5 openssl-s_client - SSL/TLS client program
11 [B<-connect> I<host:port>]
12 [B<-bind> I<host:port>]
13 [B<-proxy> I<host:port>]
14 [B<-proxy_user> I<userid>]
15 [B<-proxy_pass> I<arg>]
19 [B<-servername> I<name>]
22 [B<-verify_return_error>]
23 [B<-cert> I<filename>]
24 [B<-certform> B<DER>|B<PEM>]
26 [B<-keyform> B<DER>|B<PEM>]
27 [B<-cert_chain> I<filename>]
33 [B<-xcertform> B<DER>|B<PEM>]
34 [B<-xkeyform> B<DER>|B<PEM>]
36 [B<-CApath> I<directory>]
37 [B<-CAfile> I<filename>]
38 [B<-chainCApath> I<directory>]
39 [B<-chainCAfile> I<filename>]
42 [B<-requestCAfile> I<filename>]
43 [B<-dane_tlsa_domain> I<domain>]
44 [B<-dane_tlsa_rrdata> I<rrdata>]
45 [B<-dane_ee_no_namechecks>]
46 [B<-attime> I<timestamp>]
60 [B<-purpose> I<purpose>]
67 [B<-auth_level> I<num>]
68 [B<-nameopt> I<option>]
69 [B<-verify_depth> I<num>]
70 [B<-verify_email> I<email>]
71 [B<-verify_hostname> I<hostname>]
73 [B<-verify_name> I<name>]
86 [B<-psk_identity> I<identity>]
88 [B<-psk_session> I<file>]
108 [B<-split_send_frag>]
114 [B<-allow_no_dhe_kex>]
115 [B<-sigalgs> I<sigalglist>]
116 [B<-curves> I<curvelist>]
117 [B<-cipher> I<cipherlist>]
118 [B<-ciphersuites> I<val>]
120 [B<-starttls> I<protocol>]
121 [B<-xmpphost> I<hostname>]
122 [B<-name> I<hostname>]
126 [B<-sess_out> I<filename>]
127 [B<-sess_in> I<filename>]
129 [B<-writerand> I<file>]
130 [B<-serverinfo> I<types>]
132 [B<-alpn> I<protocols>]
133 [B<-nextprotoneg> I<protocols>]
137 [B<-keylogfile> I<file>]
138 [B<-early_data> I<file>]
142 =for comment ifdef engine ssl_client_engine ct noct ctlogfile
144 =for comment ifdef ssl3 unix 4 6 use_srtp status trace wdebug nextprotoneg
146 =for comment ifdef ssl3 tls1 tls1_1 tls1_2 tls1_3 dtls mtu dtls1 dtls1_2
148 =for comment ifdef sctp_label_bug sctp
150 =for comment ifdef srpuser srppass srp_lateuser srp_moregroups srp_strength
154 This command implements a generic SSL/TLS client which
155 connects to a remote host using SSL/TLS. It is a I<very> useful diagnostic
156 tool for SSL servers.
160 In addition to the options below, this command also supports the
161 common and client only options documented
162 in the "Supported Command Line Commands" section of the L<SSL_CONF_cmd(3)>
169 Print out a usage message.
171 =item B<-connect> I<host>:I<port>
173 This specifies the host and optional port to connect to. It is possible to
174 select the host and port using the optional target positional argument instead.
175 If neither this nor the target positional argument are specified then an attempt
176 is made to connect to the local host on port 4433.
178 =item B<-bind> I<host:port>]
180 This specifies the host address and or port to bind as the source for the
181 connection. For Unix-domain sockets the port is ignored and the host is
182 used as the source socket address.
184 =item B<-proxy> I<host:port>
186 When used with the B<-connect> flag, the program uses the host and port
187 specified with this flag and issues an HTTP CONNECT command to connect
188 to the desired server.
190 =item B<-proxy_user> I<userid>
192 When used with the B<-proxy> flag, the program will attempt to authenticate
193 with the specified proxy using basic (base64) authentication.
194 NB: Basic authentication is insecure; the credentials are sent to the proxy
195 in easily reversible base64 encoding before any TLS/SSL session is established.
196 Therefore these credentials are easily recovered by anyone able to sniff/trace
197 the network. Use with caution.
199 =item B<-proxy_pass> I<arg>
201 The proxy password source, used with the B<-proxy_user> flag.
202 For more information about the format of B<arg>
203 see L<openssl(1)/Pass phrase options>.
205 =item B<-unix> I<path>
207 Connect over the specified Unix-domain socket.
217 =item B<-servername> I<name>
219 Set the TLS SNI (Server Name Indication) extension in the ClientHello message to
221 If B<-servername> is not provided, the TLS SNI extension will be populated with
222 the name given to B<-connect> if it follows a DNS name format. If B<-connect> is
223 not provided either, the SNI is set to "localhost".
224 This is the default since OpenSSL 1.1.1.
226 Even though SNI should normally be a DNS name and not an IP address, if
227 B<-servername> is provided then that name will be sent, regardless of whether
228 it is a DNS name or not.
230 This option cannot be used in conjunction with B<-noservername>.
232 =item B<-noservername>
234 Suppresses sending of the SNI (Server Name Indication) extension in the
235 ClientHello message. Cannot be used in conjunction with the B<-servername> or
236 <-dane_tlsa_domain> options.
238 =item B<-cert> I<certname>
240 The certificate to use, if one is requested by the server. The default is
241 not to use a certificate.
243 =item B<-certform> I<format>
245 The certificate format to use: DER or PEM. PEM is the default.
247 =item B<-key> I<keyfile>
249 The private key to use. If not specified then the certificate file will
252 =item B<-keyform> I<format>
254 The private format to use: DER or PEM. PEM is the default.
258 A file containing trusted certificates to use when attempting to build the
259 client/server certificate chain related to the certificate specified via the
262 =item B<-build_chain>
264 Specify whether the application should build the certificate chain to be
265 provided to the server.
267 =item B<-xkey> I<infile>, B<-xcert> I<infile>, B<-xchain>
269 Specify an extra certificate, private key and certificate chain. These behave
270 in the same manner as the B<-cert>, B<-key> and B<-cert_chain> options. When
271 specified, the callback returning the first valid chain will be in use by the
274 =item B<-xchain_build>
276 Specify whether the application should build the certificate chain to be
277 provided to the server for the extra certificates provided via B<-xkey> I<infile>,
278 B<-xcert> I<infile>, B<-xchain> options.
280 =item B<-xcertform> B<DER>|B<PEM>, B<-xkeyform> B<DER>|B<PEM>
282 Extra certificate and private key format respectively.
284 =item B<-pass> I<arg>
286 the private key password source. For more information about the format of I<arg>
287 see L<openssl(1)/Pass phrase options>.
289 =item B<-verify> I<depth>
291 The verify depth to use. This specifies the maximum length of the
292 server certificate chain and turns on server certificate verification.
293 Currently the verify operation continues after errors so all the problems
294 with a certificate chain can be seen. As a side effect the connection
295 will never fail due to a server certificate verify failure.
297 =item B<-verify_return_error>
299 Return verification errors instead of continuing. This will typically
300 abort the handshake with a fatal error.
302 =item B<-nameopt> I<option>
304 Option which determines how the subject or issuer names are displayed. The
305 I<option> argument can be a single option or multiple options separated by
306 commas. Alternatively the B<-nameopt> switch may be used more than once to
307 set multiple options. See the L<x509(1)> manual page for details.
309 =item B<-CApath> I<directory>
311 The directory to use for server certificate verification. This directory
312 must be in "hash format", see L<verify(1)> for more information. These are
313 also used when building the client certificate chain.
315 =item B<-CAfile> I<file>
317 A file containing trusted certificates to use during server authentication
318 and to use when attempting to build the client certificate chain.
320 =item B<-chainCApath> I<directory>
322 The directory to use for building the chain provided to the server. This
323 directory must be in "hash format", see L<verify(1)> for more information.
325 =item B<-chainCAfile> I<file>
327 A file containing trusted certificates to use when attempting to build the
328 client certificate chain.
332 Do not load the trusted CA certificates from the default file location
336 Do not load the trusted CA certificates from the default directory location
338 =item B<-requestCAfile> I<file>
340 A file containing a list of certificates whose subject names will be sent
341 to the server in the B<certificate_authorities> extension. Only supported
344 =item B<-dane_tlsa_domain> I<domain>
346 Enable RFC6698/RFC7671 DANE TLSA authentication and specify the
347 TLSA base domain which becomes the default SNI hint and the primary
348 reference identifier for hostname checks. This must be used in
349 combination with at least one instance of the B<-dane_tlsa_rrdata>
352 When DANE authentication succeeds, the diagnostic output will include
353 the lowest (closest to 0) depth at which a TLSA record authenticated
354 a chain certificate. When that TLSA record is a "2 1 0" trust
355 anchor public key that signed (rather than matched) the top-most
356 certificate of the chain, the result is reported as "TA public key
357 verified". Otherwise, either the TLSA record "matched TA certificate"
358 at a positive depth or else "matched EE certificate" at depth 0.
360 =item B<-dane_tlsa_rrdata> I<rrdata>
362 Use one or more times to specify the RRDATA fields of the DANE TLSA
363 RRset associated with the target service. The I<rrdata> value is
364 specied in "presentation form", that is four whitespace separated
365 fields that specify the usage, selector, matching type and associated
366 data, with the last of these encoded in hexadecimal. Optional
367 whitespace is ignored in the associated data field. For example:
369 $ openssl s_client -brief -starttls smtp \
370 -connect smtp.example.com:25 \
371 -dane_tlsa_domain smtp.example.com \
372 -dane_tlsa_rrdata "2 1 1
373 B111DD8A1C2091A89BD4FD60C57F0716CCE50FEEFF8137CDBEE0326E 02CF362B" \
374 -dane_tlsa_rrdata "2 1 1
375 60B87575447DCBA2A36B7D11AC09FB24A9DB406FEE12D2CC90180517 616E8A18"
378 Verified peername: smtp.example.com
379 DANE TLSA 2 1 1 ...ee12d2cc90180517616e8a18 matched TA certificate at depth 1
382 =item B<-dane_ee_no_namechecks>
384 This disables server name checks when authenticating via DANE-EE(3) TLSA
386 For some applications, primarily web browsers, it is not safe to disable name
387 checks due to "unknown key share" attacks, in which a malicious server can
388 convince a client that a connection to a victim server is instead a secure
389 connection to the malicious server.
390 The malicious server may then be able to violate cross-origin scripting
392 Thus, despite the text of RFC7671, name checks are by default enabled for
393 DANE-EE(3) TLSA records, and can be disabled in applications where it is safe
395 In particular, SMTP and XMPP clients should set this option as SRV and MX
396 records already make it possible for a remote domain to redirect client
397 connections to any server of its choice, and in any case SMTP and XMPP clients
398 do not execute scripts downloaded from remote servers.
400 =item B<-attime>, B<-check_ss_sig>, B<-crl_check>, B<-crl_check_all>,
401 B<-explicit_policy>, B<-extended_crl>, B<-ignore_critical>, B<-inhibit_any>,
402 B<-inhibit_map>, B<-no_alt_chains>, B<-no_check_time>, B<-partial_chain>, B<-policy>,
403 B<-policy_check>, B<-policy_print>, B<-purpose>, B<-suiteB_128>,
404 B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>, B<-use_deltas>,
405 B<-auth_level>, B<-verify_depth>, B<-verify_email>, B<-verify_hostname>,
406 B<-verify_ip>, B<-verify_name>, B<-x509_strict>
408 Set various certificate chain validation options. See the
409 L<verify(1)> manual page for details.
413 Reconnects to the same server 5 times using the same session ID, this can
414 be used as a test that session caching is working.
418 Displays the server certificate list as sent by the server: it only consists of
419 certificates the server has sent (in the order the server has sent them). It is
420 B<not> a verified chain.
424 Print session information when the program exits. This will always attempt
425 to print out information even if the connection fails. Normally information
426 will only be printed out once if the connection succeeds. This option is useful
427 because the cipher in use may be renegotiated or the connection may fail
428 because a client certificate is required or is requested only after an
429 attempt is made to access a certain URL. Note: the output produced by this
430 option is not always accurate because a connection might never have been
435 Prints out the SSL session states.
439 Print extensive debugging information including a hex dump of all traffic.
443 Show all protocol messages with hex dump.
447 Show verbose trace output of protocol messages. OpenSSL needs to be compiled
448 with B<enable-ssl-trace> for this option to work.
452 File to send output of B<-msg> or B<-trace> to, default standard output.
456 Tests non-blocking I/O
460 Turns on non-blocking I/O
464 This option translated a line feed from the terminal into CR+LF as required
469 Inhibit shutting down the connection when end of file is reached in the
474 Inhibit printing of session and certificate information. This implicitly
475 turns on B<-ign_eof> as well.
479 Shut down the connection when end of file is reached in the input.
480 Can be used to override the implicit B<-ign_eof> after B<-quiet>.
482 =item B<-psk_identity> I<identity>
484 Use the PSK identity I<identity> when using a PSK cipher suite.
485 The default value is "Client_identity" (without the quotes).
489 Use the PSK key I<key> when using a PSK cipher suite. The key is
490 given as a hexadecimal number without leading 0x, for example -psk
492 This option must be provided in order to use a PSK cipher.
494 =item B<-psk_session> I<file>
496 Use the pem encoded SSL_SESSION data stored in I<file> as the basis of a PSK.
497 Note that this will only work if TLSv1.3 is negotiated.
499 =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>
501 These options require or disable the use of the specified SSL or TLS protocols.
502 By default, this command will negotiate the highest mutually supported protocol
504 When a specific TLS version is required, only that version will be offered to
505 and accepted from the server.
506 Note that not all protocols and flags may be available, depending on how
509 =item B<-dtls>, B<-dtls1>, B<-dtls1_2>
511 These options make this command use DTLS protocols instead of TLS.
512 With B<-dtls>, it will negotiate any supported DTLS protocol version,
513 whilst B<-dtls1> and B<-dtls1_2> will only support DTLS1.0 and DTLS1.2
518 Use SCTP for the transport protocol instead of UDP in DTLS. Must be used in
519 conjunction with B<-dtls>, B<-dtls1> or B<-dtls1_2>. This option is only
520 available where OpenSSL has support for SCTP enabled.
522 =item B<-sctp_label_bug>
524 Use the incorrect behaviour of older OpenSSL implementations when computing
525 endpoint-pair shared secrets for DTLS/SCTP. This allows communication with
526 older broken implementations but breaks interoperability with correct
527 implementations. Must be used in conjunction with B<-sctp>. This option is only
528 available where OpenSSL has support for SCTP enabled.
530 =item B<-fallback_scsv>
532 Send TLS_FALLBACK_SCSV in the ClientHello.
536 Switch on asynchronous mode. Cryptographic operations will be performed
537 asynchronously. This will only have an effect if an asynchronous capable engine
538 is also used via the B<-engine> option. For test purposes the dummy async engine
539 (dasync) can be used (if available).
541 =item B<-max_send_frag> I<int>
543 The maximum size of data fragment to send.
544 See L<SSL_CTX_set_max_send_fragment(3)> for further information.
546 =item B<-split_send_frag> I<int>
548 The size used to split data for encrypt pipelines. If more data is written in
549 one go than this value then it will be split into multiple pipelines, up to the
550 maximum number of pipelines defined by max_pipelines. This only has an effect if
551 a suitable cipher suite has been negotiated, an engine that supports pipelining
552 has been loaded, and max_pipelines is greater than 1. See
553 L<SSL_CTX_set_split_send_fragment(3)> for further information.
555 =item B<-max_pipelines> I<int>
557 The maximum number of encrypt/decrypt pipelines to be used. This will only have
558 an effect if an engine has been loaded that supports pipelining (e.g. the dasync
559 engine) and a suitable cipher suite has been negotiated. The default value is 1.
560 See L<SSL_CTX_set_max_pipelines(3)> for further information.
562 =item B<-read_buf> I<int>
564 The default read buffer size to be used for connections. This will only have an
565 effect if the buffer size is larger than the size that would otherwise be used
566 and pipelining is in use (see L<SSL_CTX_set_default_read_buffer_len(3)> for
567 further information).
571 There are several known bugs in SSL and TLS implementations. Adding this
572 option enables various workarounds.
576 Enables support for SSL/TLS compression.
577 This option was introduced in OpenSSL 1.1.0.
578 TLS compression is not recommended and is off by default as of
583 Disables support for SSL/TLS compression.
584 TLS compression is not recommended and is off by default as of
589 Only provide a brief summary of connection parameters instead of the
590 normal verbose output.
592 =item B<-sigalgs> I<sigalglist>
594 Specifies the list of signature algorithms that are sent by the client.
595 The server selects one entry in the list based on its preferences.
596 For example strings, see L<SSL_CTX_set1_sigalgs(3)>
598 =item B<-curves> I<curvelist>
600 Specifies the list of supported curves to be sent by the client. The curve is
601 ultimately selected by the server. For a list of all curves, use:
603 $ openssl ecparam -list_curves
605 =item B<-cipher> I<cipherlist>
607 This allows the TLSv1.2 and below cipher list sent by the client to be modified.
608 This list will be combined with any TLSv1.3 ciphersuites that have been
609 configured. Although the server determines which ciphersuite is used it should
610 take the first supported cipher in the list sent by the client. See
611 L<openssl-ciphers(1)> for more information.
613 =item B<-ciphersuites> I<val>
615 This allows the TLSv1.3 ciphersuites sent by the client to be modified. This
616 list will be combined with any TLSv1.2 and below ciphersuites that have been
617 configured. Although the server determines which cipher suite is used it should
618 take the first supported cipher in the list sent by the client. See
619 L<openssl-ciphers(1)> for more information. The format for this list is a simple
620 colon (":") separated list of TLSv1.3 ciphersuite names.
622 =item B<-starttls> I<protocol>
624 Send the protocol-specific message(s) to switch to TLS for communication.
625 I<protocol> is a keyword for the intended protocol. Currently, the only
626 supported keywords are "smtp", "pop3", "imap", "ftp", "xmpp", "xmpp-server",
627 "irc", "postgres", "mysql", "lmtp", "nntp", "sieve" and "ldap".
629 =item B<-xmpphost> I<hostname>
631 This option, when used with "-starttls xmpp" or "-starttls xmpp-server",
632 specifies the host for the "to" attribute of the stream element.
633 If this option is not specified, then the host specified with "-connect"
636 This option is an alias of the B<-name> option for "xmpp" and "xmpp-server".
638 =item B<-name> I<hostname>
640 This option is used to specify hostname information for various protocols
641 used with B<-starttls> option. Currently only "xmpp", "xmpp-server",
642 "smtp" and "lmtp" can utilize this B<-name> option.
644 If this option is used with "-starttls xmpp" or "-starttls xmpp-server",
645 if specifies the host for the "to" attribute of the stream element. If this
646 option is not specified, then the host specified with "-connect" will be used.
648 If this option is used with "-starttls lmtp" or "-starttls smtp", it specifies
649 the name to use in the "LMTP LHLO" or "SMTP EHLO" message, respectively. If
650 this option is not specified, then "mail.example.com" will be used.
652 =item B<-tlsextdebug>
654 Print out a hex dump of any TLS extensions received from the server.
658 Disable RFC4507bis session ticket support.
660 =item B<-sess_out> I<filename>
662 Output SSL session to I<filename>.
664 =item B<-sess_in> I<filename>
666 Load SSL session from I<filename>. The client will attempt to resume a
667 connection from this session.
669 =item B<-engine> I<id>
671 Specifying an engine (by its unique I<id> string) will cause this command
672 to attempt to obtain a functional reference to the specified engine,
673 thus initialising it if needed. The engine will then be set as the default
674 for all available algorithms.
676 =item B<-rand> I<files>
678 The files containing random data used to seed the random number generator.
679 Multiple files can be specified separated by an OS-dependent character.
680 The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
683 =item B<-writerand> I<file>
685 Writes random data to the specified I<file> upon exit.
686 This can be used with a subsequent B<-rand> flag.
688 =item B<-serverinfo> I<types>
690 A list of comma-separated TLS Extension Types (numbers between 0 and
691 65535). Each type will be sent as an empty ClientHello TLS Extension.
692 The server's response (if any) will be encoded and displayed as a PEM
697 Sends a certificate status request to the server (OCSP stapling). The server
698 response (if any) is printed out.
700 =item B<-alpn> I<protocols>, B<-nextprotoneg> I<protocols>
702 These flags enable the Enable the Application-Layer Protocol Negotiation
703 or Next Protocol Negotiation (NPN) extension, respectively. ALPN is the
704 IETF standard and replaces NPN.
705 The I<protocols> list is a comma-separated list of protocol names that
706 the client should advertise support for. The list should contain the most
707 desirable protocols first. Protocol names are printable ASCII strings,
708 for example "http/1.1" or "spdy/3".
709 An empty list of protocols is treated specially and will cause the
710 client to advertise support for the TLS extension but disconnect just
711 after receiving ServerHello with a list of server supported protocols.
712 The flag B<-nextprotoneg> cannot be specified if B<-tls1_3> is used.
714 =item B<-ct>, B<-noct>
716 Use one of these two options to control whether Certificate Transparency (CT)
717 is enabled (B<-ct>) or disabled (B<-noct>).
718 If CT is enabled, signed certificate timestamps (SCTs) will be requested from
719 the server and reported at handshake completion.
721 Enabling CT also enables OCSP stapling, as this is one possible delivery method
726 A file containing a list of known Certificate Transparency logs. See
727 L<SSL_CTX_set_ctlog_list_file(3)> for the expected file format.
729 =item B<-keylogfile> I<file>
731 Appends TLS secrets to the specified keylog file such that external programs
732 (like Wireshark) can decrypt TLS connections.
734 =item B<-early_data> I<file>
736 Reads the contents of the specified file and attempts to send it as early data
737 to the server. This will only work with resumed sessions that support early
738 data and when the server accepts the early data.
742 For TLSv1.3 only, send the Post-Handshake Authentication extension. This will
743 happen whether or not a certificate has been provided via B<-cert>.
745 =item I<host>:I<port>
747 Rather than providing B<-connect>, the target hostname and optional port may
748 be provided as a single positional argument after all options. If neither this
749 nor B<-connect> are provided, falls back to attempting to connect to
750 I<localhost> on port I<4433>.
754 =head1 CONNECTED COMMANDS
756 If a connection is established with an SSL server then any data received
757 from the server is displayed and any key presses will be sent to the
758 server. If end of file is reached then the connection will be closed down. When
759 used interactively (which means neither B<-quiet> nor B<-ign_eof> have been
760 given), then certain commands are also recognized which perform special
761 operations. These commands are a letter which must appear at the start of a
762 line. They are listed below.
768 End the current SSL connection and exit.
772 Renegotiate the SSL session (TLSv1.2 and below only).
776 Send a key update message to the server (TLSv1.3 only)
780 Send a key update message to the server and request one back (TLSv1.3 only)
786 This command can be used to debug SSL servers. To connect to an SSL HTTP
789 openssl s_client -connect servername:443
791 would typically be used (https uses port 443). If the connection succeeds
792 then an HTTP command can be given such as "GET /" to retrieve a web page.
794 If the handshake fails then there are several possible causes, if it is
795 nothing obvious like no client certificate then the B<-bugs>,
796 B<-ssl3>, B<-tls1>, B<-no_ssl3>, B<-no_tls1> options can be tried
797 in case it is a buggy server. In particular you should play with these
798 options B<before> submitting a bug report to an OpenSSL mailing list.
800 A frequent problem when attempting to get client certificates working
801 is that a web client complains it has no certificates or gives an empty
802 list to choose from. This is normally because the server is not sending
803 the clients certificate authority in its "acceptable CA list" when it
804 requests a certificate. By using this command, the CA list can be viewed
805 and checked. However some servers only request client authentication
806 after a specific URL is requested. To obtain the list in this case it
807 is necessary to use the B<-prexit> option and send an HTTP request
808 for an appropriate page.
810 If a certificate is specified on the command line using the B<-cert>
811 option it will not be used unless the server specifically requests
812 a client certificate. Therefor merely including a client certificate
813 on the command line is no guarantee that the certificate works.
815 If there are problems verifying a server certificate then the
816 B<-showcerts> option can be used to show all the certificates sent by the
819 This command is a test tool and is designed to continue the
820 handshake after any certificate verification errors. As a result it will
821 accept any certificate chain (trusted or not) sent by the peer. None test
822 applications should B<not> do this as it makes them vulnerable to a MITM
823 attack. This behaviour can be changed by with the B<-verify_return_error>
824 option: any verify errors are then returned aborting the handshake.
826 The B<-bind> option may be useful if the server or a firewall requires
827 connections to come from some particular address and or port.
831 Because this program has a lot of options and also because some of the
832 techniques used are rather old, the C source for this command is rather
833 hard to read and not a model of how things should be done.
834 A typical SSL client program would be much simpler.
836 The B<-prexit> option is a bit of a hack. We should really report
837 information whenever a session is renegotiated.
842 L<openssl-sess_id(1)>,
843 L<openssl-s_server(1)>,
844 L<openssl-ciphers(1)>,
846 L<SSL_CTX_set_max_send_fragment(3)>,
847 L<SSL_CTX_set_split_send_fragment(3)>,
848 L<SSL_CTX_set_max_pipelines(3)>
852 The B<-no_alt_chains> option was added in OpenSSL 1.1.0.
853 The B<-name> option was added in OpenSSL 1.1.1.
857 Copyright 2000-2019 The OpenSSL Project Authors. All Rights Reserved.
859 Licensed under the Apache License 2.0 (the "License"). You may not use
860 this file except in compliance with the License. You can obtain a copy
861 in the file LICENSE in the source distribution or at
862 L<https://www.openssl.org/source/license.html>.