5. Accessing Networks¶

5.1. WiFi via GUI¶

When running the Pi in desktop mode, you can join new Wifi Networks in a similar way to how you would do it on a Macintosh. In the menu bar at the top, on the right-hand side click on the wireless icon. Then from their you can select from the list of discovered networks to join them.

Note

If they have a padlock next to them then they require a password to join.

Since the College has a more complex form of authentication (username and password required). We will setup the Pi to connect to the IC network a slightly different way. We are going to modify a modify a configuration file called wpa_supplicant.conf.

5.2.1. Backup ¶

First we back up the configuration file wpa_supplicant.conf. We create the backup file wpa_supplicant.conf_backup in case we need to restore it later. It’s important that you don’t edit this backup after creating it. To do so we enter the command:

$ sudo cp /etc/wpa_supplicant/wpa_supplicant.conf /etc/wpa_supplicant/wpa_supplicant.conf_backup

5.2.2. Edit ¶

Then we edit the wpa_supplicant.conf. The default text editor installed in the Pi is nano. To edit a file with the nano editor is sufficient to enter the command nano /path/to/file. Therefore to edit wpa_supplicant.conf we enter the following command with admin user permission:

$ sudo nano /etc/wpa_supplicant/wpa_supplicant.conf

We edit the file so that the all the content appears like this:

ctrl_interface=DIR=/var/run/wpa_supplicant GROUP=netdev
update_config=1

network={
       ssid="Imperial-WPA"
       proto=RSN
       key_mgmt=WPA-EAP
       pairwise=CCMP
       auth_alg=OPEN
       eap=PEAP
       identity="ic\COLLEGE_USERNAME"
       password="YOUR_PASSWORD"
       priority=7
}

Where COLLEGE_USERNAME has to be replaced with your college username and YOUR_PASSWORD with the password associated to it.

Important

The configuration is case sensitive, so make sure you do not have typos. Even the slightest error in this file can cause the networking to fail so make sure it exactly like this.

Note

If you want to connect your Pi to the eduroam network, then set identity="COLLEGE_USERNAME@ic.ac.uk". Apply the same procedure for setting the password as seen below.

In the nano editor, to exit, press Ctrl + x. The editor will then present you with different options such as save the file or exit without modifying the file: y/n. We press y and then press enter. The editor now asks us for the name of the file we are saving, but as it already fills out the previous name for us, we press enter again.

Now we can check if the connection works by rebooting your RPi. Reboot it by entering:

$ sudo reboot now

One the system starts again the Pi should connect automatically to the WiFi.

5.2.3. Encrypting Your Password ¶

In order not to store the password in a plain text we substitute our password with an encrypted one using a MD4 hash generator. You can generate the hash with the following Linux command:

$ echo -n 'YOUR_PASSWORD' | iconv -t utf16le | openssl md4
You will have to substitute YOUR_PASSWORD with the password related to the account in the wpa_supplicant.conf. This will be the only time you’ll have to type it in plain text. Ask your colleagues to look away from the screen if you are not comfortable in them seeing your password.

The previous command will display the encrypted password on your terminal like this:

$ (stdin)= a6c71eedc2eacbca84003336a4a62a1c
We copy the string that was generated in your terminal screen (i.e. 'a6c71eedc2eacbca84003336a4a62a1c').
Tip

You can save the hash from your password in a file and then read its content:
$ echo -n 'YOUR_PASSWORD' | iconv -t utf16le | openssl md4 > hash.txt
$ cat hash.txt
The first command creates the encrypted password and stores it in the __hash.txt__ file. The second command reads the content of the __hash.txt__ file. In general we use the cat command to read and concatenate files.

Then we open the wpa_supplicant.conf file again:

$ sudo nano /etc/wpa_supplicant/wpa_supplicant.conf

In the password field replace "YOUR_PASSWORD" with the string you generated as hexadecimal characters, adding the ‘hash:’ prefix as shown in the example bellow:

network={
  ssid="Imperial-WPA"
  proto=RSN
  key_mgmt=WPA-EAP
  pairwise=CCMP
  auth_alg=OPEN
  eap=PEAP
  identity="ic\COLLEGE_USERNAME"
  password=hash:a6c71eedc2eacbca84003336a4a62a1c
}

The last security step to perform is to remove the bash history (the one that stores all the commands we had typed on the terminal). Therefore, we enter the following commands:

$ history -w
$ history -c

Then we reboot the Pi to check that the password was properly set up:

$ sudo reboot now

And you are done!

5.3. Pi as a hotspot¶

The Raspberry Pi can act as a standalone network. This can be useful in some situations where you do not want to rely on a separate wireless network, or when you might be going to a new location that cannot provide you with a network to use. Remember though that a standalone network made by the Pi will not be connected to the internet. You can find the guide to set up a standalone network here.