OPENSSL-S_SERVER(1ossl) OpenSSL OPENSSL-S_SERVER(1ossl) NAME openssl-s_server - SSL/TLS server program SYNOPSIS openssl s_server [-help] [-port +int] [-accept val] [-unix val] [-4] [-6] [-unlink] [-context val] [-verify int] [-Verify int] [-cert infile] [-cert2 infile] [-certform DER|PEM|P12] [-cert_chain infile] [-build_chain] [-serverinfo val] [-key filename|uri] [-key2 filename|uri] [-keyform DER|PEM|P12] [-pass val] [-dcert infile] [-dcertform DER|PEM|P12] [-dcert_chain infile] [-dkey filename|uri] [-dkeyform DER|PEM|P12] [-dpass val] [-nbio_test] [-crlf] [-debug] [-msg] [-msgfile outfile] [-state] [-no- cert] [-quiet] [-no_resume_ephemeral] [-www] [-WWW] [-http_server_binmode] [-no_ca_names] [-ignore_unexpected_eof] [-servername] [-servername_fatal] [-tlsextdebug] [-HTTP] [-id_prefix val] [-keymatexport val] [-keymatex- portlen +int] [-CRL infile] [-CRLform DER|PEM] [-crl_download] [-chain- CAfile infile] [-chainCApath dir] [-chainCAstore uri] [-verifyCAfile in- file] [-verifyCApath dir] [-verifyCAstore uri] [-no_cache] [-ext_cache] [-verify_return_error] [-verify_quiet] [-ign_eof] [-no_ign_eof] [-no_ems] [-status] [-status_all] [-status_verbose] [-status_timeout int] [-proxy [http[s]://][userinfo@]host[:port][/path][?query][#fragment]] [-no_proxy addresses] [-status_url val] [-status_file infile] [-ssl_config val] [-trace] [-security_debug] [-security_debug_verbose] [-brief] [-rev] [-async] [-max_send_frag +int] [-split_send_frag +int] [-max_pipelines +int] [-naccept +int] [-read_buf +int] [-no_tx_cert_comp] [-no_rx_cert_comp] [-dhparam infile] [-nbio] [-psk_identity val] [-psk_hint val] [-psk val] [-psk_session file] [-srpvfile infile] [-srpuserseed val] [-timeout] [-mtu +int] [-listen] [-sctp] [-sctp_label_bug] [-use_srtp val] [-no_dhe] [-nextprotoneg val] [-alpn val] [-ktls] [-sendfile] [-zero- copy_sendfile] [-keylogfile outfile] [-recv_max_early_data int] [-max_early_data int] [-early_data] [-stateless] [-anti_replay] [-no_anti_replay] [-num_tickets] [-tfo] [-cert_comp] [-nameopt option] [-no_ssl3] [-no_tls1] [-no_tls1_1] [-no_tls1_2] [-no_tls1_3] [-tls1] [-tls1_1] [-tls1_2] [-tls1_3] [-dtls] [-dtls1] [-dtls1_2] [-al- low_proxy_certs] [-attime timestamp] [-no_check_time] [-check_ss_sig] [-crl_check] [-crl_check_all] [-explicit_policy] [-extended_crl] [-ig- nore_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] [-issuer_checks] [-bugs] [-no_comp] [-comp] [-no_ticket] [-serverpref] [-client_renegotiation] [-legacy_renegotiation] [-no_renego- tiation] [-no_resumption_on_reneg] [-legacy_server_connect] [-no_legacy_server_connect] [-no_etm] [-allow_no_dhe_kex] [-pre- fer_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] [-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] [-rand files] [-writerand file] [-provider name] [-provider-path path] [-provparam [name:]key=value] [-propquery propq] [-enable_server_rpk] [-en- able_client_rpk] [-expected-rpks] [-ech_key filename] [-ech_dir dirname] [-ech_noretry_dir dirname] [-ech_trialdecrypt] [-ech_greaseretries] DESCRIPTION This command implements a generic SSL/TLS server which listens for connec- tions on a given port using SSL/TLS. OPTIONS 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. -accept val The optional TCP host and port to listen on for connections. If not specified, *:4433 is used. -unix val Unix domain socket to accept on. -4 Use IPv4 only. -6 Use IPv6 only. -unlink For -unix, unlink any existing socket first. -context val Sets the SSL context id. It can be given any string value. If this op- tion is not present a default value will be used. -verify int, -Verify int 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). -cert infile 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 contain- ing a DSS (DSA) key. If not specified then the filename server.pem will be used. -cert2 infile The certificate file to use for servername; default is "server2.pem". -certform DER|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. -serverinfo val 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, fol- lowed 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. -key filename|uri The private key to use. If not specified then the certificate file will be used. -key2 filename|uri The private Key file to use for servername if not given via -cert2. -keyform DER|PEM|P12 The key format; unspecified by default. See openssl-format-options(1) for details. -pass val The private key and certificate file password source. For more infor- mation about the format of val, see openssl-passphrase-options(1). -dcert infile, -dkey filename|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 for- mat. -dcertform DER|PEM|P12 The format of the additional certificate file; unspecified by default. See openssl-format-options(1) for details. -dkeyform DER|PEM|P12 The format of the additional private key; unspecified by default. See openssl-format-options(1) for details. -dpass val The passphrase for the additional private key and certificate. For more information about the format of val, see openssl-passphrase-op- tions(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 traf- fic. -security_debug Print output from SSL/TLS security framework. -security_debug_verbose Print more output from SSL/TLS security framework -msgShow all protocol messages with hex dump. -msgfile outfile File to send output of -msg or -trace to, default standard output. -state Prints the SSL session states. -CRL infile The CRL file to use. -CRLform DER|PEM The CRL file format; unspecified by default. See openssl-format-op- tions(1) for details. -crl_download Download CRLs from distribution points given in CDP extensions of cer- tificates -verifyCAfile filename A file in PEM format containing trusted CA certificates (root and/or intermediate) used to verify the client certificate chain. -verifyCApath dir 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. -verifyCAstore uri The URI of a store containing trusted certificates to use for verifying client certificates. When any of -verifyCAfile, -verifyCApath, or -verifyCAstore is speci- fied, they are loaded into a separate verification store (via SSL_CTX_set1_verify_cert_store(3)) and used for client certificate ver- ification instead of the store built from -CAfile, -CApath, and -CAs- tore. Note that -CAfile is the sole source of acceptable issuing CA names sent to the client in the Certificate Request message during the handshake; -CApath, -CAstore, and the -verifyCA* options do not con- tribute to this list. -chainCAfile file A file in PEM format containing trusted certificates to use when at- tempting to build the server certificate chain. -chainCApath dir 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. -chainCAstore uri The URI of a store containing trusted certificates to use for building the server certificate chain provided to the client. The URI may indi- cate a single certificate, as well as a collection of them. With URIs in the "file:" scheme, this acts as -chainCAfile or -chainCApath, de- pending 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. -wwwSends a status message back to the client when it connects. This in- cludes information about the ciphers used and various session parame- ters. The output is in HTML format so this option can be used with a web browser. The special URL "/renegcert" turns on client cert valida- tion, and "/reneg" tells the server to request renegotiation. -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 exten- sion 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. -http_server_binmode When acting as web-server (using option -WWW or -HTTP) open files re- quested 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 shut- ting 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_prefix val 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 ses- sion 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 connec- tion 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_ems Disable Extended master secret negotiation. -status Enables certificate status request support (aka OCSP stapling): an OCSP response is provided for the leaf (server) certificate if requested by the client side. -status_all Like before, but for TLS v1.3 and beyond, status responses for all cer- tificates in the chain (except the trust anchor) are provided if re- quested by the client side. -status_verbose Enables certificate status request support (aka OCSP stapling) and gives a verbose printout of the OCSP response. Use the -cert_chain op- tion to specify the certificate of the server's certificate signer that is required for certificate status requests. -status_timeout int 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_proxy addresses 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_url val 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 com- ponent is handled as part of the path component. -status_file infile Overrides any OCSP responder URLs from the certificate and always pro- vides the OCSP Response stored in the file. The file must be in DER format. This option may be used multiple times to specify OCSP re- sponses for all certificates in the server certificate chain. -ssl_config val 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. -revSimple 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 capa- ble provider is also used via the -provider option. -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 This is used for pipelines. There is currently no support for cipher pipelining in libssl. See SSL_CTX_set_max_send_fragment(3) for further information. -max_pipelines +int This is used for pipelines. There is currently no support for cipher pipelining in libssl. See SSL_CTX_set_max_send_fragment(3) for further information. -naccept +int The server will exit after receiving the specified number of connec- tions, 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_de- fault_read_buffer_len(3) for further information). -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 recom- mended and is off by default as of OpenSSL 1.1.0. -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 op- tion does not affect the number of tickets sent after a resumption handshake. -dhparam infile 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. -mtuSet link-layer MTU. -psk_identity val 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_hint val Use the PSK identity hint val when using a PSK cipher suite. -psk val 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_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. -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 op- tions 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 com- plete 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 com- puting endpoint-pair shared secrets for DTLS/SCTP. This allows communi- cation 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 en- abled. -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. -alpn val, -nextprotoneg val 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 exam- ple "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 intro- duced 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 spec- ified. -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. -keylogfile outfile Appends TLS secrets to the specified keylog file such that external programs (like Wireshark) can decrypt TLS connections. -max_early_data int 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_data int 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 re- jected. Note that the server manages an internal cache of session tickets. If a client closes the connection without sending the close_notify alert, the corresponding session ticket is removed and a full handshake is forced. -tfoEnable acceptance of TCP Fast Open (RFC7413) connections. -cert_comp Pre-compresses certificates (RFC8879) that will be sent during the handshake. -nameopt option 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, -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 Op- tions" 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 -al- low_no_dhe_kex, -prefer_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 See "SUPPORTED COMMAND LINE COMMANDS" in SSL_CONF_cmd(3) for details. -xkey infile, -xcert file, -xchain file, -xchain_build file, -xcertform DER|PEM, -xkeyform DER|PEM Set extended certificate verification options. See "Extended Verifica- tion Options" in openssl-verification-options(1) for details. -CAfile file, -no-CAfile, -CApath dir, -no-CApath, -CAstore uri, -no-CAs- tore See "Trusted Certificate Options" in openssl-verification-options(1) for details. -rand files, -writerand file See "Random State Options" in openssl(1) for details. -provider name -provider-path path -provparam [name:]key=value -propquery propq 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, -in- hibit_any, -inhibit_map, -no_alt_chains, -partial_chain, -policy, -pol- icy_check, -policy_print, -purpose, -suiteB_128, -suiteB_128_only, -suiteB_192, -trusted_first, -use_deltas, -auth_level, -verify_depth, -ver- ify_email, -verify_hostname, -verify_ip, -verify_name, -x509_strict -is- suer_checks Set various options of certificate chain verification. See "Verifica- tion 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 cer- tificates 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. -expected-rpks file This option implies the -enable_client_rpk option and can be specified multiple times. Each PEM file should contain one or more public keys, private keys or certificates. With a private key or certificate an at- tempt is made to extract the associated public key. Each resulting public key is added (via a call to SSL_add_expected_rpk(3) as a valid raw public key that the client may present to be considered verified. If a client nevertheless presents an X.509 certificate, the enclosed public key is validated as though it were presented as a raw public key instead. Verification success or failure is reported as a DANE verification suc- cess or failure, because verification of raw public keys is internally mapped to verification of DANE TLSA records derived from the specified keys. host:port -ech_key filename Load one Encrypted Client Hello (ECH) key pair. -ech_dir dirname Attempt to load an ECH key pair from every file in the named directory. Any keys successfully loaded will be returned in 'retry_configs'. -ech_noretry_dir dirname Attempt to load an ECH key pair from every file in the named directory. Keys loaded will not be returned in 'retry_configs'. -ech_trialdecrypt When an Encrypted Client Hello (ECH) extension is seen in a Clien- tHello, attempt to decrypt with all known ECH private keys if neces- sary. Without this, the ECH "config_id" is used to match against the loaded ECH private keys and decryption is only attempted when there's a match. -ech_greaseretries If set, servers will add GREASEy ECHConfig values to those sent in retry_configs. CONNECTED COMMANDS If a connection request is established with an SSL client and neither the -www nor the -WWW option has been used then normally any data received from the client is displayed and any key presses will be sent to the client. 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. q End the current SSL connection but still accept new connections. Q End the current SSL connection and exit. r Renegotiate the SSL session (TLSv1.2 and below only). R Renegotiate the SSL session and request a client certificate (TLSv1.2 and below only). P Send some plain text down the underlying TCP connection: this should cause the client to disconnect due to a protocol violation. S Print out some session cache status information. k Send a key update message to the client (TLSv1.3 only) K Send a key update message to the client and request one back (TLSv1.3 only) c Send a certificate request to the client (TLSv1.3 only) NOTES This command can be used to debug SSL clients. To accept connections from a web browser the command: openssl s_server -accept 443 -www can be used for example. Although specifying an empty list of CAs when requesting a client certifi- cate is strictly speaking a protocol violation, some SSL clients interpret this to mean any CA is acceptable. This is useful for debugging purposes. The session parameters can printed out using the openssl-sess_id(1) com- mand. BUGS 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 server program would be much simpler. The output of common ciphers is wrong: it just gives the list of ciphers that OpenSSL recognizes and the client supports. There should be a way for this command to print out details of any unknown cipher suites a client says it supports. SEE ALSO openssl(1), openssl-sess_id(1), openssl-s_client(1), openssl-ciphers(1), SSL_CONF_cmd(3), SSL_CTX_set_max_send_fragment(3), SSL_CTX_set_split_send_fragment(3), SSL_CTX_set_max_pipelines(3), ossl_store-file(7) HISTORY The -no_alt_chains option was added in OpenSSL 1.1.0. The -allow-no-dhe-kex and -prioritize_chacha options were added in OpenSSL 1.1.1. The -srpvfile and -srpuserseed option were deprecated in OpenSSL 3.0. The -enable_client_rpk, -enable_server_rpk, -no_rx_cert_comp, -no_tx_cert_comp, and -tfo options were added in OpenSSL 3.2. The -status_all option was added in OpenSSL 3.6. The ech options were added in OpenSSL 4.0. The -engine option was removed in OpenSSL 4.0. The -expected-rpks option was added in OpenSSL 4.0. COPYRIGHT Copyright 2000-2026 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 <https://www.openssl.org/source/license.html>. 4.0.2 2026-08-25 OPENSSL-S_SERVER(1ossl)
NAME | SYNOPSIS | DESCRIPTION | OPTIONS | CONNECTED COMMANDS | NOTES | BUGS | SEE ALSO | HISTORY | COPYRIGHT
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