5 SSL_CONF_cmd - send configuration command
9 #include <openssl/ssl.h>
11 int SSL_CONF_cmd(SSL_CONF_CTX *cctx, const char *cmd, const char *value);
12 int SSL_CONF_cmd_value_type(SSL_CONF_CTX *cctx, const char *cmd);
13 int SSL_CONF_finish(SSL_CONF_CTX *cctx);
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 The function SSL_CONF_finish() must be called after all configuration
25 operations have been completed. It is used to finalise any operations
26 or to process defaults.
28 =head1 SUPPORTED COMMAND LINE COMMANDS
30 Currently supported B<cmd> names for command lines (i.e. when the
31 flag B<SSL_CONF_CMDLINE> is set) are listed below. Note: all B<cmd> names
32 are case sensitive. Unless otherwise stated commands can be used by
33 both clients and servers and the B<value> parameter is not used. The default
34 prefix for command line commands is B<-> and that is reflected below.
40 This sets the supported signature algorithms for TLS v1.2. For clients this
41 value is used directly for the supported signature algorithms extension. For
42 servers it is used to determine which signature algorithms to support.
44 The B<value> argument should be a colon separated list of signature algorithms
45 in order of decreasing preference of the form B<algorithm+hash>. B<algorithm>
46 is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
47 OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
48 Note: algorithm and hash names are case sensitive.
50 If this option is not set then all signature algorithms supported by the
51 OpenSSL library are permissible.
53 =item B<-client_sigalgs>
55 This sets the supported signature algorithms associated with client
56 authentication for TLS v1.2. For servers the value is used in the supported
57 signature algorithms field of a certificate request. For clients it is
58 used to determine which signature algorithm to with the client certificate.
59 If a server does not request a certificate this option has no effect.
61 The syntax of B<value> is identical to B<-sigalgs>. If not set then
62 the value set for B<-sigalgs> will be used instead.
66 This sets the supported elliptic curves. For clients the curves are
67 sent using the supported curves extension. For servers it is used
68 to determine which curve to use. This setting affects curves used for both
69 signatures and key exchange, if applicable.
71 The B<value> argument is a colon separated list of curves. The curve can be
72 either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name (e.g
73 B<prime256v1>). Curve names are case sensitive.
77 This sets the temporary curve used for ephemeral ECDH modes. Only used by
80 The B<value> argument is a curve name or the special value B<auto> which
81 picks an appropriate curve based on client and server preferences. The curve
82 can be either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name
83 (e.g B<prime256v1>). Curve names are case sensitive.
87 Sets the cipher suite list to B<value>. Note: syntax checking of B<value> is
88 currently not performed unless a B<SSL> or B<SSL_CTX> structure is
89 associated with B<cctx>.
93 Attempts to use the file B<value> as the certificate for the appropriate
94 context. It currently uses SSL_CTX_use_cerificate_chain_file if an B<SSL_CTX>
95 structure is set or SSL_use_certifcate_file with filetype PEM if an B<SSL>
96 structure is set. This option is only supported if certificate operations
101 Attempts to use the file B<value> as the private key for the appropriate
102 context. This option is only supported if certificate operations
103 are permitted. Note: if no B<-key> option is set then a private key is
104 not loaded: it does not currently use the B<-cert> file.
108 Attempts to use the file B<value> as the set of temporary DH parameters for
109 the appropriate context. This option is only supported if certificate
110 operations are permitted.
112 =item B<-no_ssl2>, B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>
114 Disables protocol support for SSLv2, SSLv3, TLS 1.0, TLS 1.1 or TLS 1.2
115 by setting the corresponding options B<SSL_OP_NO_SSL2>, B<SSL_OP_NO_SSL3>,
116 B<SSL_OP_NO_TLS1>, B<SSL_OP_NO_TLS1_1> and B<SSL_OP_NO_TLS1_2> respectively.
120 Various bug workarounds are set, same as setting B<SSL_OP_ALL>.
124 Disables support for SSL/TLS compression, same as setting B<SSL_OP_NO_COMPRESS>.
128 Disables support for session tickets, same as setting B<SSL_OP_NO_TICKET>.
132 Use server and not client preference order when determining which cipher suite,
133 signature algorithm or elliptic curve to use for an incoming connection.
134 Equivalent to B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
136 =item B<-legacyrenegotiation>
138 permits the use of unsafe legacy renegotiation. Equivalent to setting
139 B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
141 =item B<-legacy_server_connect>, B<-no_legacy_server_connect>
143 permits or prohibits the use of unsafe legacy renegotiation for OpenSSL
144 clients only. Equivalent to setting or clearing B<SSL_OP_LEGACY_SERVER_CONNECT>.
149 enables strict mode protocol handling. Equivalent to setting
150 B<SSL_CERT_FLAG_TLS_STRICT>.
152 =item B<-debug_broken_protocol>
154 disables various checks and permits several kinds of broken protocol behaviour
155 for testing purposes: it should B<NEVER> be used in anything other than a test
156 environment. Only supported if OpenSSL is configured with
157 B<-DOPENSSL_SSL_DEBUG_BROKEN_PROTOCOL>.
161 =head1 SUPPORTED CONFIGURATION FILE COMMANDS
163 Currently supported B<cmd> names for configuration files (i.e. when the
164 flag B<SSL_CONF_FLAG_FILE> is set) are listed below. All configuration file
165 B<cmd> names and are case insensitive so B<signaturealgorithms> is recognised
166 as well as B<SignatureAlgorithms>. Unless otherwise stated the B<value> names
167 are also case insensitive.
169 Note: the command prefix (if set) alters the recognised B<cmd> values.
173 =item B<CipherString>
175 Sets the cipher suite list to B<value>. Note: syntax checking of B<value> is
176 currently not performed unless an B<SSL> or B<SSL_CTX> structure is
177 associated with B<cctx>.
181 Attempts to use the file B<value> as the certificate for the appropriate
182 context. It currently uses SSL_CTX_use_cerificate_chain_file if an B<SSL_CTX>
183 structure is set or SSL_use_certifcate_file with filetype PEM if an B<SSL>
184 structure is set. This option is only supported if certificate operations
189 Attempts to use the file B<value> as the private key for the appropriate
190 context. This option is only supported if certificate operations
191 are permitted. Note: if no B<-key> option is set then a private key is
192 not loaded: it does not currently use the B<Certificate> file.
194 =item B<DHParameters>
196 Attempts to use the file B<value> as the set of temporary DH parameters for
197 the appropriate context. This option is only supported if certificate
198 operations are permitted.
200 =item B<SignatureAlgorithms>
202 This sets the supported signature algorithms for TLS v1.2. For clients this
203 value is used directly for the supported signature algorithms extension. For
204 servers it is used to determine which signature algorithms to support.
206 The B<value> argument should be a colon separated list of signature algorithms
207 in order of decreasing preference of the form B<algorithm+hash>. B<algorithm>
208 is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
209 OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
210 Note: algorithm and hash names are case sensitive.
212 If this option is not set then all signature algorithms supported by the
213 OpenSSL library are permissible.
215 =item B<ClientSignatureAlgorithms>
217 This sets the supported signature algorithms associated with client
218 authentication for TLS v1.2. For servers the value is used in the supported
219 signature algorithms field of a certificate request. For clients it is
220 used to determine which signature algorithm to with the client certificate.
222 The syntax of B<value> is identical to B<SignatureAlgorithms>. If not set then
223 the value set for B<SignatureAlgorithms> will be used instead.
227 This sets the supported elliptic curves. For clients the curves are
228 sent using the supported curves extension. For servers it is used
229 to determine which curve to use. This setting affects curves used for both
230 signatures and key exchange, if applicable.
232 The B<value> argument is a colon separated list of curves. The curve can be
233 either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name (e.g
234 B<prime256v1>). Curve names are case sensitive.
236 =item B<ECDHParameters>
238 This sets the temporary curve used for ephemeral ECDH modes. Only used by
241 The B<value> argument is a curve name or the special value B<Automatic> which
242 picks an appropriate curve based on client and server preferences. The curve
243 can be either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name
244 (e.g B<prime256v1>). Curve names are case sensitive.
248 The supported versions of the SSL or TLS protocol.
250 The B<value> argument is a comma separated list of supported protocols to
251 enable or disable. If an protocol is preceded by B<-> that version is disabled.
252 All versions are enabled by default, though applications may choose to
253 explicitly disable some. Currently supported protocol values are B<SSLv2>,
254 B<SSLv3>, B<TLSv1>, B<TLSv1.1> and B<TLSv1.2>. The special value B<ALL> refers
255 to all supported versions.
259 The B<value> argument is a comma separated list of various flags to set.
260 If a flag string is preceded B<-> it is disabled. See the
261 B<SSL_CTX_set_options> function for more details of individual options.
263 Each option is listed below. Where an operation is enabled by default
264 the B<-flag> syntax is needed to disable it.
266 B<SessionTicket>: session ticket support, enabled by default. Inverse of
267 B<SSL_OP_NO_TICKET>: that is B<-SessionTicket> is the same as setting
270 B<Compression>: SSL/TLS compression support, enabled by default. Inverse
271 of B<SSL_OP_NO_COMPRESSION>.
273 B<EmptyFragments>: use empty fragments as a countermeasure against a
274 SSL 3.0/TLS 1.0 protocol vulnerability affecting CBC ciphers. It
275 is set by default. Inverse of B<SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS>.
277 B<Bugs>: enable various bug workarounds. Same as B<SSL_OP_ALL>.
279 B<DHSingle>: enable single use DH keys, set by default. Inverse of
280 B<SSL_OP_DH_SINGLE>. Only used by servers.
282 B<ECDHSingle> enable single use ECDH keys, set by default. Inverse of
283 B<SSL_OP_ECDH_SINGLE>. Only used by servers.
285 B<ServerPreference> use server and not client preference order when
286 determining which cipher suite, signature algorithm or elliptic curve
287 to use for an incoming connection. Equivalent to
288 B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
290 B<UnsafeLegacyRenegotiation> permits the use of unsafe legacy renegotiation.
291 Equivalent to B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
293 B<UnsafeLegacyServerConnect> permits the use of unsafe legacy renegotiation
294 for OpenSSL clients only. Equivalent to B<SSL_OP_LEGACY_SERVER_CONNECT>.
299 =head1 SUPPORTED COMMAND TYPES
301 The function SSL_CONF_cmd_value_type() currently returns one of the following
306 =item B<SSL_CONF_TYPE_UNKNOWN>
308 The B<cmd> string is unrecognised, this return value can be use to flag
311 =item B<SSL_CONF_TYPE_STRING>
313 The value is a string without any specific structure.
315 =item B<SSL_CONF_TYPE_FILE>
317 The value is a file name.
319 =item B<SSL_CONF_TYPE_DIR>
321 The value is a directory name.
325 The order of operations is significant. This can be used to set either defaults
326 or values which cannot be overridden. For example if an application calls:
328 SSL_CONF_cmd(ctx, "Protocol", "-SSLv2");
329 SSL_CONF_cmd(ctx, userparam, uservalue);
331 it will disable SSLv2 support by default but the user can override it. If
332 however the call sequence is:
334 SSL_CONF_cmd(ctx, userparam, uservalue);
335 SSL_CONF_cmd(ctx, "Protocol", "-SSLv2");
337 SSLv2 is B<always> disabled and attempt to override this by the user are
340 By checking the return code of SSL_CTX_cmd() it is possible to query if a
341 given B<cmd> is recognised, this is useful is SSL_CTX_cmd() values are
342 mixed with additional application specific operations.
344 For example an application might call SSL_CTX_cmd() and if it returns
345 -2 (unrecognised command) continue with processing of application specific
348 Applications can also use SSL_CTX_cmd() to process command lines though the
349 utility function SSL_CTX_cmd_argv() is normally used instead. One way
350 to do this is to set the prefix to an appropriate value using
351 SSL_CONF_CTX_set1_prefix(), pass the current argument to B<cmd> and the
352 following argument to B<value> (which may be NULL).
354 In this case if the return value is positive then it is used to skip that
355 number of arguments as they have been processed by SSL_CTX_cmd(). If -2 is
356 returned then B<cmd> is not recognised and application specific arguments
357 can be checked instead. If -3 is returned a required argument is missing
358 and an error is indicated. If 0 is returned some other error occurred and
359 this can be reported back to the user.
361 The function SSL_CONF_cmd_value_type() can be used by applications to
362 check for the existence of a command or to perform additional syntax
363 checking or translation of the command value. For example if the return
364 value is B<SSL_CONF_TYPE_FILE> an application could translate a relative
365 pathname to an absolute pathname.
369 Set supported signature algorithms:
371 SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256");
373 Enable all protocols except SSLv3 and SSLv2:
375 SSL_CONF_cmd(ctx, "Protocol", "ALL,-SSLv3,-SSLv2");
379 SSL_CONF_cmd(ctx, "Protocol", "-ALL,TLSv1.2");
381 Disable TLS session tickets:
383 SSL_CONF_cmd(ctx, "Options", "-SessionTicket");
385 Set supported curves to P-256, P-384:
387 SSL_CONF_cmd(ctx, "Curves", "P-256:P-384");
389 Set automatic support for any elliptic curve for key exchange:
391 SSL_CONF_cmd(ctx, "ECDHParameters", "Automatic");
395 SSL_CONF_cmd() returns 1 if the value of B<cmd> is recognised and B<value> is
396 B<NOT> used and 2 if both B<cmd> and B<value> are used. In other words it
397 returns the number of arguments processed. This is useful when processing
400 A return value of -2 means B<cmd> is not recognised.
402 A return value of -3 means B<cmd> is recognised and the command requires a
403 value but B<value> is NULL.
405 A return code of 0 indicates that both B<cmd> and B<value> are valid but an
406 error occurred attempting to perform the operation: for example due to an
407 error in the syntax of B<value> in this case the error queue may provide
408 additional information.
410 SSL_CONF_finish() returns 1 for success and 0 for failure.
414 L<SSL_CONF_CTX_new(3)|SSL_CONF_CTX_new(3)>,
415 L<SSL_CONF_CTX_set_flags(3)|SSL_CONF_CTX_set_flags(3)>,
416 L<SSL_CONF_CTX_set1_prefix(3)|SSL_CONF_CTX_set1_prefix(3)>,
417 L<SSL_CONF_CTX_set_ssl_ctx(3)|SSL_CONF_CTX_set_ssl_ctx(3)>,
418 L<SSL_CONF_cmd_argv(3)|SSL_CONF_cmd_argv(3)>
422 SSL_CONF_cmd() was first added to OpenSSL 1.0.2