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<-no_resumption_on_reneg>
138 set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag. Only used by servers.
140 =item B<-legacyrenegotiation>
142 permits the use of unsafe legacy renegotiation. Equivalent to setting
143 B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
145 =item B<-legacy_server_connect>, B<-no_legacy_server_connect>
147 permits or prohibits the use of unsafe legacy renegotiation for OpenSSL
148 clients only. Equivalent to setting or clearing B<SSL_OP_LEGACY_SERVER_CONNECT>.
153 enables strict mode protocol handling. Equivalent to setting
154 B<SSL_CERT_FLAG_TLS_STRICT>.
156 =item B<-debug_broken_protocol>
158 disables various checks and permits several kinds of broken protocol behaviour
159 for testing purposes: it should B<NEVER> be used in anything other than a test
160 environment. Only supported if OpenSSL is configured with
161 B<-DOPENSSL_SSL_DEBUG_BROKEN_PROTOCOL>.
165 =head1 SUPPORTED CONFIGURATION FILE COMMANDS
167 Currently supported B<cmd> names for configuration files (i.e. when the
168 flag B<SSL_CONF_FLAG_FILE> is set) are listed below. All configuration file
169 B<cmd> names and are case insensitive so B<signaturealgorithms> is recognised
170 as well as B<SignatureAlgorithms>. Unless otherwise stated the B<value> names
171 are also case insensitive.
173 Note: the command prefix (if set) alters the recognised B<cmd> values.
177 =item B<CipherString>
179 Sets the cipher suite list to B<value>. Note: syntax checking of B<value> is
180 currently not performed unless an B<SSL> or B<SSL_CTX> structure is
181 associated with B<cctx>.
185 Attempts to use the file B<value> as the certificate for the appropriate
186 context. It currently uses SSL_CTX_use_cerificate_chain_file if an B<SSL_CTX>
187 structure is set or SSL_use_certifcate_file with filetype PEM if an B<SSL>
188 structure is set. This option is only supported if certificate operations
193 Attempts to use the file B<value> as the private key for the appropriate
194 context. This option is only supported if certificate operations
195 are permitted. Note: if no B<-key> option is set then a private key is
196 not loaded: it does not currently use the B<Certificate> file.
198 =item B<DHParameters>
200 Attempts to use the file B<value> as the set of temporary DH parameters for
201 the appropriate context. This option is only supported if certificate
202 operations are permitted.
204 =item B<SignatureAlgorithms>
206 This sets the supported signature algorithms for TLS v1.2. For clients this
207 value is used directly for the supported signature algorithms extension. For
208 servers it is used to determine which signature algorithms to support.
210 The B<value> argument should be a colon separated list of signature algorithms
211 in order of decreasing preference of the form B<algorithm+hash>. B<algorithm>
212 is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
213 OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
214 Note: algorithm and hash names are case sensitive.
216 If this option is not set then all signature algorithms supported by the
217 OpenSSL library are permissible.
219 =item B<ClientSignatureAlgorithms>
221 This sets the supported signature algorithms associated with client
222 authentication for TLS v1.2. For servers the value is used in the supported
223 signature algorithms field of a certificate request. For clients it is
224 used to determine which signature algorithm to with the client certificate.
226 The syntax of B<value> is identical to B<SignatureAlgorithms>. If not set then
227 the value set for B<SignatureAlgorithms> will be used instead.
231 This sets the supported elliptic curves. For clients the curves are
232 sent using the supported curves extension. For servers it is used
233 to determine which curve to use. This setting affects curves used for both
234 signatures and key exchange, if applicable.
236 The B<value> argument is a colon separated list of curves. The curve can be
237 either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name (e.g
238 B<prime256v1>). Curve names are case sensitive.
240 =item B<ECDHParameters>
242 This sets the temporary curve used for ephemeral ECDH modes. Only used by
245 The B<value> argument is a curve name or the special value B<Automatic> which
246 picks an appropriate curve based on client and server preferences. The curve
247 can be either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name
248 (e.g B<prime256v1>). Curve names are case sensitive.
252 The supported versions of the SSL or TLS protocol.
254 The B<value> argument is a comma separated list of supported protocols to
255 enable or disable. If an protocol is preceded by B<-> that version is disabled.
256 All versions are enabled by default, though applications may choose to
257 explicitly disable some. Currently supported protocol values are B<SSLv2>,
258 B<SSLv3>, B<TLSv1>, B<TLSv1.1> and B<TLSv1.2>. The special value B<ALL> refers
259 to all supported versions.
263 The B<value> argument is a comma separated list of various flags to set.
264 If a flag string is preceded B<-> it is disabled. See the
265 B<SSL_CTX_set_options> function for more details of individual options.
267 Each option is listed below. Where an operation is enabled by default
268 the B<-flag> syntax is needed to disable it.
270 B<SessionTicket>: session ticket support, enabled by default. Inverse of
271 B<SSL_OP_NO_TICKET>: that is B<-SessionTicket> is the same as setting
274 B<Compression>: SSL/TLS compression support, enabled by default. Inverse
275 of B<SSL_OP_NO_COMPRESSION>.
277 B<EmptyFragments>: use empty fragments as a countermeasure against a
278 SSL 3.0/TLS 1.0 protocol vulnerability affecting CBC ciphers. It
279 is set by default. Inverse of B<SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS>.
281 B<Bugs>: enable various bug workarounds. Same as B<SSL_OP_ALL>.
283 B<DHSingle>: enable single use DH keys, set by default. Inverse of
284 B<SSL_OP_DH_SINGLE>. Only used by servers.
286 B<ECDHSingle> enable single use ECDH keys, set by default. Inverse of
287 B<SSL_OP_ECDH_SINGLE>. Only used by servers.
289 B<ServerPreference> use server and not client preference order when
290 determining which cipher suite, signature algorithm or elliptic curve
291 to use for an incoming connection. Equivalent to
292 B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
294 B<NoResumptionOnRenegotiation> set
295 B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> flag. Only used by servers.
297 B<UnsafeLegacyRenegotiation> permits the use of unsafe legacy renegotiation.
298 Equivalent to B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
300 B<UnsafeLegacyServerConnect> permits the use of unsafe legacy renegotiation
301 for OpenSSL clients only. Equivalent to B<SSL_OP_LEGACY_SERVER_CONNECT>.
306 =head1 SUPPORTED COMMAND TYPES
308 The function SSL_CONF_cmd_value_type() currently returns one of the following
313 =item B<SSL_CONF_TYPE_UNKNOWN>
315 The B<cmd> string is unrecognised, this return value can be use to flag
318 =item B<SSL_CONF_TYPE_STRING>
320 The value is a string without any specific structure.
322 =item B<SSL_CONF_TYPE_FILE>
324 The value is a file name.
326 =item B<SSL_CONF_TYPE_DIR>
328 The value is a directory name.
334 The order of operations is significant. This can be used to set either defaults
335 or values which cannot be overridden. For example if an application calls:
337 SSL_CONF_cmd(ctx, "Protocol", "-SSLv2");
338 SSL_CONF_cmd(ctx, userparam, uservalue);
340 it will disable SSLv2 support by default but the user can override it. If
341 however the call sequence is:
343 SSL_CONF_cmd(ctx, userparam, uservalue);
344 SSL_CONF_cmd(ctx, "Protocol", "-SSLv2");
346 SSLv2 is B<always> disabled and attempt to override this by the user are
349 By checking the return code of SSL_CTX_cmd() it is possible to query if a
350 given B<cmd> is recognised, this is useful is SSL_CTX_cmd() values are
351 mixed with additional application specific operations.
353 For example an application might call SSL_CTX_cmd() and if it returns
354 -2 (unrecognised command) continue with processing of application specific
357 Applications can also use SSL_CTX_cmd() to process command lines though the
358 utility function SSL_CTX_cmd_argv() is normally used instead. One way
359 to do this is to set the prefix to an appropriate value using
360 SSL_CONF_CTX_set1_prefix(), pass the current argument to B<cmd> and the
361 following argument to B<value> (which may be NULL).
363 In this case if the return value is positive then it is used to skip that
364 number of arguments as they have been processed by SSL_CTX_cmd(). If -2 is
365 returned then B<cmd> is not recognised and application specific arguments
366 can be checked instead. If -3 is returned a required argument is missing
367 and an error is indicated. If 0 is returned some other error occurred and
368 this can be reported back to the user.
370 The function SSL_CONF_cmd_value_type() can be used by applications to
371 check for the existence of a command or to perform additional syntax
372 checking or translation of the command value. For example if the return
373 value is B<SSL_CONF_TYPE_FILE> an application could translate a relative
374 pathname to an absolute pathname.
378 Set supported signature algorithms:
380 SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256");
382 Enable all protocols except SSLv3 and SSLv2:
384 SSL_CONF_cmd(ctx, "Protocol", "ALL,-SSLv3,-SSLv2");
388 SSL_CONF_cmd(ctx, "Protocol", "-ALL,TLSv1.2");
390 Disable TLS session tickets:
392 SSL_CONF_cmd(ctx, "Options", "-SessionTicket");
394 Set supported curves to P-256, P-384:
396 SSL_CONF_cmd(ctx, "Curves", "P-256:P-384");
398 Set automatic support for any elliptic curve for key exchange:
400 SSL_CONF_cmd(ctx, "ECDHParameters", "Automatic");
404 SSL_CONF_cmd() returns 1 if the value of B<cmd> is recognised and B<value> is
405 B<NOT> used and 2 if both B<cmd> and B<value> are used. In other words it
406 returns the number of arguments processed. This is useful when processing
409 A return value of -2 means B<cmd> is not recognised.
411 A return value of -3 means B<cmd> is recognised and the command requires a
412 value but B<value> is NULL.
414 A return code of 0 indicates that both B<cmd> and B<value> are valid but an
415 error occurred attempting to perform the operation: for example due to an
416 error in the syntax of B<value> in this case the error queue may provide
417 additional information.
419 SSL_CONF_finish() returns 1 for success and 0 for failure.
423 L<SSL_CONF_CTX_new(3)|SSL_CONF_CTX_new(3)>,
424 L<SSL_CONF_CTX_set_flags(3)|SSL_CONF_CTX_set_flags(3)>,
425 L<SSL_CONF_CTX_set1_prefix(3)|SSL_CONF_CTX_set1_prefix(3)>,
426 L<SSL_CONF_CTX_set_ssl_ctx(3)|SSL_CONF_CTX_set_ssl_ctx(3)>,
427 L<SSL_CONF_cmd_argv(3)|SSL_CONF_cmd_argv(3)>
431 SSL_CONF_cmd() was first added to OpenSSL 1.0.2