options", "-SessionTicket");
698 SSL_CONF_cmd(ctx, "Options", "Compression");
700 Set supported curves to P-256, P-384:
702 SSL_CONF_cmd(ctx, "Curves", "P-256:P-384");
707 L<SSL_CONF_CTX_new(3)>,
708 L<SSL_CONF_CTX_set_flags(3)>,
709 L<SSL_CONF_CTX_set1_prefix(3)>,
710 L<SSL_CONF_CTX_set_ssl_ctx(3)>,
711 L<SSL_CONF_cmd_argv(3)>,
712 L<SSL_CTX_set_options(3)>
716 The SSL_CONF_cmd() function was added in OpenSSL 1.0.2.
718 The B<SSL_OP_NO_SSL2> option doesn't have effect since 1.1.0, but the macro
719 is retained for backwards compatibility.
721 The B<SSL_CONF_TYPE_NONE> was added in OpenSSL 1.1.0. In earlier versions of
722 OpenSSL passing a command which didn't take an argument would return
723 B<SSL_CONF_TYPE_UNKNOWN>.
725 B<MinProtocol> and B<MaxProtocol> where added in OpenSSL 1.1.0.
727 B<AllowNoDHEKEX> and B<PrioritizeChaCha> were added in OpenSSL 1.1.1.
731 Copyright 2012-2020 The OpenSSL Project Authors. All Rights Reserved.
733 Licensed under the Apache License 2.0 (the "License"). You may not use
734 this file except in compliance with the License. You can obtain a copy
735 in the file LICENSE in the source distribution or at
736 L<https://www.openssl.org/source/license.html>.