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Date: Tue, 10 Aug 2021 10:54:46 +0530 From: Sumit Garg <sumit.garg@...aro.org> To: Jarkko Sakkinen <jarkko@...nel.org> Cc: Ahmad Fatoum <a.fatoum@...gutronix.de>, James Bottomley <jejb@...ux.ibm.com>, Mimi Zohar <zohar@...ux.ibm.com>, David Howells <dhowells@...hat.com>, kernel <kernel@...gutronix.de>, James Morris <jmorris@...ei.org>, "Serge E. Hallyn" <serge@...lyn.com>, Horia Geantă <horia.geanta@....com>, Aymen Sghaier <aymen.sghaier@....com>, Herbert Xu <herbert@...dor.apana.org.au>, "David S. Miller" <davem@...emloft.net>, Udit Agarwal <udit.agarwal@....com>, Eric Biggers <ebiggers@...nel.org>, Jan Luebbe <j.luebbe@...gutronix.de>, David Gstir <david@...ma-star.at>, Richard Weinberger <richard@....at>, Franck LENORMAND <franck.lenormand@....com>, "open list:ASYMMETRIC KEYS" <keyrings@...r.kernel.org>, "open list:HARDWARE RANDOM NUMBER GENERATOR CORE" <linux-crypto@...r.kernel.org>, linux-integrity <linux-integrity@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, "open list:SECURITY SUBSYSTEM" <linux-security-module@...r.kernel.org> Subject: Re: [PATCH 2/4] KEYS: trusted: allow trust sources to use kernel RNG for key material On Mon, 9 Aug 2021 at 15:26, Jarkko Sakkinen <jarkko@...nel.org> wrote: > > On Mon, Aug 09, 2021 at 09:52:20AM +0200, Ahmad Fatoum wrote: > > Hello Sumit, > > > > On 22.07.21 08:31, Sumit Garg wrote: > > > On Wed, 21 Jul 2021 at 22:19, Ahmad Fatoum <a.fatoum@...gutronix.de> wrote: > > >> > > >> The two existing trusted key sources don't make use of the kernel RNG, > > >> but instead let the hardware that does the sealing/unsealing also > > >> generate the random key material. While a previous change offers users > > >> the choice to use the kernel RNG instead for both, new trust sources > > >> may want to unconditionally use the kernel RNG for generating key > > >> material, like it's done elsewhere in the kernel. > > >> > > >> This is especially prudent for hardware that has proven-in-production > > >> HWRNG drivers implemented, as otherwise code would have to be duplicated > > >> only to arrive at a possibly worse result. > > >> > > >> Make this possible by turning struct trusted_key_ops::get_random > > >> into an optional member. If a driver leaves it NULL, kernel RNG > > >> will be used instead. > > >> > > >> Signed-off-by: Ahmad Fatoum <a.fatoum@...gutronix.de> > > >> --- > > >> To: James Bottomley <jejb@...ux.ibm.com> > > >> To: Jarkko Sakkinen <jarkko@...nel.org> > > >> To: Mimi Zohar <zohar@...ux.ibm.com> > > >> To: David Howells <dhowells@...hat.com> > > >> Cc: James Morris <jmorris@...ei.org> > > >> Cc: "Serge E. Hallyn" <serge@...lyn.com> > > >> Cc: "Horia Geantă" <horia.geanta@....com> > > >> Cc: Aymen Sghaier <aymen.sghaier@....com> > > >> Cc: Herbert Xu <herbert@...dor.apana.org.au> > > >> Cc: "David S. Miller" <davem@...emloft.net> > > >> Cc: Udit Agarwal <udit.agarwal@....com> > > >> Cc: Eric Biggers <ebiggers@...nel.org> > > >> Cc: Jan Luebbe <j.luebbe@...gutronix.de> > > >> Cc: David Gstir <david@...ma-star.at> > > >> Cc: Richard Weinberger <richard@....at> > > >> Cc: Franck LENORMAND <franck.lenormand@....com> > > >> Cc: Sumit Garg <sumit.garg@...aro.org> > > >> Cc: keyrings@...r.kernel.org > > >> Cc: linux-crypto@...r.kernel.org > > >> Cc: linux-integrity@...r.kernel.org > > >> Cc: linux-kernel@...r.kernel.org > > >> Cc: linux-security-module@...r.kernel.org > > >> --- > > >> include/keys/trusted-type.h | 2 +- > > >> security/keys/trusted-keys/trusted_core.c | 2 +- > > >> 2 files changed, 2 insertions(+), 2 deletions(-) > > >> > > >> diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h > > >> index d89fa2579ac0..4eb64548a74f 100644 > > >> --- a/include/keys/trusted-type.h > > >> +++ b/include/keys/trusted-type.h > > >> @@ -64,7 +64,7 @@ struct trusted_key_ops { > > >> /* Unseal a key. */ > > >> int (*unseal)(struct trusted_key_payload *p, char *datablob); > > >> > > >> - /* Get a randomized key. */ > > >> + /* Optional: Get a randomized key. */ > > >> int (*get_random)(unsigned char *key, size_t key_len); > > >> > > >> /* Exit key interface. */ > > >> diff --git a/security/keys/trusted-keys/trusted_core.c b/security/keys/trusted-keys/trusted_core.c > > >> index 569af9af8df0..d2b7626cde8b 100644 > > >> --- a/security/keys/trusted-keys/trusted_core.c > > >> +++ b/security/keys/trusted-keys/trusted_core.c > > >> @@ -334,7 +334,7 @@ static int __init init_trusted(void) > > >> continue; > > >> > > >> get_random = trusted_key_sources[i].ops->get_random; > > >> - if (trusted_kernel_rng) > > >> + if (trusted_kernel_rng || !get_random) > > >> get_random = kernel_get_random; > > >> > > > > > > For ease of understanding, I would prefer to write it as: > > > > > > get_random = trusted_key_sources[i].ops->get_random ?: > > > kernel_get_random; > > > if (trusted_kernel_rng) > > > get_random = kernel_get_random; > > > > > > With that: > > > > > > Acked-by: Sumit Garg <sumit.garg@...aro.org> > > > > I don't think it improves readability to split up the conditional. > > At least I need to take a second pass over the code to understand > > the second conditional. > > Ternary operators are pain to read, unless a super trivial case. > > I'd stick to what you did. Fair enough, I am fine with the current patch. -Sumit > > /Jarkko
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