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. Currently supported
182 protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>, B<TLSv1.2>, B<TLSv1.3>
183 for TLS and B<DTLSv1>, B<DTLSv1.2> for DTLS, and B<None> for no limit.
184 If either bound is not specified then only the other bound applies,
185 if specified. To restrict the supported protocol versions use these
186 commands rather than the deprecated alternative commands below.
188 =item B<-record_padding> I<padding>
190 Attempts to pad TLSv1.3 records so that they are a multiple of B<padding>
191 in length on send. A B<padding> of 0 or 1 turns off padding. Otherwise,
192 the B<padding> must be >1 or <=16384.
194 =item B<-debug_broken_protocol>
198 =item B<-no_middlebox>
200 Turn off "middlebox compatibility", as described below.
204 =head2 Additional Options
206 The following options are accepted by SSL_CONF_cmd(), but are not
207 processed by the OpenSSL commands.
211 =item B<-cert> I<file>
213 Attempts to use B<file> as the certificate for the appropriate context. It
214 currently uses SSL_CTX_use_certificate_chain_file() if an B<SSL_CTX>
215 structure is set or SSL_use_certificate_file() with filetype PEM if an
216 B<SSL> structure is set. This option is only supported if certificate
217 operations are permitted.
219 =item B<-key> I<file>
221 Attempts to use B<file> as the private key for the appropriate context. This
222 option is only supported if certificate operations are permitted. Note:
223 if no B<-key> option is set then a private key is not loaded unless the
224 flag B<SSL_CONF_FLAG_REQUIRE_PRIVATE> is set.
226 =item B<-dhparam> I<file>
228 Attempts to use B<file> as the set of temporary DH parameters for
229 the appropriate context. This option is only supported if certificate
230 operations are permitted.
232 =item B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>, B<-no_tls1_3>
234 Disables protocol support for SSLv3, TLSv1.0, TLSv1.1, TLSv1.2 or TLSv1.3 by
235 setting the corresponding options B<SSL_OP_NO_SSLv3>, B<SSL_OP_NO_TLSv1>,
236 B<SSL_OP_NO_TLSv1_1>, B<SSL_OP_NO_TLSv1_2> and B<SSL_OP_NO_TLSv1_3>
237 respectively. These options are deprecated, use B<-min_protocol> and
238 B<-max_protocol> instead.
240 =item B<-anti_replay>, B<-no_anti_replay>
242 Switches replay protection, on or off respectively. With replay protection on,
243 OpenSSL will automatically detect if a session ticket has been used more than
244 once, TLSv1.3 has been negotiated, and early data is enabled on the server. A
245 full handshake is forced if a session ticket is used a second or subsequent
246 time. Anti-Replay is on by default unless overridden by a configuration file and
247 is only used by servers. Anti-replay measures are required for compliance with
248 the TLSv1.3 specification. Some applications may be able to mitigate the replay
249 risks in other ways and in such cases the built-in OpenSSL functionality is not
250 required. Switching off anti-replay is equivalent to B<SSL_OP_NO_ANTI_REPLAY>.
254 =head1 SUPPORTED CONFIGURATION FILE COMMANDS
256 Currently supported B<option> names for configuration files (i.e., when the
257 flag B<SSL_CONF_FLAG_FILE> is set) are listed below. All configuration file
258 B<option> names are case insensitive so B<signaturealgorithms> is recognised
259 as well as B<SignatureAlgorithms>. Unless otherwise stated the B<value> names
260 are also case insensitive.
262 Note: the command prefix (if set) alters the recognised B<option> values.
266 =item B<CipherString>
268 Sets the ciphersuite list for TLSv1.2 and below to B<value>. This list will be
269 combined with any configured TLSv1.3 ciphersuites. Note: syntax
270 checking of B<value> is currently not performed unless an B<SSL> or B<SSL_CTX>
271 structure is associated with B<ctx>.
273 =item B<Ciphersuites>
275 Sets the available ciphersuites for TLSv1.3 to B<value>. This is a
276 colon-separated list of TLSv1.3 ciphersuite names in order of preference. This
277 list will be combined any configured TLSv1.2 and below ciphersuites.
278 See L<openssl-ciphers(1)> for more information.
282 Attempts to use the file B<value> as the certificate for the appropriate
283 context. It currently uses SSL_CTX_use_certificate_chain_file() if an B<SSL_CTX>
284 structure is set or SSL_use_certificate_file() with filetype PEM if an B<SSL>
285 structure is set. This option is only supported if certificate operations
290 Attempts to use the file B<value> as the private key for the appropriate
291 context. This option is only supported if certificate operations
292 are permitted. Note: if no B<PrivateKey> option is set then a private key is
293 not loaded unless the B<SSL_CONF_FLAG_REQUIRE_PRIVATE> is set.
295 =item B<ChainCAFile>, B<ChainCAPath>, B<VerifyCAFile>, B<VerifyCAPath>
297 These options indicate a file or directory used for building certificate
298 chains or verifying certificate chains. These options are only supported
299 if certificate operations are permitted.
301 =item B<RequestCAFile>
303 This option indicates a file containing a set of certificates in PEM form.
304 The subject names of the certificates are sent to the peer in the
305 B<certificate_authorities> extension for TLS 1.3 (in ClientHello or
306 CertificateRequest) or in a certificate request for previous versions or
309 =item B<ServerInfoFile>
311 Attempts to use the file B<value> in the "serverinfo" extension using the
312 function SSL_CTX_use_serverinfo_file.
314 =item B<DHParameters>
316 Attempts to use the file B<value> as the set of temporary DH parameters for
317 the appropriate context. This option is only supported if certificate
318 operations are permitted.
320 =item B<RecordPadding>
322 Attempts to pad TLSv1.3 records so that they are a multiple of B<value> in
323 length on send. A B<value> of 0 or 1 turns off padding. Otherwise, the
324 B<value> must be >1 or <=16384.
326 =item B<SignatureAlgorithms>
328 This sets the supported signature algorithms for TLSv1.2 and TLSv1.3.
330 value is used directly for the supported signature algorithms extension. For
331 servers it is used to determine which signature algorithms to support.
333 The B<value> argument should be a colon separated list of signature algorithms
334 in order of decreasing preference of the form B<algorithm+hash> or
335 B<signature_scheme>. B<algorithm>
336 is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
337 OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
338 Note: algorithm and hash names are case sensitive.
339 B<signature_scheme> is one of the signature schemes defined in TLSv1.3,
340 specified using the IETF name, e.g., B<ecdsa_secp256r1_sha256>, B<ed25519>,
341 or B<rsa_pss_pss_sha256>.
343 If this option is not set then all signature algorithms supported by the
344 OpenSSL library are permissible.
346 Note: algorithms which specify a PKCS#1 v1.5 signature scheme (either by
347 using B<RSA> as the B<algorithm> or by using one of the B<rsa_pkcs1_*>
348 identifiers) are ignored in TLSv1.3 and will not be negotiated.
350 =item B<ClientSignatureAlgorithms>
352 This sets the supported signature algorithms associated with client
353 authentication for TLSv1.2 and TLSv1.3.
354 For servers the value is used in the
355 B<signature_algorithms> field of a B<CertificateRequest> message.
357 used to determine which signature algorithm to use with the client certificate.
358 If a server does not request a certificate this option has no effect.
360 The syntax of B<value> is identical to B<SignatureAlgorithms>. If not set then
361 the value set for B<SignatureAlgorithms> will be used instead.
365 This sets the supported groups. For clients, the groups are
366 sent using the supported groups extension. For servers, it is used
367 to determine which group to use. This setting affects groups used for
368 signatures (in TLSv1.2 and earlier) and key exchange. The first group listed
369 will also be used for the B<key_share> sent by a client in a TLSv1.3
372 The B<value> argument is a colon separated list of groups. The group can be
373 either the B<NIST> name (e.g. B<P-256>), some other commonly used name where
374 applicable (e.g. B<X25519>, B<ffdhe2048>) or an OpenSSL OID name
375 (e.g B<prime256v1>). Group names are case sensitive. The list should be in
376 order of preference with the most preferred group first.
378 Currently supported groups for B<TLSv1.3> are B<P-256>, B<P-384>, B<P-521>,
379 B<X25519>, B<X448>, B<ffdhe2048>, B<ffdhe3072>, B<ffdhe4096>, B<ffdhe6144>,
384 This is a synonym for the "Groups" command.
388 This sets the minimum supported SSL, TLS or DTLS version.
390 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
391 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
392 The value B<None> will disable the limit.
396 This sets the maximum supported SSL, TLS or DTLS version.
398 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
399 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
400 The value B<None> will disable the limit.
404 This can be used to enable or disable certain versions of the SSL,
405 TLS or DTLS protocol.
407 The B<value> argument is a comma separated list of supported protocols
408 to enable or disable.
409 If a protocol is preceded by B<-> that version is disabled.
411 All protocol versions are enabled by default.
412 You need to disable at least one protocol version for this setting have any
414 Only enabling some protocol versions does not disable the other protocol
417 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
418 B<TLSv1.2>, B<TLSv1.3>, B<DTLSv1> and B<DTLSv1.2>.
419 The special value B<ALL> refers to all supported versions.
421 This can't enable protocols that are disabled using B<MinProtocol>
422 or B<MaxProtocol>, but can disable protocols that are still allowed
425 The B<Protocol> command is fragile and deprecated; do not use it.
426 Use B<MinProtocol> and B<MaxProtocol> instead.
427 If you do use B<Protocol>, make sure that the resulting range of enabled
428 protocols has no "holes", e.g. if TLS 1.0 and TLS 1.2 are both enabled, make
429 sure to also leave TLS 1.1 enabled.
433 The B<value> argument is a comma separated list of various flags to set.
434 If a flag string is preceded B<-> it is disabled.
435 See the L<SSL_CTX_set_options(3)> function for more details of
438 Each option is listed below. Where an operation is enabled by default
439 the B<-flag> syntax is needed to disable it.
441 B<SessionTicket>: session ticket support, enabled by default. Inverse of
442 B<SSL_OP_NO_TICKET>: that is B<-SessionTicket> is the same as setting
445 B<Compression>: SSL/TLS compression support, enabled by default. Inverse
446 of B<SSL_OP_NO_COMPRESSION>.
448 B<EmptyFragments>: use empty fragments as a countermeasure against a
449 SSL 3.0/TLS 1.0 protocol vulnerability affecting CBC ciphers. It
450 is set by default. Inverse of B<SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS>.
452 B<Bugs>: enable various bug workarounds. Same as B<SSL_OP_ALL>.
454 B<DHSingle>: enable single use DH keys, set by default. Inverse of
455 B<SSL_OP_DH_SINGLE>. Only used by servers.
457 B<ECDHSingle>: enable single use ECDH keys, set by default. Inverse of
458 B<SSL_OP_ECDH_SINGLE>. Only used by servers.
460 B<ServerPreference>: use server and not client preference order when
461 determining which cipher suite, signature algorithm or elliptic curve
462 to use for an incoming connection. Equivalent to
463 B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
465 B<PrioritizeChaCha>: prioritizes ChaCha ciphers when the client has a
466 ChaCha20 cipher at the top of its preference list. This usually indicates
467 a mobile client is in use. Equivalent to B<SSL_OP_PRIORITIZE_CHACHA>.
468 Only used by servers.
470 B<NoResumptionOnRenegotiation>: set
471 B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> flag. Only used by servers.
473 B<NoRenegotiation>: disables all attempts at renegotiation in TLSv1.2 and
474 earlier, same as setting B<SSL_OP_NO_RENEGOTIATION>.
476 B<UnsafeLegacyRenegotiation>: permits the use of unsafe legacy renegotiation.
477 Equivalent to B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
479 B<UnsafeLegacyServerConnect>: permits the use of unsafe legacy renegotiation
480 for OpenSSL clients only. Equivalent to B<SSL_OP_LEGACY_SERVER_CONNECT>.
483 B<EncryptThenMac>: use encrypt-then-mac extension, enabled by
484 default. Inverse of B<SSL_OP_NO_ENCRYPT_THEN_MAC>: that is,
485 B<-EncryptThenMac> is the same as setting B<SSL_OP_NO_ENCRYPT_THEN_MAC>.
487 B<AllowNoDHEKEX>: In TLSv1.3 allow a non-(ec)dhe based key exchange mode on
488 resumption. This means that there will be no forward secrecy for the resumed
489 session. Equivalent to B<SSL_OP_ALLOW_NO_DHE_KEX>.
491 B<MiddleboxCompat>: If set then dummy Change Cipher Spec (CCS) messages are sent
492 in TLSv1.3. This has the effect of making TLSv1.3 look more like TLSv1.2 so that
493 middleboxes that do not understand TLSv1.3 will not drop the connection. This
494 option is set by default. A future version of OpenSSL may not set this by
495 default. Equivalent to B<SSL_OP_ENABLE_MIDDLEBOX_COMPAT>.
497 B<AntiReplay>: If set then OpenSSL will automatically detect if a session ticket
498 has been used more than once, TLSv1.3 has been negotiated, and early data is
499 enabled on the server. A full handshake is forced if a session ticket is used a
500 second or subsequent time. This option is set by default and is only used by
501 servers. Anti-replay measures are required to comply with the TLSv1.3
502 specification. Some applications may be able to mitigate the replay risks in
503 other ways and in such cases the built-in OpenSSL functionality is not required.
504 Disabling anti-replay is equivalent to setting B<SSL_OP_NO_ANTI_REPLAY>.
506 B<ExtendedMasterSecret>: use extended master secret extension, enabled by
507 default. Inverse of B<SSL_OP_NO_EXTENDED_MASTER_SECRET>: that is,
508 B<-ExtendedMasterSecret> is the same as setting B<SSL_OP_NO_EXTENDED_MASTER_SECRET>.
512 The B<value> argument is a comma separated list of flags to set.
514 B<Peer> enables peer verification: for clients only.
516 B<Request> requests but does not require a certificate from the client.
519 B<Require> requests and requires a certificate from the client: an error
520 occurs if the client does not present a certificate. Servers only.
522 B<Once> requests a certificate from a client only on the initial connection:
523 not when renegotiating. Servers only.
525 B<RequestPostHandshake> configures the connection to support requests but does
526 not require a certificate from the client post-handshake. A certificate will
527 not be requested during the initial handshake. The server application must
528 provide a mechanism to request a certificate post-handshake. Servers only.
531 B<RequiresPostHandshake> configures the connection to support requests and
532 requires a certificate from the client post-handshake: an error occurs if the
533 client does not present a certificate. A certificate will not be requested
534 during the initial handshake. The server application must provide a mechanism
535 to request a certificate post-handshake. Servers only. TLSv1.3 only.
537 =item B<ClientCAFile>, B<ClientCAPath>
539 A file or directory of certificates in PEM format whose names are used as the
540 set of acceptable names for client CAs. Servers only. This option is only
541 supported if certificate operations are permitted.
545 =head1 SUPPORTED COMMAND TYPES
547 The function SSL_CONF_cmd_value_type() currently returns one of the following
552 =item B<SSL_CONF_TYPE_UNKNOWN>
554 The B<option> string is unrecognised, this return value can be use to flag
557 =item B<SSL_CONF_TYPE_STRING>
559 The value is a string without any specific structure.
561 =item B<SSL_CONF_TYPE_FILE>
563 The value is a filename.
565 =item B<SSL_CONF_TYPE_DIR>
567 The value is a directory name.
569 =item B<SSL_CONF_TYPE_NONE>
571 The value string is not used e.g. a command line option which doesn't take an
578 The order of operations is significant. This can be used to set either defaults
579 or values which cannot be overridden. For example if an application calls:
581 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
582 SSL_CONF_cmd(ctx, userparam, uservalue);
584 it will disable SSLv3 support by default but the user can override it. If
585 however the call sequence is:
587 SSL_CONF_cmd(ctx, userparam, uservalue);
588 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
590 SSLv3 is B<always> disabled and attempt to override this by the user are
593 By checking the return code of SSL_CONF_cmd() it is possible to query if a
594 given B<option> is recognised, this is useful if SSL_CONF_cmd() values are
595 mixed with additional application specific operations.
597 For example an application might call SSL_CONF_cmd() and if it returns
598 -2 (unrecognised command) continue with processing of application specific
601 Applications can also use SSL_CONF_cmd() to process command lines though the
602 utility function SSL_CONF_cmd_argv() is normally used instead. One way
603 to do this is to set the prefix to an appropriate value using
604 SSL_CONF_CTX_set1_prefix(), pass the current argument to B<option> and the
605 following argument to B<value> (which may be NULL).
607 In this case if the return value is positive then it is used to skip that
608 number of arguments as they have been processed by SSL_CONF_cmd(). If -2 is
609 returned then B<option> is not recognised and application specific arguments
610 can be checked instead. If -3 is returned a required argument is missing
611 and an error is indicated. If 0 is returned some other error occurred and
612 this can be reported back to the user.
614 The function SSL_CONF_cmd_value_type() can be used by applications to
615 check for the existence of a command or to perform additional syntax
616 checking or translation of the command value. For example if the return
617 value is B<SSL_CONF_TYPE_FILE> an application could translate a relative
618 pathname to an absolute pathname.
622 SSL_CONF_cmd() returns 1 if the value of B<option> is recognised and B<value> is
623 B<NOT> used and 2 if both B<option> and B<value> are used. In other words it
624 returns the number of arguments processed. This is useful when processing
627 A return value of -2 means B<option> is not recognised.
629 A return value of -3 means B<option> is recognised and the command requires a
630 value but B<value> is NULL.
632 A return code of 0 indicates that both B<option> and B<value> are valid but an
633 error occurred attempting to perform the operation: for example due to an
634 error in the syntax of B<value> in this case the error queue may provide
635 additional information.
639 Set supported signature algorithms:
641 SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256");
643 There are various ways to select the supported protocols.
645 This set the minimum protocol version to TLSv1, and so disables SSLv3.
646 This is the recommended way to disable protocols.
648 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1");
650 The following also disables SSLv3:
652 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
654 The following will first enable all protocols, and then disable
656 If no protocol versions were disabled before this has the same effect as
657 "-SSLv3", but if some versions were disables this will re-enable them before
660 SSL_CONF_cmd(ctx, "Protocol", "ALL,-SSLv3");
664 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1.2");
665 SSL_CONF_cmd(ctx, "MaxProtocol", "TLSv1.2");
667 This also only enables TLSv1.2:
669 SSL_CONF_cmd(ctx, "Protocol", "-ALL,TLSv1.2");
671 Disable TLS session tickets:
673 SSL_CONF_cmd(ctx, "Options", "-SessionTicket");
677 SSL_CONF_cmd(ctx, "Options", "Compression");
679 Set supported curves to P-256, P-384:
681 SSL_CONF_cmd(ctx, "Curves", "P-256:P-384");
686 L<SSL_CONF_CTX_new(3)>,
687 L<SSL_CONF_CTX_set_flags(3)>,
688 L<SSL_CONF_CTX_set1_prefix(3)>,
689 L<SSL_CONF_CTX_set_ssl_ctx(3)>,
690 L<SSL_CONF_cmd_argv(3)>,
691 L<SSL_CTX_set_options(3)>
695 The SSL_CONF_cmd() function was added in OpenSSL 1.0.2.
697 The B<SSL_OP_NO_SSL2> option doesn't have effect since 1.1.0, but the macro
698 is retained for backwards compatibility.
700 The B<SSL_CONF_TYPE_NONE> was added in OpenSSL 1.1.0. In earlier versions of
701 OpenSSL passing a command which didn't take an argument would return
702 B<SSL_CONF_TYPE_UNKNOWN>.
704 B<MinProtocol> and B<MaxProtocol> where added in OpenSSL 1.1.0.
706 B<AllowNoDHEKEX> and B<PrioritizeChaCha> were added in OpenSSL 1.1.1.
710 Copyright 2012-2018 The OpenSSL Project Authors. All Rights Reserved.
712 Licensed under the Apache License 2.0 (the "License"). You may not use
713 this file except in compliance with the License. You can obtain a copy
714 in the file LICENSE in the source distribution or at
715 L<https://www.openssl.org/source/license.html>.