Dear Monks

I have this situation in which I have to create a table, but the user defines the column names and column definitions.
Anyway, I know now that the column name is handled by quote_identifier(..), but the definition, for example, a user might give me: 
VARCHAR(100) ); DROP DATABASE mysql; --'

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is a lot harder to validate. I couldn't find a function that does this.
So I wrote the following test script to detect this kind of SQL injection: 
#! /usr/bin/perl -l

use strict ;
use warnings ;

# USER INPUT
my $SQL = 'VARCHAR(100) ); DROP DATABASE mysql; --';

validate_column_definition( $SQL ) ;

my $query = sprintf( 'CREATE TABLE test ( a %s, b INT )', $SQL ) ;
print $query ;

sub validate_column_definition {
        my $SQL = shift ;

        # remove all strings (DEFAULT 'str' OR COMMENT 'str')
        $SQL =~ s/(['][^']+['])//g ;   # remove quoted strings
        $SQL =~ s/(["][^"]+["])//g ; # remove quoted strings

        if ( $SQL =~ /#|--|\/\*|;|'|`|"/ ) {  # detect invalid charact
+ers
                print "SQL INJECTION: $SQL\n" ;
        }
}

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I think this could work, but I'm not sure; does it detect all possible attacks and doesn't it break legal SQL?
Any help would really be appreciated

cheers
LuCa

In reply to Detect SQL injection by jeanluca

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