]>
Commit | Line | Data |
---|---|---|
c3ed3b6e DSH |
1 | =pod |
2 | ||
3 | =head1 NAME | |
4 | ||
5 | s_client - SSL/TLS client program | |
6 | ||
7 | =head1 SYNOPSIS | |
8 | ||
9 | B<openssl> B<s_client> | |
169394d4 | 10 | [B<-help>] |
a32fc687 | 11 | [B<-connect host:port>] |
552bf8ec | 12 | [B<-proxy host:port>] |
a22f9c84 E |
13 | [B<-unix path>] |
14 | [B<-4>] | |
15 | [B<-6>] | |
fc1d88f0 | 16 | [B<-servername name>] |
b46c3e9b | 17 | [B<-verify depth>] |
4e6c12f3 | 18 | [B<-verify_return_error>] |
c3ed3b6e | 19 | [B<-cert filename>] |
826a42a0 | 20 | [B<-certform DER|PEM>] |
c3ed3b6e | 21 | [B<-key filename>] |
826a42a0 DSH |
22 | [B<-keyform DER|PEM>] |
23 | [B<-pass arg>] | |
c3ed3b6e DSH |
24 | [B<-CApath directory>] |
25 | [B<-CAfile filename>] | |
40e2d76b MC |
26 | [B<-no-CAfile>] |
27 | [B<-no-CApath>] | |
cddd424a VD |
28 | [B<-dane_tlsa_domain domain>] |
29 | [B<-dane_tlsa_rrdata rrdata>] | |
c4fbed6c | 30 | [B<-dane_ee_no_namechecks>] |
e42d84be HK |
31 | [B<-attime timestamp>] |
32 | [B<-check_ss_sig>] | |
33 | [B<-crl_check>] | |
34 | [B<-crl_check_all>] | |
35 | [B<-explicit_policy>] | |
36 | [B<-extended_crl>] | |
37 | [B<-ignore_critical>] | |
38 | [B<-inhibit_any>] | |
39 | [B<-inhibit_map>] | |
5a1f853b | 40 | [B<-no_check_time>] |
e42d84be HK |
41 | [B<-partial_chain>] |
42 | [B<-policy arg>] | |
43 | [B<-policy_check>] | |
44 | [B<-policy_print>] | |
45 | [B<-purpose purpose>] | |
46 | [B<-suiteB_128>] | |
47 | [B<-suiteB_128_only>] | |
48 | [B<-suiteB_192>] | |
49 | [B<-trusted_first>] | |
fa7b0111 | 50 | [B<-no_alt_chains>] |
e42d84be | 51 | [B<-use_deltas>] |
fbb82a60 | 52 | [B<-auth_level num>] |
e42d84be HK |
53 | [B<-verify_depth num>] |
54 | [B<-verify_email email>] | |
55 | [B<-verify_hostname hostname>] | |
56 | [B<-verify_ip ip>] | |
57 | [B<-verify_name name>] | |
58 | [B<-x509_strict>] | |
c3ed3b6e | 59 | [B<-reconnect>] |
c3ed3b6e DSH |
60 | [B<-showcerts>] |
61 | [B<-debug>] | |
1d8634b1 | 62 | [B<-msg>] |
c3ed3b6e DSH |
63 | [B<-nbio_test>] |
64 | [B<-state>] | |
65 | [B<-nbio>] | |
66 | [B<-crlf>] | |
ce301b6b | 67 | [B<-ign_eof>] |
fc1d88f0 | 68 | [B<-no_ign_eof>] |
c3ed3b6e | 69 | [B<-quiet>] |
c3ed3b6e DSH |
70 | [B<-ssl3>] |
71 | [B<-tls1>] | |
8c73aeb6 VD |
72 | [B<-tls1_1>] |
73 | [B<-tls1_2>] | |
582a17d6 | 74 | [B<-tls1_3>] |
c3ed3b6e DSH |
75 | [B<-no_ssl3>] |
76 | [B<-no_tls1>] | |
fb0e87fb BM |
77 | [B<-no_tls1_1>] |
78 | [B<-no_tls1_2>] | |
582a17d6 | 79 | [B<-no_tls1_3>] |
8c73aeb6 VD |
80 | [B<-dtls>] |
81 | [B<-dtls1>] | |
82 | [B<-dtls1_2>] | |
fb0e87fb | 83 | [B<-fallback_scsv>] |
bc8857bf | 84 | [B<-async>] |
0df80881 MC |
85 | [B<-split_send_frag>] |
86 | [B<-max_pipelines>] | |
87 | [B<-read_buf>] | |
c3ed3b6e | 88 | [B<-bugs>] |
cc5a9ba4 VD |
89 | [B<-comp>] |
90 | [B<-no_comp>] | |
c3ed3b6e | 91 | [B<-cipher cipherlist>] |
fc1d88f0 | 92 | [B<-serverpref>] |
e986704d | 93 | [B<-starttls protocol>] |
b98af49d | 94 | [B<-xmpphost hostname>] |
5270e702 | 95 | [B<-engine id>] |
d24a9c8f DSH |
96 | [B<-tlsextdebug>] |
97 | [B<-no_ticket>] | |
98 | [B<-sess_out filename>] | |
99 | [B<-sess_in filename>] | |
52b621db | 100 | [B<-rand file(s)>] |
9cd50f73 | 101 | [B<-serverinfo types>] |
cba3f1c7 | 102 | [B<-status>] |
776e15f9 | 103 | [B<-alpn protocols>] |
7efd0e77 | 104 | [B<-nextprotoneg protocols>] |
43341433 | 105 | [B<-ct|noct>] |
eb64a6c6 | 106 | [B<-ctlogfile>] |
c3ed3b6e DSH |
107 | |
108 | =head1 DESCRIPTION | |
109 | ||
110 | The B<s_client> command implements a generic SSL/TLS client which connects | |
111 | to a remote host using SSL/TLS. It is a I<very> useful diagnostic tool for | |
112 | SSL servers. | |
113 | ||
114 | =head1 OPTIONS | |
115 | ||
765b4137 DSH |
116 | In addition to the options below the B<s_client> utility also supports the |
117 | common and client only options documented in the | |
6f0ac0e2 | 118 | in the "Supported Command Line Commands" section of the L<SSL_CONF_cmd(3)> |
13cfb043 | 119 | manual page. |
765b4137 | 120 | |
c3ed3b6e DSH |
121 | =over 4 |
122 | ||
169394d4 MR |
123 | =item B<-help> |
124 | ||
125 | Print out a usage message. | |
126 | ||
c3ed3b6e DSH |
127 | =item B<-connect host:port> |
128 | ||
129 | This specifies the host and optional port to connect to. If not specified | |
130 | then an attempt is made to connect to the local host on port 4433. | |
131 | ||
552bf8ec MT |
132 | =item B<-proxy host:port> |
133 | ||
134 | When used with the B<-connect> flag, the program uses the host and port | |
135 | specified with this flag and issues an HTTP CONNECT command to connect | |
136 | to the desired server. | |
137 | ||
a22f9c84 E |
138 | =item B<-unix path> |
139 | ||
140 | Connect over the specified Unix-domain socket. | |
141 | ||
142 | =item B<-4> | |
143 | ||
144 | Use IPv4 only. | |
145 | ||
146 | =item B<-6> | |
147 | ||
148 | Use IPv6 only. | |
149 | ||
fc1d88f0 RS |
150 | =item B<-servername name> |
151 | ||
152 | Set the TLS SNI (Server Name Indication) extension in the ClientHello message. | |
153 | ||
c3ed3b6e DSH |
154 | =item B<-cert certname> |
155 | ||
156 | The certificate to use, if one is requested by the server. The default is | |
157 | not to use a certificate. | |
158 | ||
826a42a0 DSH |
159 | =item B<-certform format> |
160 | ||
161 | The certificate format to use: DER or PEM. PEM is the default. | |
162 | ||
c3ed3b6e DSH |
163 | =item B<-key keyfile> |
164 | ||
165 | The private key to use. If not specified then the certificate file will | |
166 | be used. | |
167 | ||
826a42a0 DSH |
168 | =item B<-keyform format> |
169 | ||
170 | The private format to use: DER or PEM. PEM is the default. | |
171 | ||
172 | =item B<-pass arg> | |
173 | ||
174 | the private key password source. For more information about the format of B<arg> | |
9b86974e | 175 | see the B<PASS PHRASE ARGUMENTS> section in L<openssl(1)>. |
826a42a0 | 176 | |
c3ed3b6e DSH |
177 | =item B<-verify depth> |
178 | ||
179 | The verify depth to use. This specifies the maximum length of the | |
180 | server certificate chain and turns on server certificate verification. | |
181 | Currently the verify operation continues after errors so all the problems | |
182 | with a certificate chain can be seen. As a side effect the connection | |
183 | will never fail due to a server certificate verify failure. | |
184 | ||
4e6c12f3 DSH |
185 | =item B<-verify_return_error> |
186 | ||
187 | Return verification errors instead of continuing. This will typically | |
188 | abort the handshake with a fatal error. | |
189 | ||
c3ed3b6e DSH |
190 | =item B<-CApath directory> |
191 | ||
192 | The directory to use for server certificate verification. This directory | |
193 | must be in "hash format", see B<verify> for more information. These are | |
194 | also used when building the client certificate chain. | |
195 | ||
196 | =item B<-CAfile file> | |
197 | ||
198 | A file containing trusted certificates to use during server authentication | |
199 | and to use when attempting to build the client certificate chain. | |
200 | ||
40e2d76b MC |
201 | =item B<-no-CAfile> |
202 | ||
203 | Do not load the trusted CA certificates from the default file location | |
204 | ||
205 | =item B<-no-CApath> | |
206 | ||
207 | Do not load the trusted CA certificates from the default directory location | |
208 | ||
cddd424a VD |
209 | =item B<-dane_tlsa_domain domain> |
210 | ||
211 | Enable RFC6698/RFC7671 DANE TLSA authentication and specify the | |
212 | TLSA base domain which becomes the default SNI hint and the primary | |
213 | reference identifier for hostname checks. This must be used in | |
214 | combination with at least one instance of the B<-dane_tlsa_rrdata> | |
215 | option below. | |
216 | ||
217 | When DANE authentication succeeds, the diagnostic output will include | |
218 | the lowest (closest to 0) depth at which a TLSA record authenticated | |
219 | a chain certificate. When that TLSA record is a "2 1 0" trust | |
220 | anchor public key that signed (rather than matched) the top-most | |
221 | certificate of the chain, the result is reported as "TA public key | |
222 | verified". Otherwise, either the TLSA record "matched TA certificate" | |
223 | at a positive depth or else "matched EE certificate" at depth 0. | |
224 | ||
225 | =item B<-dane_tlsa_rrdata rrdata> | |
226 | ||
227 | Use one or more times to specify the RRDATA fields of the DANE TLSA | |
228 | RRset associated with the target service. The B<rrdata> value is | |
229 | specied in "presentation form", that is four whitespace separated | |
230 | fields that specify the usage, selector, matching type and associated | |
231 | data, with the last of these encoded in hexadecimal. Optional | |
232 | whitespace is ignored in the associated data field. For example: | |
233 | ||
c0a445a9 VD |
234 | $ openssl s_client -brief -starttls smtp \ |
235 | -connect smtp.example.com:25 \ | |
cddd424a VD |
236 | -dane_tlsa_domain smtp.example.com \ |
237 | -dane_tlsa_rrdata "2 1 1 | |
238 | B111DD8A1C2091A89BD4FD60C57F0716CCE50FEEFF8137CDBEE0326E 02CF362B" \ | |
239 | -dane_tlsa_rrdata "2 1 1 | |
240 | 60B87575447DCBA2A36B7D11AC09FB24A9DB406FEE12D2CC90180517 616E8A18" | |
cddd424a | 241 | ... |
c0a445a9 | 242 | Verification: OK |
cddd424a | 243 | Verified peername: smtp.example.com |
c0a445a9 | 244 | DANE TLSA 2 1 1 ...ee12d2cc90180517616e8a18 matched TA certificate at depth 1 |
cddd424a VD |
245 | ... |
246 | ||
c4fbed6c VD |
247 | =item B<-dane_ee_no_namechecks> |
248 | ||
249 | This disables server name checks when authenticating via DANE-EE(3) TLSA | |
250 | records. | |
251 | For some applications, primarily web browsers, it is not safe to disable name | |
252 | checks due to "unknown key share" attacks, in which a malicious server can | |
253 | convince a client that a connection to a victim server is instead a secure | |
254 | connection to the malicious server. | |
255 | The malicious server may then be able to violate cross-origin scripting | |
256 | restrictions. | |
257 | Thus, despite the text of RFC7671, name checks are by default enabled for | |
258 | DANE-EE(3) TLSA records, and can be disabled in applications where it is safe | |
259 | to do so. | |
260 | In particular, SMTP and XMPP clients should set this option as SRV and MX | |
261 | records already make it possible for a remote domain to redirect client | |
262 | connections to any server of its choice, and in any case SMTP and XMPP clients | |
263 | do not execute scripts downloaded from remote servers. | |
264 | ||
e42d84be | 265 | =item B<-attime>, B<-check_ss_sig>, B<-crl_check>, B<-crl_check_all>, |
d33def66 | 266 | B<-explicit_policy>, B<-extended_crl>, B<-ignore_critical>, B<-inhibit_any>, |
5a1f853b | 267 | B<-inhibit_map>, B<-no_alt_chains>, B<-no_check_time>, B<-partial_chain>, B<-policy>, |
e42d84be | 268 | B<-policy_check>, B<-policy_print>, B<-purpose>, B<-suiteB_128>, |
d33def66 | 269 | B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>, B<-use_deltas>, |
fbb82a60 VD |
270 | B<-auth_level>, B<-verify_depth>, B<-verify_email>, B<-verify_hostname>, |
271 | B<-verify_ip>, B<-verify_name>, B<-x509_strict> | |
e5fa864f | 272 | |
fa7b0111 | 273 | Set various certificate chain validation options. See the |
9b86974e | 274 | L<verify(1)> manual page for details. |
e5fa864f | 275 | |
c3ed3b6e DSH |
276 | =item B<-reconnect> |
277 | ||
278 | reconnects to the same server 5 times using the same session ID, this can | |
279 | be used as a test that session caching is working. | |
280 | ||
c3ed3b6e DSH |
281 | =item B<-showcerts> |
282 | ||
283 | display the whole server certificate chain: normally only the server | |
284 | certificate itself is displayed. | |
285 | ||
286 | =item B<-prexit> | |
287 | ||
288 | print session information when the program exits. This will always attempt | |
289 | to print out information even if the connection fails. Normally information | |
290 | will only be printed out once if the connection succeeds. This option is useful | |
291 | because the cipher in use may be renegotiated or the connection may fail | |
292 | because a client certificate is required or is requested only after an | |
293 | attempt is made to access a certain URL. Note: the output produced by this | |
294 | option is not always accurate because a connection might never have been | |
295 | established. | |
296 | ||
297 | =item B<-state> | |
298 | ||
299 | prints out the SSL session states. | |
300 | ||
301 | =item B<-debug> | |
302 | ||
303 | print extensive debugging information including a hex dump of all traffic. | |
304 | ||
1d8634b1 BM |
305 | =item B<-msg> |
306 | ||
307 | show all protocol messages with hex dump. | |
308 | ||
8dbeb110 DSH |
309 | =item B<-trace> |
310 | ||
311 | show verbose trace output of protocol messages. OpenSSL needs to be compiled | |
312 | with B<enable-ssl-trace> for this option to work. | |
313 | ||
314 | =item B<-msgfile> | |
315 | ||
316 | file to send output of B<-msg> or B<-trace> to, default standard output. | |
317 | ||
c3ed3b6e DSH |
318 | =item B<-nbio_test> |
319 | ||
657e60fa | 320 | tests non-blocking I/O |
c3ed3b6e DSH |
321 | |
322 | =item B<-nbio> | |
323 | ||
657e60fa | 324 | turns on non-blocking I/O |
c3ed3b6e DSH |
325 | |
326 | =item B<-crlf> | |
327 | ||
328 | this option translated a line feed from the terminal into CR+LF as required | |
329 | by some servers. | |
330 | ||
ce301b6b RL |
331 | =item B<-ign_eof> |
332 | ||
333 | inhibit shutting down the connection when end of file is reached in the | |
334 | input. | |
335 | ||
c3ed3b6e DSH |
336 | =item B<-quiet> |
337 | ||
3b80e3aa | 338 | inhibit printing of session and certificate information. This implicitly |
ce301b6b | 339 | turns on B<-ign_eof> as well. |
c3ed3b6e | 340 | |
fc1d88f0 RS |
341 | =item B<-no_ign_eof> |
342 | ||
343 | shut down the connection when end of file is reached in the input. | |
344 | Can be used to override the implicit B<-ign_eof> after B<-quiet>. | |
345 | ||
ddac1974 NL |
346 | =item B<-psk_identity identity> |
347 | ||
348 | Use the PSK identity B<identity> when using a PSK cipher suite. | |
349 | ||
350 | =item B<-psk key> | |
351 | ||
352 | Use the PSK key B<key> when using a PSK cipher suite. The key is | |
353 | given as a hexadecimal number without leading 0x, for example -psk | |
354 | 1a2b3c4d. | |
355 | ||
582a17d6 | 356 | =item B<-ssl3>, B<-tls1>, B<-tls1_1>, B<-tls1_2>, B<-tls1_3>, B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>, B<-no_tls1_3> |
c3ed3b6e | 357 | |
8c73aeb6 VD |
358 | These options require or disable the use of the specified SSL or TLS protocols. |
359 | By default B<s_client> will negotiate the highest mutually supported protocol | |
360 | version. | |
361 | When a specific TLS version is required, only that version will be offered to | |
362 | and accepted from the server. | |
c3ed3b6e | 363 | |
8c73aeb6 VD |
364 | =item B<-dtls>, B<-dtls1>, B<-dtls1_2> |
365 | ||
366 | These options make B<s_client> use DTLS protocols instead of TLS. | |
60250017 | 367 | With B<-dtls>, B<s_client> will negotiate any supported DTLS protocol version, |
8c73aeb6 VD |
368 | whilst B<-dtls1> and B<-dtls1_2> will only support DTLS1.0 and DTLS1.2 |
369 | respectively. | |
fb0e87fb BM |
370 | |
371 | =item B<-fallback_scsv> | |
372 | ||
373 | Send TLS_FALLBACK_SCSV in the ClientHello. | |
c3ed3b6e | 374 | |
bc8857bf MC |
375 | =item B<-async> |
376 | ||
377 | switch on asynchronous mode. Cryptographic operations will be performed | |
378 | asynchronously. This will only have an effect if an asynchronous capable engine | |
379 | is also used via the B<-engine> option. For test purposes the dummy async engine | |
380 | (dasync) can be used (if available). | |
381 | ||
0df80881 MC |
382 | =item B<-split_send_frag int> |
383 | ||
384 | The size used to split data for encrypt pipelines. If more data is written in | |
385 | one go than this value then it will be split into multiple pipelines, up to the | |
386 | maximum number of pipelines defined by max_pipelines. This only has an effect if | |
387 | a suitable ciphersuite has been negotiated, an engine that supports pipelining | |
388 | has been loaded, and max_pipelines is greater than 1. See | |
389 | L<SSL_CTX_set_split_send_fragment(3)> for further information. | |
390 | ||
391 | =item B<-max_pipelines int> | |
392 | ||
393 | The maximum number of encrypt/decrypt pipelines to be used. This will only have | |
394 | an effect if an engine has been loaded that supports pipelining (e.g. the dasync | |
0ad69cd6 | 395 | engine) and a suitable ciphersuite has been negotiated. The default value is 1. |
0df80881 MC |
396 | See L<SSL_CTX_set_max_pipelines(3)> for further information. |
397 | ||
398 | =item B<-read_buf int> | |
399 | ||
400 | The default read buffer size to be used for connections. This will only have an | |
401 | effect if the buffer size is larger than the size that would otherwise be used | |
402 | and pipelining is in use (see L<SSL_CTX_set_default_read_buffer_len(3)> for | |
403 | further information). | |
404 | ||
c3ed3b6e DSH |
405 | =item B<-bugs> |
406 | ||
407 | there are several known bug in SSL and TLS implementations. Adding this | |
408 | option enables various workarounds. | |
409 | ||
cc5a9ba4 VD |
410 | =item B<-comp> |
411 | ||
412 | Enables support for SSL/TLS compression. | |
413 | This option was introduced in OpenSSL 1.1.0. | |
414 | TLS compression is not recommended and is off by default as of | |
415 | OpenSSL 1.1.0. | |
416 | ||
417 | =item B<-no_comp> | |
418 | ||
419 | Disables support for SSL/TLS compression. | |
420 | TLS compression is not recommended and is off by default as of | |
421 | OpenSSL 1.1.0. | |
422 | ||
765b4137 DSH |
423 | =item B<-brief> |
424 | ||
425 | only provide a brief summary of connection parameters instead of the | |
426 | normal verbose output. | |
427 | ||
c3ed3b6e DSH |
428 | =item B<-cipher cipherlist> |
429 | ||
fabce041 DSH |
430 | this allows the cipher list sent by the client to be modified. Although |
431 | the server determines which cipher suite is used it should take the first | |
432 | supported cipher in the list sent by the client. See the B<ciphers> | |
433 | command for more information. | |
c3ed3b6e | 434 | |
e986704d RL |
435 | =item B<-starttls protocol> |
436 | ||
437 | send the protocol-specific message(s) to switch to TLS for communication. | |
438 | B<protocol> is a keyword for the intended protocol. Currently, the only | |
cfb4f1ef | 439 | supported keywords are "smtp", "pop3", "imap", "ftp", "xmpp", "xmpp-server", |
8f85aa6b | 440 | "irc", "postgres", "lmtp" and "nntp". |
e986704d | 441 | |
b98af49d CALP |
442 | =item B<-xmpphost hostname> |
443 | ||
898ea7b8 KE |
444 | This option, when used with "-starttls xmpp" or "-starttls xmpp-server", |
445 | specifies the host for the "to" attribute of the stream element. | |
b98af49d CALP |
446 | If this option is not specified, then the host specified with "-connect" |
447 | will be used. | |
448 | ||
d24a9c8f DSH |
449 | =item B<-tlsextdebug> |
450 | ||
451 | print out a hex dump of any TLS extensions received from the server. | |
452 | ||
453 | =item B<-no_ticket> | |
454 | ||
1bc74519 | 455 | disable RFC4507bis session ticket support. |
d24a9c8f DSH |
456 | |
457 | =item B<-sess_out filename> | |
458 | ||
459 | output SSL session to B<filename> | |
460 | ||
461 | =item B<-sess_in sess.pem> | |
462 | ||
463 | load SSL session from B<filename>. The client will attempt to resume a | |
464 | connection from this session. | |
465 | ||
5270e702 RL |
466 | =item B<-engine id> |
467 | ||
e5fa864f | 468 | specifying an engine (by its unique B<id> string) will cause B<s_client> |
5270e702 RL |
469 | to attempt to obtain a functional reference to the specified engine, |
470 | thus initialising it if needed. The engine will then be set as the default | |
471 | for all available algorithms. | |
472 | ||
52b621db LJ |
473 | =item B<-rand file(s)> |
474 | ||
475 | a file or files containing random data used to seed the random number | |
9b86974e | 476 | generator, or an EGD socket (see L<RAND_egd(3)>). |
35ed393e | 477 | Multiple files can be specified separated by an OS-dependent character. |
52b621db LJ |
478 | The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for |
479 | all others. | |
480 | ||
9cd50f73 T |
481 | =item B<-serverinfo types> |
482 | ||
1bc74519 | 483 | a list of comma-separated TLS Extension Types (numbers between 0 and |
9cd50f73 T |
484 | 65535). Each type will be sent as an empty ClientHello TLS Extension. |
485 | The server's response (if any) will be encoded and displayed as a PEM | |
486 | file. | |
487 | ||
cba3f1c7 DSH |
488 | =item B<-status> |
489 | ||
490 | sends a certificate status request to the server (OCSP stapling). The server | |
491 | response (if any) is printed out. | |
492 | ||
776e15f9 | 493 | =item B<-alpn protocols>, B<-nextprotoneg protocols> |
7efd0e77 | 494 | |
776e15f9 RS |
495 | these flags enable the |
496 | Enable the Application-Layer Protocol Negotiation or Next Protocol | |
497 | Negotiation extension, respectively. ALPN is the IETF standard and | |
498 | replaces NPN. | |
499 | The B<protocols> list is a | |
7efd0e77 HK |
500 | comma-separated protocol names that the client should advertise |
501 | support for. The list should contain most wanted protocols first. | |
502 | Protocol names are printable ASCII strings, for example "http/1.1" or | |
503 | "spdy/3". | |
504 | Empty list of protocols is treated specially and will cause the client to | |
505 | advertise support for the TLS extension but disconnect just after | |
4c583c36 | 506 | receiving ServerHello with a list of server supported protocols. |
7efd0e77 | 507 | |
43341433 | 508 | =item B<-ct|noct> |
eb64a6c6 | 509 | |
43341433 VD |
510 | Use one of these two options to control whether Certificate Transparency (CT) |
511 | is enabled (B<-ct>) or disabled (B<-noct>). | |
512 | If CT is enabled, signed certificate timestamps (SCTs) will be requested from | |
513 | the server and reported at handshake completion. | |
eb64a6c6 RP |
514 | |
515 | Enabling CT also enables OCSP stapling, as this is one possible delivery method | |
516 | for SCTs. | |
517 | ||
518 | =item B<-ctlogfile> | |
519 | ||
520 | A file containing a list of known Certificate Transparency logs. See | |
521 | L<SSL_CTX_set_ctlog_list_file(3)> for the expected file format. | |
522 | ||
4bf73e9f PW |
523 | =item B<-keylogfile path> |
524 | ||
525 | Appends TLS secrets to the specified keylog file such that external programs | |
526 | (like Wireshark) can decrypt TLS connections. | |
527 | ||
efeca6aa UM |
528 | =back |
529 | ||
c3ed3b6e DSH |
530 | =head1 CONNECTED COMMANDS |
531 | ||
532 | If a connection is established with an SSL server then any data received | |
533 | from the server is displayed and any key presses will be sent to the | |
ce301b6b | 534 | server. When used interactively (which means neither B<-quiet> nor B<-ign_eof> |
3b80e3aa | 535 | have been given), the session will be renegotiated if the line begins with an |
ce301b6b RL |
536 | B<R>, and if the line begins with a B<Q> or if end of file is reached, the |
537 | connection will be closed down. | |
c3ed3b6e DSH |
538 | |
539 | =head1 NOTES | |
540 | ||
541 | B<s_client> can be used to debug SSL servers. To connect to an SSL HTTP | |
542 | server the command: | |
543 | ||
544 | openssl s_client -connect servername:443 | |
545 | ||
546 | would typically be used (https uses port 443). If the connection succeeds | |
547 | then an HTTP command can be given such as "GET /" to retrieve a web page. | |
548 | ||
549 | If the handshake fails then there are several possible causes, if it is | |
45f55f6a KR |
550 | nothing obvious like no client certificate then the B<-bugs>, |
551 | B<-ssl3>, B<-tls1>, B<-no_ssl3>, B<-no_tls1> options can be tried | |
c3ed3b6e DSH |
552 | in case it is a buggy server. In particular you should play with these |
553 | options B<before> submitting a bug report to an OpenSSL mailing list. | |
554 | ||
555 | A frequent problem when attempting to get client certificates working | |
556 | is that a web client complains it has no certificates or gives an empty | |
557 | list to choose from. This is normally because the server is not sending | |
558 | the clients certificate authority in its "acceptable CA list" when it | |
559 | requests a certificate. By using B<s_client> the CA list can be viewed | |
560 | and checked. However some servers only request client authentication | |
561 | after a specific URL is requested. To obtain the list in this case it | |
a32fc687 | 562 | is necessary to use the B<-prexit> option and send an HTTP request |
c3ed3b6e DSH |
563 | for an appropriate page. |
564 | ||
565 | If a certificate is specified on the command line using the B<-cert> | |
566 | option it will not be used unless the server specifically requests | |
567 | a client certificate. Therefor merely including a client certificate | |
568 | on the command line is no guarantee that the certificate works. | |
569 | ||
570 | If there are problems verifying a server certificate then the | |
571 | B<-showcerts> option can be used to show the whole chain. | |
572 | ||
4e6c12f3 DSH |
573 | The B<s_client> utility is a test tool and is designed to continue the |
574 | handshake after any certificate verification errors. As a result it will | |
575 | accept any certificate chain (trusted or not) sent by the peer. None test | |
576 | applications should B<not> do this as it makes them vulnerable to a MITM | |
577 | attack. This behaviour can be changed by with the B<-verify_return_error> | |
578 | option: any verify errors are then returned aborting the handshake. | |
579 | ||
c3ed3b6e DSH |
580 | =head1 BUGS |
581 | ||
8c73aeb6 VD |
582 | Because this program has a lot of options and also because some of the |
583 | techniques used are rather old, the C source of B<s_client> is rather hard to | |
584 | read and not a model of how things should be done. | |
585 | A typical SSL client program would be much simpler. | |
c3ed3b6e | 586 | |
c3ed3b6e DSH |
587 | The B<-prexit> option is a bit of a hack. We should really report |
588 | information whenever a session is renegotiated. | |
589 | ||
590 | =head1 SEE ALSO | |
591 | ||
6f0ac0e2 | 592 | L<SSL_CONF_cmd(3)>, |
9b86974e | 593 | L<sess_id(1)>, L<s_server(1)>, L<ciphers(1)> |
c3ed3b6e | 594 | |
fa7b0111 MC |
595 | =head1 HISTORY |
596 | ||
597 | The -no_alt_chains options was first added to OpenSSL 1.1.0. | |
598 | ||
e2f92610 RS |
599 | =head1 COPYRIGHT |
600 | ||
601 | Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved. | |
602 | ||
603 | Licensed under the OpenSSL license (the "License"). You may not use | |
604 | this file except in compliance with the License. You can obtain a copy | |
605 | in the file LICENSE in the source distribution or at | |
606 | L<https://www.openssl.org/source/license.html>. | |
607 | ||
608 | =cut |