authentication and authorization access control consists of two steps, authentication and...
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Authentication and authorization
Access control consists of two steps, authentication and authorization.
SubjectSubject Do operation
Do operation
Referencemonitor
Referencemonitor ObjectObject
SourceMakes an access request
Request Guard Resourcesmemoryprintersfilesnodes
Computer System Security and ManagementAccess Control
Access operations
There is two access modes:•Observe – look at the contents of an objectExample application level: select * from table (sql) or SNMP get operation•Alter – change the content of an objectExample application level: delete from table (sql) or SNMP set operation
In Linux there is three different access attributes: Read (r), Write, (w) and execute (e).And three different access groups: Owner, groups and others
For example: -rw-r--r-- 1 root root 221 Dec 18 2012 hostsThe owner of the file hosts, root, has read and write access.Groups has read access and others has read access
Computer System Security and ManagementAccess Control
Administrative access rights
Meaning of read, write and execute operations:•read – reading from file and list directories contents•write – writing to file and create or rename a file in the directory•execute – executing a (program) file and search the directory
Operations for manipulating a subject’s access rights is called grant and revoke when the subject’s rights are modified by some other party. Example root changes the ownership of a file: chown nobody:nobody /tmp/script.sh
When the owner changes his own access right operation is called assert and deny.
Computer System Security and ManagementAccess Control
Access Control Lists
An ACL corresponds to a column of the access control matrix and states who may access a given object.
ACL for process.c Bill: read, write;ACL for lists.c Alice: execute; Bill: write;
Linux access control model is based on simple ACLs.
Active Directory, AD, in Windows server uses ACL.AD uses GPO, Group Policy, to grant access to object like applications or printers to groups.
Computer System Security and ManagementAccess Control
Intermediate controls
•Group and negative permissions: Group1 in AD has access to a network disk meanwhile Group2 hasn’t.•Privileges: root access in Linux. To grant root access in Mac os X we can use the command sudo, but we need a password.•Role-Based Access Control: RBAC. In Linux root has the highest privilege or admin user in windows.
Computer System Security and ManagementAccess Control