Add netcat package

9 years ago · 9d57b270c2
2 changed files with 556 additions and 0 deletions
--- a/packages/netcat/build.sh
+++ b/packages/netcat/build.sh
@ -0,0 +1,18 @@
 TERMUX_PKG_HOMEPAGE=http://www.openbsd.org/cgi-bin/man.cgi/OpenBSD-current/man1/nc.1
 TERMUX_PKG_DESCRIPTION="Utility for reading from and writing to connections using TCP or UDP"
 TERMUX_PKG_VERSION=1.103
 _COMMIT=b023a43765b15f0b0fd5b52b7d8021f515c59c23
 TERMUX_PKG_SRCURL=https://github.com/android/platform_external_netcat/archive/${_COMMIT}.zip
 TERMUX_PKG_FOLDERNAME=platform_external_netcat-$_COMMIT
 termux_step_make () {
 	return
 }
 termux_step_make_install () {
 	cd $TERMUX_PKG_SRCDIR
 	CFLAGS+=" -DANDROID=1"
 	$CC $CFLAGS $LDFLAGS *.c -o $TERMUX_PREFIX/bin/nc
 	cp $TERMUX_PKG_BUILDER_DIR/nc.1 $TERMUX_PREFIX/share/man/man1/
 }
--- a/packages/netcat/nc.1
+++ b/packages/netcat/nc.1
@ -0,0 +1,538 @@
 .\"     $OpenBSD: nc.1,v 1.60 2012/02/07 12:11:43 lum Exp $
 .\"
 .\" Copyright (c) 1996 David Sacerdote
 .\" All rights reserved.
 .\"
 .\" Redistribution and use in source and binary forms, with or without
 .\" modification, are permitted provided that the following conditions
 .\" are met:
 .\" 1. Redistributions of source code must retain the above copyright
 .\"    notice, this list of conditions and the following disclaimer.
 .\" 2. Redistributions in binary form must reproduce the above copyright
 .\"    notice, this list of conditions and the following disclaimer in the
 .\"    documentation and/or other materials provided with the distribution.
 .\" 3. The name of the author may not be used to endorse or promote products
 .\"    derived from this software without specific prior written permission
 .\"
 .\" THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
 .\" IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
 .\" OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
 .\" IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
 .\" INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
 .\" NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
 .\" DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
 .\" THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
 .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
 .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 .\"
 .Dd $Mdocdate: February 7 2012 $
 .Dt NC 1
 .Os
 .Sh NAME
 .Nm nc
 .Nd arbitrary TCP and UDP connections and listens
 .Sh SYNOPSIS
 .Nm nc
 .Bk -words
 .Op Fl 46bCDdhklnrStUuvZz
 .Op Fl I Ar length
 .Op Fl i Ar interval
 .Op Fl O Ar length
 .Op Fl P Ar proxy_username
 .Op Fl p Ar source_port
 .Op Fl q Ar seconds
 .Op Fl s Ar source
 .Op Fl T Ar toskeyword
 .Op Fl V Ar rtable
 .Op Fl w Ar timeout
 .Op Fl X Ar proxy_protocol
 .Oo Xo
 .Fl x Ar proxy_address Ns Oo : Ns
 .Ar port Oc
 .Xc Oc
 .Op Ar destination
 .Op Ar port
 .Ek
 .Sh DESCRIPTION
 The
 .Nm
 (or
 .Nm netcat )
 utility is used for just about anything under the sun involving TCP,
 UDP, or
 .Ux Ns -domain
 sockets.
 It can open TCP connections, send UDP packets, listen on arbitrary
 TCP and UDP ports, do port scanning, and deal with both IPv4 and
 IPv6.
 Unlike
 .Xr telnet 1 ,
 .Nm
 scripts nicely, and separates error messages onto standard error instead
 of sending them to standard output, as
 .Xr telnet 1
 does with some.
 .Pp
 Common uses include:
 .Pp
 .Bl -bullet -offset indent -compact
 .It
 simple TCP proxies
 .It
 shell-script based HTTP clients and servers
 .It
 network daemon testing
 .It
 a SOCKS or HTTP ProxyCommand for
 .Xr ssh 1
 .It
 and much, much more
 .El
 .Pp
 The options are as follows:
 .Bl -tag -width Ds
 .It Fl 4
 Forces
 .Nm
 to use IPv4 addresses only.
 .It Fl 6
 Forces
 .Nm
 to use IPv6 addresses only.
 .It Fl b
 Allow broadcast.
 .It Fl C
 Send CRLF as line-ending.
 .It Fl D
 Enable debugging on the socket.
 .It Fl d
 Do not attempt to read from stdin.
 .It Fl h
 Prints out
 .Nm
 help.
 .It Fl I Ar length
 Specifies the size of the TCP receive buffer.
 .It Fl i Ar interval
 Specifies a delay time interval between lines of text sent and received.
 Also causes a delay time between connections to multiple ports.
 .It Fl k
 Forces
 .Nm
 to stay listening for another connection after its current connection
 is completed.
 It is an error to use this option without the
 .Fl l
 option.
 .It Fl l
 Used to specify that
 .Nm
 should listen for an incoming connection rather than initiate a
 connection to a remote host.
 It is an error to use this option in conjunction with the
 .Fl p ,
 .Fl s ,
 or
 .Fl z
 options.
 Additionally, any timeouts specified with the
 .Fl w
 option are ignored.
 .It Fl n
 Do not do any DNS or service lookups on any specified addresses,
 hostnames or ports.
 .It Fl O Ar length
 Specifies the size of the TCP send buffer.
 .It Fl P Ar proxy_username
 Specifies a username to present to a proxy server that requires authentication.
 If no username is specified then authentication will not be attempted.
 Proxy authentication is only supported for HTTP CONNECT proxies at present.
 .It Fl p Ar source_port
 Specifies the source port
 .Nm
 should use, subject to privilege restrictions and availability.
 .It Fl q Ar seconds
 after EOF on stdin, wait the specified number of seconds and then quit. If
 .Ar seconds
 is negative, wait forever.
 .It Fl r
 Specifies that source and/or destination ports should be chosen randomly
 instead of sequentially within a range or in the order that the system
 assigns them.
 .It Fl S
 Enables the RFC 2385 TCP MD5 signature option.
 .It Fl s Ar source
 Specifies the IP of the interface which is used to send the packets.
 For
 .Ux Ns -domain
 datagram sockets, specifies the local temporary socket file
 to create and use so that datagrams can be received.
 It is an error to use this option in conjunction with the
 .Fl l
 option.
 .It Fl T Ar toskeyword
 Change IPv4 TOS value.
 .Ar toskeyword
 may be one of
 .Ar critical ,
 .Ar inetcontrol ,
 .Ar lowcost ,
 .Ar lowdelay ,
 .Ar netcontrol ,
 .Ar throughput ,
 .Ar reliability ,
 or one of the DiffServ Code Points:
 .Ar ef ,
 .Ar af11 ... af43 ,
 .Ar cs0 ... cs7 ;
 or a number in either hex or decimal.
 .It Fl t
 Causes
 .Nm
 to send RFC 854 DON'T and WON'T responses to RFC 854 DO and WILL requests.
 This makes it possible to use
 .Nm
 to script telnet sessions.
 .It Fl U
 Specifies to use
 .Ux Ns -domain
 sockets.
 .It Fl u
 Use UDP instead of the default option of TCP.
 For
 .Ux Ns -domain
 sockets, use a datagram socket instead of a stream socket.
 If a
 .Ux Ns -domain
 socket is used, a temporary receiving socket is created in
 .Pa /tmp
 unless the
 .Fl s
 flag is given.
 .It Fl V Ar rtable
 Set the routing table to be used.
 The default is 0.
 .It Fl v
 Have
 .Nm
 give more verbose output.
 .It Fl w Ar timeout
 Connections which cannot be established or are idle timeout after
 .Ar timeout
 seconds.
 The
 .Fl w
 flag has no effect on the
 .Fl l
 option, i.e.\&
 .Nm
 will listen forever for a connection, with or without the
 .Fl w
 flag.
 The default is no timeout.
 .It Fl X Ar proxy_protocol
 Requests that
 .Nm
 should use the specified protocol when talking to the proxy server.
 Supported protocols are
 .Dq 4
 (SOCKS v.4),
 .Dq 5
 (SOCKS v.5)
 and
 .Dq connect
 (HTTPS proxy).
 If the protocol is not specified, SOCKS version 5 is used.
 .It Xo
 .Fl x Ar proxy_address Ns Oo : Ns
 .Ar port Oc
 .Xc
 Requests that
 .Nm
 should connect to
 .Ar destination
 using a proxy at
 .Ar proxy_address
 and
 .Ar port .
 If
 .Ar port
 is not specified, the well-known port for the proxy protocol is used (1080
 for SOCKS, 3128 for HTTPS).
 .It Fl Z
 DCCP mode.
 .It Fl z
 Specifies that
 .Nm
 should just scan for listening daemons, without sending any data to them.
 It is an error to use this option in conjunction with the
 .Fl l
 option.
 .El
 .Pp
 .Ar destination
 can be a numerical IP address or a symbolic hostname
 (unless the
 .Fl n
 option is given).
 In general, a destination must be specified,
 unless the
 .Fl l
 option is given
 (in which case the local host is used).
 For
 .Ux Ns -domain
 sockets, a destination is required and is the socket path to connect to
 (or listen on if the
 .Fl l
 option is given).
 .Pp
 .Ar port
 can be a single integer or a range of ports.
 Ranges are in the form nn-mm.
 In general,
 a destination port must be specified,
 unless the
 .Fl U
 option is given.
 .Sh CLIENT/SERVER MODEL
 It is quite simple to build a very basic client/server model using
 .Nm .
 On one console, start
 .Nm
 listening on a specific port for a connection.
 For example:
 .Pp
 .Dl $ nc -l 1234
 .Pp
 .Nm
 is now listening on port 1234 for a connection.
 On a second console
 .Pq or a second machine ,
 connect to the machine and port being listened on:
 .Pp
 .Dl $ nc 127.0.0.1 1234
 .Pp
 There should now be a connection between the ports.
 Anything typed at the second console will be concatenated to the first,
 and vice-versa.
 After the connection has been set up,
 .Nm
 does not really care which side is being used as a
 .Sq server
 and which side is being used as a
 .Sq client .
 The connection may be terminated using an
 .Dv EOF
 .Pq Sq ^D .
 .Pp
 There is no
 .Fl c
 or
 .Fl e
 option in this netcat, but you still can execute a command after connection
 being established by redirecting file descriptors. Be cautious here because
 opening a port and let anyone connected execute arbitrary command on your
 site is DANGEROUS. If you really need to do this, here is an example:
 .Pp
 On
 .Sq server
 side:
 .Pp
 .Dl $ rm -f /tmp/f; mkfifo /tmp/f
 .Dl $ cat /tmp/f | /bin/sh -i 2>&1 | nc -l 127.0.0.1 1234 > /tmp/f
 .Pp
 On
 .Sq client
 side:
 .Pp
 .Dl $ nc host.example.com 1234
 .Dl $ (shell prompt from host.example.com)
 .Pp
 By doing this, you create a fifo at /tmp/f and make nc listen at port 1234
 of address 127.0.0.1 on
 .Sq server
 side, when a
 .Sq client
 establishes a connection successfully to that port, /bin/sh gets executed
 on
 .Sq server
 side and the shell prompt is given to
 .Sq client
 side.
 .Pp
 When connection is terminated,
 .Nm
 quits as well. Use
 .Fl k
 if you want it keep listening, but if the command quits this option won't
 restart it or keep
 .Nm
 running. Also don't forget to remove the file descriptor once you don't need
 it anymore:
 .Pp
 .Dl $ rm -f /tmp/f
 .Pp
 .Sh DATA TRANSFER
 The example in the previous section can be expanded to build a
 basic data transfer model.
 Any information input into one end of the connection will be output
 to the other end, and input and output can be easily captured in order to
 emulate file transfer.
 .Pp
 Start by using
 .Nm
 to listen on a specific port, with output captured into a file:
 .Pp
 .Dl $ nc -l 1234 \*(Gt filename.out
 .Pp
 Using a second machine, connect to the listening
 .Nm
 process, feeding it the file which is to be transferred:
 .Pp
 .Dl $ nc host.example.com 1234 \*(Lt filename.in
 .Pp
 After the file has been transferred, the connection will close automatically.
 .Sh TALKING TO SERVERS
 It is sometimes useful to talk to servers
 .Dq by hand
 rather than through a user interface.
 It can aid in troubleshooting,
 when it might be necessary to verify what data a server is sending
 in response to commands issued by the client.
 For example, to retrieve the home page of a web site:
 .Bd -literal -offset indent
 $ printf "GET / HTTP/1.0\er\en\er\en" | nc host.example.com 80
 .Ed
 .Pp
 Note that this also displays the headers sent by the web server.
 They can be filtered, using a tool such as
 .Xr sed 1 ,
 if necessary.
 .Pp
 More complicated examples can be built up when the user knows the format
 of requests required by the server.
 As another example, an email may be submitted to an SMTP server using:
 .Bd -literal -offset indent
 $ nc [\-C] localhost 25 \*(Lt\*(Lt EOF
 HELO host.example.com
 MAIL FROM:\*(Ltuser@host.example.com\*(Gt
 RCPT TO:\*(Ltuser2@host.example.com\*(Gt
 DATA
 Body of email.
 \&.
 QUIT
 EOF
 .Ed
 .Sh PORT SCANNING
 It may be useful to know which ports are open and running services on
 a target machine.
 The
 .Fl z
 flag can be used to tell
 .Nm
 to report open ports,
 rather than initiate a connection. Usually it's useful to turn on verbose
 output to stderr by use this option in conjunction with
 .Fl v
 option.
 .Pp
 For example:
 .Bd -literal -offset indent
 $ nc \-zv host.example.com 20-30
 Connection to host.example.com 22 port [tcp/ssh] succeeded!
 Connection to host.example.com 25 port [tcp/smtp] succeeded!
 .Ed
 .Pp
 The port range was specified to limit the search to ports 20 \- 30, and is
 scanned by increasing order.
 .Pp
 You can also specify a list of ports to scan, for example:
 .Bd -literal -offset indent
 $ nc \-zv host.example.com 80 20 22
 nc: connect to host.example.com 80 (tcp) failed: Connection refused
 nc: connect to host.example.com 20 (tcp) failed: Connection refused
 Connection to host.example.com port [tcp/ssh] succeeded!
 .Ed
 .Pp
 The ports are scanned by the order you given.
 .Pp
 Alternatively, it might be useful to know which server software
 is running, and which versions.
 This information is often contained within the greeting banners.
 In order to retrieve these, it is necessary to first make a connection,
 and then break the connection when the banner has been retrieved.
 This can be accomplished by specifying a small timeout with the
 .Fl w
 flag, or perhaps by issuing a
 .Qq Dv QUIT
 command to the server:
 .Bd -literal -offset indent
 $ echo "QUIT" | nc host.example.com 20-30
 SSH-1.99-OpenSSH_3.6.1p2
 Protocol mismatch.
 220 host.example.com IMS SMTP Receiver Version 0.84 Ready
 .Ed
 .Sh EXAMPLES
 Open a TCP connection to port 42 of host.example.com, using port 31337 as
 the source port, with a timeout of 5 seconds:
 .Pp
 .Dl $ nc -p 31337 -w 5 host.example.com 42
 .Pp
 Open a UDP connection to port 53 of host.example.com:
 .Pp
 .Dl $ nc -u host.example.com 53
 .Pp
 Open a TCP connection to port 42 of host.example.com using 10.1.2.3 as the
 IP for the local end of the connection:
 .Pp
 .Dl $ nc -s 10.1.2.3 host.example.com 42
 .Pp
 Create and listen on a
 .Ux Ns -domain
 stream socket:
 .Pp
 .Dl $ nc -lU /var/tmp/dsocket
 .Pp
 Connect to port 42 of host.example.com via an HTTP proxy at 10.2.3.4,
 port 8080.
 This example could also be used by
 .Xr ssh 1 ;
 see the
 .Cm ProxyCommand
 directive in
 .Xr ssh_config 5
 for more information.
 .Pp
 .Dl $ nc -x10.2.3.4:8080 -Xconnect host.example.com 42
 .Pp
 The same example again, this time enabling proxy authentication with username
 .Dq ruser
 if the proxy requires it:
 .Pp
 .Dl $ nc -x10.2.3.4:8080 -Xconnect -Pruser host.example.com 42
 .Sh SEE ALSO
 .Xr cat 1 ,
 .Xr ssh 1
 .Sh AUTHORS
 Original implementation by *Hobbit*
 .Aq hobbit@avian.org .
 .br
 Rewritten with IPv6 support by
 .An Eric Jackson Aq ericj@monkey.org .
 .br
 Modified for Debian port by Aron Xu
 .Aq aron@debian.org .
 .Sh CAVEATS
 UDP port scans using the
 .Fl uz
 combination of flags will always report success irrespective of
 the target machine's state.
 However,
 in conjunction with a traffic sniffer either on the target machine
 or an intermediary device,
 the
 .Fl uz
 combination could be useful for communications diagnostics.
 Note that the amount of UDP traffic generated may be limited either
 due to hardware resources and/or configuration settings.