Revision as of 23:07, 9 July 2017

On January 27, 2015, a vulnerability named "GHOST" in the glibc library was publicly announced. GHOST is also referred as CVE-2015-0235. The vulnerability is a buffer overflow in the gethostbyname family of functions that can allow arbitrary code execution.

Applied Products

• TMG800, TMG3200, TMG7800-CTRL
• Tdev Linux server with (CentOS, RedHat, etc) running Toolpack software

Introduction

This page discusses some means for improving the overall security of Telcobridges system against unwanted attacks and vulnerabilities with adverse exposure as introduced from internet or connecting to network in general.

Management Port Protection

Keep the management port in a protected environment (behind a firewall). Other ports do not have access to the OS (unless configured on the web portal).

SSH Access Security

Use a strong password for the SSH access.

CentOS Update for New Packages

Keep system CentOS with database and/or Ruby up to date as needed, using yum date or through web portal by doing upgrade linux packages, see Upgrade CentOS

WebPortal - TMG unit or Linux server with access to Internet (i.e. with DNS configured)

1. login onto the WebPortal
2. Select the 'Hosts' section
3. Click on the hostname
4. Click on the 'Status' tab
5. Select 'Upgrade Linux packages' into the host 'Action'
6. Click on the 'Apply action' button
7. Refresh the page until the packages are updated as indicated in the 'Action Log' (you may use the 'Now' button to update the page). The results should appear within a minute.
8. Select 'Shutdown' into the host 'Action'
9. Select 'Reboot' into the 'Shutdown Type'
10. Click on the 'Apply action' button
11. Repeat the process for all hosts listed

Command line interface

• login with root account

[root@TB011107 ~]# uname -m
x86_64

• If the result is not "x86_64", please contact TelcoBridges support, otherwise you can proceed with either method below.
• Follow one of the two options depending if Internet is accessible from the unit

Option #1 - TMG unit or Linux server with access to Internet (i.e. with DNS configured)

• update OS packages with yum

yum clean all
yum update

• reboot the unit

reboot

Option #2 - TMG unit or Linux server without access to Internet

• download the following packages to your PC:
  • http://repo.telcobridges.com/centos/5.7/updates/x86_64/RPMS/glibc-2.5-123.el5_11.1.x86_64.rpm
  • http://repo.telcobridges.com/centos/5.7/updates/x86_64/RPMS/glibc-common-2.5-123.el5_11.1.x86_64.rpm
  • http://repo.telcobridges.com/centos/5.7/updates/x86_64/RPMS/glibc-devel-2.5-123.el5_11.1.x86_64.rpm
  • http://repo.telcobridges.com/centos/5.7/updates/x86_64/RPMS/glibc-headers-2.5-123.el5_11.1.x86_64.rpm
  • http://repo.telcobridges.com/centos/5.7/updates/x86_64/RPMS/nscd-2.5-123.el5_11.1.x86_64.rpm
• Using WinSCP or similar tool, upload the files to the TMG unit using the root account
• login with root account
• Install packages

yum localinstall glibc-2.5-123.el5_11.1.x86_64.rpm \
  glibc-common-2.5-123.el5_11.1.x86_64.rpm \
  glibc-devel-2.5-123.el5_11.1.x86_64.rpm \
  glibc-headers-2.5-123.el5_11.1.x86_64.rpm \
  nscd-2.5-123.el5_11.1.x86_64.rpm

• Note: that operation might take a long time since yum will probably experience timeouts when trying to access the external repositories.
• Reboot the unit

reboot

How to verify if the vulnerability is fixed?

• login with root account
• execute the following to create a test script

cat > rhel-GHOST-test.sh << FOF
#!/bin/bash
# rhel-GHOST-test.sh -  GHOST vulnerability tester. Only for CentOS/RHEL based servers.  #
# Version 3
# Credit : Red Hat, Inc - https://access.redhat.com/labs/ghost/ #
echo "Installed glibc version(s)"

rv=0
for glibc_nvr in \$( rpm -q --qf '%{name}-%{version}-%{release}.%{arch}\n' glibc ); do
    glibc_ver=\$( echo "\$glibc_nvr" | awk -F- '{ print \$2 }' )
    glibc_maj=\$( echo "\$glibc_ver" | awk -F. '{ print \$1 }')
    glibc_min=\$( echo "\$glibc_ver" | awk -F. '{ print \$2 }')

    echo -n "- \$glibc_nvr: "
    if [ "\$glibc_maj" -gt 2 -o \( "\$glibc_maj" -eq 2  -a  "\$glibc_min" -ge 18 \) ]; then
        # fixed upstream version
        echo 'not vulnerable'
    else
        # all RHEL updates include CVE in rpm %changelog
        if rpm -q --changelog "\$glibc_nvr" | grep -q 'CVE-2015-0235'; then
            echo "not vulnerable"
        else
            echo "vulnerable"
            rv=1
        fi
    fi
done

if [ \$rv -ne 0 ]; then
    cat <<EOF

This system is vulnerable to CVE-2015-0235. <https://access.redhat.com/security/cve/CVE-2015-0235>
Please refer to <https://access.redhat.com/articles/1332213> for remediation steps
EOF
fi

exit \$rv

FOF

• Execute the script

chmod +x rhel-GHOST-test.sh
./rhel-GHOST-test.sh

• You should not see the 'vulnerable' string displayed

Verify system timezone

We found that some systems got the timezone reset to EST time after the GHOST patch procedures

• Verify the timezone on the system

date

If it differs from the original, reset the timezone using the tbtimezone script.

References

• https://www.qualys.com/research/security-advisories/GHOST-CVE-2015-0235.txt
• https://access.redhat.com/articles/1332213
• http://www.cyberciti.biz/faq/cve-2015-0235-patch-ghost-on-debian-ubuntu-fedora-centos-rhel-linux/