Open System Services NFS Management and Operations Guide

5 OSS NFS Security
This chapter gives an overview of OSS NFS security from a management and operations viewpoint
and explains the security weaknesses of a LAN environment. Note that throughout the following
discussion, named objects are created by SCF commands. For details of commands and the objects
they create, see the Open System Services NFS SCF Reference Manual.
Process Security
The SUID attribute specifies that a process executing a file takes on the identity of the file’s owner,
instead of the identity of the user executing the file. (It is similar to the Guardian PROGID.) This
attribute enables you to build objects that access secure files without giving the access privileges
to the calling processes.
TCP/IP Security
Both TCP and UDP protocols reserve a range of privileged ports that only privileged processes can
access. NonStop TCP/IP requires that a process be a member of the super group to use a privileged
port. Programs can check whether a request comes from a privileged port and therefore from a
privileged program (such as the operating system) or from a nonprivileged user process (a security
suspect).
Because the port mapper protocol uses a privileged port, its process must run under a super-group
ID.
OSS NFS Data Security
OSS NFS provides three kinds of data security:
• Export control: A fileset is available to OSS NFS clients only when it has been exported by
the host on which its server runs. When the fileset is not exported, it is protected from any
access by any client.
• Fileset-access control: Permits only authorized OSS NFS clients to access a protected OSS
NFS fileset and only for the purpose for which they are authorized: read, write, or execute.
• File-creation control: Permits only authorized clients to create a file in a protected OSS NFS
fileset and so prevents pollution of these filesets.
The Safeguard product offers additional fileset-access security, in the form of more extensive and
refined authorization types. For more information, see the Security Management Guide.
Export Control
For an OSS NFS client to access a file, the client must mount the fileset that includes that file, which
is possible only if that fileset’s server has been exported to the client’s host. Therefore, when a
server exports file hierarchies, it lists the directories that clients can mount.
OSS NFS uses EXPORT objects to grant or deny mount requests from clients. EXPORT objects
specify a list of hosts and netgroups that are granted mount permission for a given file system.
The OSS NFS LAN interface process can also deny mount access if the client IP address is not
defined in the NonStop TCP/IP host file or if the IP address does not match the client machine
name. This feature is enabled by setting the CHECK-ADDR attribute of the LAN object to ON.
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