365 lines
16 KiB
Plaintext
365 lines
16 KiB
Plaintext
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// Examples for using socat (and filan)
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//"$" means normal user, "#" requires privileges, "//" starts a comment
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///////////////////////////////////////////////////////////////////////////////
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// similar to netcat
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// connect to 10.1.1.1 on port 80 and relay to and from stdio
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$ socat - TCP:10.1.1.1:80 # similar to "netcat 10.1.1.1 80"
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// listen on port 25, wait for an incoming connection, use CR+NL on this
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// connection, relay data to and from stdio;
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// then emulate a mailserver by hand :-)
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# socat - TCP-LISTEN:25,crlf
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// listen on port 25, wait for an incoming connection, use CR+NL on this
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// connection, relay data to and from stdio, but have line editing and history;
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// then emulate a mailserver by hand :-)
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# socat readline TCP-LISTEN:25,crlf
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// provide a transient history enabled front end to stupid line based
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// interactive programs
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$ socat readline exec:"nslookup",pty,ctty,setsid,echo=0
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// same works for ftp (but password is not hidden)
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// you may also use a file based history list
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$ socat readline,history=.nslookup_hist exec:"nslookup",pty,ctty,setsid,echo=0
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// using ~ as abbreviation for $HOME does not work!
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// poor mans 'telnetd' replacement
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# socat tcp-l:2023,reuseaddr,fork exec:/bin/login,pty,setsid,setpgid,stderr,ctty
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// and here an appropriate client:
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$ socat -,raw,echo=0 tcp:172.16.181.130:2023
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// use ssl with client and server certificate for improved security;
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// replace /bin/login by /bin/bash when using SSL client authentication, can be
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// run without root then
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// this is a cool trick, proposed by Christophe Lohr, to dump communications to
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// two files; it would also work for other manipulations (recode, compress...)
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// and it might also work with netcat ;-)
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$ socat TCP-LISTEN:5555 SYSTEM:'tee l2r | socat - "TCP:remote:5555" | tee r2l'
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///////////////////////////////////////////////////////////////////////////////
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// emergence solution because usleep(1) is not always available
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// this will "sleep" for 0.1s
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$ socat -T 0.1 pipe pipe
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///////////////////////////////////////////////////////////////////////////////
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// a very primitive HTTP/1.0 echo server (problems: sends reply headers before
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// request; hangs if client does not shutdown - HTTP keep-alive)
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// wait for a connection on port 8000; do not wait for request, but immediately
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// start a shell that sends reply headers and an empty line; then echo all
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// incoming data back to client
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$ socat TCP-LISTEN:8000,crlf SYSTEM:"echo HTTP/1.0 200; echo Content-Type\: text/plain; echo; cat"
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// a less primitive HTTP echo server that sends back not only the reqest but
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// also server and client address and port. Might have portability issues with
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// echo
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./socat -T 1 -d -d tcp-l:10081,reuseaddr,fork,crlf system:"echo -e \"\\\"HTTP/1.0 200 OK\\\nDocumentType: text/html\\\n\\\n<html>date: \$\(date\)<br>server:\$SOCAT_SOCKADDR:\$SOCAT_SOCKPORT<br>client: \$SOCAT_PEERADDR:\$SOCAT_PEERPORT\\\n<pre>\\\"\"; cat; echo -e \"\\\"\\\n</pre></html>\\\"\""
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///////////////////////////////////////////////////////////////////////////////
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// for communicating with an attached modem, I had reasonable results with
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// following command line. Required privileges depend on device mode.
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// after leaving socat, type "sane".
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// replace /dev/ttyS0 by the correct serial line or with /dev/modem
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$ socat readline /dev/ttyS0,raw,echo=0,crlf
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// or
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$ socat readline /dev/ttyS0,raw,echo=0,crlf,nonblock
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// then enter "at$"
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///////////////////////////////////////////////////////////////////////////////
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// relay TCP port 80 from everywhere (internet, intranet, dmz) through your
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// firewall to your DMZ webserver (like plug-gw)
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// listen on port 80; whenever a connection is made, fork a new process (parent
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// process keeps accepting connections), su to nobody, and connect to
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// www.dmz.mydomain.org on port 80.
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// attention: this is a substitute for a reverse proxy without providing
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// application level security.
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# socat TCP-LISTEN:80,reuseaddr,fork,su=nobody TCP:www.dmz.mydomain.org:80
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// Note: parent process keeps running as root, su after forking
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///////////////////////////////////////////////////////////////////////////////
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// relay mail from your DMZ server through your firewall.
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// accept connections only on dmz interface and allow connections only from
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// smtp.dmz.mydomain.org.
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// the advantages over plug-gw and other relays are:
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// * you can bind to an IP address (even an alias), therefore enhance security
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// * in your OS you can create several IP aliases and bind another socat daemon
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// to each, making several application servers addressable
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// * lots of options, like switching user, chroot, IP performance tuning
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// * no need for inetd
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# socat -lm -d -d TCP-LISTEN:25,bind=fw.dmz.mydomain.org,fork,su=nobody,range=smtp.dmz.mydomain.org/32 TCP:smtp.intra.mydomain.org:25
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///////////////////////////////////////////////////////////////////////////////
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// convert line terminator in ascii streams, stdin to stdout
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// use unidirectional mode, convert nl to crnl
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$ socat -u - -,crlf
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// or cr to nl
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$ socat -u -,cr -
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// save piped data similar to 'tee':
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// copies stdin to stdout, but writes everything to the file too
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$ socat -,echo=0 open:/tmp/myfile,create,trunc,ignoreeof!!/tmp/myfile
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///////////////////////////////////////////////////////////////////////////////
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// intrusion testing
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// found an XWindow Server behind IP filters with FTP data hole? (you are
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// lucky!)
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// prepare your host:
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# rm -f /tmp/.X11-unix/X1
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// relay a pseudo display :1 on your machine to victim:0
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# socat UNIX-LISTEN:/tmp/.X11-unix/X1,fork TCP:host.victim.org:6000,sp=20 &
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// and try to take a screendump (must be very lucky - when server has not even
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// host based authentication!)
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# xwd -root -display :1 -silent >victim.xwd
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// you sit behind a socks firewall that has IP filters but lazily allows socks
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// connections to loopback and has only host based X11 security.
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// like above, but from your inside client:
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# socat UNIX-LISTEN:/tmp/.X11-unix/X1,fork SOCKS4:firewall:loopback:6000
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// or for the HTTP proxy:
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# socat UNIX-LISTEN:/tmp/.X11-unix/X1,fork PROXY:firewall:loopback:6000
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///////////////////////////////////////////////////////////////////////////////
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// forms of stdin with stdout, all equivalent
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$ socat echo -
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$ socat echo STDIO
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$ socat echo STDIN!!STDOUT
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$ socat echo STDIO!!STDIO
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$ socat echo -!!-
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$ socat echo FD:0!!FD:1
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$ socat echo 0!!1
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$ socat echo /dev/stdin!!/dev/stdout // if your OS provides these
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///////////////////////////////////////////////////////////////////////////////
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// some echo address examples
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$ socat - PIPE
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$ socat - PIPE:/tmp/pipi // other version of echo
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$ socat - PIPE:/tmp/pipi,nonblock!!/tmp/pipi // other version of echo
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$ socat - EXEC:/bin/cat // another echo
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$ socat - SYSTEM:/bin/cat // another echo
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$ socat - TCP:loopback:7 // if inetd echo/TCP service activated
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$ socat - UDP:loopback:7 // if inetd echo/UDP service activated
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$ socat - /tmp/hugo,trunc,ignoreeof!!/tmp/hugo // with delay
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$ socat - UDP:loopback:2000,bind=:2000 // self "connection"
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$ socat - TCP:loopback:2000,bind=:2000 // Linux bug?
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# socat - IP:loopback:222 // raw protocol, self "connected" (attention,
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// Linux might drop packets with less than 8 bytes payload)
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///////////////////////////////////////////////////////////////////////////////
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// unidirectional data transfer
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$ socat -u - -
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// like "tail -f", but start with showing all file contents
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$ socat -u FILE:/var/log/syslog.debug,ignoreeof -
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// like "tail -f", but do not show existing file contents
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$ socat -u FILE:/var/log/syslog.debug,ignoreeof,seek-end -
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// write to new file, create with given permission and group (must be member) - race condition with group!!!
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$ socat -u - CREATE:/tmp/outfile1,group=floppy,perm=0640
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//
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// for an existing file /tmp/outfile1
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# socat -u - FILE:/tmp/outfile1,group=floppy,perm=0700,user=4321
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///////////////////////////////////////////////////////////////////////////////
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// file handling
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$ socat - FILE:/tmp/outfile1,ignoreeof!!FILE:/tmp/outfile1,append // prints outfile1, then echoes input and protocols into file (appends to old data)
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///////////////////////////////////////////////////////////////////////////////
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// unix socket handling
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// create a listening unix socket
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$ rm -f /tmp/mysocket; socat UNIX-LISTEN:/tmp/mysocket -
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// from another terminal, connect to this socket
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$ socat UNIX:/tmp/mysocket -
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// then transfer data bidirectionally
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///////////////////////////////////////////////////////////////////////////////
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// transport examples
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// socks relay (externally socksify applications);
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// your ssh client and OS are not socksified, but you want to pass a socks
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// server with ssh:
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$ socat TCP-LISTEN:10022,fork SOCKS4:socks.mydomain.org:ssh-serv:22
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$ ssh -p 10022 loopback
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// or better define a ProxyCommand in ~/.ssh/config:
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ProxyCommand socat - SOCKS:socks.mydomain.org:%h:%p
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// and with proxy:
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ProxyCommand socat - PROXY:proxy.mydomain.org:%h:%p,proxyport=8000
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///////////////////////////////////////////////////////////////////////////////
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// application examples
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// run sendmail daemon with your favorite network options
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# socat TCP-LISTEN:25,fork,ip-ttl=4,ip-tos=7,tcp-maxseg=576 EXEC:"/usr/sbin/sendmail -bs",nofork
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// local mail delivery over UNIX socket - no SUID program required
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# socat UNIX-LISTEN:/tmp/postoffice,fork,perm-early=0666 EXEC:"/usr/sbin/sendmail -bs"
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$ socat - /tmp/postoffice
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///////////////////////////////////////////////////////////////////////////////
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// uses of filan
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// see what your operating system opens for you
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$ filan
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// or if that was too detailled
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$ filan -s
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// see what file descriptors are passed via exec function
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$ socat - EXEC:filan,nofork
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$ socat - EXEC:filan
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$ socat - EXEC:filan,pipes,stderr
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$ socat - EXEC:filan,pipes
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$ socat - EXEC:filan,pty
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// see what's done by your shell and with option "pipes"
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$ socat - SYSTEM:filan,pipes
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// see if gdb gives you an equivalent environment or opens some files for your program
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$ gdb ./filan
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(gdb) r
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(gdb) r -s
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///////////////////////////////////////////////////////////////////////////////
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// want to use chat from the ppp package?
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// note: some OS's do not need "-e" for echo to print control characters
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// note: chat might send bytes one by one
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// with AIX, a similar program is available under the name "pppdial"
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$ socat -d -d tcp:localhost:25,crlf,nodelay exec:'/usr/sbin/chat -v -s "\"220 \"" "\"HELO loopback\"" "\"250 \"" "\"MAIL FROM: <hugo@localhost>\"" "\"250 \"" "\"RCPT TO: root\"" "\"250 \"" "\"DATA\"" "\"354 \"" "\"test1'$(echo -e "\r.")'\"" "\"250 \"" "\"QUIT\"" "\"221 \""',pty,echo=0,cr
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//////////////////////////////////////////////////////////////////////////////
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// IP6
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# socat readline TCP6:[::1]:21 # if your inetd/ftp is listening on ip6
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///////////////////////////////////////////////////////////////////////////////
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// application server solutions
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// run a program (here: /bin/sh) chrooted, unprivileged;
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// parent process stays in real / running as root
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# socat -d -d - EXEC:/bin/sh,chroot=/home/sandbox,su=sandbox,pty
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// make a program available on the network chrooted, unprivileged;
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// parent process stays in / running as root
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// script path is already chrooted
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# ./socat -lm -d -d TCP-LISTEN:5555,fork EXEC:/bin/myscript,chroot=/home/sandbox,su=sandbox,pty,stderr
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// to avoid terminal problems, you might - instead of telnet - connect using
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$ socat -,icanon=0,echo=0 tcp:target:5555; reset
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// access local display from ssh server, when ssh port forwarding is disabled
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// socat must be installed on ssh server host
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// might have to use xauth...
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// this example is one-shot because ssh can handle only one channel
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xterm1$ socat -d -d exec:"ssh www.dest-unreach.org rm -f /tmp/.X11-unix/X9; ~/bin/socat -d -d unix-l\:/tmp/.X11-unix/X9\,fork -" unix:/tmp/.X11-unix/X0
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xterm2$ ssh target
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target$ DISPLAY=:9 myxapplication
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// touch with perms:
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// no race condition for perms (applied with creat() call)
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$ socat -u /dev/null creat:/tmp/tempfile,perm=0600
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// touch with owner and perms:
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// race condition before changing owner, but who cares - only root may access
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# socat -u /dev/null creat:/tmp/tempfile,user=user1,perm=0600
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// invoke an interactive ssh with exec
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// first example passes control chars (^C etc.) to remote server as usual
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socat -,echo=0,raw exec:'ssh server',pty,setsid,ctty
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// second example interprets control chars on local command line
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socat -,echo=0,icanon=0 exec:'ssh server',pty,setsid,ctty
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// afterwards, type "reset"!
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// convince ssh to provide an "interactive" shell to your script
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// three main versions for entering password:
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// 1) from your TTY; have 10 seconds to enter password:
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(sleep 10; echo "ls"; sleep 1) |socat - exec:'ssh server',pty
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// 2) from XWindows (DISPLAY !); again 10 seconds
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(sleep 10; echo "ls"; sleep 1) |socat - exec:'ssh server',pty,setsid
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// 3) from script
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(sleep 5; echo PASSWORD; echo ls; sleep 1) |./socat - exec:'ssh server',pty,setsid,ctty
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// download with proxy CONNECT
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// use echo -e if required for \n
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$ (echo -e "CONNECT 128.129.130.131:80 HTTP/1.0\n"; sleep 5; echo -e "GET
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/download/file HTTP/1.0\n"; sleep 10) |socat -d -d -t 3600 - tcp:proxy:8080,crlf
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// retrieve a file from an sshd site with sourceforge style entry menu;
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// fill in your personal values; cat lets you enter your password (will be
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// visible on screen)
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$ (sleep 10; read pass; echo $pass; sleep 10; echo M; sleep 5; echo cat FILENAME; sleep 10) |./socat -d -d -ly - EXEC:'ssh -c 3des -l USER cf.sourceforge.net',pty,setsid,ctty |tee FILENAME
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// multicast community on local network: start the following command on all
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// participating hosts; like a conference call:
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# socat -d -d -d -d - udp-datagram:224.0.0.2:6666,bind=:6666,ip-add-membership=224.0.0.2:eth0,bindtodevice=eth0
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// or
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$ socat -d -d -d -d - udp-datagram:224.0.0.2:6666,bind=:6666,ip-add-membership=224.0.0.2:eth0
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// possible reasons for failure:
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// iptables or other filters (open your filters as required)
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// packets leave via wrong interface (set route: ...)
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// socket bound to specific address
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//=============================================================================
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// GENERIC FUNCTION CALLS
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// ioctl(): open CD drive (given value valid on Linux)
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// on my Linux system I find in /usr/include/linux/cdrom.h the define:
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// #define CDROMEJECT 0x5309 /* Ejects the cdrom media */
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// the following command makes something like ioctl(fd, CDROMEJECT, NULL)
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// (don't care about the read error):
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$ socat /dev/cdrom,o-nonblock,ioctl-void=0x5309 -
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// setsockopt(): SO_REUSEADDR
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// the following command performs - beyond lots of overhead - something like:
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// myint=1; setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &myint, sizeof(myint))
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$ socat -u udp-recv:7777,setsockopt-int=1:2:1 -
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// setsockopt(): SO_BINDTODEVICE
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// ways to apply SO_BINDTODEVICE without using the special socat address option
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// so-bindtodevice:
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// with string argument:
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$ sudo ./socat tcp-l:7777,setsockopt-string=1:25:eth0 pipe
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// with binary argument:
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$ sudo ./socat tcp-l:7777,setsockopt-bin=1:25:x6574683000 pipe
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===============================================================================
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// not tested, just ideas, or have problems
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// traverse firewall for making internal telnet server accessible for outside
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// telnet client, when only outbound traffic (syn-filter) is allowed:
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// on external client run "double server". this process waits for a
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// connection from localhost on port 10023, and, when it is established, waits
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// for a connection from anywhere to port 20023:
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ext$ socat -d TCP-LISTEN:10023,range=localhost TCP-LISTEN:20023
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// on internal server run double client:
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int$ socat -d TCP:localhost:23 TCP:extclient:10023
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// or, with socks firewall:
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int$ socat -d TCP:localhost:23 SOCKS:socksserver:extclient:10023
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// login with:
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ext$ telnet localhost 20023
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// you can make a double server capable of handling multiple instances:
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ext$ socat -d TCP-LISTEN:10023,range=localhost,fork TCP-LISTEN:20023,reuseaddr
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// access remote display via ssh, when ssh port forwarding is disabled
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$ socat -d -d EXEC:"ssh target socat - UNIX:/tmp/.X11-unix/X0" TCP-LISTEN:6030
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$ xclock -display localhost:30
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// relay multiple webserver addresses through your firewall into your DMZ:
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// make IP aliases on your firewall, and then:
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# socat -d -d TCP-L:80,bind=fw-addr1,fork TCP:dmz-www1:80
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# socat -d -d TCP-L:80,bind=fw-addr2,fork TCP:dmz-www2:80
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// and for improved security:
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# socat -d -d TCP-L:80,bind=fw-addr3,su=nobody,fork TCP:dmz-www3:80
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// proxy an arbitrary IP protocol over your firewall (answers won't work)
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# socat -d -d IP:0.0.0.0:150,bind=fwnonsec IP:sec-host:150,bind=fwsec
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// proxy an unsupported IP protocol over your firewall, point to point
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// end points see firewall interfaces as IP peers!
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# socat -d -d IP:nonsec-host:150,bind=fwnonsec IP:sec-host:150,bind=fwsec
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// note that, for IPsec, you might face problems that are known with NAT
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