From patchwork Wed May 4 23:21:01 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Evan Green X-Patchwork-Id: 12838904 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 3A20AC43217 for ; Wed, 4 May 2022 23:59:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1359450AbiEEABb (ORCPT ); Wed, 4 May 2022 20:01:31 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:42220 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1385492AbiEDXZ0 (ORCPT ); Wed, 4 May 2022 19:25:26 -0400 Received: from mail-pl1-x62e.google.com (mail-pl1-x62e.google.com [IPv6:2607:f8b0:4864:20::62e]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 37E744EA0B for ; Wed, 4 May 2022 16:21:49 -0700 (PDT) Received: by mail-pl1-x62e.google.com with SMTP id x18so2823786plg.6 for ; Wed, 04 May 2022 16:21:49 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=T0Ha5PjFrQlu4myFqDfG5tFx9BSiu6/SZECZT4sF2bI=; b=lygx6dOsIFOk6hF+4C4Y8LRBekgsVCS6E/2MWFWQDMqc5bqCTYepfliMJM1myFV70X jLFK02Fm2WKNyG22x0nZg+TsW5CsKzRyxkbYqV5+/PZ+gd4MpqDNr7coCd5Kt+2BDZNd ONxJuOjN2+D6qeZ3Xquf1Dcw1BHsLe77ypccU= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=T0Ha5PjFrQlu4myFqDfG5tFx9BSiu6/SZECZT4sF2bI=; b=N34Z04rYKmbVIQyWUVEYKEVEitV8WYINrUmOE17Qn0ezLjDX8Kwomu5wmQKRmZWUEl AspxRNNniUzpGzTLF9QiH7ypHbRqA8XouZg0ThudYQAITRAANrJQcvlbGCU9DeF+pL+P aq9ENDXFB9ZynR/6tpGzIHDyCHuHqTSpsKDHiqe21oE//SxMmBbqENsNIe7Ywg+m2Yli oiPEm8Ytpzsna54TUx6AIq1nK6fCCMprPY1JShnwkNLFs6LLOYj3JmxpWDHju4v7/iM/ /hJXBmd7vRX7twOwd8YWVv7qlgnjv4ceZ5JwuB+Ny5OdpD3ijXIo+vIKV9Uafi4TGj35 g4pw== X-Gm-Message-State: AOAM532lsJ0d5gZw+hgrgfCNRgOvyTkGvDOc/2SntqqS0oJ8e6/NYcOn ve/JKJM4HDJVkTaYF5+BKUFZRQ== X-Google-Smtp-Source: ABdhPJwTek7lbCixRIDyD0usxwvu26W1HK2YAo0odHiNuXLR54TGcMPEtMfBRJ0xUOtP1S0Xrla3iw== X-Received: by 2002:a17:903:22c9:b0:15e:a8a0:2a79 with SMTP id y9-20020a17090322c900b0015ea8a02a79mr16125068plg.31.1651706508866; Wed, 04 May 2022 16:21:48 -0700 (PDT) Received: from evgreen-glaptop.lan ([98.47.98.87]) by smtp.gmail.com with ESMTPSA id q12-20020a170902f78c00b0015e8d4eb2d6sm1901pln.288.2022.05.04.16.21.47 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 04 May 2022 16:21:48 -0700 (PDT) From: Evan Green To: linux-kernel@vger.kernel.org Cc: Matthew Garrett , dlunev@google.com, zohar@linux.ibm.com, jejb@linux.ibm.com, linux-integrity@vger.kernel.org, corbet@lwn.net, rjw@rjwysocki.net, gwendal@chromium.org, jarkko@kernel.org, linux-pm@vger.kernel.org, Evan Green , Len Brown , Pavel Machek , "Rafael J. Wysocki" Subject: [PATCH 09/10] PM: hibernate: Verify the digest encryption key Date: Wed, 4 May 2022 16:21:01 -0700 Message-Id: <20220504161439.9.I504d456c7a94ef1aaa7a2c63775ce9690c3ad7ab@changeid> X-Mailer: git-send-email 2.31.0 In-Reply-To: <20220504232102.469959-1-evgreen@chromium.org> References: <20220504232102.469959-1-evgreen@chromium.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-integrity@vger.kernel.org We want to ensure that the key used to encrypt the digest was created by the kernel during hibernation. To do this we request that the TPM include information about the value of PCR 23 at the time of key creation in the sealed blob. On resume, we can make sure that the PCR information in the creation data blob (already certified by the TPM to be accurate) corresponds to the expected value. Since only the kernel can touch PCR 23, if an attacker generates a key themselves the value of PCR 23 will have been different, allowing us to reject the key and boot normally instead of resuming. Sourced-from: Matthew Garrett Signed-off-by: Evan Green --- Matthew's original version of this patch is here: https://patchwork.kernel.org/project/linux-pm/patch/20210220013255.1083202-9-matthewgarrett@google.com/ I moved the TPM2_CC_CERTIFYCREATION code into a separate change in the trusted key code because the blob_handle was being flushed and was no longer valid for use in CC_CERTIFYCREATION after the key was loaded. As an added benefit of moving the certification into the trusted keys code, we can drop the other patch from the original series that squirrelled the blob_handle away. kernel/power/snapenc.c | 96 +++++++++++++++++++++++++++++++++++++++++- 1 file changed, 94 insertions(+), 2 deletions(-) diff --git a/kernel/power/snapenc.c b/kernel/power/snapenc.c index 067f49c05a4d54..38bc820f780d8b 100644 --- a/kernel/power/snapenc.c +++ b/kernel/power/snapenc.c @@ -23,6 +23,45 @@ static struct tpm_digest known_digest = { .alg_id = TPM_ALG_SHA256, 0xf1, 0x22, 0x38, 0x6c, 0x33, 0xb1, 0x14, 0xb7, 0xec, 0x05, 0x5f, 0x49}}; +/* sha256(sha256(empty_pcr | known_digest)) */ +static const char expected_digest[] = {0x2f, 0x96, 0xf2, 0x1b, 0x70, 0xa9, 0xe8, + 0x42, 0x25, 0x8e, 0x66, 0x07, 0xbe, 0xbc, 0xe3, 0x1f, 0x2c, 0x84, 0x4a, + 0x3f, 0x85, 0x17, 0x31, 0x47, 0x9a, 0xa5, 0x53, 0xbb, 0x23, 0x0c, 0x32, + 0xf3}; + +static int sha256_data(char *buf, int size, char *output) +{ + struct crypto_shash *tfm; + struct shash_desc *desc; + int ret; + + tfm = crypto_alloc_shash("sha256", 0, 0); + if (IS_ERR(tfm)) + return PTR_ERR(tfm); + + desc = kmalloc(sizeof(struct shash_desc) + + crypto_shash_descsize(tfm), GFP_KERNEL); + if (!desc) { + crypto_free_shash(tfm); + return -ENOMEM; + } + + desc->tfm = tfm; + ret = crypto_shash_init(desc); + if (ret != 0) { + crypto_free_shash(tfm); + kfree(desc); + return ret; + } + + crypto_shash_update(desc, buf, size); + crypto_shash_final(desc, output); + crypto_free_shash(desc->tfm); + kfree(desc); + + return 0; +} + /* Derive a key from the kernel and user keys for data encryption. */ static int snapshot_use_user_key(struct snapshot_data *data) { @@ -515,7 +554,7 @@ static int snapshot_create_kernel_key(struct snapshot_data *data) struct key *key; int ret, i; /* Create a key sealed by the SRK. */ - char *keyinfo = "new\t32\tkeyhandle=0x81000000"; + char *keyinfo = "new\t32\tkeyhandle=0x81000000\tcreationpcrs=0x00800000"; chip = tpm_default_chip(); if (!chip) @@ -628,6 +667,7 @@ static int snapshot_load_kernel_key(struct snapshot_data *data, struct uswsusp_key_blob *blob) { + char certhash[SHA256_DIGEST_SIZE]; const struct cred *cred = current_cred(); char *keytemplate = "load\t%s\tkeyhandle=0x81000000"; struct tpm_digest *digests = NULL; @@ -635,6 +675,7 @@ static int snapshot_load_kernel_key(struct snapshot_data *data, char *keyinfo = NULL; struct tpm_chip *chip; struct key *key; + struct trusted_key_payload *payload; int i, ret; chip = tpm_default_chip(); @@ -650,8 +691,10 @@ static int snapshot_load_kernel_key(struct snapshot_data *data, digests = kcalloc(chip->nr_allocated_banks, sizeof(struct tpm_digest), GFP_KERNEL); - if (!digests) + if (!digests) { + ret = -ENOMEM; goto reset; + } for (i = 0; i <= chip->nr_allocated_banks; i++) { digests[i].alg_id = chip->allocated_banks[i].alg_id; @@ -690,6 +733,55 @@ static int snapshot_load_kernel_key(struct snapshot_data *data, if (ret < 0) goto out; + /* Verify the creation hash matches the creation data. */ + payload = key->payload.data[0]; + ret = sha256_data(payload->creation, payload->creation_len, certhash); + if (ret < 0) + goto out; + + if (memcmp(payload->creation_hash, certhash, SHA256_DIGEST_SIZE) != 0) { + ret = -EINVAL; + goto out; + } + + /* We now know that the creation data is authentic - parse it */ + + /* TPML_PCR_SELECTION.count */ + if (be32_to_cpu(*(int *)payload->creation) != 1) { + ret = -EINVAL; + goto out; + } + + if (be16_to_cpu(*(u16 *)&payload->creation[4]) != TPM_ALG_SHA256) { + ret = -EINVAL; + goto out; + } + + if (*(char *)&payload->creation[6] != 3) { + ret = -EINVAL; + goto out; + } + + /* PCR 23 selected */ + if (be32_to_cpu(*(int *)&payload->creation[6]) != 0x03000080) { + ret = -EINVAL; + goto out; + } + + if (be16_to_cpu(*(u16 *)&payload->creation[10]) != + SHA256_DIGEST_SIZE) { + ret = -EINVAL; + goto out; + } + + /* Verify PCR 23 contained the expected value when the key was created. */ + if (memcmp(&payload->creation[12], expected_digest, + SHA256_DIGEST_SIZE) != 0) { + + ret = -EINVAL; + goto out; + } + data->key = key; key = NULL;