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_certificate_chain_file() if an B<SSL_CTX>
95 structure is set or SSL_use_certificate_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, TLSv1.0, TLSv1.1 or TLSv1.2
115 by setting the corresponding options B<SSL_OP_NO_SSLv2>, B<SSL_OP_NO_SSLv3>,
116 B<SSL_OP_NO_TLSv1>, B<SSL_OP_NO_TLSv1_1> and B<SSL_OP_NO_TLSv1_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_certificate_chain_file() if an B<SSL_CTX>
187 structure is set or SSL_use_certificate_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<ServerInfoFile>
200 Attempts to use the file B<value> in the "serverinfo" extension using the
201 function SSL_CTX_use_serverinfo_file.
203 =item B<DHParameters>
205 Attempts to use the file B<value> as the set of temporary DH parameters for
206 the appropriate context. This option is only supported if certificate
207 operations are permitted.
209 =item B<SignatureAlgorithms>
211 This sets the supported signature algorithms for TLS v1.2. For clients this
212 value is used directly for the supported signature algorithms extension. For
213 servers it is used to determine which signature algorithms to support.
215 The B<value> argument should be a colon separated list of signature algorithms
216 in order of decreasing preference of the form B<algorithm+hash>. B<algorithm>
217 is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
218 OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
219 Note: algorithm and hash names are case sensitive.
221 If this option is not set then all signature algorithms supported by the
222 OpenSSL library are permissible.
224 =item B<ClientSignatureAlgorithms>
226 This sets the supported signature algorithms associated with client
227 authentication for TLS v1.2. For servers the value is used in the supported
228 signature algorithms field of a certificate request. For clients it is
229 used to determine which signature algorithm to with the client certificate.
231 The syntax of B<value> is identical to B<SignatureAlgorithms>. If not set then
232 the value set for B<SignatureAlgorithms> will be used instead.
236 This sets the supported elliptic curves. For clients the curves are
237 sent using the supported curves extension. For servers it is used
238 to determine which curve to use. This setting affects curves used for both
239 signatures and key exchange, if applicable.
241 The B<value> argument is a colon separated list of curves. The curve can be
242 either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name (e.g
243 B<prime256v1>). Curve names are case sensitive.
245 =item B<ECDHParameters>
247 This sets the temporary curve used for ephemeral ECDH modes. Only used by
250 The B<value> argument is a curve name or the special value B<Automatic> which
251 picks an appropriate curve based on client and server preferences. The curve
252 can be either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name
253 (e.g B<prime256v1>). Curve names are case sensitive.
257 The supported versions of the SSL or TLS protocol.
259 The B<value> argument is a comma separated list of supported protocols to
260 enable or disable. If an protocol is preceded by B<-> that version is disabled.
261 Currently supported protocol values are B<SSLv2>, B<SSLv3>, B<TLSv1>,
262 B<TLSv1.1> and B<TLSv1.2>.
263 All protocol versions other than B<SSLv2> are enabled by default.
264 To avoid inadvertent enabling of B<SSLv2>, when SSLv2 is disabled, it is not
265 possible to enable it via the B<Protocol> command.
269 The B<value> argument is a comma separated list of various flags to set.
270 If a flag string is preceded B<-> it is disabled. See the
271 B<SSL_CTX_set_options> function for more details of individual options.
273 Each option is listed below. Where an operation is enabled by default
274 the B<-flag> syntax is needed to disable it.
276 B<SessionTicket>: session ticket support, enabled by default. Inverse of
277 B<SSL_OP_NO_TICKET>: that is B<-SessionTicket> is the same as setting
280 B<Compression>: SSL/TLS compression support, enabled by default. Inverse
281 of B<SSL_OP_NO_COMPRESSION>.
283 B<EmptyFragments>: use empty fragments as a countermeasure against a
284 SSL 3.0/TLS 1.0 protocol vulnerability affecting CBC ciphers. It
285 is set by default. Inverse of B<SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS>.
287 B<Bugs>: enable various bug workarounds. Same as B<SSL_OP_ALL>.
289 B<DHSingle>: enable single use DH keys, set by default. Inverse of
290 B<SSL_OP_DH_SINGLE>. Only used by servers.
292 B<ECDHSingle> enable single use ECDH keys, set by default. Inverse of
293 B<SSL_OP_ECDH_SINGLE>. Only used by servers.
295 B<ServerPreference> use server and not client preference order when
296 determining which cipher suite, signature algorithm or elliptic curve
297 to use for an incoming connection. Equivalent to
298 B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
300 B<NoResumptionOnRenegotiation> set
301 B<SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION> flag. Only used by servers.
303 B<UnsafeLegacyRenegotiation> permits the use of unsafe legacy renegotiation.
304 Equivalent to B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
306 B<UnsafeLegacyServerConnect> permits the use of unsafe legacy renegotiation
307 for OpenSSL clients only. Equivalent to B<SSL_OP_LEGACY_SERVER_CONNECT>.
312 =head1 SUPPORTED COMMAND TYPES
314 The function SSL_CONF_cmd_value_type() currently returns one of the following
319 =item B<SSL_CONF_TYPE_UNKNOWN>
321 The B<cmd> string is unrecognised, this return value can be use to flag
324 =item B<SSL_CONF_TYPE_STRING>
326 The value is a string without any specific structure.
328 =item B<SSL_CONF_TYPE_FILE>
330 The value is a file name.
332 =item B<SSL_CONF_TYPE_DIR>
334 The value is a directory name.
340 The order of operations is significant. This can be used to set either defaults
341 or values which cannot be overridden. For example if an application calls:
343 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
344 SSL_CONF_cmd(ctx, userparam, uservalue);
346 it will disable SSLv3 support by default but the user can override it. If
347 however the call sequence is:
349 SSL_CONF_cmd(ctx, userparam, uservalue);
350 SSL_CONF_cmd(ctx, "Protocol", "-SSLv3");
352 then SSLv3 is B<always> disabled and attempt to override this by the user are
355 By checking the return code of SSL_CTX_cmd() it is possible to query if a
356 given B<cmd> is recognised, this is useful is SSL_CTX_cmd() values are
357 mixed with additional application specific operations.
359 For example an application might call SSL_CTX_cmd() and if it returns
360 -2 (unrecognised command) continue with processing of application specific
363 Applications can also use SSL_CTX_cmd() to process command lines though the
364 utility function SSL_CTX_cmd_argv() is normally used instead. One way
365 to do this is to set the prefix to an appropriate value using
366 SSL_CONF_CTX_set1_prefix(), pass the current argument to B<cmd> and the
367 following argument to B<value> (which may be NULL).
369 In this case if the return value is positive then it is used to skip that
370 number of arguments as they have been processed by SSL_CTX_cmd(). If -2 is
371 returned then B<cmd> is not recognised and application specific arguments
372 can be checked instead. If -3 is returned a required argument is missing
373 and an error is indicated. If 0 is returned some other error occurred and
374 this can be reported back to the user.
376 The function SSL_CONF_cmd_value_type() can be used by applications to
377 check for the existence of a command or to perform additional syntax
378 checking or translation of the command value. For example if the return
379 value is B<SSL_CONF_TYPE_FILE> an application could translate a relative
380 pathname to an absolute pathname.
384 Set supported signature algorithms:
386 SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256");
388 Enable all protocols except SSLv3 and SSLv2:
390 SSL_CONF_cmd(ctx, "Protocol", "ALL,-SSLv3,-SSLv2");
394 SSL_CONF_cmd(ctx, "Protocol", "-ALL,TLSv1.2");
396 Disable TLS session tickets:
398 SSL_CONF_cmd(ctx, "Options", "-SessionTicket");
400 Set supported curves to P-256, P-384:
402 SSL_CONF_cmd(ctx, "Curves", "P-256:P-384");
404 Set automatic support for any elliptic curve for key exchange:
406 SSL_CONF_cmd(ctx, "ECDHParameters", "Automatic");
410 SSL_CONF_cmd() returns 1 if the value of B<cmd> is recognised and B<value> is
411 B<NOT> used and 2 if both B<cmd> and B<value> are used. In other words it
412 returns the number of arguments processed. This is useful when processing
415 A return value of -2 means B<cmd> is not recognised.
417 A return value of -3 means B<cmd> is recognised and the command requires a
418 value but B<value> is NULL.
420 A return code of 0 indicates that both B<cmd> and B<value> are valid but an
421 error occurred attempting to perform the operation: for example due to an
422 error in the syntax of B<value> in this case the error queue may provide
423 additional information.
425 SSL_CONF_finish() returns 1 for success and 0 for failure.
429 L<SSL_CONF_CTX_new(3)|SSL_CONF_CTX_new(3)>,
430 L<SSL_CONF_CTX_set_flags(3)|SSL_CONF_CTX_set_flags(3)>,
431 L<SSL_CONF_CTX_set1_prefix(3)|SSL_CONF_CTX_set1_prefix(3)>,
432 L<SSL_CONF_CTX_set_ssl_ctx(3)|SSL_CONF_CTX_set_ssl_ctx(3)>,
433 L<SSL_CONF_cmd_argv(3)|SSL_CONF_cmd_argv(3)>
437 SSL_CONF_cmd() was first added to OpenSSL 1.0.2