{ "mode": "man", "parameter": "OPENSSL-S_CLIENT", "section": "1SSL", "url": "https://www.chedong.com/phpMan.php/man/OPENSSL-S_CLIENT/1SSL/json", "generated": "2026-06-28T02:40:30Z", "synopsis": "openssl sclient [-help] [-sslconfig section] [-connect host:port] [-host hostname] [-port\nport] [-bind host:port] [-proxy host:port] [-proxyuser userid] [-proxypass arg] [-unix\npath] [-4] [-6] [-servername name] [-noservername] [-verify depth] [-verifyreturnerror]\n[-verifyquiet] [-verifyCAfile filename] [-verifyCApath dir] [-verifyCAstore uri] [-cert\nfilename] [-certform DER|PEM|P12] [-certchain filename] [-buildchain] [-CRL filename]\n[-CRLform DER|PEM] [-crldownload] [-key filename|uri] [-keyform DER|PEM|P12|ENGINE] [-pass\narg] [-chainCAfile filename] [-chainCApath directory] [-chainCAstore uri] [-requestCAfile\nfilename] [-danetlsadomain domain] [-danetlsarrdata rrdata] [-daneeenonamechecks]\n[-reconnect] [-showcerts] [-prexit] [-debug] [-trace] [-nocommands] [-securitydebug]\n[-securitydebugverbose] [-msg] [-timeout] [-mtu size] [-noetm] [-keymatexport label]\n[-keymatexportlen len] [-msgfile filename] [-nbiotest] [-state] [-nbio] [-crlf] [-igneof]\n[-noigneof] [-pskidentity identity] [-psk key] [-psksession file] [-quiet] [-sctp]\n[-sctplabelbug] [-fallbackscsv] [-async] [-maxfraglen len] [-maxsendfrag]\n[-splitsendfrag] [-maxpipelines] [-readbuf] [-ignoreunexpectedeof] [-bugs] [-comp]\n[-nocomp] [-brief] [-legacyserverconnect] [-allownodhekex] [-sigalgs sigalglist]\n[-curves curvelist] [-cipher cipherlist] [-ciphersuites val] [-serverpref] [-starttls\nprotocol] [-name hostname] [-xmpphost hostname] [-name hostname] [-tlsextdebug] [-noticket]\n[-sessout filename] [-serverinfo types] [-sessin filename] [-serverinfo types] [-status]\n[-alpn protocols] [-nextprotoneg protocols] [-ct] [-noct] [-ctlogfile] [-keylogfile file]\n[-earlydata file] [-enablepha] [-usesrtp value] [-srpuser value] [-srppass value]\n[-srplateuser] [-srpmoregroups] [-srpstrength number] [-nameopt option] [-nossl3]\n[-notls1] [-notls11] [-notls12] [-notls13] [-ssl3] [-tls1] [-tls11] [-tls12]\n[-tls13] [-dtls] [-dtls1] [-dtls12] [-xkey infile] [-xcert file] [-xchain file]\n[-xchainbuild file] [-xcertform DER|PEM]> [-xkeyform DER|PEM]> [-CAfile file] [-no-CAfile]\n[-CApath dir] [-no-CApath] [-CAstore uri] [-no-CAstore] [-bugs] [-nocomp] [-comp]\n[-noticket] [-serverpref] [-clientrenegotiation] [-legacyrenegotiation]\n[-norenegotiation] [-noresumptiononreneg] [-legacyserverconnect]\n[-nolegacyserverconnect] [-noetm] [-allownodhekex] [-prioritizechacha] [-strict]\n[-sigalgs algs] [-clientsigalgs algs] [-groups groups] [-curves curves] [-namedcurve curve]\n[-cipher ciphers] [-ciphersuites 1.3ciphers] [-minprotocol minprot] [-maxprotocol maxprot]\n[-recordpadding padding] [-debugbrokenprotocol] [-nomiddlebox] [-rand files] [-writerand\nfile] [-provider name] [-provider-path path] [-propquery propq] [-engine id]\n[-sslclientengine id] [-allowproxycerts] [-attime timestamp] [-nochecktime]\n[-checksssig] [-crlcheck] [-crlcheckall] [-explicitpolicy] [-extendedcrl]\n[-ignorecritical] [-inhibitany] [-inhibitmap] [-partialchain] [-policy arg]\n[-policycheck] [-policyprint] [-purpose purpose] [-suiteB128] [-suiteB128only]\n[-suiteB192] [-trustedfirst] [-noaltchains] [-usedeltas] [-authlevel num]\n[-verifydepth num] [-verifyemail email] [-verifyhostname hostname] [-verifyip ip]\n[-verifyname name] [-x509strict] [-issuerchecks] [host:port]", "sections": { "NAME": { "content": "openssl-sclient - SSL/TLS client program\n", "subsections": [] }, "SYNOPSIS": { "content": "openssl sclient [-help] [-sslconfig section] [-connect host:port] [-host hostname] [-port\nport] [-bind host:port] [-proxy host:port] [-proxyuser userid] [-proxypass arg] [-unix\npath] [-4] [-6] [-servername name] [-noservername] [-verify depth] [-verifyreturnerror]\n[-verifyquiet] [-verifyCAfile filename] [-verifyCApath dir] [-verifyCAstore uri] [-cert\nfilename] [-certform DER|PEM|P12] [-certchain filename] [-buildchain] [-CRL filename]\n[-CRLform DER|PEM] [-crldownload] [-key filename|uri] [-keyform DER|PEM|P12|ENGINE] [-pass\narg] [-chainCAfile filename] [-chainCApath directory] [-chainCAstore uri] [-requestCAfile\nfilename] [-danetlsadomain domain] [-danetlsarrdata rrdata] [-daneeenonamechecks]\n[-reconnect] [-showcerts] [-prexit] [-debug] [-trace] [-nocommands] [-securitydebug]\n[-securitydebugverbose] [-msg] [-timeout] [-mtu size] [-noetm] [-keymatexport label]\n[-keymatexportlen len] [-msgfile filename] [-nbiotest] [-state] [-nbio] [-crlf] [-igneof]\n[-noigneof] [-pskidentity identity] [-psk key] [-psksession file] [-quiet] [-sctp]\n[-sctplabelbug] [-fallbackscsv] [-async] [-maxfraglen len] [-maxsendfrag]\n[-splitsendfrag] [-maxpipelines] [-readbuf] [-ignoreunexpectedeof] [-bugs] [-comp]\n[-nocomp] [-brief] [-legacyserverconnect] [-allownodhekex] [-sigalgs sigalglist]\n[-curves curvelist] [-cipher cipherlist] [-ciphersuites val] [-serverpref] [-starttls\nprotocol] [-name hostname] [-xmpphost hostname] [-name hostname] [-tlsextdebug] [-noticket]\n[-sessout filename] [-serverinfo types] [-sessin filename] [-serverinfo types] [-status]\n[-alpn protocols] [-nextprotoneg protocols] [-ct] [-noct] [-ctlogfile] [-keylogfile file]\n[-earlydata file] [-enablepha] [-usesrtp value] [-srpuser value] [-srppass value]\n[-srplateuser] [-srpmoregroups] [-srpstrength number] [-nameopt option] [-nossl3]\n[-notls1] [-notls11] [-notls12] [-notls13] [-ssl3] [-tls1] [-tls11] [-tls12]\n[-tls13] [-dtls] [-dtls1] [-dtls12] [-xkey infile] [-xcert file] [-xchain file]\n[-xchainbuild file] [-xcertform DER|PEM]> [-xkeyform DER|PEM]> [-CAfile file] [-no-CAfile]\n[-CApath dir] [-no-CApath] [-CAstore uri] [-no-CAstore] [-bugs] [-nocomp] [-comp]\n[-noticket] [-serverpref] [-clientrenegotiation] [-legacyrenegotiation]\n[-norenegotiation] [-noresumptiononreneg] [-legacyserverconnect]\n[-nolegacyserverconnect] [-noetm] [-allownodhekex] [-prioritizechacha] [-strict]\n[-sigalgs algs] [-clientsigalgs algs] [-groups groups] [-curves curves] [-namedcurve curve]\n[-cipher ciphers] [-ciphersuites 1.3ciphers] [-minprotocol minprot] [-maxprotocol maxprot]\n[-recordpadding padding] [-debugbrokenprotocol] [-nomiddlebox] [-rand files] [-writerand\nfile] [-provider name] [-provider-path path] [-propquery propq] [-engine id]\n[-sslclientengine id] [-allowproxycerts] [-attime timestamp] [-nochecktime]\n[-checksssig] [-crlcheck] [-crlcheckall] [-explicitpolicy] [-extendedcrl]\n[-ignorecritical] [-inhibitany] [-inhibitmap] [-partialchain] [-policy arg]\n[-policycheck] [-policyprint] [-purpose purpose] [-suiteB128] [-suiteB128only]\n[-suiteB192] [-trustedfirst] [-noaltchains] [-usedeltas] [-authlevel num]\n[-verifydepth num] [-verifyemail email] [-verifyhostname hostname] [-verifyip ip]\n[-verifyname name] [-x509strict] [-issuerchecks] [host:port]\n", "subsections": [] }, "DESCRIPTION": { "content": "This command implements a generic SSL/TLS client which connects to a remote host using\nSSL/TLS. It is a very useful diagnostic tool for SSL servers.\n", "subsections": [] }, "OPTIONS": { "content": "In addition to the options below, this command also supports the common and client only\noptions documented in the \"Supported Command Line Commands\" section of the SSLCONFcmd(3)\nmanual page.\n", "subsections": [ { "name": "-help", "content": "Print out a usage message.\n" }, { "name": "-ssl", "content": "Use the specified section of the configuration file to configure the SSLCTX object.\n" }, { "name": "-connect", "content": "This specifies the host and optional port to connect to. It is possible to select the\nhost and port using the optional target positional argument instead. If neither this nor\nthe target positional argument are specified then an attempt is made to connect to the\nlocal host on port 4433.\n" }, { "name": "-host", "content": "Host to connect to; use -connect instead.\n" }, { "name": "-port", "content": "Connect to the specified port; use -connect instead.\n" }, { "name": "-bind", "content": "This specifies the host address and or port to bind as the source for the connection.\nFor Unix-domain sockets the port is ignored and the host is used as the source socket\naddress.\n" }, { "name": "-proxy", "content": "When used with the -connect flag, the program uses the host and port specified with this\nflag and issues an HTTP CONNECT command to connect to the desired server.\n" }, { "name": "-proxy", "content": "When used with the -proxy flag, the program will attempt to authenticate with the\nspecified proxy using basic (base64) authentication. NB: Basic authentication is\ninsecure; the credentials are sent to the proxy in easily reversible base64 encoding\nbefore any TLS/SSL session is established. Therefore, these credentials are easily\nrecovered by anyone able to sniff/trace the network. Use with caution.\n" }, { "name": "-proxy", "content": "The proxy password source, used with the -proxyuser flag. For more information about\nthe format of arg see openssl-passphrase-options(1).\n" }, { "name": "-unix", "content": "Connect over the specified Unix-domain socket.\n" }, { "name": "-4", "content": "", "flag": "-4" }, { "name": "-6", "content": "", "flag": "-6" }, { "name": "-servername", "content": "Set the TLS SNI (Server Name Indication) extension in the ClientHello message to the\ngiven value. If -servername is not provided, the TLS SNI extension will be populated\nwith the name given to -connect if it follows a DNS name format. If -connect is not\nprovided either, the SNI is set to \"localhost\". This is the default since OpenSSL 1.1.1.\n\nEven though SNI should normally be a DNS name and not an IP address, if -servername is\nprovided then that name will be sent, regardless of whether it is a DNS name or not.\n\nThis option cannot be used in conjunction with -noservername.\n" }, { "name": "-noservername", "content": "Suppresses sending of the SNI (Server Name Indication) extension in the ClientHello\nmessage. Cannot be used in conjunction with the -servername or -danetlsadomain options.\n" }, { "name": "-cert", "content": "The client certificate to use, if one is requested by the server. The default is not to\nuse a certificate.\n\nThe chain for the client certificate may be specified using -certchain.\n" }, { "name": "-certform", "content": "The client certificate file format to use; unspecified by default. See\nopenssl-format-options(1) for details.\n" }, { "name": "-cert", "content": "A file or URI of untrusted certificates to use when attempting to build the certificate\nchain related to the certificate specified via the -cert option. The input can be in\nPEM, DER, or PKCS#12 format.\n" }, { "name": "-build", "content": "Specify whether the application should build the client certificate chain to be provided\nto the server.\n" }, { "name": "-CRL", "content": "CRL file to use to check the server's certificate.\n" }, { "name": "-CRLform", "content": "The CRL file format; unspecified by default. See openssl-format-options(1) for details.\n" }, { "name": "-crl", "content": "Download CRL from distribution points in the certificate.\n" }, { "name": "-key", "content": "The client private key to use. If not specified then the certificate file will be used\nto read also the key.\n" }, { "name": "-keyform", "content": "The key format; unspecified by default. See openssl-format-options(1) for details.\n" }, { "name": "-pass", "content": "the private key and certifiate file password source. For more information about the\nformat of arg see openssl-passphrase-options(1).\n" }, { "name": "-verify", "content": "The verify depth to use. This specifies the maximum length of the server certificate\nchain and turns on server certificate verification. Currently the verify operation\ncontinues after errors so all the problems with a certificate chain can be seen. As a\nside effect the connection will never fail due to a server certificate verify failure.\n" }, { "name": "-verify", "content": "Return verification errors instead of continuing. This will typically abort the handshake\nwith a fatal error.\n" }, { "name": "-verify", "content": "Limit verify output to only errors.\n" }, { "name": "-verifyCAfile", "content": "A file in PEM format containing trusted certificates to use for verifying the server's\ncertificate.\n" }, { "name": "-verifyCApath", "content": "A directory containing trusted certificates to use for verifying the server's\ncertificate. This directory must be in \"hash format\", see openssl-verify(1) for more\ninformation.\n" }, { "name": "-verifyCAstore", "content": "The URI of a store containing trusted certificates to use for verifying the server's\ncertificate.\n" }, { "name": "-chainCAfile", "content": "A file in PEM format containing trusted certificates to use when attempting to build the\nclient certificate chain.\n" }, { "name": "-chainCApath", "content": "A directory containing trusted certificates to use for building the client certificate\nchain provided to the server. This directory must be in \"hash format\", see\nopenssl-verify(1) for more information.\n" }, { "name": "-chainCAstore", "content": "The URI of a store containing trusted certificates to use when attempting to build the\nclient certificate chain. The URI may indicate a single certificate, as well as a\ncollection of them. With URIs in the \"file:\" scheme, this acts as -chainCAfile or\n-chainCApath, depending on if the URI indicates a directory or a single file. See\nosslstore-file(7) for more information on the \"file:\" scheme.\n" }, { "name": "-requestCAfile", "content": "A file containing a list of certificates whose subject names will be sent to the server\nin the certificateauthorities extension. Only supported for TLS 1.3\n" }, { "name": "-dane", "content": "Enable RFC6698/RFC7671 DANE TLSA authentication and specify the TLSA base domain which\nbecomes the default SNI hint and the primary reference identifier for hostname checks.\nThis must be used in combination with at least one instance of the -danetlsarrdata\noption below.\n\nWhen DANE authentication succeeds, the diagnostic output will include the lowest (closest\nto 0) depth at which a TLSA record authenticated a chain certificate. When that TLSA\nrecord is a \"2 1 0\" trust anchor public key that signed (rather than matched) the top-\nmost certificate of the chain, the result is reported as \"TA public key verified\".\nOtherwise, either the TLSA record \"matched TA certificate\" at a positive depth or else\n\"matched EE certificate\" at depth 0.\n" }, { "name": "-dane", "content": "Use one or more times to specify the RRDATA fields of the DANE TLSA RRset associated with\nthe target service. The rrdata value is specified in \"presentation form\", that is four\nwhitespace separated fields that specify the usage, selector, matching type and\nassociated data, with the last of these encoded in hexadecimal. Optional whitespace is\nignored in the associated data field. For example:\n\n$ openssl sclient -brief -starttls smtp \\\n-connect smtp.example.com:25 \\\n-danetlsadomain smtp.example.com \\\n-danetlsarrdata \"2 1 1\nB111DD8A1C2091A89BD4FD60C57F0716CCE50FEEFF8137CDBEE0326E 02CF362B\" \\\n-danetlsarrdata \"2 1 1\n60B87575447DCBA2A36B7D11AC09FB24A9DB406FEE12D2CC90180517 616E8A18\"\n...\nVerification: OK\nVerified peername: smtp.example.com\nDANE TLSA 2 1 1 ...ee12d2cc90180517616e8a18 matched TA certificate at depth 1\n...\n" }, { "name": "-dane", "content": "This disables server name checks when authenticating via DANE-EE(3) TLSA records. For\nsome applications, primarily web browsers, it is not safe to disable name checks due to\n\"unknown key share\" attacks, in which a malicious server can convince a client that a\nconnection to a victim server is instead a secure connection to the malicious server.\nThe malicious server may then be able to violate cross-origin scripting restrictions.\nThus, despite the text of RFC7671, name checks are by default enabled for DANE-EE(3) TLSA\nrecords, and can be disabled in applications where it is safe to do so. In particular,\nSMTP and XMPP clients should set this option as SRV and MX records already make it\npossible for a remote domain to redirect client connections to any server of its choice,\nand in any case SMTP and XMPP clients do not execute scripts downloaded from remote\nservers.\n" }, { "name": "-reconnect", "content": "Reconnects to the same server 5 times using the same session ID, this can be used as a\ntest that session caching is working.\n" }, { "name": "-showcerts", "content": "Displays the server certificate list as sent by the server: it only consists of\ncertificates the server has sent (in the order the server has sent them). It is not a\nverified chain.\n" }, { "name": "-prexit", "content": "Print session information when the program exits. This will always attempt to print out\ninformation even if the connection fails. Normally information will only be printed out\nonce if the connection succeeds. This option is useful because the cipher in use may be\nrenegotiated or the connection may fail because a client certificate is required or is\nrequested only after an attempt is made to access a certain URL. Note: the output\nproduced by this option is not always accurate because a connection might never have been\nestablished.\n" }, { "name": "-state", "content": "Prints out the SSL session states.\n" }, { "name": "-debug", "content": "Print extensive debugging information including a hex dump of all traffic.\n" }, { "name": "-nocommands", "content": "Do not use interactive command letters.\n" }, { "name": "-security", "content": "Enable security debug messages.\n" }, { "name": "-security", "content": "Output more security debug output.\n" }, { "name": "-msg", "content": "Show protocol messages.\n" }, { "name": "-timeout", "content": "Enable send/receive timeout on DTLS connections.\n" }, { "name": "-mtu", "content": "Set MTU of the link layer to the specified size.\n" }, { "name": "-no", "content": "Disable Encrypt-then-MAC negotiation.\n" }, { "name": "-keymatexport", "content": "Export keying material using the specified label.\n" }, { "name": "-keymatexportlen", "content": "Export the specified number of bytes of keying material; default is 20.\n\nShow all protocol messages with hex dump.\n" }, { "name": "-trace", "content": "Show verbose trace output of protocol messages.\n" }, { "name": "-msgfile", "content": "File to send output of -msg or -trace to, default standard output.\n" }, { "name": "-nbio", "content": "Tests nonblocking I/O\n" }, { "name": "-nbio", "content": "Turns on nonblocking I/O\n" }, { "name": "-crlf", "content": "This option translated a line feed from the terminal into CR+LF as required by some\nservers.\n" }, { "name": "-ign", "content": "Inhibit shutting down the connection when end of file is reached in the input.\n" }, { "name": "-quiet", "content": "Inhibit printing of session and certificate information. This implicitly turns on\n-igneof as well.\n" }, { "name": "-no", "content": "Shut down the connection when end of file is reached in the input. Can be used to\noverride the implicit -igneof after -quiet.\n" }, { "name": "-psk", "content": "Use the PSK identity identity when using a PSK cipher suite. The default value is\n\"Clientidentity\" (without the quotes).\n" }, { "name": "-psk", "content": "Use the PSK key key when using a PSK cipher suite. The key is given as a hexadecimal\nnumber without leading 0x, for example -psk 1a2b3c4d. This option must be provided in\norder to use a PSK cipher.\n" }, { "name": "-psk", "content": "Use the pem encoded SSLSESSION data stored in file as the basis of a PSK. Note that\nthis will only work if TLSv1.3 is negotiated.\n" }, { "name": "-sctp", "content": "Use SCTP for the transport protocol instead of UDP in DTLS. Must be used in conjunction\nwith -dtls, -dtls1 or -dtls12. This option is only available where OpenSSL has support\nfor SCTP enabled.\n" }, { "name": "-sctp", "content": "Use the incorrect behaviour of older OpenSSL implementations when computing endpoint-pair\nshared secrets for DTLS/SCTP. This allows communication with older broken implementations\nbut breaks interoperability with correct implementations. Must be used in conjunction\nwith -sctp. This option is only available where OpenSSL has support for SCTP enabled.\n" }, { "name": "-fallback", "content": "Send TLSFALLBACKSCSV in the ClientHello.\n" }, { "name": "-async", "content": "Switch on asynchronous mode. Cryptographic operations will be performed asynchronously.\nThis will only have an effect if an asynchronous capable engine is also used via the\n-engine option. For test purposes the dummy async engine (dasync) can be used (if\navailable).\n" }, { "name": "-maxfraglen", "content": "Enable Maximum Fragment Length Negotiation; allowed values are 512, 1024, 2048, and 4096.\n" }, { "name": "-max", "content": "The maximum size of data fragment to send. See SSLCTXsetmaxsendfragment(3) for\nfurther information.\n" }, { "name": "-split", "content": "The size used to split data for encrypt pipelines. If more data is written in one go than\nthis value then it will be split into multiple pipelines, up to the maximum number of\npipelines defined by maxpipelines. This only has an effect if a suitable cipher suite\nhas been negotiated, an engine that supports pipelining has been loaded, and\nmaxpipelines is greater than 1. See SSLCTXsetsplitsendfragment(3) for further\ninformation.\n" }, { "name": "-max", "content": "The maximum number of encrypt/decrypt pipelines to be used. This will only have an effect\nif an engine has been loaded that supports pipelining (e.g. the dasync engine) and a\nsuitable cipher suite has been negotiated. The default value is 1. See\nSSLCTXsetmaxpipelines(3) for further information.\n" }, { "name": "-read", "content": "The default read buffer size to be used for connections. This will only have an effect if\nthe buffer size is larger than the size that would otherwise be used and pipelining is in\nuse (see SSLCTXsetdefaultreadbufferlen(3) for further information).\n" }, { "name": "-ignore", "content": "Some TLS implementations do not send the mandatory closenotify alert on shutdown. If the\napplication tries to wait for the closenotify alert but the peer closes the connection\nwithout sending it, an error is generated. When this option is enabled the peer does not\nneed to send the closenotify alert and a closed connection will be treated as if the\nclosenotify alert was received. For more information on shutting down a connection, see\nSSLshutdown(3).\n" }, { "name": "-bugs", "content": "There are several known bugs in SSL and TLS implementations. Adding this option enables\nvarious workarounds.\n" }, { "name": "-comp", "content": "Enables support for SSL/TLS compression. This option was introduced in OpenSSL 1.1.0.\nTLS compression is not recommended and is off by default as of OpenSSL 1.1.0.\n" }, { "name": "-no", "content": "Disables support for SSL/TLS compression. TLS compression is not recommended and is off\nby default as of OpenSSL 1.1.0.\n" }, { "name": "-brief", "content": "Only provide a brief summary of connection parameters instead of the normal verbose\noutput.\n" }, { "name": "-sigalgs", "content": "Specifies the list of signature algorithms that are sent by the client. The server\nselects one entry in the list based on its preferences. For example strings, see\nSSLCTXset1sigalgs(3)\n" }, { "name": "-curves", "content": "Specifies the list of supported curves to be sent by the client. The curve is ultimately\nselected by the server. For a list of all curves, use:\n\n$ openssl ecparam -listcurves\n" }, { "name": "-cipher", "content": "This allows the TLSv1.2 and below cipher list sent by the client to be modified. This\nlist will be combined with any TLSv1.3 ciphersuites that have been configured. Although\nthe server determines which ciphersuite is used it should take the first supported cipher\nin the list sent by the client. See openssl-ciphers(1) for more information.\n" }, { "name": "-ciphersuites", "content": "This allows the TLSv1.3 ciphersuites sent by the client to be modified. This list will be\ncombined with any TLSv1.2 and below ciphersuites that have been configured. Although the\nserver determines which cipher suite is used it should take the first supported cipher in\nthe list sent by the client. See openssl-ciphers(1) for more information. The format for\nthis list is a simple colon (\":\") separated list of TLSv1.3 ciphersuite names.\n" }, { "name": "-starttls", "content": "Send the protocol-specific message(s) to switch to TLS for communication. protocol is a\nkeyword for the intended protocol. Currently, the only supported keywords are \"smtp\",\n\"pop3\", \"imap\", \"ftp\", \"xmpp\", \"xmpp-server\", \"irc\", \"postgres\", \"mysql\", \"lmtp\", \"nntp\",\n\"sieve\" and \"ldap\".\n" }, { "name": "-xmpphost", "content": "This option, when used with \"-starttls xmpp\" or \"-starttls xmpp-server\", specifies the\nhost for the \"to\" attribute of the stream element. If this option is not specified, then\nthe host specified with \"-connect\" will be used.\n\nThis option is an alias of the -name option for \"xmpp\" and \"xmpp-server\".\n" }, { "name": "-name", "content": "This option is used to specify hostname information for various protocols used with\n-starttls option. Currently only \"xmpp\", \"xmpp-server\", \"smtp\" and \"lmtp\" can utilize\nthis -name option.\n\nIf this option is used with \"-starttls xmpp\" or \"-starttls xmpp-server\", if specifies the\nhost for the \"to\" attribute of the stream element. If this option is not specified, then\nthe host specified with \"-connect\" will be used.\n\nIf this option is used with \"-starttls lmtp\" or \"-starttls smtp\", it specifies the name\nto use in the \"LMTP LHLO\" or \"SMTP EHLO\" message, respectively. If this option is not\nspecified, then \"mail.example.com\" will be used.\n" }, { "name": "-tlsextdebug", "content": "Print out a hex dump of any TLS extensions received from the server.\n" }, { "name": "-no", "content": "Disable RFC4507bis session ticket support.\n" }, { "name": "-sess", "content": "Output SSL session to filename.\n" }, { "name": "-sess", "content": "Load SSL session from filename. The client will attempt to resume a connection from this\nsession.\n" }, { "name": "-serverinfo", "content": "A list of comma-separated TLS Extension Types (numbers between 0 and 65535). Each type\nwill be sent as an empty ClientHello TLS Extension. The server's response (if any) will\nbe encoded and displayed as a PEM file.\n" }, { "name": "-status", "content": "Sends a certificate status request to the server (OCSP stapling). The server response (if\nany) is printed out.\n" }, { "name": "-alpn -nextprotoneg", "content": "These flags enable the Enable the Application-Layer Protocol Negotiation or Next Protocol\nNegotiation (NPN) extension, respectively. ALPN is the IETF standard and replaces NPN.\nThe protocols list is a comma-separated list of protocol names that the client should\nadvertise support for. The list should contain the most desirable protocols first.\nProtocol names are printable ASCII strings, for example \"http/1.1\" or \"spdy/3\". An empty\nlist of protocols is treated specially and will cause the client to advertise support for\nthe TLS extension but disconnect just after receiving ServerHello with a list of server\nsupported protocols. The flag -nextprotoneg cannot be specified if -tls13 is used.\n" }, { "name": "-ct -noct", "content": "Use one of these two options to control whether Certificate Transparency (CT) is enabled\n(-ct) or disabled (-noct). If CT is enabled, signed certificate timestamps (SCTs) will\nbe requested from the server and reported at handshake completion.\n\nEnabling CT also enables OCSP stapling, as this is one possible delivery method for SCTs.\n" }, { "name": "-ctlogfile", "content": "A file containing a list of known Certificate Transparency logs. See\nSSLCTXsetctloglistfile(3) for the expected file format.\n" }, { "name": "-keylogfile", "content": "Appends TLS secrets to the specified keylog file such that external programs (like\nWireshark) can decrypt TLS connections.\n" }, { "name": "-early", "content": "Reads the contents of the specified file and attempts to send it as early data to the\nserver. This will only work with resumed sessions that support early data and when the\nserver accepts the early data.\n" }, { "name": "-enable", "content": "For TLSv1.3 only, send the Post-Handshake Authentication extension. This will happen\nwhether or not a certificate has been provided via -cert.\n" }, { "name": "-use", "content": "Offer SRTP key management, where value is a colon-separated profile list.\n" }, { "name": "-srpuser", "content": "Set the SRP username to the specified value. This option is deprecated.\n" }, { "name": "-srppass", "content": "Set the SRP password to the specified value. This option is deprecated.\n" }, { "name": "-srp", "content": "SRP username for the second ClientHello message. This option is deprecated.\n" }, { "name": "-srp", "content": "Tolerate other than the known g and N values.\n" }, { "name": "-srp", "content": "Set the minimal acceptable length, in bits, for N. This option is deprecated.\n" }, { "name": "-no -no -no -no -no -ssl3 -tls1 -tls1 -tls1", "content": "" }, { "name": "-tls1", "content": "See \"TLS Version Options\" in openssl(1).\n" }, { "name": "-dtls -dtls1 -dtls1", "content": "These specify the use of DTLS instead of TLS. See \"TLS Version Options\" in openssl(1).\n" }, { "name": "-nameopt", "content": "This specifies how the subject or issuer names are displayed. See\nopenssl-namedisplay-options(1) for details.\n" }, { "name": "-xkey -xcert -xchain -xchain -xcertform -xkeyform", "content": "DER|PEM\nSet extended certificate verification options. See \"Extended Verification Options\" in\nopenssl-verification-options(1) for details.\n" }, { "name": "-CAfile -no-CAfile -CApath -no-CApath -CAstore -no-CAstore", "content": "See \"Trusted Certificate Options\" in openssl-verification-options(1) for details.\n" }, { "name": "-bugs -comp -no -no -serverpref -client", "content": "" }, { "name": "-legacy -no -no -legacy", "content": "" }, { "name": "-no -no -allow -prioritize -strict -sigalgs", "content": "algs, -clientsigalgs algs, -groups groups, -curves curves, -namedcurve curve, -cipher\nciphers, -ciphersuites 1.3ciphers, -minprotocol minprot, -maxprotocol maxprot," }, { "name": "-record -debug -no", "content": "See \"SUPPORTED COMMAND LINE COMMANDS\" in SSLCONFcmd(3) for details.\n" }, { "name": "-rand -writerand", "content": "See \"Random State Options\" in openssl(1) for details.\n" }, { "name": "-provider", "content": "" }, { "name": "-provider-path", "content": "" }, { "name": "-propquery", "content": "See \"Provider Options\" in openssl(1), provider(7), and property(7).\n" }, { "name": "-engine", "content": "See \"Engine Options\" in openssl(1). This option is deprecated.\n" }, { "name": "-ssl", "content": "Specify engine to be used for client certificate operations.\n" }, { "name": "-allow -attime -no -check -crl -crl", "content": "" }, { "name": "-explicit -extended -ignore -inhibit -inhibit", "content": "" }, { "name": "-no -partial -policy -policy -policy -purpose -suiteB", "content": "" }, { "name": "-suiteB -suiteB -trusted -use -auth -verify", "content": "" }, { "name": "-verify -verify -verify -verify -x509 -issuer", "content": "Set various options of certificate chain verification. See \"Verification Options\" in\nopenssl-verification-options(1) for details.\n\nVerification errors are displayed, for debugging, but the command will proceed unless the\n-verifyreturnerror option is used.\n\nhost:port\nRather than providing -connect, the target hostname and optional port may be provided as\na single positional argument after all options. If neither this nor -connect are\nprovided, falls back to attempting to connect to localhost on port 4433.\n" } ] }, "CONNECTED COMMANDS": { "content": "If a connection is established with an SSL server then any data received from the server is\ndisplayed and any key presses will be sent to the server. If end of file is reached then the\nconnection will be closed down. When used interactively (which means neither -quiet nor", "subsections": [ { "name": "-ign", "content": "operations. These commands are a letter which must appear at the start of a line. They are\nlisted below.\n\nQ End the current SSL connection and exit.\n\nR Renegotiate the SSL session (TLSv1.2 and below only).\n\nk Send a key update message to the server (TLSv1.3 only)\n\nK Send a key update message to the server and request one back (TLSv1.3 only)\n" } ] }, "NOTES": { "content": "This command can be used to debug SSL servers. To connect to an SSL HTTP server the command:\n\nopenssl sclient -connect servername:443\n\nwould typically be used (https uses port 443). If the connection succeeds then an HTTP\ncommand can be given such as \"GET /\" to retrieve a web page.\n\nIf the handshake fails then there are several possible causes, if it is nothing obvious like\nno client certificate then the -bugs, -ssl3, -tls1, -nossl3, -notls1 options can be tried\nin case it is a buggy server. In particular you should play with these options before\nsubmitting a bug report to an OpenSSL mailing list.\n\nA frequent problem when attempting to get client certificates working is that a web client\ncomplains it has no certificates or gives an empty list to choose from. This is normally\nbecause the server is not sending the clients certificate authority in its \"acceptable CA\nlist\" when it requests a certificate. By using this command, the CA list can be viewed and\nchecked. However, some servers only request client authentication after a specific URL is\nrequested. To obtain the list in this case it is necessary to use the -prexit option and send\nan HTTP request for an appropriate page.\n\nIf a certificate is specified on the command line using the -cert option it will not be used\nunless the server specifically requests a client certificate. Therefore, merely including a\nclient certificate on the command line is no guarantee that the certificate works.\n\nIf there are problems verifying a server certificate then the -showcerts option can be used\nto show all the certificates sent by the server.\n\nThis command is a test tool and is designed to continue the handshake after any certificate\nverification errors. As a result it will accept any certificate chain (trusted or not) sent\nby the peer. Non-test applications should not do this as it makes them vulnerable to a MITM\nattack. This behaviour can be changed by with the -verifyreturnerror option: any verify\nerrors are then returned aborting the handshake.\n\nThe -bind option may be useful if the server or a firewall requires connections to come from\nsome particular address and or port.\n", "subsections": [] }, "BUGS": { "content": "Because this program has a lot of options and also because some of the techniques used are\nrather old, the C source for this command is rather hard to read and not a model of how\nthings should be done. A typical SSL client program would be much simpler.\n\nThe -prexit option is a bit of a hack. We should really report information whenever a session\nis renegotiated.\n", "subsections": [] }, "SEE ALSO": { "content": "openssl(1), openssl-sessid(1), openssl-sserver(1), openssl-ciphers(1), SSLCONFcmd(3),\nSSLCTXsetmaxsendfragment(3), SSLCTXsetsplitsendfragment(3),\nSSLCTXsetmaxpipelines(3), osslstore-file(7)\n", "subsections": [] }, "HISTORY": { "content": "The -noaltchains option was added in OpenSSL 1.1.0. The -name option was added in OpenSSL\n1.1.1.\n\nThe -certform option has become obsolete in OpenSSL 3.0.0 and has no effect.\n\nThe -engine option was deprecated in OpenSSL 3.0.\n", "subsections": [] }, "COPYRIGHT": { "content": "Copyright 2000-2021 The OpenSSL Project Authors. All Rights Reserved.\n\nLicensed under the Apache License 2.0 (the \"License\"). You may not use this file except in\ncompliance with the License. You can obtain a copy in the file LICENSE in the source\ndistribution or at .\n\n\n\n3.0.2 2026-06-02 OPENSSL-SCLIENT(1SSL)", "subsections": [] } }, "summary": "openssl-sclient - SSL/TLS client program", "flags": [ { "flag": "", "long": null, "arg": null, "description": "Print out a usage message." }, { "flag": "", "long": null, "arg": null, "description": "Use the specified section of the configuration file to configure the SSLCTX object." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "Host to connect to; use -connect instead." }, { "flag": "", "long": null, "arg": null, "description": "Connect to the specified port; use -connect instead." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "The proxy password source, used with the -proxyuser flag. For more information about the format of arg see openssl-passphrase-options(1)." }, { "flag": "", "long": null, "arg": null, "description": "Connect over the specified Unix-domain socket." }, { "flag": "-4", "long": null, "arg": null, "description": "" }, { "flag": "-6", "long": null, "arg": null, "description": "" }, { "flag": "", "long": null, "arg": null, "description": "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 1.1.1. 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 -noservername." }, { "flag": "", "long": null, "arg": null, "description": "Suppresses sending of the SNI (Server Name Indication) extension in the ClientHello message. Cannot be used in conjunction with the -servername or -danetlsadomain options." }, { "flag": "", "long": null, "arg": null, "description": "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 -certchain." }, { "flag": "", "long": null, "arg": null, "description": "The client certificate file format to use; unspecified by default. See openssl-format-options(1) for details." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "Specify whether the application should build the client certificate chain to be provided to the server." }, { "flag": "", "long": null, "arg": null, "description": "CRL file to use to check the server's certificate." }, { "flag": "", "long": null, "arg": null, "description": "The CRL file format; unspecified by default. See openssl-format-options(1) for details." }, { "flag": "", "long": null, "arg": null, "description": "Download CRL from distribution points in the certificate." }, { "flag": "", "long": null, "arg": null, "description": "The client private key to use. If not specified then the certificate file will be used to read also the key." }, { "flag": "", "long": null, "arg": null, "description": "The key format; unspecified by default. See openssl-format-options(1) for details." }, { "flag": "", "long": null, "arg": null, "description": "the private key and certifiate file password source. For more information about the format of arg see openssl-passphrase-options(1)." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "Return verification errors instead of continuing. This will typically abort the handshake with a fatal error." }, { "flag": "", "long": null, "arg": null, "description": "Limit verify output to only errors." }, { "flag": "", "long": null, "arg": null, "description": "A file in PEM format containing trusted certificates to use for verifying the server's certificate." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "The URI of a store containing trusted certificates to use for verifying the server's certificate." }, { "flag": "", "long": null, "arg": null, "description": "A file in PEM format containing trusted certificates to use when attempting to build the client certificate chain." }, { "flag": "", "long": null, "arg": null, "description": "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 information." }, { "flag": "", "long": null, "arg": null, "description": "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 osslstore-file(7) for more information on the \"file:\" scheme." }, { "flag": "", "long": null, "arg": null, "description": "A file containing a list of certificates whose subject names will be sent to the server in the certificateauthorities extension. Only supported for TLS 1.3" }, { "flag": "", "long": null, "arg": null, "description": "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 -danetlsarrdata 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." }, { "flag": "", "long": null, "arg": null, "description": "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 sclient -brief -starttls smtp \\ -connect smtp.example.com:25 \\ -danetlsadomain smtp.example.com \\ -danetlsarrdata \"2 1 1 B111DD8A1C2091A89BD4FD60C57F0716CCE50FEEFF8137CDBEE0326E 02CF362B\" \\ -danetlsarrdata \"2 1 1 60B87575447DCBA2A36B7D11AC09FB24A9DB406FEE12D2CC90180517 616E8A18\" ... Verification: OK Verified peername: smtp.example.com DANE TLSA 2 1 1 ...ee12d2cc90180517616e8a18 matched TA certificate at depth 1 ..." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "Reconnects to the same server 5 times using the same session ID, this can be used as a test that session caching is working." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "Prints out the SSL session states." }, { "flag": "", "long": null, "arg": null, "description": "Print extensive debugging information including a hex dump of all traffic." }, { "flag": "", "long": null, "arg": null, "description": "Do not use interactive command letters." }, { "flag": "", "long": null, "arg": null, "description": "Enable security debug messages." }, { "flag": "", "long": null, "arg": null, "description": "Output more security debug output." }, { "flag": "", "long": null, "arg": null, "description": "Show protocol messages." }, { "flag": "", "long": null, "arg": null, "description": "Enable send/receive timeout on DTLS connections." }, { "flag": "", "long": null, "arg": null, "description": "Set MTU of the link layer to the specified size." }, { "flag": "", "long": null, "arg": null, "description": "Disable Encrypt-then-MAC negotiation." }, { "flag": "", "long": null, "arg": null, "description": "Export keying material using the specified label." }, { "flag": "", "long": null, "arg": null, "description": "Export the specified number of bytes of keying material; default is 20. Show all protocol messages with hex dump." }, { "flag": "", "long": null, "arg": null, "description": "Show verbose trace output of protocol messages." }, { "flag": "", "long": null, "arg": null, "description": "File to send output of -msg or -trace to, default standard output." }, { "flag": "", "long": null, "arg": null, "description": "Tests nonblocking I/O" }, { "flag": "", "long": null, "arg": null, "description": "Turns on nonblocking I/O" }, { "flag": "", "long": null, "arg": null, "description": "This option translated a line feed from the terminal into CR+LF as required by some servers." }, { "flag": "", "long": null, "arg": null, "description": "Inhibit shutting down the connection when end of file is reached in the input." }, { "flag": "", "long": null, "arg": null, "description": "Inhibit printing of session and certificate information. This implicitly turns on -igneof as well." }, { "flag": "", "long": null, "arg": null, "description": "Shut down the connection when end of file is reached in the input. Can be used to override the implicit -igneof after -quiet." }, { "flag": "", "long": null, "arg": null, "description": "Use the PSK identity identity when using a PSK cipher suite. The default value is \"Clientidentity\" (without the quotes)." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "Use the pem encoded SSLSESSION data stored in file as the basis of a PSK. Note that this will only work if TLSv1.3 is negotiated." }, { "flag": "", "long": null, "arg": null, "description": "Use SCTP for the transport protocol instead of UDP in DTLS. Must be used in conjunction with -dtls, -dtls1 or -dtls12. This option is only available where OpenSSL has support for SCTP enabled." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "Send TLSFALLBACKSCSV in the ClientHello." }, { "flag": "", "long": null, "arg": null, "description": "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)." }, { "flag": "", "long": null, "arg": null, "description": "Enable Maximum Fragment Length Negotiation; allowed values are 512, 1024, 2048, and 4096." }, { "flag": "", "long": null, "arg": null, "description": "The maximum size of data fragment to send. See SSLCTXsetmaxsendfragment(3) for further information." }, { "flag": "", "long": null, "arg": null, "description": "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 maxpipelines. This only has an effect if a suitable cipher suite has been negotiated, an engine that supports pipelining has been loaded, and maxpipelines is greater than 1. See SSLCTXsetsplitsendfragment(3) for further information." }, { "flag": "", "long": null, "arg": null, "description": "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 SSLCTXsetmaxpipelines(3) for further information." }, { "flag": "", "long": null, "arg": null, "description": "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 SSLCTXsetdefaultreadbufferlen(3) for further information)." }, { "flag": "", "long": null, "arg": null, "description": "Some TLS implementations do not send the mandatory closenotify alert on shutdown. If the application tries to wait for the closenotify 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 closenotify alert and a closed connection will be treated as if the closenotify alert was received. For more information on shutting down a connection, see SSLshutdown(3)." }, { "flag": "", "long": null, "arg": null, "description": "There are several known bugs in SSL and TLS implementations. Adding this option enables various workarounds." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "Disables support for SSL/TLS compression. TLS compression is not recommended and is off by default as of OpenSSL 1.1.0." }, { "flag": "", "long": null, "arg": null, "description": "Only provide a brief summary of connection parameters instead of the normal verbose output." }, { "flag": "", "long": null, "arg": null, "description": "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 SSLCTXset1sigalgs(3)" }, { "flag": "", "long": null, "arg": null, "description": "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 -listcurves" }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "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 ciphersuite names." }, { "flag": "", "long": null, "arg": null, "description": "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\" and \"ldap\"." }, { "flag": "", "long": null, "arg": null, "description": "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\"." }, { "flag": "", "long": null, "arg": null, "description": "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 used. 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 used." }, { "flag": "", "long": null, "arg": null, "description": "Print out a hex dump of any TLS extensions received from the server." }, { "flag": "", "long": null, "arg": null, "description": "Disable RFC4507bis session ticket support." }, { "flag": "", "long": null, "arg": null, "description": "Output SSL session to filename." }, { "flag": "", "long": null, "arg": null, "description": "Load SSL session from filename. The client will attempt to resume a connection from this session." }, { "flag": "", "long": null, "arg": null, "description": "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 file." }, { "flag": "", "long": null, "arg": null, "description": "Sends a certificate status request to the server (OCSP stapling). The server response (if any) is printed out." }, { "flag": "", "long": null, "arg": null, "description": "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 -tls13 is used." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "A file containing a list of known Certificate Transparency logs. See SSLCTXsetctloglistfile(3) for the expected file format." }, { "flag": "", "long": null, "arg": null, "description": "Appends TLS secrets to the specified keylog file such that external programs (like Wireshark) can decrypt TLS connections." }, { "flag": "", "long": null, "arg": null, "description": "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." }, { "flag": "", "long": null, "arg": null, "description": "For TLSv1.3 only, send the Post-Handshake Authentication extension. This will happen whether or not a certificate has been provided via -cert." }, { "flag": "", "long": null, "arg": null, "description": "Offer SRTP key management, where value is a colon-separated profile list." }, { "flag": "", "long": null, "arg": null, "description": "Set the SRP username to the specified value. This option is deprecated." }, { "flag": "", "long": null, "arg": null, "description": "Set the SRP password to the specified value. This option is deprecated." }, { "flag": "", "long": null, "arg": null, "description": "SRP username for the second ClientHello message. This option is deprecated." }, { "flag": "", "long": null, "arg": null, "description": "Tolerate other than the known g and N values." }, { "flag": "", "long": null, "arg": null, "description": "Set the minimal acceptable length, in bits, for N. This option is deprecated." }, { "flag": "", "long": null, "arg": null, "description": "" }, { "flag": "", "long": null, "arg": null, "description": "See \"TLS Version Options\" in openssl(1)." }, { "flag": "", "long": null, "arg": null, "description": "These specify the use of DTLS instead of TLS. See \"TLS Version Options\" in openssl(1)." }, { "flag": "", "long": null, "arg": null, "description": "This specifies how the subject or issuer names are displayed. See openssl-namedisplay-options(1) for details." }, { "flag": "", "long": null, "arg": null, "description": "DER|PEM Set extended certificate verification options. See \"Extended Verification Options\" in openssl-verification-options(1) for details." }, { "flag": "", "long": null, "arg": null, "description": "See \"Trusted Certificate Options\" in openssl-verification-options(1) for details." }, { "flag": "", "long": null, "arg": null, "description": "" }, { "flag": "", "long": null, "arg": null, "description": "" }, { "flag": "", "long": null, "arg": null, "description": "algs, -clientsigalgs algs, -groups groups, -curves curves, -namedcurve curve, -cipher ciphers, -ciphersuites 1.3ciphers, -minprotocol minprot, -maxprotocol maxprot," }, { "flag": "", "long": null, "arg": null, "description": "See \"SUPPORTED COMMAND LINE COMMANDS\" in SSLCONFcmd(3) for details." }, { "flag": "", "long": null, "arg": null, "description": "See \"Random State Options\" in openssl(1) for details." }, { "flag": "", "long": null, "arg": null, "description": "" }, { "flag": "", "long": null, "arg": null, "description": "" }, { "flag": "", "long": null, "arg": null, "description": "See \"Provider Options\" in openssl(1), provider(7), and property(7)." }, { "flag": "", "long": null, "arg": null, "description": "See \"Engine Options\" in openssl(1). This option is deprecated." }, { "flag": "", "long": null, "arg": null, "description": "Specify engine to be used for client certificate operations." }, { "flag": "", "long": null, "arg": null, "description": "" }, { "flag": "", "long": null, "arg": null, "description": "" }, { "flag": "", "long": null, "arg": null, "description": "" }, { "flag": "", "long": null, "arg": null, "description": "" }, { "flag": "", "long": null, "arg": null, "description": "Set various options of certificate chain verification. See \"Verification Options\" in openssl-verification-options(1) for details. Verification errors are displayed, for debugging, but the command will proceed unless the -verifyreturnerror option is used. host:port 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." } ], "examples": [], "see_also": [ { "name": "openssl", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/openssl/1/json" }, { "name": "openssl-sessid", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/openssl-sessid/1/json" }, { "name": "openssl-sserver", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/openssl-sserver/1/json" }, { "name": "openssl-ciphers", "section": "1", "url": "https://www.chedong.com/phpMan.php/man/openssl-ciphers/1/json" }, { "name": "SSLCONFcmd", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/SSLCONFcmd/3/json" }, { "name": "SSLCTXsetmaxsendfragment", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/SSLCTXsetmaxsendfragment/3/json" }, { "name": "SSLCTXsetsplitsendfragment", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/SSLCTXsetsplitsendfragment/3/json" }, { "name": "SSLCTXsetmaxpipelines", "section": "3", "url": "https://www.chedong.com/phpMan.php/man/SSLCTXsetmaxpipelines/3/json" }, { "name": "osslstore-file", "section": "7", "url": "https://www.chedong.com/phpMan.php/man/osslstore-file/7/json" } ] }