From patchwork Thu Feb 16 20:14:07 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: James Bottomley X-Patchwork-Id: 13143724 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id AC58CC61DA4 for ; Thu, 16 Feb 2023 20:19:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S229611AbjBPUTb (ORCPT ); Thu, 16 Feb 2023 15:19:31 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38410 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229558AbjBPUTa (ORCPT ); Thu, 16 Feb 2023 15:19:30 -0500 Received: from bedivere.hansenpartnership.com (bedivere.hansenpartnership.com [IPv6:2607:fcd0:100:8a00::2]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 25FD416327; Thu, 16 Feb 2023 12:19:30 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=hansenpartnership.com; s=20151216; t=1676578769; bh=SE6HKh3MzOkV6VQ+sdsgr/jtH0PlyVA2D5a/H+vb7Jc=; h=From:To:Subject:Date:Message-Id:In-Reply-To:References:From; b=djbSDEkHw3jg6DAt2CNdahbb7xFCrvtTp0lNaDPKH+R581HPZSLaL5G9Bjl19D/H6 WLXPAohCLN8singYZdWnAXjXiXk15FuDfh9MGBxHEcfx1AomxcWq75I0hZNfKKRJtX i3905J2xhWgEjKQS+/UE3dSkZVL1LqhT2zEcX5AM= Received: from localhost (localhost [127.0.0.1]) by bedivere.hansenpartnership.com (Postfix) with ESMTP id EBE4C1286F45; Thu, 16 Feb 2023 15:19:29 -0500 (EST) Received: from bedivere.hansenpartnership.com ([127.0.0.1]) by localhost (bedivere.hansenpartnership.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id jHep8-Cu4kMR; Thu, 16 Feb 2023 15:19:29 -0500 (EST) Received: from lingrow.int.hansenpartnership.com (unknown [153.66.160.227]) by bedivere.hansenpartnership.com (Postfix) with ESMTP id 6CB031286629; Thu, 16 Feb 2023 15:19:29 -0500 (EST) From: James Bottomley To: linux-integrity@vger.kernel.org Cc: Jarkko Sakkinen , keyrings@vger.kernel.org, Ard Biesheuvel Subject: [PATCH 09/12] tpm: add session encryption protection to tpm2_get_random() Date: Thu, 16 Feb 2023 15:14:07 -0500 Message-Id: <20230216201410.15010-10-James.Bottomley@HansenPartnership.com> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20230216201410.15010-1-James.Bottomley@HansenPartnership.com> References: <20230216201410.15010-1-James.Bottomley@HansenPartnership.com> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: keyrings@vger.kernel.org If some entity is snooping the TPM bus, they can see the random numbers we're extracting from the TPM and do prediction attacks against their consumers. Foil this attack by using response encryption to prevent the attacker from seeing the random sequence. Signed-off-by: James Bottomley --- drivers/char/tpm/tpm2-cmd.c | 20 ++++++++++++++++---- 1 file changed, 16 insertions(+), 4 deletions(-) diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c index ef038cc71f9c..dc0070922d38 100644 --- a/drivers/char/tpm/tpm2-cmd.c +++ b/drivers/char/tpm/tpm2-cmd.c @@ -292,25 +292,35 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max) if (!num_bytes || max > TPM_MAX_RNG_DATA) return -EINVAL; - err = tpm_buf_init(&buf, 0, 0); + err = tpm2_start_auth_session(chip); if (err) return err; + err = tpm_buf_init(&buf, 0, 0); + if (err) { + tpm2_end_auth_session(chip); + return err; + } + do { - tpm_buf_reset(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_GET_RANDOM); + tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_GET_RANDOM); + tpm_buf_append_hmac_session_opt(chip, &buf, TPM2_SA_ENCRYPT + | TPM2_SA_CONTINUE_SESSION, + NULL, 0); tpm_buf_append_u16(&buf, num_bytes); + tpm_buf_fill_hmac_session(chip, &buf); err = tpm_transmit_cmd(chip, &buf, offsetof(struct tpm2_get_random_out, buffer), "attempting get random"); + err = tpm_buf_check_hmac_response(chip, &buf, err); if (err) { if (err > 0) err = -EIO; goto out; } - out = (struct tpm2_get_random_out *) - &buf.data[TPM_HEADER_SIZE]; + out = (struct tpm2_get_random_out *)tpm_buf_parameters(&buf); recd = min_t(u32, be16_to_cpu(out->size), num_bytes); if (tpm_buf_length(&buf) < TPM_HEADER_SIZE + @@ -327,6 +337,8 @@ int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max) } while (retries-- && total < max); tpm_buf_destroy(&buf); + tpm2_end_auth_session(chip); + return total ? total : -EIO; out: tpm_buf_destroy(&buf);