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Fortunately microcode updates are not persistent and need to be applied on every boot.
by Boulth 8y ago
Fortunately microcode updates are not persistent and need to be applied on every boot.
- jacquesm 8y agoI think that's 'unfortunately', and I think that such updates should require the movement of a switch or jumper to be activated. Obviously the 'hands off' and 'lights out' trends in the datacenter make such a requirement a non-starter but from a security perspective it would make good sense.
- monocasa 8y agoI think it's good. There's not much space in the microcode patch RAM, so hiding a malicious update like you would a root kit would be extremely difficult.
- ddingus 8y agoA stealth privilege escalation would be far more likely. Find a redundant, or unused bit, and...
- ddingus 8y agoIt's too late to edit, but that's exactly what I would go for.
- anyfoo 8y ago"There's probably not enough space for a meaningful exploit" is never a strategy that pans out. Hardcoded signature validation can go a long way, but of course it really needs to be bulletproof, and also take e.g. downgrade protection into consideration. An added physical switch, while more secure, is (as the previous commenter mentioned) so impractical, that it will more likely lead to less updating of vulnerable microcode.
- Timmah 8y agoOne reason they do this is so bad fw can't brick an expensive CPU
- joshumax 8y agoAdditionally, modern microcode updates are both encrypted and signed blobs. Granted, it's of little use if Intel/AMD are playing the role of bad actor or if the signing and decryption mechanisms are bypassed somehow; but trying to load unsigned microcode by default will result in rejection.
- jcranmer 8y agoIt's worth noting that the analysis is on old AMD microcode precisely because AMD didn't use signed microcode for a long time and so they could create custom microcode to reverse engineer what it's doing.
- RachelF 8y agoUpdates can be stored in the BIOS flash, so if you can program this you could theoretically update the microcode. The OS can also patch the microcode during boot. The signature/encryption is still a problem, which might be why they are using older AMD K8 and K10 processors from 2007 which didn't have this security. Still, if the keys do leak out of AMD or Intel, this is a huge security hole.
- ryanlol 8y agoWhat does “security hole” mean to you?