openssl-s_client - SSL/TLS client program
openssl s_client [-help] [-ssl_config
section] [-connect host:port] [-host
hostname] [-port port] [-bind host:port]
[-proxy host:port] [-proxy_user userid]
[-proxy_pass arg] [-unix path] [-4]
[-6] [-servername name] [-noservername]
[-verify depth] [-verify_return_error]
[-verify_quiet] [-verifyCAfile filename]
[-verifyCApath dir] [-verifyCAstore uri]
[-cert filename] [-certform
DER|PEM|P12] [-cert_chain filename]
[-build_chain] [-CRL filename] [-CRLform
DER|PEM] [-crl_download] [-key
DER|PEM|P12|ENGINE] [-pass arg]
[-chainCAfile filename] [-chainCApath directory]
[-chainCAstore uri] [-requestCAfile filename]
[-dane_tlsa_domain domain] [-dane_tlsa_rrdata
rrdata] [-dane_ee_no_namechecks] [-reconnect]
[-showcerts] [-prexit] [-debug] [-trace]
[-nocommands] [-security_debug] [-security_debug_verbose]
[-msg] [-timeout] [-mtu size] [-no_etm]
[-keymatexport label] [-keymatexportlen len]
[-msgfile filename] [-nbio_test] [-state]
[-nbio] [-crlf] [-ign_eof] [-no_ign_eof]
[-psk_identity identity] [-psk key]
[-psk_session file] [-quiet] [-sctp]
[-sctp_label_bug] [-fallback_scsv] [-async]
[-maxfraglen len] [-max_send_frag]
[-split_send_frag] [-max_pipelines] [-read_buf]
[-ignore_unexpected_eof] [-bugs] [-comp]
[-no_comp] [-brief] [-legacy_server_connect]
[-allow_no_dhe_kex] [-sigalgs sigalglist] [-curves
curvelist] [-cipher cipherlist] [-ciphersuites
val] [-serverpref] [-starttls protocol]
[-name hostname] [-xmpphost hostname]
[-name hostname] [-tlsextdebug] [-no_ticket]
[-sess_out filename] [-serverinfo types]
[-sess_in filename] [-serverinfo types]
[-status] [-alpn protocols] [-nextprotoneg
protocols] [-ct] [-noct] [-ctlogfile]
[-keylogfile file] [-early_data file]
[-enable_pha] [-use_srtp value] [-srpuser
value] [-srppass value] [-srp_lateuser]
[-srp_moregroups] [-srp_strength number] [-nameopt
option] [-no_ssl3] [-no_tls1] [-no_tls1_1]
[-no_tls1_2] [-no_tls1_3] [-ssl3] [-tls1]
[-tls1_1] [-tls1_2] [-tls1_3] [-dtls]
[-dtls1] [-dtls1_2] [-xkey infile] [-xcert
file] [-xchain file] [-xchain_build file]
[-xcertform DER|PEM]> [-xkeyform
DER|PEM]> [-CAfile file] [-no-CAfile]
[-CApath dir] [-no-CApath] [-CAstore uri]
[-no-CAstore] [-bugs] [-no_comp] [-comp]
[-no_ticket] [-serverpref] [-client_renegotiation]
[-no_legacy_server_connect] [-no_etm] [-allow_no_dhe_kex]
[-prioritize_chacha] [-strict] [-sigalgs algs]
[-client_sigalgs algs] [-groups groups]
[-curves curves] [-named_curve curve]
[-cipher ciphers] [-ciphersuites 1.3ciphers]
[-min_protocol minprot] [-max_protocol maxprot]
[-record_padding padding] [-debug_broken_protocol]
[-no_middlebox] [-rand files] [-writerand
file] [-provider name] [-provider-path
path] [-propquery propq] [-engine id]
[-ssl_client_engine id] [-allow_proxy_certs]
[-attime timestamp] [-no_check_time]
[-check_ss_sig] [-crl_check] [-crl_check_all]
[-explicit_policy] [-extended_crl] [-ignore_critical]
[-inhibit_any] [-inhibit_map] [-partial_chain]
[-policy arg] [-policy_check] [-policy_print]
[-purpose purpose] [-suiteB_128]
[-suiteB_128_only] [-suiteB_192] [-trusted_first]
[-no_alt_chains] [-use_deltas] [-auth_level num]
[-verify_depth num] [-verify_email email]
[-verify_hostname hostname] [-verify_ip ip]
[-verify_name name] [-x509_strict]
This command implements a generic SSL/TLS client which connects to a remote host
using SSL/TLS. It is a very useful diagnostic tool for SSL servers.
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 SSL_CONF_cmd(3) manual page.
If a connection is established with an SSL server then any data received from
the server is displayed and any key presses will be sent to the server. If end
of file is reached then the connection will be closed down. When used
interactively (which means neither -quiet nor -ign_eof have been
given), then certain commands are also recognized which perform special
operations. These commands are a letter which must appear at the start of a
line. They are listed below.
- Print out a usage message.
- -ssl_config section
- Use the specified section of the configuration file to configure the
- -connect host: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.
- -host hostname
- Host to connect to; use -connect instead.
- -port port
- Connect to the specified port; use -connect instead.
- -bind 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.
- -proxy host:port
- When used with the -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.
- -proxy_user userid
- When used with the -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.
- -proxy_pass arg
- The proxy password source, used with the -proxy_user flag. For more
information about the format of arg see
- -unix path
- Connect over the specified Unix-domain socket.
- Use IPv4 only.
- Use IPv6 only.
- -servername name
- Set the TLS SNI (Server Name Indication) extension in the ClientHello
message to the given value. If -servername is not provided, the TLS
SNI extension will be populated with the name given to -connect if
it follows a DNS name format. If -connect is not provided either,
the SNI is set to "localhost". This is the default since OpenSSL
Even though SNI should normally be a DNS name and not an IP
address, if -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
- Suppresses sending of the SNI (Server Name Indication) extension in the
ClientHello message. Cannot be used in conjunction with the
-servername or -dane_tlsa_domain options.
- -cert 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
- -certform DER|PEM|P12
- The client certificate file format to use; unspecified by default. See
openssl-format-options(1) for details.
- A file or URI of untrusted certificates to use when attempting to build
the certificate chain related to the certificate specified via the
-cert option. The input can be in PEM, DER, or PKCS#12 format.
- Specify whether the application should build the client certificate chain
to be provided to the server.
- -CRL filename
- CRL file to use to check the server's certificate.
- -CRLform DER|PEM
- The CRL file format; unspecified by default. See
openssl-format-options(1) for details.
- Download CRL from distribution points in the certificate.
- -key filename|uri
- The client private key to use. If not specified then the certificate file
will be used to read also the key.
- -keyform DER|PEM|P12|ENGINE
- The key format; unspecified by default. See
openssl-format-options(1) for details.
- -pass arg
- the private key and certifiate file password source. For more information
about the format of arg see
- -verify 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.
- Return verification errors instead of continuing. This will typically
abort the handshake with a fatal error.
- Limit verify output to only errors.
- -verifyCAfile filename
- A file in PEM format containing trusted certificates to use for verifying
the server's certificate.
- -verifyCApath dir
- A directory containing trusted certificates to use for verifying the
server's certificate. This directory must be in "hash format",
see openssl-verify(1) for more information.
- -verifyCAstore uri
- The URI of a store containing trusted certificates to use for verifying
the server's certificate.
- -chainCAfile file
- A file in PEM format containing trusted certificates to use when
attempting to build the client certificate chain.
- -chainCApath 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 openssl-verify(1) for more
- -chainCAstore 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
"file:" scheme, this acts as
-chainCAfile or -chainCApath, depending on if the URI
indicates a directory or a single file. See ossl_store-file(7) for
more information on the "file:"
- -requestCAfile file
- A file containing a list of certificates whose subject names will be sent
to the server in the certificate_authorities extension. Only
supported for TLS 1.3
- -dane_tlsa_domain 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 -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.
- -dane_tlsa_rrdata rrdata
- Use one or more times to specify the RRDATA fields of the DANE TLSA RRset
associated with the target service. The 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
Verified peername: smtp.example.com
DANE TLSA 2 1 1 ...ee12d2cc90180517616e8a18 matched TA certificate at depth 1
- 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.
- Reconnects to the same server 5 times using the same session ID, this can
be used as a test that session caching is working.
- 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 not a verified chain.
- 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.
- Prints out the SSL session states.
- Print extensive debugging information including a hex dump of all
- Do not use interactive command letters.
- Enable security debug messages.
- Output more security debug output.
- Show protocol messages.
- Enable send/receive timeout on DTLS connections.
- -mtu size
- Set MTU of the link layer to the specified size.
- Disable Encrypt-then-MAC negotiation.
- -keymatexport label
- Export keying material using the specified label.
- -keymatexportlen len
- Export the specified number of bytes of keying material; default is 20.
Show all protocol messages with hex dump.
- Show verbose trace output of protocol messages.
- -msgfile filename
- File to send output of -msg or -trace to, default standard
- Tests nonblocking I/O
- Turns on nonblocking I/O
- This option translated a line feed from the terminal into CR+LF as
required by some servers.
- Inhibit shutting down the connection when end of file is reached in the
- Inhibit printing of session and certificate information. This implicitly
turns on -ign_eof as well.
- Shut down the connection when end of file is reached in the input. Can be
used to override the implicit -ign_eof after -quiet.
- -psk_identity identity
- Use the PSK identity identity when using a PSK cipher suite. The
default value is "Client_identity" (without the quotes).
- -psk key
- Use the PSK key 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.
- -psk_session file
- Use the pem encoded SSL_SESSION data stored in file as the basis of
a PSK. Note that this will only work if TLSv1.3 is negotiated.
- Use SCTP for the transport protocol instead of UDP in DTLS. Must be used
in conjunction with -dtls, -dtls1 or -dtls1_2. This
option is only available where OpenSSL has support for SCTP enabled.
- 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 -sctp. This option is only available where OpenSSL has support
for SCTP enabled.
- Send TLS_FALLBACK_SCSV in the ClientHello.
- 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 -engine option. For test purposes the
dummy async engine (dasync) can be used (if available).
- -maxfraglen len
- Enable Maximum Fragment Length Negotiation; allowed values are
2048, and 4096.
- -max_send_frag int
- The maximum size of data fragment to send. See
SSL_CTX_set_max_send_fragment(3) for further information.
- -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 cipher suite has been negotiated, an engine
that supports pipelining has been loaded, and max_pipelines is greater
than 1. See SSL_CTX_set_split_send_fragment(3) for further
- -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 cipher suite has been negotiated. The
default value is 1. See SSL_CTX_set_max_pipelines(3) for further
- -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
SSL_CTX_set_default_read_buffer_len(3) for further
- Some TLS implementations do not send the mandatory close_notify alert on
shutdown. If the application tries to wait for the close_notify alert but
the peer closes the connection without sending it, an error is generated.
When this option is enabled the peer does not need to send the
close_notify alert and a closed connection will be treated as if the
close_notify alert was received. For more information on shutting down a
connection, see SSL_shutdown(3).
- There are several known bugs in SSL and TLS implementations. Adding this
option enables various workarounds.
- Enables support for SSL/TLS compression. This option was introduced in
OpenSSL 1.1.0. TLS compression is not recommended and is off by default as
of OpenSSL 1.1.0.
- Disables support for SSL/TLS compression. TLS compression is not
recommended and is off by default as of OpenSSL 1.1.0.
- Only provide a brief summary of connection parameters instead of the
normal verbose output.
- -sigalgs sigalglist
- Specifies the list of signature algorithms that are sent by the client.
The server selects one entry in the list based on its preferences. For
example strings, see SSL_CTX_set1_sigalgs(3)
- -curves curvelist
- Specifies the list of supported curves to be sent by the client. The curve
is ultimately selected by the server. For a list of all curves, use:
$ openssl ecparam -list_curves
- -cipher cipherlist
- This allows the TLSv1.2 and below cipher list sent by the client to be
modified. This list will be combined with any TLSv1.3 ciphersuites that
have been configured. Although the server determines which ciphersuite is
used it should take the first supported cipher in the list sent by the
client. See openssl-ciphers(1) for more information.
- -ciphersuites val
- This allows the TLSv1.3 ciphersuites sent by the client to be modified.
This list will be combined with any TLSv1.2 and below ciphersuites that
have been configured. Although the server determines which cipher suite is
used it should take the first supported cipher in the list sent by the
client. See openssl-ciphers(1) for more information. The format for
this list is a simple colon (":") separated list of TLSv1.3
- -starttls protocol
- Send the protocol-specific message(s) to switch to TLS for communication.
protocol is a keyword for the intended protocol. Currently, the
only supported keywords are "smtp", "pop3",
"imap", "ftp", "xmpp",
"xmpp-server", "irc", "postgres",
"mysql", "lmtp", "nntp", "sieve"
- -xmpphost hostname
- This option, when used with "-starttls xmpp" or "-starttls
xmpp-server", specifies the host for the "to" attribute of
the stream element. If this option is not specified, then the host
specified with "-connect" will be used.
This option is an alias of the -name option for
"xmpp" and "xmpp-server".
- -name hostname
- This option is used to specify hostname information for various protocols
used with -starttls option. Currently only "xmpp",
"xmpp-server", "smtp" and "lmtp" can utilize
this -name option.
If this option is used with "-starttls xmpp" or
"-starttls xmpp-server", if specifies the host for the
"to" attribute of the stream element. If this option is not
specified, then the host specified with "-connect" will be
If this option is used with "-starttls lmtp" or
"-starttls smtp", it specifies the name to use in the
"LMTP LHLO" or "SMTP EHLO" message, respectively. If
this option is not specified, then "mail.example.com" will be
- Print out a hex dump of any TLS extensions received from the server.
- Disable RFC4507bis session ticket support.
- -sess_out filename
- Output SSL session to filename.
- -sess_in filename
- Load SSL session from filename. The client will attempt to resume a
connection from this session.
- -serverinfo types
- 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
- Sends a certificate status request to the server (OCSP stapling). The
server response (if any) is printed out.
- -alpn protocols, -nextprotoneg protocols
- These flags enable the Enable the Application-Layer Protocol Negotiation
or Next Protocol Negotiation (NPN) extension, respectively. ALPN is the
IETF standard and replaces NPN. The protocols list is a
comma-separated list of protocol names that the client should advertise
support for. The list should contain the most desirable protocols first.
Protocol names are printable ASCII strings, for example
"http/1.1" or "spdy/3". An empty list of protocols is
treated specially and will cause the client to advertise support for the
TLS extension but disconnect just after receiving ServerHello with a list
of server supported protocols. The flag -nextprotoneg cannot be
specified if -tls1_3 is used.
- -ct, -noct
- Use one of these two options to control whether Certificate Transparency
(CT) is enabled (-ct) or disabled (-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.
- A file containing a list of known Certificate Transparency logs. See
SSL_CTX_set_ctlog_list_file(3) for the expected file format.
- -keylogfile file
- Appends TLS secrets to the specified keylog file such that external
programs (like Wireshark) can decrypt TLS connections.
- -early_data file
- Reads the contents of the specified file and attempts to send it as early
data to the server. This will only work with resumed sessions that support
early data and when the server accepts the early data.
- For TLSv1.3 only, send the Post-Handshake Authentication extension. This
will happen whether or not a certificate has been provided via
- -use_srtp value
- Offer SRTP key management, where value is a colon-separated profile
- -srpuser value
- Set the SRP username to the specified value. This option is
- -srppass value
- Set the SRP password to the specified value. This option is
- SRP username for the second ClientHello message. This option is
- -srp_moregroups This option is deprecated.
- Tolerate other than the known g and N values.
- -srp_strength number
- Set the minimal acceptable length, in bits, for N. This option is
- -no_ssl3, -no_tls1, -no_tls1_1, -no_tls1_2,
-no_tls1_3, -ssl3, -tls1, -tls1_1,
- See "TLS Version Options" in openssl(1).
- -dtls, -dtls1, -dtls1_2
- These specify the use of DTLS instead of TLS. See "TLS Version
Options" in openssl(1).
- -nameopt option
- This specifies how the subject or issuer names are displayed. See
openssl-namedisplay-options(1) for details.
- -xkey infile, -xcert file, -xchain
file, -xchain_build file, -xcertform
DER|PEM, -xkeyform DER|PEM
- Set extended certificate verification options. See "Extended
Verification Options" in openssl-verification-options(1) for
- -CAfile file, -no-CAfile, -CApath dir,
-no-CApath, -CAstore uri, -no-CAstore
- See "Trusted Certificate Options" in
openssl-verification-options(1) for details.
- -bugs, -comp, -no_comp, -no_ticket,
-no_legacy_server_connect, -no_etm -allow_no_dhe_kex,
-prioritize_chacha, -strict, -sigalgs algs,
-client_sigalgs algs, -groups groups,
-curves curves, -named_curve curve,
-cipher ciphers, -ciphersuites 1.3ciphers,
-min_protocol minprot, -max_protocol maxprot,
-record_padding padding, -debug_broken_protocol,
- See "SUPPORTED COMMAND LINE COMMANDS" in SSL_CONF_cmd(3)
- -rand files, -writerand file
- See "Random State Options" in openssl(1) for
- -provider name
- -provider-path path
- -propquery propq
- See "Provider Options" in openssl(1), provider(7),
- -engine id
- See "Engine Options" in openssl(1). This option is
- -ssl_client_engine id
- Specify engine to be used for client certificate operations.
- -allow_proxy_certs, -attime, -no_check_time,
-check_ss_sig, -crl_check, -crl_check_all,
-explicit_policy, -extended_crl, -ignore_critical,
-inhibit_any, -inhibit_map, -no_alt_chains,
-partial_chain, -policy, -policy_check,
-policy_print, -purpose, -suiteB_128,
-suiteB_128_only, -suiteB_192, -trusted_first,
-use_deltas, -auth_level, -verify_depth,
-verify_email, -verify_hostname, -verify_ip,
-verify_name, -x509_strict -issuer_checks
- Set various options of certificate chain verification. See
"Verification Options" in openssl-verification-options(1)
Verification errors are displayed, for debugging, but the
command will proceed unless the -verify_return_error option is
- Rather than providing -connect, the target hostname and optional
port may be provided as a single positional argument after all options. If
neither this nor -connect are provided, falls back to attempting to
connect to localhost on port 4433.
This command can be used to debug SSL servers. To connect to an SSL HTTP server
- End the current SSL connection and exit.
- Renegotiate the SSL session (TLSv1.2 and below only).
- Send a key update message to the server (TLSv1.3 only)
- Send a key update message to the server and request one back (TLSv1.3
openssl s_client -connect servername:443
would typically be used (https uses port 443). If the connection
succeeds then an HTTP command can be given such as "GET /" to
retrieve a web page.
If the handshake fails then there are several possible causes, if
it is nothing obvious like no client certificate then the -bugs,
-ssl3, -tls1, -no_ssl3, -no_tls1 options can be
tried in case it is a buggy server. In particular you should play with these
options before submitting a bug report to an OpenSSL mailing
A frequent problem when attempting to get client certificates
working is that a web client complains it has no certificates or gives an
empty list to choose from. This is normally because the server is not
sending the clients certificate authority in its "acceptable CA
list" when it requests a certificate. By using this command, the CA
list can be viewed and checked. However, some servers only request client
authentication after a specific URL is requested. To obtain the list in this
case it is necessary to use the -prexit option and send an HTTP
request for an appropriate page.
If a certificate is specified on the command line using the
-cert option it will not be used unless the server specifically
requests a client certificate. Therefore, merely including a client
certificate on the command line is no guarantee that the certificate
If there are problems verifying a server certificate then the
-showcerts option can be used to show all the certificates sent by
This command is a test tool and is designed to continue the
handshake after any certificate verification errors. As a result it will
accept any certificate chain (trusted or not) sent by the peer. Non-test
applications should not do this as it makes them vulnerable to a MITM
attack. This behaviour can be changed by with the
-verify_return_error option: any verify errors are then returned
aborting the handshake.
The -bind option may be useful if the server or a firewall
requires connections to come from some particular address and or port.
Because this program has a lot of options and also because some of the
techniques used are rather old, the C source for this command 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 -prexit option is a bit of a hack. We should really
report information whenever a session is renegotiated.
openssl(1), openssl-sess_id(1), openssl-s_server(1),
The -no_alt_chains option was added in OpenSSL 1.1.0. The -name
option was added in OpenSSL 1.1.1.
The -certform option has become obsolete in OpenSSL 3.0.0
and has no effect.
The -engine option was deprecated in OpenSSL 3.0.
Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.
Licensed under the Apache License 2.0 (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
Visit the GSP FreeBSD Man Page Interface.
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