Numerous Solaris customers consolidate multiple applications or servers on a single platform. The resulting configuration consists of many environments hosted on a single infrastructure and security constraints sometimes exist between these environments. Recently, a customer consolidated many virtual machines belonging to both their Intranet and Extranet on a pair of SPARC Solaris servers interconnected through Infiniband. Virtual Machines were mapped to Solaris Zones and one security constraint was to prevent SSH connections between the Intranet and the Extranet. This case study gives us the opportunity to understand how the Oracle Solaris Network Virtualization Technology —a.k.a. Project Crossbow— can be used to control outbound traffic from Solaris Zones.

Solaris Zones from both the Intranet and Extranet use an Infiniband network to access a ZFS Storage Appliance that exports NFS shares. Solaris global zones on both SPARC servers mount iSCSI LU exported by the Storage Appliance.  Non-global zones are installed on these iSCSI LU. With no security hardening, if an Extranet zone gets compromised, the attacker could try to use the Storage Appliance as a gateway to the Intranet zones, or even worse, to the global zones as all the zones are reachable from this node.

One solution consists in using Solaris Network Virtualization Technology to stop outbound SSH traffic from the Solaris Zones. The virtualized network stack provides per-network link flows. A flow classifies network traffic on a specific link. As an example, on the network link used by a Solaris Zone to connect to the Infiniband, a flow can be created for TCP traffic on port 22, thereby a flow for the ssh traffic. A bandwidth can be specified for that flow and, if set to zero, the traffic is blocked. Last but not least, flows are created from the global zone, which means that even with root privileges in a Solaris zone an attacker cannot disable or delete a flow. With the flow approach, the outbound traffic of a Solaris zone is controlled from outside the zone.

Schema 1 describes the new network setting once the security has been put in place.

Here are the instructions to create a Crossbow flow as used in Schema 1 :

(GZ)# zoneadm -z zonename halt
 ...halts the Solaris Zone.

(GZ)# flowadm add-flow -l iblink -a transport=TCP,remote_port=22 -p maxbw=0 sshFilter
  ...creates a flow on the IB partition "iblink" used by the zone to connect to the Infiniband.
  This IB partition can be identified by intersecting the output of the commands 'zonecfg -z zonename info net' and 'dladm show-part'.
  The flow is created on port 22, for the TCP traffic with a zero maximum bandwidth.
  The name given to the flow is "sshFilter".

(GZ)# zoneadm -z zonename boot
  ...restarts the Solaris zone now that the flow is in place.

Solaris Zones and Solaris Network Virtualization enable SSH access control on Infiniband (and on Ethernet) without the extra cost of a firewall. With this approach, no change is required on the Infiniband switch. All the security enforcements are put in place at the Solaris level, minimizing the impact on the overall infrastructure. The Crossbow flows come in addition to many other security controls available with Oracle Solaris such as IPFilter and Role Based Access Control, and that can be used to tackle security challenges.