-
=pod
=head1 NAME
=head1 SYNOPSIS
B<openssl> B<s_client>
+[B<-help>]
[B<-connect host:port>]
[B<-proxy host:port>]
[B<-servername name>]
[B<-no-CApath>]
[B<-dane_tlsa_domain domain>]
[B<-dane_tlsa_rrdata rrdata>]
+[B<-dane_ee_no_namechecks>]
[B<-attime timestamp>]
[B<-check_ss_sig>]
[B<-crl_check>]
[B<-ignore_critical>]
[B<-inhibit_any>]
[B<-inhibit_map>]
-[B<-issuer_checks>]
+[B<-no_check_time>]
[B<-partial_chain>]
[B<-policy arg>]
[B<-policy_check>]
[B<-trusted_first>]
[B<-no_alt_chains>]
[B<-use_deltas>]
+[B<-auth_level num>]
[B<-verify_depth num>]
[B<-verify_email email>]
[B<-verify_hostname hostname>]
[B<-quiet>]
[B<-ssl3>]
[B<-tls1>]
+[B<-tls1_1>]
+[B<-tls1_2>]
[B<-no_ssl3>]
[B<-no_tls1>]
[B<-no_tls1_1>]
[B<-no_tls1_2>]
+[B<-dtls>]
+[B<-dtls1>]
+[B<-dtls1_2>]
[B<-fallback_scsv>]
[B<-async>]
+[B<-split_send_frag>]
+[B<-max_pipelines>]
+[B<-read_buf>]
[B<-bugs>]
[B<-comp>]
[B<-no_comp>]
[B<-rand file(s)>]
[B<-serverinfo types>]
[B<-status>]
+[B<-alpn protocols>]
[B<-nextprotoneg protocols>]
+[B<-ct|noct>]
+[B<-ctlogfile>]
=head1 DESCRIPTION
In addition to the options below the B<s_client> utility also supports the
common and client only options documented in the
-in the L<SSL_CONF_cmd(3)|SSL_CONF_cmd(3)/SUPPORTED COMMAND LINE COMMANDS>
+in the "Supported Command Line Commands" section of the L<SSL_CONF_cmd(3)>
manual page.
=over 4
+=item B<-help>
+
+Print out a usage message.
+
=item B<-connect host:port>
This specifies the host and optional port to connect to. If not specified
data, with the last of these encoded in hexadecimal. Optional
whitespace is ignored in the associated data field. For example:
- $ openssl s_client -starttls smtp -connect smtp.example.com:25 \
+ $ openssl s_client -brief -starttls smtp \
+ -connect smtp.example.com:25 \
-dane_tlsa_domain smtp.example.com \
-dane_tlsa_rrdata "2 1 1
B111DD8A1C2091A89BD4FD60C57F0716CCE50FEEFF8137CDBEE0326E 02CF362B" \
-dane_tlsa_rrdata "2 1 1
60B87575447DCBA2A36B7D11AC09FB24A9DB406FEE12D2CC90180517 616E8A18"
- CONNECTED(00000003)
...
- DANE TLSA 2 1 1 matched TA certificate at depth 1
+ Verification: OK
Verified peername: smtp.example.com
+ DANE TLSA 2 1 1 ...ee12d2cc90180517616e8a18 matched TA certificate at depth 1
...
- Verify return code: 0 (ok)
- ...
+
+=item B<-dane_ee_no_namechecks>
+
+This disables server name checks when authenticating via DANE-EE(3) TLSA
+records.
+For some applications, primarily web browsers, it is not safe to disable name
+checks due to "unknown key share" attacks, in which a malicious server can
+convince a client that a connection to a victim server is instead a secure
+connection to the malicious server.
+The malicious server may then be able to violate cross-origin scripting
+restrictions.
+Thus, despite the text of RFC7671, name checks are by default enabled for
+DANE-EE(3) TLSA records, and can be disabled in applications where it is safe
+to do so.
+In particular, SMTP and XMPP clients should set this option as SRV and MX
+records already make it possible for a remote domain to redirect client
+connections to any server of its choice, and in any case SMTP and XMPP clients
+do not execute scripts downloaded from remote servers.
=item B<-attime>, B<-check_ss_sig>, B<-crl_check>, B<-crl_check_all>,
-B<explicit_policy>, B<-extended_crl>, B<-ignore_critical>, B<-inhibit_any>,
-B<-inhibit_map>, B<-issuer_checks>, B<-partial_chain>, B<-policy>,
+B<-explicit_policy>, B<-extended_crl>, B<-ignore_critical>, B<-inhibit_any>,
+B<-inhibit_map>, B<-no_alt_chains>, B<-no_check_time>, B<-partial_chain>, B<-policy>,
B<-policy_check>, B<-policy_print>, B<-purpose>, B<-suiteB_128>,
-B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>, B<-no_alt_chains>,
-B<-use_deltas>, B<-verify_depth>, B<-verify_email>, B<-verify_hostname>,
+B<-suiteB_128_only>, B<-suiteB_192>, B<-trusted_first>, B<-use_deltas>,
+B<-auth_level>, B<-verify_depth>, B<-verify_email>, B<-verify_hostname>,
B<-verify_ip>, B<-verify_name>, B<-x509_strict>
Set various certificate chain validation options. See the
given as a hexadecimal number without leading 0x, for example -psk
1a2b3c4d.
-=item B<-ssl3>, B<-tls1>, B<-no_ssl3>, B<-no_tls1>, B<-no_tls1_1>, B<-no_tls1_2>
+=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>
-these options disable the use of certain SSL or TLS protocols. By default
-the initial handshake uses a method which should be compatible with all
-servers and permit them to use SSL v3 or TLS as appropriate.
+These options require or disable the use of the specified SSL or TLS protocols.
+By default B<s_client> will negotiate the highest mutually supported protocol
+version.
+When a specific TLS version is required, only that version will be offered to
+and accepted from the server.
-Unfortunately there are still ancient and broken servers in use which
-cannot handle this technique and will fail to connect. Some servers only
-work if TLS is turned off.
+=item B<-dtls>, B<-dtls1>, B<-dtls1_2>
+
+These options make B<s_client> use DTLS protocols instead of TLS.
+With B<-dtls>, B<s_client> will negotiate any supported DTLS protocol version,
+whilst B<-dtls1> and B<-dtls1_2> will only support DTLS1.0 and DTLS1.2
+respectively.
=item B<-fallback_scsv>
is also used via the B<-engine> option. For test purposes the dummy async engine
(dasync) can be used (if available).
+=item B<-split_send_frag int>
+
+The size used to split data for encrypt pipelines. If more data is written in
+one go than this value then it will be split into multiple pipelines, up to the
+maximum number of pipelines defined by max_pipelines. This only has an effect if
+a suitable ciphersuite has been negotiated, an engine that supports pipelining
+has been loaded, and max_pipelines is greater than 1. See
+L<SSL_CTX_set_split_send_fragment(3)> for further information.
+
+=item B<-max_pipelines int>
+
+The maximum number of encrypt/decrypt pipelines to be used. This will only have
+an effect if an engine has been loaded that supports pipelining (e.g. the dasync
+engine) and a suitable ciphersuite has been negotiated. The default value is 1.
+See L<SSL_CTX_set_max_pipelines(3)> for further information.
+
+=item B<-read_buf int>
+
+The default read buffer size to be used for connections. This will only have an
+effect if the buffer size is larger than the size that would otherwise be used
+and pipelining is in use (see L<SSL_CTX_set_default_read_buffer_len(3)> for
+further information).
+
=item B<-bugs>
there are several known bug in SSL and TLS implementations. Adding this
=item B<-no_ticket>
-disable RFC4507bis session ticket support.
+disable RFC4507bis session ticket support.
=item B<-sess_out filename>
a file or files containing random data used to seed the random number
generator, or an EGD socket (see L<RAND_egd(3)>).
-Multiple files can be specified separated by a OS-dependent character.
+Multiple files can be specified separated by an OS-dependent character.
The separator is B<;> for MS-Windows, B<,> for OpenVMS, and B<:> for
all others.
=item B<-serverinfo types>
-a list of comma-separated TLS Extension Types (numbers between 0 and
+a list of comma-separated TLS Extension Types (numbers between 0 and
65535). Each type will be sent as an empty ClientHello TLS Extension.
The server's response (if any) will be encoded and displayed as a PEM
file.
sends a certificate status request to the server (OCSP stapling). The server
response (if any) is printed out.
-=item B<-nextprotoneg protocols>
+=item B<-alpn protocols>, B<-nextprotoneg protocols>
-enable Next Protocol Negotiation TLS extension and provide a list of
+these flags enable the
+Enable the Application-Layer Protocol Negotiation or Next Protocol
+Negotiation extension, respectively. ALPN is the IETF standard and
+replaces NPN.
+The B<protocols> list is a
comma-separated protocol names that the client should advertise
support for. The list should contain most wanted protocols first.
Protocol names are printable ASCII strings, for example "http/1.1" or
advertise support for the TLS extension but disconnect just after
receiving ServerHello with a list of server supported protocols.
+=item B<-ct|noct>
+
+Use one of these two options to control whether Certificate Transparency (CT)
+is enabled (B<-ct>) or disabled (B<-noct>).
+If CT is enabled, signed certificate timestamps (SCTs) will be requested from
+the server and reported at handshake completion.
+
+Enabling CT also enables OCSP stapling, as this is one possible delivery method
+for SCTs.
+
+=item B<-ctlogfile>
+
+A file containing a list of known Certificate Transparency logs. See
+L<SSL_CTX_set_ctlog_list_file(3)> for the expected file format.
+
=back
=head1 CONNECTED COMMANDS
=head1 BUGS
-Because this program has a lot of options and also because some of
-the techniques used are rather old, the C source of s_client is rather
-hard to read and not a model of how things should be done. A typical
-SSL client program would be much simpler.
+Because this program has a lot of options and also because some of the
+techniques used are rather old, the C source of B<s_client> is rather hard to
+read and not a model of how things should be done.
+A typical SSL client program would be much simpler.
The B<-prexit> option is a bit of a hack. We should really report
information whenever a session is renegotiated.
=head1 SEE ALSO
+L<SSL_CONF_cmd(3)>,
L<sess_id(1)>, L<s_server(1)>, L<ciphers(1)>
=head1 HISTORY
The -no_alt_chains options was first added to OpenSSL 1.1.0.
+=head1 COPYRIGHT
+
+Copyright 2000-2016 The OpenSSL Project Authors. All Rights Reserved.
+
+Licensed under the OpenSSL license (the "License"). You may not use
+this file except in compliance with the License. You can obtain a copy
+in the file LICENSE in the source distribution or at
+L<https://www.openssl.org/source/license.html>.
+
=cut