php: how to prevent SQL injection from $_POST

i have some php script and i think this have a lot of mistake. because of my limited knowledge in concatenation and SQL injection. At 1st time i'm not have any trouble because this script use PHP-Mysql.

But after i try to change into Interbase, i meet a lot of t开发者_如何学Pythonrouble. Please help to identify my fault.

this my following query:

$sLimit = "";
        if ( isset( $_POST['iDisplayStart'] ) )
        {
                $sLimit = " FIRST ".$_POST['iDisplayStart']." SKIP ".$_POST['iDisplayLength'];
        }
$sOrder ="";
        $sOrder = " ORDER BY LINE_NAME ";
$sWhere = "";
        if (postVar('sSearch') !="" )
        {
                 $sWhere = " WHERE (LINE_NAME LIKE '%".$_POST['sSearch']."%' OR
                                MODEL_ONLY LIKE '%".$_POST['sSearch']."%' OR ".
                               " VER_ONLY LIKE '%".$_POST['sSearch']."%' OR ".
                               " LOT_SIZE LIKE '%".$_POST['sSearch']."%' OR ".
                               " START_SERIAL LIKE '%".$_POST['sSearch']."%' OR ".
                               " SERIAL_NO_LOW LIKE '%".$_POST['sSearch']."%' OR ".
                               " SERIAL_NO_UP LIKE '%".$_POST['sSearch']."%' OR ".
                               " PROD_NO LIKE '%".$_POST['sSearch']."%' OR ".
                               " PROD_DATE LIKE '%".$_POST['sSearch']."%') ";
        }
 $sQuery = "SELECT LINE_NAME, MODEL_ONLY, VER_ONLY, PROD_NO, 
                   LOT_SIZE, START_SERIAL, SERIAL_NO_LOW, SERIAL_NO_UP, PROD_DATE 
            FROM DOC_TO".$sWhere.$sOrder.$sLimit.";";
 $rResult = ibase_query( $sQuery) or _doError(_ERROR30 . ' (<small>' . htmlspecialchars($sql) . '</small>): ' . ibase_errmsg() );  

 $sQuery = "SELECT COUNT(*) FROM (SELECT LINE_NAME, MODEL_ONLY, VER_ONLY, PROD_NO,
                                         LOT_SIZE, START_SERIAL, SERIAL_NO_LOW, SERIAL_NO_UP, PROD_DATE 
                                  FROM DOC_TO'.$sWhere.$sOrder.$sLimit.')";
 $rResultFilterTotal = ibase_query( $sQuery) or _doError(_ERROR30 . ' (<small>' . htmlspecialchars($sql) . '</small>): ' . ibase_errmsg() );
 $aResultFilterTotal = ibase_fetch_assoc($rResultFilterTotal);
 $iFilteredTotal = $aResultFilterTotal[0];

notes: i need learn more about concatenation.thanks for advance.

---

error:

Dynamic SQL Error SQL error code = -104 Token unknown - line 3, column 39 '.. ORDER BY LINE_NAME ..'

---

Looks as if it could run, so if it fails please describe how.

There is, however, one immediately visible mistake in it: In the lines

$sQuery = "SELECT COUNT(*) FROM (SELECT LINE_NAME, MODEL_ONLY, VER_ONLY, PROD_NO,
                                         LOT_SIZE, START_SERIAL, SERIAL_NO_LOW, SERIAL_NO_UP, PROD_DATE 
                                  FROM DOC_TO'.$sWhere.$sOrder.$sLimit.')";

you are starting a string with double quotes and you try to interrupt the string with single quotes, which will not work. So the code must be:

$sQuery = "SELECT COUNT(*) FROM (SELECT LINE_NAME, MODEL_ONLY, VER_ONLY, PROD_NO,
                                         LOT_SIZE, START_SERIAL, SERIAL_NO_LOW, SERIAL_NO_UP, PROD_DATE 
                                  FROM DOC_TO".$sWhere.$sOrder.$sLimit.")";

Depending on your environment in addition there is an important security flaw in your code: For example in the line

$sLimit = " FIRST ".$_POST['iDisplayStart']." SKIP ".$_POST['iDisplayLength'];

you are using $_POST to put it directly into an SQL query, which opens a so-called SQL injection security hole.

---

i have found the answer from AndreKR's guidance:

$sLimit = "";
        if ( isset( $_POST['iDisplayStart'] ) )
        {
                settype($iDisplayStart,'integer');
                $iDisplayStart = $_POST['iDisplayStart'];
                $iDisplayLength = $_POST['iDisplayLength'];
                $sLimit = sprintf(" FIRST ".$iDisplayStart." SKIP ".$iDisplayLength);
        }

and change all $_POST:

'%".$_POST['sSearch_0']."%'
into
''%".$_POST['sSearch_0']."%''   //this to prevent injection For databases Like Oracle, DB2, MS SQL, Firebird

and change :

$sQuery = "SELECT COUNT(*) FROM(......)
into
$sQuery = "SELECT COUNT(*) AS DCOUNT FROM DOC_TO".$sWhere.$sLimit.";"; //delete $sOrder

$aResultFilterTotal = ibase_fetch_assoc($rResultFilterTotal);
$iFilteredTotal = $aResultFilterTotal['DCOUNT'];  //change from ......[0]

and add at the last php page:

ibase_free_result($aResultTotal);
?>