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 and 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.
106 =item B<-no_ssl2>, B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>
108 Disables protocol support for SSLv2, SSLv3, TLS 1.0, TLS 1.1 or TLS 1.2
109 by setting the corresponding options B<SSL_OP_NO_SSL2>, B<SSL_OP_NO_SSL3>,
110 B<SSL_OP_NO_TLS1>, B<SSL_OP_NO_TLS1_1> and B<SSL_OP_NO_TLS1_2> respectively.
114 Various bug workarounds are set, same as setting B<SSL_OP_ALL>.
118 Disables support for SSL/TLS compression, same as setting B<SSL_OP_NO_COMPRESS>.
122 Disables support for session tickets, same as setting B<SSL_OP_NO_TICKET>.
126 Use server and not client preference order when determining which cipher suite,
127 signature algorithm or elliptic curve to use for an incoming connection.
128 Equivalent to B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
130 =item B<-legacyrenegotiation>
132 permits the use of unsafe legacy renegotiation. Equivalent to setting
133 B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
135 =item B<-legacy_server_connect>, B<-no_legacy_server_connect>
137 permits or prohibits the use of unsafe legacy renegotiation for OpenSSL
138 clients only. Equivalent to setting or clearing B<SSL_OP_LEGACY_SERVER_CONNECT>.
143 enables strict mode protocol handling. Equivalent to setting
144 B<SSL_CERT_FLAG_TLS_STRICT>.
146 =item B<-debug_broken_protocol>
148 disables various checks and permits several kinds of broken protocol behaviour
149 for testing purposes: it should B<NEVER> be used in anything other than a test
150 environment. Only supported if OpenSSL is configured with
151 B<-DOPENSSL_SSL_DEBUG_BROKEN_PROTOCOL>.
155 =head1 SUPPORTED CONFIGURATION FILE COMMANDS
157 Currently supported B<cmd> names for configuration files (i.e. when the
158 flag B<SSL_CONF_FLAG_FILE> is set) are listed below. All configuration file
159 B<cmd> names and are case insensitive so B<signaturealgorithms> is recognised
160 as well as B<SignatureAlgorithms>. Unless otherwise stated the B<value> names
161 are also case insensitive.
163 Note: the command prefix (if set) alters the recognised B<cmd> values.
167 =item B<CipherString>
169 Sets the cipher suite list to B<value>. Note: syntax checking of B<value> is
170 currently not performed unless an B<SSL> or B<SSL_CTX> structure is
171 associated with B<cctx>.
175 Attempts to use the file B<value> as the certificate for the appropriate
176 context. It currently uses SSL_CTX_use_cerificate_chain_file if an B<SSL_CTX>
177 structure is set or SSL_use_certifcate_file with filetype PEM if an B<SSL>
178 structure is set. This option is only supported if certificate operations
183 Attempts to use the file B<value> as the private key for the appropriate
184 context. This option is only supported if certificate operations
185 are permitted. Note: if no B<-key> option is set then a private key is
186 not loaded: it does not currently use the B<Certificate> file.
188 =item B<SignatureAlgorithms>
190 This sets the supported signature algorithms for TLS v1.2. For clients this
191 value is used directly for the supported signature algorithms extension. For
192 servers it is used to determine which signature algorithms to support.
194 The B<value> argument should be a colon separated list of signature algorithms
195 in order of decreasing preference of the form B<algorithm+hash>. B<algorithm>
196 is one of B<RSA>, B<DSA> or B<ECDSA> and B<hash> is a supported algorithm
197 OID short name such as B<SHA1>, B<SHA224>, B<SHA256>, B<SHA384> of B<SHA512>.
198 Note: algorithm and hash names are case sensitive.
200 If this option is not set then all signature algorithms supported by the
201 OpenSSL library are permissible.
203 =item B<ClientSignatureAlgorithms>
205 This sets the supported signature algorithms associated with client
206 authentication for TLS v1.2. For servers the value is used in the supported
207 signature algorithms field of a certificate request. For clients it is
208 used to determine which signature algorithm to with the client certificate.
210 The syntax of B<value> is identical to B<SignatureAlgorithms>. If not set then
211 the value set for B<SignatureAlgorithms> will be used instead.
215 This sets the supported elliptic curves. For clients the curves are
216 sent using the supported curves extension. For servers it is used
217 to determine which curve to use. This setting affects curves used for both
218 signatures and key exchange, if applicable.
220 The B<value> argument is a colon separated list of curves. The curve can be
221 either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name (e.g
222 B<prime256v1>). Curve names are case sensitive.
224 =item B<ECDHParameters>
226 This sets the temporary curve used for ephemeral ECDH modes. Only used by
229 The B<value> argument is a curve name or the special value B<Automatic> which
230 picks an appropriate curve based on client and server preferences. The curve
231 can be either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name
232 (e.g B<prime256v1>). Curve names are case sensitive.
236 The supported versions of the SSL or TLS protocol.
238 The B<value> argument is a comma separated list of supported protocols to
239 enable or disable. If an protocol is preceded by B<-> that version is disabled.
240 All versions are enabled by default, though applications may choose to
241 explicitly disable some. Currently supported protocol values are B<SSLv2>,
242 B<SSLv3>, B<TLSv1>, B<TLSv1.1> and B<TLSv1.2>. The special value B<ALL> refers
243 to all supported versions.
247 The B<value> argument is a comma separated list of various flags to set.
248 If a flag string is preceded B<-> it is disabled. See the
249 B<SSL_CTX_set_options> function for more details of individual options.
251 Each option is listed below. Where an operation is enabled by default
252 the B<-flag> syntax is needed to disable it.
254 B<SessionTicket>: session ticket support, enabled by default. Inverse of
255 B<SSL_OP_NO_TICKET>: that is B<-SessionTicket> is the same as setting
258 B<Compression>: SSL/TLS compression support, enabled by default. Inverse
259 of B<SSL_OP_NO_COMPRESSION>.
261 B<EmptyFragments>: use empty fragments as a countermeasure against a
262 SSL 3.0/TLS 1.0 protocol vulnerability affecting CBC ciphers. It
263 is set by default. Inverse of B<SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS>.
265 B<Bugs>: enable various bug workarounds. Same as B<SSL_OP_ALL>.
267 B<DHSingle>: enable single use DH keys, set by default. Inverse of
268 B<SSL_OP_DH_SINGLE>. Only used by servers.
270 B<ECDHSingle> enable single use ECDH keys, set by default. Inverse of
271 B<SSL_OP_ECDH_SINGLE>. Only used by servers.
273 B<ServerPreference> use server and not client preference order when
274 determining which cipher suite, signature algorithm or elliptic curve
275 to use for an incoming connection. Equivalent to
276 B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers.
278 B<UnsafeLegacyRenegotiation> permits the use of unsafe legacy renegotiation.
279 Equivalent to B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>.
281 B<UnsafeLegacyServerConnect> permits the use of unsafe legacy renegotiation
282 for OpenSSL clients only. Equivalent to B<SSL_OP_LEGACY_SERVER_CONNECT>.
287 =head1 SUPPORTED COMMAND TYPES
289 The function SSL_CONF_cmd_value_type() currently returns one of the following
294 =item B<SSL_CONF_TYPE_UNKNOWN>
296 The B<cmd> string is unrecognised, this return value can be use to flag
299 =item B<SSL_CONF_TYPE_STRING>
301 The value is a string without any specific structure.
303 =item B<SSL_CONF_TYPE_FILE>
305 The value is a file name.
307 =item B<SSL_CONF_TYPE_DIR>
309 The value is a directory name.
313 The order of operations is significant. This can be used to set either defaults
314 or values which cannot be overridden. For example if an application calls:
316 SSL_CONF_cmd(ctx, "Protocol", "-SSLv2");
317 SSL_CONF_cmd(ctx, userparam, uservalue);
319 it will disable SSLv2 support by default but the user can override it. If
320 however the call sequence is:
322 SSL_CONF_cmd(ctx, userparam, uservalue);
323 SSL_CONF_cmd(ctx, "Protocol", "-SSLv2");
325 SSLv2 is B<always> disabled and attempt to override this by the user are
328 By checking the return code of SSL_CTX_cmd() it is possible to query if a
329 given B<cmd> is recognised, this is useful is SSL_CTX_cmd() values are
330 mixed with additional application specific operations.
332 For example an application might call SSL_CTX_cmd() and if it returns
333 -2 (unrecognised command) continue with processing of application specific
336 Applications can also use SSL_CTX_cmd() to process command lines though the
337 utility function SSL_CTX_cmd_argv() is normally used instead. One way
338 to do this is to set the prefix to an appropriate value using
339 SSL_CONF_CTX_set1_prefix(), pass the current argument to B<cmd> and the
340 following argument to B<value> (which may be NULL).
342 In this case if the return value is positive then it is used to skip that
343 number of arguments as they have been processed by SSL_CTX_cmd(). If -2 is
344 returned then B<cmd> is not recognised and application specific arguments
345 can be checked instead. If -3 is returned a required argument is missing
346 and an error is indicated. If 0 is returned some other error occurred and
347 this can be reported back to the user.
349 The function SSL_CONF_cmd_value_type() can be used by applications to
350 check for the existence of a command or to perform additional syntax
351 checking or translation of the command value. For example if the return
352 value is B<SSL_CONF_TYPE_FILE> an application could translate a relative
353 pathname to an absolute pathname.
357 Set supported signature algorithms:
359 SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256");
361 Enable all protocols except SSLv3 and SSLv2:
363 SSL_CONF_cmd(ctx, "Protocol", "ALL,-SSLv3,-SSLv2");
367 SSL_CONF_cmd(ctx, "Protocol", "-ALL,TLSv1.2");
369 Disable TLS session tickets:
371 SSL_CONF_cmd(ctx, "Options", "-SessionTicket");
373 Set supported curves to P-256, P-384:
375 SSL_CONF_cmd(ctx, "Curves", "P-256:P-384");
377 Set automatic support for any elliptic curve for key exchange:
379 SSL_CONF_cmd(ctx, "ECDHParameters", "Automatic");
383 SSL_CONF_cmd() returns 1 if the value of B<cmd> is recognised and B<value> is
384 B<NOT> used and 2 if both B<cmd> and B<value> are used. In other words it
385 returns the number of arguments processed. This is useful when processing
388 A return value of -2 means B<cmd> is not recognised.
390 A return value of -3 means B<cmd> is recognised and the command requires a
391 value but B<value> is NULL.
393 A return code of 0 indicates that both B<cmd> and B<value> are valid but an
394 error occurred attempting to perform the operation: for example due to an
395 error in the syntax of B<value> in this case the error queue may provide
396 additional information.
398 SSL_CONF_finish() returns 1 for success and 0 for failure.
402 L<SSL_CONF_CTX_new(3)|SSL_CONF_CTX_new(3)>,
403 L<SSL_CONF_CTX_set_flags(3)|SSL_CONF_CTX_set_flags(3)>,
404 L<SSL_CONF_CTX_set1_prefix(3)|SSL_CONF_CTX_set1_prefix(3)>,
405 L<SSL_CONF_CTX_set_ssl_ctx(3)|SSL_CONF_CTX_set_ssl_ctx(3)>,
406 L<SSL_CONF_cmd_argv(3)|SSL_CONF_cmd_argv(3)>
410 SSL_CONF_cmd() was first added to OpenSSL 1.0.2