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Re: Need help with syntax error in CGI script (security hole)

by Ovid (Cardinal)
on Aug 02, 2004 at 01:47 UTC ( #379169=note: print w/replies, xml ) Need Help??

in reply to Need help with syntax error in CGI script

In addition to what the others have said, I'd like to point out a huge security hole. I've reformatted the code for clarity, but the following is logically equivalent to what you have:

my $dbh = DBI->connect( 'DBI:mysql:*********', '*****', '*****', {RaiseError => 1 , AutoCommit => 1} ) || die "Can't Connect: $!"; my $sth = $dbh->prepare(<<END_SQL); UPDATE inventory SET img="$short_name", thumb="$short_tname" WHERE partno="$img_name"; ENDSQL $sth->execute;

Never allow user to be able to send data directly to the database like this. If you do, you open yourself up to SQL injection attacks where the attacker can insert their own SQL and run it arbitrarily against the server. You can protect against this by using the $dbh->quote method on the variables before you insert them. However, a cleaner strategy is to always use placeholders:

my $sth = $dbh->prepare(<<END_SQL); UPDATE inventory SET img = ?, thumb = ? WHERE partno = ?; ENDSQL $sth->execute($short_name, $short_tname, $img_name);

Read "Placeholders and Bind Values" in the DBI documentation for more information.


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