Received-SPF: pass (google.com: domain of linux-crypto+bounces-4229-linux.lists.archive=gmail.com@vger.kernel.org designates 2604:1380:4601:e00::3 as permitted sender) client-ip=2604:1380:4601:e00::3;
Message-ID: <66ec985f3ee229135bf748f1b0874d5367a74d7f.camel@HansenPartnership.com>
Subject: Re: [PATCH v8 18/22] tpm: add session encryption protection to
 tpm2_get_random()
From: James Bottomley <James.Bottomley@HansenPartnership.com>
To: Ard Biesheuvel <ardb@kernel.org>
Cc: Linux Crypto Mailing List <linux-crypto@vger.kernel.org>, Herbert Xu
 <herbert@gondor.apana.org.au>, =?ISO-8859-1?Q?N=EDcolas?= "F. R. A. Prado"
 <nfraprado@collabora.com>, linux-integrity@vger.kernel.org, Jarkko Sakkinen
 <jarkko@kernel.org>, keyrings@vger.kernel.org, regressions@lists.linux.dev,
  kernel@collabora.com
Date: Fri, 17 May 2024 07:25:40 -0700
In-Reply-To: <CAMj1kXFE_R_x10BVkU+8vrMz0RHiX0+rz-ZL+w08FH2CLQHZXA@mail.gmail.com>
References: <20240429202811.13643-1-James.Bottomley@HansenPartnership.com>
	 <20240429202811.13643-19-James.Bottomley@HansenPartnership.com>
	 <119dc5ed-f159-41be-9dda-1a056f29888d@notapiano>
	 <0f68c283ff4bbb89b8a019d47891f798c6fff287.camel@HansenPartnership.com>
	 <CAMj1kXHi4r8KY9GvX573kwqvLpMfX-J=K2hWiGAKkf5bnicwYQ@mail.gmail.com>
	 <0d260c2f7a9f67ec8bd2305919636678d06000d1.camel@HansenPartnership.com>
	 <CAMj1kXFE_R_x10BVkU+8vrMz0RHiX0+rz-ZL+w08FH2CLQHZXA@mail.gmail.com>
Content-Type: text/plain; charset="UTF-8"
User-Agent: Evolution 3.42.4 
Precedence: bulk
MIME-Version: 1.0
Content-Transfer-Encoding: 8bit

On Fri, 2024-05-17 at 15:43 +0200, Ard Biesheuvel wrote:
> On Fri, 17 May 2024 at 15:35, James Bottomley
> <James.Bottomley@hansenpartnership.com> wrote:
[...]
> > Thanks for the analysis.  If I look at how CRYPTO_ECC does it, that
> > selects CRYPTO_RNG_DEFAULT which pulls in CRYPTO_DRBG, so the fix
> > would be the attached.  Does that look right to you Ard?
> 
> No it doesn't - it's CRYPTO_RNG_DEFAULT not CRYTPO_RNG_DEFAULT :-)
> 
> With that fixed,
> 
> Acked-by: Ard Biesheuvel <ardb@kernel.org>

Erm, oops, sorry about that; so attached is the update.

James

---8>8>8><8<8<8---

From 2ac337a33e6416ef806e2c692b9239d193e8468f Mon Sep 17 00:00:00 2001
From: James Bottomley <James.Bottomley@HansenPartnership.com>
Date: Fri, 17 May 2024 06:29:31 -0700
Subject: [PATCH] tpm: Fix sessions cryptography requirement for Random Numbers
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

The ECDH code in tpm2-sessions.c requires an initial random number
generator to generate the key pair.  If the configuration doesn't have
CONFIG_RNG_DEFAULT, it will try to pull this in as a module (which is
impossible for the early kernel boot where the TPM starts).  Fix this
by selecting the required RNG.

Reported-by: Nícolas F. R. A. Prado <nfraprado@collabora.com>
Fixes: 1b6d7f9eb150 ("tpm: add session encryption protection to tpm2_get_random()")
Acked-by: Ard Biesheuvel <ardb@kernel.org>
Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com>
---
 drivers/char/tpm/Kconfig | 1 +
 1 file changed, 1 insertion(+)

diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig
index 4f83ee7021d0..ecdd3db4be2b 100644
--- a/drivers/char/tpm/Kconfig
+++ b/drivers/char/tpm/Kconfig
@@ -31,6 +31,7 @@ config TCG_TPM2_HMAC
 	bool "Use HMAC and encrypted transactions on the TPM bus"
 	default y
 	select CRYPTO_ECDH
+	select CRYPTO_RNG_DEFAULT
 	select CRYPTO_LIB_AESCFB
 	select CRYPTO_LIB_SHA256
 	help
-- 
2.35.3