From patchwork Thu Nov 3 18:01:16 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Evan Green X-Patchwork-Id: 13030797 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 525DFC4332F for ; Thu, 3 Nov 2022 18:05:01 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230011AbiKCSE5 (ORCPT ); Thu, 3 Nov 2022 14:04:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:38018 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231185AbiKCSEM (ORCPT ); Thu, 3 Nov 2022 14:04:12 -0400 Received: from mail-pl1-x632.google.com (mail-pl1-x632.google.com [IPv6:2607:f8b0:4864:20::632]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7341723BF9 for ; Thu, 3 Nov 2022 11:01:53 -0700 (PDT) Received: by mail-pl1-x632.google.com with SMTP id 4so2707718pli.0 for ; Thu, 03 Nov 2022 11:01:53 -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:subject:date :message-id:reply-to; bh=gN9qKMAhYJlqKuIbqJEoz2jqEFif72BoLEhc9K1zc0g=; b=Z/A7qsCsCNMQebxMQUC7jeFHDbsCaxq6l6xjtJLdKNsLMO2wJ1eVH+54fYkt67yJIZ 5EeKE7mZJBZeCt+yZ24MTMX5WMFvtd4imlOBNzHP4jhjjMA8t6qbm6NjK49G+9baNTYq Hb/NFEIIMs+34NLi/jQmUCZzQIilo0WZ7iMvQ= 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 :subject:date:message-id:reply-to; bh=gN9qKMAhYJlqKuIbqJEoz2jqEFif72BoLEhc9K1zc0g=; b=pHwvoAVUzFzhPyG1k/yXWLpNAJikfna/b4cj4jarYNvga1ZtZxeEQyi8xKRPNdzMHS WKVY8WFggvES6bOH72wLcUyFDOTHpzamCoAzXTLKYm/4LczGe7StQbndIuFdWPjkYlaj +8sycOcUjMsPrfewDI0pTaAZUAkbTGUj5OXBzgNfV9yE+apA/0FpDzO17l8x8iiW1or5 gPd0WXoroiyUkou+OHGPJ5VWLyelSRsJREaB6SOw8qKeEVOZdrhrEbQyneD55H3+mWbP 4R/9MKtwHKQucYp3gbqPc8skZniBqb1/gfcZHioHUjmrWSYZ01TRB5halezptnIegvKV WbbQ== X-Gm-Message-State: ACrzQf3InOlsDDvvQQZ0nwM/zAUBreVztY/1ViWNmEEORY04sg+gQwo2 bEUWQ2j6/HlgxZdPFsCO4Lpc9szRSzvc49gB X-Google-Smtp-Source: AMsMyM5a8tzGl/cuGVJLwZgHv1F/Lsn8ZnybwoSrB6/BbEzupQ6p0duRG7+uxZmiFVkZrKcswz9S4Q== X-Received: by 2002:a17:90b:118a:b0:213:bbbc:8f09 with SMTP id gk10-20020a17090b118a00b00213bbbc8f09mr28269131pjb.64.1667498513109; Thu, 03 Nov 2022 11:01:53 -0700 (PDT) Received: from evgreen-glaptop.lan ([98.45.28.95]) by smtp.gmail.com with ESMTPSA id t12-20020a1709027fcc00b00177fb862a87sm1000277plb.20.2022.11.03.11.01.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Thu, 03 Nov 2022 11:01:52 -0700 (PDT) From: Evan Green To: linux-kernel@vger.kernel.org Cc: corbet@lwn.net, linux-pm@vger.kernel.org, rjw@rjwysocki.net, gwendal@chromium.org, apronin@chromium.org, Pavel Machek , Kees Cook , Matthew Garrett , linux-integrity@vger.kernel.org, jejb@linux.ibm.com, zohar@linux.ibm.com, dlunev@google.com, Eric Biggers , Ben Boeckel , jarkko@kernel.org, Evan Green , Len Brown , "Rafael J. Wysocki" Subject: [PATCH v4 08/11] PM: hibernate: Use TPM-backed keys to encrypt image Date: Thu, 3 Nov 2022 11:01:16 -0700 Message-Id: <20221103105558.v4.8.Ibd067e73916b9fae268a5824c2dd037416426af8@changeid> X-Mailer: git-send-email 2.38.1.431.g37b22c650d-goog In-Reply-To: <20221103180120.752659-1-evgreen@chromium.org> References: <20221103180120.752659-1-evgreen@chromium.org> MIME-Version: 1.0 Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org When using encrypted hibernate images, have the TPM create a key for us and seal it. By handing back a sealed blob instead of the raw key, we prevent usermode from being able to decrypt and tamper with the hibernate image on a different machine. We'll also go through the motions of having PCR23 set to a known value at the time of key creation and unsealing. Currently there's nothing that enforces the contents of PCR23 as a condition to unseal the key blob, that will come in a later change. Sourced-from: Matthew Garrett Signed-off-by: Evan Green Reviewed-by: Kees Cook --- Matthew's incarnation of this patch is at: https://patchwork.kernel.org/project/linux-pm/patch/20210220013255.1083202-9-matthewgarrett@google.com/ Changes in v4: - s/tpm_pcr_reset/tpm2_pcr_reset/ due to change in other patch - Variable ordering and whitespace fixes (Jarkko) - Add NULL check explanation in teardown (Jarkko) - Change strlen+1 to sizeof for static buffer (Jarkko) - Fix nr_allocated_banks loop overflow (found via KASAN) Changes in v3: - ENCRYPTED_HIBERNATION needs TRUSTED_KEYS builtin for key_type_trusted. - Remove KEYS dependency since it's covered by TRUSTED_KEYS (Kees) Changes in v2: - Rework load/create_kernel_key() to eliminate a label (Andrey) - Call put_device() needed from calling tpm_default_chip(). kernel/power/Kconfig | 1 + kernel/power/snapenc.c | 211 +++++++++++++++++++++++++++++++++++++++-- kernel/power/user.h | 1 + 3 files changed, 204 insertions(+), 9 deletions(-) diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig index cd574af0b43379..2f8acbd87b34dc 100644 --- a/kernel/power/Kconfig +++ b/kernel/power/Kconfig @@ -96,6 +96,7 @@ config ENCRYPTED_HIBERNATION bool "Encryption support for userspace snapshots" depends on HIBERNATION_SNAPSHOT_DEV depends on CRYPTO_AEAD2=y + depends on TRUSTED_KEYS=y default n help Enable support for kernel-based encryption of hibernation snapshots diff --git a/kernel/power/snapenc.c b/kernel/power/snapenc.c index f215df16dad4d3..7ff4fc66f7500c 100644 --- a/kernel/power/snapenc.c +++ b/kernel/power/snapenc.c @@ -4,13 +4,23 @@ #include #include #include +#include +#include #include #include +#include #include #include "power.h" #include "user.h" +/* sha256("To sleep, perchance to dream") */ +static struct tpm_digest known_digest = { .alg_id = TPM_ALG_SHA256, + .digest = {0x92, 0x78, 0x3d, 0x79, 0x2d, 0x00, 0x31, 0xb0, 0x55, 0xf9, + 0x1e, 0x0d, 0xce, 0x83, 0xde, 0x1d, 0xc4, 0xc5, 0x8e, 0x8c, + 0xf1, 0x22, 0x38, 0x6c, 0x33, 0xb1, 0x14, 0xb7, 0xec, 0x05, + 0x5f, 0x49}}; + /* Encrypt more data from the snapshot into the staging area. */ static int snapshot_encrypt_refill(struct snapshot_data *data) { @@ -314,6 +324,16 @@ void snapshot_teardown_encryption(struct snapshot_data *data) { int i; + /* + * Do NULL checks so this function can safely be called from error paths + * and other places where this context may not be fully set up. + */ + if (data->key) { + key_revoke(data->key); + key_put(data->key); + data->key = NULL; + } + if (data->aead_req) { aead_request_free(data->aead_req); data->aead_req = NULL; @@ -382,10 +402,82 @@ static int snapshot_setup_encryption_common(struct snapshot_data *data) return rc; } +static int snapshot_create_kernel_key(struct snapshot_data *data) +{ + /* Create a key sealed by the SRK. */ + char *keyinfo = "new\t32\tkeyhandle=0x81000000"; + const struct cred *cred = current_cred(); + struct tpm_digest *digests = NULL; + struct key *key = NULL; + struct tpm_chip *chip; + int ret, i; + + chip = tpm_default_chip(); + if (!chip) + return -ENODEV; + + if (!(tpm_is_tpm2(chip))) { + ret = -ENODEV; + goto out_dev; + } + + ret = tpm2_pcr_reset(chip, 23); + if (ret) + goto out; + + digests = kcalloc(chip->nr_allocated_banks, sizeof(struct tpm_digest), + GFP_KERNEL); + 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; + if (digests[i].alg_id == known_digest.alg_id) + memcpy(&digests[i], &known_digest, sizeof(known_digest)); + } + + ret = tpm_pcr_extend(chip, 23, digests); + if (ret != 0) + goto out; + + key = key_alloc(&key_type_trusted, "swsusp", GLOBAL_ROOT_UID, + GLOBAL_ROOT_GID, cred, 0, KEY_ALLOC_NOT_IN_QUOTA, + NULL); + + if (IS_ERR(key)) { + ret = PTR_ERR(key); + key = NULL; + goto out; + } + + ret = key_instantiate_and_link(key, keyinfo, sizeof(keyinfo), NULL, + NULL); + if (ret != 0) + goto out; + + data->key = key; + key = NULL; + +out: + if (key) { + key_revoke(key); + key_put(key); + } + + kfree(digests); + tpm2_pcr_reset(chip, 23); + +out_dev: + put_device(&chip->dev); + return ret; +} + int snapshot_get_encryption_key(struct snapshot_data *data, struct uswsusp_key_blob __user *key) { - u8 aead_key[SNAPSHOT_ENCRYPTION_KEY_SIZE]; + struct trusted_key_payload *payload; u8 nonce[USWSUSP_KEY_NONCE_SIZE]; int rc; @@ -401,21 +493,28 @@ int snapshot_get_encryption_key(struct snapshot_data *data, get_random_bytes(nonce, sizeof(nonce)); memcpy(&data->nonce_low, &nonce[0], sizeof(data->nonce_low)); memcpy(&data->nonce_high, &nonce[8], sizeof(data->nonce_high)); - /* Build a random key */ - get_random_bytes(aead_key, sizeof(aead_key)); - rc = crypto_aead_setkey(data->aead_tfm, aead_key, sizeof(aead_key)); + + /* Create a kernel key, and set it. */ + rc = snapshot_create_kernel_key(data); + if (rc) + goto fail; + + payload = data->key->payload.data[0]; + /* Install the key */ + rc = crypto_aead_setkey(data->aead_tfm, payload->key, SNAPSHOT_ENCRYPTION_KEY_SIZE); if (rc) goto fail; - /* Hand the key back to user mode (to be changed!) */ - rc = put_user(sizeof(struct uswsusp_key_blob), &key->blob_len); + /* Hand the key back to user mode in sealed form. */ + rc = put_user(payload->blob_len, &key->blob_len); if (rc) goto fail; - rc = copy_to_user(&key->blob, &aead_key, sizeof(aead_key)); + rc = copy_to_user(&key->blob, &payload->blob, payload->blob_len); if (rc) goto fail; + /* The nonce just gets handed back in the clear. */ rc = copy_to_user(&key->nonce, &nonce, sizeof(nonce)); if (rc) goto fail; @@ -427,10 +526,99 @@ int snapshot_get_encryption_key(struct snapshot_data *data, return rc; } +static int snapshot_load_kernel_key(struct snapshot_data *data, + struct uswsusp_key_blob *blob) +{ + + char *keytemplate = "load\t%s\tkeyhandle=0x81000000"; + const struct cred *cred = current_cred(); + struct tpm_digest *digests = NULL; + char *blobstring = NULL; + struct key *key = NULL; + struct tpm_chip *chip; + char *keyinfo = NULL; + int i, ret; + + chip = tpm_default_chip(); + if (!chip) + return -ENODEV; + + if (!(tpm_is_tpm2(chip))) { + ret = -ENODEV; + goto out_dev; + } + + ret = tpm2_pcr_reset(chip, 23); + if (ret) + goto out; + + digests = kcalloc(chip->nr_allocated_banks, sizeof(struct tpm_digest), + GFP_KERNEL); + if (!digests) + goto out; + + for (i = 0; i < chip->nr_allocated_banks; i++) { + digests[i].alg_id = chip->allocated_banks[i].alg_id; + if (digests[i].alg_id == known_digest.alg_id) + memcpy(&digests[i], &known_digest, sizeof(known_digest)); + } + + ret = tpm_pcr_extend(chip, 23, digests); + if (ret != 0) + goto out; + + blobstring = kmalloc(blob->blob_len * 2, GFP_KERNEL); + if (!blobstring) { + ret = -ENOMEM; + goto out; + } + + bin2hex(blobstring, blob->blob, blob->blob_len); + keyinfo = kasprintf(GFP_KERNEL, keytemplate, blobstring); + if (!keyinfo) { + ret = -ENOMEM; + goto out; + } + + key = key_alloc(&key_type_trusted, "swsusp", GLOBAL_ROOT_UID, + GLOBAL_ROOT_GID, cred, 0, KEY_ALLOC_NOT_IN_QUOTA, + NULL); + + if (IS_ERR(key)) { + ret = PTR_ERR(key); + key = NULL; + goto out; + } + + ret = key_instantiate_and_link(key, keyinfo, strlen(keyinfo) + 1, NULL, + NULL); + if (ret != 0) + goto out; + + data->key = key; + key = NULL; + +out: + if (key) { + key_revoke(key); + key_put(key); + } + + kfree(keyinfo); + kfree(blobstring); + kfree(digests); + tpm2_pcr_reset(chip, 23); + +out_dev: + put_device(&chip->dev); + return ret; +} + int snapshot_set_encryption_key(struct snapshot_data *data, struct uswsusp_key_blob __user *key) { struct uswsusp_key_blob blob; + struct trusted_key_payload *payload; int rc; /* It's too late if data's been pushed in. */ @@ -446,13 +634,18 @@ int snapshot_set_encryption_key(struct snapshot_data *data, if (rc) goto crypto_setup_fail; - if (blob.blob_len != sizeof(struct uswsusp_key_blob)) { + if (blob.blob_len > sizeof(key->blob)) { rc = -EINVAL; goto crypto_setup_fail; } + rc = snapshot_load_kernel_key(data, &blob); + if (rc) + goto crypto_setup_fail; + + payload = data->key->payload.data[0]; rc = crypto_aead_setkey(data->aead_tfm, - blob.blob, + payload->key, SNAPSHOT_ENCRYPTION_KEY_SIZE); if (rc) diff --git a/kernel/power/user.h b/kernel/power/user.h index ac429782abff85..6c86fb64ebe13e 100644 --- a/kernel/power/user.h +++ b/kernel/power/user.h @@ -31,6 +31,7 @@ struct snapshot_data { uint64_t crypt_total; uint64_t nonce_low; uint64_t nonce_high; + struct key *key; #endif };