CSRF

CSRF，全称Cross-site request forgery，翻译过来就是跨站请求伪造，是指利用受害者尚未失效的身份认证信息（cookie、会话等），诱骗其点击恶意链接或者访问包含攻击代码的页面，在受害人不知情的情况下以受害者的身份向（身份认证信息所对应的）服务器发送请求，从而完成非法操作（如转账、改密等）。CSRF与XSS最大的区别就在于，CSRF并没有盗取cookie而是直接利用。

low

<?phpif( isset( $_GET[ 'Change' ] ) ) {// Get input$pass_new  = $_GET[ 'password_new' ];$pass_conf = $_GET[ 'password_conf' ];// Do the passwords match?if( $pass_new == $pass_conf ) {// They do!$pass_new = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $pass_new ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));$pass_new = md5( $pass_new );// Update the database$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()) ? $___mysqli_res : false)) . '</pre>' );// Feedback for the userecho "<pre>Password Changed.</pre>";}else {// Issue with passwords matchingecho "<pre>Passwords did not match.</pre>";}((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}?> 

// Do the passwords match?if( $pass_new == $pass_conf ) {// They do!$pass_new = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $pass_new ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));$pass_new = md5( $pass_new );

服务器收到修改密码的请求后，会检查参数password_new与password_conf是否相同，如果相同，就会修改密码，并没有任何的防CSRF机制（当然服务器对请求的发送者是做了身份验证的，是检查的cookie，只是这里的代码没有体现）。

需要注意的是，CSRF最关键的是利用受害者的cookie向服务器发送伪造请求，所以如果受害者之前用Chrome浏览器登录的这个系统，而用搜狗浏览器点击这个链接，攻击是不会触发的，因为搜狗浏览器并不能利用Chrome浏览器的cookie，所以会自动跳转到登录界面。

构造链接http://127.0.0.1/dvwa/vulnerabilities/csrf/?password_new=admin&password_conf=admin&Change=Change#
就是访问这个链接密码就会改变

还可以利用短网址缩短网址进行伪装

medium

<?phpif( isset( $_GET[ 'Change' ] ) ) {// Checks to see where the request came fromif( stripos( $_SERVER[ 'HTTP_REFERER' ] ,$_SERVER[ 'SERVER_NAME' ]) !== false ) {// Get input$pass_new  = $_GET[ 'password_new' ];$pass_conf = $_GET[ 'password_conf' ];// Do the passwords match?if( $pass_new == $pass_conf ) {// They do!$pass_new = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $pass_new ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));$pass_new = md5( $pass_new );// Update the database$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()) ? $___mysqli_res : false)) . '</pre>' );// Feedback for the userecho "<pre>Password Changed.</pre>";}else {// Issue with passwords matchingecho "<pre>Passwords did not match.</pre>";}}else {// Didn't come from a trusted sourceecho "<pre>That request didn't look correct.</pre>";}((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}?> 

相关函数学习
stripos() 函数查找字符串在另一字符串中第一次出现的位置（不区分大小写）。

if( stripos( $_SERVER[ 'HTTP_REFERER' ] ,$_SERVER[ 'SERVER_NAME' ]) !== false )

这句代码就是利用stripos() 函数进行HTTP_REFERER（http数据包头的Referer参数的值，表示来源地址）和SERVER_NAME（http数据包头的Host参数，及要访问的主机名）的匹配检查

抓包查看

过滤规则是http包头的Referer参数的值中必须包含主机名（这里是127.0.0.1）

可以将攻击页面命名为127.0.0.1.html（页面被放置在攻击者的服务器里）就可以绕过

high

<?phpif( isset( $_GET[ 'Change' ] ) ) {// Check Anti-CSRF tokencheckToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );// Get input$pass_new  = $_GET[ 'password_new' ];$pass_conf = $_GET[ 'password_conf' ];// Do the passwords match?if( $pass_new == $pass_conf ) {// They do!$pass_new = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $pass_new ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));$pass_new = md5( $pass_new );// Update the database$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()) ? $___mysqli_res : false)) . '</pre>' );// Feedback for the userecho "<pre>Password Changed.</pre>";}else {// Issue with passwords matchingecho "<pre>Passwords did not match.</pre>";}((is_null($___mysqli_res = mysqli_close($GLOBALS["___mysqli_ston"]))) ? false : $___mysqli_res);
}// Generate Anti-CSRF token
generateSessionToken();?> 

// Check Anti-CSRF tokencheckToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );

可以发现加入了Anti-CSRF token机制，用户每次访问改密页面时，服务器会返回一个随机的token，向服务器发起请求时，需要提交token参数，而服务器在收到请求时，会优先检查token，只有token正确，才会处理客户端的请求。

要绕过High级别的反CSRF机制，关键是要获取token，要利用受害者的cookie去修改密码的页面获取关键的token。

可以尝试去构造一个攻击页面，将其放置在攻击者的服务器，引诱受害者访问，从而完成CSRF攻击

impossible

<?phpif( isset( $_GET[ 'Change' ] ) ) {// Check Anti-CSRF tokencheckToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );// Get input$pass_curr = $_GET[ 'password_current' ];$pass_new  = $_GET[ 'password_new' ];$pass_conf = $_GET[ 'password_conf' ];// Sanitise current password input$pass_curr = stripslashes( $pass_curr );$pass_curr = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $pass_curr ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));$pass_curr = md5( $pass_curr );// Check that the current password is correct$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();// Do both new passwords match and does the current password match the user?if( ( $pass_new == $pass_conf ) && ( $data->rowCount() == 1 ) ) {// It does!$pass_new = stripslashes( $pass_new );$pass_new = ((isset($GLOBALS["___mysqli_ston"]) && is_object($GLOBALS["___mysqli_ston"])) ? mysqli_real_escape_string($GLOBALS["___mysqli_ston"],  $pass_new ) : ((trigger_error("[MySQLConverterToo] Fix the mysql_escape_string() call! This code does not work.", E_USER_ERROR)) ? "" : ""));$pass_new = md5( $pass_new );// Update database with new password$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();// Feedback for the userecho "<pre>Password Changed.</pre>";}else {// Issue with passwords matchingecho "<pre>Passwords did not match or current password incorrect.</pre>";}
}// Generate Anti-CSRF token
generateSessionToken();?> 

Impossible级别的代码利用PDO技术防御SQL注入，至于防护CSRF，则要求用户输入原始密码（简单粗暴），攻击者在不知道原始密码的情况下，无论如何都无法进行CSRF攻击。

学习PDO技术防范SQL注入的方法

File Inclusion

File Inclusion，意思是文件包含（漏洞），是指当服务器开启allow_url_include选项时，就可以通过php的某些特性函数（include()，require()和include_once()，require_once()）利用url去动态包含文件，此时如果没有对文件来源进行严格审查，就会导致任意文件读取或者任意命令执行。文件包含漏洞分为本地文件包含漏洞与远程文件包含漏洞，远程文件包含漏洞是因为开启了php配置中的allow_url_fopen选项（选项开启之后，服务器允许包含一个远程的文件）。

low

<?php// The page we wish to display
$file = $_GET[ 'page' ];?> 

服务器端对page参数没有做任何的过滤跟检查。
服务器期望用户的操作是点击下面的三个链接，服务器会包含相应的文件，并将结果返回。需要特别说明的是，服务器包含文件时，不管文件后缀是否是php，都会尝试当做php文件执行，如果文件内容确为php，则会正常执行并返回结果，如果不是，则会原封不动地打印文件内容，所以文件包含漏洞常常会导致任意文件读取与任意命令执行。

漏洞利用

本地文件包含

http://127.0.0.1/dvwa/vulnerabilities/fi/?page=/etc/shadow

Warning: include(/etc/shadow): failed to open stream: No such file or directory in D:\phpstudy_pro\WWW\dvwa\vulnerabilities\fi\index.php on line 36Warning: include(): Failed opening '/etc/shadow' for inclusion (include_path='.;C:\php\pear;../../external/phpids/0.6/lib/') in D:\phpstudy_pro\WWW\dvwa\vulnerabilities\fi\index.php on line 36

报错显示没有这个文件，同时暴露了服务器文件的绝对路径D:\phpstudy_pro\WWW

构造绝对路径

http://127.0.0.1/dvwa/vulnerabilities/fi/?page=D:\phpstudy_pro\WWW\dvwa\php.ini

; This file attempts to overwrite the original php.ini file. Doesnt always work. magic_quotes_gpc = Off allow_url_fopen = On allow_url_include = On

配置文件中的magic_quote_gpc选项为off。在php版本小于5.3.4的服务器中，当magic_quote_gpc选项为off时，我们可以在文件名中使用%00进行截断，也就是说文件名中%00后的内容不会被识别

使用%00截断可以绕过某些过滤规则，例如要求page参数的后缀必须为php

medium

<?php// The page we wish to display
$file = $_GET[ 'page' ];// Input validation
$file = str_replace( array( "http://", "https://" ), "", $file );
$file = str_replace( array( "../", "..\"" ), "", $file );?> 

对比low的代码增加了str_replace函数，对page参数进行替换的处理，将http:// 、https://、 ../、..\替换为空字符

可以使用双写绕过替换规则
因为替换的只是../、..\，所以对采用绝对路径的方式包含文件是不会受到任何限制

high

<?php// The page we wish to display
$file = $_GET[ 'page' ];// Input validation
if( !fnmatch( "file*", $file ) && $file != "include.php" ) {// This isn't the page we want!echo "ERROR: File not found!";exit;
}?> 

对比low使用了fnmatch函数检查page参数，要求page参数的开头必须是file，服务器才会去包含相应的文件

可以用浏览器打开一个本地文件，利用了file协议

可以构造形如

http://127.0.0.1/dvwa/vulnerabilities/fi/?page= file:///xxx

Impossible

<?php// The page we wish to display
$file = $_GET[ 'page' ];// Only allow include.php or file{1..3}.php
if( $file != "include.php" && $file != "file1.php" && $file != "file2.php" && $file != "file3.php" ) {// This isn't the page we want!echo "ERROR: File not found!";exit;
}?> 

Impossible级别的代码使用了白名单机制进行防护，简单粗暴，page参数必须为“include.php”、“file1.php”、“file2.php”、“file3.php”之一，彻底杜绝了文件包含漏洞

File Upload

文件上传漏洞，由于对上传文件的类型、内容没有进行严格的过滤、检查，可以通过上传木马获取服务器的webshell权限

low
直接传马尝试
上传成功并返回路径
然后用蚁剑连即可

查看源码

<?phpif( isset( $_POST[ 'Upload' ] ) ) {// Where are we going to be writing to?$target_path  = DVWA_WEB_PAGE_TO_ROOT . "hackable/uploads/";$target_path .= basename( $_FILES[ 'uploaded' ][ 'name' ] );// Can we move the file to the upload folder?if( !move_uploaded_file( $_FILES[ 'uploaded' ][ 'tmp_name' ], $target_path ) ) {// Noecho '<pre>Your image was not uploaded.</pre>';}else {// Yes!echo "<pre>{$target_path} succesfully uploaded!</pre>";}
}?> 

medium

<?phpif( isset( $_POST[ 'Upload' ] ) ) {// Where are we going to be writing to?$target_path  = DVWA_WEB_PAGE_TO_ROOT . "hackable/uploads/";$target_path .= basename( $_FILES[ 'uploaded' ][ 'name' ] );// File information$uploaded_name = $_FILES[ 'uploaded' ][ 'name' ];$uploaded_type = $_FILES[ 'uploaded' ][ 'type' ];$uploaded_size = $_FILES[ 'uploaded' ][ 'size' ];// Is it an image?if( ( $uploaded_type == "image/jpeg" || $uploaded_type == "image/png" ) &&( $uploaded_size < 100000 ) ) {// Can we move the file to the upload folder?if( !move_uploaded_file( $_FILES[ 'uploaded' ][ 'tmp_name' ], $target_path ) ) {// Noecho '<pre>Your image was not uploaded.</pre>';}else {// Yes!echo "<pre>{$target_path} succesfully uploaded!</pre>";}}else {// Invalid fileecho '<pre>Your image was not uploaded. We can only accept JPEG or PNG images.</pre>';}
}?> 

    // Is it an image?if( ( $uploaded_type == "image/jpeg" || $uploaded_type == "image/png" ) &&( $uploaded_size < 100000 ) ) 

代码对上传文件的类型、大小做了限制，要求文件类型必须是jpeg或者image，大小不能超过100000B

既然让上传jpeg或者image，那么可以通过修改文件后缀来实现绕过

high

<?phpif( isset( $_POST[ 'Upload' ] ) ) {// Where are we going to be writing to?$target_path  = DVWA_WEB_PAGE_TO_ROOT . "hackable/uploads/";$target_path .= basename( $_FILES[ 'uploaded' ][ 'name' ] );// File information$uploaded_name = $_FILES[ 'uploaded' ][ 'name' ];$uploaded_ext  = substr( $uploaded_name, strrpos( $uploaded_name, '.' ) + 1);$uploaded_size = $_FILES[ 'uploaded' ][ 'size' ];$uploaded_tmp  = $_FILES[ 'uploaded' ][ 'tmp_name' ];// Is it an image?if( ( strtolower( $uploaded_ext ) == "jpg" || strtolower( $uploaded_ext ) == "jpeg" || strtolower( $uploaded_ext ) == "png" ) &&( $uploaded_size < 100000 ) &&getimagesize( $uploaded_tmp ) ) {// Can we move the file to the upload folder?if( !move_uploaded_file( $uploaded_tmp, $target_path ) ) {// Noecho '<pre>Your image was not uploaded.</pre>';}else {// Yes!echo "<pre>{$target_path} succesfully uploaded!</pre>";}}else {// Invalid fileecho '<pre>Your image was not uploaded. We can only accept JPEG or PNG images.</pre>';}
}?> 

相关函数学习

strrpos(string,find,start)

函数返回字符串find在另一字符串string中最后一次出现的位置，如果没有找到字符串则返回false，可选参数start规定在何处开始搜索。

getimagesize(string filename)

函数会通过读取文件头，返回图片的长、宽等信息，如果没有相关的图片文件头，函数会报错。

可以看到，High级别的代码读取文件名中最后一个”.”后的字符串，期望通过文件名来限制文件类型，因此要求上传文件名形式必须是”.jpg”、”.jpeg”、”*.png”之一。同时，getimagesize函数更是限制了上传文件的文件头必须为图像类型。

就是要检查文件头，直接添加一个即可

上传成功

impossible

<?phpif( isset( $_POST[ 'Upload' ] ) ) {// Check Anti-CSRF tokencheckToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );// File information$uploaded_name = $_FILES[ 'uploaded' ][ 'name' ];$uploaded_ext  = substr( $uploaded_name, strrpos( $uploaded_name, '.' ) + 1);$uploaded_size = $_FILES[ 'uploaded' ][ 'size' ];$uploaded_type = $_FILES[ 'uploaded' ][ 'type' ];$uploaded_tmp  = $_FILES[ 'uploaded' ][ 'tmp_name' ];// Where are we going to be writing to?$target_path   = DVWA_WEB_PAGE_TO_ROOT . 'hackable/uploads/';//$target_file   = basename( $uploaded_name, '.' . $uploaded_ext ) . '-';$target_file   =  md5( uniqid() . $uploaded_name ) . '.' . $uploaded_ext;$temp_file     = ( ( ini_get( 'upload_tmp_dir' ) == '' ) ? ( sys_get_temp_dir() ) : ( ini_get( 'upload_tmp_dir' ) ) );$temp_file    .= DIRECTORY_SEPARATOR . md5( uniqid() . $uploaded_name ) . '.' . $uploaded_ext;// Is it an image?if( ( strtolower( $uploaded_ext ) == 'jpg' || strtolower( $uploaded_ext ) == 'jpeg' || strtolower( $uploaded_ext ) == 'png' ) &&( $uploaded_size < 100000 ) &&( $uploaded_type == 'image/jpeg' || $uploaded_type == 'image/png' ) &&getimagesize( $uploaded_tmp ) ) {// Strip any metadata, by re-encoding image (Note, using php-Imagick is recommended over php-GD)if( $uploaded_type == 'image/jpeg' ) {$img = imagecreatefromjpeg( $uploaded_tmp );imagejpeg( $img, $temp_file, 100);}else {$img = imagecreatefrompng( $uploaded_tmp );imagepng( $img, $temp_file, 9);}imagedestroy( $img );// Can we move the file to the web root from the temp folder?if( rename( $temp_file, ( getcwd() . DIRECTORY_SEPARATOR . $target_path . $target_file ) ) ) {// Yes!echo "<pre><a href='${target_path}${target_file}'>${target_file}</a> succesfully uploaded!</pre>";}else {// Noecho '<pre>Your image was not uploaded.</pre>';}// Delete any temp filesif( file_exists( $temp_file ) )unlink( $temp_file );}else {// Invalid fileecho '<pre>Your image was not uploaded. We can only accept JPEG or PNG images.</pre>';}
}// Generate Anti-CSRF token
generateSessionToken();?> 

相关函数学习

in_get(varname)

函数返回相应选项的值

imagecreatefromjpeg ( filename )

函数返回图片文件的图像标识，失败返回false

imagejpeg ( image , filename , quality)

从image图像以filename为文件名创建一个JPEG图像，可选参数quality，范围从 0（最差质量，文件更小）到
100（最佳质量，文件最大）

imagedestroy( img )

函数销毁图像资源

Impossible级别的代码对上传文件进行了重命名（为md5值，导致%00截断无法绕过过滤规则），加入Anti-CSRF token防护CSRF攻击，同时对文件的内容作了严格的检查，导致攻击者无法上传含有恶意脚本的文件。

8.5