{
    "mode": "man",
    "parameter": "stunnel4",
    "section": "",
    "url": "https://www.chedong.com/phpMan.php/man/stunnel4/json",
    "generated": "2026-06-10T16:40:14Z",
    "synopsis": "",
    "sections": {
        "NAME": {
            "content": "stunnel - TLS offloading and load-balancing proxy\n",
            "subsections": []
        },
        "SYNOPSIS": {
            "content": "",
            "subsections": [
                {
                    "name": "Unix:",
                    "content": "stunnel [FILE] | -fd N | -help | -version | -sockets | -options\n"
                },
                {
                    "name": "WIN32:",
                    "content": "stunnel [ [ -install | -uninstall | -start | -stop |\n-reload | -reopen | -exit ] [-quiet] [FILE] ] |\n-help | -version | -sockets | -options\n"
                }
            ]
        },
        "DESCRIPTION": {
            "content": "The stunnel program is designed to work as TLS encryption wrapper between remote clients and\nlocal (inetd-startable) or remote servers. The concept is that having non-TLS aware daemons\nrunning on your system you can easily set them up to communicate with clients over secure TLS\nchannels.\n\nstunnel can be used to add TLS functionality to commonly used Inetd daemons like POP-2,\nPOP-3, and IMAP servers, to standalone daemons like NNTP, SMTP and HTTP, and in tunneling PPP\nover network sockets without changes to the source code.\n\nThis product includes cryptographic software written by Eric Young (eay@cryptsoft.com)\n",
            "subsections": []
        },
        "OPTIONS": {
            "content": "FILE\nUse specified configuration file\n",
            "subsections": [
                {
                    "name": "-fd",
                    "content": "Read the config file from specified file descriptor\n"
                },
                {
                    "name": "-help",
                    "content": "Print stunnel help menu\n"
                },
                {
                    "name": "-version",
                    "content": "Print stunnel version and compile time defaults\n"
                },
                {
                    "name": "-sockets",
                    "content": "Print default socket options\n"
                },
                {
                    "name": "-options",
                    "content": "Print supported TLS options\n"
                },
                {
                    "name": "-install",
                    "content": "Install NT Service\n"
                },
                {
                    "name": "-uninstall",
                    "content": "Uninstall NT Service\n"
                },
                {
                    "name": "-start",
                    "content": "Start NT Service\n"
                },
                {
                    "name": "-stop",
                    "content": "Stop NT Service\n"
                },
                {
                    "name": "-reload",
                    "content": "Reload the configuration file of the running NT Service\n"
                },
                {
                    "name": "-reopen",
                    "content": "Reopen the log file of the running NT Service\n"
                },
                {
                    "name": "-exit",
                    "content": "Exit an already started stunnel\n"
                },
                {
                    "name": "-quiet",
                    "content": "Don't display any message boxes\n"
                }
            ]
        },
        "CONFIGURATION FILE": {
            "content": "Each line of the configuration file can be either:\n\n•   An empty line (ignored).\n\n•   A comment starting with ';' (ignored).\n\n•   An 'optionname = optionvalue' pair.\n\n•   '[servicename]' indicating a start of a service definition.\n\nAn address parameter of an option may be either:\n\n•   A port number.\n\n•   A colon-separated pair of IP address (either IPv4, IPv6, or domain name) and port number.\n\n•   A Unix socket path (Unix only).\n\nGLOBAL OPTIONS\nchroot = DIRECTORY (Unix only)\ndirectory to chroot stunnel process\n\nchroot keeps stunnel in a chrooted jail.  CApath, CRLpath, pid and exec are located\ninside the jail and the patches have to be relative to the directory specified with\nchroot.\n\nSeveral functions of the operating system also need their files to be located within the\nchroot jail, e.g.:\n\n•   Delayed resolver typically needs /etc/nsswitch.conf and /etc/resolv.conf.\n\n•   Local time in log files needs /etc/timezone.\n\n•   Some other functions may need devices, e.g. /dev/zero or /dev/null.\n\ncompression = deflate | zlib\nselect data compression algorithm\n\ndefault: no compression\n\nDeflate is the standard compression method as described in RFC 1951.\n\ndebug = [FACILITY.]LEVEL\ndebugging level\n\nLevel is one of the syslog level names or numbers emerg (0), alert (1), crit (2), err\n(3), warning (4), notice (5), info (6), or debug (7).  All logs for the specified level\nand all levels numerically less than it will be shown.  Use debug = debug or debug = 7\nfor greatest debugging output.  The default is notice (5).\n\nThe syslog facility 'daemon' will be used unless a facility name is supplied.\n(Facilities are not supported on Win32.)\n\nCase is ignored for both facilities and levels.\n\nEGD = EGDPATH (Unix only)\npath to Entropy Gathering Daemon socket\n\nEntropy Gathering Daemon socket to use to feed the OpenSSL random number generator.\n\nengine = auto | ENGINEID\nselect hardware or software cryptographic engine\n\ndefault: software-only cryptography\n\nSee Examples section for an engine configuration to use the certificate and the\ncorresponding private key from a cryptographic device.\n\nengineCtrl = COMMAND[:PARAMETER]\ncontrol hardware engine\n\nengineDefault = TASKLIST\nset OpenSSL tasks delegated to the current engine\n\nThe parameter specifies a comma-separated list of task to be delegated to the current\nengine.\n\nThe following tasks may be available, if supported by the engine: ALL, RSA, DSA, ECDH,\nECDSA, DH, RAND, CIPHERS, DIGESTS, PKEY, PKEYCRYPTO, PKEYASN1.\n\nfips = yes | no\nenable or disable FIPS 140-2 mode.\n\nThis option allows you to disable entering FIPS mode if stunnel was compiled with FIPS\n140-2 support.\n\ndefault: no (since version 5.00)\n\nforeground = yes | quiet | no (Unix only)\nforeground mode\n\nStay in foreground (don't fork).\n\nWith the yes parameter it also logs to stderr in addition to the destinations specified\nwith syslog and output.\n\ndefault: background in daemon mode\n\niconActive = ICONFILE (GUI only)\nGUI icon to be displayed when there are established connections\n\nOn Windows platform the parameter should be an .ico file containing a 16x16 pixel image.\n\niconError = ICONFILE (GUI only)\nGUI icon to be displayed when no valid configuration is loaded\n\nOn Windows platform the parameter should be an .ico file containing a 16x16 pixel image.\n\niconIdle = ICONFILE (GUI only)\nGUI icon to be displayed when there are no established connections\n\nOn Windows platform the parameter should be an .ico file containing a 16x16 pixel image.\n\nlog = append | overwrite\nlog file handling\n\nThis option allows you to choose whether the log file (specified with the output option)\nis appended or overwritten when opened or re-opened.\n\ndefault: append\n\noutput = FILE\nappend log messages to a file\n\n/dev/stdout device can be used to send log messages to the standard output (for example\nto log them with daemontools splogger).\n\npid = FILE (Unix only)\npid file location\n\nIf the argument is empty, then no pid file will be created.\n\npid path is relative to the chroot directory if specified.\n\nRNDbytes = BYTES\nbytes to read from random seed files\n\nRNDfile = FILE\npath to file with random seed data\n\nThe OpenSSL library will use data from this file first to seed the random number\ngenerator.\n\nRNDoverwrite = yes | no\noverwrite the random seed files with new random data\n\ndefault: yes\n\nservice = SERVICE (Unix only)\nstunnel service name\n\nThe specified service name is used for syslog and as the inetd mode service name for TCP\nWrappers.  While this option can technically be specified in the service sections, it is\nonly useful in global options.\n\ndefault: stunnel\n\nsyslog = yes | no (Unix only)\nenable logging via syslog\n\ndefault: yes\n\ntaskbar = yes | no (WIN32 only)\nenable the taskbar icon\n\ndefault: yes\n\nSERVICE-LEVEL OPTIONS\nEach configuration section begins with a service name in square brackets.  The service name\nis used for libwrap (TCP Wrappers) access control and lets you distinguish stunnel services\nin your log files.\n\nNote that if you wish to run stunnel in inetd mode (where it is provided a network socket by\na server such as inetd, xinetd, or tcpserver) then you should read the section entitled INETD\nMODE below.\n\naccept = [HOST:]PORT\naccept connections on specified address\n\nIf no host specified, defaults to all IPv4 addresses for the local host.\n\nTo listen on all IPv6 addresses use:\n\naccept = :::PORT\n\nCApath = DIRECTORY\nCertificate Authority directory\n\nThis is the directory in which stunnel will look for certificates when using the\nverifyChain or verifyPeer options.  Note that the certificates in this directory should\nbe named XXXXXXXX.0 where XXXXXXXX is the hash value of the DER encoded subject of the\ncert.\n\nThe hash algorithm has been changed in OpenSSL 1.0.0.  It is required to crehash the\ndirectory on upgrade from OpenSSL 0.x.x to OpenSSL 1.x.x.\n\nCApath path is relative to the chroot directory if specified.\n\nCAfile = CAFILE\nCertificate Authority file\n\nThis file contains multiple CA certificates, to be used with the verifyChain and\nverifyPeer options.\n\ncert = CERTFILE\ncertificate chain file name\n\nThe parameter specifies the file containing certificates used by stunnel to authenticate\nitself against the remote client or server.  The file should contain the whole\ncertificate chain starting from the actual server/client certificate, and ending with the\nself-signed root CA certificate.  The file must be either in PEM or P12 format.\n\nA certificate chain is required in server mode, and optional in client mode.\n\nThis parameter is also used as the certificate identifier when a hardware engine is\nenabled.\n\ncheckEmail = EMAIL\nemail address of the peer certificate subject\n\nMultiple checkEmail options are allowed in a single service section.  Certificates are\naccepted if no subject checks were specified, or the email address of the peer\ncertificate matches any of the email addresses specified with checkEmail.\n\nThis option requires OpenSSL 1.0.2 or later.\n\ncheckHost = HOST\nhost of the peer certificate subject\n\nMultiple checkHost options are allowed in a single service section.  Certificates are\naccepted if no subject checks were specified, or the host name of the peer certificate\nmatches any of the hosts specified with checkHost.\n\nThis option requires OpenSSL 1.0.2 or later.\n\ncheckIP = IP\nIP address of the peer certificate subject\n\nMultiple checkIP options are allowed in a single service section.  Certificates are\naccepted if no subject checks were specified, or the IP address of the peer certificate\nmatches any of the IP addresses specified with checkIP.\n\nThis option requires OpenSSL 1.0.2 or later.\n\nciphers = CIPHERLIST\nselect permitted TLS ciphers (TLSv1.2 and below)\n\nThis option does not impact TLSv1.3 ciphersuites.\n\nA colon-delimited list of the ciphers to allow in the TLS connection, for example\nDES-CBC3-SHA:IDEA-CBC-MD5.\n\nciphersuites = CIPHERSUITESLIST\nselect permitted TLSv1.3 ciphersuites\n\nA colon-delimited list of TLSv1.3 ciphersuites names in order of preference.\n\nThis option requires OpenSSL 1.1.1 or later.\n\ndefault: TLSCHACHA20POLY1305SHA256:TLSAES256GCMSHA384:TLSAES128GCMSHA256\n\nclient = yes | no\nclient mode (remote service uses TLS)\n\ndefault: no (server mode)\n\nconfig = COMMAND[:PARAMETER]\nOpenSSL configuration command\n\nThe OpenSSL configuration command is executed with the specified parameter.  This allows\nany configuration commands to be invoked from the stunnel configuration file.  Supported\ncommands are described on the SSSSLLCCOONNFFccmmdd(3ssl) manual page.\n\nSeveral config lines can be used to specify multiple configuration commands.\n\nUse curves option instead of enabling config = Curves:listcurves to support elliptic\ncurves.\n\nThis option requires OpenSSL 1.0.2 or later.\n\nconnect = [HOST:]PORT\nconnect to a remote address\n\nIf no host is specified, the host defaults to localhost.\n\nMultiple connect options are allowed in a single service section.\n\nIf host resolves to multiple addresses and/or if multiple connect options are specified,\nthen the remote address is chosen using a round-robin algorithm.\n\nCRLpath = DIRECTORY\nCertificate Revocation Lists directory\n\nThis is the directory in which stunnel will look for CRLs when using the verifyChain and\nverifyPeer options. Note that the CRLs in this directory should be named XXXXXXXX.r0\nwhere XXXXXXXX is the hash value of the CRL.\n\nThe hash algorithm has been changed in OpenSSL 1.0.0.  It is required to crehash the\ndirectory on upgrade from OpenSSL 0.x.x to OpenSSL 1.x.x.\n\nCRLpath path is relative to the chroot directory if specified.\n\nCRLfile = CRLFILE\nCertificate Revocation Lists file\n\nThis file contains multiple CRLs, used with the verifyChain and verifyPeer options.\n\ncurves = list\nECDH curves separated with ':'\n\nOnly a single curve name is allowed for OpenSSL older than 1.1.1.\n\nTo get a list of supported curves use:\n\nopenssl ecparam -listcurves\n\ndefault:\n\nX25519:P-256:X448:P-521:P-384 (OpenSSL 1.1.1 or later)\n\nprime256v1 (OpenSSL older than 1.1.1)\n\nlogId = TYPE\nconnection identifier type\n\nThis identifier allows you to distinguish log entries generated for each of the\nconnections.\n\nCurrently supported types:\n\nsequential\nThe numeric sequential identifier is only unique within a single instance of stunnel,\nbut very compact.  It is most useful for manual log analysis.\n\nunique\nThis alphanumeric identifier is globally unique, but longer than the sequential\nnumber.  It is most useful for automated log analysis.\n\nthread\nThe operating system thread identifier is neither unique (even within a single\ninstance of stunnel) nor short.  It is most useful for debugging software or\nconfiguration issues.\n\nprocess\nThe operating system process identifier (PID) may be useful in the inetd mode.\n\ndefault: sequential\n\ndebug = LEVEL\ndebugging level\n\nLevel is a one of the syslog level names or numbers emerg (0), alert (1), crit (2), err\n(3), warning (4), notice (5), info (6), or debug (7).  All logs for the specified level\nand all levels numerically less than it will be shown.  The default is notice (5).\n\nWhile the debug = debug or debug = 7 level generates the most verbose output, it is only\nintended to be used by stunnel developers.  Please only use this value if you are a\ndeveloper, or you intend to send your logs to our technical support.  Otherwise, the\ngenerated logs will be confusing.\n\ndelay = yes | no\ndelay DNS lookup for the connect option\n\nThis option is useful for dynamic DNS, or when DNS is not available during stunnel\nstartup (road warrior VPN, dial-up configurations).\n\nDelayed resolver mode is automatically engaged when stunnel fails to resolve on startup\nany of the connect targets for a service.\n\nDelayed resolver inflicts failover = prio.\n\ndefault: no\n\nengineId = ENGINEID\nselect engine ID for the service\n\nengineNum = ENGINENUMBER\nselect engine number for the service\n\nThe engines are numbered starting from 1.\n\nexec = EXECUTABLEPATH\nexecute a local inetd-type program\n\nexec path is relative to the chroot directory if specified.\n\nThe following environmental variables are set on Unix platforms: REMOTEHOST,\nREMOTEPORT, SSLCLIENTDN, SSLCLIENTIDN.\n\nexecArgs = $0 $1 $2 ...\narguments for exec including the program name ($0)\n\nQuoting is currently not supported.  Arguments are separated with an arbitrary amount of\nwhitespace.\n\nfailover = rr | prio\nFailover strategy for multiple \"connect\" targets.\n\nrr  round robin - fair load distribution\n\nprio\npriority - use the order specified in config file\n\ndefault: prio\n\nident = USERNAME\nuse IDENT (RFC 1413) username checking\n\ninclude = DIRECTORY\ninclude all configuration file parts located in DIRECTORY\n\nThe files are included in the ascending alphabetical order of their names. The\nrecommended filename convention is\n\nfor global options:\n\n00-global.conf\n\nfor local service-level options:\n\n01-service.conf\n\n02-service.conf\n\nkey = KEYFILE\nprivate key for the certificate specified with cert option\n\nA private key is needed to authenticate the certificate owner.  Since this file should be\nkept secret it should only be readable by its owner.  On Unix systems you can use the\nfollowing command:\n\nchmod 600 keyfile\n\nThis parameter is also used as the private key identifier when a hardware engine is\nenabled.\n\ndefault: the value of the cert option\n\nlibwrap = yes | no\nEnable or disable the use of /etc/hosts.allow and /etc/hosts.deny.\n\ndefault: no (since version 5.00)\n\nlocal = HOST\nBy default, the IP address of the outgoing interface is used as the source for remote\nconnections.  Use this option to bind a static local IP address instead.\n\nOCSP = URL\nselect OCSP responder for certificate verification\n\nOCSPaia = yes | no\nvalidate certificates with their AIA OCSP responders\n\nThis option enables stunnel to validate certificates with the list of OCSP responder URLs\nretrieved from their AIA (Authority Information Access) extension.\n\nOCSPflag = OCSPFLAG\nspecify OCSP responder flag\n\nSeveral OCSPflag can be used to specify multiple flags.\n\ncurrently supported flags: NOCERTS, NOINTERN, NOSIGS, NOCHAIN, NOVERIFY, NOEXPLICIT,\nNOCASIGN, NODELEGATED, NOCHECKS, TRUSTOTHER, RESPIDKEY, NOTIME\n\nOCSPnonce = yes | no\nsend and verify the OCSP nonce extension\n\nThis option protects the OCSP protocol against replay attacks.  Due to its computational\noverhead, the nonce extension is usually only supported on internal (e.g. corporate)\nresponders, and not on public OCSP responders.\n\noptions = SSLOPTIONS\nOpenSSL library options\n\nThe parameter is the OpenSSL option name as described in the SSSSLLCCTTXXsseettooppttiioonnss(3ssl)\nmanual, but without SSLOP prefix.  stunnel -options lists the options found to be\nallowed in the current combination of stunnel and the OpenSSL library used to build it.\n\nSeveral option lines can be used to specify multiple options.  An option name can be\nprepended with a dash (\"-\") to disable the option.\n\nFor example, for compatibility with the erroneous Eudora TLS implementation, the\nfollowing option can be used:\n\noptions = DONTINSERTEMPTYFRAGMENTS\n\ndefault:\n\noptions = NOSSLv2\noptions = NOSSLv3\n\nUse sslVersionMax or sslVersionMin option instead of disabling specific TLS protocol\nversions when compiled with OpenSSL 1.1.0 or later.\n\nprotocol = PROTO\napplication protocol to negotiate TLS\n\nThis option enables initial, protocol-specific negotiation of the TLS encryption.  The\nprotocol option should not be used with TLS encryption on a separate port.\n\nCurrently supported protocols:\n\ncifs\nProprietary (undocummented) extension of CIFS protocol implemented in Samba.  Support\nfor this extension was dropped in Samba 3.0.0.\n\ncapwin\nhttp://www.capwin.org/ application support\n\ncapwinctrl\nhttp://www.capwin.org/ application support\n\nThis protocol is only supported in client mode.\n\nconnect\nBased on RFC 2817 - Upgrading to TLS Within HTTP/1.1, section 5.2 - Requesting a\nTunnel with CONNECT\n\nThis protocol is only supported in client mode.\n\nimap\nBased on RFC 2595 - Using TLS with IMAP, POP3 and ACAP\n\nldap\nBased on RFC 2830 - Lightweight Directory Access Protocol (v3): Extension for\nTransport Layer Security\n\nnntp\nBased on RFC 4642 - Using Transport Layer Security (TLS) with Network News Transfer\nProtocol (NNTP)\n\nThis protocol is only supported in client mode.\n\npgsql\nBased on http://www.postgresql.org/docs/8.3/static/protocol-flow.html#AEN73982\n\npop3\nBased on RFC 2449 - POP3 Extension Mechanism\n\nproxy\nPassing of the original client IP address with HAProxy PROXY protocol version 1\nhttps://www.haproxy.org/download/1.8/doc/proxy-protocol.txt\n\nsmtp\nBased on RFC 2487 - SMTP Service Extension for Secure SMTP over TLS\n\nsocks\nSOCKS versions 4, 4a, and 5 are supported.  The SOCKS protocol itself is encapsulated\nwithin TLS encryption layer to protect the final destination address.\n\nhttp://www.openssh.com/txt/socks4.protocol\n\nhttp://www.openssh.com/txt/socks4a.protocol\n\nThe BIND command of the SOCKS protocol is not supported.  The USERID parameter is\nignored.\n\nSee Examples section for sample configuration files for VPN based on SOCKS\nencryption.\n\nprotocolAuthentication = AUTHENTICATION\nauthentication type for the protocol negotiations\n\nCurrently, this option is only supported in the client-side 'connect' and 'smtp'\nprotocols.\n\nSupported authentication types for the 'connect' protocol are 'basic' or 'ntlm'.  The\ndefault 'connect' authentication type is 'basic'.\n\nSupported authentication types for the 'smtp' protocol are 'plain' or 'login'.  The\ndefault 'smtp' authentication type is 'plain'.\n\nprotocolDomain = DOMAIN\ndomain for the protocol negotiations\n\nCurrently, this option is only supported in the client-side 'connect' protocol.\n\nprotocolHeader = HEADER\nheader for the protocol negotiations\n\nCurrently, this option is only supported in the client-side 'connect' protocol.\n\nprotocolHost = ADDRESS\nhost address for the protocol negotiations\n\nFor the 'connect' protocol negotiations, protocolHost specifies HOST:PORT of the final\nTLS server to be connected to by the proxy.  The proxy server directly connected by\nstunnel must be specified with the connect option.\n\nFor the 'smtp' protocol negotiations, protocolHost controls the client SMTP HELO/EHLO\nvalue.\n\nprotocolPassword = PASSWORD\npassword for the protocol negotiations\n\nCurrently, this option is only supported in the client-side 'connect' and 'smtp'\nprotocols.\n\nprotocolUsername = USERNAME\nusername for the protocol negotiations\n\nCurrently, this option is only supported in the client-side 'connect' and 'smtp'\nprotocols.\n\nPSKidentity = IDENTITY\nPSK identity for the PSK client\n\nPSKidentity can be used on stunnel clients to select the PSK identity used for\nauthentication.  This option is ignored in server sections.\n\ndefault: the first identity specified in the PSKsecrets file.\n\nPSKsecrets = FILE\nfile with PSK identities and corresponding keys\n\nEach line of the file in the following format:\n\nIDENTITY:KEY\n\nHexadecimal keys are automatically converted to binary form.  Keys are required to be at\nleast 16 bytes long, which implies at least 32 characters for hexadecimal keys.  The file\nshould neither be world-readable nor world-writable.\n\npty = yes | no (Unix only)\nallocate a pseudoterminal for 'exec' option\n\nredirect = [HOST:]PORT\nredirect TLS client connections on certificate-based authentication failures\n\nThis option only works in server mode.  Some protocol negotiations are also incompatible\nwith the redirect option.\n\nrenegotiation = yes | no\nsupport TLS renegotiation\n\nApplications of the TLS renegotiation include some authentication scenarios, or re-keying\nlong lasting connections.\n\nOn the other hand this feature can facilitate a trivial CPU-exhaustion DoS attack:\n\nhttp://vincent.bernat.im/en/blog/2011-ssl-dos-mitigation.html\n\nPlease note that disabling TLS renegotiation does not fully mitigate this issue.\n\ndefault: yes (if supported by OpenSSL)\n\nreset = yes | no\nattempt to use the TCP RST flag to indicate an error\n\nThis option is not supported on some platforms.\n\ndefault: yes\n\nretry = yes | no\nreconnect a connect+exec section after it was disconnected\n\ndefault: no\n\nsecurityLevel = LEVEL\nset the security level\n\nThe meaning of each level is described below:\n\nlevel 0\nEverything is permitted.\n\nlevel 1\nThe security level corresponds to a minimum of 80 bits of security. Any parameters\noffering below 80 bits of security are excluded. As a result RSA, DSA and DH keys\nshorter than 1024 bits and ECC keys shorter than 160 bits are prohibited. All export\ncipher suites are prohibited since they all offer less than 80 bits of security. SSL\nversion 2 is prohibited. Any cipher suite using MD5 for the MAC is also prohibited.\n\nlevel 2\nSecurity level set to 112 bits of security. As a result RSA, DSA and DH keys shorter\nthan 2048 bits and ECC keys shorter than 224 bits are prohibited. In addition to the\nlevel 1 exclusions any cipher suite using RC4 is also prohibited. SSL version 3 is\nalso not allowed. Compression is disabled.\n\nlevel 3\nSecurity level set to 128 bits of security. As a result RSA, DSA and DH keys shorter\nthan 3072 bits and ECC keys shorter than 256 bits are prohibited. In addition to the\nlevel 2 exclusions cipher suites not offering forward secrecy are prohibited. TLS\nversions below 1.1 are not permitted. Session tickets are disabled.\n\nlevel 4\nSecurity level set to 192 bits of security. As a result RSA, DSA and DH keys shorter\nthan 7680 bits and ECC keys shorter than 384 bits are prohibited. Cipher suites using\nSHA1 for the MAC are prohibited. TLS versions below 1.2 are not permitted.\n\nlevel 5\nSecurity level set to 256 bits of security. As a result RSA, DSA and DH keys shorter\nthan 15360 bits and ECC keys shorter than 512 bits are prohibited.\n\ndefault: 2\n\nThe securityLevel option is only available when compiled with OpenSSL 1.1.0 and later.\n\nrequireCert = yes | no\nrequire a client certificate for verifyChain or verifyPeer\n\nWith requireCert set to no, the stunnel server accepts client connections that did not\npresent a certificate.\n\nBoth verifyChain = yes and verifyPeer = yes imply requireCert = yes.\n\ndefault: no\n\nsetgid = GROUP (Unix only)\nUnix group id\n\nAs a global option: setgid() to the specified group in daemon mode and clear all other\ngroups.\n\nAs a service-level option: set the group of the Unix socket specified with \"accept\".\n\nsetuid = USER (Unix only)\nUnix user id\n\nAs a global option: setuid() to the specified user in daemon mode.\n\nAs a service-level option: set the owner of the Unix socket specified with \"accept\".\n\nsessionCacheSize = NUMENTRIES\nsession cache size\n\nsessionCacheSize specifies the maximum number of the internal session cache entries.\n\nThe value of 0 can be used for unlimited size.  It is not recommended for production use\ndue to the risk of a memory exhaustion DoS attack.\n\nsessionCacheTimeout = TIMEOUT\nsession cache timeout\n\nThis is the number of seconds to keep cached TLS sessions.\n\nsessionResume = yes | no\nallow or disallow session resumption\n\ndefault: yes\n\nsessiond = HOST:PORT\naddress of sessiond TLS cache server\n\nsni = SERVICENAME:SERVERNAMEPATTERN (server mode)\nUse the service as a slave service (a name-based virtual server) for Server Name\nIndication TLS extension (RFC 3546).\n\nSERVICENAME specifies the master service that accepts client connections with the accept\noption.  SERVERNAMEPATTERN specifies the host name to be redirected.  The pattern may\nstart with the '*' character, e.g.  '*.example.com'.  Multiple slave services are\nnormally specified for a single master service.  The sni option can also be specified\nmore than once within a single slave service.\n\nThis service, as well as the master service, may not be configured in client mode.\n\nThe connect option of the slave service is ignored when the protocol option is specified,\nas protocol connects to the remote host before TLS handshake.\n\nLibwrap checks (Unix only) are performed twice: with the master service name after TCP\nconnection is accepted, and with the slave service name during the TLS handshake.\n\nThe sni option is only available when compiled with OpenSSL 1.0.0 and later.\n\nsni = SERVERNAME (client mode)\nUse the parameter as the value of TLS Server Name Indication (RFC 3546) extension.\n\nEmpty SERVERNAME disables sending the SNI extension.\n\nThe sni option is only available when compiled with OpenSSL 1.0.0 and later.\n\nsocket = a|l|r:OPTION=VALUE[:VALUE]\nSet an option on the accept/local/remote socket\n\nThe values for the linger option are lonof:llinger.  The values for the time are\ntvsec:tvusec.\n\nExamples:\n\nsocket = l:SOLINGER=1:60\nset one minute timeout for closing local socket\nsocket = r:SOOOBINLINE=yes\nplace out-of-band data directly into the\nreceive data stream for remote sockets\nsocket = a:SOREUSEADDR=no\ndisable address reuse (enabled by default)\nsocket = a:SOBINDTODEVICE=lo\nonly accept connections on loopback interface\n\nsslVersion = SSLVERSION\nselect the TLS protocol version\n\nSupported versions: all, SSLv2, SSLv3, TLSv1, TLSv1.1, TLSv1.2, TLSv1.3\n\nAvailability of specific protocols depends on the linked OpenSSL library.  Older versions\nof OpenSSL do not support TLSv1.1, TLSv1.2 and TLSv1.3.  Newer versions of OpenSSL do not\nsupport SSLv2.\n\nObsolete SSLv2 and SSLv3 are currently disabled by default.\n\nSetting the option\n\nsslVersion = SSLVERSION\n\nis equivalent to options\n\nsslVersionMax = SSLVERSION\nsslVersionMin = SSLVERSION\n\nwhen compiled with OpenSSL 1.1.0 and later.\n\nsslVersionMax = SSLVERSION\nmaximum supported protocol versions\n\nSupported versions: all, SSLv3, TLSv1, TLSv1.1, TLSv1.2, TLSv1.3\n\nall enable protocol versions up to the highest version supported by the linked OpenSSL\nlibrary.\n\nAvailability of specific protocols depends on the linked OpenSSL library.\n\nThe sslVersionMax option is only available when compiled with OpenSSL 1.1.0 and later.\n\ndefault: all\n\nsslVersionMin = SSLVERSION\nminimum supported protocol versions\n\nSupported versions: all, SSLv3, TLSv1, TLSv1.1, TLSv1.2, TLSv1.3\n\nall enable protocol versions down to the lowest version supported by the linked OpenSSL\nlibrary.\n\nAvailability of specific protocols depends on the linked OpenSSL library.\n\nThe sslVersionMin option is only available when compiled with OpenSSL 1.1.0 and later.\n\ndefault: TLSv1\n\nstack = BYTES (except for FORK model)\nCPU stack size of created threads\n\nExcessive thread stack size increases virtual memory usage.  Insufficient thread stack\nsize may cause application crashes.\n\ndefault: 65536 bytes (sufficient for all platforms we tested)\n\nticketKeySecret = SECRET\nhexadecimal symmetric key used for session ticket confidentiality protection\n\nSession tickets defined in RFC 5077 provide an enhanced session resumption capability,\nwhere the server-side caching is not required to maintain per session state.\n\nCombining ticketKeySecret and ticketMacSecret options allow to resume a negotiated\nsession on other cluster nodes, or to resume a negotiated session after server restart.\n\nThe key is required to be either 16 or 32 bytes long, which implies exactly 32 or 64\nhexadecimal digits.  Colons may optionally be used between two-character hexadecimal\nbytes.\n\nThis option only works in server mode.\n\nThe ticketKeySecret option is only available when compiled with OpenSSL 1.0.0 and later.\n\nDisabling NOTICKET option is required for the ticket support in OpenSSL older than\n1.1.1, but note that this option is incompatible with the redirect option.\n\nticketMacSecret = SECRET\nhexadecimal symmetric key used for session ticket integrity protection\n\nThe key is required to be either 16 or 32 bytes long, which implies exactly 32 or 64\nhexadecimal digits.  Colons may optionally be used between two-character hexadecimal\nbytes.\n\nThis option only works in server mode.\n\nThe ticketMacSecret option is only available when compiled with OpenSSL 1.0.0 and later.\n\nTIMEOUTbusy = SECONDS\ntime to wait for expected data\n\nTIMEOUTclose = SECONDS\ntime to wait for closenotify (set to 0 for buggy MSIE)\n\nTIMEOUTconnect = SECONDS\ntime to wait to connect to a remote host\n\nTIMEOUTidle = SECONDS\ntime to keep an idle connection\n\ntransparent = none | source | destination | both (Unix only)\nenable transparent proxy support on selected platforms\n\nSupported values:\n\nnone\nDisable transparent proxy support.  This is the default.\n\nsource\nRe-write the address to appear as if a wrapped daemon is connecting from the TLS\nclient machine instead of the machine running stunnel.\n\nThis option is currently available in:\n\nRemote mode (connect option) on Linux >=2.6.28\nThis configuration requires stunnel to be executed as root and without the setuid\noption.\n\nThis configuration requires the following setup for iptables and routing\n(possibly in /etc/rc.local or equivalent file):\n\niptables -t mangle -N DIVERT\niptables -t mangle -A PREROUTING -p tcp -m socket -j DIVERT\niptables -t mangle -A DIVERT -j MARK --set-mark 1\niptables -t mangle -A DIVERT -j ACCEPT\nip rule add fwmark 1 lookup 100\nip route add local 0.0.0.0/0 dev lo table 100\necho 0 >/proc/sys/net/ipv4/conf/lo/rpfilter\n\nstunnel must also to be executed as root and without the setuid option.\n\nRemote mode (connect option) on Linux 2.2.x\nThis configuration requires the kernel to be compiled with the transparent proxy\noption.  Connected service must be installed on a separate host.  Routing towards\nthe clients has to go through the stunnel box.\n\nstunnel must also to be executed as root and without the setuid option.\n\nRemote mode (connect option) on FreeBSD >=8.0\nThis configuration requires additional firewall and routing setup.  stunnel must\nalso to be executed as root and without the setuid option.\n\nLocal mode (exec option)\nThis configuration works by pre-loading the libstunnel.so shared library.\nRLDLIST environment variable is used on Tru64, and LDPRELOAD variable on other\nplatforms.\n\ndestination\nThe original destination is used instead of the connect option.\n\nA service section for transparent destination may look like this:\n\n[transparent]\nclient = yes\naccept = <stunnelport>\ntransparent = destination\n\nThis configuration requires iptables setup to work, possibly in /etc/rc.local or\nequivalent file.\n\nFor a connect target installed on the same host:\n\n/sbin/iptables -t nat -I OUTPUT -p tcp --dport <redirectedport> \\\n-m ! --uid-owner <stunneluserid> \\\n-j DNAT --to-destination <localip>:<stunnelport>\n\nFor a connect target installed on a remote host:\n\n/sbin/iptables -I INPUT -i eth0 -p tcp --dport <stunnelport> -j ACCEPT\n/sbin/iptables -t nat -I PREROUTING -p tcp --dport <redirectedport> \\\n-i eth0 -j DNAT --to-destination <localip>:<stunnelport>\n\nThe transparent destination option is currently only supported on Linux.\n\nboth\nUse both source and destination transparent proxy.\n\nTwo legacy options are also supported for backward compatibility:\n\nyes This option has been renamed to source.\n\nno  This option has been renamed to none.\n\nverify = LEVEL\nverify the peer certificate\n\nThis option is obsolete and should be replaced with the verifyChain and verifyPeer\noptions.\n\nlevel 0\nRequest and ignore the peer certificate.\n\nlevel 1\nVerify the peer certificate if present.\n\nlevel 2\nVerify the peer certificate.\n\nlevel 3\nVerify the peer against a locally installed certificate.\n\nlevel 4\nIgnore the chain and only verify the peer certificate.\n\ndefault\nNo verify.\n\nverifyChain = yes | no\nverify the peer certificate chain starting from the root CA\n\nFor server certificate verification it is essential to also require a specific\ncertificate with checkHost or checkIP.\n\nThe self-signed root CA certificate needs to be stored either in the file specified with\nCAfile, or in the directory specified with CApath.\n\ndefault: no\n\nverifyPeer = yes | no\nverify the peer certificate\n\nThe peer certificate needs to be stored either in the file specified with CAfile, or in\nthe directory specified with CApath.\n\ndefault: no\n",
            "subsections": []
        },
        "RETURN VALUE": {
            "content": "stunnel returns zero on success, non-zero on error.\n",
            "subsections": []
        },
        "SIGNALS": {
            "content": "The following signals can be used to control stunnel in Unix environment:\n\nSIGHUP\nForce a reload of the configuration file.\n\nSome global options will not be reloaded:\n\n•   chroot\n\n•   foreground\n\n•   pid\n\n•   setgid\n\n•   setuid\n\nThe use of the 'setuid' option will also prevent stunnel from binding to privileged\n(<1024) ports during configuration reloading.\n\nWhen the 'chroot' option is used, stunnel will look for all its files (including the\nconfiguration file, certificates, the log file and the pid file) within the chroot jail.\n\nSIGUSR1\nClose and reopen the stunnel log file.  This function can be used for log rotation.\n\nSIGUSR2\nLog the list of active connections.\n\nSIGTERM, SIGQUIT, SIGINT\nShut stunnel down.\n\nThe result of sending any other signals to the server is undefined.\n",
            "subsections": []
        },
        "EXAMPLES": {
            "content": "In order to provide TLS encapsulation to your local imapd service, use:\n\n[imapd]\naccept = 993\nexec = /usr/sbin/imapd\nexecArgs = imapd\n\nor in remote mode:\n\n[imapd]\naccept = 993\nconnect = 143\n\nIn order to let your local e-mail client connect to a TLS-enabled imapd service on another\nserver, configure the e-mail client to connect to localhost on port 119 and use:\n\n[imap]\nclient = yes\naccept = 143\nconnect = servername:993\n\nIf you want to provide tunneling to your pppd daemon on port 2020, use something like:\n\n[vpn]\naccept = 2020\nexec = /usr/sbin/pppd\nexecArgs = pppd local\npty = yes\n\nIf you want to use stunnel in inetd mode to launch your imapd process, you'd use this\nstunnel.conf.  Note there must be no [servicename] section.\n\nexec = /usr/sbin/imapd\nexecArgs = imapd\n\nTo setup SOCKS VPN configure the following client service:\n\n[socksclient]\nclient = yes\naccept = 127.0.0.1:1080\nconnect = vpnserver:9080\nverifyPeer = yes\nCAfile = stunnel.pem\n\nThe corresponding configuration on the vpnserver host:\n\n[socksserver]\nprotocol = socks\naccept = 9080\ncert = stunnel.pem\nkey = stunnel.key\n\nNow test your configuration on the client machine with:\n\ncurl --socks4a localhost http://www.example.com/\n\nAn example server mode SNI configuration:\n\n[virtual]\n; master service\naccept = 443\ncert =  default.pem\nconnect = default.internal.mydomain.com:8080\n\n[sni1]\n; slave service 1\nsni = virtual:server1.mydomain.com\ncert = server1.pem\nconnect = server1.internal.mydomain.com:8081\n\n[sni2]\n; slave service 2\nsni = virtual:server2.mydomain.com\ncert = server2.pem\nconnect = server2.internal.mydomain.com:8082\nverifyPeer = yes\nCAfile = server2-allowed-clients.pem\n\nAn example of advanced engine configuration allows for authentication with private keys\nstored in the Windows certificate store (Windows only).  With the CAPI engine you don't need\nto manually select the client key to use.  The client key is automatically selected based on\nthe list of CAs trusted by the server.\n\nengine = capi\n\n[service]\nengineId = capi\nclient = yes\naccept = 127.0.0.1:8080\nconnect = example.com:8443\n\nAn example of advanced engine configuration to use the certificate and the corresponding\nprivate key from a pkcs11 engine:\n\nengine = pkcs11\nengineCtrl = MODULEPATH:opensc-pkcs11.so\nengineCtrl = PIN:123456\n\n[service]\nengineId = pkcs11\nclient = yes\naccept = 127.0.0.1:8080\nconnect = example.com:843\ncert = pkcs11:token=MyToken;object=MyCert\nkey = pkcs11:token=MyToken;object=MyKey\n\nAn example of advanced engine configuration to use the certificate and the corresponding\nprivate key from a SoftHSM token:\n\nengine = pkcs11\nengineCtrl = MODULEPATH:softhsm2.dll\nengineCtrl = PIN:12345\n\n[service]\nengineId = pkcs11\nclient = yes\naccept = 127.0.0.1:8080\nconnect = example.com:843\ncert = pkcs11:token=MyToken;object=KeyCert\n",
            "subsections": []
        },
        "NOTES": {
            "content": "RESTRICTIONS\nstunnel cannot be used for the FTP daemon because of the nature of the FTP protocol which\nutilizes multiple ports for data transfers.  There are available TLS-enabled versions of FTP\nand telnet daemons, however.\n\nINETD MODE\nThe most common use of stunnel is to listen on a network port and establish communication\nwith either a new port via the connect option, or a new program via the exec option.  However\nthere is a special case when you wish to have some other program accept incoming connections\nand launch stunnel, for example with inetd, xinetd, or tcpserver.\n\nFor example, if you have the following line in inetd.conf:\n\nimaps stream tcp nowait root /usr/bin/stunnel stunnel /etc/stunnel/imaps.conf\n\nIn these cases, the inetd-style program is responsible for binding a network socket (imaps\nabove) and handing it to stunnel when a connection is received.  Thus you do not want stunnel\nto have any accept option.  All the Service Level Options should be placed in the global\noptions section, and no [servicename] section will be present.  See the EXAMPLES section for\nexample configurations.\n\nCERTIFICATES\nEach TLS-enabled daemon needs to present a valid X.509 certificate to the peer. It also needs\na private key to decrypt the incoming data. The easiest way to obtain a certificate and a key\nis to generate them with the free OpenSSL package. You can find more information on\ncertificates generation on pages listed below.\n\nThe .pem file should contain the unencrypted private key and a signed certificate (not\ncertificate request).  So the file should look like this:\n\n-----BEGIN RSA PRIVATE KEY-----\n[encoded key]\n-----END RSA PRIVATE KEY-----\n-----BEGIN CERTIFICATE-----\n[encoded certificate]\n-----END CERTIFICATE-----\n\nRANDOMNESS\nstunnel needs to seed the PRNG (pseudo-random number generator) in order for TLS to use good\nrandomness.  The following sources are loaded in order until sufficient random data has been\ngathered:\n\n•   The file specified with the RNDfile flag.\n\n•   The file specified by the RANDFILE environment variable, if set.\n\n•   The file .rnd in your home directory, if RANDFILE not set.\n\n•   The file specified with '--with-random' at compile time.\n\n•   The contents of the screen if running on Windows.\n\n•   The egd socket specified with the EGD flag.\n\n•   The egd socket specified with '--with-egd-sock' at compile time.\n\n•   The /dev/urandom device.\n\nNote that on Windows machines that do not have console user interaction (mouse movements,\ncreating windows, etc.) the screen contents are not variable enough to be sufficient, and you\nshould provide a random file for use with the RNDfile flag.\n\nNote that the file specified with the RNDfile flag should contain random data -- that means\nit should contain different information each time stunnel is run.  This is handled\nautomatically unless the RNDoverwrite flag is used.  If you wish to update this file\nmanually, the openssl rand command in recent versions of OpenSSL, would be useful.\n\nImportant note: If /dev/urandom is available, OpenSSL often seeds the PRNG with it while\nchecking the random state.  On systems with /dev/urandom OpenSSL is likely to use it even\nthough it is listed at the very bottom of the list above.  This is the behaviour of OpenSSL\nand not stunnel.\n\nDH PARAMETERS\nstunnel 4.40 and later contains hardcoded 2048-bit DH parameters.  Starting with stunnel\n5.18, these hardcoded DH parameters are replaced every 24 hours with autogenerated temporary\nDH parameters.  DH parameter generation may take several minutes.\n\nAlternatively, it is possible to specify static DH parameters in the certificate file, which\ndisables generating temporary DH parameters:\n\nopenssl dhparam 2048 >> stunnel.pem\n",
            "subsections": []
        },
        "FILES": {
            "content": "/etc/stunnel/stunnel.conf\nstunnel configuration file\n",
            "subsections": []
        },
        "BUGS": {
            "content": "The execArgs option and the Win32 command line do not support quoting.\n",
            "subsections": []
        },
        "SEE ALSO": {
            "content": "tcpd(8)\naccess control facility for internet services\n\ninetd(8)\ninternet 'super-server'\n\nhttp://www.stunnel.org/\nstunnel homepage\n\nhttp://www.openssl.org/\nOpenSSL project website\n",
            "subsections": []
        },
        "AUTHOR": {
            "content": "Michał Trojnara\n<Michal.Trojnara@stunnel.org>\n\n\n\n5.63                                         2022.01.18                                   stunnel(8)",
            "subsections": []
        }
    },
    "summary": "stunnel - TLS offloading and load-balancing proxy",
    "flags": [
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "Read the config file from specified file descriptor"
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "Print stunnel help menu"
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "Print stunnel version and compile time defaults"
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "Print default socket options"
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "Print supported TLS options"
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "Install NT Service"
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "Uninstall NT Service"
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "Start NT Service"
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "Stop NT Service"
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "Reload the configuration file of the running NT Service"
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "Reopen the log file of the running NT Service"
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "Exit an already started stunnel"
        },
        {
            "flag": "",
            "long": null,
            "arg": null,
            "description": "Don't display any message boxes"
        }
    ],
    "examples": [
        "In order to provide TLS encapsulation to your local imapd service, use:",
        "[imapd]",
        "accept = 993",
        "exec = /usr/sbin/imapd",
        "execArgs = imapd",
        "or in remote mode:",
        "[imapd]",
        "accept = 993",
        "connect = 143",
        "In order to let your local e-mail client connect to a TLS-enabled imapd service on another",
        "server, configure the e-mail client to connect to localhost on port 119 and use:",
        "[imap]",
        "client = yes",
        "accept = 143",
        "connect = servername:993",
        "If you want to provide tunneling to your pppd daemon on port 2020, use something like:",
        "[vpn]",
        "accept = 2020",
        "exec = /usr/sbin/pppd",
        "execArgs = pppd local",
        "pty = yes",
        "If you want to use stunnel in inetd mode to launch your imapd process, you'd use this",
        "stunnel.conf.  Note there must be no [servicename] section.",
        "exec = /usr/sbin/imapd",
        "execArgs = imapd",
        "To setup SOCKS VPN configure the following client service:",
        "[socksclient]",
        "client = yes",
        "accept = 127.0.0.1:1080",
        "connect = vpnserver:9080",
        "verifyPeer = yes",
        "CAfile = stunnel.pem",
        "The corresponding configuration on the vpnserver host:",
        "[socksserver]",
        "protocol = socks",
        "accept = 9080",
        "cert = stunnel.pem",
        "key = stunnel.key",
        "Now test your configuration on the client machine with:",
        "curl --socks4a localhost http://www.example.com/",
        "An example server mode SNI configuration:",
        "[virtual]",
        "; master service",
        "accept = 443",
        "cert =  default.pem",
        "connect = default.internal.mydomain.com:8080",
        "[sni1]",
        "; slave service 1",
        "sni = virtual:server1.mydomain.com",
        "cert = server1.pem",
        "connect = server1.internal.mydomain.com:8081",
        "[sni2]",
        "; slave service 2",
        "sni = virtual:server2.mydomain.com",
        "cert = server2.pem",
        "connect = server2.internal.mydomain.com:8082",
        "verifyPeer = yes",
        "CAfile = server2-allowed-clients.pem",
        "An example of advanced engine configuration allows for authentication with private keys",
        "stored in the Windows certificate store (Windows only).  With the CAPI engine you don't need",
        "to manually select the client key to use.  The client key is automatically selected based on",
        "the list of CAs trusted by the server.",
        "engine = capi",
        "[service]",
        "engineId = capi",
        "client = yes",
        "accept = 127.0.0.1:8080",
        "connect = example.com:8443",
        "An example of advanced engine configuration to use the certificate and the corresponding",
        "private key from a pkcs11 engine:",
        "engine = pkcs11",
        "engineCtrl = MODULEPATH:opensc-pkcs11.so",
        "engineCtrl = PIN:123456",
        "[service]",
        "engineId = pkcs11",
        "client = yes",
        "accept = 127.0.0.1:8080",
        "connect = example.com:843",
        "cert = pkcs11:token=MyToken;object=MyCert",
        "key = pkcs11:token=MyToken;object=MyKey",
        "An example of advanced engine configuration to use the certificate and the corresponding",
        "private key from a SoftHSM token:",
        "engine = pkcs11",
        "engineCtrl = MODULEPATH:softhsm2.dll",
        "engineCtrl = PIN:12345",
        "[service]",
        "engineId = pkcs11",
        "client = yes",
        "accept = 127.0.0.1:8080",
        "connect = example.com:843",
        "cert = pkcs11:token=MyToken;object=KeyCert"
    ],
    "see_also": [
        {
            "name": "tcpd",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/tcpd/8/json"
        },
        {
            "name": "inetd",
            "section": "8",
            "url": "https://www.chedong.com/phpMan.php/man/inetd/8/json"
        }
    ]
}