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_FLAG_CMDLINE> is set) are listed below. Note: all B<option>
28 names 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<-client_renegotiation>
63 Allows servers to accept client-initiated renegotiation. Equivalent to
64 setting B<SSL_OP_ALLOW_CLIENT_RENEGOTIATION>.
67 =item B<-legacy_renegotiation>
69 Permits the use of unsafe legacy renegotiation. Equivalent to setting
70 B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
72 =item B<-no_renegotiation>
74 Disables all attempts at renegotiation in TLSv1.2 and earlier, same as setting
75 B<SSL_OP_NO_RENEGOTIATION>.
77 =item B<-no_resumption_on_reneg>
79 Sets B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION>. Only used by servers.
81 =item B<-legacy_server_connect>, B<-no_legacy_server_connect>
83 Permits or prohibits the use of unsafe legacy renegotiation for OpenSSL
84 clients only. Equivalent to setting or clearing B<SSL_OP_LEGACY_SERVER_CONNECT>.
86 =item B<-prioritize_chacha>
88 Prioritize ChaCha ciphers when the client has a ChaCha20 cipher at the top of
89 its preference list. This usually indicates a client without AES hardware
90 acceleration (e.g. mobile) is in use. Equivalent to B<SSL_OP_PRIORITIZE_CHACHA>.
91 Only used by servers. Requires B<-serverpref>.
93 =item B<-allow_no_dhe_kex>
95 In TLSv1.3 allow a non-(ec)dhe based key exchange mode on resumption. This means
96 that there will be no forward secrecy for the resumed session.
100 Enables strict mode protocol handling. Equivalent to setting
101 B<SSL_CERT_FLAG_TLS_STRICT>.
103 =item B<-sigalgs> I<algs>
105 This sets the supported signature algorithms for TLSv1.2 and TLSv1.3.
106 For clients this value is used directly for the supported signature
107 algorithms extension. For servers it is used to determine which signature
108 algorithms to support.
110 The B<algs> argument should be a colon separated list of signature
111 algorithms in order of decreasing preference of the form B<algorithm+hash>
112 or B<signature_scheme>. B<algorithm> is one of B<RSA>, B<DSA> or B<ECDSA> and
113 B<hash> is a supported algorithm OID short name such as B<SHA1>, B<SHA224>,
114 B<SHA256>, B<SHA384> of B<SHA512>. Note: algorithm and hash names are case
115 sensitive. B<signature_scheme> is one of the signature schemes defined in
116 TLSv1.3, specified using the IETF name, e.g., B<ecdsa_secp256r1_sha256>,
117 B<ed25519>, or B<rsa_pss_pss_sha256>.
119 If this option is not set then all signature algorithms supported by the
120 OpenSSL library are permissible.
122 Note: algorithms which specify a PKCS#1 v1.5 signature scheme (either by
123 using B<RSA> as the B<algorithm> or by using one of the B<rsa_pkcs1_*>
124 identifiers) are ignored in TLSv1.3 and will not be negotiated.
126 =item B<-client_sigalgs> I<algs>
128 This sets the supported signature algorithms associated with client
129 authentication for TLSv1.2 and TLSv1.3. For servers the B<algs> is used
130 in the B<signature_algorithms> field of a B<CertificateRequest> message.
131 For clients it is used to determine which signature algorithm to use with
132 the client certificate. If a server does not request a certificate this
133 option has no effect.
135 The syntax of B<algs> is identical to B<-sigalgs>. If not set, then the
136 value set for B<-sigalgs> will be used instead.
138 =item B<-groups> I<groups>
140 This sets the supported groups. For clients, the groups are sent using
141 the supported groups extension. For servers, it is used to determine which
142 group to use. This setting affects groups used for signatures (in TLSv1.2
143 and earlier) and key exchange. The first group listed will also be used
144 for the B<key_share> sent by a client in a TLSv1.3 B<ClientHello>.
146 The B<groups> argument is a colon separated list of groups. The group can
147 be either the B<NIST> name (e.g. B<P-256>), some other commonly used name
148 where applicable (e.g. B<X25519>, B<ffdhe2048>) or an OpenSSL OID name
149 (e.g. B<prime256v1>). Group names are case sensitive. The list should be
150 in order of preference with the most preferred group first.
152 Currently supported groups for B<TLSv1.3> are B<P-256>, B<P-384>, B<P-521>,
153 B<X25519>, B<X448>, B<ffdhe2048>, B<ffdhe3072>, B<ffdhe4096>, B<ffdhe6144>,
156 =item B<-curves> I<groups>
158 This is a synonym for the B<-groups> command.
160 =item B<-named_curve> I<curve>
162 This sets the temporary curve used for ephemeral ECDH modes. Only used
165 The B<groups> argument is a curve name or the special value B<auto> which
166 picks an appropriate curve based on client and server preferences. The
167 curve can be either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name
168 (e.g. B<prime256v1>). Curve names are case sensitive.
170 =item B<-cipher> I<ciphers>
172 Sets the TLSv1.2 and below ciphersuite list to B<ciphers>. This list will be
173 combined with any configured TLSv1.3 ciphersuites. Note: syntax checking
174 of B<ciphers> is currently not performed unless a B<SSL> or B<SSL_CTX>
175 structure is associated with B<ctx>.
177 =item B<-ciphersuites> I<1.3ciphers>
179 Sets the available ciphersuites for TLSv1.3 to value. This is a
180 colon-separated list of TLSv1.3 ciphersuite names in order of preference. This
181 list will be combined any configured TLSv1.2 and below ciphersuites.
182 See L<openssl-ciphers(1)> for more information.
184 =item B<-min_protocol> I<minprot>, B<-max_protocol> I<maxprot>
186 Sets the minimum and maximum supported protocol.
187 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
188 B<TLSv1.2>, B<TLSv1.3> for TLS; B<DTLSv1>, B<DTLSv1.2> for DTLS, and B<None>
190 If either the lower or upper bound is not specified then only the other bound
191 applies, if specified.
192 If your application supports both TLS and DTLS you can specify any of these
193 options twice, once with a bound for TLS and again with an appropriate bound
195 To restrict the supported protocol versions use these commands rather than the
196 deprecated alternative commands below.
198 =item B<-record_padding> I<padding>
200 Attempts to pad TLSv1.3 records so that they are a multiple of B<padding>
201 in length on send. A B<padding> of 0 or 1 turns off padding. Otherwise,
202 the B<padding> must be >1 or <=16384.
204 =item B<-debug_broken_protocol>
208 =item B<-no_middlebox>
210 Turn off "middlebox compatibility", as described below.
214 =head2 Additional Options
216 The following options are accepted by SSL_CONF_cmd(), but are not
217 processed by the OpenSSL commands.
221 =item B<-cert> I<file>
223 Attempts to use B<file> as the certificate for the appropriate context. It
224 currently uses SSL_CTX_use_certificate_chain_file() if an B<SSL_CTX>
225 structure is set or SSL_use_certificate_file() with filetype PEM if an
226 B<SSL> structure is set. This option is only supported if certificate
227 operations are permitted.
229 =item B<-key> I<file>
231 Attempts to use B<file> as the private key for the appropriate context. This
232 option is only supported if certificate operations are permitted. Note:
233 if no B<-key> option is set then a private key is not loaded unless the
234 flag B<SSL_CONF_FLAG_REQUIRE_PRIVATE> is set.
236 =item B<-dhparam> I<file>
238 Attempts to use B<file> as the set of temporary DH parameters for
239 the appropriate context. This option is only supported if certificate
240 operations are permitted.
242 =item B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>, B<-no_tls1_3>
244 Disables protocol support for SSLv3, TLSv1.0, TLSv1.1, TLSv1.2 or TLSv1.3 by
245 setting the corresponding options B<SSL_OP_NO_SSLv3>, B<SSL_OP_NO_TLSv1>,
246 B<SSL_OP_NO_TLSv1_1>, B<SSL_OP_NO_TLSv1_2> and B<SSL_OP_NO_TLSv1_3>
247 respectively. These options are deprecated, use B<-min_protocol> and
248 B<-max_protocol> instead.
250 =item B<-anti_replay>, B<-no_anti_replay>
252 Switches replay protection, on or off respectively. With replay protection on,
253 OpenSSL will automatically detect if a session ticket has been used more than
254 once, TLSv1.3 has been negotiated, and early data is enabled on the server. A
255 full handshake is forced if a session ticket is used a second or subsequent
256 time. Anti-Replay is on by default unless overridden by a configuration file and
257 is only used by servers. Anti-replay measures are required for compliance with
258 the TLSv1.3 specification. Some applications may be able to mitigate the replay
259 risks in other ways and in such cases the built-in OpenSSL functionality is not
260 required. Switching off anti-replay is equivalent to B<SSL_OP_NO_ANTI_REPLAY>.
264 =head1 SUPPORTED CONFIGURATION FILE COMMANDS
266 Currently supported B<option> names for configuration files (i.e., when the
267 flag B<SSL_CONF_FLAG_FILE> is set) are listed below. All configuration file
268 B<option> names are case insensitive so B<signaturealgorithms> is recognised
269 as well as B<SignatureAlgorithms>. Unless otherwise stated the B<value> names
270 are also case insensitive.
272 Note: the command prefix (if set) alters the recognised B<option> values.
276 =item B<CipherString>
278 Sets the ciphersuite list for TLSv1.2 and below to B<value>. This list will be
279 combined with any configured TLSv1.3 ciphersuites. Note: syntax
280 checking of B<value> is currently not performed unless an B<SSL> or B<SSL_CTX>
281 structure is associated with B<ctx>.
283 =item B<Ciphersuites>
285 Sets the available ciphersuites for TLSv1.3 to B<value>. This is a
286 colon-separated list of TLSv1.3 ciphersuite names in order of preference. This
287 list will be combined any configured TLSv1.2 and below ciphersuites.
288 See L<openssl-ciphers(1)> for more information.
292 Attempts to use the file B<value> as the certificate for the appropriate
293 context. It currently uses SSL_CTX_use_certificate_chain_file() if an B<SSL_CTX>
294 structure is set or SSL_use_certificate_file() with filetype PEM if an B<SSL>
295 structure is set. This option is only supported if certificate operations
300 Attempts to use the file B<value> as the private key for the appropriate
301 context. This option is only supported if certificate operations
302 are permitted. Note: if no B<PrivateKey> option is set then a private key is
303 not loaded unless the B<SSL_CONF_FLAG_REQUIRE_PRIVATE> is set.
305 =item B<ChainCAFile>, B<ChainCAPath>, B<VerifyCAFile>, B<VerifyCAPath>
307 These options indicate a file or directory used for building certificate
308 chains or verifying certificate chains. These options are only supported
309 if certificate operations are permitted.
311 =item B<RequestCAFile>
313 This option indicates a file containing a set of certificates in PEM form.
314 The subject names of the certificates are sent to the peer in the
315 B<certificate_authorities> extension for TLS 1.3 (in ClientHello or
316 CertificateRequest) or in a certificate request for previous versions or
319 =item B<ServerInfoFile>
321 Attempts to use the file B<value> in the "serverinfo" extension using the
322 function SSL_CTX_use_serverinfo_file.
324 =item B<DHParameters>
326 Attempts to use the file B<value> as the set of temporary DH parameters for
327 the appropriate context. This option is only supported if certificate
328 operations are permitted.
330 =item B<RecordPadding>
332 Attempts to pad TLSv1.3 records so that they are a multiple of B<value> in
333 length on send. A B<value> of 0 or 1 turns off padding. Otherwise, the
334 B<value> must be >1 or <=16384.
336 =item B<SignatureAlgorithms>
338 This sets the supported signature algorithms for TLSv1.2 and TLSv1.3.
340 value is used directly for the supported signature algorithms extension. For
341 servers it is used to determine which signature algorithms to support.
343 The B<value> argument should be a colon separated list of signature algorithms
344 in order of decreasing preference of the form B<algorithm+hash> or
345 B<signature_scheme>. B<algorithm>
346 is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
347 OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
348 Note: algorithm and hash names are case sensitive.
349 B<signature_scheme> is one of the signature schemes defined in TLSv1.3,
350 specified using the IETF name, e.g., B<ecdsa_secp256r1_sha256>, B<ed25519>,
351 or B<rsa_pss_pss_sha256>.
353 If this option is not set then all signature algorithms supported by the
354 OpenSSL library are permissible.
356 Note: algorithms which specify a PKCS#1 v1.5 signature scheme (either by
357 using B<RSA> as the B<algorithm> or by using one of the B<rsa_pkcs1_*>
358 identifiers) are ignored in TLSv1.3 and will not be negotiated.
360 =item B<ClientSignatureAlgorithms>
362 This sets the supported signature algorithms associated with client
363 authentication for TLSv1.2 and TLSv1.3.
364 For servers the value is used in the
365 B<signature_algorithms> field of a B<CertificateRequest> message.
367 used to determine which signature algorithm to use with the client certificate.
368 If a server does not request a certificate this option has no effect.
370 The syntax of B<value> is identical to B<SignatureAlgorithms>. If not set then
371 the value set for B<SignatureAlgorithms> will be used instead.
375 This sets the supported groups. For clients, the groups are
376 sent using the supported groups extension. For servers, it is used
377 to determine which group to use. This setting affects groups used for
378 signatures (in TLSv1.2 and earlier) and key exchange. The first group listed
379 will also be used for the B<key_share> sent by a client in a TLSv1.3
382 The B<value> argument is a colon separated list of groups. The group can be
383 either the B<NIST> name (e.g. B<P-256>), some other commonly used name where
384 applicable (e.g. B<X25519>, B<ffdhe2048>) or an OpenSSL OID name
385 (e.g. B<prime256v1>). Group names are case sensitive. The list should be in
386 order of preference with the most preferred group first.
388 Currently supported groups for B<TLSv1.3> are B<P-256>, B<P-384>, B<P-521>,
389 B<X25519>, B<X448>, B<ffdhe2048>, B<ffdhe3072>, B<ffdhe4096>, B<ffdhe6144>,
394 This is a synonym for the "Groups" command.
398 This sets the minimum supported SSL, TLS or DTLS version.
400 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
401 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
402 The SSL and TLS bounds apply only to TLS-based contexts, while the DTLS bounds
403 apply only to DTLS-based contexts.
404 The command can be repeated with one instance setting a TLS bound, and the
405 other setting a DTLS bound.
406 The value B<None> applies to both types of contexts and disables the limits.
410 This sets the maximum supported SSL, TLS or DTLS version.
412 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
413 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
414 The SSL and TLS bounds apply only to TLS-based contexts, while the DTLS bounds
415 apply only to DTLS-based contexts.
416 The command can be repeated with one instance setting a TLS bound, and the
417 other setting a DTLS bound.
418 The value B<None> applies to both types of contexts and disables the limits.
422 This can be used to enable or disable certain versions of the SSL,
423 TLS or DTLS protocol.
425 The B<value> argument is a comma separated list of supported protocols
426 to enable or disable.
427 If a protocol is preceded by B<-> that version is disabled.
429 All protocol versions are enabled by default.
430 You need to disable at least one protocol version for this setting have any
432 Only enabling some protocol versions does not disable the other protocol
435 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
436 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
437 The special value B<ALL> refers to all supported versions.
439 This can't enable protocols that are disabled using B<MinProtocol>
440 or B<MaxProtocol>, but can disable protocols that are still allowed
443 The B<Protocol> command is fragile and deprecated; do not use it.
444 Use B<MinProtocol> and B<MaxProtocol> instead.
445 If you do use B<Protocol>, make sure that the resulting range of enabled
446 protocols has no "holes", e.g. if TLS 1.0 and TLS 1.2 are both enabled, make
447 sure to also leave TLS 1.1 enabled.
451 The B<value> argument is a comma separated list of various flags to set.
452 If a flag string is preceded B<-> it is disabled.
453 See the L<SSL_CTX_set_options(3)> function for more details of
456 Each option is listed below. Where an operation is enabled by default
457 the B<-flag> syntax is needed to disable it.
459 B<SessionTicket>: session ticket support, enabled by default. Inverse of
460 B<SSL_OP_NO_TICKET>: that is B<-SessionTicket> is the same as setting
463 B<Compression>: SSL/TLS compression support, disabled by default. Inverse
464 of B<SSL_OP_NO_COMPRESSION>.
466 B<EmptyFragments>: use empty fragments as a countermeasure against a
467 SSL 3.0/TLS 1.0 protocol vulnerability affecting CBC ciphers. It
468 is set by default. Inverse of B<SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS>.
470 B<Bugs>: enable various bug workarounds. Same as B<SSL_OP_ALL>.
472 B<DHSingle>: enable single use DH keys, set by default. Inverse of
473 B<SSL_OP_DH_SINGLE>. Only used by servers.
475 B<ECDHSingle>: enable single use ECDH keys, set by default. Inverse of
476 B<SSL_OP_ECDH_SINGLE>. Only used by servers.
478 B<ServerPreference>: use server and not client preference order when
479 determining which cipher suite, signature algorithm or elliptic curve
480 to use for an incoming connection. Equivalent to
481 B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
483 B<PrioritizeChaCha>: prioritizes ChaCha ciphers when the client has a
484 ChaCha20 cipher at the top of its preference list. This usually indicates
485 a mobile client is in use. Equivalent to B<SSL_OP_PRIORITIZE_CHACHA>.
486 Only used by servers.
488 B<NoResumptionOnRenegotiation>: set
489 B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> flag. Only used by servers.
491 B<NoRenegotiation>: disables all attempts at renegotiation in TLSv1.2 and
492 earlier, same as setting B<SSL_OP_NO_RENEGOTIATION>.
494 B<UnsafeLegacyRenegotiation>: permits the use of unsafe legacy renegotiation.
495 Equivalent to B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
497 B<UnsafeLegacyServerConnect>: permits the use of unsafe legacy renegotiation
498 for OpenSSL clients only. Equivalent to B<SSL_OP_LEGACY_SERVER_CONNECT>.
500 B<EncryptThenMac>: use encrypt-then-mac extension, enabled by
501 default. Inverse of B<SSL_OP_NO_ENCRYPT_THEN_MAC>: that is,
502 B<-EncryptThenMac> is the same as setting B<SSL_OP_NO_ENCRYPT_THEN_MAC>.
504 B<AllowNoDHEKEX>: In TLSv1.3 allow a non-(ec)dhe based key exchange mode on
505 resumption. This means that there will be no forward secrecy for the resumed
506 session. Equivalent to B<SSL_OP_ALLOW_NO_DHE_KEX>.
508 B<MiddleboxCompat>: If set then dummy Change Cipher Spec (CCS) messages are sent
509 in TLSv1.3. This has the effect of making TLSv1.3 look more like TLSv1.2 so that
510 middleboxes that do not understand TLSv1.3 will not drop the connection. This
511 option is set by default. A future version of OpenSSL may not set this by
512 default. Equivalent to B<SSL_OP_ENABLE_MIDDLEBOX_COMPAT>.
514 B<AntiReplay>: If set then OpenSSL will automatically detect if a session ticket
515 has been used more than once, TLSv1.3 has been negotiated, and early data is
516 enabled on the server. A full handshake is forced if a session ticket is used a
517 second or subsequent time. This option is set by default and is only used by
518 servers. Anti-replay measures are required to comply with the TLSv1.3
519 specification. Some applications may be able to mitigate the replay risks in
520 other ways and in such cases the built-in OpenSSL functionality is not required.
521 Disabling anti-replay is equivalent to setting B<SSL_OP_NO_ANTI_REPLAY>.
523 B<ExtendedMasterSecret>: use extended master secret extension, enabled by
524 default. Inverse of B<SSL_OP_NO_EXTENDED_MASTER_SECRET>: that is,
525 B<-ExtendedMasterSecret> is the same as setting B<SSL_OP_NO_EXTENDED_MASTER_SECRET>.
527 B<CANames>: use CA names extension, enabled by
528 default. Inverse of B<SSL_OP_DISABLE_TLSEXT_CA_NAMES>: that is,
529 B<-CANames> is the same as setting B<SSL_OP_DISABLE_TLSEXT_CA_NAMES>.
531 B<KTLS>: Enables kernel TLS if support has been compiled in, and it is supported
532 by the negotiated ciphersuites and extensions. Equivalent to
533 B<SSL_OP_ENABLE_KTLS>.
537 The B<value> argument is a comma separated list of flags to set.
539 B<Peer> enables peer verification: for clients only.
541 B<Request> requests but does not require a certificate from the client.
544 B<Require> requests and requires a certificate from the client: an error
545 occurs if the client does not present a certificate. Servers only.
547 B<Once> requests a certificate from a client only on the initial connection:
548 not when renegotiating. Servers only.
550 B<RequestPostHandshake> configures the connection to support requests but does
551 not require a certificate from the client post-handshake. A certificate will
552 not be requested during the initial handshake. The server application must
553 provide a mechanism to request a certificate post-handshake. Servers only.
556 B<RequiresPostHandshake> configures the connection to support requests and
557 requires a certificate from the client post-handshake: an error occurs if the
558 client does not present a certificate. A certificate will not be requested
559 during the initial handshake. The server application must provide a mechanism
560 to request a certificate post-handshake. Servers only. TLSv1.3 only.
562 =item B<ClientCAFile>, B<ClientCAPath>
564 A file or directory of certificates in PEM format whose names are used as the
565 set of acceptable names for client CAs. Servers only. This option is only
566 supported if certificate operations are permitted.
570 =head1 SUPPORTED COMMAND TYPES
572 The function SSL_CONF_cmd_value_type() currently returns one of the following
577 =item B<SSL_CONF_TYPE_UNKNOWN>
579 The B<option> string is unrecognised, this return value can be use to flag
582 =item B<SSL_CONF_TYPE_STRING>
584 The value is a string without any specific structure.
586 =item B<SSL_CONF_TYPE_FILE>
588 The value is a filename.
590 =item B<SSL_CONF_TYPE_DIR>
592 The value is a directory name.
594 =item B<SSL_CONF_TYPE_NONE>
596 The value string is not used e.g. a command line option which doesn't take an
603 The order of operations is significant. This can be used to set either defaults
604 or values which cannot be overridden. For example if an application calls:
606 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
607 SSL_CONF_cmd(ctx, userparam, uservalue);
609 it will disable SSLv3 support by default but the user can override it. If
610 however the call sequence is:
612 SSL_CONF_cmd(ctx, userparam, uservalue);
613 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
615 SSLv3 is B<always> disabled and attempt to override this by the user are
618 By checking the return code of SSL_CONF_cmd() it is possible to query if a
619 given B<option> is recognised, this is useful if SSL_CONF_cmd() values are
620 mixed with additional application specific operations.
622 For example an application might call SSL_CONF_cmd() and if it returns
623 -2 (unrecognised command) continue with processing of application specific
626 Applications can also use SSL_CONF_cmd() to process command lines though the
627 utility function SSL_CONF_cmd_argv() is normally used instead. One way
628 to do this is to set the prefix to an appropriate value using
629 SSL_CONF_CTX_set1_prefix(), pass the current argument to B<option> and the
630 following argument to B<value> (which may be NULL).
632 In this case if the return value is positive then it is used to skip that
633 number of arguments as they have been processed by SSL_CONF_cmd(). If -2 is
634 returned then B<option> is not recognised and application specific arguments
635 can be checked instead. If -3 is returned a required argument is missing
636 and an error is indicated. If 0 is returned some other error occurred and
637 this can be reported back to the user.
639 The function SSL_CONF_cmd_value_type() can be used by applications to
640 check for the existence of a command or to perform additional syntax
641 checking or translation of the command value. For example if the return
642 value is B<SSL_CONF_TYPE_FILE> an application could translate a relative
643 pathname to an absolute pathname.
647 SSL_CONF_cmd() returns 1 if the value of B<option> is recognised and B<value> is
648 B<NOT> used and 2 if both B<option> and B<value> are used. In other words it
649 returns the number of arguments processed. This is useful when processing
652 A return value of -2 means B<option> is not recognised.
654 A return value of -3 means B<option> is recognised and the command requires a
655 value but B<value> is NULL.
657 A return code of 0 indicates that both B<option> and B<value> are valid but an
658 error occurred attempting to perform the operation: for example due to an
659 error in the syntax of B<value> in this case the error queue may provide
660 additional information.
664 Set supported signature algorithms:
666 SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256");
668 There are various ways to select the supported protocols.
670 This set the minimum protocol version to TLSv1, and so disables SSLv3.
671 This is the recommended way to disable protocols.
673 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1");
675 The following also disables SSLv3:
677 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
679 The following will first enable all protocols, and then disable
681 If no protocol versions were disabled before this has the same effect as
682 "-SSLv3", but if some versions were disables this will re-enable them before
685 SSL_CONF_cmd(ctx, "Protocol", "ALL,-SSLv3");
689 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1.2");
690 SSL_CONF_cmd(ctx, "MaxProtocol", "TLSv1.2");
692 This also only enables TLSv1.2:
694 SSL_CONF_cmd(ctx, "Protocol", "-ALL,TLSv1.2");
696 Disable TLS session tickets:
698 SSL_CONF_cmd(ctx, "Options", "-SessionTicket");
702 SSL_CONF_cmd(ctx, "Options", "Compression");
704 Set supported curves to P-256, P-384:
706 SSL_CONF_cmd(ctx, "Curves", "P-256:P-384");
711 L<SSL_CONF_CTX_new(3)>,
712 L<SSL_CONF_CTX_set_flags(3)>,
713 L<SSL_CONF_CTX_set1_prefix(3)>,
714 L<SSL_CONF_CTX_set_ssl_ctx(3)>,
715 L<SSL_CONF_cmd_argv(3)>,
716 L<SSL_CTX_set_options(3)>
720 The SSL_CONF_cmd() function was added in OpenSSL 1.0.2.
722 The B<SSL_OP_NO_SSL2> option doesn't have effect since 1.1.0, but the macro
723 is retained for backwards compatibility.
725 The B<SSL_CONF_TYPE_NONE> was added in OpenSSL 1.1.0. In earlier versions of
726 OpenSSL passing a command which didn't take an argument would return
727 B<SSL_CONF_TYPE_UNKNOWN>.
729 B<MinProtocol> and B<MaxProtocol> where added in OpenSSL 1.1.0.
731 B<AllowNoDHEKEX> and B<PrioritizeChaCha> were added in OpenSSL 1.1.1.
733 The B<UnsafeLegacyServerConnect> option is no longer set by default from
738 Copyright 2012-2022 The OpenSSL Project Authors. All Rights Reserved.
740 Licensed under the Apache License 2.0 (the "License"). You may not use
741 this file except in compliance with the License. You can obtain a copy
742 in the file LICENSE in the source distribution or at
743 L<https://www.openssl.org/source/license.html>.