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>.
80 =item B<-prioritize_chacha>
82 Prioritize ChaCha ciphers when the client has a ChaCha20 cipher at the top of
83 its preference list. This usually indicates a client without AES hardware
84 acceleration (e.g. mobile) is in use. Equivalent to B<SSL_OP_PRIORITIZE_CHACHA>.
85 Only used by servers. Requires B<-serverpref>.
87 =item B<-allow_no_dhe_kex>
89 In TLSv1.3 allow a non-(ec)dhe based key exchange mode on resumption. This means
90 that there will be no forward secrecy for the resumed session.
94 enables strict mode protocol handling. Equivalent to setting
95 B<SSL_CERT_FLAG_TLS_STRICT>.
97 =item B<-sigalgs> I<algs>
99 This sets the supported signature algorithms for TLSv1.2 and TLSv1.3.
100 For clients this value is used directly for the supported signature
101 algorithms extension. For servers it is used to determine which signature
102 algorithms to support.
104 The B<algs> argument should be a colon separated list of signature
105 algorithms in order of decreasing preference of the form B<algorithm+hash>
106 or B<signature_scheme>. B<algorithm> is one of B<RSA>, B<DSA> or B<ECDSA> and
107 B<hash> is a supported algorithm OID short name such as B<SHA1>, B<SHA224>,
108 B<SHA256>, B<SHA384> of B<SHA512>. Note: algorithm and hash names are case
109 sensitive. B<signature_scheme> is one of the signature schemes defined in
110 TLSv1.3, specified using the IETF name, e.g., B<ecdsa_secp256r1_sha256>,
111 B<ed25519>, or B<rsa_pss_pss_sha256>.
113 If this option is not set then all signature algorithms supported by the
114 OpenSSL library are permissible.
116 Note: algorithms which specify a PKCS#1 v1.5 signature scheme (either by
117 using B<RSA> as the B<algorithm> or by using one of the B<rsa_pkcs1_*>
118 identifiers) are ignored in TLSv1.3 and will not be negotiated.
120 =item B<-client_sigalgs> I<algs>
122 This sets the supported signature algorithms associated with client
123 authentication for TLSv1.2 and TLSv1.3. For servers the B<algs> is used
124 in the B<signature_algorithms> field of a B<CertificateRequest> message.
125 For clients it is used to determine which signature algorithm to use with
126 the client certificate. If a server does not request a certificate this
127 option has no effect.
129 The syntax of B<algs> is identical to B<-sigalgs>. If not set, then the
130 value set for B<-sigalgs> will be used instead.
132 =item B<-groups> I<groups>
134 This sets the supported groups. For clients, the groups are sent using
135 the supported groups extension. For servers, it is used to determine which
136 group to use. This setting affects groups used for signatures (in TLSv1.2
137 and earlier) and key exchange. The first group listed will also be used
138 for the B<key_share> sent by a client in a TLSv1.3 B<ClientHello>.
140 The B<groups> argument is a colon separated list of groups. The group can
141 be either the B<NIST> name (e.g. B<P-256>), some other commonly used name
142 where applicable (e.g. B<X25519>, B<ffdhe2048>) or an OpenSSL OID name
143 (e.g. B<prime256v1>). Group names are case sensitive. The list should be
144 in order of preference with the most preferred group first.
146 Currently supported groups for B<TLSv1.3> are B<P-256>, B<P-384>, B<P-521>,
147 B<X25519>, B<X448>, B<ffdhe2048>, B<ffdhe3072>, B<ffdhe4096>, B<ffdhe6144>,
150 =item B<-curves> I<groups>
152 This is a synonym for the B<-groups> command.
154 =item B<-named_curve> I<curve>
156 This sets the temporary curve used for ephemeral ECDH modes. Only used
159 The B<groups> argument is a curve name or the special value B<auto> which
160 picks an appropriate curve based on client and server preferences. The
161 curve can be either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name
162 (e.g. B<prime256v1>). Curve names are case sensitive.
164 =item B<-cipher> I<ciphers>
166 Sets the TLSv1.2 and below ciphersuite list to B<ciphers>. This list will be
167 combined with any configured TLSv1.3 ciphersuites. Note: syntax checking
168 of B<ciphers> is currently not performed unless a B<SSL> or B<SSL_CTX>
169 structure is associated with B<ctx>.
171 =item B<-ciphersuites> I<1.3ciphers>
173 Sets the available ciphersuites for TLSv1.3 to value. This is a
174 colon-separated list of TLSv1.3 ciphersuite names in order of preference. This
175 list will be combined any configured TLSv1.2 and below ciphersuites.
176 See L<openssl-ciphers(1)> for more information.
178 =item B<-min_protocol> I<minprot>, B<-max_protocol> I<maxprot>
180 Sets the minimum and maximum supported protocol.
181 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
182 B<TLSv1.2>, B<TLSv1.3> for TLS; B<DTLSv1>, B<DTLSv1.2> for DTLS, and B<None>
184 If either the lower or upper bound is not specified then only the other bound
185 applies, if specified.
186 If your application supports both TLS and DTLS you can specify any of these
187 options twice, once with a bound for TLS and again with an appropriate bound
189 To restrict the supported protocol versions use these commands rather than the
190 deprecated alternative commands below.
192 =item B<-record_padding> I<padding>
194 Attempts to pad TLSv1.3 records so that they are a multiple of B<padding>
195 in length on send. A B<padding> of 0 or 1 turns off padding. Otherwise,
196 the B<padding> must be >1 or <=16384.
198 =item B<-debug_broken_protocol>
202 =item B<-no_middlebox>
204 Turn off "middlebox compatibility", as described below.
208 =head2 Additional Options
210 The following options are accepted by SSL_CONF_cmd(), but are not
211 processed by the OpenSSL commands.
215 =item B<-cert> I<file>
217 Attempts to use B<file> as the certificate for the appropriate context. It
218 currently uses SSL_CTX_use_certificate_chain_file() if an B<SSL_CTX>
219 structure is set or SSL_use_certificate_file() with filetype PEM if an
220 B<SSL> structure is set. This option is only supported if certificate
221 operations are permitted.
223 =item B<-key> I<file>
225 Attempts to use B<file> as the private key for the appropriate context. This
226 option is only supported if certificate operations are permitted. Note:
227 if no B<-key> option is set then a private key is not loaded unless the
228 flag B<SSL_CONF_FLAG_REQUIRE_PRIVATE> is set.
230 =item B<-dhparam> I<file>
232 Attempts to use B<file> as the set of temporary DH parameters for
233 the appropriate context. This option is only supported if certificate
234 operations are permitted.
236 =item B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>, B<-no_tls1_3>
238 Disables protocol support for SSLv3, TLSv1.0, TLSv1.1, TLSv1.2 or TLSv1.3 by
239 setting the corresponding options B<SSL_OP_NO_SSLv3>, B<SSL_OP_NO_TLSv1>,
240 B<SSL_OP_NO_TLSv1_1>, B<SSL_OP_NO_TLSv1_2> and B<SSL_OP_NO_TLSv1_3>
241 respectively. These options are deprecated, use B<-min_protocol> and
242 B<-max_protocol> instead.
244 =item B<-anti_replay>, B<-no_anti_replay>
246 Switches replay protection, on or off respectively. With replay protection on,
247 OpenSSL will automatically detect if a session ticket has been used more than
248 once, TLSv1.3 has been negotiated, and early data is enabled on the server. A
249 full handshake is forced if a session ticket is used a second or subsequent
250 time. Anti-Replay is on by default unless overridden by a configuration file and
251 is only used by servers. Anti-replay measures are required for compliance with
252 the TLSv1.3 specification. Some applications may be able to mitigate the replay
253 risks in other ways and in such cases the built-in OpenSSL functionality is not
254 required. Switching off anti-replay is equivalent to B<SSL_OP_NO_ANTI_REPLAY>.
258 =head1 SUPPORTED CONFIGURATION FILE COMMANDS
260 Currently supported B<option> names for configuration files (i.e., when the
261 flag B<SSL_CONF_FLAG_FILE> is set) are listed below. All configuration file
262 B<option> names are case insensitive so B<signaturealgorithms> is recognised
263 as well as B<SignatureAlgorithms>. Unless otherwise stated the B<value> names
264 are also case insensitive.
266 Note: the command prefix (if set) alters the recognised B<option> values.
270 =item B<CipherString>
272 Sets the ciphersuite list for TLSv1.2 and below to B<value>. This list will be
273 combined with any configured TLSv1.3 ciphersuites. Note: syntax
274 checking of B<value> is currently not performed unless an B<SSL> or B<SSL_CTX>
275 structure is associated with B<ctx>.
277 =item B<Ciphersuites>
279 Sets the available ciphersuites for TLSv1.3 to B<value>. This is a
280 colon-separated list of TLSv1.3 ciphersuite names in order of preference. This
281 list will be combined any configured TLSv1.2 and below ciphersuites.
282 See L<openssl-ciphers(1)> for more information.
286 Attempts to use the file B<value> as the certificate for the appropriate
287 context. It currently uses SSL_CTX_use_certificate_chain_file() if an B<SSL_CTX>
288 structure is set or SSL_use_certificate_file() with filetype PEM if an B<SSL>
289 structure is set. This option is only supported if certificate operations
294 Attempts to use the file B<value> as the private key for the appropriate
295 context. This option is only supported if certificate operations
296 are permitted. Note: if no B<PrivateKey> option is set then a private key is
297 not loaded unless the B<SSL_CONF_FLAG_REQUIRE_PRIVATE> is set.
299 =item B<ChainCAFile>, B<ChainCAPath>, B<VerifyCAFile>, B<VerifyCAPath>
301 These options indicate a file or directory used for building certificate
302 chains or verifying certificate chains. These options are only supported
303 if certificate operations are permitted.
305 =item B<RequestCAFile>
307 This option indicates a file containing a set of certificates in PEM form.
308 The subject names of the certificates are sent to the peer in the
309 B<certificate_authorities> extension for TLS 1.3 (in ClientHello or
310 CertificateRequest) or in a certificate request for previous versions or
313 =item B<ServerInfoFile>
315 Attempts to use the file B<value> in the "serverinfo" extension using the
316 function SSL_CTX_use_serverinfo_file.
318 =item B<DHParameters>
320 Attempts to use the file B<value> as the set of temporary DH parameters for
321 the appropriate context. This option is only supported if certificate
322 operations are permitted.
324 =item B<RecordPadding>
326 Attempts to pad TLSv1.3 records so that they are a multiple of B<value> in
327 length on send. A B<value> of 0 or 1 turns off padding. Otherwise, the
328 B<value> must be >1 or <=16384.
330 =item B<SignatureAlgorithms>
332 This sets the supported signature algorithms for TLSv1.2 and TLSv1.3.
334 value is used directly for the supported signature algorithms extension. For
335 servers it is used to determine which signature algorithms to support.
337 The B<value> argument should be a colon separated list of signature algorithms
338 in order of decreasing preference of the form B<algorithm+hash> or
339 B<signature_scheme>. B<algorithm>
340 is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
341 OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
342 Note: algorithm and hash names are case sensitive.
343 B<signature_scheme> is one of the signature schemes defined in TLSv1.3,
344 specified using the IETF name, e.g., B<ecdsa_secp256r1_sha256>, B<ed25519>,
345 or B<rsa_pss_pss_sha256>.
347 If this option is not set then all signature algorithms supported by the
348 OpenSSL library are permissible.
350 Note: algorithms which specify a PKCS#1 v1.5 signature scheme (either by
351 using B<RSA> as the B<algorithm> or by using one of the B<rsa_pkcs1_*>
352 identifiers) are ignored in TLSv1.3 and will not be negotiated.
354 =item B<ClientSignatureAlgorithms>
356 This sets the supported signature algorithms associated with client
357 authentication for TLSv1.2 and TLSv1.3.
358 For servers the value is used in the
359 B<signature_algorithms> field of a B<CertificateRequest> message.
361 used to determine which signature algorithm to use with the client certificate.
362 If a server does not request a certificate this option has no effect.
364 The syntax of B<value> is identical to B<SignatureAlgorithms>. If not set then
365 the value set for B<SignatureAlgorithms> will be used instead.
369 This sets the supported groups. For clients, the groups are
370 sent using the supported groups extension. For servers, it is used
371 to determine which group to use. This setting affects groups used for
372 signatures (in TLSv1.2 and earlier) and key exchange. The first group listed
373 will also be used for the B<key_share> sent by a client in a TLSv1.3
376 The B<value> argument is a colon separated list of groups. The group can be
377 either the B<NIST> name (e.g. B<P-256>), some other commonly used name where
378 applicable (e.g. B<X25519>, B<ffdhe2048>) or an OpenSSL OID name
379 (e.g. B<prime256v1>). Group names are case sensitive. The list should be in
380 order of preference with the most preferred group first.
382 Currently supported groups for B<TLSv1.3> are B<P-256>, B<P-384>, B<P-521>,
383 B<X25519>, B<X448>, B<ffdhe2048>, B<ffdhe3072>, B<ffdhe4096>, B<ffdhe6144>,
388 This is a synonym for the "Groups" command.
392 This sets the minimum supported SSL, TLS or DTLS version.
394 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
395 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
396 The SSL and TLS bounds apply only to TLS-based contexts, while the DTLS bounds
397 apply only to DTLS-based contexts.
398 The command can be repeated with one instance setting a TLS bound, and the
399 other setting a DTLS bound.
400 The value B<None> applies to both types of contexts and disables the limits.
404 This sets the maximum supported SSL, TLS or DTLS version.
406 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
407 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
408 The SSL and TLS bounds apply only to TLS-based contexts, while the DTLS bounds
409 apply only to DTLS-based contexts.
410 The command can be repeated with one instance setting a TLS bound, and the
411 other setting a DTLS bound.
412 The value B<None> applies to both types of contexts and disables the limits.
416 This can be used to enable or disable certain versions of the SSL,
417 TLS or DTLS protocol.
419 The B<value> argument is a comma separated list of supported protocols
420 to enable or disable.
421 If a protocol is preceded by B<-> that version is disabled.
423 All protocol versions are enabled by default.
424 You need to disable at least one protocol version for this setting have any
426 Only enabling some protocol versions does not disable the other protocol
429 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
430 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
431 The special value B<ALL> refers to all supported versions.
433 This can't enable protocols that are disabled using B<MinProtocol>
434 or B<MaxProtocol>, but can disable protocols that are still allowed
437 The B<Protocol> command is fragile and deprecated; do not use it.
438 Use B<MinProtocol> and B<MaxProtocol> instead.
439 If you do use B<Protocol>, make sure that the resulting range of enabled
440 protocols has no "holes", e.g. if TLS 1.0 and TLS 1.2 are both enabled, make
441 sure to also leave TLS 1.1 enabled.
445 The B<value> argument is a comma separated list of various flags to set.
446 If a flag string is preceded B<-> it is disabled.
447 See the L<SSL_CTX_set_options(3)> function for more details of
450 Each option is listed below. Where an operation is enabled by default
451 the B<-flag> syntax is needed to disable it.
453 B<SessionTicket>: session ticket support, enabled by default. Inverse of
454 B<SSL_OP_NO_TICKET>: that is B<-SessionTicket> is the same as setting
457 B<Compression>: SSL/TLS compression support, enabled by default. Inverse
458 of B<SSL_OP_NO_COMPRESSION>.
460 B<EmptyFragments>: use empty fragments as a countermeasure against a
461 SSL 3.0/TLS 1.0 protocol vulnerability affecting CBC ciphers. It
462 is set by default. Inverse of B<SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS>.
464 B<Bugs>: enable various bug workarounds. Same as B<SSL_OP_ALL>.
466 B<DHSingle>: enable single use DH keys, set by default. Inverse of
467 B<SSL_OP_DH_SINGLE>. Only used by servers.
469 B<ECDHSingle>: enable single use ECDH keys, set by default. Inverse of
470 B<SSL_OP_ECDH_SINGLE>. Only used by servers.
472 B<ServerPreference>: use server and not client preference order when
473 determining which cipher suite, signature algorithm or elliptic curve
474 to use for an incoming connection. Equivalent to
475 B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
477 B<PrioritizeChaCha>: prioritizes ChaCha ciphers when the client has a
478 ChaCha20 cipher at the top of its preference list. This usually indicates
479 a mobile client is in use. Equivalent to B<SSL_OP_PRIORITIZE_CHACHA>.
480 Only used by servers.
482 B<NoResumptionOnRenegotiation>: set
483 B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> flag. Only used by servers.
485 B<NoRenegotiation>: disables all attempts at renegotiation in TLSv1.2 and
486 earlier, same as setting B<SSL_OP_NO_RENEGOTIATION>.
488 B<UnsafeLegacyRenegotiation>: permits the use of unsafe legacy renegotiation.
489 Equivalent to B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
491 B<UnsafeLegacyServerConnect>: permits the use of unsafe legacy renegotiation
492 for OpenSSL clients only. Equivalent to B<SSL_OP_LEGACY_SERVER_CONNECT>.
495 B<EncryptThenMac>: use encrypt-then-mac extension, enabled by
496 default. Inverse of B<SSL_OP_NO_ENCRYPT_THEN_MAC>: that is,
497 B<-EncryptThenMac> is the same as setting B<SSL_OP_NO_ENCRYPT_THEN_MAC>.
499 B<AllowNoDHEKEX>: In TLSv1.3 allow a non-(ec)dhe based key exchange mode on
500 resumption. This means that there will be no forward secrecy for the resumed
501 session. Equivalent to B<SSL_OP_ALLOW_NO_DHE_KEX>.
503 B<MiddleboxCompat>: If set then dummy Change Cipher Spec (CCS) messages are sent
504 in TLSv1.3. This has the effect of making TLSv1.3 look more like TLSv1.2 so that
505 middleboxes that do not understand TLSv1.3 will not drop the connection. This
506 option is set by default. A future version of OpenSSL may not set this by
507 default. Equivalent to B<SSL_OP_ENABLE_MIDDLEBOX_COMPAT>.
509 B<AntiReplay>: If set then OpenSSL will automatically detect if a session ticket
510 has been used more than once, TLSv1.3 has been negotiated, and early data is
511 enabled on the server. A full handshake is forced if a session ticket is used a
512 second or subsequent time. This option is set by default and is only used by
513 servers. Anti-replay measures are required to comply with the TLSv1.3
514 specification. Some applications may be able to mitigate the replay risks in
515 other ways and in such cases the built-in OpenSSL functionality is not required.
516 Disabling anti-replay is equivalent to setting B<SSL_OP_NO_ANTI_REPLAY>.
518 B<ExtendedMasterSecret>: use extended master secret extension, enabled by
519 default. Inverse of B<SSL_OP_NO_EXTENDED_MASTER_SECRET>: that is,
520 B<-ExtendedMasterSecret> is the same as setting B<SSL_OP_NO_EXTENDED_MASTER_SECRET>.
522 B<CANames>: use CA names extension, enabled by
523 default. Inverse of B<SSL_OP_DISABLE_TLSEXT_CA_NAMES>: that is,
524 B<-CANames> is the same as setting B<SSL_OP_DISABLE_TLSEXT_CA_NAMES>.
526 B<KTLS>: Enables kernel TLS if support has been compiled in, and it is supported
527 by the negotiated ciphersuites and extensions. Equivalent to
528 B<SSL_OP_ENABLE_KTLS>.
532 The B<value> argument is a comma separated list of flags to set.
534 B<Peer> enables peer verification: for clients only.
536 B<Request> requests but does not require a certificate from the client.
539 B<Require> requests and requires a certificate from the client: an error
540 occurs if the client does not present a certificate. Servers only.
542 B<Once> requests a certificate from a client only on the initial connection:
543 not when renegotiating. Servers only.
545 B<RequestPostHandshake> configures the connection to support requests but does
546 not require a certificate from the client post-handshake. A certificate will
547 not be requested during the initial handshake. The server application must
548 provide a mechanism to request a certificate post-handshake. Servers only.
551 B<RequiresPostHandshake> configures the connection to support requests and
552 requires a certificate from the client post-handshake: an error occurs if the
553 client does not present a certificate. A certificate will not be requested
554 during the initial handshake. The server application must provide a mechanism
555 to request a certificate post-handshake. Servers only. TLSv1.3 only.
557 =item B<ClientCAFile>, B<ClientCAPath>
559 A file or directory of certificates in PEM format whose names are used as the
560 set of acceptable names for client CAs. Servers only. This option is only
561 supported if certificate operations are permitted.
565 =head1 SUPPORTED COMMAND TYPES
567 The function SSL_CONF_cmd_value_type() currently returns one of the following
572 =item B<SSL_CONF_TYPE_UNKNOWN>
574 The B<option> string is unrecognised, this return value can be use to flag
577 =item B<SSL_CONF_TYPE_STRING>
579 The value is a string without any specific structure.
581 =item B<SSL_CONF_TYPE_FILE>
583 The value is a filename.
585 =item B<SSL_CONF_TYPE_DIR>
587 The value is a directory name.
589 =item B<SSL_CONF_TYPE_NONE>
591 The value string is not used e.g. a command line option which doesn't take an
598 The order of operations is significant. This can be used to set either defaults
599 or values which cannot be overridden. For example if an application calls:
601 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
602 SSL_CONF_cmd(ctx, userparam, uservalue);
604 it will disable SSLv3 support by default but the user can override it. If
605 however the call sequence is:
607 SSL_CONF_cmd(ctx, userparam, uservalue);
608 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
610 SSLv3 is B<always> disabled and attempt to override this by the user are
613 By checking the return code of SSL_CONF_cmd() it is possible to query if a
614 given B<option> is recognised, this is useful if SSL_CONF_cmd() values are
615 mixed with additional application specific operations.
617 For example an application might call SSL_CONF_cmd() and if it returns
618 -2 (unrecognised command) continue with processing of application specific
621 Applications can also use SSL_CONF_cmd() to process command lines though the
622 utility function SSL_CONF_cmd_argv() is normally used instead. One way
623 to do this is to set the prefix to an appropriate value using
624 SSL_CONF_CTX_set1_prefix(), pass the current argument to B<option> and the
625 following argument to B<value> (which may be NULL).
627 In this case if the return value is positive then it is used to skip that
628 number of arguments as they have been processed by SSL_CONF_cmd(). If -2 is
629 returned then B<option> is not recognised and application specific arguments
630 can be checked instead. If -3 is returned a required argument is missing
631 and an error is indicated. If 0 is returned some other error occurred and
632 this can be reported back to the user.
634 The function SSL_CONF_cmd_value_type() can be used by applications to
635 check for the existence of a command or to perform additional syntax
636 checking or translation of the command value. For example if the return
637 value is B<SSL_CONF_TYPE_FILE> an application could translate a relative
638 pathname to an absolute pathname.
642 SSL_CONF_cmd() returns 1 if the value of B<option> is recognised and B<value> is
643 B<NOT> used and 2 if both B<option> and B<value> are used. In other words it
644 returns the number of arguments processed. This is useful when processing
647 A return value of -2 means B<option> is not recognised.
649 A return value of -3 means B<option> is recognised and the command requires a
650 value but B<value> is NULL.
652 A return code of 0 indicates that both B<option> and B<value> are valid but an
653 error occurred attempting to perform the operation: for example due to an
654 error in the syntax of B<value> in this case the error queue may provide
655 additional information.
659 Set supported signature algorithms:
661 SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256");
663 There are various ways to select the supported protocols.
665 This set the minimum protocol version to TLSv1, and so disables SSLv3.
666 This is the recommended way to disable protocols.
668 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1");
670 The following also disables SSLv3:
672 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
674 The following will first enable all protocols, and then disable
676 If no protocol versions were disabled before this has the same effect as
677 "-SSLv3", but if some versions were disables this will re-enable them before
680 SSL_CONF_cmd(ctx, "Protocol", "ALL,-SSLv3");
684 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1.2");
685 SSL_CONF_cmd(ctx, "MaxProtocol", "TLSv1.2");
687 This also only enables TLSv1.2:
689 SSL_CONF_cmd(ctx, "Protocol", "-ALL,TLSv1.2");
691 Disable TLS session tickets:
693 SSL_CONF_cmd(ctx, "Options", "-SessionTicket");
697 SSL_CONF_cmd(ctx, "Options", "Compression");
699 Set supported curves to P-256, P-384:
701 SSL_CONF_cmd(ctx, "Curves", "P-256:P-384");
706 L<SSL_CONF_CTX_new(3)>,
707 L<SSL_CONF_CTX_set_flags(3)>,
708 L<SSL_CONF_CTX_set1_prefix(3)>,
709 L<SSL_CONF_CTX_set_ssl_ctx(3)>,
710 L<SSL_CONF_cmd_argv(3)>,
711 L<SSL_CTX_set_options(3)>
715 The SSL_CONF_cmd() function was added in OpenSSL 1.0.2.
717 The B<SSL_OP_NO_SSL2> option doesn't have effect since 1.1.0, but the macro
718 is retained for backwards compatibility.
720 The B<SSL_CONF_TYPE_NONE> was added in OpenSSL 1.1.0. In earlier versions of
721 OpenSSL passing a command which didn't take an argument would return
722 B<SSL_CONF_TYPE_UNKNOWN>.
724 B<MinProtocol> and B<MaxProtocol> where added in OpenSSL 1.1.0.
726 B<AllowNoDHEKEX> and B<PrioritizeChaCha> were added in OpenSSL 1.1.1.
730 Copyright 2012-2021 The OpenSSL Project Authors. All Rights Reserved.
732 Licensed under the Apache License 2.0 (the "License"). You may not use
733 this file except in compliance with the License. You can obtain a copy
734 in the file LICENSE in the source distribution or at
735 L<https://www.openssl.org/source/license.html>.