Tag: SSH

Categories
Hardware

Netgear GSM7224 v1

Originally written in 2018. This post was languishing in drafts for a couple of years. I may complete it someday.

I acquired three old Netgear GSM7224 switches for my lab network some time ago and I pulled them off the shelf recently to use in a project I am currently working on. I wish I had actually checked them out fully when I first acquired them because it has cost me a week or so in time to get them useable in a reasonably secure test network. I did not anticipate the problems getting older high-end Netgear products to work securely in a network environment with up to date patched hosts.

Netgear GSM7224 Ethernet Switch
Netgear GSM7224 installed in test lab

If you are trying to make use of ageing Netgear GSM7224 Gigabit Ethernet Managed Switches you may find this article useful. Some of this may even be relevant to other network equipment running similar firmware Eg. Sun Netra.

Observations

I spent a little time getting familiar with one of the switches on my bench. I used a laptop running Ubuntu 18.04 with a USB Serial adapter and a 9-pin null modem serial cable connected to the switch’s console port on the front panel. As these were second hand switches I didn’t have knowledge of the existing admin password. Resetting the password was at the top of the task list but until then it was time to do some basic surveilance on the switch using nmap. These are my initial observations.

  • Noisy or failed fans
  • Slow start-up time
  • Old firmware. The latest 2007 version is still available for download
  • Log files are time and dated from 1 Jan 1970 at start-up
  • Awful Netgear documentation, lots of critical configuration information undocumented
  • Telnet running on tcp 23
  • No SSH v2 access
  • Unencrypted web management interface on tcp 80
  • No HTTPS for web interface
  • Mysterious tcp 4242 port listening
  • Web Management prompts for Java plugin but 2018 browsers are not able to run Java applets

Objectives

  1. Reset passwords on all switch login accounts
  2. Replace fans with new parts
  3. Document out of band command line management via the serial console
  4. Upgrade firmware to latest version
  5. Fix the time stamps in the log files
  6. Fix the Java plugin requirement
  7. Configure in-band management only from the management VLAN 1 with no internet access
  8. Enable SSH v1 safely via a bastion host running SSH v2
  9. Enable HTTPS web interface only over management VLAN
  10. Disable less secure management interfaces, telnet and unencrypted web management
  11. Enable remote syslog
  12. Enable SNMP

Tools and Equipment Required

  • Netgear GSM7224
  • The latest firmware for the switch. At the time of writing this was 6.2.0.14
  • Laptop or desktop computer that has a terminal emulator.
  • Oracle VirtualBox to host an old distro that has an SSH v1 client or a Windows PC with PuTTY.
  • CD-ROM or ISO image file for an old 32-bit Linux or FreeBSD distribution that was released between 2006 and 2007. This is primarily for using OpenSSL and OpenSSH from this period to fully configure the switch. I used Ubuntu 6.06 LTS x86 as this was still downloadable in 2018
  • 9-pin serial null modem cable.
  • USB to Serial adapter if your computer does not have a native serial port.
  • VT100 terminal emulation program that can connect to the switch’s console session via your serial connection. I used Minicom that was installable from the Ubuntu repos.
  • Netgear GSM7224 Administrators Guide
  • Netgear GSM7224 Command Line Reference
  • nmap or zenmap (GUI version) for testing

Optional Requirements

  • A compatible Java Plugin for a web browser that shipped with your 2006 Linux distro. If you want to try the Java applet function in the switch’s web interface
  • Wireshark if you want or need to decode further the SSH protocol between your switch and ssh clients

Replace the Noisy Fans

All three of my switches had noisy fans. Each has two 40x40x10mm 5VDC 2-pin fans inside and one in each had partially seized which was causing a lot of noise.

Opening the case was just a bit of screwdriver work to remove the rack mounting ears and then the screws holding the case together. All of the externally visible screws have to be removed to open the case. The cover slides off rearwards with a slight upward tilt. Once inside I could see the fans that need replacing.

I opted for cheap replacement fans sourced from eBay but I probably should have put more thought into that decision at the time. Within a few months the replacement fans started getting noisy.

I wish I had documented the fan replacement fully as I am going to use one of these switches again in November 2024. I originally installed brass inserts into the plastic housings of the 40mm fans to enable them to attached with screws to the chassis. I am guessing that the inserts are M3 thread and approximately 4mm deep. I have ordered some more for another set of new fans.

Gain Console Access

I connected a 9-pin null modem serial cable that I use for console access to the switch and to a USB serial adapter plugged into my laptop.

I use Minicom as a terminal emulator to access my switch consoles. Ctrl-A in Minicom gains access to its configuration menu. The connection was configured for /dev/ttyUSB0 at 9600,n,8,1. After saving the settings the switch console login prompt appeared.

My Netgear switches were all purchased used without documentation or being reset to factory defaults. I tried logging in as admin with various popular passwords without luck. Fortunately, rebooting the switches with Minicom still connected and running reveals a boot menu. Select option 2 to access a configuration menu. From here the switch can be reset to factory defaults without needing a password.

Update Firmware

I downloaded the ‘latest’ firmware from Netgear and setup a TFTP server on my laptop to serve the new firmware image. The firmware’s README describes the process to upgrade and although it takes a while silently updating there is eventually some confirmation on screen and the job is done.

I was having problem getting the SNTP client to synchronise time with the NTP servers that I had specified to use. That was until I tried this configuration command that worked…

(GSM7224) (config)# sntp client mode unicast

I also had some problems getting recent SSH clients to work. PuTTY on a Windows machine was useful as is still support SSH v1.

Port scanning the switch revealed that tcp 4242 appears to be used by the switch’s Java client interface. As I am not using the Java client it can be closed using:

no ip http java

More to follow…

Categories
Hardware

FOXSAT-HDR Dropbear SSH with keys

WARNING: This article relates to the dropbear package version 2012.55 and not the updated package 2012.55-1 that now includes the ability to login with keys. It is no longer necessary to use these instructions to modify the dropbear installation on your FOXSAT-HDR. The instructions on how to generate and distribute client keys are still valid.

I have just upgraded the functionality of my Humax FOXSAT-HDR with some custom firmware. The new firmware came with Telnet active but I prefer to use SSH with RSA or DSA keys. Dropbear is the installable package that provides SSH for the custom firmware but I couldn’t find any documentation with the firmware that explained how to get it working with client keys.

Following an evening of research and experimentation, I found a way of getting it to work. Ubuntu/Linux/BSD users can use this process to configure Dropbear on the FOXSAT-HDR to use SSH authorized_keys instead of passwords. I worked around the read-only file system by changing the root account home directory to /tmp.

Install Dropbear on your custom firmware FOXSAT-HDR using opkg or the web interface. Test that it works using a password. Dropbox appears to be configured to use only the root account. From my Ubuntu machine I login from a terminal session using:-

ssh root@foxsat-hdr

When you are happy it is working OK. Open another terminal session and create a DSA public key file on your Ubuntu PC. The file will be ~/.ssh/id_dsa.pub

cd
cd .ssh
ssh-keygen -t dsa
ls

Copy the key(s) to the FOXSAT-HDR. You may already have a public RSA key present in the .ssh folder.

scp id_*.pub root@foxsat-hdr:/tmp

If you are not already logged in to the FOXSAT-HDR via SSH, do so now to create the two authorized_keys files required.

cd /opt/etc
mkdir .ssh
chmod 700 .ssh
cd .ssh
cat /tmp/id_*.pub >> authorized_keys
chmod 600 authorized_keys
ln -s /opt/etc/.ssh/authorized_keys /opt/etc/.ssh/authorized_keys2

Create an init.d script to fix the keys on startup. The root account will have it’s home directory moved to /tmp so that the hidden key folder can be found in there. The ‘echo’ command line is quite long and ends in ‘fix’, it is not two lines.

echo -e "#!/bin/sh\n\nln -s /opt/etc/.ssh /tmp/.ssh">/opt/etc/init.d/S55sshpubkeyfix

chmod 755 /opt/etc/init.d/S55sshpubkeyfix

Now edit the password file using vi to change the root account home directory from ‘/’ to ‘/tmp’. If you don’t know how to use vi, read this first. Otherwise, here is a command list to refresh your memory.

cp /opt/etc/passwd /opt/etc/passwd.old
vi /opt/etc/passwd

When you have saved the file. Check it, then reboot if it is good.

cat /opt/etc/passwd
reboot

Your FOXSAT-HDR will reboot and you should be able to login using SSH. This time switch on debugging to check the authentication sequence during login. If it works, you will not have to use a password to establish a secure shell.

ssh -vv root@foxsat-hdr

Telnet can be deactivated using ‘Service Management’ in the web interface.

I have more than one SSH client

If you want to use SSH from another Ubuntu PC it is easy to copy its DSA client key to the FOXSAT-HDR now that the authorized_keys file has been created.

ssh-keygen -t dsa
ssh-copy-id root@foxsat-hdr

Improvement

This could be incorporated into the Dropbear package if the maintainer emptied the authorized_keys file (zero length) before sealing the package file. Users would then only need to use ssh-keygen and ssh-copy-id to make use of the additional security.

Categories
Hardware

Custom firmware for Humax FOXSAT-HDR

I have been using my Humax FOXSAT-HDR since I bought it new in 2009 and functionally it hasn’t changed much bar the addition of BBC and ITV catch-up TV services. I have always hoped that the manufacturer would issue a DLNA server upgrade to the firmware, but it never came. That is until today…

While searching the internet to find if the Freesat+ YouTube player was available for the FOXSAT-HDR, I found a custom firmware distribution that has been in development and use for some years that could be used to provide web access and DLNA services.

There is no dedicated website for the firmware but it appears the www.avforums.com is the place to go for community support and the latest downloads.

The version that I downloaded and installed was v4.1.1 . It came in a RAR file that I decompressed into a folder on one of my Ubuntu machines. I copied the files to a 1.1GB USB stick formatted FAT32 as advised in the README but it wouldn’t boot the new firmware installer. I found another stick that was 985MB when formatted and it worked perfectly. The installation was exactly as described in the instructions and when the FOXSAT-HDR rebooted there was no visible change other than the firmware version being displayed on the front panel during boot up.

Pointing a web browser at the box, I continued to install the full web interface. When complete I could see that the DLNA server was an installable package but I couldn’t get the package list to update from the web interface. No problem, I telneted into the box and used the command line instead.

opkg update
opkg list
opkg install dropbear

I installed dropbear so that I could deactivate Telnet and use SSH instead. More on this later.

After installing dropbear via the command line the web interface tabs for ‘Installed’, ‘Available’ and ‘Upgrades’ worked but the main ‘Update package list from internet’ still doesn’t work from the web interface.

I am currently experimenting with MediaTomb uPNP to serve recordings to my son’s PS3 but I think I will try the TwonkyMedia 5 DLNA server as originally planned. Twonky charge 15 Euros for the licence activation but I guess it’s probably worth it.

If you wish to rollback to the original firmware, you will need an installable image of it. I found one that I could download v1.00.21 from here.

3 May 2015
I should have updated this a long time ago as I have since upgraded my Foxsat-HDR to v4.1.2 and then on to v4.1.3
I am really impressed with the current version. Everything works well as flashed and with the addition of some of my own custom modifications to get it working with my WDTV-Live box.

Categories
Security Ubuntu

Ubuntu 10.10 SSH login message fix

Do you get two welcome messages when logging in to your Ubuntu 10.10 host? I have experienced it on hosts upgraded from 10.04 and on freshly built hosts from the downloaded CD-ROM images. The problem can be easily fixed using…

sudo rm /etc/motd.tail

If you are still using password based login for SSH, consider using key based logins instead. It is very easy to set up, convenient to use and secure. If you also use PuTTY on a Windows PC you can use Pageant as the automatic authentication agent.