Open System Services Porting Guide (G06.24+, H06.03+)

Porting UNIX Applications to the OSS Environment
Open System Services Porting Guide—520573-006
7-9
Security Model
Security Model
A common security model is implemented across the OSS and Guardian
environments. An object-oriented, access control mechanism is used in which the
attributes of the object, rather than the function used to access the object, determine
who can access the object; the security model of the target object applies. With this
security model, the Guardian access rules are used to access Guardian objects, and
the OSS access rules are used to access OSS objects. For OSS objects (files,
processes), the security mechanism used is identical to that used in other UNIX
environments. Security discussions related to accessing objects within the OSS and
Guardian environments follow.
Process-Identity Attributes
Process identity attributes are stored in the process control block for each process.
These are used to identify the user, the primary group to which the user belongs, and
the supplementary groups to which the user belongs. The process identity attributes
are used to determine which rights a user has as the owner of the process.
Process-identity attributes relevant in the OSS and Guardian environments are:
•
Authentication type
•
Effective user ID (EUID)
•
Effective group ID (EGID)
•
Group list
•
Logon name
Other process-identity attributes that are mostly useful in the OSS environment are:
•
Real user ID (RUID)
•
Real group ID (RGID)
•
Saved-set user ID (SSUID)
•
Saved-set group ID (SSGID)
OSS functions such as getpwnam(), getuid(), and so on, can be used to access
information about the user, alias, group, and other relevant process-identity attributes.
File Attributes and Access
OSS files have different attributes than Guardian disk files. For example, the file
protection bits, the file owner ID, and the group ID are stored differently for OSS files
than for Guardian disk files.
Guardian files are protected by a 12-bit security vector and optionally by the Safeguard
Access Control Lists (ACLs). The ACLs are associated with Guardian files.
The security vector associated with a Guardian file consists of four 3-bit permission
fields, one field for each permission: Read, Write, Execute, and Purge. The seven
classes of accessors (any, community, group, network, owner, super, user) are
encoded in the three bits.