Messages in this thread | ![/](/images/icornerl.gif) | | Date | Thu, 29 Aug 2019 11:45:05 -0400 | From | "Theodore Y. Ts'o" <> | Subject | Re: [PATCH v9 2/3] fdt: add support for rng-seed |
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On Thu, Aug 29, 2019 at 06:03:57PM +0800, Hsin-Yi Wang wrote: > On Thu, Aug 29, 2019 at 1:36 AM Kees Cook <keescook@chromium.org> wrote: > > > > Can this please be a boot param (with the default controlled by the > > CONFIG)? See how CONFIG_RANDOM_TRUST_CPU is wired up... > > > > Currently rng-seed read and added in setup_arch() --> > setup_machine_fdt().. -> early_init_dt_scan_chosen(), which is earlier > than parse_early_param() that initializes early_param. > > If we want to set it as a boot param, add_bootloader_randomness() can > only be called after parse_early_param(). The seed can't be directly > added to pool after it's read in. We need to store into global > variable and load it later. > If this seems okay then I'll add a patch for this. Thanks
I thought about asking for this, but we really want to do this as early as possible, so that it can be used by KASLR and other services that are run super early. Also, whether or not we can trust the bootloader is going to be a system-level thing. This should probably be defaulted to off, and only enabled by the system integrator if they are 100%, positively sure, that the entire system is one where we can trust the source of randomness which the bootloader is using --- or for that matter, that the bootloader is trustworthy!
Is it really going to be that useful for a random system administrator to be able to flip this on or off from the command line? Hopefully there will be an easy way to configure the firmware or the bootloader to simply not supply entropy, if for some reason it's not trustworthy.
- Ted
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