.\" Automatically generated by Pod::Man v1.3, Pod::Parser v1.13 .\" .\" Standard preamble: .\" ======================================================================== .de Sh \" Subsection heading .br .if t .Sp .ne 5 .PP \fB\\$1\fR .PP .. .de Sp \" Vertical space (when we can't use .PP) .if t .sp .5v .if n .sp .. .de Vb \" Begin verbatim text .ft CW .nf .ne \\$1 .. .de Ve \" End verbatim text .ft R .fi .. .\" Set up some character translations and predefined strings. \*(-- will .\" give an unbreakable dash, \*(PI will give pi, \*(L" will give a left .\" double quote, and \*(R" will give a right double quote. | will give a .\" real vertical bar. \*(C+ will give a nicer C++. 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The concept is that having non-SSL aware daemons running on your system you can easily set them up to communicate with clients over secure \s-1SSL\s0 channels. .PP \&\fBstunnel\fR can be used to add \s-1SSL\s0 functionality to commonly used \fIInetd\fR daemons like \s-1POP\-2\s0, \s-1POP\-3\s0, and \s-1IMAP\s0 servers, to standalone daemons like \&\s-1NNTP\s0, \s-1SMTP\s0 and \s-1HTTP\s0, and in tunneling \s-1PPP\s0 over network sockets without changes to the source code. .PP This product includes cryptographic software written by Eric Young (eay@cryptsoft.com) .SH "OPTIONS" .IX Header "OPTIONS" .IP "\fB[filename]\fR" 4 .IX Item "[filename]" Use specified configuration file .IP "\fB\-fd [n]\fR (Unix only)" 4 .IX Item "-fd [n] (Unix only)" Read the config file from specified file descriptor .IP "\fB\-help\fR" 4 .IX Item "-help" Print \fBstunnel\fR help menu .IP "\fB\-version\fR" 4 .IX Item "-version" Print \fBstunnel\fR version and compile time defaults .IP "\fB\-sockets\fR" 4 .IX Item "-sockets" Print default socket options .IP "\fB\-install\fR (\s-1NT/2000/XP\s0 only)" 4 .IX Item "-install (NT/2000/XP only)" Install \s-1NT\s0 Service .IP "\fB\-uninstall\fR (\s-1NT/2000/XP\s0 only)" 4 .IX Item "-uninstall (NT/2000/XP only)" Uninstall \s-1NT\s0 Service .SH "CONFIGURATION FILE" .IX Header "CONFIGURATION FILE" Each line of the configuration file can be either: .IP "\(bu" 4 an empty line (ignored) .IP "\(bu" 4 a comment starting with \*(L"#\*(R" (ignored) .IP "\(bu" 4 an \*(L"option_name = option_value\*(R" pair .IP "\(bu" 4 \&\*(L"[service_name]\*(R" indicating a start of a service definition .Sh "\s-1GLOBAL\s0 \s-1OPTIONS\s0" .IX Subsection "GLOBAL OPTIONS" .IP "\fBCApath\fR = directory" 4 .IX Item "CApath = directory" Certificate Authority directory .Sp This is the directory in which \fBstunnel\fR will look for certificates when using the \fIverify\fR. Note that the certificates in this directory should be named \s-1XXXXXXXX\s0.0 where \s-1XXXXXXXX\s0 is the hash value of the cert. .IP "\fBCAfile\fR = certfile" 4 .IX Item "CAfile = certfile" Certificate Authority file .Sp This file contains multiple \s-1CA\s0 certificates, used with the \fIverify\fR. .IP "\fBcert\fR = pemfile" 4 .IX Item "cert = pemfile" certificate chain \s-1PEM\s0 file name .Sp A \s-1PEM\s0 is always needed in server mode. Specifying this flag in client mode will use this certificate chain as a client side certificate chain. Using client side certs is optional. The certificates must be in \s-1PEM\s0 format and must be sorted starting with the certificate to the highest level (root \s-1CA\s0). .IP "\fBchroot\fR = directory (Unix only)" 4 .IX Item "chroot = directory (Unix only)" directory to chroot \fBstunnel\fR process .Sp \&\fBchroot\fR keeps \fBstunnel\fR in chrooted jail. \fICApath\fR, \fIpid\fR and \fIexec\fR are located inside the jail and the patches have to be relative to the directory specified with \fBchroot\fR. .Sp To have libwrap (\s-1TCP\s0 Wrappers) control effective in a chrooted environment you also have to copy its configuration files (/etc/hosts.allow and /etc/hosts.deny) there. .IP "\fBciphers\fR = cipherlist" 4 .IX Item "ciphers = cipherlist" Select permitted \s-1SSL\s0 ciphers .Sp A colon delimited list of the ciphers to allow in the \s-1SSL\s0 connection. For example \s-1DES\-CBC3\-SHA:IDEA\-CBC\-MD5\s0 .IP "\fBclient\fR = yes | no" 4 .IX Item "client = yes | no" client mode (remote service uses \s-1SSL\s0) .Sp default: no (server mode) .IP "\fBCRLpath\fR = directory" 4 .IX Item "CRLpath = directory" Certificate Revocation Lists directory .Sp This is the directory in which \fBstunnel\fR will look for CRLs when using the \fIverify\fR. Note that the CRLs in this directory should be named \s-1XXXXXXXX\s0.0 where \s-1XXXXXXXX\s0 is the hash value of the \s-1CRL\s0. .IP "\fBCRLfile\fR = certfile" 4 .IX Item "CRLfile = certfile" Certificate Revocation Lists file .Sp This file contains multiple CRLs, used with the \fIverify\fR. .IP "\fBdebug\fR = [facility.]level" 4 .IX Item "debug = [facility.]level" debugging level .Sp Level is a one of the syslog level names or numbers emerg (0), alert (1), crit (2), err (3), warning (4), notice (5), info (6), or debug (7). All logs for the specified level and all levels numerically less than it will be shown. Use \fBdebug = debug\fR or \&\fBdebug = 7\fR for greatest debugging output. The default is notice (5). .Sp The syslog facility 'daemon' will be used unless a facility name is supplied. (Facilities are not supported on Win32.) .Sp Case is ignored for both facilities and levels. .IP "\fB\s-1EGD\s0\fR = egd path (Unix only)" 4 .IX Item "EGD = egd path (Unix only)" path to Entropy Gathering Daemon socket .Sp Entropy Gathering Daemon socket to use to feed OpenSSL random number generator. (Available only if compiled with OpenSSL 0.9.5a or higher) .IP "\fBforeground\fR = yes | no (Unix only)" 4 .IX Item "foreground = yes | no (Unix only)" foreground mode .Sp Stay in foreground (don't fork) and log to stderr instead of via syslog (unless \fBoutput\fR is specified). .Sp default: background in daemon mode .IP "\fBkey\fR = keyfile" 4 .IX Item "key = keyfile" private key for certificate specified with \fIcert\fR option .Sp Private key is needed to authenticate certificate owner. Since this file should be kept secret it should only be readable to its owner. On Unix systems you can use the following command: .Sp .Vb 1 \& chmod 600 keyfile .Ve default: value of \fIcert\fR option .IP "\fBoptions\fR = SSL_options" 4 .IX Item "options = SSL_options" OpenSSL library options .Sp The parameter is the OpenSSL option name as described in the \&\fI\fISSL_CTX_set_options\fI\|(3ssl)\fR manual, but without \fI\s-1SSL_OP_\s0\fR prefix. Several \fIoptions\fR can be used to specify multiple options. .Sp For example for compatibility with erroneous Eudora \s-1SSL\s0 implementation the following option can be used: .Sp .Vb 1 \& options = DONT_INSERT_EMPTY_FRAGMENTS .Ve .IP "\fBoutput\fR = file" 4 .IX Item "output = file" append log messages to a file instead of using syslog .Sp /dev/stdout device can be used to redirect log messages to the standard output (for example to log them with daemontools splogger). .IP "\fBpid\fR = file (Unix only)" 4 .IX Item "pid = file (Unix only)" pid file location .Sp If the argument is empty, then no pid file will be created. .IP "\fBRNDbytes\fR = bytes" 4 .IX Item "RNDbytes = bytes" bytes to read from random seed files .Sp Number of bytes of data read from random seed files. With \s-1SSL\s0 versions less than 0.9.5a, also determines how many bytes of data are considered sufficient to seed the \s-1PRNG\s0. More recent OpenSSL versions have a builtin function to determine when sufficient randomness is available. .IP "\fBRNDfile\fR = file" 4 .IX Item "RNDfile = file" path to file with random seed data .Sp The \s-1SSL\s0 library will use data from this file first to seed the random number generator. .IP "\fBRNDoverwrite\fR = yes | no" 4 .IX Item "RNDoverwrite = yes | no" overwrite the random seed files with new random data .Sp default: yes .IP "\fBservice\fR = servicename" 4 .IX Item "service = servicename" use specified string as the service name .Sp On Unix: \fIinetd\fR mode service name for \s-1TCP\s0 Wrapper library. .Sp On \s-1NT/2000/XP:\s0 \s-1NT\s0 service name in the Control Panel. .Sp default: stunnel .IP "\fBsession\fR = timeout" 4 .IX Item "session = timeout" session cache timeout .IP "\fBsetgid\fR = groupname (Unix only)" 4 .IX Item "setgid = groupname (Unix only)" \&\fIsetgid()\fR to groupname in daemon mode and clears all other groups .IP "\fBsetuid\fR = username (Unix only)" 4 .IX Item "setuid = username (Unix only)" \&\fIsetuid()\fR to username in daemon mode .IP "\fBsocket\fR = a|l|r:option=value[:value]" 4 .IX Item "socket = a|l|r:option=value[:value]" Set an option on accept/local/remote socket .Sp The values for linger option are l_onof:l_linger. The values for time are tv_sec:tv_usec. .Sp Examples: .Sp .Vb 11 \& socket = l:SO_LINGER=1:60 \& set one minute timeout for closing local socket \& socket = r:TCP_NODELAY=1 \& turn off the Nagle algorithm for remote sockets \& socket = r:SO_OOBINLINE=1 \& place out-of-band data directly into the \& receive data stream for remote sockets \& socket = a:SO_REUSEADDR=0 \& disable address reuse (enabled by default) \& socket = a:SO_BINDTODEVICE=lo \& only accept connections on loopback interface .Ve .IP "\fBtaskbar\fR = yes | no (\s-1WIN32\s0 only)" 4 .IX Item "taskbar = yes | no (WIN32 only)" enable the taskbar icon .Sp default: yes .IP "\fBverify\fR = level" 4 .IX Item "verify = level" verify peer certificate .Sp .Vb 4 \& level 1 - verify peer certificate if present \& level 2 - verify peer certificate \& level 3 - verify peer with locally installed certificate \& default - no verify .Ve .Sh "SERVICE-LEVEL \s-1OPTIONS\s0" .IX Subsection "SERVICE-LEVEL OPTIONS" Each configuration section begins with service name in square brackets. The service name is used for libwrap (\s-1TCP\s0 Wrappers) access control and lets you distinguish \fBstunnel\fR services in your log files. .PP Note that if you wish to run \fBstunnel\fR in \fIinetd\fR mode (where it is provided a network socket by a server such as \fIinetd\fR, \fIxinetd\fR, or \fItcpserver\fR) then you should read the section entitiled \fI\s-1INETD\s0 \s-1MODE\s0\fR below. .IP "\fBaccept\fR = [host:]port" 4 .IX Item "accept = [host:]port" accept connections on specified host:port .Sp If no host specified, defaults to all \s-1IP\s0 addresses for the local host. .IP "\fBconnect\fR = [host:]port" 4 .IX Item "connect = [host:]port" connect to remote host:port .Sp If no host specified, defaults to localhost. .IP "\fBdelay\fR = yes | no" 4 .IX Item "delay = yes | no" delay \s-1DNS\s0 lookup for 'connect' option .IP "\fBexec\fR = executable_path (Unix only)" 4 .IX Item "exec = executable_path (Unix only)" execute local inetd-type program .ie n .IP "\fBexecargs\fR = $0\fR \f(CW$1\fR \f(CW$2 ... (Unix only)" 4 .el .IP "\fBexecargs\fR = \f(CW$0\fR \f(CW$1\fR \f(CW$2\fR ... (Unix only)" 4 .IX Item "execargs = $0 $1 $2 ... (Unix only)" arguments for \fIexec\fR including program name ($0) .Sp Quoting is currently not supported. Arguments are speparated with arbitrary number of whitespaces. .IP "\fBident\fR = username" 4 .IX Item "ident = username" use \s-1IDENT\s0 (\s-1RFC\s0 1413) username checking .IP "\fBlocal\fR = host" 4 .IX Item "local = host" \&\s-1IP\s0 of the outgoing interface is used as source for remote connections. Use this option to bind a static local \s-1IP\s0 address, instead. .IP "\fBprotocol\fR = proto" 4 .IX Item "protocol = proto" Negotiate \s-1SSL\s0 with specified protocol .Sp currently supported: cifs, nntp, pop3, smtp .IP "\fBpty\fR = yes | no (Unix only)" 4 .IX Item "pty = yes | no (Unix only)" allocate pseudo terminal for 'exec' option .IP "\fBTIMEOUTbusy\fR = seconds" 4 .IX Item "TIMEOUTbusy = seconds" time to wait for expected data .IP "\fBTIMEOUTclose\fR = seconds" 4 .IX Item "TIMEOUTclose = seconds" time to wait for close_notify (set to 0 for buggy \s-1MSIE\s0) .IP "\fBTIMEOUTidle\fR = seconds" 4 .IX Item "TIMEOUTidle = seconds" time to keep an idle connection .IP "\fBtransparent\fR = yes | no (Unix only)" 4 .IX Item "transparent = yes | no (Unix only)" transparent proxy mode .Sp Re-write address to appear as if wrapped daemon is connecting from the \s-1SSL\s0 client machine instead of the machine running \fBstunnel\fR. This option is only available in local mode (\fIexec\fR option) by LD_PRELOADing env.so shared library or in remote mode (\fIconnect\fR option) on Linux 2.2 kernel compiled with \fItransparent proxy\fR option and then only in server mode. Note that this option will not combine with proxy mode (\fIconnect\fR) unless the client's default route to the target machine lies through the host running \fBstunnel\fR, which cannot be localhost. .SH "RETURN VALUE" .IX Header "RETURN VALUE" \&\fBstunnel\fR returns zero on success, non-zero on error. .SH "EXAMPLES" .IX Header "EXAMPLES" In order to provide \s-1SSL\s0 encapsulation to your local \fIimapd\fR service, use .PP .Vb 4 \& [imapd] \& accept = 993 \& exec = /usr/sbin/imapd \& execargs = imapd .Ve If you want to provide tunneling to your \fIpppd\fR daemon on port 2020, use something like .PP .Vb 5 \& [vpn] \& accept = 2020 \& exec = /usr/sbin/pppd \& execargs = pppd local \& pty = yes .Ve If you want to use \fBstunnel\fR in \fIinetd\fR mode to launch your imapd process, you'd use this \fIstunnel.conf\fR. Note there must be no \fI[service_name]\fR section. .PP .Vb 2 \& exec = /usr/sbin/imapd \& execargs = imapd .Ve .SH "FILES" .IX Header "FILES" .IP "\fIstunnel.conf\fR" 4 .IX Item "stunnel.conf" \&\fBstunnel\fR configuration file .IP "\fIstunnel.pem\fR" 4 .IX Item "stunnel.pem" \&\fBstunnel\fR certificate and private key .SH "BUGS" .IX Header "BUGS" Option \fIexecargs\fR does not support quoting. .SH "RESTRICTIONS" .IX Header "RESTRICTIONS" \&\fBstunnel\fR cannot be used for the \s-1FTP\s0 daemon because of the nature of the \s-1FTP\s0 protocol which utilizes multiple ports for data transfers. There are available \s-1SSL\s0 enabled versions of \s-1FTP\s0 and telnet daemons, however. .SH "NOTES" .IX Header "NOTES" .Sh "\s-1INETD\s0 \s-1MODE\s0" .IX Subsection "INETD MODE" The most common use of \fBstunnel\fR is to listen on a network port and establish communication with either a new port via the connect option, or a new program via the \fIexec\fR option. However there is a special case when you wish to have some other program accept incoming connections and launch \fBstunnel\fR, for example with \fIinetd\fR, \fIxinetd\fR, or \fItcpserver\fR. .PP For example, if you have the following line in \fIinetd.conf\fR: .PP .Vb 1 \& imaps stream tcp nowait root /usr/sbin/stunnel stunnel /etc/stunnel/imaps.conf .Ve In these cases, the \fIinetd\fR\-style program is responsible for binding a network socket (\fIimaps\fR above) and handing it to \fBstunnel\fR when a connection is received. Thus you do not want \fBstunnel\fR to have any \fIaccept\fR option. All the \fIService Level Options\fR should be placed in the global options section, and no \fI[service_name]\fR section will be present. See the \fI\s-1EXAMPLES\s0\fR section for example configurations. .Sh "\s-1CERTIFICATES\s0" .IX Subsection "CERTIFICATES" Each \s-1SSL\s0 enabled daemon needs to present a valid X.509 certificate to the peer. It also needs a private key to decrypt the incoming data. The easiest way to obtain a certificate and a key is to generate them with the free \fIOpenSSL\fR package. You can find more information on certificates generation on pages listed below. .PP Two things are important when generating certificate-key pairs for \&\fBstunnel\fR. The private key cannot be encrypted, because the server has no way to obtain the password from the user. To produce an unencrypted key add the \fI\-nodes\fR option when running the \fBreq\fR command from the \fIOpenSSL\fR kit. .PP The order of contents of the \fI.pem\fR file is also important. It should contain the unencrypted private key first, then a signed certificate (not certificate request). There should be also empty lines after certificate and private key. Plaintext certificate information appended on the top of generated certificate should be discarded. So the file should look like this: .PP .Vb 8 \& -----BEGIN RSA PRIVATE KEY----- \& [encoded key] \& -----END RSA PRIVATE KEY----- \& [empty line] \& -----BEGIN CERTIFICATE----- \& [encoded certificate] \& -----END CERTIFICATE----- \& [empty line] .Ve .Sh "\s-1RANDOMNESS\s0" .IX Subsection "RANDOMNESS" \&\fBstunnel\fR needs to seed the \s-1PRNG\s0 (pseudo random number generator) in order for \s-1SSL\s0 to use good randomness. The following sources are loaded in order until sufficient random data has been gathered: .IP "\(bu" 4 The file specified with the \fIRNDfile\fR flag. .IP "\(bu" 4 The file specified by the \s-1RANDFILE\s0 environment variable, if set. .IP "\(bu" 4 The file .rnd in your home directory, if \s-1RANDFILE\s0 not set. .IP "\(bu" 4 The file specified with '\-\-with\-random' at compile time. .IP "\(bu" 4 The contents of the screen if running on Windows. .IP "\(bu" 4 The egd socket specified with the \fI\s-1EGD\s0\fR flag. .IP "\(bu" 4 The egd socket specified with '\-\-with\-egd\-sock' at compile time. .IP "\(bu" 4 The /dev/urandom device. .PP With recent (>=OpenSSL 0.9.5a) version of \s-1SSL\s0 it will stop loading random data automatically when sufficient entropy has been gathered. With previous versions it will continue to gather from all the above sources since no \s-1SSL\s0 function exists to tell when enough data is available. .PP Note that on Windows machines that do not have console user interaction (mouse movements, creating windows, etc) the screen contents are not variable enough to be sufficient, and you should provide a random file for use with the \fIRNDfile\fR flag. .PP Note that the file specified with the \fIRNDfile\fR flag should contain random data \*(-- that means it should contain different information each time \fBstunnel\fR is run. This is handled automatically unless the \fIRNDoverwrite\fR flag is used. If you wish to update this file manually, the \fIopenssl rand\fR command in recent versions of OpenSSL, would be useful. .PP One important note \*(-- if /dev/urandom is available, OpenSSL has a habit of seeding the \s-1PRNG\s0 with it even when checking the random state, so on systems with /dev/urandom you're likely to use it even though it's listed at the very bottom of the list above. This isn't \fBstunnel's\fR behaviour, it's OpenSSLs. .SH "SEE ALSO" .IX Header "SEE ALSO" .IP "\fItcpd\fR\|(8)" 4 .IX Item "tcpd" access control facility for internet services .IP "\fIinetd\fR\|(8)" 4 .IX Item "inetd" internet ``super\-server'' .IP "\fIhttp://stunnel.mirt.net/\fR" 4 .IX Item "http://stunnel.mirt.net/" \&\fBstunnel\fR homepage .IP "\fIhttp://www.stunnel.org/\fR" 4 .IX Item "http://www.stunnel.org/" \&\fBstunnel\fR Frequently Asked Questions .IP "\fIhttp://www.openssl.org/\fR" 4 .IX Item "http://www.openssl.org/" OpenSSL project website .SH "AUTHOR" .IX Header "AUTHOR" .IP "Michal Trojnara" 4 .IX Item "Michal Trojnara" <\fIMichal.Trojnara@mirt.net\fR>