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SubjectRe: BEWARE! Linux seteuid is broken!

> Possibly not but be incredibly careful when fiddling with this code
> especially with saved uids and exec

I am... 8)

I killed a lot of time searching for setreu(g)ids at my site
and replacing them with seteu(g)ids. It was not easy, I was forced
to port TIRPC and make RPC via UNIX sockets to pass credentials
in secure fashion. I hope it was not just waste of time,
I consider changing real uid as the greatest security hole.

When I decided that eliminated almost all of them I put
'printk' into kernel setreuid to catch remaining programs using it. And...
I was discouraged when discovered that seteuid in Linux == setreuid(-1,..).
I was sure that it MUST be separate syscall, because it MUST not
change saved uids.

Those crazy examples just demonstrate that Linux functions
are broken and they must be changed.

I already did it by replacing pretty useless setfs.ids with correct were bad idea (the greatest fault is that is write only and
it is impossible to save/restore it) and my nfsd does not use
in any case.

My "security system" developed under Linux and for Linux
works at any unix flavor that I have around except for Linux. It's funny,
is not it?

Alexey Kuznetsov.

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