Re: Basic questions about LSM architecture.

From: Stephen Smalley (sdsat_private)
Date: Mon Nov 26 2001 - 09:52:00 PST

  • Next message: Stephen Smalley: "Re: Basic questions about LSM architecture."

    On Sun, 25 Nov 2001, rhys tucker wrote:
    > superuser logic. The first security module overrides the dummy module by
    > redirecting security_operations to itself. Security modules may
    > implement different security polcies and may be stacked i.e. SELinux,
    > capabilities and DTE security modules may be in effect at the same time
    > (although I don't know if such a configuration is sensible).
    Just to clarify about stacking:  you can easily stack most security
    modules with either the dummy (traditional superuser) module or
    the capabilities module because these two modules do not use the security
    fields added by LSM.  So you can stack SELinux or DTE with capabilities.
    But stacking two security modules that both use the security fields
    requires that the two security modules use a shared convention for using
    the security field, e.g. a common security object header with a module
    identifier and a link for chaining multiple security objects on a single
    security field.  I don't think that anyone has done this yet, so you can't
    just stack SELinux and DTE.
    Also, you can implement multiple security policies within a single
    security module.  SELinux provides a flexible nondiscretionary access
    control architecture that cleanly separates policy definition from policy
    enforcement, so you can implement many different kinds of policies within
    its framework.  The security policy in SELinux is encapsulated in a
    separate component called the security server, and an example security
    server is provided that implements a combination of Role-Based Access
    Control, Type Enforcement, and optionally Multi-Level Security.
    Stephen D. Smalley, NAI Labs
    linux-security-module mailing list

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