1S_CLIENT(1) OpenSSL S_CLIENT(1)
2
6 openssl-s_client, s_client - SSL/TLS client program
7
9 openssl s_client [-help] [-connect host:port] [-bind host:port] [-proxy
10 host:port] [-unix path] [-4] [-6] [-servername name] [-noservername]
11 [-verify depth] [-verify_return_error] [-cert filename] [-certform
12 DER|PEM] [-key filename] [-keyform DER|PEM] [-cert_chain filename]
13 [-build_chain] [-xkey] [-xcert] [-xchain] [-xchain_build] [-xcertform
14 PEM|DER] [-xkeyform PEM|DER] [-pass arg] [-CApath directory] [-CAfile
15 filename] [-chainCApath directory] [-chainCAfile filename] [-no-CAfile]
16 [-no-CApath] [-requestCAfile filename] [-dane_tlsa_domain domain]
17 [-dane_tlsa_rrdata rrdata] [-dane_ee_no_namechecks] [-attime timestamp]
18 [-check_ss_sig] [-crl_check] [-crl_check_all] [-explicit_policy]
19 [-extended_crl] [-ignore_critical] [-inhibit_any] [-inhibit_map]
20 [-no_check_time] [-partial_chain] [-policy arg] [-policy_check]
21 [-policy_print] [-purpose purpose] [-suiteB_128] [-suiteB_128_only]
22 [-suiteB_192] [-trusted_first] [-no_alt_chains] [-use_deltas]
23 [-auth_level num] [-nameopt option] [-verify_depth num] [-verify_email
24 email] [-verify_hostname hostname] [-verify_ip ip] [-verify_name name]
25 [-build_chain] [-x509_strict] [-reconnect] [-showcerts] [-debug] [-msg]
26 [-nbio_test] [-state] [-nbio] [-crlf] [-ign_eof] [-no_ign_eof]
27 [-psk_identity identity] [-psk key] [-psk_session file] [-quiet]
28 [-ssl3] [-tls1] [-tls1_1] [-tls1_2] [-tls1_3] [-no_ssl3] [-no_tls1]
29 [-no_tls1_1] [-no_tls1_2] [-no_tls1_3] [-dtls] [-dtls1] [-dtls1_2]
30 [-sctp] [-sctp_label_bug] [-fallback_scsv] [-async] [-max_send_frag]
31 [-split_send_frag] [-max_pipelines] [-read_buf] [-bugs] [-comp]
32 [-no_comp] [-allow_no_dhe_kex] [-sigalgs sigalglist] [-curves
33 curvelist] [-cipher cipherlist] [-ciphersuites val] [-serverpref]
34 [-starttls protocol] [-xmpphost hostname] [-name hostname] [-engine id]
35 [-tlsextdebug] [-no_ticket] [-sess_out filename] [-sess_in filename]
36 [-rand file...] [-writerand file] [-serverinfo types] [-status] [-alpn
37 protocols] [-nextprotoneg protocols] [-ct] [-noct] [-ctlogfile]
38 [-keylogfile file] [-early_data file] [-enable_pha] [target]
39
41 The s_client command implements a generic SSL/TLS client which connects
42 to a remote host using SSL/TLS. It is a very useful diagnostic tool for
43 SSL servers.
44
46 In addition to the options below the s_client utility also supports the
47 common and client only options documented in the "Supported Command
48 Line Commands" section of the SSL_CONF_cmd(3) manual page.
49 -help
51 Print out a usage message.
52 -connect host:port
54 This specifies the host and optional port to connect to. It is
55 possible to select the host and port using the optional target
56 positional argument instead. If neither this nor the target
57 positional argument are specified then an attempt is made to
58 connect to the local host on port 4433.
59 -bind host:port]
61 This specifies the host address and or port to bind as the source
62 for the connection. For Unix-domain sockets the port is ignored
63 and the host is used as the source socket address.
64 -proxy host:port
66 When used with the -connect flag, the program uses the host and
67 port specified with this flag and issues an HTTP CONNECT command to
68 connect to the desired server.
69 -unix path
71 Connect over the specified Unix-domain socket.
72 -4 Use IPv4 only.
74 -6 Use IPv6 only.
76 -servername name
78 Set the TLS SNI (Server Name Indication) extension in the
79 ClientHello message to the given value. If -servername is not
80 provided, the TLS SNI extension will be populated with the name
81 given to -connect if it follows a DNS name format. If -connect is
82 not provided either, the SNI is set to "localhost". This is the
83 default since OpenSSL 1.1.1.
84 Even though SNI should normally be a DNS name and not an IP
86 address, if -servername is provided then that name will be sent,
87 regardless of whether it is a DNS name or not.
88 This option cannot be used in conjunction with -noservername.
90 -noservername
92 Suppresses sending of the SNI (Server Name Indication) extension in
93 the ClientHello message. Cannot be used in conjunction with the
94 -servername or <-dane_tlsa_domain> options.
95 -cert certname
97 The certificate to use, if one is requested by the server. The
98 default is not to use a certificate.
99 -certform format
101 The certificate format to use: DER or PEM. PEM is the default.
102 -key keyfile
104 The private key to use. If not specified then the certificate file
105 will be used.
106 -keyform format
108 The private format to use: DER or PEM. PEM is the default.
109 -cert_chain
111 A file containing trusted certificates to use when attempting to
112 build the client/server certificate chain related to the
113 certificate specified via the -cert option.
114 -build_chain
116 Specify whether the application should build the certificate chain
117 to be provided to the server.
118 -xkey infile, -xcert infile, -xchain
120 Specify an extra certificate, private key and certificate chain.
121 These behave in the same manner as the -cert, -key and -cert_chain
122 options. When specified, the callback returning the first valid
123 chain will be in use by the client.
124 -xchain_build
126 Specify whether the application should build the certificate chain
127 to be provided to the server for the extra certificates provided
128 via -xkey infile, -xcert infile, -xchain options.
129 -xcertform PEM|DER, -xkeyform PEM|DER
131 Extra certificate and private key format respectively.
132 -pass arg
134 the private key password source. For more information about the
135 format of arg see the PASS PHRASE ARGUMENTS section in openssl(1).
136 -verify depth
138 The verify depth to use. This specifies the maximum length of the
139 server certificate chain and turns on server certificate
140 verification. Currently the verify operation continues after
141 errors so all the problems with a certificate chain can be seen. As
142 a side effect the connection will never fail due to a server
143 certificate verify failure.
144 -verify_return_error
146 Return verification errors instead of continuing. This will
147 typically abort the handshake with a fatal error.
148 -nameopt option
150 Option which determines how the subject or issuer names are
151 displayed. The option argument can be a single option or multiple
152 options separated by commas. Alternatively the -nameopt switch may
153 be used more than once to set multiple options. See the x509(1)
154 manual page for details.
155 -CApath directory
157 The directory to use for server certificate verification. This
158 directory must be in "hash format", see verify(1) for more
159 information. These are also used when building the client
160 certificate chain.
161 -CAfile file
163 A file containing trusted certificates to use during server
164 authentication and to use when attempting to build the client
165 certificate chain.
166 -chainCApath directory
168 The directory to use for building the chain provided to the server.
169 This directory must be in "hash format", see verify(1) for more
170 information.
171 -chainCAfile file
173 A file containing trusted certificates to use when attempting to
174 build the client certificate chain.
175 -no-CAfile
177 Do not load the trusted CA certificates from the default file
178 location
179 -no-CApath
181 Do not load the trusted CA certificates from the default directory
182 location
183 -requestCAfile file
185 A file containing a list of certificates whose subject names will
186 be sent to the server in the certificate_authorities extension.
187 Only supported for TLS 1.3
188 -dane_tlsa_domain domain
190 Enable RFC6698/RFC7671 DANE TLSA authentication and specify the
191 TLSA base domain which becomes the default SNI hint and the primary
192 reference identifier for hostname checks. This must be used in
193 combination with at least one instance of the -dane_tlsa_rrdata
194 option below.
195 When DANE authentication succeeds, the diagnostic output will
197 include the lowest (closest to 0) depth at which a TLSA record
198 authenticated a chain certificate. When that TLSA record is a "2 1
199 0" trust anchor public key that signed (rather than matched) the
200 top-most certificate of the chain, the result is reported as "TA
201 public key verified". Otherwise, either the TLSA record "matched
202 TA certificate" at a positive depth or else "matched EE
203 certificate" at depth 0.
204 -dane_tlsa_rrdata rrdata
206 Use one or more times to specify the RRDATA fields of the DANE TLSA
207 RRset associated with the target service. The rrdata value is
208 specified in "presentation form", that is four whitespace separated
209 fields that specify the usage, selector, matching type and
210 associated data, with the last of these encoded in hexadecimal.
211 Optional whitespace is ignored in the associated data field. For
212 example:
213 $ openssl s_client -brief -starttls smtp \
215 -connect smtp.example.com:25 \
216 -dane_tlsa_domain smtp.example.com \
217 -dane_tlsa_rrdata "2 1 1
218 B111DD8A1C2091A89BD4FD60C57F0716CCE50FEEFF8137CDBEE0326E 02CF362B" \
219 -dane_tlsa_rrdata "2 1 1
220 60B87575447DCBA2A36B7D11AC09FB24A9DB406FEE12D2CC90180517 616E8A18"
221 ...
222 Verification: OK
223 Verified peername: smtp.example.com
224 DANE TLSA 2 1 1 ...ee12d2cc90180517616e8a18 matched TA certificate at depth 1
225 ...
226 -dane_ee_no_namechecks
228 This disables server name checks when authenticating via DANE-EE(3)
229 TLSA records. For some applications, primarily web browsers, it is
230 not safe to disable name checks due to "unknown key share" attacks,
231 in which a malicious server can convince a client that a connection
232 to a victim server is instead a secure connection to the malicious
233 server. The malicious server may then be able to violate cross-
234 origin scripting restrictions. Thus, despite the text of RFC7671,
235 name checks are by default enabled for DANE-EE(3) TLSA records, and
236 can be disabled in applications where it is safe to do so. In
237 particular, SMTP and XMPP clients should set this option as SRV and
238 MX records already make it possible for a remote domain to redirect
239 client connections to any server of its choice, and in any case
240 SMTP and XMPP clients do not execute scripts downloaded from remote
241 servers.
242 -attime, -check_ss_sig, -crl_check, -crl_check_all, -explicit_policy,
244 -extended_crl, -ignore_critical, -inhibit_any, -inhibit_map,
245 -no_alt_chains, -no_check_time, -partial_chain, -policy, -policy_check,
246 -policy_print, -purpose, -suiteB_128, -suiteB_128_only, -suiteB_192,
247 -trusted_first, -use_deltas, -auth_level, -verify_depth, -verify_email,
248 -verify_hostname, -verify_ip, -verify_name, -x509_strict
249 Set various certificate chain validation options. See the verify(1)
250 manual page for details.
251 -reconnect
253 Reconnects to the same server 5 times using the same session ID,
254 this can be used as a test that session caching is working.
255 -showcerts
257 Displays the server certificate list as sent by the server: it only
258 consists of certificates the server has sent (in the order the
259 server has sent them). It is not a verified chain.
260 -prexit
262 Print session information when the program exits. This will always
263 attempt to print out information even if the connection fails.
264 Normally information will only be printed out once if the
265 connection succeeds. This option is useful because the cipher in
266 use may be renegotiated or the connection may fail because a client
267 certificate is required or is requested only after an attempt is
268 made to access a certain URL. Note: the output produced by this
269 option is not always accurate because a connection might never have
270 been established.
271 -state
273 Prints out the SSL session states.
274 -debug
276 Print extensive debugging information including a hex dump of all
277 traffic.
278 -msg
280 Show all protocol messages with hex dump.
281 -trace
283 Show verbose trace output of protocol messages. OpenSSL needs to be
284 compiled with enable-ssl-trace for this option to work.
285 -msgfile
287 File to send output of -msg or -trace to, default standard output.
288 -nbio_test
290 Tests non-blocking I/O
291 -nbio
293 Turns on non-blocking I/O
294 -crlf
296 This option translated a line feed from the terminal into CR+LF as
297 required by some servers.
298 -ign_eof
300 Inhibit shutting down the connection when end of file is reached in
301 the input.
302 -quiet
304 Inhibit printing of session and certificate information. This
305 implicitly turns on -ign_eof as well.
306 -no_ign_eof
308 Shut down the connection when end of file is reached in the input.
309 Can be used to override the implicit -ign_eof after -quiet.
310 -psk_identity identity
312 Use the PSK identity identity when using a PSK cipher suite. The
313 default value is "Client_identity" (without the quotes).
314 -psk key
316 Use the PSK key key when using a PSK cipher suite. The key is given
317 as a hexadecimal number without leading 0x, for example -psk
318 1a2b3c4d. This option must be provided in order to use a PSK
319 cipher.
320 -psk_session file
322 Use the pem encoded SSL_SESSION data stored in file as the basis of
323 a PSK. Note that this will only work if TLSv1.3 is negotiated.
324 -ssl3, -tls1, -tls1_1, -tls1_2, -tls1_3, -no_ssl3, -no_tls1,
326 -no_tls1_1, -no_tls1_2, -no_tls1_3
327 These options require or disable the use of the specified SSL or
328 TLS protocols. By default s_client will negotiate the highest
329 mutually supported protocol version. When a specific TLS version
330 is required, only that version will be offered to and accepted from
331 the server. Note that not all protocols and flags may be
332 available, depending on how OpenSSL was built.
333 -dtls, -dtls1, -dtls1_2
335 These options make s_client use DTLS protocols instead of TLS.
336 With -dtls, s_client will negotiate any supported DTLS protocol
337 version, whilst -dtls1 and -dtls1_2 will only support DTLS1.0 and
338 DTLS1.2 respectively.
339 -sctp
341 Use SCTP for the transport protocol instead of UDP in DTLS. Must be
342 used in conjunction with -dtls, -dtls1 or -dtls1_2. This option is
343 only available where OpenSSL has support for SCTP enabled.
344 -sctp_label_bug
346 Use the incorrect behaviour of older OpenSSL implementations when
347 computing endpoint-pair shared secrets for DTLS/SCTP. This allows
348 communication with older broken implementations but breaks
349 interoperability with correct implementations. Must be used in
350 conjunction with -sctp. This option is only available where OpenSSL
351 has support for SCTP enabled.
352 -fallback_scsv
354 Send TLS_FALLBACK_SCSV in the ClientHello.
355 -async
357 Switch on asynchronous mode. Cryptographic operations will be
358 performed asynchronously. This will only have an effect if an
359 asynchronous capable engine is also used via the -engine option.
360 For test purposes the dummy async engine (dasync) can be used (if
361 available).
362 -max_send_frag int
364 The maximum size of data fragment to send. See
365 SSL_CTX_set_max_send_fragment(3) for further information.
366 -split_send_frag int
368 The size used to split data for encrypt pipelines. If more data is
369 written in one go than this value then it will be split into
370 multiple pipelines, up to the maximum number of pipelines defined
371 by max_pipelines. This only has an effect if a suitable cipher
372 suite has been negotiated, an engine that supports pipelining has
373 been loaded, and max_pipelines is greater than 1. See
374 SSL_CTX_set_split_send_fragment(3) for further information.
375 -max_pipelines int
377 The maximum number of encrypt/decrypt pipelines to be used. This
378 will only have an effect if an engine has been loaded that supports
379 pipelining (e.g. the dasync engine) and a suitable cipher suite has
380 been negotiated. The default value is 1. See
381 SSL_CTX_set_max_pipelines(3) for further information.
382 -read_buf int
384 The default read buffer size to be used for connections. This will
385 only have an effect if the buffer size is larger than the size that
386 would otherwise be used and pipelining is in use (see
387 SSL_CTX_set_default_read_buffer_len(3) for further information).
388 -bugs
390 There are several known bugs in SSL and TLS implementations. Adding
391 this option enables various workarounds.
392 -comp
394 Enables support for SSL/TLS compression. This option was
395 introduced in OpenSSL 1.1.0. TLS compression is not recommended
396 and is off by default as of OpenSSL 1.1.0.
397 -no_comp
399 Disables support for SSL/TLS compression. TLS compression is not
400 recommended and is off by default as of OpenSSL 1.1.0.
401 -brief
403 Only provide a brief summary of connection parameters instead of
404 the normal verbose output.
405 -sigalgs sigalglist
407 Specifies the list of signature algorithms that are sent by the
408 client. The server selects one entry in the list based on its
409 preferences. For example strings, see SSL_CTX_set1_sigalgs(3)
410 -curves curvelist
412 Specifies the list of supported curves to be sent by the client.
413 The curve is ultimately selected by the server. For a list of all
414 curves, use:
415 $ openssl ecparam -list_curves
417 -cipher cipherlist
419 This allows the TLSv1.2 and below cipher list sent by the client to
420 be modified. This list will be combined with any TLSv1.3
421 ciphersuites that have been configured. Although the server
422 determines which ciphersuite is used it should take the first
423 supported cipher in the list sent by the client. See the ciphers
424 command for more information.
425 -ciphersuites val
427 This allows the TLSv1.3 ciphersuites sent by the client to be
428 modified. This list will be combined with any TLSv1.2 and below
429 ciphersuites that have been configured. Although the server
430 determines which cipher suite is used it should take the first
431 supported cipher in the list sent by the client. See the ciphers
432 command for more information. The format for this list is a simple
433 colon (":") separated list of TLSv1.3 ciphersuite names.
434 -starttls protocol
436 Send the protocol-specific message(s) to switch to TLS for
437 communication. protocol is a keyword for the intended protocol.
438 Currently, the only supported keywords are "smtp", "pop3", "imap",
439 "ftp", "xmpp", "xmpp-server", "irc", "postgres", "mysql", "lmtp",
440 "nntp", "sieve" and "ldap".
441 -xmpphost hostname
443 This option, when used with "-starttls xmpp" or "-starttls xmpp-
444 server", specifies the host for the "to" attribute of the stream
445 element. If this option is not specified, then the host specified
446 with "-connect" will be used.
447 This option is an alias of the -name option for "xmpp" and "xmpp-
449 server".
450 -name hostname
452 This option is used to specify hostname information for various
453 protocols used with -starttls option. Currently only "xmpp", "xmpp-
454 server", "smtp" and "lmtp" can utilize this -name option.
455 If this option is used with "-starttls xmpp" or "-starttls xmpp-
457 server", if specifies the host for the "to" attribute of the stream
458 element. If this option is not specified, then the host specified
459 with "-connect" will be used.
460 If this option is used with "-starttls lmtp" or "-starttls smtp",
462 it specifies the name to use in the "LMTP LHLO" or "SMTP EHLO"
463 message, respectively. If this option is not specified, then
464 "mail.example.com" will be used.
465 -tlsextdebug
467 Print out a hex dump of any TLS extensions received from the
468 server.
469 -no_ticket
471 Disable RFC4507bis session ticket support.
472 -sess_out filename
474 Output SSL session to filename.
475 -sess_in sess.pem
477 Load SSL session from filename. The client will attempt to resume a
478 connection from this session.
479 -engine id
481 Specifying an engine (by its unique id string) will cause s_client
482 to attempt to obtain a functional reference to the specified
483 engine, thus initialising it if needed. The engine will then be set
484 as the default for all available algorithms.
485 -rand file...
487 A file or files containing random data used to seed the random
488 number generator. Multiple files can be specified separated by an
489 OS-dependent character. The separator is ; for MS-Windows, , for
490 OpenVMS, and : for all others.
491 [-writerand file]
493 Writes random data to the specified file upon exit. This can be
494 used with a subsequent -rand flag.
495 -serverinfo types
497 A list of comma-separated TLS Extension Types (numbers between 0
498 and 65535). Each type will be sent as an empty ClientHello TLS
499 Extension. The server's response (if any) will be encoded and
500 displayed as a PEM file.
501 -status
503 Sends a certificate status request to the server (OCSP stapling).
504 The server response (if any) is printed out.
505 -alpn protocols, -nextprotoneg protocols
507 These flags enable the Enable the Application-Layer Protocol
508 Negotiation or Next Protocol Negotiation (NPN) extension,
509 respectively. ALPN is the IETF standard and replaces NPN. The
510 protocols list is a comma-separated list of protocol names that the
511 client should advertise support for. The list should contain the
512 most desirable protocols first. Protocol names are printable ASCII
513 strings, for example "http/1.1" or "spdy/3". An empty list of
514 protocols is treated specially and will cause the client to
515 advertise support for the TLS extension but disconnect just after
516 receiving ServerHello with a list of server supported protocols.
517 The flag -nextprotoneg cannot be specified if -tls1_3 is used.
518 -ct, -noct
520 Use one of these two options to control whether Certificate
521 Transparency (CT) is enabled (-ct) or disabled (-noct). If CT is
522 enabled, signed certificate timestamps (SCTs) will be requested
523 from the server and reported at handshake completion.
524 Enabling CT also enables OCSP stapling, as this is one possible
526 delivery method for SCTs.
527 -ctlogfile
529 A file containing a list of known Certificate Transparency logs.
530 See SSL_CTX_set_ctlog_list_file(3) for the expected file format.
531 -keylogfile file
533 Appends TLS secrets to the specified keylog file such that external
534 programs (like Wireshark) can decrypt TLS connections.
535 -early_data file
537 Reads the contents of the specified file and attempts to send it as
538 early data to the server. This will only work with resumed sessions
539 that support early data and when the server accepts the early data.
540 -enable_pha
542 For TLSv1.3 only, send the Post-Handshake Authentication extension.
543 This will happen whether or not a certificate has been provided via
544 -cert.
545 [target]
547 Rather than providing -connect, the target hostname and optional
548 port may be provided as a single positional argument after all
549 options. If neither this nor -connect are provided, falls back to
550 attempting to connect to localhost on port 4433.
551
553 If a connection is established with an SSL server then any data
554 received from the server is displayed and any key presses will be sent
555 to the server. If end of file is reached then the connection will be
556 closed down. When used interactively (which means neither -quiet nor
557 -ign_eof have been given), then certain commands are also recognized
558 which perform special operations. These commands are a letter which
559 must appear at the start of a line. They are listed below.
560 Q End the current SSL connection and exit.
562 R Renegotiate the SSL session (TLSv1.2 and below only).
564 B Send a heartbeat message to the server (DTLS only)
566 k Send a key update message to the server (TLSv1.3 only)
568 K Send a key update message to the server and request one back
570 (TLSv1.3 only)
571
573 s_client can be used to debug SSL servers. To connect to an SSL HTTP
574 server the command:
575 openssl s_client -connect servername:443
577 would typically be used (https uses port 443). If the connection
579 succeeds then an HTTP command can be given such as "GET /" to retrieve
580 a web page.
581 If the handshake fails then there are several possible causes, if it is
583 nothing obvious like no client certificate then the -bugs, -ssl3,
584 -tls1, -no_ssl3, -no_tls1 options can be tried in case it is a buggy
585 server. In particular you should play with these options before
586 submitting a bug report to an OpenSSL mailing list.
587 A frequent problem when attempting to get client certificates working
589 is that a web client complains it has no certificates or gives an empty
590 list to choose from. This is normally because the server is not sending
591 the clients certificate authority in its "acceptable CA list" when it
592 requests a certificate. By using s_client the CA list can be viewed and
593 checked. However some servers only request client authentication after
594 a specific URL is requested. To obtain the list in this case it is
595 necessary to use the -prexit option and send an HTTP request for an
596 appropriate page.
597 If a certificate is specified on the command line using the -cert
599 option it will not be used unless the server specifically requests a
600 client certificate. Therefor merely including a client certificate on
601 the command line is no guarantee that the certificate works.
602 If there are problems verifying a server certificate then the
604 -showcerts option can be used to show all the certificates sent by the
605 server.
606 The s_client utility is a test tool and is designed to continue the
608 handshake after any certificate verification errors. As a result it
609 will accept any certificate chain (trusted or not) sent by the peer.
610 None test applications should not do this as it makes them vulnerable
611 to a MITM attack. This behaviour can be changed by with the
612 -verify_return_error option: any verify errors are then returned
613 aborting the handshake.
614 The -bind option may be useful if the server or a firewall requires
616 connections to come from some particular address and or port.
617
619 Because this program has a lot of options and also because some of the
620 techniques used are rather old, the C source of s_client is rather hard
621 to read and not a model of how things should be done. A typical SSL
622 client program would be much simpler.
623 The -prexit option is a bit of a hack. We should really report
625 information whenever a session is renegotiated.
626
628 SSL_CONF_cmd(3), sess_id(1), s_server(1), ciphers(1),
629 SSL_CTX_set_max_send_fragment(3), SSL_CTX_set_split_send_fragment(3),
630 SSL_CTX_set_max_pipelines(3)
631
633 The -no_alt_chains option was added in OpenSSL 1.1.0. The -name option
634 was added in OpenSSL 1.1.1.
635
637 Copyright 2000-2020 The OpenSSL Project Authors. All Rights Reserved.
638 Licensed under the OpenSSL license (the "License"). You may not use
640 this file except in compliance with the License. You can obtain a copy
641 in the file LICENSE in the source distribution or at
642 <https://www.openssl.org/source/license.html>.
6431.1.1g 2020-04-23 S_CLIENT(1)