Help with man in the middle setup using netcat on the tivo to redirect ports

Discussion in 'TiVo Help Center' started by ciper, Aug 15, 2007.

  1. ciper

    ciper Active Member

    Nov 4, 2004


    I need the advice of a unix guru. I've been trying to create a man in the middle situation using NC and piped output. I tried
    nc -l -p 81 | nc x.x.x.1 80 | nc -l -p 81
    but that isnt able to bind to the same port as the first one. I can't seem to get the connection to go both ways. Here is an example of what I have tried against my routers administration page to test

    bash-2.02# tail -f /var/hack/io | nc -l -p 82 &
    [11] 574
    bash-2.02# nc x.x.x.1 80 > /var/hack/io

    GET / HTTP/1.1
    User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.
    070725 Firefox/
    Accept: text/xml,application/xml,application/xhtml+xml,text/html;
    Accept-Language: en-us,en;q=0.5
    Accept-Encoding: gzip,deflate
    Accept-Charset: ISO-8859-1,utf-8;q=0.7,*;q=0.7
    Keep-Alive: 300
    Connection: keep-alive
    [b]At which point I get an error page in the browser
    I break out of the command and the error page is exactly what is in my IO file[/b]
    bash-2.02# cat /var/hack/io
    HTTP/1.0 400 Bad Request
    Server: httpd
    Date: Tue, 14 Aug 2007 23:42:22 GMT
    Content-Type: text/html
    Connection: close
    <HTML><HEAD><TITLE>400 Bad Request</TITLE></HEAD>
    <BODY BGCOLOR="#cc9999"><H4>400 Bad Request</H4>
    No request found.
    Does this mean my "tunnel" is working but tail is saying "file truncated" when the connection is established which is confusing everything?
  2. ormium

    ormium New Member

    Nov 27, 2012

    you have to use a pipe:

    mknod tmp_pipe p
    nc -l 1231 < tmp_pipe |nc hostname 80 > tmp_pipe

    you can also search and replace for strings and copy the intermediate traffic to your file system:

    nc -l 9080 < tmp_pipe |nc 9080 |tee original.txt |sed 's/HTTP\/1.1 771 Undefined/HTTP\/1.1 200 OK/' |tee modified.txt > tmp_pipe

    best Regards,


    Romeo Kienzler
    r o m e o . k i e n z l e r ( a - t ) g m a i l . c o m
  3. lrhorer

    lrhorer Active Member

    Aug 31, 2003
    After more than 5 years, I seriously doubt the OP is still seeking a solution.
  4. wintifrosch

    wintifrosch New Member

    Feb 28, 2014
    @lrhorer: I was VERY HAPPY about the reply of ormium. More than a year ago, he wrote exactly what I was looking for!

    A question is a question. We google them.
    A solution is a solution. We find them.

    I thank cypher for asking my question years ago.
    And i thank ormium for serving the answer long time before I was asking!

    That's why we love forums :up:
    What is your contribute?

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