=pod {- OpenSSL::safe::output_do_not_edit_headers(); -} =head1 NAME openssl-s_server - SSL/TLS server program =head1 SYNOPSIS B B [B<-help>] [B<-port> I<+int>] [B<-accept> I] [B<-unix> I] [B<-4>] [B<-6>] [B<-unlink>] [B<-context> I] [B<-verify> I] [B<-Verify> I] [B<-cert> I] [B<-cert2> I] [B<-certform> B|B|B] [B<-cert_chain> I] [B<-build_chain>] [B<-serverinfo> I] [B<-key> I] [B<-key2> I] [B<-keyform> B|B|B|B] [B<-pass> I] [B<-dcert> I] [B<-dcertform> B|B|B] [B<-dcert_chain> I] [B<-dkey> I] [B<-dkeyform> B|B|B|B] [B<-dpass> I] [B<-nbio_test>] [B<-crlf>] [B<-debug>] [B<-msg>] [B<-msgfile> I] [B<-state>] [B<-nocert>] [B<-quiet>] [B<-no_resume_ephemeral>] [B<-www>] [B<-WWW>] [B<-http_server_binmode>] [B<-no_ca_names>] [B<-servername>] [B<-servername_fatal>] [B<-tlsextdebug>] [B<-HTTP>] [B<-id_prefix> I] [B<-keymatexport> I] [B<-keymatexportlen> I<+int>] [B<-CRL> I] [B<-CRLform> B|B] [B<-crl_download>] [B<-chainCAfile> I] [B<-chainCApath> I] [B<-chainCAstore> I] [B<-verifyCAfile> I] [B<-verifyCApath> I] [B<-verifyCAstore> I] [B<-no_cache>] [B<-ext_cache>] [B<-verify_return_error>] [B<-verify_quiet>] [B<-ign_eof>] [B<-no_ign_eof>] [B<-status>] [B<-status_verbose>] [B<-status_timeout> I] [B<-status_url> I] [B<-status_file> I] [B<-trace>] [B<-security_debug>] [B<-security_debug_verbose>] [B<-brief>] [B<-rev>] [B<-async>] [B<-ssl_config> I] [B<-max_send_frag> I<+int>] [B<-split_send_frag> I<+int>] [B<-max_pipelines> I<+int>] [B<-naccept> I<+int>] [B<-read_buf> I<+int>] [B<-bugs>] [B<-no_comp>] [B<-comp>] [B<-no_ticket>] [B<-serverpref>] [B<-legacy_renegotiation>] [B<-no_renegotiation>] [B<-legacy_server_connect>] [B<-no_resumption_on_reneg>] [B<-no_legacy_server_connect>] [B<-allow_no_dhe_kex>] [B<-prioritize_chacha>] [B<-strict>] [B<-sigalgs> I] [B<-client_sigalgs> I] [B<-groups> I] [B<-curves> I] [B<-named_curve> I] [B<-cipher> I] [B<-ciphersuites> I] [B<-dhparam> I] [B<-record_padding> I] [B<-debug_broken_protocol>] [B<-nbio>] [B<-psk_identity> I] [B<-psk_hint> I] [B<-psk> I] [B<-psk_session> I] [B<-srpvfile> I] [B<-srpuserseed> I] [B<-timeout>] [B<-mtu> I<+int>] [B<-listen>] [B<-sctp>] [B<-sctp_label_bug>] [B<-no_dhe>] [B<-nextprotoneg> I] [B<-use_srtp> I] [B<-alpn> I] [B<-sendfile>] [B<-keylogfile> I] [B<-recv_max_early_data> I] [B<-max_early_data> I] [B<-early_data>] [B<-stateless>] [B<-anti_replay>] [B<-no_anti_replay>] [B<-num_tickets>] {- $OpenSSL::safe::opt_name_synopsis -} {- $OpenSSL::safe::opt_version_synopsis -} {- $OpenSSL::safe::opt_v_synopsis -} {- $OpenSSL::safe::opt_s_synopsis -} {- $OpenSSL::safe::opt_x_synopsis -} {- $OpenSSL::safe::opt_trust_synopsis -} {- $OpenSSL::safe::opt_r_synopsis -} {- $OpenSSL::safe::opt_engine_synopsis -} {- $OpenSSL::safe::opt_provider_synopsis -} =for openssl ifdef unix 4 6 unlink no_dhe nextprotoneg use_srtp engine =for openssl ifdef status status_verbose status_timeout status_url status_file =for openssl ifdef psk_hint srpvfile srpuserseed sctp sctp_label_bug =for openssl ifdef sctp sctp_label_bug trace mtu timeout listen =for openssl ifdef ssl3 tls1 tls1_1 tls1_2 tls1_3 dtls mtu dtls1 dtls1_2 =for openssl ifdef sendfile =head1 DESCRIPTION This command implements a generic SSL/TLS server which listens for connections on a given port using SSL/TLS. =head1 OPTIONS In addition to the options below, this command also supports the common and server only options documented L =over 4 =item B<-help> Print out a usage message. =item B<-port> I<+int> The TCP port to listen on for connections. If not specified 4433 is used. =item B<-accept> I The optional TCP host and port to listen on for connections. If not specified, *:4433 is used. =item B<-unix> I Unix domain socket to accept on. =item B<-4> Use IPv4 only. =item B<-6> Use IPv6 only. =item B<-unlink> For -unix, unlink any existing socket first. =item B<-context> I Sets the SSL context id. It can be given any string value. If this option is not present a default value will be used. =item B<-verify> I, B<-Verify> I 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 B<-verify> option a certificate is requested but the client does not have to send one, with the B<-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. =item B<-cert> I 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 F will be used. =item B<-certform> B|B|B The server certificate file format. This option has no effect and is retained for backward compatibility only. =item B<-cert_chain> A file containing untrusted certificates to use when attempting to build the certificate chain related to the certificate specified via the B<-cert> option. =item B<-build_chain> Specify whether the application should build the server certificate chain to be provided to the client. =item B<-serverinfo> I 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. =item B<-key> I The private key to use. If not specified then the certificate file will be used. =item B<-keyform> B|B|B|B The key format; the default is B. The only value with effect is B; all others have become obsolete. See L for details. =item B<-pass> I The private key password source. For more information about the format of I, see L. =item B<-dcert> I, B<-dkey> I Specify an additional certificate and private key, these behave in the same manner as the B<-cert> and B<-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. =item B<-dcert_chain> A file containing untrusted certificates to use when attempting to build the server certificate chain when a certificate specified via the B<-dcert> option is in use. =item B<-dcertform> B|B|B The format of the additional certificate file. This option has no effect and is retained for backward compatibility only. =item B<-dkeyform> B|B|B|B The format of the additional private key; the default is B. The only value with effect is B; all others have become obsolete. See L. =item B<-dpass> I The passphrase for the additional private key. For more information about the format of I, see L. =item B<-nbio_test> Tests non blocking I/O. =item B<-crlf> This option translated a line feed from the terminal into CR+LF. =item B<-debug> Print extensive debugging information including a hex dump of all traffic. =item B<-msg> Show all protocol messages with hex dump. =item B<-msgfile> I File to send output of B<-msg> or B<-trace> to, default standard output. =item B<-state> Prints the SSL session states. =item B<-CRL> I The CRL file to use. =item B<-CRLform> B|B The CRL file format; the default is B. See L for details. =item B<-crl_download> Download CRLs from distribution points given in CDP extensions of certificates =item B<-verifyCAfile> I A file in PEM format CA containing trusted certificates to use for verifying client certificates. =item B<-verifyCApath> I A directory containing trusted certificates to use for verifying client certificates. This directory must be in "hash format", see L for more information. =item B<-verifyCAstore> I The URI of a store containing trusted certificates to use for verifying client certificates. =item B<-chainCAfile> I A file in PEM format containing trusted certificates to use when attempting to build the server certificate chain. =item B<-chainCApath> I 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 L for more information. =item B<-chainCAstore> I 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 C scheme, this acts as B<-chainCAfile> or B<-chainCApath>, depending on if the URI indicates a directory or a single file. See L for more information on the C scheme. =item B<-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). =item B<-quiet> Inhibit printing of session and certificate information. =item B<-tlsextdebug> Print a hex dump of any TLS extensions received from the server. =item B<-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 C turns on client cert validation, and C tells the server to request renegotiation. The B<-early_data> option cannot be used with this option. =item B<-WWW>, B<-HTTP> Emulates a simple web server. Pages will be resolved relative to the current directory, for example if the URL C is requested the file F<./page.html> will be sent. If the B<-HTTP> flag is used, the files are sent directly, and should contain any HTTP response headers (including status response line). If the B<-WWW> option is used, the response headers are generated by the server, and the file extension is examined to determine the B header. Extensions of C, C, and C are C and all others are C. In addition, the special URL C will return status information like the B<-www> option. Neither of these options can be used in conjunction with B<-early_data>. =item B<-http_server_binmode> When acting as web-server (using option B<-WWW> or B<-HTTP>) open files requested by the client in binary mode. =item B<-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. =item B<-id_prefix> I Generate SSL/TLS session IDs prefixed by I. This is mostly useful for testing any SSL/TLS code (eg. proxies) that wish to deal with multiple servers, when each of which might be generating a unique range of session IDs (eg. with a certain prefix). =item B<-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. =item B<-status> Enables certificate status request support (aka OCSP stapling). =item B<-status_verbose> Enables certificate status request support (aka OCSP stapling) and gives a verbose printout of the OCSP response. =item B<-status_timeout> I Sets the timeout for OCSP response to I seconds. =item B<-status_url> I 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. =item B<-status_file> I 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. =item B<-trace> Show verbose trace output of protocol messages. OpenSSL needs to be compiled with B for this option to work. =item B<-brief> Provide a brief summary of connection parameters instead of the normal verbose output. =item B<-rev> Simple test server which just reverses the text received from the client and sends it back to the server. Also sets B<-brief>. Cannot be used in conjunction with B<-early_data>. =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<-max_send_frag> I<+int> The maximum size of data fragment to send. See L 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, 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 L for further information. =item B<-max_pipelines> I<+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 L for further information. =item B<-naccept> I<+int> The server will exit after receiving the specified number of connections, default unlimited. =item B<-read_buf> I<+int> The default read buffer size to be used for connections. This will only have an effect if the buffer size is larger than the size that would otherwise be used and pipelining is in use (see L for further information). =item B<-bugs> There are several known bugs in SSL and TLS implementations. Adding this option enables various workarounds. =item B<-no_comp> Disable negotiation of TLS compression. TLS compression is not recommended and is off by default as of OpenSSL 1.1.0. =item B<-comp> Enable negotiation of 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. =item B<-no_ticket> Disable RFC4507bis session ticket support. This option has no effect if TLSv1.3 is negotiated. See B<-num_tickets>. =item B<-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. =item B<-serverpref> Use the server's cipher preferences, rather than the client's preferences. =item B<-prioritize_chacha> Prioritize ChaCha ciphers when preferred by clients. Requires B<-serverpref>. =item B<-no_resumption_on_reneg> Set the B option. =item B<-client_sigalgs> I Signature algorithms to support for client certificate authentication (colon-separated list). =item B<-named_curve> I Specifies the elliptic curve to use. NOTE: this is single curve, not a list. For a list of all possible curves, use: $ openssl ecparam -list_curves =item B<-cipher> I 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 L for more information. =item B<-ciphersuites> I 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 L command for more information. The format for this list is a simple colon (":") separated list of TLSv1.3 ciphersuite names. =item B<-dhparam> I 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. =item B<-nbio> Turns on non blocking I/O. =item B<-psk_identity> I Expect the client to send PSK identity I when using a PSK cipher suite, and warn if they do not. By default, the expected PSK identity is the string "Client_identity". =item B<-psk_hint> I Use the PSK identity hint I when using a PSK cipher suite. =item B<-psk> I Use the PSK key I 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 Use the pem encoded SSL_SESSION data stored in I as the basis of a PSK. Note that this will only work if TLSv1.3 is negotiated. =item B<-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. =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<-no_dhe> If this option is set then no DH parameters will be loaded effectively disabling the ephemeral DH cipher suites. =item B<-alpn> I, B<-nextprotoneg> I 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 I 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 B<-nextprotoneg> cannot be specified if B<-tls1_3> is used. =item B<-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 if B<-WWW> or B<-HTTP> is specified. =item B<-keylogfile> I Appends TLS secrets to the specified keylog file such that external programs (like Wireshark) can decrypt TLS connections. =item B<-max_early_data> I Change the default maximum early data bytes that are specified for new sessions and any incoming early data (when used in conjunction with the B<-early_data> flag). The default value is approximately 16k. The argument must be an integer greater than or equal to 0. =item B<-recv_max_early_data> I Specify the hard limit on the maximum number of early data bytes that will be accepted. =item B<-early_data> Accept early data where possible. Cannot be used in conjunction with B<-www>, B<-WWW>, B<-HTTP> or B<-rev>. =item B<-stateless> Require TLSv1.3 cookies. =item B<-anti_replay>, B<-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. {- $OpenSSL::safe::opt_name_item -} {- $OpenSSL::safe::opt_version_item -} {- $OpenSSL::safe::opt_s_item -} {- $OpenSSL::safe::opt_x_item -} {- $OpenSSL::safe::opt_trust_item -} {- $OpenSSL::safe::opt_r_item -} {- $OpenSSL::safe::opt_engine_item -} {- $OpenSSL::safe::opt_provider_item -} {- $OpenSSL::safe::opt_v_item -} If the server requests a client certificate, then verification errors are displayed, for debugging, but the command will proceed unless the B<-verify_return_error> option is used. =back =head1 CONNECTED COMMANDS If a connection request is established with an SSL client and neither the B<-www> nor the B<-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. =over 4 =item B End the current SSL connection but still accept new connections. =item B End the current SSL connection and exit. =item B Renegotiate the SSL session (TLSv1.2 and below only). =item B Renegotiate the SSL session and request a client certificate (TLSv1.2 and below only). =item B

Send some plain text down the underlying TCP connection: this should cause the client to disconnect due to a protocol violation. =item B Print out some session cache status information. =item B Send a key update message to the client (TLSv1.3 only) =item B Send a key update message to the client and request one back (TLSv1.3 only) =item B Send a certificate request to the client (TLSv1.3 only) =back =head1 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 certificate 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 L command. =head1 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. =head1 SEE ALSO L, L, L, L, L, L, L, L, L =head1 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. All B<-keyform> and B<-dkeyform> values except B have become obsolete in OpenSSL 3.0.0 and have no effect. The B<-certform> and B<-dcertform> options have become obsolete in OpenSSL 3.0.0 and have no effect. =head1 COPYRIGHT Copyright 2000-2020 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 L. =cut