Access to the Télécom ParisTech network.

Notations

I will use <username> to denote the LDAP username, and <password> the corresponding password.

In my case, then I have the following:

 username="cdurand"
 password="¿?¿?¿?¿?"

SSH Access

Out-of-the-box access

You can use this script to access shells from Télécom ParisTech machines.

The code is not perfect and could be improved, dont hesitate to write comments on the github page if you have suggestions.

Please note that basic help is available by executing ./ssh.sh -h.

Shell access

Simple shell access can be performed through ssh.enst.fr.

 neze@yoga ~ $ ssh <username>@ssh.enst.fr
 <username>@ssh.enst.fr's password:
 ssh1%

You will end up randomly on ssh1 or ssh2 (with your same old home folder whatever the machine).

Access to a computer

You can access any computer in a lab, provided it is switched on. The examples will be made with c129-21, i.e., computer 21 from room 129 in the C building.

 neze@yoga ~ $ ssh <username>@ssh.enst.fr
 <username>@ssh.enst.fr's password:
 ssh1% ssh c129-21
 <username>@c129-21's password:
 c129-21%

Direct access

To avoid having to call every ssh command, and easily add new rooms to your configuration, you can edit your ssh config file (generally found in ~/.ssh/config).

 neze@yoga ~ $ mkdir -p ~/.ssh
 neze@yoga ~ $ $EDITOR ~/.ssh/config

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+Host enst room
+  User <username>
+
+Host enst
+  HostName ssh.enst.fr
+
+Host room
+  HostName c129-21.enst.fr
+  ProxyCommand ssh -W %h:%p enst

 neze@yoga ~ $ ssh room
 <username>@enst's password:
 <username>@room's password:
 c129-21%

Using a key

Using a key avoids having to type the password every time and is more secure.

You can (if you don’t already have one) generate a key. If you do not trust your computer’s safety or if you intend to use this key for critical accesses, please make sure not to use an empty passphrase.

 neze@yoga ~ $ ssh-keygen -t ecdsa -b 521
 Generating public/private ecdsa key pair.
 Enter file in which to save the key (~/.ssh/id_ecdsa):
 Enter passphrase (empty for no passphrase):
 Enter same passphrase again:
 Your identification has been saved in ~/.ssh/id_ecdsa.
 Your public key has been saved in ~/.ssh/id_ecdsa.pub.
 The key fingerprint is:
 SHA256:RFvkT4zJm42yqK8Y5Ju2Pkk4napTH8NgnGK/DW6flO8 neze@neze-yoga
 The key's randomart image is:
 +---[ECDSA 521]---+
 |        ..o      |
 |       . = +     |
 | . .    o = o    |
 |..=    .   B     |
 |.=o+    S + o    |
 |oo=o+ .. o       |
 | =+o+=. .        |
 |o +Oooo          |
 |o+Bo+=oE         |
 +----[SHA256]-----+

Then you have to copy the public key to Télécom. Do not copy this file manually, use ssh-copy-id as below.

 neze@yoga ~ $ ssh-copy-id -i ~/.ssh/id_ecdsa.pub enst
 /usr/bin/ssh-copy-id: INFO: Source of key(s) to be installed: "~/.ssh/id_ecdsa.pub"
 /usr/bin/ssh-copy-id: INFO: attempting to log in with the new key(s), to filter out any that are already installed
 /usr/bin/ssh-copy-id: INFO: 1 key(s) remain to be installed -- if you are prompted now it is to install the new keys
 
 <username>@enst's password:
 
 Number of key(s) added: 1
 
 Now try logging into the machine, with:   "ssh 'enst'"
 and check to make sure that only the key(s) you wanted were added.

Finally, make sure that your ssh config file always use the right key by modifying ~/.ssh/config as follows.

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 Host enst room
   User <username>
+  IdentityFile ~/.ssh/id_ecdsa
 
 Host enst
   HostName ssh.enst.fr
 
 Host room
   HostName c129-21.enst.fr
   ProxyCommand ssh -W %h:%p enst

Now, connection to room should be rather direct.

 neze@yoga ~ $ ssh room
 c129-21%

Accessing graphical interfaces

Graphical interfaces access can be tricky when you have to go through an intermediate server (here, enst or ssh.enst.fr). The configuration file however allows you to do this pretty easily. Now that you configured everything you can easily access graphical interfaces of room.

 neze@yoga ~ $ ssh -X room
 c129-21% eclipse          # or chromium, for example

Tunnelling

A basic use-case of tunnels is getting access to scientific paper websites like IEEE.

Assuming that you configured your ssh client, you should be able to open a socks proxy:

 neze@yoga ~ $ ssh -ND 8080 room

Do not close this terminal, then configure your web browser to use the SOCKS5 proxy 127.0.0.1:8080. On firefox, this is found in the Preferences page, Advanced section, under the Network tab. There is a Settings button to setup how Firefox connects to the Internet, and it includes a proxy configuration.

More information about SSH connections and tunnels can be found in this article or on the web.