From patchwork Tue Aug 23 22:25:25 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Evan Green X-Patchwork-Id: 12952704 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 14A3EC32772 for ; Tue, 23 Aug 2022 22:27:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233888AbiHWW1Y (ORCPT ); Tue, 23 Aug 2022 18:27:24 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53438 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234139AbiHWW0g (ORCPT ); Tue, 23 Aug 2022 18:26:36 -0400 Received: from mail-pf1-x434.google.com (mail-pf1-x434.google.com [IPv6:2607:f8b0:4864:20::434]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E77648769C for ; Tue, 23 Aug 2022 15:26:24 -0700 (PDT) Received: by mail-pf1-x434.google.com with SMTP id x19so11984717pfq.1 for ; Tue, 23 Aug 2022 15:26:24 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=chromium.org; s=google; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc; bh=Tz3YQHlg7lPKnl8810X0eKouDRImUz/13B9zincHNWA=; b=Wv5JaMMYwHBpWL278QUwYO9DY6IaHzIbnhZDnYZ96/QvRII8RcbPWBWjeBtmIne9le qZjwLds3yzxRjEg6PMgQ3+ZKVDefOo/26u8/e5VZJ/cL5jfRNsSkaJDBND30BF5msNY5 4x+4rQX6ve4nrYaBemGNl9KU+6ZM8ZYnIVDGQ= X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc; bh=Tz3YQHlg7lPKnl8810X0eKouDRImUz/13B9zincHNWA=; b=DvC3EZeuInvyQsHa1Le+6wlknHeKoefkUZF+8/mL4lLfUMptke81zReBeBI/VUVrQs aqr5k9eV5FWwnswebfDIXYRjyN4KrfSZvC6E/LpLdtoq3IzGQGIZfHw/p3brX2hrMGrT hl/AZGuiJMfWnTSCZ1xm/do8gVI+zsVI979QiZQfA7lSLBWtwYHL7LEUkOpC9JMKQ3O0 mGcTUc64O0FpBWBNU2RNsOSWC/ffbBqXuzD0Upd1tMN0GdljiD47rOJlNc5cnMkH/2aV GqQ//D+1mMknIpYZHyCMNaqOaFXwsWPQDA+SASvjgNbWkBGe20HJ5VnW2dflBIIEmMX4 Q4NQ== X-Gm-Message-State: ACgBeo2dMK99QuAP5L/KIpzD4KXpMnm2Xq/pucO888hz2f5rsvdoJ6jH ZV6c8BD7G2UYp/ENNvoWuUivcA== X-Google-Smtp-Source: AA6agR7FQ9WlKLJeWlN4z1N50CerpdT2pXOjpoZwpiqb82lHYslzyUvA7umGVzB89k5iWjoebs0Wdg== X-Received: by 2002:aa7:94a4:0:b0:536:4ec6:2de2 with SMTP id a4-20020aa794a4000000b005364ec62de2mr16717815pfl.33.1661293584432; Tue, 23 Aug 2022 15:26:24 -0700 (PDT) Received: from evgreen-glaptop.lan ([98.45.66.167]) by smtp.gmail.com with ESMTPSA id f76-20020a62384f000000b0052f20d70845sm11256292pfa.150.2022.08.23.15.26.22 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Aug 2022 15:26:24 -0700 (PDT) From: Evan Green To: linux-kernel@vger.kernel.org Cc: gwendal@chromium.org, Eric Biggers , Matthew Garrett , jarkko@kernel.org, zohar@linux.ibm.com, linux-integrity@vger.kernel.org, Pavel Machek , apronin@chromium.org, dlunev@google.com, rjw@rjwysocki.net, linux-pm@vger.kernel.org, corbet@lwn.net, jejb@linux.ibm.com, Evan Green , Len Brown , "Rafael J. Wysocki" Subject: [PATCH v2 09/10] PM: hibernate: Verify the digest encryption key Date: Tue, 23 Aug 2022 15:25:25 -0700 Message-Id: <20220823152108.v2.9.I504d456c7a94ef1aaa7a2c63775ce9690c3ad7ab@changeid> X-Mailer: git-send-email 2.31.0 In-Reply-To: <20220823222526.1524851-1-evgreen@chromium.org> References: <20220823222526.1524851-1-evgreen@chromium.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-pm@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. Changes in v2: - Fixed some sparse warnings - Use CRYPTO_LIB_SHA256 to get rid of sha256_data() (Eric) - Adjusted offsets due to new ASN.1 format, and added a creation data length check. kernel/power/snapenc.c | 67 ++++++++++++++++++++++++++++++++++++++++-- 1 file changed, 65 insertions(+), 2 deletions(-) diff --git a/kernel/power/snapenc.c b/kernel/power/snapenc.c index e0b902d2dcf13a..1f08942450775a 100644 --- a/kernel/power/snapenc.c +++ b/kernel/power/snapenc.c @@ -22,6 +22,12 @@ 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}; + /* Derive a key from the kernel and user keys for data encryption. */ static int snapshot_use_user_key(struct snapshot_data *data) { @@ -486,7 +492,7 @@ static int snapshot_create_kernel_key(struct snapshot_data *data) struct key *key = NULL; 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) @@ -605,6 +611,7 @@ 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; @@ -612,6 +619,7 @@ static int snapshot_load_kernel_key(struct snapshot_data *data, char *keyinfo = NULL; struct tpm_chip *chip; struct key *key = NULL; + struct trusted_key_payload *payload; int i, ret; chip = tpm_default_chip(); @@ -629,8 +637,10 @@ 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 out; + } for (i = 0; i <= chip->nr_allocated_banks; i++) { digests[i].alg_id = chip->allocated_banks[i].alg_id; @@ -670,6 +680,59 @@ 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]; + if (!payload->creation || !payload->creation_hash || + (payload->creation_len < 3) || + (payload->creation_hash_len < SHA256_DIGEST_SIZE)) { + ret = -EINVAL; + goto out; + } + + sha256(payload->creation + 2, payload->creation_len - 2, certhash); + if (memcmp(payload->creation_hash + 2, 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(*(__be32 *)&payload->creation[2]) != 1) { + ret = -EINVAL; + goto out; + } + + if (be16_to_cpu(*(__be16 *)&payload->creation[6]) != TPM_ALG_SHA256) { + ret = -EINVAL; + goto out; + } + + if (*(char *)&payload->creation[8] != 3) { + ret = -EINVAL; + goto out; + } + + /* PCR 23 selected */ + if (be32_to_cpu(*(__be32 *)&payload->creation[8]) != 0x03000080) { + ret = -EINVAL; + goto out; + } + + if (be16_to_cpu(*(__be16 *)&payload->creation[12]) != + SHA256_DIGEST_SIZE) { + ret = -EINVAL; + goto out; + } + + /* Verify PCR 23 contained the expected value when the key was created. */ + if (memcmp(&payload->creation[14], expected_digest, + SHA256_DIGEST_SIZE) != 0) { + + ret = -EINVAL; + goto out; + } + data->key = key; key = NULL;