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1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
5 | SSL_CONF_cmd - send configuration command | |
6 | ||
7 | =head1 SYNOPSIS | |
8 | ||
9 | #include <openssl/ssl.h> | |
10 | ||
11 | int SSL_CONF_cmd(SSL_CONF_CTX *cctx, const char *cmd, const char *value); | |
12 | ||
13 | =head1 DESCRIPTION | |
14 | ||
15 | The function SSL_CONF_cmd() performs configuration operation B<cmd> with | |
16 | optional parameter B<value> on B<ctx>. Its purpose is to simplify application | |
17 | configuration of B<SSL_CTX> or B<SSL> structures by providing a common | |
18 | framework for configuration files or command line options. | |
19 | ||
20 | =head1 SUPPORTED CONFIGURATION FILE COMMANDS | |
21 | ||
22 | Currently supported B<cmd> names for configuration files (i.e. when the | |
23 | flag B<SSL_CONF_FLAG_FILE> is set) are listed below. All configuration file | |
24 | B<cmd> names and are case insensitive so B<signaturealgorithms> is recognised | |
25 | as well as B<SignatureAlgorithms>. Unless otherwise states the B<value> names | |
26 | are also case insensitive. | |
27 | ||
28 | Note: the command prefix (if set) alters the recognised B<cmd> values. | |
29 | ||
30 | =over 4 | |
31 | ||
32 | =item B<CipherSuite> | |
33 | ||
34 | Sets the cipher suite list to B<value>. Note: syntax checking of B<value> is | |
35 | currently not performed unless a B<SSL> or B<SSL_CTX> structure is | |
36 | associated with B<cctx>. | |
37 | ||
38 | =item B<SignatureAlgorithms> | |
39 | ||
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. | |
43 | ||
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. | |
49 | ||
50 | If this option is not set then all signature algorithms supported by the | |
51 | OpenSSL library are permissible. | |
52 | ||
53 | =item B<ClientSignatureAlgorithms> | |
54 | ||
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 use for the client certificate. | |
59 | ||
60 | The syntax of B<value> is identical to B<SignatureAlgorithms>. If not set then | |
61 | the value set for B<SignatureAlgorithms> will be used instead. | |
62 | ||
63 | =item B<Curves> | |
64 | ||
65 | This sets the supported elliptic curves. For servers the curves are | |
66 | sent using the supported curves extension to TLS. For clients the it is used | |
67 | to determine which curve to use. This affects curves used for both signatures | |
68 | and key exchange. | |
69 | ||
70 | The B<value> argument is a colon separated list of curves. The curve can be | |
71 | either the B<NIST> name (e.g. B<P-256>) or an OpenSSL OID name (e.g | |
72 | B<prime256v1>). Curve names are case sensitive. | |
73 | ||
74 | =item B<ECDHParameters> | |
75 | ||
76 | This sets the temporary curve used for ephemeral ECDH modes. | |
77 | ||
78 | The B<value> argument is a curve name or the special value B<Automatic> which | |
79 | automatically picks an appropriate curve based on client and server | |
80 | preferences. The curve can be either the B<NIST> name (e.g. B<P-256>) or an | |
81 | OpenSSL OID name (e.g B<prime256v1>). Curve names are case sensitive. | |
82 | ||
83 | =item B<Protocol> | |
84 | ||
85 | The supported versions of the SSL or TLS protocol. | |
86 | ||
87 | The B<value> argument is a comma separated list of supported protocols to | |
88 | enable or disable. If an protocol is preceded by B<-> that version is disabled. | |
89 | All versions are enabled by default, though applications may choose to | |
90 | explicitly disable some version. Currently supported protocol | |
91 | values are B<SSLv2>, B<SSLv3>, B<TLSv1>, B<TLSv1.1> and B<TLSv1.2>. The | |
92 | special value B<ALL> refers to all supported versions. | |
93 | ||
94 | =item B<Options> | |
95 | ||
96 | The B<value> argument is a comma separated list of various flags to set. | |
97 | If a flag string is preceded B<-> it is disabled. See the | |
98 | B<SSL_CTX_set_options> function for more details of individual options. | |
99 | ||
100 | Each option is listed below. Where an operation is enabled by default | |
101 | the B<-flag> syntax is needed to disable it. | |
102 | ||
103 | B<SessionTicket>: session ticket support, enabled by default. Inverse of | |
104 | B<SSL_OP_NO_TICKET>: that is B<-SessionTicket> is the same as setting | |
105 | B<SSL_OP_NO_TICKET>. | |
106 | ||
107 | B<Compression>: SSL/TLS compression support, enabled by default. Inverse | |
108 | of B<SSL_OP_NO_COMPRESSION>. | |
109 | ||
110 | B<EmptyFragments>: use empty fragments as a countermeasure against a | |
111 | SSL 3.0/TLS 1.0 protocol vulnerability affecting CBC ciphers. It | |
112 | is set by default. Inverse of B<SSL_OP_DONT_INSERT_EMPTY_FRAGMENTS>. | |
113 | ||
114 | B<Bugs> enable various bug workarounds. Same as B<SSL_OP_ALL>. | |
115 | ||
116 | B<DHSingle> enable single use DH keys, set by default. Inverse of | |
117 | B<SSL_OP_DH_SINGLE>. Only used by servers. | |
118 | ||
119 | B<ECDHSingle> enable single use ECDH keys, set by default. Inverse of | |
120 | B<SSL_OP_ECDH_SINGLE>. Only used by servers. | |
121 | ||
122 | B<ServerPreference> use server and not client preference order when | |
123 | determining which cipher suite, signature algorithm or elliptic curve | |
124 | to use for an incoming connection. Equivalent to | |
125 | B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers. | |
126 | ||
127 | B<UnsafeLegacyRenegotiation> permits the use of unsafe legacy renegotiation. | |
128 | Equivalent to B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>. | |
129 | ||
130 | B<UnsafeLegacyServerConnect> permits the use of unsafe legacy renegotiation | |
131 | for OpenSSL clients only. Equivalent to B<SSL_OP_LEGACY_SERVER_CONNECT>. | |
132 | Set by default. | |
133 | ||
134 | =back | |
135 | ||
136 | =head1 SUPPORTED COMMAND LINE COMMANDS | |
137 | ||
138 | Currently supported B<cmd> names for command lines (i.e. when the | |
139 | flag B<SSL_CONF_CMDLINE> is set) are listed below. Note: all B<cmd> names | |
140 | and are case sensitive. Unless otherwise stated the B<value> parameter is | |
141 | noh used. The default prefix for command line commands is B<-> and that is | |
142 | reflected below. | |
143 | ||
144 | =over 4 | |
145 | ||
146 | =item B<-sigalgs> | |
147 | ||
148 | Sets the supported signature algorithms to B<value>. Equivalent to the | |
149 | B<SignatureAlgorithms> file command. | |
150 | ||
151 | =item B<-client_sigalgs> | |
152 | ||
153 | Sets the supported client signature algorithms to B<value>. Equivalent to the | |
154 | B<ClientSignatureAlgorithms> file command. | |
155 | ||
156 | =item B<-curves> | |
157 | ||
158 | Sets supported elliptic curves to B<value>. Equivalent to B<Curves> file | |
159 | command. | |
160 | ||
161 | =item B<-named_curve> | |
162 | ||
163 | Sets supported ECDH parameters to B<value>. For automatic curve selection | |
164 | B<value> should be set to B<auto>, otherwise the command is identical to | |
165 | the B<ECDHParameters> file command. | |
166 | ||
167 | =item B<-cipher> | |
168 | ||
169 | Sets the cipher suite list to B<value>. Note: syntax checking of B<value> is | |
170 | currently not performed unless a B<SSL> or B<SSL_CTX> structure is | |
171 | associated with B<cctx>. | |
172 | ||
173 | =item B<-no_ssl2>, B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2> | |
174 | ||
175 | Disables protocol support for SSLv2, SSLv3, TLS 1.0, TLS 1.1 or TLS 1.2 | |
176 | by setting the corresponding options B<SSL_OP_NO_SSL2>, B<SSL_OP_NO_SSL3>, | |
177 | B<SSL_OP_NO_TLS1> B<SSL_OP_NO_TLS1_1> and B<SSL_OP_NO_TLS1_2> respectively. | |
178 | ||
179 | =item B<-bugs> | |
180 | ||
181 | Various bug workarounds are set, same as setting B<SSL_OP_ALL>. | |
182 | ||
183 | =item B<-no_comp> | |
184 | ||
185 | Disables support for SSL/TLS compression, same as setting B<SSL_OP_NO_COMPRESS>. | |
186 | ||
187 | =item B<-no_ticket> | |
188 | ||
189 | Disables support for session tickets, same as setting B<SSL_OP_NO_TICKET>. | |
190 | ||
191 | =item B<-serverpref> | |
192 | ||
193 | Use server and not client preference order when determining which cipher suite, | |
194 | signature algorithm or elliptic curve to use for an incoming connection. | |
195 | Equivalent to B<SSL_OP_CIPHER_SERVER_PREFERENCE>. Only used by servers. | |
196 | ||
197 | =item B<-legacyrenegotiation> | |
198 | ||
199 | permits the use of unsafe legacy renegotiation. Equivalent to setting | |
200 | B<SSL_OP_ALLOW_UNSAFE_LEGACY_RENEGOTIATION>. | |
201 | ||
202 | =item B<-legacy_server_connect>, B<-no_legacy_server_connect> | |
203 | ||
204 | permits or prohibits the use of unsafe legacy renegotiation for OpenSSL | |
205 | clients only. Equivalent to setting or clearing B<SSL_OP_LEGACY_SERVER_CONNECT>. | |
206 | Set by default. | |
207 | ||
208 | =item B<-strict> | |
209 | ||
210 | enables strict mode protocol handling. Equivalent to setting | |
211 | B<SSL_CERT_FLAG_TLS_STRICT>. | |
212 | ||
213 | =item B<-debug_broken_protocol> | |
214 | ||
215 | disables various checks and permits several kinds of broken protocol behaviour | |
216 | for testing purposes: it should B<NEVER> be used in anything other than a test | |
217 | environment. Only supported if OpenSSL is configured with | |
218 | B<-DOPENSSL_SSL_DEBUG_BROKEN_PROTOCOL>. | |
219 | ||
220 | =back | |
221 | ||
222 | =head1 NOTES | |
223 | ||
224 | The order of operations is significant. This can be used to set either defaults | |
225 | or values which cannot be overridden. For example if an application calls: | |
226 | ||
227 | SSL_CONF_cmd(ctx, "Protocol", "-SSLv2"); | |
228 | SSL_CONF_cmd(ctx, userparam, uservalue); | |
229 | ||
230 | it will disable SSLv2 support by default but the user can override it. If | |
231 | however the call sequence is: | |
232 | ||
233 | SSL_CONF_cmd(ctx, userparam, uservalue); | |
234 | SSL_CONF_cmd(ctx, "Protocol", "-SSLv2"); | |
235 | ||
236 | SSLv2 is B<always> disabled and attempt to override this by the user are | |
237 | ignored. | |
238 | ||
239 | By checking the return code of SSL_CTX_cmd() it is possible to query if a | |
240 | given B<cmd> is recognised, this is useful is SSL_CTX_cmd() values are | |
241 | mixed with additional application specific operations. | |
242 | ||
243 | For example an application might call SSL_CTX_cmd() and if it returns | |
244 | -2 (unrecognised command) continue with processing of application specific | |
245 | commands. | |
246 | ||
247 | Applications can also use SSL_CTX_cmd() to process command lines though the | |
248 | utility function SSL_CTX_cmd_argv() is normally used instead. One way | |
249 | to do this is to check for an initial prefix ("-", "--" or "--ssl-" for example) | |
250 | on a command argument and pass the rest to B<cmd>. The following argument | |
251 | is passed to B<value> (which may be NULL). | |
252 | ||
253 | In this case if the return value is positive then it is used to skip that | |
254 | number of arguments as they have been processed by SSL_CTX_cmd(). If -2 is | |
255 | returned then B<cmd> is not recognised and application specific arguments | |
256 | can be checked instead. If -3 is returned a required argument is missing | |
257 | and an error is indicated. If 0 is returned some other error occurred and | |
258 | this can be reported back to the user. | |
259 | ||
260 | =head1 EXAMPLES | |
261 | ||
262 | Set supported signature algorithms: | |
263 | ||
264 | SSL_CONF_cmd(ctx, "SignatureAlgorithms", "ECDSA+SHA256:RSA+SHA256:DSA+SHA256"); | |
265 | ||
266 | Enable all protocols except SSLv3 and SSLv2: | |
267 | ||
268 | SSL_CONF_cmd(ctx, "Protocol", "ALL,-SSLv3,-SSLv2"); | |
269 | ||
270 | Only enable TLSv1.2: | |
271 | ||
272 | SSL_CONF_cmd(ctx, "Protocol", "-ALL,TLSv1.2"); | |
273 | ||
274 | Disable TLS session tickets: | |
275 | ||
276 | SSL_CONF_cmd(ctx, "Options", "-SessionTicket"); | |
277 | ||
278 | Set supported curves to P-256, P-384: | |
279 | ||
280 | SSL_CONF_cmd(ctx, "Curves", "P-256:P-384"); | |
281 | ||
282 | Set automatic support for any elliptic curve for key exchange: | |
283 | ||
284 | SSL_CONF_cmd(ctx, "ECDHParameters", "Automatic"); | |
285 | ||
286 | =head1 RETURN VALUES | |
287 | ||
288 | SSL_CONF_cmd() return 1 if the value of B<cmd> is recognised and B<value> is | |
289 | B<NOT> used and 2 if both B<cmd> and B<value> are used. In other words it | |
290 | returns the number of arguments processed. This is useful when processing | |
291 | command lines. | |
292 | ||
293 | A return value of -2 means B<cmd> is not recognised. | |
294 | ||
295 | A return value of -3 means B<cmd> is recognised and the command requires a | |
296 | value but B<value> is NULL. | |
297 | ||
298 | A return code of 0 indicates that both B<cmd> and B<value> are valid but an | |
299 | error occurred attempting to perform the operation: for example due to an | |
300 | error in the syntax of B<value> in this case the error queue may provide | |
301 | additional information. | |
302 | ||
303 | =head1 SEE ALSO | |
304 | ||
305 | L<SSL_CONF_CTX_new(3)|SSL_CONF_CTX_new(3)>, | |
306 | L<SSL_CONF_CTX_set_flags(3)|SSL_CONF_CTX_set_flags(3)>, | |
307 | L<SSL_CONF_CTX_set1_prefix(3)|SSL_CONF_CTX_set1_prefix(3)>, | |
308 | L<SSL_CONF_CTX_set_ssl_ctx(3)|SSL_CONF_CTX_set_ssl_ctx(3)>, | |
309 | L<SSL_CONF_cmd_argv(3)|SSL_CONF_cmd_argv(3)> | |
310 | ||
311 | =head1 HISTORY | |
312 | ||
313 | SSL_CONF_cmd() was first added to OpenSSL 1.1.0 | |
314 | ||
315 | =cut |