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