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Sat, Jun 29, 2013 5:01 pm

Copying and Pasting in SSH Session on Chrome OS

To copy and paste information into an SSH session on Chrome OS, you can use ctrl-c to copy the information and ctrl-shift-v to paste the information.

[/os/chrome] permanent link

Fri, Jun 28, 2013 9:29 pm

SSH Port Forwarding for VNC under Chrome OS

If you need a Virtual Network Computing client for a Chromebook, such as the one manufactured by Acer, RealVNC provides a free one that is available through the Google Chrome Web Store. For details on the app, see VNC® Viewer for Google Chrome™.

When I used it to connect to a Mac OS X system, I was warned that the connection would not be encrypted.

Unencrypted Connection

This connection will not be encrypted. Your authentication credentials will be transmitted securely, but all subsequent data exchanged while the connection is in progress may be susceptible to interception by third parties.

That's not a significant concern for me when both systems are on a Local Area Network (LAN) I control, but I normally tunnel VNC connections through an SSH connection when connecting over the Internet to ensure transmissions are encrypted.

Chrome OS on a Chromebook contains A Secure Shell (SSH) client application. To access it, hit the Ctrl-Alt-T keys simultaneously, which will open a terminal window as a tab in the Chrome browser. Type ssh at the "crosh>" prompt to access the ssh client.

Welcome to crosh, type 'help' for a list of commands.
crosh> ssh

Within the ssh application, typing help will show you a list of the available commands.

ssh> help
connect - connect
dynamic-forward port - dynamic socks proxy (-D)
forward port:host:port - static port forward (-L)
help - this
host <hostname> - remote hostname
key <file> - sets private key to use (-i)
nocmd - don't execute command (-N)
port <num> - port on remote host (-p)
server-alive-interval <num> - set ServerAliveInterval option
exit - exit ssh subsystem
user <username< - username on remote host
Note that this program can only bind local ports in the range
8000-8999, inclusive.
ssh> 

If you wish to encrypt a Virtual Nework Computing (VNC) connection by tunneling it through an SSH connection, you will need to specify a port from 8000 to 8999 as the port to be used for forwarding the VNC traffic when using SSH under Chrome OS. You can do so using a forward command such as the following:

crosh> ssh
ssh> user JDoe
ssh> host my.example.com
ssh> forward 8000:127.0.0.1:5900
ssh> connect

Then using the RealVNC client for Chrome OS, you can specify 127.0.0.1:8000 or localhost::8000 as the address through which to establish the VNC connection. You could also have used forward 8000:localhost:5900 for the SSH forwarding command. The address 127.0.0.1 is the localhost address and with the port number of 8000 tells VNC to try establishing the VNC connection by connecting to port number 8000 on the system on which VNC is running, i.e., the Chromebook. Because there is an SSH tunnel through that port, SSH will route any traffic to TCP port 8000 through its connection to port 5900 on the remote system.

You will still get the warning from the VNC Viewer about transmissions not being encrypted when you tunnel the traffic through the SSH tunnel, but you no longer have to worry about the warning, since the traffic is going through an encrypted SSH tunnel. The VNC Viewer does not know that its transmissions are going through an encrypted tunnel; it only knows that it isn't performing any encryption.

[/os/chrome] permanent link

Sun, Jun 23, 2013 8:13 pm

Scratchpad not Synching

I've been having problems with my Chromebook after an update from Google this week. Periodically, I will lose the capability to view videos I've downloaded. A window will open for the video, but it won't play; clicking on the button to play the video will have no effect. Also, when I open the files application, it won't show the files in a directory. Shutting the system off and then restarting it can resolve the problem, though I then find that each time I do so, when I reopen the browser about half the previously opened tabs no longer appear. And, also, annoyingly, the last time I shut the system down and restarted it, about 1/2 hour's worth of notes I had taken in the Scratchpad app about 1/2 hour prior to shutting down the system had disappeared.

I checked Google Drive, but the particular Scratchpad note I had been editing wasn't there. Though Scratchpad had at one time been synchronizing between my Chromebook and Google Drive, it appeared it hadn't done so for quite some time.

I opened the Scratchpad app (version 3.1.0), which opened a new browser tab. On the left-hand side where a list of the notes I had created appeared there was also a "Scratchpad tips and tricks" note. I clicked on it; one of the options that appeared in the note was "Connect your Scratchpad to Google Docs." When I clicked on Connect, I saw that, under Options, "Sync with Google Docs" was set to "Off". I clicked on the option to change it and gave the application access to the Google Docs for my Gmail account. I then saw the option was set to "On". Hopefully, now I will have a copy of my notes on Google Docs should the problem reoccur. I recall once previously being asked what version of a note I wanted, the one stored locally or the one on Google Docs.

Note: you can also get to the setting to change the synchronization option by taking the following steps in the browser:

  1. Click on the the "Customize and control Google Chrome" button at the top, right-hand side of the browser window, the one with the 3 short horizontal bars one below the other on it.
  2. Click on Settings.
  3. Click on Extensions.
  4. Click on the Options link under Scratchpad and set the synchronization option.

[/os/chrome] permanent link

Wed, May 22, 2013 11:05 pm

Using the SSH Client on a Chromebook to Establish a Socks Proxy Connection

The Chrome OS on a Chromebook contains a Secure Shell (SSH) client application. To access it, hit the Ctrl-Alt-T keys simultaneously, which will open a terminal window as a tab in the Chrome browser. Type ssh at the "crosh>" prompt to access the ssh client.
Welcome to crosh, type 'help' for a list of commands.
crosh> ssh

Within the ssh application, typing help will show you a list of the available commands.

ssh> help
connect - connect
dynamic-forward port - dynamic socks proxy (-D)
forward port:host:port - static port forward (-L)
help - this
host <hostname> - remote hostname
key <file> - sets private key to use (-i)
nocmd - don't execute command (-N)
port <num> - port on remote host (-p)
server-alive-interval <num> - set ServerAliveInterval option
exit - exit ssh subsystem
user <username< - username on remote host
Note that this program can only bind local ports in the range
8000-8999, inclusive.
ssh> 

To establish the SOCKS proxy connection via SSH, type dynamic-forward port where port is the port number you wish to use for the SOCKS proxy. E.g., dynamic-forward 8000. Note: the help information for the SSH client states "that this program can only bind local ports in the range 8000-8999, inclusive." Then type host fqdn where fqdn is the fully qualified domain name or IP address of the system to which you wish to connect followed by user username where username is the account under which you wish to log into the SSH server. They type connect to establish the connection.

ssh> dynamic-forward 8000
ssh> host example.com
ssh> user jdoe
ssh> connect

You will be prompted for the password for the login once the Chromebook connects to the remote SSH server.

To now change the proxy settings of the Chrome browser, take the following steps:

  1. Click the network icon Chrome OS
Connection Manager in the lower-right corner of your screen.
  2. Select Settings and find the "Internet connection" section on the Settings page that appears.
  3. You will need to check the "Allow proxies for shared networks" check box if the network is shared with all users of the Chromebook. If checked, all profiles on your Chrome device will use the proxy settings set for a network. If this box isn't checked and the network is shared for all users of the Chromebook, you won't be able to configure the proxy settings, as they will be grayed out, until you check this box.
  4. Click the network for which you're using the proxy settings.
  5. Select the Proxy tab in the window that displays the network options.
  6. Configure your proxy settings by selecting the "Manual proxy configuration" option and then entering the proxy settings. For the case above, where I'm using a socks proxy created through the SSH client, I would put 127.0.0.1, which is the localhost address, in the SOCKS host field and 8000 in the port field, since that was the port I chose to use. Putting 127.0.0.1 in the host field tells the browser to establish the connection via port 8000 on the local system from which you established the SSH connection.

    Chrome OS proxy settings

    Then click on the Close button to initiate the use of the socks proxy.
  7. You can verify that you are using the socks proxy, by going to a website, such as whatismyip.com that will show you the IP address from which it sees your connection originating.

[/os/chrome] permanent link

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