DVWA靶场Insecure CAPTCHA(不安全验证)漏洞所有级别通关教程及源码审计

Insecure CAPTCHA(不安全验证)

Insecure CAPTCHA（不安全验证）漏洞指的是在实现 CAPTCHA（完全自动化公共图灵测试区分计算机和人类）机制时，未能有效保护用户输入的验证信息，从而使得攻击者能够绕过或破解该验证机制。这类漏洞通常出现在网络应用程序中，目的是防止自动化脚本（如机器人）对网站进行滥用，CAPTCHA全称为Completely Automated Public Turing Test to Tell Computers and Humans Apart，中文名字是全自动区分计算机和人类的图灵测试

low

正常修改会报错

重新修改密码并抓包发送到重放器

将step=1修改为step=2，发包

修改成功

源码审计

并没有什么过滤，设置了step=2才能修改，使用**mysqli_real_escape_string**可能SQL注入；使用了不安全的md5加密算法

<?phpif (isset($_POST['Change']) && ($_POST['step'] == '1')) { // Step 1: 用户提交了第一个表单，并且是第一步$hide_form = true; // 标识隐藏CAPTCHA表单// 获取用户输入的新密码和确认密码$pass_new  = $_POST['password_new'];$pass_conf = $_POST['password_conf'];// 通过第三方服务检查CAPTCHA$resp = recaptcha_check_answer($_DVWA['recaptcha_private_key'],$_POST['g-recaptcha-response']);// CAPTCHA验证未通过if (!$resp) {$html     .= "<pre><br />The CAPTCHA was incorrect. Please try again.</pre>";$hide_form = false; // 如果错误，不隐藏表单return;} else {// CAPTCHA验证通过，检查两次输入的密码是否匹配if ($pass_new == $pass_conf) {// 如果匹配，让用户确认更改$html .= "<pre><br />You passed the CAPTCHA! Click the button to confirm your changes.<br /></pre><form action=\"#\" method=\"POST\"><input type=\"hidden\" name=\"step\" value=\"2\" /><input type=\"hidden\" name=\"password_new\" value=\"{$pass_new}\" /><input type=\"hidden\" name=\"password_conf\" value=\"{$pass_conf}\" /><input type=\"submit\" name=\"Change\" value=\"Change\" /></form>";} else {// 两次输入的密码不匹配$html     .= "<pre>Both passwords must match.</pre>";$hide_form = false; // 不隐藏表单，提示用户重新输入}}
}
if (isset($_POST['Change']) && ($_POST['step'] == '2')) { // Step 2: 用户提交确认后的表单，进行更改操作$hide_form = true; // 隐藏CAPTCHA表单// 获取用户输入的新密码和确认密码$pass_new  = $_POST['password_new'];$pass_conf = $_POST['password_conf'];// 确认两个密码匹配if ($pass_new == $pass_conf) {// 对特殊字符进行转义，防止SQL注入$pass_new = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"], $pass_new) : "");// 将密码进行md5加密（注：md5已不再安全，实际应用中应使用更安全的加密方式）$pass_new = md5($pass_new);// 更新数据库中当前用户的密码$insert = "UPDATE `users` SET password = '$pass_new' WHERE user = '" . dvwaCurrentUser() . "';";$result = mysqli_query($GLOBALS["___mysqli_ston"], $insert) or die('<pre>' . ((is_object($GLOBALS["___mysqli_ston"])) ? mysqli_error($GLOBALS["___mysqli_ston"]) : (($___mysqli_res = mysqli_connect_error()) ? $___mysqli_res : false)) . '</pre>');// 给用户反馈密码已更改$html .= "<pre>Password Changed.</pre>";} else {// 两次输入的密码不匹配$html .= "<pre>Passwords did not match.</pre>";$hide_form = false; // 提示错误，不隐藏表单}// 关闭数据库连接((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}
?>

medium

同样修改后抓包

这里查看源码可以发现设置了passed_captcha验证

将step=1修改为step=2，并且添加passed_captcha=true

修改成功

源码审计

与low级别差不多，多了一个设置passed_captcha=true才能正常修改

?phpif (isset($_POST['Change']) && ($_POST['step'] == '1')) {// 第一步：用户提交了表单且处于步骤1$hide_form = true; // 标识隐藏CAPTCHA表单// 获取用户输入的新密码和确认密码$pass_new = $_POST['password_new'];$pass_conf = $_POST['password_conf'];// 从第三方验证CAPTCHA$resp = recaptcha_check_answer($_DVWA['recaptcha_private_key'],$_POST['g-recaptcha-response']);// CAPTCHA验证未通过if (!$resp) {$html .= "<pre><br />The CAPTCHA was incorrect. Please try again.</pre>";$hide_form = false; // 如果错误，不隐藏表单return;} else {// CAPTCHA验证通过，检查两次输入的密码是否匹配if ($pass_new == $pass_conf) {// 密码匹配，显示下一步$html .= "<pre><br />You passed the CAPTCHA! Click the button to confirm your changes.<br /></pre><form action=\"#\" method=\"POST\"><input type=\"hidden\" name=\"step\" value=\"2\" /><input type=\"hidden\" name=\"password_new\" value=\"{$pass_new}\" /><input type=\"hidden\" name=\"password_conf\" value=\"{$pass_conf}\" /><input type=\"hidden\" name=\"passed_captcha\" value=\"true\" /><input type=\"submit\" name=\"Change\" value=\"Change\" /></form>";} else {// 两次输入的密码不匹配$html .= "<pre>Both passwords must match.</pre>";$hide_form = false; // 不隐藏表单，提示用户重新输入}}
}
if (isset($_POST['Change']) && ($_POST['step'] == '2')) {// 第二步：用户提交确认后的表单$hide_form = true; // 隐藏CAPTCHA表单// 获取用户输入的新密码和确认密码$pass_new = $_POST['password_new'];$pass_conf = $_POST['password_conf'];// 确保用户完成了第一步if (!$_POST['passed_captcha']) {$html .= "<pre><br />You have not passed the CAPTCHA.</pre>";$hide_form = false;return;}// 检查两次输入的密码是否匹配if ($pass_new == $pass_conf) {// 匹配进行密码更新// 转义特殊字符，防止SQL注入$pass_new = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"], $pass_new) : "");// 使用md5加密密码（注意：md5不够安全，实际应用中应使用更好的加密方法）$pass_new = md5($pass_new);// 更新数据库中的用户密码$insert = "UPDATE `users` SET password = '$pass_new' WHERE user = '" . dvwaCurrentUser() . "';";$result = mysqli_query($GLOBALS["___mysqli_ston"], $insert) or die('<pre>' . ((is_object($GLOBALS["___mysqli_ston"])) ? mysqli_error($GLOBALS["___mysqli_ston"]) : (($___mysqli_res = mysqli_connect_error()) ? $___mysqli_res : false)) . '</pre>');// 反馈用户密码已更改$html .= "<pre>Password Changed.</pre>";} else {// 两次输入的密码不匹配$html .= "<pre>Passwords did not match.</pre>";$hide_form = false;}// 关闭数据库连接((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}
?>

high

定位登录框，发现这么一处注释

 **DEV NOTE**   Response: 'hidd3n_valu3'   &&   User-Agent: 'reCAPTCHA'   **/DEV NOTE** 

结合源码得知需要g-recaptcha-response=hidd3n_valu3 并且 User-Agent: 'reCAPTCHA'

同样修改后抓包

发送包并修改参数

修改成功

源码审计

设置了请求头：reCAPTCHA ； g-recaptcha-response = hidd3n_valu3，以及token使会话更有安全性，还利用CSRF令牌使的更安全

<?phpif (isset($_POST['Change'])) {// 用户提交了表单，隐藏CAPTCHA表单$hide_form = true;// 获取用户输入的新密码和确认密码$pass_new = $_POST['password_new'];$pass_conf = $_POST['password_conf'];// 验证CAPTCHA$resp = recaptcha_check_answer($_DVWA['recaptcha_private_key'],$_POST['g-recaptcha-response']);// 检查CAPTCHA验证是否通过或符合内置绕过条件if ($resp || ($_POST['g-recaptcha-response'] == 'hidd3n_valu3'&& $_SERVER['HTTP_USER_AGENT'] == 'reCAPTCHA')) {// CAPTCHA验证通过，检查两次输入的密码是否匹配if ($pass_new == $pass_conf) {// 转义输入以防止SQL注入攻击$pass_new = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"], $pass_new) : "");// 使用md5加密密码（注意：不推荐在生产环境中使用）$pass_new = md5($pass_new);// 更新数据库用户密码$insert = "UPDATE `users` SET password = '$pass_new' WHERE user = '" . dvwaCurrentUser() . "' LIMIT 1;";$result = mysqli_query($GLOBALS["___mysqli_ston"], $insert) or die('<pre>' . ((is_object($GLOBALS["___mysqli_ston"])) ? mysqli_error($GLOBALS["___mysqli_ston"]) : (($___mysqli_res = mysqli_connect_error()) ? $___mysqli_res : false)) . '</pre>');// 返回用户的反馈信息$html .= "<pre>Password Changed.</pre>";} else {// 如果密码不匹配$html .= "<pre>Both passwords must match.</pre>";$hide_form = false;}} else {// CAPTCHA输入错误时的响应$html .= "<pre><br />The CAPTCHA was incorrect. Please try again.</pre>";$hide_form = false;return;}// 关闭数据库连接((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}// 生成反CSRF攻击的令牌
generateSessionToken();
?>

impossible

源码审计

结合反CSRF令牌和CAPTCHA，提高安全性；并且使用PDO和参数绑定防止SQL注入。

<?php
if (isset($_POST['Change'])) {// 检查反CSRF令牌，确保请求的合法性checkToken($_REQUEST['user_token'], $_SESSION['session_token'], 'index.php');// 隐藏CAPTCHA表单$hide_form = true;// 获取用户输入的新密码，并移除转义字符$pass_new = $_POST['password_new'];$pass_new = stripslashes($pass_new);$pass_new = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"], $pass_new) : "");$pass_new = md5($pass_new); // 对新密码进行MD5加密// 获取用户输入的确认密码，并移除转义字符$pass_conf = $_POST['password_conf'];$pass_conf = stripslashes($pass_conf);$pass_conf = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"], $pass_conf) : "");$pass_conf = md5($pass_conf); // 对确认密码进行MD5加密// 获取用户输入的当前密码，并移除转义字符$pass_curr = $_POST['password_current'];$pass_curr = stripslashes($pass_curr);$pass_curr = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"], $pass_curr) : "");$pass_curr = md5($pass_curr); // 对当前密码进行MD5加密// 使用第三方功能验证CAPTCHA$resp = recaptcha_check_answer($_DVWA['recaptcha_private_key'],$_POST['g-recaptcha-response']);// 如果CAPTCHA验证失败if (!$resp) {// 反馈信息：CAPTCHA错误$html .= "<pre><br />The CAPTCHA was incorrect. Please try again.</pre>";$hide_form = false;} else {// 检查当前密码是否正确$data = $db->prepare('SELECT password FROM users WHERE user = (:user) AND password = (:password) LIMIT 1;');$data->bindParam(':user', dvwaCurrentUser(), PDO::PARAM_STR);$data->bindParam(':password', $pass_curr, PDO::PARAM_STR);$data->execute();// 检查新密码是否匹配，且当前密码是否正确if (($pass_new == $pass_conf) && ($data->rowCount() == 1)) {// 更新数据库中的用户密码$data = $db->prepare('UPDATE users SET password = (:password) WHERE user = (:user);');$data->bindParam(':password', $pass_new, PDO::PARAM_STR);$data->bindParam(':user', dvwaCurrentUser(), PDO::PARAM_STR);$data->execute();// 用户反馈：成功$html .= "<pre>Password Changed.</pre>";} else {// 用户反馈：失败$html .= "<pre>Either your current password is incorrect or the new passwords did not match.<br />Please try again.</pre>";$hide_form = false;}}
}// 生成反CSRF攻击的令牌
generateSessionToken();
?>