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Re: DBI and MySQL

by Trimbach (Curate)
on Jul 12, 2002 at 11:42 UTC ( #181247=note: print w/replies, xml ) Need Help??

in reply to DBI and MySQL

It's also worth noting that placeholders also let you avoid the nastiness from having someone send your program f*cked input in order to get at data they're not supposed to. I'm guessing by the name of %INPUT that that hash is populated from data from the outside world, so, what if instead of $INPUT{'attorney'} = "Tom" (a legitimate value), some Evil person makes $INPUT{'attorney'} = "Tom' AND supersecret='yes'"

Assuming you removed the extra WHERE, your SQL would evaluate to this in your original code:

SELECT * FROM dataflex where attorney = 'TOM' AND supersecret='yes' an +d issue = 'some issue'
Not exactly what you expected, yes? Using placeholders, on the other hand, ensures that this doesn't happen. Here's what it would (mostly) look like (note the escaping of the single quotes):
<code> SELECT * FROM dataflex where attorney = 'TOM\' AND supersecret=\'yes\' +' AND supersecret='yes' and issue = 'some issue'
The single quotes around the malicious extra arguments are escaped, which means the WHOLE value (TOM' AND supersecret='yes') is checked for in the attorney column (which, dollars to donuts, won't match anywhere.) This prevents EvilDoers from getting at data they ain't supposed to get.

Placeholders are a nearly unqualified good. Learn to love them.

Gary Blackburn
Trained Killer

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