Security Flaw in Popular Disk Encryption Technologies

[Tim Clewlow]

--- Pieter de Boer <pieter at thedarkside.nl> wrote:

> Jeremy Chadwick wrote:
> 
> > It's interesting that you classified this as a "feature" (in quotes),
> > because there's nothing "modern" about said "feature".  This issue has
> > existed since the beginning of RAM chip engineering; I can even confirm
> > this "feature" exists on old video game consoles such as the Nintendo
> > and Super Nintendo (where there were strict guidelines put in place by
> > Nintendo, requiring developers to initialise certain areas of memory
> > and certain memory-mapped I/O registers during hard or soft resets).
> I shouldnt've used the word 'modern', then.
> 
> > Proper software should be memset() or bzero()'ing memory space it
> > mallocs.  I've gotten in the habit of doing this for years, purely as a
> > safety net.  If said software doesn't do this, it's very likely
> > succeptable.
> That is not relevant to the issue. The issue is that the keys are in 
> memory when the encrypted filesystem is in use. The keys can be read by 
> pulling and reinserting the power plug and restarting into a tool that 
> can dump memory (or by placing the memory modules in another system). 
> The keys to encrypted volumes can be found in this dump, leading to a 
> compromise of the data.

Many BIOS have fast and slow boot options - they are usually set to fast by
default. The slow boot option often checks RAM and effectively wipes RAM in the
process. If the BIOS is password protected then the only way to break in is to
reset the BIOS by removing the BIOS battery. Given that RAM degrades over a
short period of no power, and that arranging to physically pull the BIOS
battery most likely exceeds that time limit, then this would effectively be one
solution. Although it will mean always booting the slow way.

Tim.


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