DVWA中命令执行漏洞
low
<?php
if( isset( $_POST[ 'Submit' ] ) ) {
// Get input
$target = $_REQUEST[ 'ip' ];
// Determine OS and execute the ping command.
if( stristr( php_uname( 's' ), 'Windows NT' ) ) {
// Windows
$cmd = shell_exec( 'ping ' . $target );
}
else {
// *nix
$cmd = shell_exec( 'ping -c 4 ' . $target );
}
// Feedback for the end user
$html .= "<pre>{$cmd}</pre>";
}
?>
可以看到并没有对客户传入的参数进行任何过滤，这时候构造
127.0.0.1 & ls
127.0.0.1 && ls
1 || ls
1 | ls
1;ls
可以来获取当前目录下文件名。并且能通过cat进行任意文件读取
medium
<?php
if( isset( $_POST[ 'Submit' ] ) ) {
// Get input
$target = $_REQUEST[ 'ip' ];
// Set blacklist
$substitutions = array(
'&&' => '',
';' => '',
);
// Remove any of the charactars in the array (blacklist).
$target = str_replace( array_keys( $substitutions ), $substitutions, $target );
// Determine OS and execute the ping command.
if( stristr( php_uname( 's' ), 'Windows NT' ) ) {
// Windows
$cmd = shell_exec( 'ping ' . $target );
}
else {
// *nix
$cmd = shell_exec( 'ping -c 4 ' . $target );
}
// Feedback for the end user
$html .= "<pre>{$cmd}</pre>";
}
?>
medium相对于low，设置了黑名单，但是也就只过滤了;和&&,并没有什么暖用
str_replace( array_keys( $substitutions ), $substitutions, $target ) ，如果在$target匹配到substitutions中的键值，那么就将其替换成substitutions中的值，即''
high
<?php
if( isset( $_POST[ 'Submit' ] ) ) {
// Get input
$target = trim($_REQUEST[ 'ip' ]);
// Set blacklist
$substitutions = array(
'&' => '',
';' => '',
'| ' => '',
'-' => '',
'$' => '',
'(' => '',
')' => '',
'`' => '',
'||' => '',
);
// Remove any of the charactars in the array (blacklist).
$target = str_replace( array_keys( $substitutions ), $substitutions, $target );
// Determine OS and execute the ping command.
if( stristr( php_uname( 's' ), 'Windows NT' ) ) {
// Windows
$cmd = shell_exec( 'ping ' . $target );
}
else {
// *nix
$cmd = shell_exec( 'ping -c 4 ' . $target );
}
// Feedback for the end user
$html .= "<pre>{$cmd}</pre>";
}
?>
相比于medium，过滤了更多的管道符，但我们发现过滤'| '时，跟了个空格，所以构造
127.0.0.1 |ls一样可以执行任意命令
impossible
<?php
if( isset( $_POST[ 'Submit' ] ) ) {
// Check Anti-CSRF token
checkToken( $_REQUEST[ 'user_token' ], $_SESSION[ 'session_token' ], 'index.php' );
// Get input
$target = $_REQUEST[ 'ip' ];
$target = stripslashes( $target );
// Split the IP into 4 octects
$octet = explode( ".", $target );
// Check IF each octet is an integer
if( ( is_numeric( $octet[0] ) ) && ( is_numeric( $octet[1] ) ) && ( is_numeric( $octet[2] ) ) && ( is_numeric( $octet[3] ) ) && ( sizeof( $octet ) == 4 ) ) {
// If all 4 octets are int's put the IP back together.
$target = $octet[0] . '.' . $octet[1] . '.' . $octet[2] . '.' . $octet[3];
// Determine OS and execute the ping command.
if( stristr( php_uname( 's' ), 'Windows NT' ) ) {
// Windows
$cmd = shell_exec( 'ping ' . $target );
}
else {
// *nix
$cmd = shell_exec( 'ping -c 4 ' . $target );
}
// Feedback for the end user
$html .= "<pre>{$cmd}</pre>";
}
else {
// Ops. Let the user name theres a mistake
$html .= '<pre>ERROR: You have entered an invalid IP.</pre>';
}
}
// Generate Anti-CSRF token
generateSessionToken();
?>
相比于high级别，加了随机token，防止csrf,用了explode()函数，以.为分割符，将$target字符串分割成了数组的形式，并且对各个部分进行了判定，因为正常的ip地址127.0.0.1，所以分割出来长度是4，并且全部是数字，利用这个特点，进行是否是数字判断，导致我们无法在地址后面动些手脚