S_SERVER(1) OpenSSL S_SERVER(1) NNAAMMEE openssl-s_server, s_server - SSL/TLS server program SSYYNNOOPPSSIISS ooppeennssssll ss__sseerrvveerr [--aacccceepptt ppoorrtt] [--ccoonntteexxtt iidd] [--vveerriiffyy ddeepptthh] [--VVeerriiffyy ddeepptthh] [--ccrrll__cchheecckk] [--ccrrll__cchheecckk__aallll] [--cceerrtt ffiilleennaammee] [--cceerrttffoorrmm DDEERR||PPEEMM] [--kkeeyy kkeeyyffiillee] [--kkeeyyffoorrmm DDEERR||PPEEMM] [--ppaassss aarrgg] [--ddcceerrtt ffiillee-- nnaammee] [--ddcceerrttffoorrmm DDEERR||PPEEMM] [--ddkkeeyy kkeeyyffiillee] [--ddkkeeyyffoorrmm DDEERR||PPEEMM] [--ddppaassss aarrgg] [--ddhhppaarraamm ffiilleennaammee] [--nnbbiioo] [--nnbbiioo__tteesstt] [--ccrrllff] [--ddeebbuugg] [--mmssgg] [--ssttaattee] [--CCAAppaatthh ddiirreeccttoorryy] [--CCAAffiillee ffiilleennaammee] [--nnoo__aalltt__cchhaaiinnss] [--nnoocceerrtt] [--cclliieenntt__ssiiggaallggss ssiiggaallgglliisstt] [--nnaammeedd__ccuurrvvee ccuurrvvee] [--cciipphheerr cciipphheerrlliisstt] [--sseerrvveerrpprreeff] [--qquuiieett] [--nnoo__ttmmpp__rrssaa] [--ssssll22] [--ssssll33] [--ttllss11] [--nnoo__ssssll22] [--nnoo__ssssll33] [--nnoo__ttllss11] [--nnoo__ddhhee] [--nnoo__eeccddhhee] [--bbuuggss] [--hhaacckk] [--wwwwww] [--WWWWWW] [--HHTTTTPP] [--eennggiinnee iidd] [--ttllsseexxttddeebbuugg] [--nnoo__ttiicckkeett] [--iidd__pprreeffiixx aarrgg] [--rraanndd ffiillee((ss))] [--sseerrvveerriinnffoo ffiillee] [--nnoo__rreessuummpp-- ttiioonn__oonn__rreenneegg] [--ssttaattuuss] [--ssttaattuuss__vveerrbboossee] [--ssttaattuuss__ttiimmeeoouutt nnsseecc] [--ssttaattuuss__uurrll uurrll] [--aallppnn pprroottooccoollss] [--nneexxttpprroottoonneegg pprroottooccoollss] DDEESSCCRRIIPPTTIIOONN The ss__sseerrvveerr command implements a generic SSL/TLS server which listens for connections on a given port using SSL/TLS. OOPPTTIIOONNSS --aacccceepptt ppoorrtt the TCP port to listen on for connections. If not specified 4433 is used. --ccoonntteexxtt iidd sets the SSL context id. It can be given any string value. If this option is not present a default value will be used. --cceerrtt cceerrttnnaammee The certificate to use, most servers cipher suites require the use of a certificate and some require a certificate with a certain pub- lic key type: for example the DSS cipher suites require a certifi- cate containing a DSS (DSA) key. If not specified then the filename "server.pem" will be used. --cceerrttffoorrmm ffoorrmmaatt The certificate format to use: DER or PEM. PEM is the default. --kkeeyy kkeeyyffiillee The private key to use. If not specified then the certificate file will be used. --kkeeyyffoorrmm ffoorrmmaatt The private format to use: DER or PEM. PEM is the default. --ppaassss aarrgg the private key password source. For more information about the format of aarrgg see the PPAASSSS PPHHRRAASSEE AARRGGUUMMEENNTTSS section in _o_p_e_n_s_s_l(1). --ddcceerrtt ffiilleennaammee, --ddkkeeyy kkeeyynnaammee specify an additional certificate and private key, these behave in the same manner as the --cceerrtt and --kkeeyy 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 certifi- cate 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. --ddcceerrttffoorrmm ffoorrmmaatt, --ddkkeeyyffoorrmm ffoorrmmaatt, --ddppaassss aarrgg additional certificate and private key format and passphrase respectively. --nnoocceerrtt if this option is set then no certificate is used. This restricts the cipher suites available to the anonymous ones (currently just anonymous DH). --ddhhppaarraamm ffiilleennaammee the DH parameter file to use. The ephemeral DH cipher suites gener- ate 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 the s_server program will be used. --nnoo__ddhhee if this option is set then no DH parameters will be loaded effec- tively disabling the ephemeral DH cipher suites. --nnoo__eeccddhhee if this option is set then no ECDH parameters will be selected, effectively disabling the ephemeral ECDH cipher suites. --nnoo__ttmmpp__rrssaa certain export cipher suites sometimes use a temporary RSA key, this option disables temporary RSA key generation. --vveerriiffyy ddeepptthh, --VVeerriiffyy ddeepptthh 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 --vveerriiffyy option a certificate is requested but the client does not have to send one, with the --VVeerriiffyy option the client must supply a certificate or an error occurs. If the ciphersuite cannot request a client certificate (for example an anonymous ciphersuite or PSK) this option has no effect. --ccrrll__cchheecckk, --ccrrll__cchheecckk__aallll Check the peer certificate has not been revoked by its CA. The CRL(s) are appended to the certificate file. With the --ccrrll__cchheecckk__aallll option all CRLs of all CAs in the chain are checked. --CCAAppaatthh ddiirreeccttoorryy The directory to use for client certificate verification. This directory must be in "hash format", see vveerriiffyy for more informa- tion. These are also used when building the server certificate chain. --CCAAffiillee ffiillee A file containing trusted certificates to use during client authen- tication and to use when attempting to build the server certificate chain. The list is also used in the list of acceptable client CAs passed to the client when a certificate is requested. --nnoo__aalltt__cchhaaiinnss See the vveerriiffyy manual page for details. --ssttaattee prints out the SSL session states. --ddeebbuugg print extensive debugging information including a hex dump of all traffic. --mmssgg show all protocol messages with hex dump. --nnbbiioo__tteesstt tests non blocking I/O --nnbbiioo turns on non blocking I/O --ccrrllff this option translated a line feed from the terminal into CR+LF. --qquuiieett inhibit printing of session and certificate information. --ppsskk__hhiinntt hhiinntt Use the PSK identity hint hhiinntt when using a PSK cipher suite. --ppsskk kkeeyy Use the PSK key kkeeyy 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. --ssssll22, --ssssll33, --ttllss11, --ttllss11__11, --ttllss11__22, --nnoo__ssssll22, --nnoo__ssssll33, --nnoo__ttllss11, --nnoo__ttllss11__11, --nnoo__ttllss11__22 These options require or disable the use of the specified SSL or TLS protocols. By default the initial handshake uses a _v_e_r_s_i_o_n_- _f_l_e_x_i_b_l_e method which will negotiate the highest mutually supported protocol version. --bbuuggss there are several known bug in SSL and TLS implementations. Adding this option enables various workarounds. --hhaacckk this option enables a further workaround for some some early Net- scape SSL code (?). --cclliieenntt__ssiiggaallggss ssiiggaallgglliisstt Signature algorithms to support for client certificate authentica- tion (colon-separated list) --nnaammeedd__ccuurrvvee ccuurrvvee 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 --cciipphheerr cciipphheerrlliisstt this allows the cipher list used by the server to be modified. 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 irrelevant. See the cciipphheerrss command for more information. --sseerrvveerrpprreeff use the server's cipher preferences, rather than the client's pref- erences. --ttllsseexxttddeebbuugg print out a hex dump of any TLS extensions received from the server. --nnoo__ttiicckkeett disable RFC4507bis session ticket support. --wwwwww sends a status message back to the client when it connects. This includes lots of information about the ciphers used and various session parameters. The output is in HTML format so this option will normally be used with a web browser. --WWWWWW 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 loaded. --HHTTTTPP 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 loaded. The files loaded are assumed to contain a complete and cor- rect HTTP response (lines that are part of the HTTP response line and headers must end with CRLF). --eennggiinnee iidd specifying an engine (by its unique iidd string) will cause ss__sseerrvveerr to attempt to obtain a functional reference to the specified engine, thus initialising it if needed. The engine will then be set as the default for all available algorithms. --iidd__pprreeffiixx aarrgg generate SSL/TLS session IDs prefixed by aarrgg. 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). --rraanndd ffiillee((ss)) a file or files containing random data used to seed the random num- ber generator, or an EGD socket (see _R_A_N_D___e_g_d(3)). Multiple files can be specified separated by a OS-dependent character. The sepa- rator is ;; for MS-Windows, ,, for OpenVMS, and :: for all others. --sseerrvveerriinnffoo ffiillee 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. --nnoo__rreessuummppttiioonn__oonn__rreenneegg set SSL_OP_NO_SESSION_RESUMPTION_ON_RENEGOTIATION flag. --ssttaattuuss enables certificate status request support (aka OCSP stapling). --ssttaattuuss__vveerrbboossee enables certificate status request support (aka OCSP stapling) and gives a verbose printout of the OCSP response. --ssttaattuuss__ttiimmeeoouutt nnsseecc sets the timeout for OCSP response to nnsseecc seconds. --ssttaattuuss__uurrll uurrll 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. --aallppnn pprroottooccoollss, --nneexxttpprroottoonneegg pprroottooccoollss these flags enable the Enable the Application-Layer Protocol Nego- tiation or Next Protocol Negotiation extension, respectively. ALPN is the IETF standard and replaces NPN. The pprroottooccoollss list is a comma-separated list of supported protocol names. The list should contain most wanted protocols first. Protocol names are printable ASCII strings, for example "http/1.1" or "spdy/3". CCOONNNNEECCTTEEDD CCOOMMMMAANNDDSS If a connection request is established with an SSL client and neither the --wwwwww nor the --WWWWWW 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 single letter commands are also recognized which perform spe- cial operations: these are listed below. qq end the current SSL connection but still accept new connections. QQ end the current SSL connection and exit. rr renegotiate the SSL session. RR renegotiate the SSL session and request a client certificate. PP send some plain text down the underlying TCP connection: this should cause the client to disconnect due to a protocol violation. SS print out some session cache status information. NNOOTTEESS ss__sseerrvveerr 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 cer- tificate is strictly speaking a protocol violation, some SSL clients interpret this to mean any CA is acceptable. This is useful for debug- ging purposes. The session parameters can printed out using the sseessss__iidd program. BBUUGGSS Because this program has a lot of options and also because some of the techniques used are rather old, the C source of s_server 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 the ss__sseerrvveerr program to print out details of any unknown cipher suites a client says it supports. SSEEEE AALLSSOO _s_e_s_s___i_d(1), _s___c_l_i_e_n_t(1), _c_i_p_h_e_r_s(1) HHIISSTTOORRYY The -no_alt_chains options was first added to OpenSSL 1.0.2b. 1.0.2u 2019-12-20 S_SERVER(1)