path: root/doc/man1/openssl-s_client.pod.in

=pod
{- OpenSSL::safe::output_do_not_edit_headers(); -}

=head1 NAME

openssl-s_client - SSL/TLS client program

=head1 SYNOPSIS

B<openssl> B<s_client>
[B<-help>]
[B<-ssl_config> I<section>]
[B<-connect> I<host:port>]
[B<-host> I<hostname>]
[B<-port> I<port>]
[B<-bind> I<host:port>]
[B<-proxy> I<host:port>]
[B<-proxy_user> I<userid>]
[B<-proxy_pass> I<arg>]
[B<-unix> I<path>]
[B<-4>]
[B<-6>]
[B<-quic>]
[B<-servername> I<name>]
[B<-noservername>]
[B<-verify> I<depth>]
[B<-verify_return_error>]
[B<-verify_quiet>]
[B<-verifyCAfile> I<filename>]
[B<-verifyCApath> I<dir>]
[B<-verifyCAstore> I<uri>]
[B<-cert> I<filename>]
[B<-certform> B<DER>|B<PEM>|B<P12>]
[B<-cert_chain> I<filename>]
[B<-build_chain>]
[B<-CRL> I<filename>]
[B<-CRLform> B<DER>|B<PEM>]
[B<-crl_download>]
[B<-key> I<filename>|I<uri>]
[B<-keyform> B<DER>|B<PEM>|B<P12>|B<ENGINE>]
[B<-pass> I<arg>]
[B<-chainCAfile> I<filename>]
[B<-chainCApath> I<directory>]
[B<-chainCAstore> I<uri>]
[B<-requestCAfile> I<filename>]
[B<-dane_tlsa_domain> I<domain>]
[B<-dane_tlsa_rrdata> I<rrdata>]
[B<-dane_ee_no_namechecks>]
[B<-reconnect>]
[B<-showcerts>]
[B<-prexit>]
[B<-no-interactive>]
[B<-debug>]
[B<-trace>]
[B<-nocommands>]
[B<-adv>]
[B<-security_debug>]
[B<-security_debug_verbose>]
[B<-msg>]
[B<-timeout>]
[B<-mtu> I<size>]
[B<-no_etm>]
[B<-no_ems>]
[B<-keymatexport> I<label>]
[B<-keymatexportlen> I<len>]
[B<-msgfile> I<filename>]
[B<-nbio_test>]
[B<-state>]
[B<-nbio>]
[B<-crlf>]
[B<-ign_eof>]
[B<-no_ign_eof>]
[B<-psk_identity> I<identity>]
[B<-psk> I<key>]
[B<-psk_session> I<file>]
[B<-quiet>]
[B<-sctp>]
[B<-sctp_label_bug>]
[B<-fallback_scsv>]
[B<-async>]
[B<-maxfraglen> I<len>]
[B<-max_send_frag>]
[B<-split_send_frag>]
[B<-max_pipelines>]
[B<-read_buf>]
[B<-ignore_unexpected_eof>]
[B<-bugs>]
[B<-no_tx_cert_comp>]
[B<-no_rx_cert_comp>]
[B<-comp>]
[B<-no_comp>]
[B<-brief>]
[B<-legacy_server_connect>]
[B<-no_legacy_server_connect>]
[B<-allow_no_dhe_kex>]
[B<-prefer_no_dhe_kex>]
[B<-sigalgs> I<sigalglist>]
[B<-curves> I<curvelist>]
[B<-cipher> I<cipherlist>]
[B<-ciphersuites> I<val>]
[B<-serverpref>]
[B<-starttls> I<protocol>]
[B<-name> I<hostname>]
[B<-xmpphost> I<hostname>]
[B<-name> I<hostname>]
[B<-tlsextdebug>]
[B<-no_ticket>]
[B<-sess_out> I<filename>]
[B<-serverinfo> I<types>]
[B<-sess_in> I<filename>]
[B<-serverinfo> I<types>]
[B<-status>]
[B<-alpn> I<protocols>]
[B<-nextprotoneg> I<protocols>]
[B<-ct>]
[B<-noct>]
[B<-ctlogfile>]
[B<-keylogfile> I<file>]
[B<-early_data> I<file>]
[B<-enable_pha>]
[B<-use_srtp> I<value>]
[B<-srpuser> I<value>]
[B<-srppass> I<value>]
[B<-srp_lateuser>]
[B<-srp_moregroups>]
[B<-srp_strength> I<number>]
[B<-ktls>]
[B<-tfo>]
{- $OpenSSL::safe::opt_name_synopsis -}
{- $OpenSSL::safe::opt_version_synopsis -}
{- $OpenSSL::safe::opt_x_synopsis -}
{- $OpenSSL::safe::opt_trust_synopsis -}
{- $OpenSSL::safe::opt_s_synopsis -}
{- $OpenSSL::safe::opt_r_synopsis -}
{- $OpenSSL::safe::opt_provider_synopsis -}
{- $OpenSSL::safe::opt_engine_synopsis -}[B<-ssl_client_engine> I<id>]
{- $OpenSSL::safe::opt_v_synopsis -}
[B<-enable_server_rpk>]
[B<-enable_client_rpk>]
[I<host>:I<port>]

=head1 DESCRIPTION

This command implements a generic SSL/TLS client which
connects to a remote host using SSL/TLS. It is a I<very> useful diagnostic
tool for SSL servers.

=head1 OPTIONS

In addition to the options below, this command also supports the
common and client only options documented
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<-ssl_config> I<section>

Use the specified section of the configuration file to configure the B<SSL_CTX> object.

=item B<-connect> I<host>:I<port>

This specifies the host and optional port to connect to. It is possible to
select the host and port using the optional target positional argument instead.
If neither this nor the target positional argument are specified then an attempt
is made to connect to the local host on port 4433.

=item B<-host> I<hostname>

Host to connect to; use B<-connect> instead.

=item B<-port> I<port>

Connect to the specified port; use B<-connect> instead.

=item B<-bind> I<host:port>

This specifies the host address and or port to bind as the source for the
connection.  For Unix-domain sockets the port is ignored and the host is
used as the source socket address.

=item B<-proxy> I<host:port>

When used with the B<-connect> flag, the program uses the host and port
specified with this flag and issues an HTTP CONNECT command to connect
to the desired server.

=item B<-proxy_user> I<userid>

When used with the B<-proxy> flag, the program will attempt to authenticate
with the specified proxy using basic (base64) authentication.
NB: Basic authentication is insecure; the credentials are sent to the proxy
in easily reversible base64 encoding before any TLS/SSL session is established.
Therefore, these credentials are easily recovered by anyone able to sniff/trace
the network. Use with caution.

=item B<-proxy_pass> I<arg>

The proxy password source, used with the B<-proxy_user> flag.
For more information about the format of B<arg>
see L<openssl-passphrase-options(1)>.

=item B<-unix> I<path>

Connect over the specified Unix-domain socket.

=item B<-4>

Use IPv4 only.

=item B<-6>

Use IPv6 only.

=item B<-quic>

Connect using the QUIC protocol. If specified then the B<-alpn> option must also
be provided.

=item B<-servername> I<name>

Set the TLS SNI (Server Name Indication) extension in the ClientHello message to
the given value.
If B<-servername> is not provided, the TLS SNI extension will be populated with
the name given to B<-connect> if it follows a DNS name format. If B<-connect> is
not provided either, the SNI is set to "localhost".
This is the default since OpenSSL 1.1.1.

Even though SNI should normally be a DNS name and not an IP address, if
B<-servername> is provided then that name will be sent, regardless of whether
it is a DNS name or not.

This option cannot be used in conjunction with B<-noservername>.

=item B<-noservername>

Suppresses sending of the SNI (Server Name Indication) extension in the
ClientHello message. Cannot be used in conjunction with the B<-servername> or
B<-dane_tlsa_domain> options.

=item B<-cert> I<filename>

The client certificate to use, if one is requested by the server.
The default is not to use a certificate.

The chain for the client certificate may be specified using B<-cert_chain>.

=item B<-certform> B<DER>|B<PEM>|B<P12>

The client certificate file format to use; unspecified by default.
See L<openssl-format-options(1)> for details.

=item B<-cert_chain>

A file or URI of untrusted certificates to use when attempting to build the
certificate chain related to the certificate specified via the B<-cert> option.
The input can be in PEM, DER, or PKCS#12 format.

=item B<-build_chain>

Specify whether the application should build the client certificate chain to be
provided to the server.

=item B<-CRL> I<filename>

CRL file to use to check the server's certificate.

=item B<-CRLform> B<DER>|B<PEM>

The CRL file format; unspecified by default.
See L<openssl-format-options(1)> for details.

=item B<-crl_download>

Download CRL from distribution points in the certificate.

=item B<-key> I<filename>|I<uri>

The client private key to use.
If not specified then the certificate file will be used to read also the key.

=item B<-keyform> B<DER>|B<PEM>|B<P12>|B<ENGINE>

The key format; unspecified by default.
See L<openssl-format-options(1)> for details.

=item B<-pass> I<arg>

the private key and certificate file password source.
For more information about the format of I<arg>
see L<openssl-passphrase-options(1)>.

=item B<-verify> I<depth>

The verify depth to use. This specifies the maximum length of the
server certificate chain and turns on server certificate verification.
Currently the verify operation continues after errors so all the problems
with a certificate chain can be seen. As a side effect the connection
will never fail due to a server certificate verify failure.

=item B<-verify_return_error>

Return verification errors instead of continuing. This will typically
abort the handshake with a fatal error.

=item B<-verify_quiet>

Limit verify output to only errors.

=item B<-verifyCAfile> I<filename>

A file in PEM format containing trusted certificates to use
for verifying the server's certificate.

=item B<-verifyCApath> I<dir>

A directory containing trusted certificates to use
for verifying the server's certificate.
This directory must be in "hash format",
see L<openssl-verify(1)> for more information.

=item B<-verifyCAstore> I<uri>

The URI of a store containing trusted certificates to use
for verifying the server's certificate.

=item B<-chainCAfile> I<file>

A file in PEM format containing trusted certificates to use
when attempting to build the client certificate chain.

=item B<-chainCApath> I<directory>

A directory containing trusted certificates to use
for building the client certificate chain provided to the server.
This directory must be in "hash format",
see L<openssl-verify(1)> for more information.

=item B<-chainCAstore> I<uri>

The URI of a store containing trusted certificates to use
when attempting to build the client certificate chain.
The URI may indicate a single certificate, as well as a collection of them.
With URIs in the C<file:> scheme, this acts as B<-chainCAfile> or
B<-chainCApath>, depending on if the URI indicates a directory or a
single file.
See L<ossl_store-file(7)> for more information on the C<file:> scheme.

=item B<-requestCAfile> I<file>

A file containing a list of certificates whose subject names will be sent
to the server in the B<certificate_authorities> extension. Only supported
for TLS 1.3

=item B<-dane_tlsa_domain> I<domain>

Enable RFC6698/RFC7671 DANE TLSA authentication and specify the
TLSA base domain which becomes the default SNI hint and the primary
reference identifier for hostname checks.  This must be used in
combination with at least one instance of the B<-dane_tlsa_rrdata>
option below.

When DANE authentication succeeds, the diagnostic output will include
the lowest (closest to 0) depth at which a TLSA record authenticated
a chain certificate.  When that TLSA record is a "2 1 0" trust
anchor public key that signed (rather than matched) the top-most
certificate of the chain, the result is reported as "TA public key
verified".  Otherwise, either the TLSA record "matched TA certificate"
at a positive depth or else "matched EE certificate" at depth 0.

=item B<-dane_tlsa_rrdata> I<rrdata>

Use one or more times to specify the RRDATA fields of the DANE TLSA
RRset associated with the target service.  The I<rrdata> value is
specified in "presentation form", that is four whitespace separated
fields that specify the usage, selector, matching type and associated
data, with the last of these encoded in hexadecimal.  Optional
whitespace is ignored in the associated data field.  For example:

  $ 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"
  ...
  Verification: OK
  Verified peername: smtp.example.com
  DANE TLSA 2 1 1 ...ee12d2cc90180517616e8a18 matched TA certificate at depth 1
  ...

=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<-reconnect>

Reconnects to the same server 5 times using the same session ID, this can
be used as a test that session caching is working.

=item B<-showcerts>

Displays the server certificate list as sent by the server: it only consists of
certificates the server has sent (in the order the server has sent them). It is
B<not> a verified chain.

=item B<-prexit>

Print session information when the program exits. This will always attempt
to print out information even if the connection fails. Normally information
will only be printed out once if the connection succeeds. This option is useful
because the cipher in use may be renegotiated or the connection may fail
because a client certificate is required or is requested only after an
attempt is made to access a certain URL. Note: the output produced by this
option is not always accurate because a connection might never have been
established.

=item B<-no-interactive>

This flag can be used to run the client in a non-interactive mode.

=item B<-state>

Prints out the SSL session states.

=item B<-debug>

Print extensive debugging information including a hex dump of all traffic.

=item B<-nocommands>

Do not use interactive command letters.

=item B<-adv>

Use advanced command mode.

=item B<-security_debug>

Enable security debug messages.

=item B<-security_debug_verbose>

Output more security debug output.

=item B<-msg>

Show protocol messages.

=item B<-timeout>

Enable send/receive timeout on DTLS connections.

=item B<-mtu> I<size>

Set MTU of the link layer to the specified size.

=item B<-no_etm>

Disable Encrypt-then-MAC negotiation.

=item B<-no_ems>

Disable Extended master secret negotiation.

=item B<-keymatexport> I<label>

Export keying material using the specified label.

=item B<-keymatexportlen> I<len>

Export the specified number of bytes of keying material; default is 20.

Show all protocol messages with hex dump.

=item B<-trace>

Show verbose trace output of protocol messages.

=item B<-msgfile> I<filename>

File to send output of B<-msg> or B<-trace> to, default standard output.

=item B<-nbio_test>

Tests nonblocking I/O

=item B<-nbio>

Turns on nonblocking I/O

=item B<-crlf>

This option translated a line feed from the terminal into CR+LF as required
by some servers.

=item B<-ign_eof>

Inhibit shutting down the connection when end of file is reached in the
input.

=item B<-quiet>

Inhibit printing of session and certificate information.  This implicitly
turns on B<-ign_eof> as well.

=item B<-no_ign_eof>

Shut down the connection when end of file is reached in the input.
Can be used to override the implicit B<-ign_eof> after B<-quiet>.

=item B<-psk_identity> I<identity>

Use the PSK identity I<identity> when using a PSK cipher suite.
The default value is "Client_identity" (without the quotes).

=item B<-psk> I<key>

Use the PSK key I<key> when using a PSK cipher suite. The key is
given as a hexadecimal number without leading 0x, for example -psk
1a2b3c4d.
This option must be provided in order to use a PSK cipher.

=item B<-psk_session> I<file>

Use the pem encoded SSL_SESSION data stored in I<file> as the basis of a PSK.
Note that this will only work if TLSv1.3 is negotiated.

=item B<-sctp>

Use SCTP for the transport protocol instead of UDP in DTLS. Must be used in
conjunction with B<-dtls>, B<-dtls1> or B<-dtls1_2>. This option is only
available where OpenSSL has support for SCTP enabled.

=item B<-sctp_label_bug>

Use the incorrect behaviour of older OpenSSL implementations when computing
endpoint-pair shared secrets for DTLS/SCTP. This allows communication with
older broken implementations but breaks interoperability with correct
implementations. Must be used in conjunction with B<-sctp>. This option is only
available where OpenSSL has support for SCTP enabled.

=item B<-fallback_scsv>

Send TLS_FALLBACK_SCSV in the ClientHello.

=item B<-async>

Switch on asynchronous mode. Cryptographic operations will be performed
asynchronously. This will only have an effect if an asynchronous capable engine
is also used via the B<-engine> option. For test purposes the dummy async engine
(dasync) can be used (if available).

=item B<-maxfraglen> I<len>

Enable Maximum Fragment Length Negotiation; allowed values are
C<512>, C<1024>, C<2048>, and C<4096>.

=item B<-max_send_frag> I<int>

The maximum size of data fragment to send.
See L<SSL_CTX_set_max_send_fragment(3)> for further information.

=item B<-split_send_frag> I<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