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SubjectRe: Unexecutable stack
>There is a case that can be made for the code-segment ".text" to be
>non-writable. It prevents a hardware glitch from modifying code. There
>is also a case that can be make for making this segment non-readable
>because it can become a covert communications channel. However,
>it is very unlikely that either would enhance the security of any
>system you are likely to encounter in a lifetime.

Depends on both license restrictions and export restrictions....

If the licence says "execute-only" then I believe you can get into trouble
if the binary is copied, decoded, and recoded into another program. If it
is traced back to your system, then a trade-secret violation can be presented.

Copying can be accomplished by a stack overflow bug; which I would think that
some of the responsibility can be put back on the vendor for including a bug.

I like the option of make the stack non-executable because:
1. it allows the detection of bugs (stack overflow) in third-party software
where I have no control over wether the bug can be fixed.
2. It does prevent some breaches generated by (1).

trap handling doesn't have to be done by requiring executable stack. That
just happens to be an implementation detail. I have seen it done via
stack frames, and being able to unwind the stack.
-------------------------------------------------------------------------
Jesse I Pollard, II
Email: pollard@navo.hpc.mil

Any opinions expressed are solely my own.

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