Messages in this thread | | | Date | Wed, 7 Apr 1999 15:26:11 -0500 (EST) | From | "Mark H. Wood" <> | Subject | Re: Subject: Re: ext3 to include capabilities? |
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On Wed, 7 Apr 1999, Jonathan Corbet wrote: > In all this discussion, I'm surprised that this old idea hasn't gone by:
I am always maundering about some aspect of VMS, so I've tried to hold my tongue this time.
> Back in my VMS days (some time ago, anymore) we would deal with things > called "known images." Essentially, VMS maintained a central database of > executibles which would be run with enhanced privileges. It was your > typical opaque VMS thing behind fifteen layers of RMS stuff, but it worked, ^^^ Nope. The Known Files List is an in-core data structure only. You want an image to be known, you execute INSTALL on it every time you boot.
> and it had one distinct advantage: the system knew, at any time, what and > where *every* privileged executible was. No need for security scanners and > such, just ask.
No spoofing, either. The kernel holds an open file handle on each known file all the time it is "known". The file *cannot* be replaced unless you deINSTALL it. And the file's KFL entry is the only thing consulted when checking for amplified privileges, so privs evaporate when you deINSTALL.
> To top it off, databases like this in VMS could be set up with all kinds of > ACL traps to raise hell every time somebody changes them.
This is that heavy-duty audit stuff discussed in another recent thread. You need a certain privilege to make KFEs, and the system can be set to audit every use of that privilege.
> The downside, of course, is that a lookup has to be performed for ever > exec() the system does.
I presume that the KFL is hashed or something. The lookup is so fast I couldn't say how long it takes. The KFL only has about a hundred entries, on systems I've examined. Besides, INSTALLed images start *faster* because the file header (including a chunk of retrieval pointers) stays in core forever -- the usage count never drops to zero, y'know. Some people INSTALL a few images with no privs, just to get 'em to start faster.
-- Mark H. Wood, Lead System Programmer mwood@IUPUI.Edu Specializing in unusual perspectives for more than twenty years.
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