[U-Boot] Does U-boot support ASLR?

[Mike Frysinger]

On Thursday 09 February 2012 14:28:07 Scott Wood wrote:
> On 02/09/2012 12:58 PM, Mike Frysinger wrote:
> > On Thursday 09 February 2012 13:37:15 Jason Markley wrote:
> >> I agree any proposal would need to be accompanied by good reasoning.
> >> I'm honestly a little confused as to why a generally accepted security
> >> feature such as ASLR would NOT be useful for u-boot.  U-boot has the
> >> capability to interact with the outside world via the network as well as
> >> the console.  When using the U-boot API, it also remains resident in
> >> memory.  Wouldn't something like ASLR enhance the security posture of
> >> U-boot in those situations?
> > 
> > u-boot is running in supervisor mode / ring 0 / etc...  you have full
> > access to the hardware with a simple `mw` command.  randomizing the
> > address base of u-boot doesn't gain you anything.  so no, i see no
> > advantage of u-boot itself utilizing ASLR regardless of what it
> > interacts with.
> 
> This assumes that the full command line interface is enabled, and is the
> mechanism of interaction in question.  It doesn't apply to interactions
> over the network, special serial protocols, etc.

network/serial loads do no file length checks.  `tftpload 0` will write until 
the server stops sending.  not to mention there is no secure communication 
between u-boot and the server.

> > ignoring this, there are two fundamental issues with ASLR:
> >  - this early on, u-boot has very little (if no) entropy, so any attempts
> >  to
> > 
> > generate random numbers are going to be fairly predictable
> 
> This doesn't apply if there's a hardware random number generator -- and
> even poor entropy is more effort to guess than a fixed address.

not when you know the starting point and can brute force it through

> It probably doesn't make sense as default behavior, but I could see it
> being useful in some situations.

such as ?
-mike
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