Wednesday, 28 June 2017

How to see Debian/Ubuntu Security advisories and receive email alerts

Security advisories are published by leading Linux O.S. distributors, announcing important security patches that should be applied as a matter of urgency to safeguard a particular piece of software and ultimately, safeguard your Linux Operating System.

Different Linux flavours can be set up to automatically email a notification to you. You can also set up automated security patching. I will show you how below.

Below are several links to visit for Security advisory notices and details.

http://www.linuxsecurity.com/content/section/3/170/ - Shows Security advisories for several flavours of Linux O.S.

https://www.debian.org/security/ - Shows Security advisories for Debian

https://www.ubuntu.com/usn/ - Shows Security advisories for Ubuntu

Prerequisites

Before we get started:

  • You have to have an SMTP server that can send the emails from your workstation, to the recipient (i.e. your corporate exchange or Gmail).
  • You have the credentials for a user that is able to send Email on that server (i.e. a mailbox or a Gmail account).

There are a few simple SMTP servers out there. The ssmtp (Simple S.M.T.P) package works well. There are better setup articles but we can quickly set it up.

To install the ssmtp (Simple S.M.T.P) package, use the following command:

sudo apt-get install ssmtp

Using your favourite editor, edit the configuration file:

sudo nano /etc/ssmtp/ssmtp.conf

Edit the following lines. The number after the colon, is the port number used to connect to your email providers SMTP service.

root=username@gmail.com
mailhub=smtp.gmail.com:587
hostname=username@gmail.com
UseSTARTTLS=YES
AuthUser=username
AuthPass=password
FromLineOverride=yes

In order to make the default (root) “from” field be the server name, edit the /etc/ssmtp/revaliases file:

root:machine-name@some-domain.com:smtp.gmail.com

Test the ssmtp setup by sending an Email:

echo "Test message using ssmtp" | sudo ssmtp -vvv your-email@some-domain.com

Security Update email alerts for Debian/Ubuntu

Apticron is a simple script which sends daily emails about pending package updates such as security updates.

sudo apt-get install apticron

Configure Apticron

sudo nano /etc/apticron/apticron.conf

Edit the following line, ‘EMAIL=’ changing it to your email address

# apticron.conf
#
# set EMAIL to a space separated list of addresses which will be notified of
# impending updates
#
EMAIL="root"
[...]

You will now receive an email alert once a day if, there are any security advisories.

Automatic Security Updates

To check if your Debian / Ubuntu system has Automatic Security Updates installed, you can manually run it with verbose.

sudo apt-get update
sudo unattended-upgrades -v

If this gives an error then, it is not installed so execute
sudo dpkg-reconfigure --priority=low unattended-upgrades

Once installed, check
cat /etc/apt/apt.conf.d/20auto-upgrades

This should result in
APT::Periodic::Update-Package-Lists "1";
APT::Periodic::Unattended-Upgrade "1";

If not, edit the file and set APT::Periodic::Unattended-Upgrade to "1".

References:
https://help.ubuntu.com/community/AutomaticSecurityUpdates
https://www.quora.com/How-can-I-get-email-alerts-for-Linux-security-patches-mainly-Ubuntu-CentOS
http://www.linuxsecurity.com/content/section/3/170/
https://www.debian.org/security/
https://www.ubuntu.com/usn/

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