jan31 - CS 426 class Jan 31, 2012

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CS 426 class Jan 31, 2012 www.cs.purdue.edu/homes/ssw/cs426/{index.html,syll.pdf,outline} (General purpose) Operating System security Access protection of general objects In multiprogramming, OS must protect: memory (already discussed: fence, B/B, page, seg) files or data on auxiliary storage a running program in memory a directory of files a hardware device a data structure, such as a stack OS tables (page, segm) instructions, especially privileged ones passwords and user authentication mechanism the protection mechanism itself Memory protection is simple because every access goes thru certain points in hardware Other objects: more points, more paths, hard to check all A "user" or "subject" accesses an "object" Goals in protecting objects: 1. check every access (right may have been revoked) 2. enforce "least privilege" (no extra rights - pgm can't see real address) guards against part of protection mechanism failing. 3.
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jan31 - CS 426 class Jan 31, 2012

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