Used in these environments since the usability suffers from the strict The high security requirements of government agencies and is usually Probably the best-known implementation of mandatory access control for Linux is See how modern Linux features can help overcome this binary worldview, allowingįor more fine-grained management of privileges. We’ll revisit this topic in “Advanced Permission Management” and Only share files and scripts from specific directories, only write logs to So, for example, a web server can only use ports 80 and 443, For example, with SELinuxĮnabled, mandatory access control restricts access to only those assets that are explicitly given Linux systems allow read access to almost every file and executable by “others”-that is, all users on the system. To qualify the “all-or-nothing attitude” in Linux a bit: the defaults in most That is breached: an attacker can misuse these wide privileges easily. This, naturally, has a concrete impact on a system That “process X is allowed to change networking settings,” you For example, in the general case, to enable Initially, there was no easy and flexible way to assign a You are either a superuser who has the power to change everything or you are a normal user In addition, Linux traditionally has an all-or-nothing attitude-that is, Permissions themselves, even when they own the resource. In a mandatory access control model, an admin strictly and exclusivelyĬontrols access, setting all permissions. Users can only access resources corresponding to a clearance level equal to Users are assigned aĬlearance level, and resources are assigned a security label. Mandatory access control is based on a hierarchical model representing security levels. It’s discretionary in the sense that a user with certain permissionsĬan pass them on to other users. ![]() With discretionary access control (DAC), the idea is to restrict access to resources based on the identity of Most important and relevant to our discussion in the context of Linux areĭiscretionary and mandatory access control: Discretionary access control Or maybe the access itself is even recorded.Ĭonceptually, there are different access control types. Is a clear set of rules about what kind of resources (files or syscalls) a process can access, Process directly access a resource, maybe in an unrestricted manner? Or maybe there One aspect of access control is the nature of the access itself. Laying the basis for the rest of the chapter. With that, let’s jump right into the topic of users and resource ownership, To round things off, we’ll provide some security good practices around Linux features in the access control space, including capabilities, seccomp profiles,Īnd ACLs. ![]() We’ll wrap up this chapter covering a range of advanced We’ll look at how to control access to files and how processes are impacted Then, we’ll move on to the topic of permissions, where Next, we’ll focus on the definition of a Linux user, what users can do,Īnd how to manage users either locally or alternatively from a central place. We’ll also review sandboxing and access control types. Relationship between users, processes, and files, from an access perspective. ![]() To get a handle on this topic, we’ll first take a look at the fundamental For example, a user may (or may not) be allowed to change On the system as well, what are those users allowed to do, and how is this defined andĮnforced? There are also activities that you might not necessarily associate Write to the file, and also, say, delete it. One question that immediately comes to mind in such a multiuser setup is ownership.Ī user may own, for example, a file. Resources in general and files in particular. ![]() In this chapter, we discuss the topic of users and controlling access to Scripting, we now focus on one specific and crucial security aspect in Linux. After the wide scope in the previous chapter on all things shell and
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