Question

我一直在阅读有关SQL注入的文章，并决定修改我的代码以防止SQL注入。

例如，我有一个输入，我将值插入我的数据库。最初，我对注射的警惕是这样的：

function test_input($data) {
    $data = trim($data);
    $data = stripslashes($data);
    $data = htmlspecialchars($data);
    // $data = addslashes($data);
    $data = mysql_real_escape_string($data);
    return $data;
}

$artist = $_POST["artist"];     // can be anything
$artist = test_input($artist);  // escaped chars are &, quotes, <, >, \n, \r, etc.

if ($mysqli->query("SELECT * FROM `my_table` WHERE `artist` = '$artist'")->num_rows == 0) {
    $mysqli->query("INSERT INTO my_table (artist) VALUES ('$artist')");
    echo "New artist is added.";
} else {
    echo "Artist already exists.";
}

在我读过的文章中，有人建议应该使用准备好的陈述。我已经改变了我的代码并使用了它：

$artist = $_POST["artist"]; // can be anything

$query = $mysqli->prepare("SELECT * FROM my_table WHERE artist = ?");
$query->bind_param("s", $artist);
$query->execute();
$result = $query->get_result();
$query->close();

if ($result->num_rows == 0) {
    echo "Artist doesn't exist in the DB." . PHP_EOL;
    $query = $mysqli->prepare("INSERT INTO my_table (artist) VALUES (?)");
    $query->bind_param("s", $artist);
    $query->execute();
    if ($query->affected_rows > 0) {
        echo "Artist is added to the DB." . PHP_EOL;
    }
    $query->close();
} else {
    echo "Artist already exists in the DB." . PHP_EOL;
}

虽然这会阻止SQL注入，但它对XSS没有任何作用。所以我决定修改test_input（已移除$data = mysql_real_escape_string($data);）并使用它来阻止脚本注入。

function test_input($data) {
    $data = trim($data);
    $data = stripslashes($data);
    $data = htmlspecialchars($data);
    return $data;
}

$artist = $_POST["artist"]; // can be anything
$artist = test_input($artist);

现在，我的问题是关于使用预准备语句。我将插入三件物品;艺术家，专辑和歌曲。一遍又一遍地重复相同的过程（准备，绑定，执行，关闭）似乎对我来说是不情愿的。我想创建一个函数并用它包装准备好的语句进程。像这样：

function p_statement($mysqli, $query_string = "", $type = "", $vars = []) {
    $query = $mysqli->prepare($query_string);
    $query->bind_param($type, $vars);
    $query->execute();
    $result = null;
    preg_match("/^[A-Z]+/", $query_string, $command);
    switch ($command[0]) {
        case "SELECT":
            $result = $query->get_result();
            break;
        case "INSERT":
            $result = $query->affected_rows;
            break;
    }
    $query->close();
    return $result;
}

但是，这会产生一个问题：$vars数组。由于传递给mysqli_stmt::bind_param()的变量数量是可变的/动态的，我在主函数p_statement中使用了一个数组。我不知道应该如何将数组中的项目传递给mysqli_stmt::bind_param()。 bind_param期待(type, var1, var2, varn,)，我有一个数组。

我该如何做到这一点？

Answer 1

~~您正在寻找implode()~~

查看联机帮助页，它显示了有关使用call_user_func_array的信息。我编辑了一些代码段。

function p_statement($mysqli, $query_string = "", $type = "", $vars = []) {

    $query = $mysqli->prepare($query_string);

    //assign $type to first index of $vars
    array_unshift($vars, $type);

    //Turn all values into reference since call_user_func_array
    //expects arguments of bind_param to be references
    //@see mysqli::bind_param() manpage
    foreach ($vars as $key => $value) {
        $vars[$key] =& $vars[$key];
    }

    call_user_func_array(array($query, 'bind_param'), $vars);
    $query->execute();

    //INSERT, SELECT, UPDATE and DELETE have each 6 chars, you can
    //validate it using substr() below for better and faster performance
    if (strtolower(substr($query_string, 0, 6)) == "select") {
        $result = $query->get_result();
    } else {
        $result = $query->affected_rows;
    }

    $query->close();
    return $result;
}

Answer 2

我找到了一种使用call_user_func_array解决问题的方法。

function p_statement($mysqli, $query_string = "", $type = "", $vars = []) {
    $query = $mysqli->prepare($query_string);
    // create an empty array
    $parameters = array();
    // push the type string into the array by reference
    $parameters[] = & $type;
    // push the items from $vars array into the array by reference
    for ($i = 0; $i < count($vars); $i++) {
        $parameters[] = & $vars[$i];
    }
    // call mysqli_stmt::bind_param with the $parameters array, which contains [type, var1, var2, ...]
    call_user_func_array(array($query, "bind_param"), $parameters);
    $query->execute();
    $result = null;
    preg_match("/^[A-Z]+/", $query_string, $command);
    switch ($command[0]) {
        case "SELECT":
            $result = $query->get_result();
            break;
        case "INSERT":
        case "UPDATE":
        case "DELETE":
            $result = $query->affected_rows;
            break;
    }
    $query->close();
    return $result;
}

$artist = "3 Doors Down";
$year   = 2000;

$artist_select = p_statement($mysqli, "SELECT * FROM albums WHERE artist = ? AND year = ?", "si", [$artist, $year]);

var_dump($artist_select->fetch_all(MYSQLI_ASSOC));

输出：

array(1) {
  [0]=>
  array(3) {
    ["album"]=>
    string(15) "The Better Life"
    ["year"]=>
    int(2000)
    ["artist"]=>
    string(12) "3 Doors Down"
  }
}

在函数中包装预准备语句

2 个答案: