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<-client_renegotiation>
63 Allows servers to accept client-initiated renegotiation. Equivalent to
64 setting B<SSL_OP_ALLOW_CLIENT_RENEGOTIATION>.
67 =item B<-legacyrenegotiation>
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<-immediate_renegotiation>
88 Try to do a renegotiation immediately after the handshake.
89 This is for debugging and has no option equivalent.
90 Ignored by the B<openssl s_client> command.
92 =item B<-prioritize_chacha>
94 Prioritize ChaCha ciphers when the client has a ChaCha20 cipher at the top of
95 its preference list. This usually indicates a client without AES hardware
96 acceleration (e.g. mobile) is in use. Equivalent to B<SSL_OP_PRIORITIZE_CHACHA>.
97 Only used by servers. Requires B<-serverpref>.
99 =item B<-allow_no_dhe_kex>
101 In TLSv1.3 allow a non-(ec)dhe based key exchange mode on resumption. This means
102 that there will be no forward secrecy for the resumed session.
106 Enables strict mode protocol handling. Equivalent to setting
107 B<SSL_CERT_FLAG_TLS_STRICT>.
109 =item B<-sigalgs> I<algs>
111 This sets the supported signature algorithms for TLSv1.2 and TLSv1.3.
112 For clients this value is used directly for the supported signature
113 algorithms extension. For servers it is used to determine which signature
114 algorithms to support.
116 The B<algs> argument should be a colon separated list of signature
117 algorithms in order of decreasing preference of the form B<algorithm+hash>
118 or B<signature_scheme>. B<algorithm> is one of B<RSA>, B<DSA> or B<ECDSA> and
119 B<hash> is a supported algorithm OID short name such as B<SHA1>, B<SHA224>,
120 B<SHA256>, B<SHA384> of B<SHA512>. Note: algorithm and hash names are case
121 sensitive. B<signature_scheme> is one of the signature schemes defined in
122 TLSv1.3, specified using the IETF name, e.g., B<ecdsa_secp256r1_sha256>,
123 B<ed25519>, or B<rsa_pss_pss_sha256>.
125 If this option is not set then all signature algorithms supported by the
126 OpenSSL library are permissible.
128 Note: algorithms which specify a PKCS#1 v1.5 signature scheme (either by
129 using B<RSA> as the B<algorithm> or by using one of the B<rsa_pkcs1_*>
130 identifiers) are ignored in TLSv1.3 and will not be negotiated.
132 =item B<-client_sigalgs> I<algs>
134 This sets the supported signature algorithms associated with client
135 authentication for TLSv1.2 and TLSv1.3. For servers the B<algs> is used
136 in the B<signature_algorithms> field of a B<CertificateRequest> message.
137 For clients it is used to determine which signature algorithm to use with
138 the client certificate. If a server does not request a certificate this
139 option has no effect.
141 The syntax of B<algs> is identical to B<-sigalgs>. If not set, then the
142 value set for B<-sigalgs> will be used instead.
144 =item B<-groups> I<groups>
146 This sets the supported groups. For clients, the groups are sent using
147 the supported groups extension. For servers, it is used to determine which
148 group to use. This setting affects groups used for signatures (in TLSv1.2
149 and earlier) and key exchange. The first group listed will also be used
150 for the B<key_share> sent by a client in a TLSv1.3 B<ClientHello>.
152 The B<groups> argument is a colon separated list of groups. The group can
153 be either the B<NIST> name (e.g. B<P-256>), some other commonly used name
154 where applicable (e.g. B<X25519>, B<ffdhe2048>) or an OpenSSL OID name
155 (e.g. B<prime256v1>). Group names are case sensitive. The list should be
156 in order of preference with the most preferred group first.
158 Currently supported groups for B<TLSv1.3> are B<P-256>, B<P-384>, B<P-521>,
159 B<X25519>, B<X448>, B<ffdhe2048>, B<ffdhe3072>, B<ffdhe4096>, B<ffdhe6144>,
162 =item B<-curves> I<groups>
164 This is a synonym for the B<-groups> command.
166 =item B<-named_curve> I<curve>
168 This sets the temporary curve used for ephemeral ECDH modes. Only used
171 The B<groups> argument is a curve name or the special value B<auto> which
172 picks an appropriate curve based on client and server preferences. The
173 curve can be either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name
174 (e.g. B<prime256v1>). Curve names are case sensitive.
176 =item B<-cipher> I<ciphers>
178 Sets the TLSv1.2 and below ciphersuite list to B<ciphers>. This list will be
179 combined with any configured TLSv1.3 ciphersuites. Note: syntax checking
180 of B<ciphers> is currently not performed unless a B<SSL> or B<SSL_CTX>
181 structure is associated with B<ctx>.
183 =item B<-ciphersuites> I<1.3ciphers>
185 Sets the available ciphersuites for TLSv1.3 to value. This is a
186 colon-separated list of TLSv1.3 ciphersuite names in order of preference. This
187 list will be combined any configured TLSv1.2 and below ciphersuites.
188 See L<openssl-ciphers(1)> for more information.
190 =item B<-min_protocol> I<minprot>, B<-max_protocol> I<maxprot>
192 Sets the minimum and maximum supported protocol.
193 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
194 B<TLSv1.2>, B<TLSv1.3> for TLS; B<DTLSv1>, B<DTLSv1.2> for DTLS, and B<None>
196 If either the lower or upper bound is not specified then only the other bound
197 applies, if specified.
198 If your application supports both TLS and DTLS you can specify any of these
199 options twice, once with a bound for TLS and again with an appropriate bound
201 To restrict the supported protocol versions use these commands rather than the
202 deprecated alternative commands below.
204 =item B<-record_padding> I<padding>
206 Attempts to pad TLSv1.3 records so that they are a multiple of B<padding>
207 in length on send. A B<padding> of 0 or 1 turns off padding. Otherwise,
208 the B<padding> must be >1 or <=16384.
210 =item B<-debug_broken_protocol>
214 =item B<-no_middlebox>
216 Turn off "middlebox compatibility", as described below.
220 =head2 Additional Options
222 The following options are accepted by SSL_CONF_cmd(), but are not
223 processed by the OpenSSL commands.
227 =item B<-cert> I<file>
229 Attempts to use B<file> as the certificate for the appropriate context. It
230 currently uses SSL_CTX_use_certificate_chain_file() if an B<SSL_CTX>
231 structure is set or SSL_use_certificate_file() with filetype PEM if an
232 B<SSL> structure is set. This option is only supported if certificate
233 operations are permitted.
235 =item B<-key> I<file>
237 Attempts to use B<file> as the private key for the appropriate context. This
238 option is only supported if certificate operations are permitted. Note:
239 if no B<-key> option is set then a private key is not loaded unless the
240 flag B<SSL_CONF_FLAG_REQUIRE_PRIVATE> is set.
242 =item B<-dhparam> I<file>
244 Attempts to use B<file> as the set of temporary DH parameters for
245 the appropriate context. This option is only supported if certificate
246 operations are permitted.
248 =item B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>, B<-no_tls1_3>
250 Disables protocol support for SSLv3, TLSv1.0, TLSv1.1, TLSv1.2 or TLSv1.3 by
251 setting the corresponding options B<SSL_OP_NO_SSLv3>, B<SSL_OP_NO_TLSv1>,
252 B<SSL_OP_NO_TLSv1_1>, B<SSL_OP_NO_TLSv1_2> and B<SSL_OP_NO_TLSv1_3>
253 respectively. These options are deprecated, use B<-min_protocol> and
254 B<-max_protocol> instead.
256 =item B<-anti_replay>, B<-no_anti_replay>
258 Switches replay protection, on or off respectively. With replay protection on,
259 OpenSSL will automatically detect if a session ticket has been used more than
260 once, TLSv1.3 has been negotiated, and early data is enabled on the server. A
261 full handshake is forced if a session ticket is used a second or subsequent
262 time. Anti-Replay is on by default unless overridden by a configuration file and
263 is only used by servers. Anti-replay measures are required for compliance with
264 the TLSv1.3 specification. Some applications may be able to mitigate the replay
265 risks in other ways and in such cases the built-in OpenSSL functionality is not
266 required. Switching off anti-replay is equivalent to B<SSL_OP_NO_ANTI_REPLAY>.
270 =head1 SUPPORTED CONFIGURATION FILE COMMANDS
272 Currently supported B<option> names for configuration files (i.e., when the
273 flag B<SSL_CONF_FLAG_FILE> is set) are listed below. All configuration file
274 B<option> names are case insensitive so B<signaturealgorithms> is recognised
275 as well as B<SignatureAlgorithms>. Unless otherwise stated the B<value> names
276 are also case insensitive.
278 Note: the command prefix (if set) alters the recognised B<option> values.
282 =item B<CipherString>
284 Sets the ciphersuite list for TLSv1.2 and below to B<value>. This list will be
285 combined with any configured TLSv1.3 ciphersuites. Note: syntax
286 checking of B<value> is currently not performed unless an B<SSL> or B<SSL_CTX>
287 structure is associated with B<ctx>.
289 =item B<Ciphersuites>
291 Sets the available ciphersuites for TLSv1.3 to B<value>. This is a
292 colon-separated list of TLSv1.3 ciphersuite names in order of preference. This
293 list will be combined any configured TLSv1.2 and below ciphersuites.
294 See L<openssl-ciphers(1)> for more information.
298 Attempts to use the file B<value> as the certificate for the appropriate
299 context. It currently uses SSL_CTX_use_certificate_chain_file() if an B<SSL_CTX>
300 structure is set or SSL_use_certificate_file() with filetype PEM if an B<SSL>
301 structure is set. This option is only supported if certificate operations
306 Attempts to use the file B<value> as the private key for the appropriate
307 context. This option is only supported if certificate operations
308 are permitted. Note: if no B<PrivateKey> option is set then a private key is
309 not loaded unless the B<SSL_CONF_FLAG_REQUIRE_PRIVATE> is set.
311 =item B<ChainCAFile>, B<ChainCAPath>, B<VerifyCAFile>, B<VerifyCAPath>
313 These options indicate a file or directory used for building certificate
314 chains or verifying certificate chains. These options are only supported
315 if certificate operations are permitted.
317 =item B<RequestCAFile>
319 This option indicates a file containing a set of certificates in PEM form.
320 The subject names of the certificates are sent to the peer in the
321 B<certificate_authorities> extension for TLS 1.3 (in ClientHello or
322 CertificateRequest) or in a certificate request for previous versions or
325 =item B<ServerInfoFile>
327 Attempts to use the file B<value> in the "serverinfo" extension using the
328 function SSL_CTX_use_serverinfo_file.
330 =item B<DHParameters>
332 Attempts to use the file B<value> as the set of temporary DH parameters for
333 the appropriate context. This option is only supported if certificate
334 operations are permitted.
336 =item B<RecordPadding>
338 Attempts to pad TLSv1.3 records so that they are a multiple of B<value> in
339 length on send. A B<value> of 0 or 1 turns off padding. Otherwise, the
340 B<value> must be >1 or <=16384.
342 =item B<SignatureAlgorithms>
344 This sets the supported signature algorithms for TLSv1.2 and TLSv1.3.
346 value is used directly for the supported signature algorithms extension. For
347 servers it is used to determine which signature algorithms to support.
349 The B<value> argument should be a colon separated list of signature algorithms
350 in order of decreasing preference of the form B<algorithm+hash> or
351 B<signature_scheme>. B<algorithm>
352 is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
353 OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
354 Note: algorithm and hash names are case sensitive.
355 B<signature_scheme> is one of the signature schemes defined in TLSv1.3,
356 specified using the IETF name, e.g., B<ecdsa_secp256r1_sha256>, B<ed25519>,
357 or B<rsa_pss_pss_sha256>.
359 If this option is not set then all signature algorithms supported by the
360 OpenSSL library are permissible.
362 Note: algorithms which specify a PKCS#1 v1.5 signature scheme (either by
363 using B<RSA> as the B<algorithm> or by using one of the B<rsa_pkcs1_*>
364 identifiers) are ignored in TLSv1.3 and will not be negotiated.
366 =item B<ClientSignatureAlgorithms>
368 This sets the supported signature algorithms associated with client
369 authentication for TLSv1.2 and TLSv1.3.
370 For servers the value is used in the
371 B<signature_algorithms> field of a B<CertificateRequest> message.
373 used to determine which signature algorithm to use with the client certificate.
374 If a server does not request a certificate this option has no effect.
376 The syntax of B<value> is identical to B<SignatureAlgorithms>. If not set then
377 the value set for B<SignatureAlgorithms> will be used instead.
381 This sets the supported groups. For clients, the groups are
382 sent using the supported groups extension. For servers, it is used
383 to determine which group to use. This setting affects groups used for
384 signatures (in TLSv1.2 and earlier) and key exchange. The first group listed
385 will also be used for the B<key_share> sent by a client in a TLSv1.3
388 The B<value> argument is a colon separated list of groups. The group can be
389 either the B<NIST> name (e.g. B<P-256>), some other commonly used name where
390 applicable (e.g. B<X25519>, B<ffdhe2048>) or an OpenSSL OID name
391 (e.g. B<prime256v1>). Group names are case sensitive. The list should be in
392 order of preference with the most preferred group first.
394 Currently supported groups for B<TLSv1.3> are B<P-256>, B<P-384>, B<P-521>,
395 B<X25519>, B<X448>, B<ffdhe2048>, B<ffdhe3072>, B<ffdhe4096>, B<ffdhe6144>,
400 This is a synonym for the "Groups" command.
404 This sets the minimum 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 sets the maximum supported SSL, TLS or DTLS version.
418 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
419 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
420 The SSL and TLS bounds apply only to TLS-based contexts, while the DTLS bounds
421 apply only to DTLS-based contexts.
422 The command can be repeated with one instance setting a TLS bound, and the
423 other setting a DTLS bound.
424 The value B<None> applies to both types of contexts and disables the limits.
428 This can be used to enable or disable certain versions of the SSL,
429 TLS or DTLS protocol.
431 The B<value> argument is a comma separated list of supported protocols
432 to enable or disable.
433 If a protocol is preceded by B<-> that version is disabled.
435 All protocol versions are enabled by default.
436 You need to disable at least one protocol version for this setting have any
438 Only enabling some protocol versions does not disable the other protocol
441 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
442 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
443 The special value B<ALL> refers to all supported versions.
445 This can't enable protocols that are disabled using B<MinProtocol>
446 or B<MaxProtocol>, but can disable protocols that are still allowed
449 The B<Protocol> command is fragile and deprecated; do not use it.
450 Use B<MinProtocol> and B<MaxProtocol> instead.
451 If you do use B<Protocol>, make sure that the resulting range of enabled
452 protocols has no "holes", e.g. if TLS 1.0 and TLS 1.2 are both enabled, make
453 sure to also leave TLS 1.1 enabled.
457 The B<value> argument is a comma separated list of various flags to set.
458 If a flag string is preceded B<-> it is disabled.
459 See the L<SSL_CTX_set_options(3)> function for more details of
462 Each option is listed below. Where an operation is enabled by default
463 the B<-flag> syntax is needed to disable it.
465 B<SessionTicket>: session ticket support, enabled by default. Inverse of
466 B<SSL_OP_NO_TICKET>: that is B<-SessionTicket> is the same as setting
469 B<Compression>: SSL/TLS compression support, enabled by default. Inverse
470 of B<SSL_OP_NO_COMPRESSION>.
472 B<EmptyFragments>: use empty fragments as a countermeasure against a
473 SSL 3.0/TLS 1.0 protocol vulnerability affecting CBC ciphers. It
474 is set by default. Inverse of B<SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS>.
476 B<Bugs>: enable various bug workarounds. Same as B<SSL_OP_ALL>.
478 B<DHSingle>: enable single use DH keys, set by default. Inverse of
479 B<SSL_OP_DH_SINGLE>. Only used by servers.
481 B<ECDHSingle>: enable single use ECDH keys, set by default. Inverse of
482 B<SSL_OP_ECDH_SINGLE>. Only used by servers.
484 B<ServerPreference>: use server and not client preference order when
485 determining which cipher suite, signature algorithm or elliptic curve
486 to use for an incoming connection. Equivalent to
487 B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
489 B<PrioritizeChaCha>: prioritizes ChaCha ciphers when the client has a
490 ChaCha20 cipher at the top of its preference list. This usually indicates
491 a mobile client is in use. Equivalent to B<SSL_OP_PRIORITIZE_CHACHA>.
492 Only used by servers.
494 B<NoResumptionOnRenegotiation>: set
495 B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> flag. Only used by servers.
497 B<NoRenegotiation>: disables all attempts at renegotiation in TLSv1.2 and
498 earlier, same as setting B<SSL_OP_NO_RENEGOTIATION>.
500 B<UnsafeLegacyRenegotiation>: permits the use of unsafe legacy renegotiation.
501 Equivalent to B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
503 B<UnsafeLegacyServerConnect>: permits the use of unsafe legacy renegotiation
504 for OpenSSL clients only. Equivalent to B<SSL_OP_LEGACY_SERVER_CONNECT>.
507 B<EncryptThenMac>: use encrypt-then-mac extension, enabled by
508 default. Inverse of B<SSL_OP_NO_ENCRYPT_THEN_MAC>: that is,
509 B<-EncryptThenMac> is the same as setting B<SSL_OP_NO_ENCRYPT_THEN_MAC>.
511 B<AllowNoDHEKEX>: In TLSv1.3 allow a non-(ec)dhe based key exchange mode on
512 resumption. This means that there will be no forward secrecy for the resumed
513 session. Equivalent to B<SSL_OP_ALLOW_NO_DHE_KEX>.
515 B<MiddleboxCompat>: If set then dummy Change Cipher Spec (CCS) messages are sent
516 in TLSv1.3. This has the effect of making TLSv1.3 look more like TLSv1.2 so that
517 middleboxes that do not understand TLSv1.3 will not drop the connection. This
518 option is set by default. A future version of OpenSSL may not set this by
519 default. Equivalent to B<SSL_OP_ENABLE_MIDDLEBOX_COMPAT>.
521 B<AntiReplay>: If set then OpenSSL will automatically detect if a session ticket
522 has been used more than once, TLSv1.3 has been negotiated, and early data is
523 enabled on the server. A full handshake is forced if a session ticket is used a
524 second or subsequent time. This option is set by default and is only used by
525 servers. Anti-replay measures are required to comply with the TLSv1.3
526 specification. Some applications may be able to mitigate the replay risks in
527 other ways and in such cases the built-in OpenSSL functionality is not required.
528 Disabling anti-replay is equivalent to setting B<SSL_OP_NO_ANTI_REPLAY>.
530 B<ExtendedMasterSecret>: use extended master secret extension, enabled by
531 default. Inverse of B<SSL_OP_NO_EXTENDED_MASTER_SECRET>: that is,
532 B<-ExtendedMasterSecret> is the same as setting B<SSL_OP_NO_EXTENDED_MASTER_SECRET>.
534 B<CANames>: use CA names extension, enabled by
535 default. Inverse of B<SSL_OP_DISABLE_TLSEXT_CA_NAMES>: that is,
536 B<-CANames> is the same as setting B<SSL_OP_DISABLE_TLSEXT_CA_NAMES>.
538 B<KTLS>: Enables kernel TLS if support has been compiled in, and it is supported
539 by the negotiated ciphersuites and extensions. Equivalent to
540 B<SSL_OP_ENABLE_KTLS>.
544 The B<value> argument is a comma separated list of flags to set.
546 B<Peer> enables peer verification: for clients only.
548 B<Request> requests but does not require a certificate from the client.
551 B<Require> requests and requires a certificate from the client: an error
552 occurs if the client does not present a certificate. Servers only.
554 B<Once> requests a certificate from a client only on the initial connection:
555 not when renegotiating. Servers only.
557 B<RequestPostHandshake> configures the connection to support requests but does
558 not require a certificate from the client post-handshake. A certificate will
559 not be requested during the initial handshake. The server application must
560 provide a mechanism to request a certificate post-handshake. Servers only.
563 B<RequiresPostHandshake> configures the connection to support requests and
564 requires a certificate from the client post-handshake: an error occurs if the
565 client does not present a certificate. A certificate will not be requested
566 during the initial handshake. The server application must provide a mechanism
567 to request a certificate post-handshake. Servers only. TLSv1.3 only.
569 =item B<ClientCAFile>, B<ClientCAPath>
571 A file or directory of certificates in PEM format whose names are used as the
572 set of acceptable names for client CAs. Servers only. This option is only
573 supported if certificate operations are permitted.
577 =head1 SUPPORTED COMMAND TYPES
579 The function SSL_CONF_cmd_value_type() currently returns one of the following
584 =item B<SSL_CONF_TYPE_UNKNOWN>
586 The B<option> string is unrecognised, this return value can be use to flag
589 =item B<SSL_CONF_TYPE_STRING>
591 The value is a string without any specific structure.
593 =item B<SSL_CONF_TYPE_FILE>
595 The value is a filename.
597 =item B<SSL_CONF_TYPE_DIR>
599 The value is a directory name.
601 =item B<SSL_CONF_TYPE_NONE>
603 The value string is not used e.g. a command line option which doesn't take an
610 The order of operations is significant. This can be used to set either defaults
611 or values which cannot be overridden. For example if an application calls:
613 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
614 SSL_CONF_cmd(ctx, userparam, uservalue);
616 it will disable SSLv3 support by default but the user can override it. If
617 however the call sequence is:
619 SSL_CONF_cmd(ctx, userparam, uservalue);
620 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
622 SSLv3 is B<always> disabled and attempt to override this by the user are
625 By checking the return code of SSL_CONF_cmd() it is possible to query if a
626 given B<option> is recognised, this is useful if SSL_CONF_cmd() values are
627 mixed with additional application specific operations.
629 For example an application might call SSL_CONF_cmd() and if it returns
630 -2 (unrecognised command) continue with processing of application specific
633 Applications can also use SSL_CONF_cmd() to process command lines though the
634 utility function SSL_CONF_cmd_argv() is normally used instead. One way
635 to do this is to set the prefix to an appropriate value using
636 SSL_CONF_CTX_set1_prefix(), pass the current argument to B<option> and the
637 following argument to B<value> (which may be NULL).
639 In this case if the return value is positive then it is used to skip that
640 number of arguments as they have been processed by SSL_CONF_cmd(). If -2 is
641 returned then B<option> is not recognised and application specific arguments
642 can be checked instead. If -3 is returned a required argument is missing
643 and an error is indicated. If 0 is returned some other error occurred and
644 this can be reported back to the user.
646 The function SSL_CONF_cmd_value_type() can be used by applications to
647 check for the existence of a command or to perform additional syntax
648 checking or translation of the command value. For example if the return
649 value is B<SSL_CONF_TYPE_FILE> an application could translate a relative
650 pathname to an absolute pathname.
654 SSL_CONF_cmd() returns 1 if the value of B<option> is recognised and B<value> is
655 B<NOT> used and 2 if both B<option> and B<value> are used. In other words it
656 returns the number of arguments processed. This is useful when processing
659 A return value of -2 means B<option> is not recognised.
661 A return value of -3 means B<option> is recognised and the command requires a
662 value but B<value> is NULL.
664 A return code of 0 indicates that both B<option> and B<value> are valid but an
665 error occurred attempting to perform the operation: for example due to an
666 error in the syntax of B<value> in this case the error queue may provide
667 additional information.
671 Set supported signature algorithms:
673 SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256");
675 There are various ways to select the supported protocols.
677 This set the minimum protocol version to TLSv1, and so disables SSLv3.
678 This is the recommended way to disable protocols.
680 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1");
682 The following also disables SSLv3:
684 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
686 The following will first enable all protocols, and then disable
688 If no protocol versions were disabled before this has the same effect as
689 "-SSLv3", but if some versions were disables this will re-enable them before
692 SSL_CONF_cmd(ctx, "Protocol", "ALL,-SSLv3");
696 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1.2");
697 SSL_CONF_cmd(ctx, "MaxProtocol", "TLSv1.2");
699 This also only enables TLSv1.2:
701 SSL_CONF_cmd(ctx, "Protocol", "-ALL,TLSv1.2");
703 Disable TLS session tickets:
705 SSL_CONF_cmd(ctx, "Options", "-SessionTicket");
709 SSL_CONF_cmd(ctx, "Options", "Compression");
711 Set supported curves to P-256, P-384:
713 SSL_CONF_cmd(ctx, "Curves", "P-256:P-384");
718 L<SSL_CONF_CTX_new(3)>,
719 L<SSL_CONF_CTX_set_flags(3)>,
720 L<SSL_CONF_CTX_set1_prefix(3)>,
721 L<SSL_CONF_CTX_set_ssl_ctx(3)>,
722 L<SSL_CONF_cmd_argv(3)>,
723 L<SSL_CTX_set_options(3)>
727 The SSL_CONF_cmd() function was added in OpenSSL 1.0.2.
729 The B<SSL_OP_NO_SSL2> option doesn't have effect since 1.1.0, but the macro
730 is retained for backwards compatibility.
732 The B<SSL_CONF_TYPE_NONE> was added in OpenSSL 1.1.0. In earlier versions of
733 OpenSSL passing a command which didn't take an argument would return
734 B<SSL_CONF_TYPE_UNKNOWN>.
736 B<MinProtocol> and B<MaxProtocol> where added in OpenSSL 1.1.0.
738 B<AllowNoDHEKEX> and B<PrioritizeChaCha> were added in OpenSSL 1.1.1.
742 Copyright 2012-2021 The OpenSSL Project Authors. All Rights Reserved.
744 Licensed under the Apache License 2.0 (the "License"). You may not use
745 this file except in compliance with the License. You can obtain a copy
746 in the file LICENSE in the source distribution or at
747 L<https://www.openssl.org/source/license.html>.