I think someone can still access files outside your WWW directory by
requesting a file called .\./somefile. When your script first checks
for instances of ".." in the URL, it doesn't find any since the periods
are separated by a backslash. The script then removes all backslashes,
changing the URL to ../somefile.
Matt
On Sun, Feb 17, 2002 at 10:26:28PM -0800, Ryan wrote:
> -----BEGIN PGP SIGNED MESSAGE-----
> Hash: SHA1
>
> This is a perl cgi script I wrote to allow me to have large html files on my
> web host without exceeding my storage quota.
>
> I'd like it looked at, _I_ can no longer abuse it to run random commands or
> go where I shouldn't, but that doesn't mean others can'.
>
> Any other feedback would also be great.
>
> #!/usr/bin/perl
> #Let users transparently access files that are gzipped server-side
> #Useful only to keep under my storage quota ;-)
>
> my $in = $ENV{'QUERY_STRING'}; # Handle CGI calls
> $in =~ s/\+/ /g; # Replace '+' with ' '
> $in =~ s/%(..)/pack("c",hex($1))/ge; # Undo URL quoting
>
> $in =~ s/\.\.//g; # Foil Nasty h4x0rz trying to desend
> # directories
> $in =~ s/\\//g; # There is no need for backslashes!
> $in =~ s/\'//g; # prevent h4x0rz from
> # running commands like
> # zcat.cgi?file=foo.html.gz';rm -rf *'
>
> my %data = split (/=/, $in); # Make an array
>
> my $file = $data{'file'}; # get the name of the requested file
>
> print "Content-Type: text/html\n\n";
> # print `echo '$file'`; # debugging
> print `zcat ~/WWW/'$file'`; # quotes prevent nastys.
>
> - --
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* Matt Roper <[EMAIL PROTECTED]> *
* http://www.mattrope.com *
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