You left out a simple example or two on how to specify what you will allow. So, Allow me =) 
my $file = $cgi->param( 'file' );
my $data;
#
# One way
#
$file =~ s#[^A-Z0-9a-z.]+##g;  #strip down to alphanum and period
  # can change the meaning of what people post.
$file =~ m#(.*)#; #evil evil evil if you haven't striped.
$data = $1 || ""; #not really necessary to have alternate, nice tho.
#
# Alternate way
#
$file =~ m#([A-Z0-9a-z.]+)#; #grab first good chunk. 
  # can potentially ignore a lot of data and boggle the user
$data = $1 | ""; #you really want this now, match can fail.
#
# My "best" way
#
die "Eeeek! Evil data sent to the 'file' parameter!\n"
  if ($file =~ m#[^A-Z0-9a-z.]#);
  #now use the first method above to detaint anyway...

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$you = new YOU;
honk() if $you->love(perl)

In reply to RE: CGI Security and the null byte problem by extremely
in thread CGI Security and the null byte problem by Ovid

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