From: joeyli <jlee@suse.com>
To: Matt Fleming <matt@codeblueprint.co.uk>
Cc: "Lee, Chun-Yi" <joeyli.kernel@gmail.com>,
linux-kernel@vger.kernel.org, linux-efi@vger.kernel.org,
linux-pm@vger.kernel.org, "Rafael J. Wysocki" <rjw@rjwysocki.net>,
Matthew Garrett <matthew.garrett@nebula.com>,
Len Brown <len.brown@intel.com>, Pavel Machek <pavel@ucw.cz>,
Josh Boyer <jwboyer@redhat.com>, Vojtech Pavlik <vojtech@suse.cz>,
Matt Fleming <matt.fleming@intel.com>,
Jiri Kosina <jkosina@suse.cz>, "H. Peter Anvin" <hpa@zytor.com>,
Ingo Molnar <mingo@redhat.com>
Subject: Re: [PATCH v2 05/16] x86/efi: Get entropy through EFI random number generator protocol
Date: Thu, 27 Aug 2015 14:17:50 +0800 [thread overview]
Message-ID: <20150827061750.GE24088@linux-rxt1.site> (raw)
In-Reply-To: <20150820202620.GF2567@codeblueprint.co.uk>
On Thu, Aug 20, 2015 at 09:26:20PM +0100, Matt Fleming wrote:
> On Tue, 11 Aug, at 02:16:25PM, Lee, Chun-Yi wrote:
> > +
> > +static unsigned long efi_get_rng64(efi_system_table_t *sys_table,
> > + void **rng_handle)
> > +{
> > + const struct efi_config *efi_early = __efi_early();
> > + efi_rng_protocol_64 *rng = NULL;
> > + efi_guid_t rng_proto = EFI_RNG_PROTOCOL_GUID;
> > + u64 *handles = (u64 *)(unsigned long)rng_handle;
> > + efi_status_t status;
> > + unsigned long rng_number;
> > +
> > + status = efi_call_early(handle_protocol, handles[0],
> > + &rng_proto, (void **)&rng);
> > + if (status != EFI_SUCCESS)
> > + efi_printk(sys_table, "Failed to get EFI_RNG_PROTOCOL handles\n");
> > +
> > + if (status == EFI_SUCCESS && rng) {
> > + status = efi_early->call((unsigned long)rng->get_rng, rng, NULL,
> > + sizeof(rng_number), &rng_number);
>
> Actually, one thing just occurred to me - you're not passing an
> RNGAlgorithm value and are relying upon the firmware's default
> implementation.
>
> I don't think that's a safe bet, the default could be anything and
> might vary across implementations.
>
I didn't set specific RNGAlgorithm because different BIOS may
set different algorithm as default, it's also a kind of random situation
to provide uncertainty.
On the other hand, if the specific RNGAlgorithm doesn't support by BIOS
then EFI stub still need use BIOS's _default_ algorithm to get random
value.
> Can we do a little better here and pick a "preferred" algorithm
> instead of the default?
>
> --
> Matt Fleming, Intel Open Source Technology Center
Per EDK2 implementation, EFI_RNG_ALGORITHM_SP800_90_CTR_256 is the default
algorithm that provided by driver, and EFI_RNG_ALGORITHM_RAW is the second
algorithm supported by EDK2. BIOS vendor need to write driver to support
others.
Maybe using EFI_RNG_ALGORITHM_SP800_90_CTR_256 as the default RNGAlgorithm
in efi_random can cover the most widely UEFI implementation, but when BIOS
do not support EFI_RNG_ALGORITHM_SP800_90_CTR_256 then kernel still need
use BIOS's _default_ setting.
I hope your suggestion.
Thanks a lot!
Joey Lee
next prev parent reply other threads:[~2015-08-27 6:18 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-08-11 6:16 [PATCH v2 00/16] Signature verification of hibernate snapshot Lee, Chun-Yi
2015-08-11 6:16 ` [PATCH v2 01/16] PM / hibernate: define HMAC algorithm and digest size of hibernation Lee, Chun-Yi
2015-08-11 6:16 ` [PATCH v2 02/16] x86/efi: Add get and set variable to EFI services pointer table Lee, Chun-Yi
2015-08-19 16:35 ` Matt Fleming
2015-08-11 6:16 ` [PATCH v2 03/16] x86/boot: Public getting random boot function Lee, Chun-Yi
2015-08-11 6:16 ` [PATCH v2 04/16] x86/efi: Generating random number in EFI stub Lee, Chun-Yi
2015-08-20 14:12 ` Matt Fleming
2015-08-27 4:06 ` joeyli
2015-08-11 6:16 ` [PATCH v2 05/16] x86/efi: Get entropy through EFI random number generator protocol Lee, Chun-Yi
2015-08-20 14:47 ` Matt Fleming
2015-08-27 4:51 ` joeyli
2015-08-20 20:26 ` Matt Fleming
2015-08-27 6:17 ` joeyli [this message]
2015-08-11 6:16 ` [PATCH v2 06/16] x86/efi: Generating random HMAC key for siging hibernate image Lee, Chun-Yi
2015-08-20 20:40 ` Matt Fleming
2015-08-27 9:04 ` joeyli
2015-09-09 12:15 ` Matt Fleming
2015-09-13 2:47 ` joeyli
2015-08-11 6:16 ` [PATCH v2 07/16] efi: Make efi_status_to_err() public Lee, Chun-Yi
2015-08-20 15:07 ` Matt Fleming
2015-08-27 9:06 ` joeyli
2015-08-11 6:16 ` [PATCH v2 08/16] x86/efi: Carrying hibernation key by setup data Lee, Chun-Yi
2015-08-15 17:07 ` Pavel Machek
2015-08-16 5:28 ` joeyli
2015-08-16 21:23 ` Jiri Kosina
2015-08-17 6:54 ` Nigel Cunningham
2015-08-21 12:40 ` Matt Fleming
2015-08-27 9:28 ` joeyli
2015-08-11 6:16 ` [PATCH v2 09/16] PM / hibernate: Reserve hibernation key and erase footprints Lee, Chun-Yi
2015-08-13 2:45 ` Chen, Yu C
2015-08-13 3:25 ` joeyli
2015-08-13 14:33 ` joeyli
2015-08-21 13:27 ` Matt Fleming
2015-08-27 10:21 ` joeyli
2015-09-09 12:24 ` Matt Fleming
2015-09-13 2:58 ` joeyli
2015-08-11 6:16 ` [PATCH v2 10/16] PM / hibernate: Generate and verify signature of hibernate snapshot Lee, Chun-Yi
2015-08-11 6:16 ` [PATCH v2 11/16] PM / hibernate: Avoid including hibernation key to hibernate image Lee, Chun-Yi
2015-08-11 6:16 ` [PATCH v2 12/16] PM / hibernate: Forward signature verifying result and key to image kernel Lee, Chun-Yi
2015-08-11 6:16 ` [PATCH v2 13/16] PM / hibernate: Add configuration to enforce signature verification Lee, Chun-Yi
2015-08-11 6:16 ` [PATCH v2 14/16] PM / hibernate: Allow user trigger hibernation key re-generating Lee, Chun-Yi
2015-08-11 6:16 ` [PATCH v2 15/16] PM / hibernate: Bypass verification logic on legacy BIOS Lee, Chun-Yi
2015-08-11 6:16 ` [PATCH v2 16/16] PM / hibernate: Document signature verification of hibernate snapshot Lee, Chun-Yi
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