In addition to the options below, this command also supports the common and server only options
documented "Supported Command Line Commands" in SSL_CONF_cmd(3)
-help
Print out a usage message.
-port+int
The TCP port to listen on for connections. If not specified 4433 is used.
-acceptval
The optional TCP host and port to listen on for connections. If not specified, *:4433 is used.
-unixval
Unix domain socket to accept on.
-4 Use IPv4 only.
-6 Use IPv6 only.
-unlink
For -unix, unlink any existing socket first.
-contextval
Sets the SSL context id. It can be given any string value. If this option is not present a default
value will be used.
-verifyint, -Verifyint
The verify depth to use. This specifies the maximum length of the client certificate chain and makes
the server request a certificate from the client. With the -verify option a certificate is requested
but the client does not have to send one, with the -Verify option the client must supply a
certificate or an error occurs.
If the cipher suite cannot request a client certificate (for example an anonymous cipher suite or
PSK) this option has no effect.
By default, validation of any supplied client certificate and its chain is done w.r.t. the (D)TLS
Client ("sslclient") purpose. For details see "Certificate Extensions" in
openssl-verification-options(1).
-certinfile
The certificate to use, most servers cipher suites require the use of a certificate and some require
a certificate with a certain public key type: for example the DSS cipher suites require a certificate
containing a DSS (DSA) key. If not specified then the filename server.pem will be used.
-cert2infile
The certificate file to use for servername; default is "server2.pem".
-certformDER|PEM|P12
The server certificate file format; unspecified by default. See openssl-format-options(1) for
details.
-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 -cert option. These untrusted certificates are sent to clients
and used for generating certificate status (aka OCSP stapling) requests. The input can be in PEM,
DER, or PKCS#12 format.
-build_chain
Specify whether the application should build the server certificate chain to be provided to the
client.
-serverinfoval
A file containing one or more blocks of PEM data. Each PEM block must encode a TLS ServerHello
extension (2 bytes type, 2 bytes length, followed by "length" bytes of extension data). If the
client sends an empty TLS ClientHello extension matching the type, the corresponding ServerHello
extension will be returned.
-keyfilename|uri
The private key to use. If not specified then the certificate file will be used.
-key2filename|uri
The private Key file to use for servername if not given via -cert2.
-keyformDER|PEM|P12|ENGINE
The key format; unspecified by default. See openssl-format-options(1) for details.
-passval
The private key and certificate file password source. For more information about the format of val,
see openssl-passphrase-options(1).
-dcertinfile, -dkeyfilename|uri
Specify an additional certificate and private key, these behave in the same manner as the -cert and
-key options except there is no default if they are not specified (no additional certificate and key
is used). As noted above some cipher suites require a certificate containing a key of a certain type.
Some cipher suites need a certificate carrying an RSA key and some a DSS (DSA) key. By using RSA and
DSS certificates and keys a server can support clients which only support RSA or DSS cipher suites by
using an appropriate certificate.
-dcert_chain
A file or URI of untrusted certificates to use when attempting to build the server certificate chain
when a certificate specified via the -dcert option is in use. The input can be in PEM, DER, or
PKCS#12 format.
-dcertformDER|PEM|P12
The format of the additional certificate file; unspecified by default. See openssl-format-options(1)
for details.
-dkeyformDER|PEM|P12|ENGINE
The format of the additional private key; unspecified by default. See openssl-format-options(1) for
details.
-dpassval
The passphrase for the additional private key and certificate. For more information about the format
of val, see openssl-passphrase-options(1).
-nbio_test
Tests non blocking I/O.
-crlf
This option translated a line feed from the terminal into CR+LF.
-debug
Print extensive debugging information including a hex dump of all traffic.
-security_debug
Print output from SSL/TLS security framework.
-security_debug_verbose
Print more output from SSL/TLS security framework
-msg
Show all protocol messages with hex dump.
-msgfileoutfile
File to send output of -msg or -trace to, default standard output.
-state
Prints the SSL session states.
-CRLinfile
The CRL file to use.
-CRLformDER|PEM
The CRL file format; unspecified by default. See openssl-format-options(1) for details.
-crl_download
Download CRLs from distribution points given in CDP extensions of certificates
-verifyCAfilefilename
A file in PEM format CA containing trusted certificates to use for verifying client certificates.
-verifyCApathdir
A directory containing trusted certificates to use for verifying client certificates. This directory
must be in "hash format", see openssl-verify(1) for more information.
-verifyCAstoreuri
The URI of a store containing trusted certificates to use for verifying client certificates.
-chainCAfilefile
A file in PEM format containing trusted certificates to use when attempting to build the server
certificate chain.
-chainCApathdir
A directory containing trusted certificates to use for building the server certificate chain provided
to the client. This directory must be in "hash format", see openssl-verify(1) for more information.
-chainCAstoreuri
The URI of a store containing trusted certificates to use for building the server certificate chain
provided to the client. 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:"
scheme.
-nocert
If this option is set then no certificate is used. This restricts the cipher suites available to the
anonymous ones (currently just anonymous DH).
-quiet
Inhibit printing of session and certificate information.
-no_resume_ephemeral
Disable caching and tickets if ephemeral (EC)DH is used.
-tlsextdebug
Print a hex dump of any TLS extensions received from the server.
-www
Sends a status message back to the client when it connects. This includes information about the
ciphers used and various session parameters. The output is in HTML format so this option can be used
with a web browser. The special URL "/renegcert" turns on client cert validation, and "/reneg" tells
the server to request renegotiation. The -early_data option cannot be used with this option.
-WWW, -HTTP
Emulates a simple web server. Pages will be resolved relative to the current directory, for example
if the URL "https://myhost/page.html" is requested the file ./page.html will be sent. If the -HTTP
flag is used, the files are sent directly, and should contain any HTTP response headers (including
status response line). If the -WWW option is used, the response headers are generated by the server,
and the file extension is examined to determine the Content-Type header. Extensions of "html",
"htm", and "php" are "text/html" and all others are "text/plain". In addition, the special URL
"/stats" will return status information like the -www option. Neither of these options can be used
in conjunction with -early_data.
-http_server_binmode
When acting as web-server (using option -WWW or -HTTP) open files requested by the client in binary
mode.
-no_ca_names
Disable TLS Extension CA Names. You may want to disable it for security reasons or for compatibility
with some Windows TLS implementations crashing when this extension is larger than 1024 bytes.
-ignore_unexpected_eof
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).
-servername
Servername for HostName TLS extension.
-servername_fatal
On servername mismatch send fatal alert (default: warning alert).
-id_prefixval
Generate SSL/TLS session IDs prefixed by val. This is mostly useful for testing any SSL/TLS code
(e.g. proxies) that wish to deal with multiple servers, when each of which might be generating a
unique range of session IDs (e.g. with a certain prefix).
-keymatexport
Export keying material using label.
-keymatexportlen
Export the given number of bytes of keying material; default 20.
-no_cache
Disable session cache.
-ext_cache.
Disable internal cache, set up and use external cache.
-verify_return_error
Verification errors normally just print a message but allow the connection to continue, for debugging
purposes. If this option is used, then verification errors close the connection.
-verify_quiet
No verify output except verify errors.
-ign_eof
Ignore input EOF (default: when -quiet).
-no_ign_eof
Do not ignore input EOF.
-no_etm
Disable Encrypt-then-MAC negotiation.
-no_ems
Disable Extended master secret negotiation.
-status
Enables certificate status request support (aka OCSP stapling).
-status_verbose
Enables certificate status request support (aka OCSP stapling) and gives a verbose printout of the
OCSP response. Use the -cert_chain option to specify the certificate of the server's certificate
signer that is required for certificate status requests.
-status_timeoutint
Sets the timeout for OCSP response to int seconds.
-proxy[http[s]://][userinfo@]host[:port][/path][?query][#fragment]
The HTTP(S) proxy server to use for reaching the OCSP server unless -no_proxy applies, see below. If
the host string is an IPv6 address, it must be enclosed in "[" and "]". The proxy port defaults to
80 or 443 if the scheme is "https"; apart from that the optional "http://" or "https://" prefix is
ignored, as well as any userinfo, path, query, and fragment components. Defaults to the environment
variable "http_proxy" if set, else "HTTP_PROXY" in case no TLS is used, otherwise "https_proxy" if
set, else "HTTPS_PROXY".
-no_proxyaddresses
List of IP addresses and/or DNS names of servers not to use an HTTP(S) proxy for, separated by commas
and/or whitespace (where in the latter case the whole argument must be enclosed in "..."). Default
is from the environment variable "no_proxy" if set, else "NO_PROXY".
-status_urlval
Sets a fallback responder URL to use if no responder URL is present in the server certificate.
Without this option an error is returned if the server certificate does not contain a responder
address. The optional userinfo and fragment URL components are ignored. Any given query component
is handled as part of the path component.
-status_fileinfile
Overrides any OCSP responder URLs from the certificate and always provides the OCSP Response stored
in the file. The file must be in DER format.
-ssl_configval
Configure SSL_CTX using the given configuration value.
-trace
Show verbose trace output of protocol messages.
-brief
Provide a brief summary of connection parameters instead of the normal verbose output.
-rev
Simple echo server that sends back received text reversed. Also sets -brief. Cannot be used in
conjunction with -early_data.
-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 -engine option. For test
purposes the dummy async engine (dasync) can be used (if available).
-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 information.
-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
information.
-naccept+int
The server will exit after receiving the specified number of connections, default unlimited.
-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 information).
-bugs
There are several known bugs in SSL and TLS implementations. Adding this option enables various
workarounds.
-no_tx_cert_comp
Disables support for sending TLSv1.3 compressed certificates.
-no_rx_cert_comp
Disables support for receiving TLSv1.3 compressed certificates.
-no_comp
Disable negotiation of TLS compression. TLS compression is not recommended and is off by default as
of OpenSSL 1.1.0.
-comp
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. TLS compression can only be
used in security level 1 or lower. From OpenSSL 3.2.0 and above the default security level is 2, so
this option will have no effect without also changing the security level. Use the -cipher option to
change the security level. See openssl-ciphers(1) for more information.
-no_ticket
Disable RFC4507bis session ticket support. This option has no effect if TLSv1.3 is negotiated. See
-num_tickets.
-num_tickets
Control the number of tickets that will be sent to the client after a full handshake in TLSv1.3. The
default number of tickets is 2. This option does not affect the number of tickets sent after a
resumption handshake.
-serverpref
Use the server's cipher preferences, rather than the client's preferences.
-prioritize_chacha
Prioritize ChaCha ciphers when preferred by clients. Requires -serverpref.
-no_resumption_on_reneg
Set the SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION option.
-client_sigalgsval
Signature algorithms to support for client certificate authentication (colon-separated list).
-named_curveval
Specifies the elliptic curve to use. NOTE: this is single curve, not a list.
The list of all supported groups includes named EC parameters as well as X25519 and X448 or FFDHE
groups, and may also include groups implemented in 3rd-party providers. For a list of named EC
parameters, use:
$ openssl ecparam -list_curves
-cipherval
This allows the list of TLSv1.2 and below ciphersuites used by the server to be modified. This list
is combined with any TLSv1.3 ciphersuites that have been configured. When the client sends a list of
supported ciphers the first client cipher also included in the server list is used. Because the
client specifies the preference order, the order of the server cipherlist is irrelevant. See
openssl-ciphers(1) for more information.
-ciphersuitesval
This allows the list of TLSv1.3 ciphersuites used by the server to be modified. This list is
combined with any TLSv1.2 and below ciphersuites that have been configured. When the client sends a
list of supported ciphers the first client cipher also included in the server list is used. Because
the client specifies the preference order, the order of the server cipherlist is irrelevant. See
openssl-ciphers(1) command for more information. The format for this list is a simple colon (":")
separated list of TLSv1.3 ciphersuite names.
-dhparaminfile
The DH parameter file to use. The ephemeral DH cipher suites generate keys using a set of DH
parameters. If not specified then an attempt is made to load the parameters from the server
certificate file. If this fails then a static set of parameters hard coded into this command will be
used.
-nbio
Turns on non blocking I/O.
-timeout
Enable timeouts.
-mtu
Set link-layer MTU.
-psk_identityval
Expect the client to send PSK identity val when using a PSK cipher suite, and warn if they do not.
By default, the expected PSK identity is the string "Client_identity".
-psk_hintval
Use the PSK identity hint val when using a PSK cipher suite.
-pskval
Use the PSK key val 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_sessionfile
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.
-srpvfile
The verifier file for SRP. This option is deprecated.
-srpuserseed
A seed string for a default user salt. This option is deprecated.
-listen
This option can only be used in conjunction with one of the DTLS options above. With this option,
this command will listen on a UDP port for incoming connections. Any ClientHellos that arrive will
be checked to see if they have a cookie in them or not. Any without a cookie will be responded to
with a HelloVerifyRequest. If a ClientHello with a cookie is received then this command will connect
to that peer and complete the handshake.
-sctp
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.
-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 -sctp. This option is
only available where OpenSSL has support for SCTP enabled.
-use_srtp
Offer SRTP key management with a colon-separated profile list.
-no_dhe
If this option is set then no DH parameters will be loaded effectively disabling the ephemeral DH
cipher suites.
-alpnval, -nextprotonegval
These flags enable the Application-Layer Protocol Negotiation or Next Protocol Negotiation (NPN)
extension, respectively. ALPN is the IETF standard and replaces NPN. The val list is a comma-
separated list of supported protocol names. The list should contain the most desirable protocols
first. Protocol names are printable ASCII strings, for example "http/1.1" or "spdy/3". The flag
-nextprotoneg cannot be specified if -tls1_3 is used.
-ktls
Enable Kernel TLS for sending and receiving. This option was introduced in OpenSSL 3.2.0. Kernel
TLS is off by default as of OpenSSL 3.2.0.
-sendfile
If this option is set and KTLS is enabled, SSL_sendfile() will be used instead of BIO_write() to send
the HTTP response requested by a client. This option is only valid when -ktls along with -WWW or
-HTTP are specified.
-zerocopy_sendfile
If this option is set, SSL_sendfile() will use the zerocopy TX mode, which gives a performance boost
when used with KTLS hardware offload. Note that invalid TLS records might be transmitted if the file
is changed while being sent. This option depends on -sendfile; when used alone, -sendfile is
implied, and a warning is shown. Note that KTLS sendfile on FreeBSD always runs in the zerocopy mode.
-keylogfileoutfile
Appends TLS secrets to the specified keylog file such that external programs (like Wireshark) can
decrypt TLS connections.
-max_early_dataint
Change the default maximum early data bytes that are specified for new sessions and any incoming
early data (when used in conjunction with the -early_data flag). The default value is approximately
16k. The argument must be an integer greater than or equal to 0.
-recv_max_early_dataint
Specify the hard limit on the maximum number of early data bytes that will be accepted.
-early_data
Accept early data where possible. Cannot be used in conjunction with -www, -WWW, -HTTP or -rev.
-stateless
Require TLSv1.3 cookies.
-anti_replay, -no_anti_replay
Switches replay protection on or off, respectively. Replay protection is on by default unless
overridden by a configuration file. When it is on, OpenSSL will automatically detect if a session
ticket has been used more than once, TLSv1.3 has been negotiated, and early data is enabled on the
server. A full handshake is forced if a session ticket is used a second or subsequent time. Any early
data that was sent will be rejected.
-tfo
Enable acceptance of TCP Fast Open (RFC7413) connections.
-cert_comp
Pre-compresses certificates (RFC8879) that will be sent during the handshake.
-nameoptoption
This specifies how the subject or issuer names are displayed. See openssl-namedisplay-options(1) for
details.
-no_ssl3, -no_tls1, -no_tls1_1, -no_tls1_2, -no_tls1_3, -ssl3, -tls1, -tls1_1, -tls1_2, -tls1_3
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).
-bugs, -comp, -no_comp, -no_ticket, -serverpref, -client_renegotiation, -legacy_renegotiation,
-no_renegotiation, -no_resumption_on_reneg, -legacy_server_connect, -no_legacy_server_connect, -no_etm-allow_no_dhe_kex, -prefer_no_dhe_kex, -prioritize_chacha, -strict, -sigalgsalgs, -client_sigalgsalgs,
-groupsgroups, -curvescurves, -named_curvecurve, -cipherciphers, -ciphersuites1.3ciphers,
-min_protocolminprot, -max_protocolmaxprot, -record_paddingpadding, -debug_broken_protocol,
-no_middlebox
See "SUPPORTED COMMAND LINE COMMANDS" in SSL_CONF_cmd(3) for details.
-xkeyinfile, -xcertfile, -xchainfile, -xchain_buildfile, -xcertformDER|PEM, -xkeyformDER|PEM
Set extended certificate verification options. See "Extended Verification Options" in
openssl-verification-options(1) for details.
-CAfilefile, -no-CAfile, -CApathdir, -no-CApath, -CAstoreuri, -no-CAstore
See "Trusted Certificate Options" in openssl-verification-options(1) for details.
-randfiles, -writerandfile
See "Random State Options" in openssl(1) for details.
-engineid
See "Engine Options" in openssl(1). This option is deprecated.
-providername-provider-pathpath-propquerypropq
See "Provider Options" in openssl(1), provider(7), and property(7).
-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) for details.
If the server requests a client certificate, then verification errors are displayed, for debugging,
but the command will proceed unless the -verify_return_error option is used.
-enable_server_rpk
Enable support for sending raw public keys (RFC7250) to the client. A raw public key will be sent by
the server, if solicited by the client, provided a suitable key and public certificate pair is
configured. Clients that don't support raw public keys or prefer to use X.509 certificates can still
elect to receive X.509 certificates as usual.
Raw public keys are extracted from the configured certificate/private key.
-enable_client_rpk
Enable support for receiving raw public keys (RFC7250) from the client. Use of X.509 certificates by
the client becomes optional, and clients that support raw public keys may elect to use them. Clients
that don't support raw public keys or prefer to use X.509 certificates can still elect to send X.509
certificates as usual.
Raw public keys are extracted from the configured certificate/private key.
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