於 四，2013-08-29 於 23:32 +0200，Pavel Machek 提到： > Hi! > > > > > - Bootloader store the public key to EFI boottime variable by itself > > > > - Bootloader put The private key to S4SignKey EFI variable for forward to > > > > kernel. > > > > > > Is the UEFI NVRAM really suited for such regular updates? > > > > > > > Yes, Matthew raised this concern at before. I modified patch to load > > private key in efi stub kernel, before ExitBootServices(), that means we > > don't need generate key-pair at every system boot. So, the above > > procedure of efi bootloader will only run one time. > > > > User can enable SNAPSHOT_REGEN_KEYS kernel config to notify efi > > booloader regenerate key-pair for every S4 to improve security if he > > want. So, the key-pair re-generate procedure will only launched when S4 > > resume, not every system boot. > > How many writes can UEFI NVRAM survive? (Is it NOR?) Currently doesn't have enough information for normal. Yes, I don't know. > > "every S4 resume" may be approximately "every boot" for some users... > Pavel Yes, it's possible. So, this option will be disabled by default. Default will only generate one key-pair for every hibernate. If "re-generate key-pair for every S4" is still hurt lift of UEFI NVRAM too much, then another thinking for re-generate key-pair are: + Re-generate key-pair after a number of hibernates. e.g. after 5, 10, 20... times or + Random re-generate key-pair? On the other hand... In current design, GenS4Key EFI variable could be write by userland hibernate tool, kernel will respect GenS4Key value from userland when hibernate launch. So, userland can tell bootloader to lunch the key-pair regeneration procedure. Thanks a lot! Joey LEe -- To unsubscribe from this list: send the line "unsubscribe linux-crypto" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
