Updates basics_of_linux.md

# There can't be any space between the variable name and the equal sign. It has to be varname=command

battery_time=$(cat /sys/class/power_supply/BAT0/capacity)

# The variables cna then be used like this

# The variables can then be used like this

echo "$battery_time"

```

## Iterate over a file

This script will iterate over a file and echo out every single line:

route add default gw 192.168.55.1

```

Remember that these routes will only be temporary.

#### Example - Man in the middle a host

It is often useful to man in the middle all traffic from a machine, to see what requests and stuff it does.

Let's say that the scenario is that the victim-machine is connected to the mitm-machine by ethernet cable. This can be either a physical cable or thought a virtual machine.

**Victim machine**

On the victim machine we don't have network-manager installed. And out `/etc/network/interfaces` has nothing in it except for:

```

auto lo

iface lo inet loopback

```

When we run `ip addr`we get the following result:

```

root@deb64:~# ip a

1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1

    link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00

    inet 127.0.0.1/8 scope host lo

       valid_lft forever preferred_lft forever

    inet6 ::1/128 scope host 

       valid_lft forever preferred_lft forever

2: ens3: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000

    link/ether 52:54:00:a9:fc:4a brd ff:ff:ff:ff:ff:ff

```

So our network interface ens3 does not have an ip-address and it is down. So let's first give it an ip-address, now remember that this ip-address will only be temporary, and will disappear on next reboot. If you want to make it permanent you need to define it in `/etc/network/interface`

**Give interface an ip-address**

```

ip addr add 192.168.150.2/24 dev ens3

# Here we give it the ip-address 192.168.150.2 with netmask 255.255.255.0 (/24), and we 

# give it to the device/interface ens3

```

**Now we can start the interface, or "bring it up" as it is called:**

```

ip link set ens3 up

```

When we bring up the interface the routing table will automatically get populated. 

```

root@deb64:~# ip r

192.168.150.0/24 dev ens3 proto kernel scope link src 192.168.150.2 

```

**Add default gateway**

But we are still not  able to reach the internet since we have not defined a default gateway yet. So let's do that.

```

ip route add default via 192.168.150.1 dev ens3

```

If we look at the routing table now we can see our new default gateway.

```

root@deb64:~# ip route

default via 192.168.150.1 dev ens3 

192.168.150.0/24 dev ens3 proto kernel scope link src 192.168.150.2 

```

Now we are done setting up the victim machine.

**Attacking machine**

First we need to give our machine the ip-address of the default gateway, so that the victim will connect to the attacking machine.

```

ip addr add 192.168.150.1/24 dev ens3

```

Now we just need to configure the NATing.

```

iptables -t nat -A POSTROUTING -j ACCEPT 

```

This is all we have to do. If we now do a `curl icanhazip.com` from our victim machine, we can see the traffic flying by with tcpdump in our attacker-machine.

However, we might want to inspect the traffic in burp-suite, or some other proxy tool. In ordet to do that we can redirect specific traffic into our proxy with the help of our friend iptables.

```

iptables -t nat -A PREROUTING -i ens3 -s 192.168.150.2 -p tcp -m tcp --dport 443 -j REDIRECT --to-ports 8080

iptables -t nat -A PREROUTING -i ens3 -s 192.168.150.2 -p tcp -m tcp --dport 80  -j REDIRECT --to-ports 8080

iptables -t nat -A PREROUTING -i ens3 -s 192.168.150.2 -p tcp -m tcp --dport 53  -j REDIRECT --to-ports 53

```

Now we just have to configure burp-suite a little bit.

Go to `Proxy > Options > Proxy Listeners > Edit > Binding > All interfaces`

Go to: `Proxy > Options > Proxy Listeners > Edit > Request handling > Support invisible proxy`

Now if you do the following from the victim machine:

```

curl icanhazip.com

```

You will see the request in burp suite.

Remember that these routes will only be temporary.

### Wireless - wpa\_supplicant