From patchwork Sat Feb 20 01:32:55 2021 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Matthew Garrett X-Patchwork-Id: 385439 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-26.3 required=3.0 tests=BAYES_00,DKIMWL_WL_MED, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, INCLUDES_CR_TRAILER, INCLUDES_PATCH, MAILING_LIST_MULTI, SPF_HELO_NONE, SPF_PASS, USER_AGENT_GIT,USER_IN_DEF_DKIM_WL autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 13304C433E6 for ; Sat, 20 Feb 2021 01:35:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id DDBA464E77 for ; Sat, 20 Feb 2021 01:35:30 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S230024AbhBTBfM (ORCPT ); Fri, 19 Feb 2021 20:35:12 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44172 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229996AbhBTBfE (ORCPT ); Fri, 19 Feb 2021 20:35:04 -0500 Received: from mail-yb1-xb49.google.com (mail-yb1-xb49.google.com [IPv6:2607:f8b0:4864:20::b49]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id DD784C061A2E for ; Fri, 19 Feb 2021 17:33:21 -0800 (PST) Received: by mail-yb1-xb49.google.com with SMTP id u17so8910099ybi.10 for ; Fri, 19 Feb 2021 17:33:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=sender:date:in-reply-to:message-id:mime-version:references:subject :from:to:cc; bh=AHjbHsJdHsjDWlT0meS/7wKVqgJA5qMsPwUMgz7CTrY=; b=DPjRo4j75pe5NPWUZw2PULq38PKScJgLe5C694z+Od25e1mgQhQ+0ZXITV67hlasB7 BHs9xe+ceb9RhAHRmdX19BKDLmd5FIXfgd8HemfRm4tTBBBAbKdirqtCV3bLbCZ6fMgH Fx4DgvBfX2gig6RPjueqXD+IlBOr8gwiqtvTUgGre0W6u7Vgp1DYhkYrStASE96rNlLp 1+kNlWDHPnwUYBF4nGUn+mChnYkhsFYkxPUUGh4bK1qbtcGhqDDiGUFIPRRT2WDqRi4T MtI3kHh6oBvhW7sOheb/oGp2WKxKuMWh9Rk58TkctHC7Apr/uCRNteVL4cLuYcZAVg/H 126Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:in-reply-to:message-id:mime-version :references:subject:from:to:cc; bh=AHjbHsJdHsjDWlT0meS/7wKVqgJA5qMsPwUMgz7CTrY=; b=Z2mmFjb3OyMoUFSBk4ZK5h/ofJnr/+WcZOE4X2xMeXDpYh/Q/56f04NQpVgFOinspu J7zbrMb2KrnhJI+N2YLPV/eU4Pb7YlrRTBSdoyyqO98yFX8e5MG9iZyy5woJBL3cQkbv dwTNHBsfaQ2dAINxxKBZgKNyXIy9KeRWP/MSX61TU4Ti7FsojrSyg6LhTxMpUILK93Sx 7/wet+KmjTDLss7crhU59e1cAzbDSW2Jj4pLUO+CX2FCTwqDDqofGbKXoHasrvgvERXo /tX/c554E21W4Cz/p0fCwV5MvsQteTAuZiIA737o3PBurf+j1Tq7OVEXf9oAqL7RTFC0 XVlQ== X-Gm-Message-State: AOAM5300Q7wuOzY38LrvgYwWFSO9UmP6sQFjlDywvDuj1X2K/WNlfQlc v+bhMHQ2QuAC2z3nyhUcP3XHiw8AZU7wMnlxJ45g8g== X-Google-Smtp-Source: ABdhPJzDmDLe4ZPw7iSJPXc33ot7QHjnB/KrkLLd5Ij4DEcK/c6DsPaOS9aOJK39H4e6EnR2yDtA16zvqnpOF8cRLY0/9Q== Sender: "matthewgarrett via sendgmr" X-Received: from matthewgarrett-tmp.c.googlers.com ([fda3:e722:ac3:10:7f:e700:c0a8:1081]) (user=matthewgarrett job=sendgmr) by 2002:a25:4112:: with SMTP id o18mr17366423yba.222.1613784801141; Fri, 19 Feb 2021 17:33:21 -0800 (PST) Date: Sat, 20 Feb 2021 01:32:55 +0000 In-Reply-To: <20210220013255.1083202-1-matthewgarrett@google.com> Message-Id: <20210220013255.1083202-10-matthewgarrett@google.com> Mime-Version: 1.0 References: <20210220013255.1083202-1-matthewgarrett@google.com> X-Mailer: git-send-email 2.30.0.617.g56c4b15f3c-goog Subject: [PATCH 9/9] pm: hibernate: seal the encryption key with a PCR policy From: Matthew Garrett To: linux-kernel@vger.kernel.org Cc: linux-integrity@vger.kernel.org, linux-pm@vger.kernel.org, keyrings@vger.kernel.org, zohar@linux.ibm.com, jejb@linux.ibm.com, jarkko@kernel.org, corbet@lwn.net, rjw@rjwysocki.net, Matthew Garrett , Matthew Garrett Precedence: bulk List-ID: X-Mailing-List: linux-pm@vger.kernel.org The key blob is not secret, and by default the TPM will happily unseal it regardless of system state. We can protect against that by sealing the secret with a PCR policy - if the current PCR state doesn't match, the TPM will refuse to release the secret. For now let's just seal it to PCR 23. In the long term we may want a more flexible policy around this, such as including PCR 7. Signed-off-by: Matthew Garrett --- include/linux/tpm.h | 4 ++ kernel/power/tpm.c | 161 ++++++++++++++++++++++++++++++++++++++++++-- 2 files changed, 160 insertions(+), 5 deletions(-) diff --git a/include/linux/tpm.h b/include/linux/tpm.h index f6970986b097..2e0141978c87 100644 --- a/include/linux/tpm.h +++ b/include/linux/tpm.h @@ -225,18 +225,22 @@ enum tpm2_command_codes { TPM2_CC_CONTEXT_LOAD = 0x0161, TPM2_CC_CONTEXT_SAVE = 0x0162, TPM2_CC_FLUSH_CONTEXT = 0x0165, + TPM2_CC_START_AUTH_SESSION = 0x0176, TPM2_CC_VERIFY_SIGNATURE = 0x0177, TPM2_CC_GET_CAPABILITY = 0x017A, TPM2_CC_GET_RANDOM = 0x017B, TPM2_CC_PCR_READ = 0x017E, + TPM2_CC_POLICY_PCR = 0x017F, TPM2_CC_PCR_EXTEND = 0x0182, TPM2_CC_EVENT_SEQUENCE_COMPLETE = 0x0185, TPM2_CC_HASH_SEQUENCE_START = 0x0186, + TPM2_CC_POLICY_GET_DIGEST = 0x0189, TPM2_CC_CREATE_LOADED = 0x0191, TPM2_CC_LAST = 0x0193, /* Spec 1.36 */ }; enum tpm2_permanent_handles { + TPM2_RH_NULL = 0x40000007, TPM2_RS_PW = 0x40000009, }; diff --git a/kernel/power/tpm.c b/kernel/power/tpm.c index 34e6cfb98ce4..5de27c2f08be 100644 --- a/kernel/power/tpm.c +++ b/kernel/power/tpm.c @@ -125,6 +125,118 @@ static int swsusp_enc_dec(struct trusted_key_payload *payload, char *buf, return ret; } +static int tpm_setup_policy(struct tpm_chip *chip, int *session_handle) +{ + struct tpm_header *head; + struct tpm_buf buf; + char nonce[32] = {0x00}; + int rc; + + rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, + TPM2_CC_START_AUTH_SESSION); + if (rc) + return rc; + + /* Decrypt key */ + tpm_buf_append_u32(&buf, TPM2_RH_NULL); + + /* Auth entity */ + tpm_buf_append_u32(&buf, TPM2_RH_NULL); + + /* Nonce - blank is fine here */ + tpm_buf_append_u16(&buf, sizeof(nonce)); + tpm_buf_append(&buf, nonce, sizeof(nonce)); + + /* Encrypted secret - empty */ + tpm_buf_append_u16(&buf, 0); + + /* Policy type - session */ + tpm_buf_append_u8(&buf, 0x01); + + /* Encryption type - NULL */ + tpm_buf_append_u16(&buf, TPM_ALG_NULL); + + /* Hash type - SHA256 */ + tpm_buf_append_u16(&buf, TPM_ALG_SHA256); + + rc = tpm_send(chip, buf.data, tpm_buf_length(&buf)); + + if (rc) + goto out; + + head = (struct tpm_header *)buf.data; + + if (be32_to_cpu(head->length) != sizeof(struct tpm_header) + + sizeof(int) + sizeof(u16) + sizeof(nonce)) { + rc = -EINVAL; + goto out; + } + + *session_handle = be32_to_cpu(*(int *)&buf.data[10]); + memcpy(nonce, &buf.data[16], sizeof(nonce)); + + tpm_buf_destroy(&buf); + + rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_POLICY_PCR); + if (rc) + return rc; + + tpm_buf_append_u32(&buf, *session_handle); + + /* PCR digest - read from the PCR, we'll verify creation data later */ + tpm_buf_append_u16(&buf, 0); + + /* One PCR */ + tpm_buf_append_u32(&buf, 1); + + /* SHA256 banks */ + tpm_buf_append_u16(&buf, TPM_ALG_SHA256); + + /* Select PCR 23 */ + tpm_buf_append_u32(&buf, 0x03000080); + + rc = tpm_send(chip, buf.data, tpm_buf_length(&buf)); + + if (rc) + goto out; + +out: + tpm_buf_destroy(&buf); + return rc; +} + +static int tpm_policy_get_digest(struct tpm_chip *chip, int handle, + char *digest) +{ + struct tpm_header *head; + struct tpm_buf buf; + int rc; + + rc = tpm_buf_init(&buf, TPM2_ST_NO_SESSIONS, TPM2_CC_POLICY_GET_DIGEST); + if (rc) + return rc; + + tpm_buf_append_u32(&buf, handle); + + rc = tpm_send(chip, buf.data, tpm_buf_length(&buf)); + + if (rc) + goto out; + + head = (struct tpm_header *)buf.data; + if (be32_to_cpu(head->length) != sizeof(struct tpm_header) + + sizeof(u16) + SHA256_DIGEST_SIZE) { + rc = -EINVAL; + goto out; + } + + memcpy(digest, &buf.data[12], SHA256_DIGEST_SIZE); +out: + tpm_buf_destroy(&buf); + + return rc; +} + static int tpm_certify_creationdata(struct tpm_chip *chip, struct trusted_key_payload *payload) { @@ -182,11 +294,14 @@ int swsusp_encrypt_digest(struct swsusp_header *header) const struct cred *cred = current_cred(); struct trusted_key_payload *payload; struct tpm_digest *digests = NULL; + char policy[SHA256_DIGEST_SIZE]; + char *policydigest = NULL; struct tpm_chip *chip; struct key *key; + int session_handle; int ret, i; - - char *keyinfo = "new\t32\tkeyhandle=0x81000001\tcreationpcrs=0x00800000"; + char *keyinfo = NULL; + char *keytemplate = "new\t32\tkeyhandle=0x81000001\tcreationpcrs=0x00800000\tpolicydigest=%s"; chip = tpm_default_chip(); @@ -213,10 +328,35 @@ int swsusp_encrypt_digest(struct swsusp_header *header) memcpy(&digests[i], &digest, sizeof(digest)); } + policydigest = kmalloc(SHA256_DIGEST_SIZE * 2 + 1, GFP_KERNEL); + if (!policydigest) { + ret = -ENOMEM; + goto reset; + } + ret = tpm_pcr_extend(chip, 23, digests); if (ret != 0) goto reset; + ret = tpm_setup_policy(chip, &session_handle); + + if (ret != 0) + goto reset; + + ret = tpm_policy_get_digest(chip, session_handle, policy); + + if (ret != 0) + goto reset; + + bin2hex(policydigest, policy, SHA256_DIGEST_SIZE); + policydigest[64] = '\0'; + + keyinfo = kasprintf(GFP_KERNEL, keytemplate, policydigest); + if (!keyinfo) { + ret = -ENOMEM; + goto reset; + } + key = key_alloc(&key_type_trusted, "swsusp", GLOBAL_ROOT_UID, GLOBAL_ROOT_GID, cred, 0, KEY_ALLOC_NOT_IN_QUOTA, NULL); @@ -228,6 +368,7 @@ int swsusp_encrypt_digest(struct swsusp_header *header) ret = key_instantiate_and_link(key, keyinfo, strlen(keyinfo) + 1, NULL, NULL); + if (ret < 0) goto error; @@ -244,6 +385,8 @@ int swsusp_encrypt_digest(struct swsusp_header *header) key_revoke(key); key_put(key); reset: + kfree(keyinfo); + kfree(policydigest); kfree(digests); tpm_pcr_reset(chip, 23); return ret; @@ -252,13 +395,14 @@ int swsusp_encrypt_digest(struct swsusp_header *header) int swsusp_decrypt_digest(struct swsusp_header *header) { const struct cred *cred = current_cred(); - char *keytemplate = "load\t%s\tkeyhandle=0x81000001"; + char *keytemplate = "load\t%s\tkeyhandle=0x81000001\tpolicyhandle=0x%x"; struct trusted_key_payload *payload; struct tpm_digest *digests = NULL; char certhash[SHA256_DIGEST_SIZE]; char *blobstring = NULL; char *keyinfo = NULL; struct tpm_chip *chip; + int session_handle; struct key *key; int i, ret; @@ -291,15 +435,22 @@ int swsusp_decrypt_digest(struct swsusp_header *header) if (ret != 0) goto reset; - blobstring = kmalloc(header->blob_len * 2, GFP_KERNEL); + ret = tpm_setup_policy(chip, &session_handle); + + if (ret != 0) + goto reset; + + blobstring = kmalloc(header->blob_len * 2 + 1, GFP_KERNEL); if (!blobstring) { ret = -ENOMEM; goto reset; } bin2hex(blobstring, header->blob, header->blob_len); + blobstring[header->blob_len * 2] = '\0'; - keyinfo = kasprintf(GFP_KERNEL, keytemplate, blobstring); + keyinfo = kasprintf(GFP_KERNEL, keytemplate, blobstring, + session_handle); if (!keyinfo) { ret = -ENOMEM; goto reset;