Re: Proposal "LUID"

From: Alan Cox (alan@lxorguk.ukuu.org.uk)
Date: Sat Apr 15 2000 - 14:37:15 EST


> are 'legal' at both the user and kernel level (UID==65535 is legal). UID==0 is not
> special in regards to auditing.

65535 is special as is 2^32-1. (uid_t)-1 (ie the unsigned cast of in our case)
is special to setuid and related calls meaning 'no change'

> 1) adding a variable "luid" to the uid_t line in the task struct
> 2) adding two system calls - 1 to 'set' and one to 'get' the value.
> 3) adding CAP_SET_LUID that allows setting setting the luid.
>
> This proposal would affect no user applications in current systems. It
> would be tamperproof on current systems by anyone not possessing CAP_SET_LUID.

Untrue. All users must lack CAP_SYS_RAWIO for this to be true, otherwise they
can use hardware to DMA back over their luid from other capabilities

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