On Thu, Feb 21, 2008 at 12:10 PM, Paul Millar <[EMAIL PROTECTED]> wrote:
> Apparently, the problem here is DRAM doesn't fade fast enough. If the reboot > is fast, then the memory contents are preserved, so exposing the in-memory > cache of the disk encryption key. Boot off a memory stick and one can > analysis the memory's content. yes, this is a problem and has been for as long as DRAM has been around. I kept wondering if anyone would notice :-) I used to debug DRAM-based micros by power cycling them and then dumping DRAM. Most of it survived. I won't even mention how long ago this was. > > The (perhaps flippant ;-) remark from "bootman" about storing the keys > somewhere where the data will be erased by the BIOS led me to wonder if > coreboot could do something like this. yes, very easily. > > Perhaps coreboot could add the option of wipe the memory contents before > handing over to the payload, maybe a "wipe-memory" payload that fails over to > the next, main payload? We could do it in initram with no trouble. You pretty much have to do a full memory write to reset the ECC tags anyway (note: NOT zero. Just write). I'm kind of opposed to zeroing memory, since frequently, you want the contents of memory for port-mortem. That said, I'm surprised their attack worked since I assumed all those wonderful "secure" BIOSes -- such as EFI -- would zero all of memory. There must be something else going on here. Oh, there is -- they turned off memory wipe. I'm not that astonished, I'm surprised that anyone is ... DRAM retention is a widely known issue. >If erasing the whole memory would take too long, > could it wipe some part of the memory and (by convention) that part of the > memory be used for storing secrets? HMM, the K8 has 3.2 GB/sec memory bw at minimum. Put 128 GB on a single CPU ->40 seconds. People might get upset. But people who care about security should not. It's funny. Those incredibly slow BIOSes disable a very important security item to get faster boot :-) > > Neither offers a completely solution to the problem: apparently, as the > temperature is lowered, the data in DRAM will survive longer---at liquid > Nitrogen temperatures it can last for hours---but perhaps it could help. The problem is easily solved -- on some machines, it should not be possible to disable (at minimum) a full zero'ing of memory. Neat paper though. It makes a widely known but not much discussed problem more widely known. ron -- coreboot mailing list [email protected] http://www.coreboot.org/mailman/listinfo/coreboot
