Re: shell script cgi

From: c jones (ojnes33at_private)
Date: Fri Nov 15 2002 - 08:26:44 PST

  • Next message: Philip Rowlands: "Re: shell script cgi"

    Answering two messages in one...
    
    --- Ian Stoba <ianat_private> wrote:
    > Sorry to state the obvious, but you know that the
    > HTTP_USER_AGENT is 
    > set in the headers and not in the request, right?
    
    Correct. I am explicitly setting the value (although I
    did try to use arguments to the CGI so I could
    reference $*, but that didn't get me anywhere).
    
    
    --- Brian Hatch <vuln-devat_private> wrote:
    > Anyone else remembering the 'nph-finger' days of
    > yore?
    > It had
    > 	echo QUERY_STRING = $QUERY_STRING
    > 
    > you could pass things like '*' to abuse shell
    > filename
    > expansion, and that'd be the best you're going to
    > get
    > out of that code.  I don't think you can get it to
    > execute arbitrary commands, no matter what you try.
    
    Okay... my testing with this is telling that this is
    true, but... why? Where is the protection coming
    from--the fact that HTTP_USER_AGENT is an environment
    variable?  It seems that if I set the value *in* the
    script it terminates the echo command & executes what
    I want it to, but if it comes from the environment it
    interprets it as a string and that's it.
    
    I searhed the Neohapsis/SF archives for nph-finger but
    couldn't find any history there... 
    
    I suppose I should have put this in my first message,
    but here's a general sample of what I'm trying to put
    into the HTTP_USER_AGENT field (for testing trying to
    cat the passwd file to /tmp)(I've tried a million
    variations trying to terminate that first echo):
    "|cat /etc/passwd>/tmp/passwd|echo "
    
    Thanks for you help
    
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