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 *cctx, const char *cmd, const char *value);
13 int SSL_CONF_cmd_value_type(SSL_CONF_CTX *cctx, const char *cmd);
17 The function SSL_CONF_cmd() performs configuration operation B<cmd> 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<cmd> refers to.
24 =head1 SUPPORTED COMMAND LINE COMMANDS
26 Currently supported B<cmd> names for command lines (i.e. when the
27 flag B<SSL_CONF_CMDLINE> is set) are listed below. Note: all B<cmd> 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 This sets the supported signature algorithms for TLS v1.2. For clients this
37 value is used directly for the supported signature algorithms extension. For
38 servers it is used to determine which signature algorithms to support.
40 The B<value> argument should be a colon separated list of signature algorithms
41 in order of decreasing preference of the form B<algorithm+hash>. B<algorithm>
42 is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
43 OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
44 Note: algorithm and hash names are case sensitive.
46 If this option is not set then all signature algorithms supported by the
47 OpenSSL library are permissible.
49 =item B<-client_sigalgs>
51 This sets the supported signature algorithms associated with client
52 authentication for TLS v1.2. For servers the value is used in the supported
53 signature algorithms field of a certificate request. For clients it is
54 used to determine which signature algorithm to with the client certificate.
55 If a server does not request a certificate this option has no effect.
57 The syntax of B<value> is identical to B<-sigalgs>. If not set then
58 the value set for B<-sigalgs> will be used instead.
62 This sets the supported groups. For clients, the groups are
63 sent using the supported groups extension. For servers, it is used
64 to determine which group to use. This setting affects groups used for both
65 signatures and key exchange, if applicable. It also affects the preferred
66 key_share sent by a client in a TLSv1.3 compatible connection.
68 The B<value> argument is a colon separated list of groups. The group can be
69 either the B<NIST> name (e.g. B<P-256>), some other commonly used name where
70 applicable (e.g. B<X25519>) or an OpenSSL OID name (e.g B<prime256v1>). Group
71 names are case sensitive. The list should be in order of preference with the
72 most preferred group first. The first listed group will be the one used for a
73 key_share by a TLSv1.3 client.
77 This is a synonym for the "-groups" command.
82 This sets the temporary curve used for ephemeral ECDH modes. Only used by
85 The B<value> argument is a curve name or the special value B<auto> which
86 picks an appropriate curve based on client and server preferences. The curve
87 can be either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name
88 (e.g B<prime256v1>). Curve names are case sensitive.
92 Sets the cipher suite list to B<value>. Note: syntax checking of B<value> is
93 currently not performed unless a B<SSL> or B<SSL_CTX> structure is
94 associated with B<cctx>.
98 Attempts to use the file B<value> as the certificate for the appropriate
99 context. It currently uses SSL_CTX_use_certificate_chain_file() if an B<SSL_CTX>
100 structure is set or SSL_use_certificate_file() with filetype PEM if an B<SSL>
101 structure is set. This option is only supported if certificate operations
106 Attempts to use the file B<value> as the private key for the appropriate
107 context. This option is only supported if certificate operations
108 are permitted. Note: if no B<-key> option is set then a private key is
109 not loaded unless the flag B<SSL_CONF_FLAG_REQUIRE_PRIVATE> is set.
113 Attempts to use the file B<value> as the set of temporary DH parameters for
114 the appropriate context. This option is only supported if certificate
115 operations are permitted.
117 =item B<-record_padding>
119 Attempts to pad TLS 1.3 records so that they are a multiple of B<value> in
120 length on send. A B<value> of 0 or 1 turns off padding. Otherwise, the
121 B<value> must be >1 or <=16384.
123 =item B<-no_renegotiation>
125 Disables all attempts at renegotiation in TLSv1.2 and earlier, same as setting
126 B<SSL_OP_NO_RENEGOTIATION>.
128 =item B<-min_protocol>, B<-max_protocol>
130 Sets the minimum and maximum supported protocol.
131 Currently supported protocol values are B<SSLv3>, B<TLSv1>,
132 B<TLSv1.1>, B<TLSv1.2> for TLS and B<DTLSv1>, B<DTLSv1.2> for DTLS,
133 and B<None> for no limit.
134 If the either bound is not specified then only the other bound applies,
136 To restrict the supported protocol versions use these commands rather
137 than the deprecated alternative commands below.
139 =item B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>, B<-no_tls1_3>
141 Disables protocol support for SSLv3, TLSv1.0, TLSv1.1, TLSv1.2 or TLSv1.3 by
142 setting the corresponding options B<SSL_OP_NO_SSLv3>, B<SSL_OP_NO_TLSv1>,
143 B<SSL_OP_NO_TLSv1_1>, B<SSL_OP_NO_TLSv1_2> and B<SSL_OP_NO_TLSv1_3>
144 respectively. These options are deprecated, instead use B<-min_protocol> and
149 Various bug workarounds are set, same as setting B<SSL_OP_ALL>.
153 Enables support for SSL/TLS compression, same as clearing
154 B<SSL_OP_NO_COMPRESSION>.
155 This command was introduced in OpenSSL 1.1.0.
156 As of OpenSSL 1.1.0, compression is off by default.
160 Disables support for SSL/TLS compression, same as setting
161 B<SSL_OP_NO_COMPRESSION>.
162 As of OpenSSL 1.1.0, compression is off by default.
166 Disables support for session tickets, same as setting B<SSL_OP_NO_TICKET>.
170 Use server and not client preference order when determining which cipher suite,
171 signature algorithm or elliptic curve to use for an incoming connection.
172 Equivalent to B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
174 =item B<-prioritize_chacha>
176 Prioritize ChaCha ciphers when the client has a ChaCha20 cipher at the top of
177 its preference list. This usually indicates a client without AES hardware
178 acceleration (e.g. mobile) is in use. Equivalent to B<SSL_OP_PRIORITIZE_CHACHA>.
179 Only used by servers. Requires B<-serverpref>.
181 =item B<-no_resumption_on_reneg>
183 set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag. Only used by servers.
185 =item B<-legacyrenegotiation>
187 permits the use of unsafe legacy renegotiation. Equivalent to setting
188 B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
190 =item B<-legacy_server_connect>, B<-no_legacy_server_connect>
192 permits or prohibits the use of unsafe legacy renegotiation for OpenSSL
193 clients only. Equivalent to setting or clearing B<SSL_OP_LEGACY_SERVER_CONNECT>.
196 =item B<-allow_no_dhe_kex>
198 In TLSv1.3 allow a non-(ec)dhe based key exchange mode on resumption. This means
199 that there will be no forward secrecy for the resumed session.
203 enables strict mode protocol handling. Equivalent to setting
204 B<SSL_CERT_FLAG_TLS_STRICT>.
208 =head1 SUPPORTED CONFIGURATION FILE COMMANDS
210 Currently supported B<cmd> names for configuration files (i.e. when the
211 flag B<SSL_CONF_FLAG_FILE> is set) are listed below. All configuration file
212 B<cmd> names are case insensitive so B<signaturealgorithms> is recognised
213 as well as B<SignatureAlgorithms>. Unless otherwise stated the B<value> names
214 are also case insensitive.
216 Note: the command prefix (if set) alters the recognised B<cmd> values.
220 =item B<CipherString>
222 Sets the cipher suite list to B<value>. Note: syntax checking of B<value> is
223 currently not performed unless an B<SSL> or B<SSL_CTX> structure is
224 associated with B<cctx>.
228 Attempts to use the file B<value> as the certificate for the appropriate
229 context. It currently uses SSL_CTX_use_certificate_chain_file() if an B<SSL_CTX>
230 structure is set or SSL_use_certificate_file() with filetype PEM if an B<SSL>
231 structure is set. This option is only supported if certificate operations
236 Attempts to use the file B<value> as the private key for the appropriate
237 context. This option is only supported if certificate operations
238 are permitted. Note: if no B<PrivateKey> option is set then a private key is
239 not loaded unless the B<SSL_CONF_FLAG_REQUIRE_PRIVATE> is set.
241 =item B<ChainCAFile>, B<ChainCAPath>, B<VerifyCAFile>, B<VerifyCAPath>
243 These options indicate a file or directory used for building certificate
244 chains or verifying certificate chains. These options are only supported
245 if certificate operations are permitted.
247 =item B<RequestCAFile>
249 This option indicates a file containing a set of certificates in PEM form.
250 The subject names of the certificates are sent to the peer in the
251 B<certificate_authorities> extension for TLS 1.3 (in ClientHello or
252 CertificateRequest) or in a certificate request for previous versions or
255 =item B<ServerInfoFile>
257 Attempts to use the file B<value> in the "serverinfo" extension using the
258 function SSL_CTX_use_serverinfo_file.
260 =item B<DHParameters>
262 Attempts to use the file B<value> as the set of temporary DH parameters for
263 the appropriate context. This option is only supported if certificate
264 operations are permitted.
266 =item B<RecordPadding>
268 Attempts to pad TLS 1.3 records so that they are a multiple of B<value> in
269 length on send. A B<value> of 0 or 1 turns off padding. Otherwise, the
270 B<value> must be >1 or <=16384.
272 =item B<NoRenegotiation>
274 Disables all attempts at renegotiation in TLSv1.2 and earlier, same as setting
275 B<SSL_OP_NO_RENEGOTIATION>.
277 =item B<SignatureAlgorithms>
279 This sets the supported signature algorithms for TLS v1.2. For clients this
280 value is used directly for the supported signature algorithms extension. For
281 servers it is used to determine which signature algorithms to support.
283 The B<value> argument should be a colon separated list of signature algorithms
284 in order of decreasing preference of the form B<algorithm+hash>. B<algorithm>
285 is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
286 OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
287 Note: algorithm and hash names are case sensitive.
289 If this option is not set then all signature algorithms supported by the
290 OpenSSL library are permissible.
292 =item B<ClientSignatureAlgorithms>
294 This sets the supported signature algorithms associated with client
295 authentication for TLS v1.2. For servers the value is used in the supported
296 signature algorithms field of a certificate request. For clients it is
297 used to determine which signature algorithm to with the client certificate.
299 The syntax of B<value> is identical to B<SignatureAlgorithms>. If not set then
300 the value set for B<SignatureAlgorithms> will be used instead.
304 This sets the supported groups. For clients, the groups are
305 sent using the supported groups extension. For servers, it is used
306 to determine which group to use. This setting affects groups used for both
307 signatures and key exchange, if applicable. It also affects the preferred
308 key_share sent by a client in a TLSv1.3 compatible connection.
310 The B<value> argument is a colon separated list of groups. The group can be
311 either the B<NIST> name (e.g. B<P-256>), some other commonly used name where
312 applicable (e.g. B<X25519>) or an OpenSSL OID name (e.g B<prime256v1>). Group
313 names are case sensitive. The list should be in order of preference with the
314 most preferred group first. The first listed group will be the one used for a
315 key_share by a TLSv1.3 client.
319 This is a synonym for the "Groups" command.
323 This sets the minimum supported SSL, TLS or DTLS version.
325 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
326 B<TLSv1.2>, B<DTLSv1> and B<DTLSv1.2>.
327 The value B<None> will disable the limit.
331 This sets the maximum supported SSL, TLS or DTLS version.
333 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
334 B<TLSv1.2>, B<DTLSv1> and B<DTLSv1.2>.
335 The value B<None> will disable the limit.
339 This can be used to enable or disable certain versions of the SSL,
340 TLS or DTLS protocol.
342 The B<value> argument is a comma separated list of supported protocols
343 to enable or disable.
344 If a protocol is preceded by B<-> that version is disabled.
346 All protocol versions are enabled by default.
347 You need to disable at least one protocol version for this setting have any
349 Only enabling some protocol versions does not disable the other protocol
352 Currently supported protocol values are B<SSLv3>, B<TLSv1>, B<TLSv1.1>,
353 B<TLSv1.2>, B<DTLSv1> and B<DTLSv1.2>.
354 The special value B<ALL> refers to all supported versions.
356 This can't enable protocols that are disabled using B<MinProtocol>
357 or B<MaxProtocol>, but can disable protocols that are still allowed
360 The B<Protocol> command is fragile and deprecated; do not use it.
361 Use B<MinProtocol> and B<MaxProtocol> instead.
362 If you do use B<Protocol>, make sure that the resulting range of enabled
363 protocols has no "holes", e.g. if TLS 1.0 and TLS 1.2 are both enabled, make
364 sure to also leave TLS 1.1 enabled.
368 The B<value> argument is a comma separated list of various flags to set.
369 If a flag string is preceded B<-> it is disabled.
370 See the L<SSL_CTX_set_options(3)> function for more details of
373 Each option is listed below. Where an operation is enabled by default
374 the B<-flag> syntax is needed to disable it.
376 B<SessionTicket>: session ticket support, enabled by default. Inverse of
377 B<SSL_OP_NO_TICKET>: that is B<-SessionTicket> is the same as setting
380 B<Compression>: SSL/TLS compression support, enabled by default. Inverse
381 of B<SSL_OP_NO_COMPRESSION>.
383 B<EmptyFragments>: use empty fragments as a countermeasure against a
384 SSL 3.0/TLS 1.0 protocol vulnerability affecting CBC ciphers. It
385 is set by default. Inverse of B<SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS>.
387 B<Bugs>: enable various bug workarounds. Same as B<SSL_OP_ALL>.
389 B<DHSingle>: enable single use DH keys, set by default. Inverse of
390 B<SSL_OP_DH_SINGLE>. Only used by servers.
392 B<ECDHSingle>: enable single use ECDH keys, set by default. Inverse of
393 B<SSL_OP_ECDH_SINGLE>. Only used by servers.
395 B<ServerPreference>: use server and not client preference order when
396 determining which cipher suite, signature algorithm or elliptic curve
397 to use for an incoming connection. Equivalent to
398 B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
400 B<PrioritizeChaCha>: prioritizes ChaCha ciphers when the client has a
401 ChaCha20 cipher at the top of its preference list. This usually indicates
402 a mobile client is in use. Equivalent to B<SSL_OP_PRIORITIZE_CHACHA>.
403 Only used by servers.
405 B<NoResumptionOnRenegotiation>: set
406 B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> flag. Only used by servers.
408 B<UnsafeLegacyRenegotiation>: permits the use of unsafe legacy renegotiation.
409 Equivalent to B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
411 B<UnsafeLegacyServerConnect>: permits the use of unsafe legacy renegotiation
412 for OpenSSL clients only. Equivalent to B<SSL_OP_LEGACY_SERVER_CONNECT>.
415 B<EncryptThenMac>: use encrypt-then-mac extension, enabled by
416 default. Inverse of B<SSL_OP_NO_ENCRYPT_THEN_MAC>: that is,
417 B<-EncryptThenMac> is the same as setting B<SSL_OP_NO_ENCRYPT_THEN_MAC>.
419 B<AllowNoDHEKEX>: In TLSv1.3 allow a non-(ec)dhe based key exchange mode on
420 resumption. This means that there will be no forward secrecy for the resumed
421 session. Equivalent to B<SSL_OP_ALLOW_NO_DHE_KEX>.
423 B<MiddleboxCompat>: If set then dummy Change Cipher Spec (CCS) messages are sent
424 in TLSv1.3. This has the effect of making TLSv1.3 look more like TLSv1.2 so that
425 middleboxes that do not understand TLSv1.3 will not drop the connection. This
426 option is set by default. A future version of OpenSSL may not set this by
427 default. Equivalent to B<SSL_OP_ENABLE_MIDDLEBOX_COMPAT>.
431 The B<value> argument is a comma separated list of flags to set.
433 B<Peer> enables peer verification: for clients only.
435 B<Request> requests but does not require a certificate from the client.
438 B<Require> requests and requires a certificate from the client: an error
439 occurs if the client does not present a certificate. Servers only.
441 B<Once> requests a certificate from a client only on the initial connection:
442 not when renegotiating. Servers only.
444 B<RequestPostHandshake> configures the connection to support requests but does
445 not require a certificate from the client post-handshake. A certificate will
446 not be requested during the initial handshake. The server application must
447 provide a mechanism to request a certificate post-handshake. Servers only.
450 B<RequiresPostHandshake> configures the connection to support requests and
451 requires a certificate from the client post-handshake: an error occurs if the
452 client does not present a certificate. A certificate will not be requested
453 during the initial handshake. The server application must provide a mechanism
454 to request a certificate post-handshake. Servers only. TLSv1.3 only.
456 =item B<ClientCAFile>, B<ClientCAPath>
458 A file or directory of certificates in PEM format whose names are used as the
459 set of acceptable names for client CAs. Servers only. This option is only
460 supported if certificate operations are permitted.
464 =head1 SUPPORTED COMMAND TYPES
466 The function SSL_CONF_cmd_value_type() currently returns one of the following
471 =item B<SSL_CONF_TYPE_UNKNOWN>
473 The B<cmd> string is unrecognised, this return value can be use to flag
476 =item B<SSL_CONF_TYPE_STRING>
478 The value is a string without any specific structure.
480 =item B<SSL_CONF_TYPE_FILE>
482 The value is a file name.
484 =item B<SSL_CONF_TYPE_DIR>
486 The value is a directory name.
488 =item B<SSL_CONF_TYPE_NONE>
490 The value string is not used e.g. a command line option which doesn't take an
497 The order of operations is significant. This can be used to set either defaults
498 or values which cannot be overridden. For example if an application calls:
500 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
501 SSL_CONF_cmd(ctx, userparam, uservalue);
503 it will disable SSLv3 support by default but the user can override it. If
504 however the call sequence is:
506 SSL_CONF_cmd(ctx, userparam, uservalue);
507 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
509 SSLv3 is B<always> disabled and attempt to override this by the user are
512 By checking the return code of SSL_CONF_cmd() it is possible to query if a
513 given B<cmd> is recognised, this is useful if SSL_CONF_cmd() values are
514 mixed with additional application specific operations.
516 For example an application might call SSL_CONF_cmd() and if it returns
517 -2 (unrecognised command) continue with processing of application specific
520 Applications can also use SSL_CONF_cmd() to process command lines though the
521 utility function SSL_CONF_cmd_argv() is normally used instead. One way
522 to do this is to set the prefix to an appropriate value using
523 SSL_CONF_CTX_set1_prefix(), pass the current argument to B<cmd> and the
524 following argument to B<value> (which may be NULL).
526 In this case if the return value is positive then it is used to skip that
527 number of arguments as they have been processed by SSL_CONF_cmd(). If -2 is
528 returned then B<cmd> is not recognised and application specific arguments
529 can be checked instead. If -3 is returned a required argument is missing
530 and an error is indicated. If 0 is returned some other error occurred and
531 this can be reported back to the user.
533 The function SSL_CONF_cmd_value_type() can be used by applications to
534 check for the existence of a command or to perform additional syntax
535 checking or translation of the command value. For example if the return
536 value is B<SSL_CONF_TYPE_FILE> an application could translate a relative
537 pathname to an absolute pathname.
541 Set supported signature algorithms:
543 SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256");
545 There are various ways to select the supported protocols.
547 This set the minimum protocol version to TLSv1, and so disables SSLv3.
548 This is the recommended way to disable protocols.
550 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1");
552 The following also disables SSLv3:
554 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
556 The following will first enable all protocols, and then disable
558 If no protocol versions were disabled before this has the same effect as
559 "-SSLv3", but if some versions were disables this will re-enable them before
562 SSL_CONF_cmd(ctx, "Protocol", "ALL,-SSLv3");
566 SSL_CONF_cmd(ctx, "MinProtocol", "TLSv1.2");
567 SSL_CONF_cmd(ctx, "MaxProtocol", "TLSv1.2");
569 This also only enables TLSv1.2:
571 SSL_CONF_cmd(ctx, "Protocol", "-ALL,TLSv1.2");
573 Disable TLS session tickets:
575 SSL_CONF_cmd(ctx, "Options", "-SessionTicket");
579 SSL_CONF_cmd(ctx, "Options", "Compression");
581 Set supported curves to P-256, P-384:
583 SSL_CONF_cmd(ctx, "Curves", "P-256:P-384");
585 Set automatic support for any elliptic curve for key exchange:
587 SSL_CONF_cmd(ctx, "ECDHParameters", "Automatic");
591 SSL_CONF_cmd() returns 1 if the value of B<cmd> is recognised and B<value> is
592 B<NOT> used and 2 if both B<cmd> and B<value> are used. In other words it
593 returns the number of arguments processed. This is useful when processing
596 A return value of -2 means B<cmd> is not recognised.
598 A return value of -3 means B<cmd> is recognised and the command requires a
599 value but B<value> is NULL.
601 A return code of 0 indicates that both B<cmd> and B<value> are valid but an
602 error occurred attempting to perform the operation: for example due to an
603 error in the syntax of B<value> in this case the error queue may provide
604 additional information.
608 L<SSL_CONF_CTX_new(3)>,
609 L<SSL_CONF_CTX_set_flags(3)>,
610 L<SSL_CONF_CTX_set1_prefix(3)>,
611 L<SSL_CONF_CTX_set_ssl_ctx(3)>,
612 L<SSL_CONF_cmd_argv(3)>,
613 L<SSL_CTX_set_options(3)>
617 SSL_CONF_cmd() was first added to OpenSSL 1.0.2
619 B<SSL_OP_NO_SSL2> doesn't have effect since 1.1.0, but the macro is retained
620 for backwards compatibility.
622 B<SSL_CONF_TYPE_NONE> was first added to OpenSSL 1.1.0. In earlier versions of
623 OpenSSL passing a command which didn't take an argument would return
624 B<SSL_CONF_TYPE_UNKNOWN>.
626 B<MinProtocol> and B<MaxProtocol> where added in OpenSSL 1.1.0.
628 B<AllowNoDHEKEX> and B<PrioritizeChaCha> were added in OpenSSL 1.1.1.
632 Copyright 2012-2018 The OpenSSL Project Authors. All Rights Reserved.
634 Licensed under the OpenSSL license (the "License"). You may not use
635 this file except in compliance with the License. You can obtain a copy
636 in the file LICENSE in the source distribution or at
637 L<https://www.openssl.org/source/license.html>.