Setting Up Virtual Security Zones in a Linux Cluster
An increasing number of projects use Linux and other open-source software as basic building blocks to create clusters. Examples range from clusters that perform massive computations of visual effects for movies to clusters used as next-generation telecommunication servers.
More and more often, various issues, including economics, management and flexibility, require applications to run on the same physical cluster. An illustration of this situation in the telecom world is carrier-grade clustered servers shared among different operators. The operators share the global infrastructure of the cluster and provide different services to their clients but want to keep their binaries and data private. In such cases, cluster administrators do not have access to the source code for these applications, and security mechanisms cannot be enforced at the source code level. Hence, a security infrastructure is needed to ensure that a given application's resources cannot be tampered with or used by other entities on the cluster.
The Distributed Security Infrastructure (DSI) provides a solution for such a situation. It attempts to build a coherent security framework dedicated to carrier-grade Linux clusters by dividing a cluster into several virtual subclusters, guaranteeing controlled/restricted connections between them. Even though the project is only in its second year of design and development, we believe DSI is a useful tool for cluster administrators. This article presents how to use DSI to set virtual security zones inside a Linux cluster.
In this section, we briefly introduce DSI's architecture. DSI is composed of one security server (SS) and multiple security managers (SMs), one per node (Figure 1). The SS centralizes management of the cluster: it gathers alarms and warnings sent by SMs and propagates a unique security policy over the cluster. On the other hand, SMs are responsible for enforcing security on their own nodes. Furthermore, messages are exchanged between the SS and SMs over encrypted and authenticated channels, using SSL/TLS over CORBA event channels.
Security mechanisms in DSI are implemented at the process level to check the access privileges a process has to a resource. Each process is identified by its security context identifier (ScID) and the node identification on which it is running (SnID).
SnIDs are assigned using the DSI SetNodeID tool. All processes sharing the same security context are assigned the same ScID. ScIDs can be assigned automatically by the system according to DSP rules (see below), or they can be assigned specifically to a given binary using the DSI SetSID tool. This allows grouping of binaries according to their security contexts.
In DSI, writing a security policy for the cluster consists of granting or denying permissions to a given SnID and ScID pair. These rules are valid for the whole cluster. All rules are centralized in an XML file on the SS to ease management.
DSI provides a way to update and enforce transparently and automatically a unique homogeneous view of the whole cluster's security. Once the administrator modifies existing rules or adds a new rule to the distributed security policy (DSP), the DSP must be loaded on the SS using the dsiUpdatePolicy tool. Then, dsiUpdatePolicy checks the DSP file against our DSP XML schema (syntactical checks). If the DSP is validated, the SS propagates the new rules to all nodes of the cluster using the secure communication channels. Finally, each SM enforces the rules at kernel level calling the distributed security module (DSM, see Figure 2). DSM is based on the LSM kernel patch. Its detailed description is beyond the scope of this article; see the on-line Resources section for links to more information.
Controlling access to local resources is rather simple: the DSM module retrieves the local ScID and SnID of the requesting process and checks corresponding permissions in the security rules. Actually, the originality of DSI lies in distributed access control. Currently, only socket communications are implemented. To illustrate this, we detail the access control mechanisms when a process tries to access a resource located on another node (Figure 3):
The access request first is intercepted by the local DSM, which checks that the process has the privilege to call locally the socket-related systems calls.
Then, the ScID and SnID of the requesting process are added by DSM to each IP packet sent to the remote node.
On the receiving node, the remote DSM uses the ScID and SnID of the requesting process, extracted from the IP packet, to check its permission to communicate with both the target socket and the process to which the target socket belongs.
Finally, the remote DSM locally checks that the process to which the target socket belongs may receive information from the requesting process.
Fast/Flexible Linux OS Recovery
On Demand Now
In this live one-hour webinar, learn how to enhance your existing backup strategies for complete disaster recovery preparedness using Storix System Backup Administrator (SBAdmin), a highly flexible full-system recovery solution for UNIX and Linux systems.
Join Linux Journal's Shawn Powers and David Huffman, President/CEO, Storix, Inc.
Free to Linux Journal readers.Register Now!
- Download "Linux Management with Red Hat Satellite: Measuring Business Impact and ROI"
- Petros Koutoupis' RapidDisk
- The Italian Army Switches to LibreOffice
- Linux Mint 18
- ServersCheck's Thermal Imaging Camera Sensor
- Oracle vs. Google: Round 2
- The FBI and the Mozilla Foundation Lock Horns over Known Security Hole
- Varnish Software's Varnish Massive Storage Engine
- Privacy and the New Math
Until recently, IBM’s Power Platform was looked upon as being the system that hosted IBM’s flavor of UNIX and proprietary operating system called IBM i. These servers often are found in medium-size businesses running ERP, CRM and financials for on-premise customers. By enabling the Power platform to run the Linux OS, IBM now has positioned Power to be the platform of choice for those already running Linux that are facing scalability issues, especially customers looking at analytics, big data or cloud computing.
￼Running Linux on IBM’s Power hardware offers some obvious benefits, including improved processing speed and memory bandwidth, inherent security, and simpler deployment and management. But if you look beyond the impressive architecture, you’ll also find an open ecosystem that has given rise to a strong, innovative community, as well as an inventory of system and network management applications that really help leverage the benefits offered by running Linux on Power.Get the Guide