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Linux Advisory Watch: November 4th 2005 Print E-mail
User Rating:      How can I rate this item?
Source: LinuxSecurity.com Contributors - Posted by Benjamin D. Thomas   
Linux Advisory Watch This week, advisories were released for lynx, OpenSSL, gnump3d, netpbmfree, gallery, phpmyadmin, SELinux PAM Local, TikiWiki, mantis, Ethereal, XLI, libgda, ImageMagick, kernel, and wget. The distributors include Debian, Gentoo, and Red Hat.


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Hacks From Pax: SELinux And Access Decisions
Pax Dickinson

Security Contexts

SELinux makes access decisions by checking the security context of the subject (a process, sometimes associated with a user) against the action attempted (e.g. a file read) and the security context of the targeted object (such as a file or network port). These contexts are divided into three parts: a user identity, a role, and a domain or type. In the current SELinux policy, access is not restricted based on user identities, so we'll focus on roles and domains in this article.

User Roles

On an SELinux system, unlike a standard Linux system, root has no special privileges inherent to the account. SELinux privileges are denoted by a user's role. A standard user is assigned a role of user_r, which gives no special privileges. System administrator accounts are assigned a role of staff_r, which permits what is known as a "role transition" to the sysadm_r role. The sysadm_r role is the equivalent of the root account on a non-SELinux system, it has unfettered access to the system.

A staff user transitions to the sysadm_r role by using the newrole command, as shown below.

newrole -r sysadm_r

The user is then prompted for his or her password, successful entry of which will result in transition to the new role. You can view your current role by issuing an id -Z command.

Domains and Types

Domains and types are synonyms, typically the term "domain" is used when referring to processes and the term "type" is used referring to files. Types are the primary method used by SELinux to make authorization decisions. The strict policy defines relatively few users and roles, but contains hundreds of types.

Types are assigned by the security policy based on the path of the file in question, and the policy also transitions processes into an appropriate domain based on the context of the executed file and the domain of the process executing the file.

For example, the Apache webserver executable file has a type of httpd_exec_t. When that file is executed by the init process at bootup, the policy forces the new process to transition into the httpd_t domain. The httpd_t domain has the ability to read web content denoted by the httpd_content_t type, but not to change it or access any other domains not required for proper webserver operation.

You can view the type of a given file by using the -Z option of ls, and you can view the domain a process is running in by using the -Z option of ps. These -Z options are specific to SELinux and will not function on a non-SELinux system.

Read Entire Article:
http://www.linuxsecurity.com/content/view/120622/49/


LinuxSecurity.com Feature Extras:

Linux File & Directory Permissions Mistakes - One common mistake Linux administrators make is having file and directory permissions that are far too liberal and allow access beyond that which is needed for proper system operations. A full explanation of unix file permissions is beyond the scope of this article, so I'll assume you are familiar with the usage of such tools as chmod, chown, and chgrp. If you'd like a refresher, one is available right here on linuxsecurity.com.

Introduction: Buffer Overflow Vulnerabilities - Buffer overflows are a leading type of security vulnerability. This paper explains what a buffer overflow is, how it can be exploited, and what countermeasures can be taken to prevent the use of buffer overflow vulnerabilities.

Getting to Know Linux Security: File Permissions - Welcome to the first tutorial in the 'Getting to Know Linux Security' series. The topic explored is Linux file permissions. It offers an easy to follow explanation of how to read permissions, and how to set them using chmod. This guide is intended for users new to Linux security, therefore very simple. If the feedback is good, I'll consider creating more complex guides for advanced users. Please let us know what you think and how these can be improved.

 

Take advantage of our Linux Security discussion list! This mailing list is for general security-related questions and comments. To subscribe send an e-mail to security-discuss-request@linuxsecurity.com with "subscribe" as the subject.

Thank you for reading the LinuxSecurity.com weekly security newsletter. The purpose of this document is to provide our readers with a quick summary of each week's most relevant Linux security headline.


   Debian
  Debian: New lynx packages fix arbitrary code execution
  27th, October, 2005

Updated package.

http://www.linuxsecurity.com/content/view/120671
 
  Debian: New OpenSSL packages fix cryptographic weakness
  27th, October, 2005

Updated package.

http://www.linuxsecurity.com/content/view/120672
 
  Debian: New lynx-ssl packages fix arbitrary code execution
  27th, October, 2005

Updated package.

http://www.linuxsecurity.com/content/view/120676
 
  Debian: New gnump3d packages fix several vulnerabilities
  28th, October, 2005

Updated package.

http://www.linuxsecurity.com/content/view/120680
 
  Debian: New netpbm-free packages fix arbitrary code execution
  28th, October, 2005

Updated package.

http://www.linuxsecurity.com/content/view/120686
 
  Debian: New gallery packages fix privilege escalation
  2nd, November, 2005

Updated profile.

http://www.linuxsecurity.com/content/view/120701
 
  Debian: New phpmyadmin packages fix several vulnerabilities
  2nd, November, 2005

Updated profile.

http://www.linuxsecurity.com/content/view/120703
 
   Gentoo
  Gentoo: SELinux PAM Local password guessing attack
  28th, October, 2005

A vulnerability in the SELinux version of PAM allows a local attacker to brute-force system passwords.

http://www.linuxsecurity.com/content/view/120681
 
  Gentoo: TikiWiki XSS vulnerability
  28th, October, 2005

TikiWiki is vulnerable to cross-site scripting attacks.

http://www.linuxsecurity.com/content/view/120684
 
  Gentoo: Mantis Multiple vulnerabilities
  28th, October, 2005

Mantis is affected by multiple vulnerabilities ranging from information disclosure to arbitrary script execution.

http://www.linuxsecurity.com/content/view/120685
 
  Gentoo: Ethereal Multiple vulnerabilities in protocol dissectors
  30th, October, 2005

Ethereal is vulnerable to numerous vulnerabilities, potentially resulting in the execution of arbitrary code or abnormal termination.

http://www.linuxsecurity.com/content/view/120689
 
  Gentoo: XLI, Xloadimage Buffer overflow
  30th, October, 2005

XLI and Xloadimage contain a vulnerability which could potentially result in the execution of arbitrary code.

http://www.linuxsecurity.com/content/view/120690
 
  Gentoo: libgda Format string vulnerabilities
  2nd, November, 2005

Two format string vulnerabilities in libgda may lead to the execution of arbitrary code.

http://www.linuxsecurity.com/content/view/120712
 
  Gentoo: QDBM, ImageMagick, GDAL RUNPATH issues
  2nd, November, 2005

Multiple packages suffer from RUNPATH issues that may allow users in the "portage" group to escalate privileges.

http://www.linuxsecurity.com/content/view/120713
 
   Red Hat
  RedHat: Important: kernel security update
  27th, October, 2005

Updated kernel packages that fix several security issues and a page attribute mapping bug are now available for Red Hat Enterprise Linux 4. This update has been rated as having important security impact by the Red Hat Security Response Team.

http://www.linuxsecurity.com/content/view/120677
 
  RedHat: Moderate: curl security update
  2nd, November, 2005

Updated curl packages that fix a security issue are now available. This update has been rated as having moderate security impact by the Red Hat Security Response Team.

{mos_sb_discuss:13}

http://www.linuxsecurity.com/content/view/120707
 
  RedHat: Important: wget security update
  2nd, November, 2005

Updated wget packages that fix a security issue are now available. This update has been rated as having important security impact by the Red Hat Security Response Team.

http://www.linuxsecurity.com/content/view/120708
 
  RedHat: Important: openssl security update
  2nd, November, 2005

Updated OpenSSL packages that fix a remote denial of service vulnerability are now available for Red Hat Enterprise Linux 2.1 This update has been rated as having important security impact by the Red Hat Security Response Team.

http://www.linuxsecurity.com/content/view/120709
 
  RedHat: Moderate: openssl096b security update
  2nd, November, 2005

Updated OpenSSL096b compatibility packages that fix a remote denial of service vulnerability are now available. This update has been rated as having moderate security impact by the Red Hat Security Response Team.

http://www.linuxsecurity.com/content/view/120710
 

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