1OPENSSL-S_CLIENT(1ossl) OpenSSL OPENSSL-S_CLIENT(1ossl)
2
6 openssl-s_client - SSL/TLS client program
7
9 openssl s_client [-help] [-ssl_config section] [-connect host:port]
10 [-host hostname] [-port port] [-bind host:port] [-proxy host:port]
11 [-proxy_user userid] [-proxy_pass arg] [-unix path] [-4] [-6]
12 [-servername name] [-noservername] [-verify depth]
13 [-verify_return_error] [-verify_quiet] [-verifyCAfile filename]
14 [-verifyCApath dir] [-verifyCAstore uri] [-cert filename] [-certform
15 DER|PEM|P12] [-cert_chain filename] [-build_chain] [-CRL filename]
16 [-CRLform DER|PEM] [-crl_download] [-key filename|uri] [-keyform
17 DER|PEM|P12|ENGINE] [-pass arg] [-chainCAfile filename] [-chainCApath
18 directory] [-chainCAstore uri] [-requestCAfile filename]
19 [-dane_tlsa_domain domain] [-dane_tlsa_rrdata rrdata]
20 [-dane_ee_no_namechecks] [-reconnect] [-showcerts] [-prexit] [-debug]
21 [-trace] [-nocommands] [-security_debug] [-security_debug_verbose]
22 [-msg] [-timeout] [-mtu size] [-no_etm] [-keymatexport label]
23 [-keymatexportlen len] [-msgfile filename] [-nbio_test] [-state]
24 [-nbio] [-crlf] [-ign_eof] [-no_ign_eof] [-psk_identity identity] [-psk
25 key] [-psk_session file] [-quiet] [-sctp] [-sctp_label_bug]
26 [-fallback_scsv] [-async] [-maxfraglen len] [-max_send_frag]
27 [-split_send_frag] [-max_pipelines] [-read_buf]
28 [-ignore_unexpected_eof] [-bugs] [-comp] [-no_comp] [-brief]
29 [-legacy_server_connect] [-no_legacy_server_connect]
30 [-allow_no_dhe_kex] [-sigalgs sigalglist] [-curves curvelist] [-cipher
31 cipherlist] [-ciphersuites val] [-serverpref] [-starttls protocol]
32 [-name hostname] [-xmpphost hostname] [-name hostname] [-tlsextdebug]
33 [-no_ticket] [-sess_out filename] [-serverinfo types] [-sess_in
34 filename] [-serverinfo types] [-status] [-alpn protocols]
35 [-nextprotoneg protocols] [-ct] [-noct] [-ctlogfile] [-keylogfile file]
36 [-early_data file] [-enable_pha] [-use_srtp value] [-srpuser value]
37 [-srppass value] [-srp_lateuser] [-srp_moregroups] [-srp_strength
38 number] [-nameopt option] [-no_ssl3] [-no_tls1] [-no_tls1_1]
39 [-no_tls1_2] [-no_tls1_3] [-ssl3] [-tls1] [-tls1_1] [-tls1_2] [-tls1_3]
40 [-dtls] [-dtls1] [-dtls1_2] [-xkey infile] [-xcert file] [-xchain file]
41 [-xchain_build file] [-xcertform DER|PEM]> [-xkeyform DER|PEM]>
42 [-CAfile file] [-no-CAfile] [-CApath dir] [-no-CApath] [-CAstore uri]
43 [-no-CAstore] [-bugs] [-no_comp] [-comp] [-no_ticket] [-serverpref]
44 [-client_renegotiation] [-legacy_renegotiation] [-no_renegotiation]
45 [-no_resumption_on_reneg] [-legacy_server_connect]
46 [-no_legacy_server_connect] [-no_etm] [-allow_no_dhe_kex]
47 [-prioritize_chacha] [-strict] [-sigalgs algs] [-client_sigalgs algs]
48 [-groups groups] [-curves curves] [-named_curve curve] [-cipher
49 ciphers] [-ciphersuites 1.3ciphers] [-min_protocol minprot]
50 [-max_protocol maxprot] [-record_padding padding]
51 [-debug_broken_protocol] [-no_middlebox] [-rand files] [-writerand
52 file] [-provider name] [-provider-path path] [-propquery propq]
53 [-engine id] [-ssl_client_engine id] [-allow_proxy_certs] [-attime
54 timestamp] [-no_check_time] [-check_ss_sig] [-crl_check]
55 [-crl_check_all] [-explicit_policy] [-extended_crl] [-ignore_critical]
56 [-inhibit_any] [-inhibit_map] [-partial_chain] [-policy arg]
57 [-policy_check] [-policy_print] [-purpose purpose] [-suiteB_128]
58 [-suiteB_128_only] [-suiteB_192] [-trusted_first] [-no_alt_chains]
59 [-use_deltas] [-auth_level num] [-verify_depth num] [-verify_email
60 email] [-verify_hostname hostname] [-verify_ip ip] [-verify_name name]
61 [-x509_strict] [-issuer_checks] [host:port]
62
64 This command implements a generic SSL/TLS client which connects to a
65 remote host using SSL/TLS. It is a very useful diagnostic tool for SSL
66 servers.
67
69 In addition to the options below, this command also supports the common
70 and client only options documented in the "Supported Command Line
71 Commands" section of the SSL_CONF_cmd(3) manual page.
72 -help
74 Print out a usage message.
75 -ssl_config section
77 Use the specified section of the configuration file to configure
78 the SSL_CTX object.
79 -connect host:port
81 This specifies the host and optional port to connect to. It is
82 possible to select the host and port using the optional target
83 positional argument instead. If neither this nor the target
84 positional argument are specified then an attempt is made to
85 connect to the local host on port 4433.
86 -host hostname
88 Host to connect to; use -connect instead.
89 -port port
91 Connect to the specified port; use -connect instead.
92 -bind host:port
94 This specifies the host address and or port to bind as the source
95 for the connection. For Unix-domain sockets the port is ignored
96 and the host is used as the source socket address.
97 -proxy host:port
99 When used with the -connect flag, the program uses the host and
100 port specified with this flag and issues an HTTP CONNECT command to
101 connect to the desired server.
102 -proxy_user userid
104 When used with the -proxy flag, the program will attempt to
105 authenticate with the specified proxy using basic (base64)
106 authentication. NB: Basic authentication is insecure; the
107 credentials are sent to the proxy in easily reversible base64
108 encoding before any TLS/SSL session is established. Therefore,
109 these credentials are easily recovered by anyone able to
110 sniff/trace the network. Use with caution.
111 -proxy_pass arg
113 The proxy password source, used with the -proxy_user flag. For
114 more information about the format of arg see
115 openssl-passphrase-options(1).
116 -unix path
118 Connect over the specified Unix-domain socket.
119 -4 Use IPv4 only.
121 -6 Use IPv6 only.
123 -servername name
125 Set the TLS SNI (Server Name Indication) extension in the
126 ClientHello message to the given value. If -servername is not
127 provided, the TLS SNI extension will be populated with the name
128 given to -connect if it follows a DNS name format. If -connect is
129 not provided either, the SNI is set to "localhost". This is the
130 default since OpenSSL 1.1.1.
131 Even though SNI should normally be a DNS name and not an IP
133 address, if -servername is provided then that name will be sent,
134 regardless of whether it is a DNS name or not.
135 This option cannot be used in conjunction with -noservername.
137 -noservername
139 Suppresses sending of the SNI (Server Name Indication) extension in
140 the ClientHello message. Cannot be used in conjunction with the
141 -servername or -dane_tlsa_domain options.
142 -cert filename
144 The client certificate to use, if one is requested by the server.
145 The default is not to use a certificate.
146 The chain for the client certificate may be specified using
148 -cert_chain.
149 -certform DER|PEM|P12
151 The client certificate file format to use; unspecified by default.
152 See openssl-format-options(1) for details.
153 -cert_chain
155 A file or URI of untrusted certificates to use when attempting to
156 build the certificate chain related to the certificate specified
157 via the -cert option. The input can be in PEM, DER, or PKCS#12
158 format.
159 -build_chain
161 Specify whether the application should build the client certificate
162 chain to be provided to the server.
163 -CRL filename
165 CRL file to use to check the server's certificate.
166 -CRLform DER|PEM
168 The CRL file format; unspecified by default. See
169 openssl-format-options(1) for details.
170 -crl_download
172 Download CRL from distribution points in the certificate.
173 -key filename|uri
175 The client private key to use. If not specified then the
176 certificate file will be used to read also the key.
177 -keyform DER|PEM|P12|ENGINE
179 The key format; unspecified by default. See
180 openssl-format-options(1) for details.
181 -pass arg
183 the private key and certificate file password source. For more
184 information about the format of arg see
185 openssl-passphrase-options(1).
186 -verify depth
188 The verify depth to use. This specifies the maximum length of the
189 server certificate chain and turns on server certificate
190 verification. Currently the verify operation continues after
191 errors so all the problems with a certificate chain can be seen. As
192 a side effect the connection will never fail due to a server
193 certificate verify failure.
194 -verify_return_error
196 Return verification errors instead of continuing. This will
197 typically abort the handshake with a fatal error.
198 -verify_quiet
200 Limit verify output to only errors.
201 -verifyCAfile filename
203 A file in PEM format containing trusted certificates to use for
204 verifying the server's certificate.
205 -verifyCApath dir
207 A directory containing trusted certificates to use for verifying
208 the server's certificate. This directory must be in "hash format",
209 see openssl-verify(1) for more information.
210 -verifyCAstore uri
212 The URI of a store containing trusted certificates to use for
213 verifying the server's certificate.
214 -chainCAfile file
216 A file in PEM format containing trusted certificates to use when
217 attempting to build the client certificate chain.
218 -chainCApath directory
220 A directory containing trusted certificates to use for building the
221 client certificate chain provided to the server. This directory
222 must be in "hash format", see openssl-verify(1) for more
223 information.
224 -chainCAstore uri
226 The URI of a store containing trusted certificates to use when
227 attempting to build the client certificate chain. The URI may
228 indicate a single certificate, as well as a collection of them.
229 With URIs in the "file:" scheme, this acts as -chainCAfile or
230 -chainCApath, depending on if the URI indicates a directory or a
231 single file. See ossl_store-file(7) for more information on the
232 "file:" scheme.
233 -requestCAfile file
235 A file containing a list of certificates whose subject names will
236 be sent to the server in the certificate_authorities extension.
237 Only supported for TLS 1.3
238 -dane_tlsa_domain domain
240 Enable RFC6698/RFC7671 DANE TLSA authentication and specify the
241 TLSA base domain which becomes the default SNI hint and the primary
242 reference identifier for hostname checks. This must be used in
243 combination with at least one instance of the -dane_tlsa_rrdata
244 option below.
245 When DANE authentication succeeds, the diagnostic output will
247 include the lowest (closest to 0) depth at which a TLSA record
248 authenticated a chain certificate. When that TLSA record is a "2 1
249 0" trust anchor public key that signed (rather than matched) the
250 top-most certificate of the chain, the result is reported as "TA
251 public key verified". Otherwise, either the TLSA record "matched
252 TA certificate" at a positive depth or else "matched EE
253 certificate" at depth 0.
254 -dane_tlsa_rrdata rrdata
256 Use one or more times to specify the RRDATA fields of the DANE TLSA
257 RRset associated with the target service. The rrdata value is
258 specified in "presentation form", that is four whitespace separated
259 fields that specify the usage, selector, matching type and
260 associated data, with the last of these encoded in hexadecimal.
261 Optional whitespace is ignored in the associated data field. For
262 example:
263 $ openssl s_client -brief -starttls smtp \
265 -connect smtp.example.com:25 \
266 -dane_tlsa_domain smtp.example.com \
267 -dane_tlsa_rrdata "2 1 1
268 B111DD8A1C2091A89BD4FD60C57F0716CCE50FEEFF8137CDBEE0326E 02CF362B" \
269 -dane_tlsa_rrdata "2 1 1
270 60B87575447DCBA2A36B7D11AC09FB24A9DB406FEE12D2CC90180517 616E8A18"
271 ...
272 Verification: OK
273 Verified peername: smtp.example.com
274 DANE TLSA 2 1 1 ...ee12d2cc90180517616e8a18 matched TA certificate at depth 1
275 ...
276 -dane_ee_no_namechecks
278 This disables server name checks when authenticating via DANE-EE(3)
279 TLSA records. For some applications, primarily web browsers, it is
280 not safe to disable name checks due to "unknown key share" attacks,
281 in which a malicious server can convince a client that a connection
282 to a victim server is instead a secure connection to the malicious
283 server. The malicious server may then be able to violate cross-
284 origin scripting restrictions. Thus, despite the text of RFC7671,
285 name checks are by default enabled for DANE-EE(3) TLSA records, and
286 can be disabled in applications where it is safe to do so. In
287 particular, SMTP and XMPP clients should set this option as SRV and
288 MX records already make it possible for a remote domain to redirect
289 client connections to any server of its choice, and in any case
290 SMTP and XMPP clients do not execute scripts downloaded from remote
291 servers.
292 -reconnect
294 Reconnects to the same server 5 times using the same session ID,
295 this can be used as a test that session caching is working.
296 -showcerts
298 Displays the server certificate list as sent by the server: it only
299 consists of certificates the server has sent (in the order the
300 server has sent them). It is not a verified chain.
301 -prexit
303 Print session information when the program exits. This will always
304 attempt to print out information even if the connection fails.
305 Normally information will only be printed out once if the
306 connection succeeds. This option is useful because the cipher in
307 use may be renegotiated or the connection may fail because a client
308 certificate is required or is requested only after an attempt is
309 made to access a certain URL. Note: the output produced by this
310 option is not always accurate because a connection might never have
311 been established.
312 -state
314 Prints out the SSL session states.
315 -debug
317 Print extensive debugging information including a hex dump of all
318 traffic.
319 -nocommands
321 Do not use interactive command letters.
322 -security_debug
324 Enable security debug messages.
325 -security_debug_verbose
327 Output more security debug output.
328 -msg
330 Show protocol messages.
331 -timeout
333 Enable send/receive timeout on DTLS connections.
334 -mtu size
336 Set MTU of the link layer to the specified size.
337 -no_etm
339 Disable Encrypt-then-MAC negotiation.
340 -keymatexport label
342 Export keying material using the specified label.
343 -keymatexportlen len
345 Export the specified number of bytes of keying material; default is
346 20.
347 Show all protocol messages with hex dump.
349 -trace
351 Show verbose trace output of protocol messages.
352 -msgfile filename
354 File to send output of -msg or -trace to, default standard output.
355 -nbio_test
357 Tests nonblocking I/O
358 -nbio
360 Turns on nonblocking I/O
361 -crlf
363 This option translated a line feed from the terminal into CR+LF as
364 required by some servers.
365 -ign_eof
367 Inhibit shutting down the connection when end of file is reached in
368 the input.
369 -quiet
371 Inhibit printing of session and certificate information. This
372 implicitly turns on -ign_eof as well.
373 -no_ign_eof
375 Shut down the connection when end of file is reached in the input.
376 Can be used to override the implicit -ign_eof after -quiet.
377 -psk_identity identity
379 Use the PSK identity identity when using a PSK cipher suite. The
380 default value is "Client_identity" (without the quotes).
381 -psk key
383 Use the PSK key key when using a PSK cipher suite. The key is given
384 as a hexadecimal number without leading 0x, for example -psk
385 1a2b3c4d. This option must be provided in order to use a PSK
386 cipher.
387 -psk_session file
389 Use the pem encoded SSL_SESSION data stored in file as the basis of
390 a PSK. Note that this will only work if TLSv1.3 is negotiated.
391 -sctp
393 Use SCTP for the transport protocol instead of UDP in DTLS. Must be
394 used in conjunction with -dtls, -dtls1 or -dtls1_2. This option is
395 only available where OpenSSL has support for SCTP enabled.
396 -sctp_label_bug
398 Use the incorrect behaviour of older OpenSSL implementations when
399 computing endpoint-pair shared secrets for DTLS/SCTP. This allows
400 communication with older broken implementations but breaks
401 interoperability with correct implementations. Must be used in
402 conjunction with -sctp. This option is only available where OpenSSL
403 has support for SCTP enabled.
404 -fallback_scsv
406 Send TLS_FALLBACK_SCSV in the ClientHello.
407 -async
409 Switch on asynchronous mode. Cryptographic operations will be
410 performed asynchronously. This will only have an effect if an
411 asynchronous capable engine is also used via the -engine option.
412 For test purposes the dummy async engine (dasync) can be used (if
413 available).
414 -maxfraglen len
416 Enable Maximum Fragment Length Negotiation; allowed values are 512,
417 1024, 2048, and 4096.
418 -max_send_frag int
420 The maximum size of data fragment to send. See
421 SSL_CTX_set_max_send_fragment(3) for further information.
422 -split_send_frag int
424 The size used to split data for encrypt pipelines. If more data is
425 written in one go than this value then it will be split into
426 multiple pipelines, up to the maximum number of pipelines defined
427 by max_pipelines. This only has an effect if a suitable cipher
428 suite has been negotiated, an engine that supports pipelining has
429 been loaded, and max_pipelines is greater than 1. See
430 SSL_CTX_set_split_send_fragment(3) for further information.
431 -max_pipelines int
433 The maximum number of encrypt/decrypt pipelines to be used. This
434 will only have an effect if an engine has been loaded that supports
435 pipelining (e.g. the dasync engine) and a suitable cipher suite has
436 been negotiated. The default value is 1. See
437 SSL_CTX_set_max_pipelines(3) for further information.
438 -read_buf int
440 The default read buffer size to be used for connections. This will
441 only have an effect if the buffer size is larger than the size that
442 would otherwise be used and pipelining is in use (see
443 SSL_CTX_set_default_read_buffer_len(3) for further information).
444 -ignore_unexpected_eof
446 Some TLS implementations do not send the mandatory close_notify
447 alert on shutdown. If the application tries to wait for the
448 close_notify alert but the peer closes the connection without
449 sending it, an error is generated. When this option is enabled the
450 peer does not need to send the close_notify alert and a closed
451 connection will be treated as if the close_notify alert was
452 received. For more information on shutting down a connection, see
453 SSL_shutdown(3).
454 -bugs
456 There are several known bugs in SSL and TLS implementations. Adding
457 this option enables various workarounds.
458 -comp
460 Enables support for SSL/TLS compression. This option was
461 introduced in OpenSSL 1.1.0. TLS compression is not recommended
462 and is off by default as of OpenSSL 1.1.0.
463 -no_comp
465 Disables support for SSL/TLS compression. TLS compression is not
466 recommended and is off by default as of OpenSSL 1.1.0.
467 -brief
469 Only provide a brief summary of connection parameters instead of
470 the normal verbose output.
471 -sigalgs sigalglist
473 Specifies the list of signature algorithms that are sent by the
474 client. The server selects one entry in the list based on its
475 preferences. For example strings, see SSL_CTX_set1_sigalgs(3)
476 -curves curvelist
478 Specifies the list of supported curves to be sent by the client.
479 The curve is ultimately selected by the server. For a list of all
480 curves, use:
481 $ openssl ecparam -list_curves
483 -cipher cipherlist
485 This allows the TLSv1.2 and below cipher list sent by the client to
486 be modified. This list will be combined with any TLSv1.3
487 ciphersuites that have been configured. Although the server
488 determines which ciphersuite is used it should take the first
489 supported cipher in the list sent by the client. See
490 openssl-ciphers(1) for more information.
491 -ciphersuites val
493 This allows the TLSv1.3 ciphersuites sent by the client to be
494 modified. This list will be combined with any TLSv1.2 and below
495 ciphersuites that have been configured. Although the server
496 determines which cipher suite is used it should take the first
497 supported cipher in the list sent by the client. See
498 openssl-ciphers(1) for more information. The format for this list
499 is a simple colon (":") separated list of TLSv1.3 ciphersuite
500 names.
501 -starttls protocol
503 Send the protocol-specific message(s) to switch to TLS for
504 communication. protocol is a keyword for the intended protocol.
505 Currently, the only supported keywords are "smtp", "pop3", "imap",
506 "ftp", "xmpp", "xmpp-server", "irc", "postgres", "mysql", "lmtp",
507 "nntp", "sieve" and "ldap".
508 -xmpphost hostname
510 This option, when used with "-starttls xmpp" or "-starttls xmpp-
511 server", specifies the host for the "to" attribute of the stream
512 element. If this option is not specified, then the host specified
513 with "-connect" will be used.
514 This option is an alias of the -name option for "xmpp" and "xmpp-
516 server".
517 -name hostname
519 This option is used to specify hostname information for various
520 protocols used with -starttls option. Currently only "xmpp", "xmpp-
521 server", "smtp" and "lmtp" can utilize this -name option.
522 If this option is used with "-starttls xmpp" or "-starttls xmpp-
524 server", if specifies the host for the "to" attribute of the stream
525 element. If this option is not specified, then the host specified
526 with "-connect" will be used.
527 If this option is used with "-starttls lmtp" or "-starttls smtp",
529 it specifies the name to use in the "LMTP LHLO" or "SMTP EHLO"
530 message, respectively. If this option is not specified, then
531 "mail.example.com" will be used.
532 -tlsextdebug
534 Print out a hex dump of any TLS extensions received from the
535 server.
536 -no_ticket
538 Disable RFC4507bis session ticket support.
539 -sess_out filename
541 Output SSL session to filename.
542 -sess_in filename
544 Load SSL session from filename. The client will attempt to resume a
545 connection from this session.
546 -serverinfo types
548 A list of comma-separated TLS Extension Types (numbers between 0
549 and 65535). Each type will be sent as an empty ClientHello TLS
550 Extension. The server's response (if any) will be encoded and
551 displayed as a PEM file.
552 -status
554 Sends a certificate status request to the server (OCSP stapling).
555 The server response (if any) is printed out.
556 -alpn protocols, -nextprotoneg protocols
558 These flags enable the Enable the Application-Layer Protocol
559 Negotiation or Next Protocol Negotiation (NPN) extension,
560 respectively. ALPN is the IETF standard and replaces NPN. The
561 protocols list is a comma-separated list of protocol names that the
562 client should advertise support for. The list should contain the
563 most desirable protocols first. Protocol names are printable ASCII
564 strings, for example "http/1.1" or "spdy/3". An empty list of
565 protocols is treated specially and will cause the client to
566 advertise support for the TLS extension but disconnect just after
567 receiving ServerHello with a list of server supported protocols.
568 The flag -nextprotoneg cannot be specified if -tls1_3 is used.
569 -ct, -noct
571 Use one of these two options to control whether Certificate
572 Transparency (CT) is enabled (-ct) or disabled (-noct). If CT is
573 enabled, signed certificate timestamps (SCTs) will be requested
574 from the server and reported at handshake completion.
575 Enabling CT also enables OCSP stapling, as this is one possible
577 delivery method for SCTs.
578 -ctlogfile
580 A file containing a list of known Certificate Transparency logs.
581 See SSL_CTX_set_ctlog_list_file(3) for the expected file format.
582 -keylogfile file
584 Appends TLS secrets to the specified keylog file such that external
585 programs (like Wireshark) can decrypt TLS connections.
586 -early_data file
588 Reads the contents of the specified file and attempts to send it as
589 early data to the server. This will only work with resumed sessions
590 that support early data and when the server accepts the early data.
591 -enable_pha
593 For TLSv1.3 only, send the Post-Handshake Authentication extension.
594 This will happen whether or not a certificate has been provided via
595 -cert.
596 -use_srtp value
598 Offer SRTP key management, where value is a colon-separated profile
599 list.
600 -srpuser value
602 Set the SRP username to the specified value. This option is
603 deprecated.
604 -srppass value
606 Set the SRP password to the specified value. This option is
607 deprecated.
608 -srp_lateuser
610 SRP username for the second ClientHello message. This option is
611 deprecated.
612 -srp_moregroups This option is deprecated.
614 Tolerate other than the known g and N values.
615 -srp_strength number
617 Set the minimal acceptable length, in bits, for N. This option is
618 deprecated.
619 -no_ssl3, -no_tls1, -no_tls1_1, -no_tls1_2, -no_tls1_3, -ssl3, -tls1,
621 -tls1_1, -tls1_2, -tls1_3
622 See "TLS Version Options" in openssl(1).
623 -dtls, -dtls1, -dtls1_2
625 These specify the use of DTLS instead of TLS. See "TLS Version
626 Options" in openssl(1).
627 -nameopt option
629 This specifies how the subject or issuer names are displayed. See
630 openssl-namedisplay-options(1) for details.
631 -xkey infile, -xcert file, -xchain file, -xchain_build file, -xcertform
633 DER|PEM, -xkeyform DER|PEM
634 Set extended certificate verification options. See "Extended
635 Verification Options" in openssl-verification-options(1) for
636 details.
637 -CAfile file, -no-CAfile, -CApath dir, -no-CApath, -CAstore uri,
639 -no-CAstore
640 See "Trusted Certificate Options" in
641 openssl-verification-options(1) for details.
642 -bugs, -comp, -no_comp, -no_ticket, -serverpref, -client_renegotiation,
644 -legacy_renegotiation, -no_renegotiation, -no_resumption_on_reneg,
645 -legacy_server_connect, -no_legacy_server_connect, -no_etm
646 -allow_no_dhe_kex, -prioritize_chacha, -strict, -sigalgs algs,
647 -client_sigalgs algs, -groups groups, -curves curves, -named_curve
648 curve, -cipher ciphers, -ciphersuites 1.3ciphers, -min_protocol
649 minprot, -max_protocol maxprot, -record_padding padding,
650 -debug_broken_protocol, -no_middlebox
651 See "SUPPORTED COMMAND LINE COMMANDS" in SSL_CONF_cmd(3) for
652 details.
653 -rand files, -writerand file
655 See "Random State Options" in openssl(1) for details.
656 -provider name
658 -provider-path path
659 -propquery propq
660 See "Provider Options" in openssl(1), provider(7), and property(7).
661 -engine id
663 See "Engine Options" in openssl(1). This option is deprecated.
664 -ssl_client_engine id
666 Specify engine to be used for client certificate operations.
667 -allow_proxy_certs, -attime, -no_check_time, -check_ss_sig, -crl_check,
669 -crl_check_all, -explicit_policy, -extended_crl, -ignore_critical,
670 -inhibit_any, -inhibit_map, -no_alt_chains, -partial_chain, -policy,
671 -policy_check, -policy_print, -purpose, -suiteB_128, -suiteB_128_only,
672 -suiteB_192, -trusted_first, -use_deltas, -auth_level, -verify_depth,
673 -verify_email, -verify_hostname, -verify_ip, -verify_name, -x509_strict
674 -issuer_checks
675 Set various options of certificate chain verification. See
676 "Verification Options" in openssl-verification-options(1) for
677 details.
678 Verification errors are displayed, for debugging, but the command
680 will proceed unless the -verify_return_error option is used.
681 host:port
683 Rather than providing -connect, the target hostname and optional
684 port may be provided as a single positional argument after all
685 options. If neither this nor -connect are provided, falls back to
686 attempting to connect to localhost on port 4433.
687
689 If a connection is established with an SSL server then any data
690 received from the server is displayed and any key presses will be sent
691 to the server. If end of file is reached then the connection will be
692 closed down. When used interactively (which means neither -quiet nor
693 -ign_eof have been given), then certain commands are also recognized
694 which perform special operations. These commands are a letter which
695 must appear at the start of a line. They are listed below.
696 Q End the current SSL connection and exit.
698 R Renegotiate the SSL session (TLSv1.2 and below only).
700 k Send a key update message to the server (TLSv1.3 only)
702 K Send a key update message to the server and request one back
704 (TLSv1.3 only)
705
707 This command can be used to debug SSL servers. To connect to an SSL
708 HTTP server the command:
709 openssl s_client -connect servername:443
711 would typically be used (https uses port 443). If the connection
713 succeeds then an HTTP command can be given such as "GET /" to retrieve
714 a web page.
715 If the handshake fails then there are several possible causes, if it is
717 nothing obvious like no client certificate then the -bugs, -ssl3,
718 -tls1, -no_ssl3, -no_tls1 options can be tried in case it is a buggy
719 server. In particular you should play with these options before
720 submitting a bug report to an OpenSSL mailing list.
721 A frequent problem when attempting to get client certificates working
723 is that a web client complains it has no certificates or gives an empty
724 list to choose from. This is normally because the server is not sending
725 the clients certificate authority in its "acceptable CA list" when it
726 requests a certificate. By using this command, the CA list can be
727 viewed and checked. However, some servers only request client
728 authentication after a specific URL is requested. To obtain the list in
729 this case it is necessary to use the -prexit option and send an HTTP
730 request for an appropriate page.
731 If a certificate is specified on the command line using the -cert
733 option it will not be used unless the server specifically requests a
734 client certificate. Therefore, merely including a client certificate on
735 the command line is no guarantee that the certificate works.
736 If there are problems verifying a server certificate then the
738 -showcerts option can be used to show all the certificates sent by the
739 server.
740 This command is a test tool and is designed to continue the handshake
742 after any certificate verification errors. As a result it will accept
743 any certificate chain (trusted or not) sent by the peer. Non-test
744 applications should not do this as it makes them vulnerable to a MITM
745 attack. This behaviour can be changed by with the -verify_return_error
746 option: any verify errors are then returned aborting the handshake.
747 The -bind option may be useful if the server or a firewall requires
749 connections to come from some particular address and or port.
750
752 Because this program has a lot of options and also because some of the
753 techniques used are rather old, the C source for this command is rather
754 hard to read and not a model of how things should be done. A typical
755 SSL client program would be much simpler.
756 The -prexit option is a bit of a hack. We should really report
758 information whenever a session is renegotiated.
759
761 openssl(1), openssl-sess_id(1), openssl-s_server(1),
762 openssl-ciphers(1), SSL_CONF_cmd(3), SSL_CTX_set_max_send_fragment(3),
763 SSL_CTX_set_split_send_fragment(3), SSL_CTX_set_max_pipelines(3),
764 ossl_store-file(7)
765
767 The -no_alt_chains option was added in OpenSSL 1.1.0. The -name option
768 was added in OpenSSL 1.1.1.
769 The -certform option has become obsolete in OpenSSL 3.0.0 and has no
771 effect.
772 The -engine option was deprecated in OpenSSL 3.0.
774
776 Copyright 2000-2022 The OpenSSL Project Authors. All Rights Reserved.
777 Licensed under the Apache License 2.0 (the "License"). You may not use
779 this file except in compliance with the License. You can obtain a copy
780 in the file LICENSE in the source distribution or at
781 <https://www.openssl.org/source/license.html>.
7823.1.1 2023-08-31 OPENSSL-S_CLIENT(1ossl)