这种使用单选按钮的表单对 SQL 注入安全吗？

Question

I'm trying to make a dynamic search feature on my website, where the user can choose to look up claim information based on ID, Make, Model, or Date. There is a search bar to type in the data and the radio buttons provide the search filter.

I'm wondering if my simple if-statement approach has vulnerabilities to SQL injection since I'm passing in the variable directly as the column name (PDO won't let you pass this value in as a parameter as I understand it)

HTML CODE:

    <form method="POST" action="find-claims.php">
        <label for="find-claim">Find Claim:</label>
        <input type="search" id="claim-search-bar" name="claim-search-bar"><br/>
        <input type="radio" value="by-id" class="radio-param" name="search-param" checked><label for="by-id">By Claim Id</label>
        <input type="radio" value="by-make" class="radio-param" name="search-param"><label for="by-make">By Vehicle Make</label>
        <input type="radio" value="by-model" class="radio-param" name="search-param"><label for="by-model">By Vehicle Model</label>
        <input type="radio" value="by-date" class="radio-param" name="search-param"><label for="by-date">By Claim Date</label>
        <input type="submit" class="radio-param" value="Submit">
    </form>

PHP CODE:

// Get search data
$searchVal = $_POST["claim-search-bar"];

// Get radio value
$searchType = $_POST["search-param"];

// Store search type into db-naming scheme
$radioVal = "";
if($searchType == "by-id"){
    $radioVal = "claim_id";
}
else if($searchType == "by-make"){
    $radioVal = "make";
}
else if($searchType == "by-model"){
    $radioVal = "model";
}
else if($searchType == "by-date"){
    $radioVal = "date_received";
}

// DB Interaction
try{
    // Connection to DB
    require "../db-info.php";
    $dbh = new PDO("mysql:host=$serverName; dbname=$dbName", $userName, $password);
    $dbh->setAttribute( PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION );

    // Get Claim based off dynamic input
    $getClaim = $dbh->prepare("SELECT * FROM claims WHERE $radioVal = ?");
    $getClaim->bindParam(1, $searchVal);
    $getClaim->execute();
    $claimInfo = $getClaim->fetchAll();

    // Checks if DB returned any data
    if($claimInfo){
        // Display corresponding info
    }
    else{
        echo "sorry no claim found";
    }

    $dbh = null;
    $stmt = null;

} catch(PDOException $e){
    throw new \PDOException($e->getMessage(), (int)$e->getCode());
}

Answer 1

You can store the search values in the array. Along with removing the useless try-catch it will make your code two times less bloated.

// Get search data
$searchVal = $_POST["claim-search-bar"];

// Get radio value
$searchType = $_POST["search-param"];

// Store search type into db-naming scheme
$searchValues = [
    "by-id" => "claim_id",
    "by-make" => "make",
    "by-model" => "model",
    "by-date") => "date_received",
];
$radioVal = $searchValues[$searchType] ?? "claim_id";
// Connection to DB
require "../db-info.php";
// the connection code should really go into include

// Get Claim based off dynamic input
$getClaim = $dbh->prepare("SELECT * FROM claims WHERE $radioVal = ?");
$getClaim->execute([$searchVal]);
$claimInfo = $getClaim->fetchAll();

// Checks if DB returned any data
if($claimInfo){
    // Display corresponding info
}
else{
    echo "sorry no claim found";
}

Answer 2

Because $radioVal is only assigned literal values you wrote in your code, and it is never assigned any untrusted content, it is safe with respect to SQL injection.

However, I recommend you give it a better default other than "" . Because if none of the known values for $searchType are matched, then $radioVal will remain "" and you'll get an SQL statement of:

SELECT * FROM claims WHERE  = ?

That'll be a syntax error. It won't be due to SQL injection, but it won't work.

And by the way, you do not need to sanitize $searchVal . That's the point of using a bound parameter, that it is bound after the query is prepared, so it cannot introduce SQL injection. It doesn't matter if it's sanitized or not.