1 / 18

In tr oduction

SECURITY ISSUES Access Control List & Audit Trail UNIX & Windows2000 Arun Asokan Karthikeyan Chandrasekaran Ramaselvi Balasubramanian. In tr oduction. The goals: Information Confidentiality System Integrity System Availability

millie
Download Presentation

In tr oduction

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. SECURITY ISSUESAccess Control List & Audit Trail UNIX & Windows2000Arun Asokan Karthikeyan Chandrasekaran Ramaselvi Balasubramanian

  2. Introduction The goals: • Information Confidentiality • System Integrity • System Availability • They are mutually dependent • Confidentiality achieved by ACCESS CONTROL

  3. Access ControlCollection of mechanisms that permits managers of a system to exercise a directing influence over the behavior, use and content of the system • System Access Control • Password and other authentication • System Auditing • Discretionary Access Control • Access Control List • Mandatory Access Control • Reference Monitor

  4. UNIX File System • Ordinary files • Directory files • Special files • Pipes

  5. Basic Access Control • 1 : Type of file. • 2 – 4 : Owner’s permission. • 5 – 7 : Group’s permission. • 8 – 10 : Other’s permission.

  6. Access Control ListUNIX • An access control list (ACL) is an ordered list of access control entries (ACEs) that define the protections that apply to an object and its properties • ACLs entry contains • Attributes: Defines special file modes such as SETUID, SETGID & Sticky bit • Base permissions: Reflect the basic access rights • Extended permissions: specify, permit, deny

  7. Access Control List .

  8. Auditing • Is a feature which provides accountability to all system activities from file access to network and database • Each audit event such as user login is formatted into fields such as the event type, user id, file names and time • Audit events • Administrative event class • Security administrator events • System administrator events • Operator events • Audit event class • Describes the operation of the audit system itself

  9. Audit Trail • Record of both completed and attempted access and service chronological record of system activities • Enables reconstruction and examination of the sequence of events and changes in audit event • Monitoring system changes • Files system permission & checksum should be set, snapshots taken & made read only • Snapshots are made regularly and compared with the original for changes Eg: tripwire, rdist utility, securemax (from open Vision), ESM….

  10. Windows2000 File System • Supports two file system • FAT (File Allocation Table) • File system does not record security information such as owner or access permission of a file or directory • NTFS (New Technology Files System) • Supports a variety of multi-user security models • NTFS Vs FAT • Fault tolerance • Access Control by directory or file • Can compress individual or directories • POSIX support

  11. Access Control List • Data structure of an ACL • ACL size - # of bytes of memory allocated • ACL Revision – revision # for the ACL’s data structure • ACE Count - # of ACE’s in the ACL

  12. Access Control Entries Contains the following access control information • A security identifier (SID) • An access mask – specifies access rights • A set of bit flags that determines which child objects can inherit the ACE • A flag that indicates the type of ACE

  13. ACE Types • 3 Generic types • 3 Object-Specific ACE types

  14. Access Rights • Generic Access Rights • Standard Access Rights • Other rights like, SACL access rights, Object-specific access rights, user rights

  15. How Access Control Works?

  16. Access Checking & Audit Generation • Function “AccessCheckAndAuditAlarm” determines whether the subject is allowed or denied access and then determines is there a need to generate an auditing entry in the security log. • It considers the following • Subjects access token • Subject’s desired access mask (a data structure 32 bit log, each bit corresponding to a particular access rights) • Object’s security descriptor • After the access-checking is complete, this function returns a granted access mask (it is identical to desired access mask except that all bits are initially turned off)

  17. Auditing • Here, we generate entries in the security log for successful or failed attempts to access an object • After the access checking is over, the function will tell us what need to be logged in • Subject’s access token • Desired access mask – subject • Granted access mask – access check • Object’s SACL

  18. Conclusion • UNIX Vs Win2000 • Easy to control system configuration on UNIX • ACL's are much more complex than traditional UNIX style permissions • In basic UNIX, it is impossible to give a number of users different access rights

More Related