yum-security

yum-security is a plugin to the Red Hat Entreprise Linux package manager yum. It helps installing only security updates (RHSA) (as opposed to bug fixes (RHBA) or enhancements (RHEA)).
Explanation of RHSA, RHBA and RHEA advisories

RHEL 7 : yum-security is part of yum

RHEL 6 : yum install yum-plugin-security

    List all available erratas without installing them :

    yum updateinfo list available

    List all available security updates without installing them :

    yum updateinfo list security all
    yum updateinfo list sec

    List of the currently installed security updates :

    yum updateinfo list security installed

More examples are available in this Red Hat KB article

Red Hat Security Data API

Red Hat has been provided security information since January 2005 through different ways :
RHSA-Announce mailing list, Red Hat CVE database and Red Hat Product Errata

For a better access of their data, the Red Hat Product Security has just released a beta API. It provides more search options for accessing real-time data.

More details can be found in the post below :
Red Hat Security Blog post about their new Security Data API service
RedHat Security Data API

Getting more details about Red Hat Security Advisories and related CVEs

Two links for an in-depth explanation regarding Red Hat backporting security fixes process as well as compatibility between Red Hat security advisories and Mitre CVEs.

Backporting Security Fixes

Red Hat and CVE compatibility

Red Hat provides free access to two databases for errata and for CVE referenced in Red Hat products :

Red Hat Product Errata database

Red Hat CVE Database

Apache HTTPD : ETag Inode Information Leakage

Apache HTTPD : ETag Inode Information Leakage

This is an error that occurs during PCI scans. To remediate it, disable the ETag feature in your Apache configuration file.

Add FileETag None to /etc/httpd/conf/httpd.conf and restart your Apache server :

echo 'FileETag None' >> /etc/httpd/conf/httpd.conf

service httpd restart

Check if the ETag information are present in the http headers sent by your Apache serverĀ  :

curl -I https://your_server_name/ -k

 

 

CIFS NULL session permitted

How to disable CIFS NULL session permitted on a Linux server to meet compliance requirements ?

rpcclient can help retrieve details about this server. Log in with an anonymous user :

rpcclient -U "" server_name

Once logged in, run either of these commands :

srvinfo
querydominfo

To leave rpcclient, run the quit command.

If you were able to logged in and if any of the commands display details, then CIFS null session is permitted.

To disable it, add the following parameters to your smb.conf file :

guest account = nobody
restrict anonymous = 1

Check Samba configuration file syntax with :

testparm smb.conf

Restart Samba daemons :

service smb restart
service nmb restart
service winbind restart

Run once again any of the commands within a new rpcclient session.
Any information should be available now.

Disabling TLS/SSL Birthday attacks on 64-bit block ciphers (SWEET32) in Apache in CentOS 7.2.1511

To disable TLS/SSL Birthday attacks on 64-bit block ciphers (SWEET32) in Apache in CentOS 7.2.15111, remove any DES-based ciphers in your Apache ssl configuration file :

[root@localhost:~]# cat /etc/httpd/conf.d/ssl.conf
SSLHonorCipherOrder on
SSLCipherSuite ECDH+AESGCM:DH+AESGCM:ECDH+AES256:DH+AES256:ECDH+AES128:DH+AES:RSA+AESGCM:RSA+AES:!aNULL:!MD5:!DSS

Make sure that your httpd config file syntax is OK :
[root@localhost:~]# apachectl configtest

Restart your web server :
[root@localhost:~]# systemctl restart httpd.service

Run a nmap scan with ssl-enum-ciphers script enabled :

[root@localhost:~]# nmap --script ssl-enum-ciphers -p 443 server_fqdn |grep 3DES

No DES-based ciphers should be displayed.