Talk:Processors - Revision history

DavidCary: "buggy executable", "trusted"

2007-06-13T23:07:02Z

"buggy executable", "trusted"

TimBird: answer question better

2007-06-11T19:00:17Z

answer question better

TimBird: answer question

2007-06-11T18:55:48Z

answer question

New page

Is it true that the the Linux [[security]] permissions system relies on the MMU? -- DavidCary

No. --[[User:TimBird|TimBird]]

← Older revision		Revision as of 23:07, 13 June 2007
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	of the kernel or any other process. Thus it is not wise to run untrusted code		of the kernel or any other process. Thus it is not wise to run untrusted code
	on an MMU-less system. --[[User:TimBird\|TimBird]]		on an MMU-less system. --[[User:TimBird\|TimBird]]
		+
		+	So any buggy executable can bypass the normal system calls, delete files, and crash the entire system.
		+
		+	But a buggy shell script or Java app will stay confined to its own compartment by the file system permissions
		+	(unless the shell or the JVM is a buggy executable).
		+
		+	p.s.: I'm starting to hear a lot of programmers use the term "trusted".
		+	And what they mean by it is not what I (or, I suspect, you) mean by it.
		+
		+	* "The Fallacy of Trusted Client Software" by [http://www.schneier.com/essay-063.html Bruce Schneier], [http://infosecuritymag.techtarget.com/articles/august00/columns2_cryptorhythms.shtml Information Security Magazine], August 2000
		+	* [http://www.theregister.co.uk/2005/09/27/untrusted_search/ "Trusted search software labels fraud site as safe"] ... "Such incorrect classifications create a false sense of security"
		+	* [http://www.w3.org/2000/12/drm-ws/pp/cloakware.html a user that cannot be ... trusted. ... Bob must assumed to be hostile, not just naive.]
		+	* [http://www.eff.org/Infrastructure/trusted_computing/20031001_tc.php "Trusted Computing: Promise and Risk"] by Seth Schoen. "... trusted computing ... remains controversial. Some of the controversy is based on misconceptions ..."
		+
		+	--[[User:DavidCary\|DavidCary]] 02:07, 14 June 2007 (EEST)

← Older revision		Revision as of 19:00, 11 June 2007
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	Is it true that the the Linux [[security]] permissions system relies on the MMU? -- DavidCary		Is it true that the the Linux [[security]] permissions system relies on the MMU? -- DavidCary

−	No. --[[User:TimBird\|TimBird]]	+	It depends on what you mean by "security permissions". The file system permissions
		+	are enforced by the file system. Any process operating through normal system calls
		+	will be unable to open files for which is does not have appropriate security.
		+
		+	However, security between processes is NOT enforced via memory protection, since
		+	there is no memory management unit. Any process can access the memory areas
		+	of the kernel or any other process. Thus it is not wise to run untrusted code
		+	on an MMU-less system. --[[User:TimBird\|TimBird]]