Security-Enhanced Linux
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Security-Enhanced Linux (SELinux) is a version of the Linux kernel and utilities, which contains support for mandatory access controls based on the principle of least privilege. Primarily developed by the US National Security Agency (NSA) it was released to the open source development community. Other significant contributors include Network Associates, Secure Computing Corporation, and Tresys. Experimental ports of the FLASK/TE implementation have been made available via the TrustedBSD Project for the FreeBSD and Darwin operating systems.
- From NSA Security-enhanced Linux Team (http://www.nsa.gov/selinux/):
- "NSA Security-enhanced Linux is a set of patches to the Linux kernel and some utilities to incorporate a strong, flexible mandatory access control (MAC) architecture into the major subsystems of the kernel. It provides a mechanism to enforce the separation of information based on confidentiality and integrity requirements, which allows threats of tampering and bypassing of application security mechanisms to be addressed and enables the confinement of damage that can be caused by malicious or flawed applications. It includes a set of sample security policy configuration files designed to meet common, general-purpose security goals."
Security-enhanced Linux is a research prototype of the Linux kernel and a number of utilities designed to demonstrate the value of mandatory access controls to the Linux community and how such controls could be added to Linux. The prototype kernel contains architectural components originally developed to improve the security of the Flask operating system. These provide general support for enforcing many kinds of mandatory access control policies, including those based on the concepts of type enforcement, role-based access control, and multi-level security. Observers of operating system security research may recall DTOS, a Mach-derived Distributed Trusted Operating System, on which Flask was based, as well as Trusted Mach, a research project from Trusted Information Systems that was influencial in the design and implementation of DTOS. Those interested in Type Enforcement may also be interested in Domain and Type Enforcement.
The SE Linux kernel enforces mandatory access control policies that confine user programs and system servers to the minimum amount of privilege they require to do their jobs. This reduces or eliminates the ability of these programs and daemons to cause harm when compromised (via buffer overflows or misconfigurations, for example). This confinement mechanism operates independently of the traditional Linux access control mechanisms. It has no concept of a "root" super-user, and does not share the well-known shortcomings of the traditional Linux security mechanisms (such as a dependence on setuid/setgid binaries).
The security of an unmodified Linux system depends on the correctness of the kernel, all the privileged applications, and each of their configurations. A problem in any one of these areas may allow the compromise of the entire system. In contrast, the security of a modified system based on the security-enhanced Linux kernel depends primarily on the correctness of the kernel and its security policy configuration. While problems with the correctness or configuration of applications may allow the limited compromise of individual user programs and system daemons, they do not pose a threat to the security of other user programs and system daemons or to the security of the system as a whole. SELinux merged with the 2.6 series Linux Kernel.
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Features
- Clean separation of policy from enforcement
- Well-defined policy interfaces
- Independent of specific policies and policy languages
- Independent of specific security label formats and contents
- Individual labels and controls for kernel objects and services
- Caching of access decisions for efficiency
- Support for policy changes
- Controls over process initialization and inheritance and program execution
- Controls over file systems, directories, files, and open file descriptions
- Controls over sockets, messages, and network interfaces
- Controls over use of "capabilities"
Implementations
SE Linux is available with commercial support as part of Red Hat Enterprise Linux version 4.
In community supported Linux distributions it has been available in Fedora Core since version 2, it is part of Hardened Gentoo and work is proceeding on making it part of Debian
See also
External links
- US National Security Agency's Security-Enhanced Linux website (http://www.nsa.gov/selinux/)
- NSA press release: NSA shares security enhancements to Linux (http://www.nsa.gov/releases/selinux_01022001.html)
- FreshMeat's Security-Enhanced Linux project page (http://freshmeat.net/projects/selinux/)
- SELinux (UnOfficial) FAQ (http://www.crypt.gen.nz/selinux/faq.html)
- SELinux demo machine -- Fedora-based (http://www.coker.com.au/selinux/play.html)
- SELinux demo machine -- Debian-based (http://selinux.simplyaquatics.com/)
- SELinux demo machine -- Gentoo-based (http://selinux.dev.gentoo.org/)
- SEBSD (http://www.TrustedBSD.org/sebsd.html)
- SEDarwin (http://www.TrustedBSD.org/sedarwin.html)de:SELinux