From patchwork Tue Aug 23 22:25:17 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Evan Green X-Patchwork-Id: 12952678 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 40078C32772 for ; Tue, 23 Aug 2022 22:26:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233756AbiHWW02 (ORCPT ); Tue, 23 Aug 2022 18:26:28 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52632 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233254AbiHWW0E (ORCPT ); Tue, 23 Aug 2022 18:26:04 -0400 Received: from mail-pj1-x1034.google.com (mail-pj1-x1034.google.com [IPv6:2607:f8b0:4864:20::1034]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 8EDEC87096 for ; Tue, 23 Aug 2022 15:25:55 -0700 (PDT) Received: by mail-pj1-x1034.google.com with SMTP id x63-20020a17090a6c4500b001fabbf8debfso16087488pjj.4 for ; Tue, 23 Aug 2022 15:25:55 -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=xSQKGWLEW/kUQwiNWyncH9Xp5s+ASlV194q1jpJPOQw=; b=dMFSA6x1duIowrTxa5xI9MFep/heDTq8cj9utyAUvGpwtN0PBwCrEwYkBYtpfIA0XB u0o1PWf/neWzT73SL0XPQT95t6CsWbbKgg/5XtzZz8XrTQrio/0TBlopjgwfugE9iCeB J2ssMqpQ2fOEV3iLudF+Nrna/KhoEqJ+yPC7w= 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=xSQKGWLEW/kUQwiNWyncH9Xp5s+ASlV194q1jpJPOQw=; b=aLISseVQU3Md6c3Ntg0BIULsXyl5SqVn9We/mE6oQiXVgU5tWTmyeRQ5Gj8Ph54d4T U5XNh1SCnVKT2chIwjO13mmXSOynvuCA9a/zvvQmYWGe5GntJKMkrXR7FHKurUYLvhdd SWqio9qHXZlmVIbwFlwmePnL8cAIDQ/ZpQzDDa/70LoVQ7yzqv0oQde57/xyjUqrUOme UQouZ4NSY+II9yyVBIfJsSlCaowaifW+VPilmSOZ0t0B98P/N7Gd5DX3esVR+06eJhER 1ilQSv67OEW76NIxnxWEusCFVaMSRB29BaWUxwirz8Sap6Ms8zfIE0ge+1ZT3nfRA3za POQA== X-Gm-Message-State: ACgBeo3pispz2PrEc4CVSD0JJNK5rWFaEkBFE575ckQbugbEUD81dUZH jsTrF/MqmxkHzJxrBwAiliS4zQ== X-Google-Smtp-Source: AA6agR4EAufBpEOyvq0nP8MHgnnultni3r6jafYIEsU16dhG8QKjr+jH/gZgzBUiOrv2Hg5PMg0j8g== X-Received: by 2002:a17:90a:bf0a:b0:1fa:b53c:3f3a with SMTP id c10-20020a17090abf0a00b001fab53c3f3amr5247240pjs.126.1661293555045; Tue, 23 Aug 2022 15:25:55 -0700 (PDT) Received: from evgreen-glaptop.lan ([98.45.66.167]) by smtp.gmail.com with ESMTPSA id f76-20020a62384f000000b0052f20d70845sm11256292pfa.150.2022.08.23.15.25.53 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Aug 2022 15:25:54 -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, Matthew Garrett , Matthew Garrett , Evan Green , Hao Wu , Jason Gunthorpe , Peter Huewe , axelj Subject: [PATCH v2 01/10] tpm: Add support for in-kernel resetting of PCRs Date: Tue, 23 Aug 2022 15:25:17 -0700 Message-Id: <20220823152108.v2.1.I776854f47e3340cc2913ed4d8ecdd328048b73c3@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 From: Matthew Garrett Add an internal command for resetting a PCR. This will be used by the encrypted hibernation code to set PCR23 to a known value. The hibernation code will seal the hibernation key with a policy specifying PCR23 be set to this known value as a mechanism to ensure that the hibernation key is genuine. But to do this repeatedly, resetting the PCR is necessary as well. From: Matthew Garrett Signed-off-by: Matthew Garrett Signed-off-by: Evan Green --- Matthew's original version of this patch was at: https://patchwork.kernel.org/patch/12096487/ (no changes since v1) drivers/char/tpm/tpm-interface.c | 28 +++++++++++++++++++++++++ drivers/char/tpm/tpm.h | 2 ++ drivers/char/tpm/tpm1-cmd.c | 34 ++++++++++++++++++++++++++++++ drivers/char/tpm/tpm2-cmd.c | 36 ++++++++++++++++++++++++++++++++ include/linux/tpm.h | 7 +++++++ 5 files changed, 107 insertions(+) diff --git a/drivers/char/tpm/tpm-interface.c b/drivers/char/tpm/tpm-interface.c index 1621ce8187052c..17b8643ee109c2 100644 --- a/drivers/char/tpm/tpm-interface.c +++ b/drivers/char/tpm/tpm-interface.c @@ -342,6 +342,34 @@ int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, } EXPORT_SYMBOL_GPL(tpm_pcr_extend); +/** + * tpm_pcr_reset - reset the specified PCR + * @chip: a &struct tpm_chip instance, %NULL for the default chip + * @pcr_idx: the PCR to be reset + * + * Return: same as with tpm_transmit_cmd() + */ +int tpm_pcr_reset(struct tpm_chip *chip, u32 pcr_idx) +{ + int rc; + + chip = tpm_find_get_ops(chip); + if (!chip) + return -ENODEV; + + if (chip->flags & TPM_CHIP_FLAG_TPM2) { + rc = tpm2_pcr_reset(chip, pcr_idx); + goto out; + } + + rc = tpm1_pcr_reset(chip, pcr_idx, "attempting to reset a PCR"); + +out: + tpm_put_ops(chip); + return rc; +} +EXPORT_SYMBOL_GPL(tpm_pcr_reset); + /** * tpm_send - send a TPM command * @chip: a &struct tpm_chip instance, %NULL for the default chip diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h index 24ee4e1cc452a0..a80b341d38eb8c 100644 --- a/drivers/char/tpm/tpm.h +++ b/drivers/char/tpm/tpm.h @@ -175,6 +175,7 @@ int tpm1_get_timeouts(struct tpm_chip *chip); unsigned long tpm1_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal); int tpm1_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, const u8 *hash, const char *log_msg); +int tpm1_pcr_reset(struct tpm_chip *chip, u32 pcr_idx, const char *log_msg); int tpm1_pcr_read(struct tpm_chip *chip, u32 pcr_idx, u8 *res_buf); ssize_t tpm1_getcap(struct tpm_chip *chip, u32 subcap_id, cap_t *cap, const char *desc, size_t min_cap_length); @@ -217,6 +218,7 @@ int tpm2_pcr_read(struct tpm_chip *chip, u32 pcr_idx, struct tpm_digest *digest, u16 *digest_size_ptr); int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, struct tpm_digest *digests); +int tpm2_pcr_reset(struct tpm_chip *chip, u32 pcr_idx); int tpm2_get_random(struct tpm_chip *chip, u8 *dest, size_t max); ssize_t tpm2_get_tpm_pt(struct tpm_chip *chip, u32 property_id, u32 *value, const char *desc); diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c index cf64c738510529..8ec743dec26544 100644 --- a/drivers/char/tpm/tpm1-cmd.c +++ b/drivers/char/tpm/tpm1-cmd.c @@ -478,6 +478,40 @@ int tpm1_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, const u8 *hash, return rc; } +struct tpm_pcr_selection { + u16 size_of_select; + u8 pcr_select[3]; +} __packed; + +#define TPM_ORD_PCR_RESET 200 +int tpm1_pcr_reset(struct tpm_chip *chip, u32 pcr_idx, const char *log_msg) +{ + struct tpm_pcr_selection selection; + struct tpm_buf buf; + int i, rc; + char tmp; + + rc = tpm_buf_init(&buf, TPM_TAG_RQU_COMMAND, TPM_ORD_PCR_RESET); + if (rc) + return rc; + + selection.size_of_select = 3; + + for (i = 0; i < selection.size_of_select; i++) { + tmp = 0; + if (pcr_idx / 3 == i) { + pcr_idx -= i * 8; + tmp |= 1 << pcr_idx; + } + selection.pcr_select[i] = tmp; + } + tpm_buf_append(&buf, (u8 *)&selection, sizeof(selection)); + + rc = tpm_transmit_cmd(chip, &buf, sizeof(selection), log_msg); + tpm_buf_destroy(&buf); + return rc; +} + #define TPM_ORD_GET_CAP 101 ssize_t tpm1_getcap(struct tpm_chip *chip, u32 subcap_id, cap_t *cap, const char *desc, size_t min_cap_length) diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c index 65d03867e114c5..69126a6770386e 100644 --- a/drivers/char/tpm/tpm2-cmd.c +++ b/drivers/char/tpm/tpm2-cmd.c @@ -269,6 +269,42 @@ int tpm2_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, return rc; } +/** + * tpm2_pcr_reset() - reset a PCR + * + * @chip: TPM chip to use. + * @pcr_idx: index of the PCR. + * + * Return: Same as with tpm_transmit_cmd. + */ +int tpm2_pcr_reset(struct tpm_chip *chip, u32 pcr_idx) +{ + struct tpm_buf buf; + struct tpm2_null_auth_area auth_area; + int rc; + + rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_PCR_RESET); + if (rc) + return rc; + + tpm_buf_append_u32(&buf, pcr_idx); + + auth_area.handle = cpu_to_be32(TPM2_RS_PW); + auth_area.nonce_size = 0; + auth_area.attributes = 0; + auth_area.auth_size = 0; + + tpm_buf_append_u32(&buf, sizeof(struct tpm2_null_auth_area)); + tpm_buf_append(&buf, (const unsigned char *)&auth_area, + sizeof(auth_area)); + + rc = tpm_transmit_cmd(chip, &buf, 0, "attempting to reset a PCR"); + + tpm_buf_destroy(&buf); + + return rc; +} + struct tpm2_get_random_out { __be16 size; u8 buffer[TPM_MAX_RNG_DATA]; diff --git a/include/linux/tpm.h b/include/linux/tpm.h index dfeb25a0362dee..8320cbac6f4009 100644 --- a/include/linux/tpm.h +++ b/include/linux/tpm.h @@ -219,6 +219,7 @@ enum tpm2_command_codes { TPM2_CC_HIERARCHY_CONTROL = 0x0121, TPM2_CC_HIERARCHY_CHANGE_AUTH = 0x0129, TPM2_CC_CREATE_PRIMARY = 0x0131, + TPM2_CC_PCR_RESET = 0x013D, TPM2_CC_SEQUENCE_COMPLETE = 0x013E, TPM2_CC_SELF_TEST = 0x0143, TPM2_CC_STARTUP = 0x0144, @@ -423,6 +424,7 @@ extern ssize_t tpm_transmit_cmd(struct tpm_chip *chip, struct tpm_buf *buf, size_t min_rsp_body_length, const char *desc); extern int tpm_pcr_read(struct tpm_chip *chip, u32 pcr_idx, struct tpm_digest *digest); +extern int tpm_pcr_reset(struct tpm_chip *chip, u32 pcr_idx); extern int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, struct tpm_digest *digests); extern int tpm_send(struct tpm_chip *chip, void *cmd, size_t buflen); @@ -440,6 +442,11 @@ static inline int tpm_pcr_read(struct tpm_chip *chip, int pcr_idx, return -ENODEV; } +static inline int tpm_pcr_reset(struct tpm_chip *chip, int pcr_idx) +{ + return -ENODEV; +} + static inline int tpm_pcr_extend(struct tpm_chip *chip, u32 pcr_idx, struct tpm_digest *digests) { From patchwork Tue Aug 23 22:25:18 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Evan Green X-Patchwork-Id: 12952679 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 C3C67C32793 for ; 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Tue, 23 Aug 2022 15:26:00 -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, Matthew Garrett , Matthew Garrett , Evan Green , Jason Gunthorpe , Peter Huewe Subject: [PATCH v2 02/10] tpm: Allow PCR 23 to be restricted to kernel-only use Date: Tue, 23 Aug 2022 15:25:18 -0700 Message-Id: <20220823152108.v2.2.I9ded8c8caad27403e9284dfc78ad6cbd845bc98d@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 From: Matthew Garrett Under certain circumstances it might be desirable to enable the creation of TPM-backed secrets that are only accessible to the kernel. In an ideal world this could be achieved by using TPM localities, but these don't appear to be available on consumer systems. An alternative is to simply block userland from modifying one of the resettable PCRs, leaving it available to the kernel. If the kernel ensures that no userland can access the TPM while it is carrying out work, it can reset PCR 23, extend it to an arbitrary value, create or load a secret, and then reset the PCR again. Even if userland somehow obtains the sealed material, it will be unable to unseal it since PCR 23 will never be in the appropriate state. From: Matthew Garrett Signed-off-by: Matthew Garrett Signed-off-by: Evan Green --- Matthew's original version of this patch is at: https://patchwork.kernel.org/patch/12096491/ Changes in v2: - Fixed sparse warnings drivers/char/tpm/Kconfig | 10 +++++++++ drivers/char/tpm/tpm-dev-common.c | 8 +++++++ drivers/char/tpm/tpm.h | 21 +++++++++++++++++++ drivers/char/tpm/tpm1-cmd.c | 35 +++++++++++++++++++++++++++++++ drivers/char/tpm/tpm2-cmd.c | 22 +++++++++++++++++++ drivers/char/tpm/tpm2-space.c | 2 +- 6 files changed, 97 insertions(+), 1 deletion(-) diff --git a/drivers/char/tpm/Kconfig b/drivers/char/tpm/Kconfig index 927088b2c3d3f2..4483b61a428b11 100644 --- a/drivers/char/tpm/Kconfig +++ b/drivers/char/tpm/Kconfig @@ -211,4 +211,14 @@ config TCG_FTPM_TEE This driver proxies for firmware TPM running in TEE. source "drivers/char/tpm/st33zp24/Kconfig" + +config TCG_TPM_RESTRICT_PCR + bool "Restrict userland access to PCR 23" + depends on TCG_TPM + help + If set, block userland from extending or resetting PCR 23. This + allows it to be restricted to in-kernel use, preventing userland + from being able to make use of data sealed to the TPM by the kernel. + This is required for secure hibernation support, but should be left + disabled if any userland may require access to PCR23. endif # TCG_TPM diff --git a/drivers/char/tpm/tpm-dev-common.c b/drivers/char/tpm/tpm-dev-common.c index dc4c0a0a512903..7a4e618c7d1942 100644 --- a/drivers/char/tpm/tpm-dev-common.c +++ b/drivers/char/tpm/tpm-dev-common.c @@ -198,6 +198,14 @@ ssize_t tpm_common_write(struct file *file, const char __user *buf, priv->response_read = false; *off = 0; + if (priv->chip->flags & TPM_CHIP_FLAG_TPM2) + ret = tpm2_cmd_restricted(priv->chip, priv->data_buffer, size); + else + ret = tpm1_cmd_restricted(priv->chip, priv->data_buffer, size); + + if (ret) + goto out; + /* * If in nonblocking mode schedule an async job to send * the command return the size. diff --git a/drivers/char/tpm/tpm.h b/drivers/char/tpm/tpm.h index a80b341d38eb8c..077c3ca0a127ba 100644 --- a/drivers/char/tpm/tpm.h +++ b/drivers/char/tpm/tpm.h @@ -229,6 +229,8 @@ void tpm2_shutdown(struct tpm_chip *chip, u16 shutdown_type); unsigned long tpm2_calc_ordinal_duration(struct tpm_chip *chip, u32 ordinal); int tpm2_probe(struct tpm_chip *chip); int tpm2_get_cc_attrs_tbl(struct tpm_chip *chip); +int tpm_find_and_validate_cc(struct tpm_chip *chip, struct tpm_space *space, + const void *buf, size_t bufsiz); int tpm2_find_cc(struct tpm_chip *chip, u32 cc); int tpm2_init_space(struct tpm_space *space, unsigned int buf_size); void tpm2_del_space(struct tpm_chip *chip, struct tpm_space *space); @@ -244,4 +246,23 @@ void tpm_bios_log_setup(struct tpm_chip *chip); void tpm_bios_log_teardown(struct tpm_chip *chip); int tpm_dev_common_init(void); void tpm_dev_common_exit(void); + +#ifdef CONFIG_TCG_TPM_RESTRICT_PCR +#define TPM_RESTRICTED_PCR 23 + +int tpm1_cmd_restricted(struct tpm_chip *chip, u8 *buffer, size_t size); +int tpm2_cmd_restricted(struct tpm_chip *chip, u8 *buffer, size_t size); +#else +static inline int tpm1_cmd_restricted(struct tpm_chip *chip, u8 *buffer, + size_t size) +{ + return 0; +} + +static inline int tpm2_cmd_restricted(struct tpm_chip *chip, u8 *buffer, + size_t size) +{ + return 0; +} +#endif #endif diff --git a/drivers/char/tpm/tpm1-cmd.c b/drivers/char/tpm/tpm1-cmd.c index 8ec743dec26544..318e75ae42fb85 100644 --- a/drivers/char/tpm/tpm1-cmd.c +++ b/drivers/char/tpm/tpm1-cmd.c @@ -845,3 +845,38 @@ int tpm1_get_pcr_allocation(struct tpm_chip *chip) return 0; } + +#ifdef CONFIG_TCG_TPM_RESTRICT_PCR +int tpm1_cmd_restricted(struct tpm_chip *chip, u8 *buffer, size_t size) +{ + struct tpm_header *header = (struct tpm_header *)buffer; + char len, offset; + __be32 *pcr; + int pos; + + switch (be32_to_cpu(header->ordinal)) { + case TPM_ORD_PCR_EXTEND: + if (size < (TPM_HEADER_SIZE + sizeof(u32))) + return -EINVAL; + pcr = (__be32 *)&buffer[TPM_HEADER_SIZE]; + if (be32_to_cpu(*pcr) == TPM_RESTRICTED_PCR) + return -EPERM; + break; + case TPM_ORD_PCR_RESET: + if (size < (TPM_HEADER_SIZE + 1)) + return -EINVAL; + len = buffer[TPM_HEADER_SIZE]; + if (size < (TPM_HEADER_SIZE + 1 + len)) + return -EINVAL; + offset = TPM_RESTRICTED_PCR/3; + if (len < offset) + break; + pos = TPM_HEADER_SIZE + 1 + offset; + if (buffer[pos] & (1 << (TPM_RESTRICTED_PCR - 2 * offset))) + return -EPERM; + break; + } + + return 0; +} +#endif diff --git a/drivers/char/tpm/tpm2-cmd.c b/drivers/char/tpm/tpm2-cmd.c index 69126a6770386e..dbf7f5552c6782 100644 --- a/drivers/char/tpm/tpm2-cmd.c +++ b/drivers/char/tpm/tpm2-cmd.c @@ -821,3 +821,25 @@ int tpm2_find_cc(struct tpm_chip *chip, u32 cc) return -1; } + +#ifdef CONFIG_TCG_TPM_RESTRICT_PCR +int tpm2_cmd_restricted(struct tpm_chip *chip, u8 *buffer, size_t size) +{ + int cc = tpm_find_and_validate_cc(chip, NULL, buffer, size); + __be32 *handle; + + switch (cc) { + case TPM2_CC_PCR_EXTEND: + case TPM2_CC_PCR_RESET: + if (size < (TPM_HEADER_SIZE + sizeof(u32))) + return -EINVAL; + + handle = (__be32 *)&buffer[TPM_HEADER_SIZE]; + if (be32_to_cpu(*handle) == TPM_RESTRICTED_PCR) + return -EPERM; + break; + } + + return 0; +} +#endif diff --git a/drivers/char/tpm/tpm2-space.c b/drivers/char/tpm/tpm2-space.c index ffb35f0154c16c..6f51cd92c6400f 100644 --- a/drivers/char/tpm/tpm2-space.c +++ b/drivers/char/tpm/tpm2-space.c @@ -262,7 +262,7 @@ static int tpm2_map_command(struct tpm_chip *chip, u32 cc, u8 *cmd) return 0; } -static int tpm_find_and_validate_cc(struct tpm_chip *chip, +int tpm_find_and_validate_cc(struct tpm_chip *chip, struct tpm_space *space, const void *cmd, size_t len) { From patchwork Tue Aug 23 22:25:19 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Evan Green X-Patchwork-Id: 12952680 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 AE37DC32793 for ; Tue, 23 Aug 2022 22:26:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234175AbiHWW0n (ORCPT ); Tue, 23 Aug 2022 18:26:43 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52672 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233581AbiHWW0P (ORCPT ); Tue, 23 Aug 2022 18:26:15 -0400 Received: from mail-pj1-x1034.google.com (mail-pj1-x1034.google.com [IPv6:2607:f8b0:4864:20::1034]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 83DC886FE4 for ; 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Tue, 23 Aug 2022 15:26:05 -0700 (PDT) Received: from evgreen-glaptop.lan ([98.45.66.167]) by smtp.gmail.com with ESMTPSA id f76-20020a62384f000000b0052f20d70845sm11256292pfa.150.2022.08.23.15.26.03 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Aug 2022 15:26:04 -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 , David Howells , James Morris , Paul Moore , "Serge E. Hallyn" , keyrings@vger.kernel.org, linux-security-module@vger.kernel.org Subject: [PATCH v2 03/10] security: keys: trusted: Include TPM2 creation data Date: Tue, 23 Aug 2022 15:25:19 -0700 Message-Id: <20220823152108.v2.3.Ieb1215f598bc9df56b0e29e5977eae4fcca25e15@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 In addition to the private key and public key, the TPM2_Create command may also return creation data, a creation hash, and a creation ticket. These fields allow the TPM to attest to the contents of a specified set of PCRs at the time the trusted key was created. Encrypted hibernation will use this to ensure that PCRs settable only by the kernel were set properly at the time of creation, indicating this is an authentic hibernate key. Encode these additional parameters into the ASN.1 created to represent the key blob. The new fields are made optional so that they don't bloat key blobs which don't need them, and to ensure interoperability with old blobs. --- (no changes since v1) This is a replacement for Matthew's original patch here: https://patchwork.kernel.org/patch/12096489/ That patch was written before the exported key format was switched to ASN.1. This patch accomplishes the same thing (saving, loading, and getting pointers to the creation data) while utilizing the new ASN.1 format. Signed-off-by: Evan Green --- include/keys/trusted-type.h | 8 + security/keys/trusted-keys/tpm2key.asn1 | 5 +- security/keys/trusted-keys/trusted_tpm2.c | 202 +++++++++++++++++++--- 3 files changed, 190 insertions(+), 25 deletions(-) diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h index 4eb64548a74f1a..209086fed240a5 100644 --- a/include/keys/trusted-type.h +++ b/include/keys/trusted-type.h @@ -22,15 +22,23 @@ #define MAX_BLOB_SIZE 512 #define MAX_PCRINFO_SIZE 64 #define MAX_DIGEST_SIZE 64 +#define MAX_CREATION_DATA 412 +#define MAX_TK 76 struct trusted_key_payload { struct rcu_head rcu; unsigned int key_len; unsigned int blob_len; + unsigned int creation_len; + unsigned int creation_hash_len; + unsigned int tk_len; unsigned char migratable; unsigned char old_format; unsigned char key[MAX_KEY_SIZE + 1]; unsigned char blob[MAX_BLOB_SIZE]; + unsigned char *creation; + unsigned char *creation_hash; + unsigned char *tk; }; struct trusted_key_options { diff --git a/security/keys/trusted-keys/tpm2key.asn1 b/security/keys/trusted-keys/tpm2key.asn1 index f57f869ad60068..1bfbf290e523a3 100644 --- a/security/keys/trusted-keys/tpm2key.asn1 +++ b/security/keys/trusted-keys/tpm2key.asn1 @@ -7,5 +7,8 @@ TPMKey ::= SEQUENCE { emptyAuth [0] EXPLICIT BOOLEAN OPTIONAL, parent INTEGER ({tpm2_key_parent}), pubkey OCTET STRING ({tpm2_key_pub}), - privkey OCTET STRING ({tpm2_key_priv}) + privkey OCTET STRING ({tpm2_key_priv}), + creationData [1] EXPLICIT OCTET STRING OPTIONAL ({tpm2_key_creation_data}), + creationHash [2] EXPLICIT OCTET STRING OPTIONAL ({tpm2_key_creation_hash}), + creationTk [3] EXPLICIT OCTET STRING OPTIONAL ({tpm2_key_creation_tk}) } diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c index 2b2c8eb258d5bd..1f166d4fa307a9 100644 --- a/security/keys/trusted-keys/trusted_tpm2.c +++ b/security/keys/trusted-keys/trusted_tpm2.c @@ -37,7 +37,10 @@ static int tpm2_key_encode(struct trusted_key_payload *payload, u8 *work = scratch, *work1; u8 *end_work = scratch + SCRATCH_SIZE; u8 *priv, *pub; + u8 *creation_data = NULL, *creation_hash = NULL, *creation_tk = NULL; + u16 creation_data_len, creation_hash_len = 0, creation_tk_len = 0; u16 priv_len, pub_len; + int rc; priv_len = get_unaligned_be16(src) + 2; priv = src; @@ -46,6 +49,26 @@ static int tpm2_key_encode(struct trusted_key_payload *payload, pub_len = get_unaligned_be16(src) + 2; pub = src; + src += pub_len; + + creation_data_len = get_unaligned_be16(src); + if (creation_data_len) { + creation_data_len += 2; + creation_data = src; + src += creation_data_len; + + creation_hash_len = get_unaligned_be16(src) + 2; + creation_hash = src; + src += creation_hash_len; + + /* + * The creation ticket (TPMT_TK_CREATION) consists of a 2 byte + * tag, 4 byte handle, and then a TPM2B_DIGEST, which is a 2 + * byte length followed by data. + */ + creation_tk_len = get_unaligned_be16(src + 6) + 8; + creation_tk = src; + } if (!scratch) return -ENOMEM; @@ -63,26 +86,81 @@ static int tpm2_key_encode(struct trusted_key_payload *payload, } /* - * Assume both octet strings will encode to a 2 byte definite length + * Assume each octet string will encode to a 2 byte definite length. + * Each optional octet string consumes one extra byte. * - * Note: For a well behaved TPM, this warning should never - * trigger, so if it does there's something nefarious going on + * Note: For a well behaved TPM, this warning should never trigger, so + * if it does there's something nefarious going on */ - if (WARN(work - scratch + pub_len + priv_len + 14 > SCRATCH_SIZE, - "BUG: scratch buffer is too small")) - return -EINVAL; + if (WARN(work - scratch + pub_len + priv_len + creation_data_len + + creation_hash_len + creation_tk_len + (7 * 5) + 3 > + SCRATCH_SIZE, + "BUG: scratch buffer is too small")) { + rc = -EINVAL; + goto err; + } work = asn1_encode_integer(work, end_work, options->keyhandle); work = asn1_encode_octet_string(work, end_work, pub, pub_len); work = asn1_encode_octet_string(work, end_work, priv, priv_len); + if (creation_data_len) { + u8 *scratch2 = kmalloc(SCRATCH_SIZE, GFP_KERNEL); + u8 *work2; + u8 *end_work2 = scratch2 + SCRATCH_SIZE; + + if (!scratch2) { + rc = -ENOMEM; + goto err; + } + + work2 = asn1_encode_octet_string(scratch2, + end_work2, + creation_data, + creation_data_len); + + work = asn1_encode_tag(work, + end_work, + 1, + scratch2, + work2 - scratch2); + + work2 = asn1_encode_octet_string(scratch2, + end_work2, + creation_hash, + creation_hash_len); + + work = asn1_encode_tag(work, + end_work, + 2, + scratch2, + work2 - scratch2); + + work2 = asn1_encode_octet_string(scratch2, + end_work2, + creation_tk, + creation_tk_len); + + work = asn1_encode_tag(work, + end_work, + 3, + scratch2, + work2 - scratch2); + + kfree(scratch2); + } work1 = payload->blob; work1 = asn1_encode_sequence(work1, work1 + sizeof(payload->blob), scratch, work - scratch); - if (WARN(IS_ERR(work1), "BUG: ASN.1 encoder failed")) - return PTR_ERR(work1); + if (WARN(IS_ERR(work1), "BUG: ASN.1 encoder failed")) { + rc = PTR_ERR(work1); + goto err; + } return work1 - payload->blob; +err: + kfree(scratch); + return rc; } struct tpm2_key_context { @@ -91,15 +169,21 @@ struct tpm2_key_context { u32 pub_len; const u8 *priv; u32 priv_len; + const u8 *creation_data; + u32 creation_data_len; + const u8 *creation_hash; + u32 creation_hash_len; + const u8 *creation_tk; + u32 creation_tk_len; }; static int tpm2_key_decode(struct trusted_key_payload *payload, - struct trusted_key_options *options, - u8 **buf) + struct trusted_key_options *options) { + u64 data_len; int ret; struct tpm2_key_context ctx; - u8 *blob; + u8 *blob, *buf; memset(&ctx, 0, sizeof(ctx)); @@ -108,21 +192,57 @@ static int tpm2_key_decode(struct trusted_key_payload *payload, if (ret < 0) return ret; - if (ctx.priv_len + ctx.pub_len > MAX_BLOB_SIZE) + data_len = ctx.priv_len + ctx.pub_len + ctx.creation_data_len + + ctx.creation_hash_len + ctx.creation_tk_len; + + if (data_len > MAX_BLOB_SIZE) return -EINVAL; - blob = kmalloc(ctx.priv_len + ctx.pub_len + 4, GFP_KERNEL); - if (!blob) + buf = kmalloc(data_len + 4, GFP_KERNEL); + if (!buf) return -ENOMEM; - *buf = blob; + blob = buf; options->keyhandle = ctx.parent; memcpy(blob, ctx.priv, ctx.priv_len); blob += ctx.priv_len; memcpy(blob, ctx.pub, ctx.pub_len); + blob += ctx.pub_len; + if (ctx.creation_data_len) { + memcpy(blob, ctx.creation_data, ctx.creation_data_len); + blob += ctx.creation_data_len; + } + + if (ctx.creation_hash_len) { + memcpy(blob, ctx.creation_hash, ctx.creation_hash_len); + blob += ctx.creation_hash_len; + } + if (ctx.creation_tk_len) { + memcpy(blob, ctx.creation_tk, ctx.creation_tk_len); + blob += ctx.creation_tk_len; + } + + /* + * Copy the buffer back into the payload blob since the creation + * info will be used after loading. + */ + payload->blob_len = blob - buf; + memcpy(payload->blob, buf, payload->blob_len); + if (ctx.creation_data_len) { + payload->creation = payload->blob + ctx.priv_len + ctx.pub_len; + payload->creation_len = ctx.creation_data_len; + payload->creation_hash = payload->creation + ctx.creation_data_len; + payload->creation_hash_len = ctx.creation_hash_len; + payload->tk = payload->creation_hash + + payload->creation_hash_len; + + payload->tk_len = ctx.creation_tk_len; + } + + kfree(buf); return 0; } @@ -185,6 +305,42 @@ int tpm2_key_priv(void *context, size_t hdrlen, return 0; } +int tpm2_key_creation_data(void *context, size_t hdrlen, + unsigned char tag, + const void *value, size_t vlen) +{ + struct tpm2_key_context *ctx = context; + + ctx->creation_data = value; + ctx->creation_data_len = vlen; + + return 0; +} + +int tpm2_key_creation_hash(void *context, size_t hdrlen, + unsigned char tag, + const void *value, size_t vlen) +{ + struct tpm2_key_context *ctx = context; + + ctx->creation_hash = value; + ctx->creation_hash_len = vlen; + + return 0; +} + +int tpm2_key_creation_tk(void *context, size_t hdrlen, + unsigned char tag, + const void *value, size_t vlen) +{ + struct tpm2_key_context *ctx = context; + + ctx->creation_tk = value; + ctx->creation_tk_len = vlen; + + return 0; +} + /** * tpm_buf_append_auth() - append TPMS_AUTH_COMMAND to the buffer. * @@ -229,6 +385,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip, struct trusted_key_options *options) { int blob_len = 0; + unsigned int offset; struct tpm_buf buf; u32 hash; u32 flags; @@ -317,13 +474,14 @@ int tpm2_seal_trusted(struct tpm_chip *chip, rc = -E2BIG; goto out; } - if (tpm_buf_length(&buf) < TPM_HEADER_SIZE + 4 + blob_len) { + offset = TPM_HEADER_SIZE + 4; + if (tpm_buf_length(&buf) < offset + blob_len) { rc = -EFAULT; goto out; } blob_len = tpm2_key_encode(payload, options, - &buf.data[TPM_HEADER_SIZE + 4], + &buf.data[offset], blob_len); out: @@ -370,13 +528,11 @@ static int tpm2_load_cmd(struct tpm_chip *chip, int rc; u32 attrs; - rc = tpm2_key_decode(payload, options, &blob); - if (rc) { - /* old form */ - blob = payload->blob; + rc = tpm2_key_decode(payload, options); + if (rc) payload->old_format = 1; - } + blob = payload->blob; /* new format carries keyhandle but old format doesn't */ if (!options->keyhandle) return -EINVAL; @@ -433,8 +589,6 @@ static int tpm2_load_cmd(struct tpm_chip *chip, (__be32 *) &buf.data[TPM_HEADER_SIZE]); out: - if (blob != payload->blob) - kfree(blob); tpm_buf_destroy(&buf); if (rc > 0) From patchwork Tue Aug 23 22:25:20 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Evan Green X-Patchwork-Id: 12952681 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 B9994C32793 for ; Tue, 23 Aug 2022 22:26:55 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234033AbiHWW0y (ORCPT ); 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Tue, 23 Aug 2022 15:26:08 -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, Matthew Garrett , Matthew Garrett , Evan Green , David Howells , James Morris , Paul Moore , "Serge E. Hallyn" , keyrings@vger.kernel.org, linux-doc@vger.kernel.org, linux-security-module@vger.kernel.org Subject: [PATCH v2 04/10] security: keys: trusted: Allow storage of PCR values in creation data Date: Tue, 23 Aug 2022 15:25:20 -0700 Message-Id: <20220823152108.v2.4.I32591db064b6cdc91850d777f363c9d05c985b39@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 From: Matthew Garrett When TPMs generate keys, they can also generate some information describing the state of the PCRs at creation time. This data can then later be certified by the TPM, allowing verification of the PCR values. This allows us to determine the state of the system at the time a key was generated. Add an additional argument to the trusted key creation options, allowing the user to provide the set of PCRs that should have their values incorporated into the creation data. From: Matthew Garrett Signed-off-by: Matthew Garrett Signed-off-by: Evan Green --- Matthew's original version of this patch is at: https://patchwork.kernel.org/patch/12096503/ (no changes since v1) .../security/keys/trusted-encrypted.rst | 4 +++ include/keys/trusted-type.h | 1 + security/keys/trusted-keys/trusted_tpm1.c | 9 +++++++ security/keys/trusted-keys/trusted_tpm2.c | 25 +++++++++++++++++-- 4 files changed, 37 insertions(+), 2 deletions(-) diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst index 0bfb4c33974890..dc9e11bb4824da 100644 --- a/Documentation/security/keys/trusted-encrypted.rst +++ b/Documentation/security/keys/trusted-encrypted.rst @@ -199,6 +199,10 @@ Usage:: policyhandle= handle to an authorization policy session that defines the same policy and with the same hash algorithm as was used to seal the key. + creationpcrs= hex integer representing the set of PCR values to be + included in the PCR creation data. The bit corresponding + to each PCR should be 1 to be included, 0 to be ignored. + TPM2 only. "keyctl print" returns an ascii hex copy of the sealed key, which is in standard TPM_STORED_DATA format. The key length for new keys are always in bytes. diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h index 209086fed240a5..8523d41507b2a4 100644 --- a/include/keys/trusted-type.h +++ b/include/keys/trusted-type.h @@ -54,6 +54,7 @@ struct trusted_key_options { uint32_t policydigest_len; unsigned char policydigest[MAX_DIGEST_SIZE]; uint32_t policyhandle; + uint32_t creation_pcrs; }; struct trusted_key_ops { diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c index aa108bea6739b3..2975827c01bec0 100644 --- a/security/keys/trusted-keys/trusted_tpm1.c +++ b/security/keys/trusted-keys/trusted_tpm1.c @@ -713,6 +713,7 @@ enum { Opt_hash, Opt_policydigest, Opt_policyhandle, + Opt_creationpcrs, }; static const match_table_t key_tokens = { @@ -725,6 +726,7 @@ static const match_table_t key_tokens = { {Opt_hash, "hash=%s"}, {Opt_policydigest, "policydigest=%s"}, {Opt_policyhandle, "policyhandle=%s"}, + {Opt_creationpcrs, "creationpcrs=%s"}, {Opt_err, NULL} }; @@ -858,6 +860,13 @@ static int getoptions(char *c, struct trusted_key_payload *pay, return -EINVAL; opt->policyhandle = handle; break; + case Opt_creationpcrs: + if (!tpm2) + return -EINVAL; + res = kstrtoint(args[0].from, 16, &opt->creation_pcrs); + if (res < 0) + return -EINVAL; + break; default: return -EINVAL; } diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c index 1f166d4fa307a9..1d1470b880ca01 100644 --- a/security/keys/trusted-keys/trusted_tpm2.c +++ b/security/keys/trusted-keys/trusted_tpm2.c @@ -389,7 +389,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip, struct tpm_buf buf; u32 hash; u32 flags; - int i; + int i, j; int rc; for (i = 0; i < ARRAY_SIZE(tpm2_hash_map); i++) { @@ -458,7 +458,28 @@ int tpm2_seal_trusted(struct tpm_chip *chip, tpm_buf_append_u16(&buf, 0); /* creation PCR */ - tpm_buf_append_u32(&buf, 0); + if (options->creation_pcrs) { + /* One bank */ + tpm_buf_append_u32(&buf, 1); + /* Which bank to use */ + tpm_buf_append_u16(&buf, hash); + /* Length of the PCR bitmask */ + tpm_buf_append_u8(&buf, 3); + /* PCR bitmask */ + for (i = 0; i < 3; i++) { + char tmp = 0; + + for (j = 0; j < 8; j++) { + char bit = (i * 8) + j; + + if (options->creation_pcrs & (1 << bit)) + tmp |= (1 << j); + } + tpm_buf_append_u8(&buf, tmp); + } + } else { + tpm_buf_append_u32(&buf, 0); + } if (buf.flags & TPM_BUF_OVERFLOW) { rc = -E2BIG; From patchwork Tue Aug 23 22:25:21 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Evan Green X-Patchwork-Id: 12952682 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 7C1B2C32772 for ; Tue, 23 Aug 2022 22:26:59 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234231AbiHWW05 (ORCPT ); Tue, 23 Aug 2022 18:26:57 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52680 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233715AbiHWW0U (ORCPT ); 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Hallyn" , axelj , keyrings@vger.kernel.org, linux-security-module@vger.kernel.org Subject: [PATCH v2 05/10] security: keys: trusted: Verify creation data Date: Tue, 23 Aug 2022 15:25:21 -0700 Message-Id: <20220823152108.v2.5.I6cdb522cb5ea28fcd1e35b4cd92cbd067f99269a@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 If a loaded key contains creation data, ask the TPM to verify that creation data. This allows users like encrypted hibernate to know that the loaded and parsed creation data has not been tampered with. Partially-sourced-from: Matthew Garrett Signed-off-by: Evan Green --- Source material for this change is at: https://patchwork.kernel.org/project/linux-pm/patch/20210220013255.1083202-9-matthewgarrett@google.com/ Changes in v2: - Adjust hash len by 2 due to new ASN.1 storage, and add underflow check. include/linux/tpm.h | 1 + security/keys/trusted-keys/trusted_tpm2.c | 77 ++++++++++++++++++++++- 2 files changed, 77 insertions(+), 1 deletion(-) diff --git a/include/linux/tpm.h b/include/linux/tpm.h index 8320cbac6f4009..438f8bc0a50582 100644 --- a/include/linux/tpm.h +++ b/include/linux/tpm.h @@ -224,6 +224,7 @@ enum tpm2_command_codes { TPM2_CC_SELF_TEST = 0x0143, TPM2_CC_STARTUP = 0x0144, TPM2_CC_SHUTDOWN = 0x0145, + TPM2_CC_CERTIFYCREATION = 0x014A, TPM2_CC_NV_READ = 0x014E, TPM2_CC_CREATE = 0x0153, TPM2_CC_LOAD = 0x0157, diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c index 1d1470b880ca01..f81c6578c7f783 100644 --- a/security/keys/trusted-keys/trusted_tpm2.c +++ b/security/keys/trusted-keys/trusted_tpm2.c @@ -691,6 +691,74 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip, return rc; } +/** + * tpm2_certify_creation() - execute a TPM2_CertifyCreation command + * + * @chip: TPM chip to use + * @payload: the key data in clear and encrypted form + * @blob_handle: the loaded TPM handle of the key + * + * Return: 0 on success + * -EINVAL on tpm error status + * < 0 error from tpm_send or tpm_buf_init + */ +static int tpm2_certify_creation(struct tpm_chip *chip, + struct trusted_key_payload *payload, + u32 blob_handle) +{ + struct tpm_header *head; + struct tpm_buf buf; + int rc; + + rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CERTIFYCREATION); + if (rc) + return rc; + + /* Use TPM_RH_NULL for signHandle */ + tpm_buf_append_u32(&buf, 0x40000007); + + /* Object handle */ + tpm_buf_append_u32(&buf, blob_handle); + + /* Auth */ + tpm_buf_append_u32(&buf, 9); + tpm_buf_append_u32(&buf, TPM2_RS_PW); + tpm_buf_append_u16(&buf, 0); + tpm_buf_append_u8(&buf, 0); + tpm_buf_append_u16(&buf, 0); + + /* Qualifying data */ + tpm_buf_append_u16(&buf, 0); + + /* Creation data hash */ + if (payload->creation_hash_len < 2) { + rc = -EINVAL; + goto out; + } + + tpm_buf_append_u16(&buf, payload->creation_hash_len - 2); + tpm_buf_append(&buf, payload->creation_hash + 2, + payload->creation_hash_len - 2); + + /* signature scheme */ + tpm_buf_append_u16(&buf, TPM_ALG_NULL); + + /* creation ticket */ + tpm_buf_append(&buf, payload->tk, payload->tk_len); + + rc = tpm_transmit_cmd(chip, &buf, 6, "certifying creation data"); + if (rc) + goto out; + + head = (struct tpm_header *)buf.data; + + if (head->return_code != 0) + rc = -EINVAL; +out: + tpm_buf_destroy(&buf); + return rc; +} + /** * tpm2_unseal_trusted() - unseal the payload of a trusted key * @@ -716,8 +784,15 @@ int tpm2_unseal_trusted(struct tpm_chip *chip, goto out; rc = tpm2_unseal_cmd(chip, payload, options, blob_handle); - tpm2_flush_context(chip, blob_handle); + if (rc) + goto flush; + + if (payload->creation_len) + rc = tpm2_certify_creation(chip, payload, blob_handle); + +flush: + tpm2_flush_context(chip, blob_handle); out: tpm_put_ops(chip); From patchwork Tue Aug 23 22:25:22 2022 Content-Type: text/plain; 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Tue, 23 Aug 2022 15:26:15 -0700 (PDT) Received: from evgreen-glaptop.lan ([98.45.66.167]) by smtp.gmail.com with ESMTPSA id f76-20020a62384f000000b0052f20d70845sm11256292pfa.150.2022.08.23.15.26.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Aug 2022 15:26:15 -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 06/10] PM: hibernate: Add kernel-based encryption Date: Tue, 23 Aug 2022 15:25:22 -0700 Message-Id: <20220823152108.v2.6.Ifff11e11797a1bde0297577ecb2f7ebb3f9e2b04@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 Enabling the kernel to be able to do encryption and integrity checks on the hibernate image prevents a malicious userspace from escalating to kernel execution via hibernation resume. As a first step toward this, add the scaffolding needed for the kernel to do AEAD encryption on the hibernate image, giving us both secrecy and integrity. We currently hardwire the encryption to be gcm(aes) in 16-page chunks. This strikes a balance between minimizing the authentication tag overhead on storage, and keeping a modest sized staging buffer. With this chunk size, we'd generate 2MB of authentication tag data on an 8GB hiberation image. The encryption currently sits on top of the core snapshot functionality, wired up only if requested in the uswsusp path. This could potentially be lowered into the common snapshot code given a mechanism to stitch the key contents into the image itself. To avoid forcing usermode to deal with sequencing the auth tags in with the data, we stitch the auth tags in to the snapshot after each chunk of pages. This complicates the read and write functions, as we roll through the flow of (for read) 1) fill the staging buffer with encrypted data, 2) feed the data pages out to user mode, 3) feed the tag out to user mode. To avoid having each syscall return a small and variable amount of data, the encrypted versions of read and write operate in a loop, allowing an arbitrary amount of data through per syscall. One alternative that would simplify things here would be a streaming interface to AEAD. Then we could just stream the entire hibernate image through directly, and handle a single tag at the end. However there is a school of thought that suggests a streaming interface to AEAD represents a loaded footgun, as it tempts the caller to act on the decrypted but not yet verified data, defeating the purpose of AEAD. With this change alone, we don't actually protect ourselves from malicious userspace at all, since we kindly hand the key in plaintext to usermode. In later changes, we'll seal the key with the TPM before handing it back to usermode, so they can't decrypt or tamper with the key themselves. Signed-off-by: Evan Green --- (no changes since v1) Documentation/power/userland-swsusp.rst | 8 + include/uapi/linux/suspend_ioctls.h | 15 +- kernel/power/Kconfig | 13 + kernel/power/Makefile | 1 + kernel/power/snapenc.c | 491 ++++++++++++++++++++++++ kernel/power/user.c | 40 +- kernel/power/user.h | 101 +++++ 7 files changed, 657 insertions(+), 12 deletions(-) create mode 100644 kernel/power/snapenc.c create mode 100644 kernel/power/user.h diff --git a/Documentation/power/userland-swsusp.rst b/Documentation/power/userland-swsusp.rst index 1cf62d80a9ca10..f759915a78ce98 100644 --- a/Documentation/power/userland-swsusp.rst +++ b/Documentation/power/userland-swsusp.rst @@ -115,6 +115,14 @@ SNAPSHOT_S2RAM to resume the system from RAM if there's enough battery power or restore its state on the basis of the saved suspend image otherwise) +SNAPSHOT_ENABLE_ENCRYPTION + Enables encryption of the hibernate image within the kernel. Upon suspend + (ie when the snapshot device was opened for reading), returns a blob + representing the random encryption key the kernel created to encrypt the + hibernate image with. Upon resume (ie when the snapshot device was opened + for writing), receives a blob from usermode containing the key material + previously returned during hibernate. + The device's read() operation can be used to transfer the snapshot image from the kernel. It has the following limitations: diff --git a/include/uapi/linux/suspend_ioctls.h b/include/uapi/linux/suspend_ioctls.h index bcce04e21c0dce..b73026ef824bb9 100644 --- a/include/uapi/linux/suspend_ioctls.h +++ b/include/uapi/linux/suspend_ioctls.h @@ -13,6 +13,18 @@ struct resume_swap_area { __u32 dev; } __attribute__((packed)); +#define USWSUSP_KEY_NONCE_SIZE 16 + +/* + * This structure is used to pass the kernel's hibernate encryption key in + * either direction. + */ +struct uswsusp_key_blob { + __u32 blob_len; + __u8 blob[512]; + __u8 nonce[USWSUSP_KEY_NONCE_SIZE]; +} __attribute__((packed)); + #define SNAPSHOT_IOC_MAGIC '3' #define SNAPSHOT_FREEZE _IO(SNAPSHOT_IOC_MAGIC, 1) #define SNAPSHOT_UNFREEZE _IO(SNAPSHOT_IOC_MAGIC, 2) @@ -29,6 +41,7 @@ struct resume_swap_area { #define SNAPSHOT_PREF_IMAGE_SIZE _IO(SNAPSHOT_IOC_MAGIC, 18) #define SNAPSHOT_AVAIL_SWAP_SIZE _IOR(SNAPSHOT_IOC_MAGIC, 19, __kernel_loff_t) #define SNAPSHOT_ALLOC_SWAP_PAGE _IOR(SNAPSHOT_IOC_MAGIC, 20, __kernel_loff_t) -#define SNAPSHOT_IOC_MAXNR 20 +#define SNAPSHOT_ENABLE_ENCRYPTION _IOWR(SNAPSHOT_IOC_MAGIC, 21, struct uswsusp_key_blob) +#define SNAPSHOT_IOC_MAXNR 21 #endif /* _LINUX_SUSPEND_IOCTLS_H */ diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig index 60a1d3051cc79a..cd574af0b43379 100644 --- a/kernel/power/Kconfig +++ b/kernel/power/Kconfig @@ -92,6 +92,19 @@ config HIBERNATION_SNAPSHOT_DEV If in doubt, say Y. +config ENCRYPTED_HIBERNATION + bool "Encryption support for userspace snapshots" + depends on HIBERNATION_SNAPSHOT_DEV + depends on CRYPTO_AEAD2=y + default n + help + Enable support for kernel-based encryption of hibernation snapshots + created by uswsusp tools. + + Say N if userspace handles the image encryption. + + If in doubt, say N. + config PM_STD_PARTITION string "Default resume partition" depends on HIBERNATION diff --git a/kernel/power/Makefile b/kernel/power/Makefile index 874ad834dc8daf..7be08f2e0e3b68 100644 --- a/kernel/power/Makefile +++ b/kernel/power/Makefile @@ -16,6 +16,7 @@ obj-$(CONFIG_SUSPEND) += suspend.o obj-$(CONFIG_PM_TEST_SUSPEND) += suspend_test.o obj-$(CONFIG_HIBERNATION) += hibernate.o snapshot.o swap.o obj-$(CONFIG_HIBERNATION_SNAPSHOT_DEV) += user.o +obj-$(CONFIG_ENCRYPTED_HIBERNATION) += snapenc.o obj-$(CONFIG_PM_AUTOSLEEP) += autosleep.o obj-$(CONFIG_PM_WAKELOCKS) += wakelock.o diff --git a/kernel/power/snapenc.c b/kernel/power/snapenc.c new file mode 100644 index 00000000000000..cb90692d6ab83a --- /dev/null +++ b/kernel/power/snapenc.c @@ -0,0 +1,491 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* This file provides encryption support for system snapshots. */ + +#include +#include +#include +#include +#include +#include + +#include "power.h" +#include "user.h" + +/* Encrypt more data from the snapshot into the staging area. */ +static int snapshot_encrypt_refill(struct snapshot_data *data) +{ + + u8 nonce[GCM_AES_IV_SIZE]; + int pg_idx; + int res; + struct aead_request *req = data->aead_req; + DECLARE_CRYPTO_WAIT(wait); + size_t total = 0; + + /* + * The first buffer is the associated data, set to the offset to prevent + * attacks that rearrange chunks. + */ + sg_set_buf(&data->sg[0], &data->crypt_total, sizeof(data->crypt_total)); + + /* Load the crypt buffer with snapshot pages. */ + for (pg_idx = 0; pg_idx < CHUNK_SIZE; pg_idx++) { + void *buf = data->crypt_pages[pg_idx]; + + res = snapshot_read_next(&data->handle); + if (res < 0) + return res; + if (res == 0) + break; + + WARN_ON(res != PAGE_SIZE); + + /* + * Copy the page into the staging area. A future optimization + * could potentially skip this copy for lowmem pages. + */ + memcpy(buf, data_of(data->handle), PAGE_SIZE); + sg_set_buf(&data->sg[1 + pg_idx], buf, PAGE_SIZE); + total += PAGE_SIZE; + } + + sg_set_buf(&data->sg[1 + pg_idx], &data->auth_tag, SNAPSHOT_AUTH_TAG_SIZE); + aead_request_set_callback(req, 0, crypto_req_done, &wait); + /* + * Use incrementing nonces for each chunk, since a 64 bit value won't + * roll into re-use for any given hibernate image. + */ + memcpy(&nonce[0], &data->nonce_low, sizeof(data->nonce_low)); + memcpy(&nonce[sizeof(data->nonce_low)], + &data->nonce_high, + sizeof(nonce) - sizeof(data->nonce_low)); + + data->nonce_low += 1; + /* Total does not include AAD or the auth tag. */ + aead_request_set_crypt(req, data->sg, data->sg, total, nonce); + res = crypto_wait_req(crypto_aead_encrypt(req), &wait); + if (res) + return res; + + data->crypt_size = total; + data->crypt_total += total; + return 0; +} + +/* Decrypt data from the staging area and push it to the snapshot. */ +static int snapshot_decrypt_drain(struct snapshot_data *data) +{ + u8 nonce[GCM_AES_IV_SIZE]; + int page_count; + int pg_idx; + int res; + struct aead_request *req = data->aead_req; + DECLARE_CRYPTO_WAIT(wait); + size_t total; + + /* Set up the associated data. */ + sg_set_buf(&data->sg[0], &data->crypt_total, sizeof(data->crypt_total)); + + /* + * Get the number of full pages, which could be short at the end. There + * should also be a tag at the end, so the offset won't be an even page. + */ + page_count = data->crypt_offset >> PAGE_SHIFT; + total = page_count << PAGE_SHIFT; + if ((total == 0) || (total == data->crypt_offset)) + return -EINVAL; + + /* + * Load the sg list with the crypt buffer. Inline decrypt back into the + * staging buffer. A future optimization could decrypt directly into + * lowmem pages. + */ + for (pg_idx = 0; pg_idx < page_count; pg_idx++) + sg_set_buf(&data->sg[1 + pg_idx], data->crypt_pages[pg_idx], PAGE_SIZE); + + /* + * It's possible this is the final decrypt, and there are fewer than + * CHUNK_SIZE pages. If this is the case we would have just written the + * auth tag into the first few bytes of a new page. Copy to the tag if + * so. + */ + if ((page_count < CHUNK_SIZE) && + (data->crypt_offset - total) == sizeof(data->auth_tag)) { + + memcpy(data->auth_tag, + data->crypt_pages[pg_idx], + sizeof(data->auth_tag)); + + } else if (data->crypt_offset != + ((CHUNK_SIZE << PAGE_SHIFT) + SNAPSHOT_AUTH_TAG_SIZE)) { + + return -EINVAL; + } + + sg_set_buf(&data->sg[1 + pg_idx], &data->auth_tag, SNAPSHOT_AUTH_TAG_SIZE); + aead_request_set_callback(req, 0, crypto_req_done, &wait); + memcpy(&nonce[0], &data->nonce_low, sizeof(data->nonce_low)); + memcpy(&nonce[sizeof(data->nonce_low)], + &data->nonce_high, + sizeof(nonce) - sizeof(data->nonce_low)); + + data->nonce_low += 1; + aead_request_set_crypt(req, data->sg, data->sg, total + SNAPSHOT_AUTH_TAG_SIZE, nonce); + res = crypto_wait_req(crypto_aead_decrypt(req), &wait); + if (res) + return res; + + data->crypt_size = 0; + data->crypt_offset = 0; + + /* Push the decrypted pages further down the stack. */ + total = 0; + for (pg_idx = 0; pg_idx < page_count; pg_idx++) { + void *buf = data->crypt_pages[pg_idx]; + + res = snapshot_write_next(&data->handle); + if (res < 0) + return res; + if (res == 0) + break; + + if (!data_of(data->handle)) + return -EINVAL; + + WARN_ON(res != PAGE_SIZE); + + /* + * Copy the page into the staging area. A future optimization + * could potentially skip this copy for lowmem pages. + */ + memcpy(data_of(data->handle), buf, PAGE_SIZE); + total += PAGE_SIZE; + } + + data->crypt_total += total; + return 0; +} + +static ssize_t snapshot_read_next_encrypted(struct snapshot_data *data, + void **buf) +{ + size_t tag_off; + + /* Refill the encrypted buffer if it's empty. */ + if ((data->crypt_size == 0) || + (data->crypt_offset >= + (data->crypt_size + SNAPSHOT_AUTH_TAG_SIZE))) { + + int rc; + + data->crypt_size = 0; + data->crypt_offset = 0; + rc = snapshot_encrypt_refill(data); + if (rc < 0) + return rc; + } + + /* Return data pages if the offset is in that region. */ + if (data->crypt_offset < data->crypt_size) { + size_t pg_idx = data->crypt_offset >> PAGE_SHIFT; + size_t pg_off = data->crypt_offset & (PAGE_SIZE - 1); + *buf = data->crypt_pages[pg_idx] + pg_off; + return PAGE_SIZE - pg_off; + } + + /* Use offsets just beyond the size to return the tag. */ + tag_off = data->crypt_offset - data->crypt_size; + if (tag_off > SNAPSHOT_AUTH_TAG_SIZE) + tag_off = SNAPSHOT_AUTH_TAG_SIZE; + + *buf = data->auth_tag + tag_off; + return SNAPSHOT_AUTH_TAG_SIZE - tag_off; +} + +static ssize_t snapshot_write_next_encrypted(struct snapshot_data *data, + void **buf) +{ + size_t tag_off; + + /* Return data pages if the offset is in that region. */ + if (data->crypt_offset < (PAGE_SIZE * CHUNK_SIZE)) { + size_t pg_idx = data->crypt_offset >> PAGE_SHIFT; + size_t pg_off = data->crypt_offset & (PAGE_SIZE - 1); + *buf = data->crypt_pages[pg_idx] + pg_off; + return PAGE_SIZE - pg_off; + } + + /* Use offsets just beyond the size to return the tag. */ + tag_off = data->crypt_offset - (PAGE_SIZE * CHUNK_SIZE); + if (tag_off > SNAPSHOT_AUTH_TAG_SIZE) + tag_off = SNAPSHOT_AUTH_TAG_SIZE; + + *buf = data->auth_tag + tag_off; + return SNAPSHOT_AUTH_TAG_SIZE - tag_off; +} + +ssize_t snapshot_read_encrypted(struct snapshot_data *data, + char __user *buf, size_t count, loff_t *offp) +{ + ssize_t total = 0; + + /* Loop getting buffers of varying sizes and copying to userspace. */ + while (count) { + size_t copy_size; + size_t not_done; + void *src; + ssize_t src_size = snapshot_read_next_encrypted(data, &src); + + if (src_size <= 0) { + if (total == 0) + return src_size; + + break; + } + + copy_size = min(count, (size_t)src_size); + not_done = copy_to_user(buf + total, src, copy_size); + copy_size -= not_done; + total += copy_size; + count -= copy_size; + data->crypt_offset += copy_size; + if (copy_size == 0) { + if (total == 0) + return -EFAULT; + + break; + } + } + + *offp += total; + return total; +} + +ssize_t snapshot_write_encrypted(struct snapshot_data *data, + const char __user *buf, size_t count, loff_t *offp) +{ + ssize_t total = 0; + + /* Loop getting buffers of varying sizes and copying from. */ + while (count) { + size_t copy_size; + size_t not_done; + void *dst; + ssize_t dst_size = snapshot_write_next_encrypted(data, &dst); + + if (dst_size <= 0) { + if (total == 0) + return dst_size; + + break; + } + + copy_size = min(count, (size_t)dst_size); + not_done = copy_from_user(dst, buf + total, copy_size); + copy_size -= not_done; + total += copy_size; + count -= copy_size; + data->crypt_offset += copy_size; + if (copy_size == 0) { + if (total == 0) + return -EFAULT; + + break; + } + + /* Drain the encrypted buffer if it's full. */ + if ((data->crypt_offset >= + ((PAGE_SIZE * CHUNK_SIZE) + SNAPSHOT_AUTH_TAG_SIZE))) { + + int rc; + + rc = snapshot_decrypt_drain(data); + if (rc < 0) + return rc; + } + } + + *offp += total; + return total; +} + +void snapshot_teardown_encryption(struct snapshot_data *data) +{ + int i; + + if (data->aead_req) { + aead_request_free(data->aead_req); + data->aead_req = NULL; + } + + if (data->aead_tfm) { + crypto_free_aead(data->aead_tfm); + data->aead_tfm = NULL; + } + + for (i = 0; i < CHUNK_SIZE; i++) { + if (data->crypt_pages[i]) { + free_page((unsigned long)data->crypt_pages[i]); + data->crypt_pages[i] = NULL; + } + } +} + +static int snapshot_setup_encryption_common(struct snapshot_data *data) +{ + int i, rc; + + data->crypt_total = 0; + data->crypt_offset = 0; + data->crypt_size = 0; + memset(data->crypt_pages, 0, sizeof(data->crypt_pages)); + /* This only works once per hibernate. */ + if (data->aead_tfm) + return -EINVAL; + + /* Set up the encryption transform */ + data->aead_tfm = crypto_alloc_aead("gcm(aes)", 0, 0); + if (IS_ERR(data->aead_tfm)) { + rc = PTR_ERR(data->aead_tfm); + data->aead_tfm = NULL; + return rc; + } + + rc = -ENOMEM; + data->aead_req = aead_request_alloc(data->aead_tfm, GFP_KERNEL); + if (data->aead_req == NULL) + goto setup_fail; + + /* Allocate the staging area */ + for (i = 0; i < CHUNK_SIZE; i++) { + data->crypt_pages[i] = (void *)__get_free_page(GFP_ATOMIC); + if (data->crypt_pages[i] == NULL) + goto setup_fail; + } + + sg_init_table(data->sg, CHUNK_SIZE + 2); + + /* + * The associated data will be the offset so that blocks can't be + * rearranged. + */ + aead_request_set_ad(data->aead_req, sizeof(data->crypt_total)); + rc = crypto_aead_setauthsize(data->aead_tfm, SNAPSHOT_AUTH_TAG_SIZE); + if (rc) + goto setup_fail; + + return 0; + +setup_fail: + snapshot_teardown_encryption(data); + return rc; +} + +int snapshot_get_encryption_key(struct snapshot_data *data, + struct uswsusp_key_blob __user *key) +{ + u8 aead_key[SNAPSHOT_ENCRYPTION_KEY_SIZE]; + u8 nonce[USWSUSP_KEY_NONCE_SIZE]; + int rc; + /* Don't pull a random key from a world that can be reset. */ + if (data->ready) + return -EPIPE; + + rc = snapshot_setup_encryption_common(data); + if (rc) + return rc; + + /* Build a random starting nonce. */ + 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)); + 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); + if (rc) + goto fail; + + rc = copy_to_user(&key->blob, &aead_key, sizeof(aead_key)); + if (rc) + goto fail; + + rc = copy_to_user(&key->nonce, &nonce, sizeof(nonce)); + if (rc) + goto fail; + + return 0; + +fail: + snapshot_teardown_encryption(data); + return rc; +} + +int snapshot_set_encryption_key(struct snapshot_data *data, + struct uswsusp_key_blob __user *key) +{ + struct uswsusp_key_blob blob; + int rc; + + /* It's too late if data's been pushed in. */ + if (data->handle.cur) + return -EPIPE; + + rc = snapshot_setup_encryption_common(data); + if (rc) + return rc; + + /* Load the key from user mode. */ + rc = copy_from_user(&blob, key, sizeof(struct uswsusp_key_blob)); + if (rc) + goto crypto_setup_fail; + + if (blob.blob_len != sizeof(struct uswsusp_key_blob)) { + rc = -EINVAL; + goto crypto_setup_fail; + } + + rc = crypto_aead_setkey(data->aead_tfm, + blob.blob, + SNAPSHOT_ENCRYPTION_KEY_SIZE); + + if (rc) + goto crypto_setup_fail; + + /* Load the starting nonce. */ + memcpy(&data->nonce_low, &blob.nonce[0], sizeof(data->nonce_low)); + memcpy(&data->nonce_high, &blob.nonce[8], sizeof(data->nonce_high)); + return 0; + +crypto_setup_fail: + snapshot_teardown_encryption(data); + return rc; +} + +loff_t snapshot_get_encrypted_image_size(loff_t raw_size) +{ + loff_t pages = raw_size >> PAGE_SHIFT; + loff_t chunks = (pages + (CHUNK_SIZE - 1)) / CHUNK_SIZE; + /* + * The encrypted size is the normal size, plus a stitched in + * authentication tag for every chunk of pages. + */ + return raw_size + (chunks * SNAPSHOT_AUTH_TAG_SIZE); +} + +int snapshot_finalize_decrypted_image(struct snapshot_data *data) +{ + int rc; + + if (data->crypt_offset != 0) { + rc = snapshot_decrypt_drain(data); + if (rc) + return rc; + } + + return 0; +} diff --git a/kernel/power/user.c b/kernel/power/user.c index d43c2aa583b26b..348e55f623b7e1 100644 --- a/kernel/power/user.c +++ b/kernel/power/user.c @@ -25,19 +25,10 @@ #include #include "power.h" +#include "user.h" static bool need_wait; - -static struct snapshot_data { - struct snapshot_handle handle; - int swap; - int mode; - bool frozen; - bool ready; - bool platform_support; - bool free_bitmaps; - dev_t dev; -} snapshot_state; +struct snapshot_data snapshot_state; int is_hibernate_resume_dev(dev_t dev) { @@ -120,6 +111,7 @@ static int snapshot_release(struct inode *inode, struct file *filp) } else if (data->free_bitmaps) { free_basic_memory_bitmaps(); } + snapshot_teardown_encryption(data); pm_notifier_call_chain(data->mode == O_RDONLY ? PM_POST_HIBERNATION : PM_POST_RESTORE); hibernate_release(); @@ -143,6 +135,12 @@ static ssize_t snapshot_read(struct file *filp, char __user *buf, res = -ENODATA; goto Unlock; } + + if (snapshot_encryption_enabled(data)) { + res = snapshot_read_encrypted(data, buf, count, offp); + goto Unlock; + } + if (!pg_offp) { /* on page boundary? */ res = snapshot_read_next(&data->handle); if (res <= 0) @@ -178,6 +176,11 @@ static ssize_t snapshot_write(struct file *filp, const char __user *buf, data = filp->private_data; + if (snapshot_encryption_enabled(data)) { + res = snapshot_write_encrypted(data, buf, count, offp); + goto unlock; + } + if (!pg_offp) { res = snapshot_write_next(&data->handle); if (res <= 0) @@ -313,6 +316,12 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd, break; case SNAPSHOT_ATOMIC_RESTORE: + if (snapshot_encryption_enabled(data)) { + error = snapshot_finalize_decrypted_image(data); + if (error) + break; + } + snapshot_write_finalize(&data->handle); if (data->mode != O_WRONLY || !data->frozen || !snapshot_image_loaded(&data->handle)) { @@ -348,6 +357,8 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd, } size = snapshot_get_image_size(); size <<= PAGE_SHIFT; + if (snapshot_encryption_enabled(data)) + size = snapshot_get_encrypted_image_size(size); error = put_user(size, (loff_t __user *)arg); break; @@ -405,6 +416,13 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd, error = snapshot_set_swap_area(data, (void __user *)arg); break; + case SNAPSHOT_ENABLE_ENCRYPTION: + if (data->mode == O_RDONLY) + error = snapshot_get_encryption_key(data, (void __user *)arg); + else + error = snapshot_set_encryption_key(data, (void __user *)arg); + break; + default: error = -ENOTTY; diff --git a/kernel/power/user.h b/kernel/power/user.h new file mode 100644 index 00000000000000..6823e2eba7ec53 --- /dev/null +++ b/kernel/power/user.h @@ -0,0 +1,101 @@ +/* SPDX-License-Identifier: GPL-2.0 */ + +#include +#include +#include + +#define SNAPSHOT_ENCRYPTION_KEY_SIZE AES_KEYSIZE_128 +#define SNAPSHOT_AUTH_TAG_SIZE 16 + +/* Define the number of pages in a single AEAD encryption chunk. */ +#define CHUNK_SIZE 16 + +struct snapshot_data { + struct snapshot_handle handle; + int swap; + int mode; + bool frozen; + bool ready; + bool platform_support; + bool free_bitmaps; + dev_t dev; + +#if defined(CONFIG_ENCRYPTED_HIBERNATION) + struct crypto_aead *aead_tfm; + struct aead_request *aead_req; + void *crypt_pages[CHUNK_SIZE]; + u8 auth_tag[SNAPSHOT_AUTH_TAG_SIZE]; + struct scatterlist sg[CHUNK_SIZE + 2]; /* Add room for AD and auth tag. */ + size_t crypt_offset; + size_t crypt_size; + uint64_t crypt_total; + uint64_t nonce_low; + uint64_t nonce_high; +#endif + +}; + +extern struct snapshot_data snapshot_state; + +/* kernel/power/swapenc.c routines */ +#if defined(CONFIG_ENCRYPTED_HIBERNATION) + +ssize_t snapshot_read_encrypted(struct snapshot_data *data, + char __user *buf, size_t count, loff_t *offp); + +ssize_t snapshot_write_encrypted(struct snapshot_data *data, + const char __user *buf, size_t count, loff_t *offp); + +void snapshot_teardown_encryption(struct snapshot_data *data); +int snapshot_get_encryption_key(struct snapshot_data *data, + struct uswsusp_key_blob __user *key); + +int snapshot_set_encryption_key(struct snapshot_data *data, + struct uswsusp_key_blob __user *key); + +loff_t snapshot_get_encrypted_image_size(loff_t raw_size); + +int snapshot_finalize_decrypted_image(struct snapshot_data *data); + +#define snapshot_encryption_enabled(data) (!!(data)->aead_tfm) + +#else + +ssize_t snapshot_read_encrypted(struct snapshot_data *data, + char __user *buf, size_t count, loff_t *offp) +{ + return -ENOTTY; +} + +ssize_t snapshot_write_encrypted(struct snapshot_data *data, + const char __user *buf, size_t count, loff_t *offp) +{ + return -ENOTTY; +} + +static void snapshot_teardown_encryption(struct snapshot_data *data) {} +static int snapshot_get_encryption_key(struct snapshot_data *data, + struct uswsusp_key_blob __user *key) +{ + return -ENOTTY; +} + +static int snapshot_set_encryption_key(struct snapshot_data *data, + struct uswsusp_key_blob __user *key) +{ + return -ENOTTY; +} + +static loff_t snapshot_get_encrypted_image_size(loff_t raw_size) +{ + return raw_size; +} + +static int snapshot_finalize_decrypted_image(struct snapshot_data *data) +{ + return -ENOTTY; +} + +#define snapshot_encryption_enabled(data) (0) + +#endif From patchwork Tue Aug 23 22:25:23 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Evan Green X-Patchwork-Id: 12952702 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 BD17DC32772 for ; Tue, 23 Aug 2022 22:27:23 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233286AbiHWW1W (ORCPT ); Tue, 23 Aug 2022 18:27:22 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:52840 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233839AbiHWW0d (ORCPT ); Tue, 23 Aug 2022 18:26:33 -0400 Received: from mail-pj1-x1035.google.com (mail-pj1-x1035.google.com [IPv6:2607:f8b0:4864:20::1035]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id E2BF9870A4 for ; 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Tue, 23 Aug 2022 15:26:18 -0700 (PDT) Received: from evgreen-glaptop.lan ([98.45.66.167]) by smtp.gmail.com with ESMTPSA id f76-20020a62384f000000b0052f20d70845sm11256292pfa.150.2022.08.23.15.26.16 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Aug 2022 15:26:18 -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 07/10] PM: hibernate: Use TPM-backed keys to encrypt image Date: Tue, 23 Aug 2022 15:25:23 -0700 Message-Id: <20220823152108.v2.7.Ibd067e73916b9fae268a5824c2dd037416426af8@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 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 --- Matthew's incarnation of this patch is at: https://patchwork.kernel.org/project/linux-pm/patch/20210220013255.1083202-9-matthewgarrett@google.com/ 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 | 2 + kernel/power/snapenc.c | 207 +++++++++++++++++++++++++++++++++++++++-- kernel/power/user.h | 1 + 3 files changed, 201 insertions(+), 9 deletions(-) diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig index cd574af0b43379..ff15361c5d8fad 100644 --- a/kernel/power/Kconfig +++ b/kernel/power/Kconfig @@ -96,6 +96,8 @@ config ENCRYPTED_HIBERNATION bool "Encryption support for userspace snapshots" depends on HIBERNATION_SNAPSHOT_DEV depends on CRYPTO_AEAD2=y + depends on KEYS + depends on TRUSTED_KEYS 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 cb90692d6ab83a..90079f6d4f184b 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) { @@ -313,6 +323,12 @@ void snapshot_teardown_encryption(struct snapshot_data *data) { int i; + 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; @@ -381,11 +397,83 @@ static int snapshot_setup_encryption_common(struct snapshot_data *data) return rc; } +static int snapshot_create_kernel_key(struct snapshot_data *data) +{ + const struct cred *cred = current_cred(); + struct tpm_digest *digests = NULL; + struct tpm_chip *chip; + struct key *key = NULL; + int ret, i; + /* Create a key sealed by the SRK. */ + char *keyinfo = "new\t32\tkeyhandle=0x81000000"; + + chip = tpm_default_chip(); + if (!chip) + return -ENODEV; + + if (!(tpm_is_tpm2(chip))) { + ret = -ENODEV; + goto out_dev; + } + + ret = tpm_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, 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(digests); + tpm_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]; u8 nonce[USWSUSP_KEY_NONCE_SIZE]; + struct trusted_key_payload *payload; int rc; /* Don't pull a random key from a world that can be reset. */ if (data->ready) @@ -399,21 +487,28 @@ 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; @@ -425,10 +520,99 @@ 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) +{ + + const struct cred *cred = current_cred(); + char *keytemplate = "load\t%s\tkeyhandle=0x81000000"; + struct tpm_digest *digests = NULL; + char *blobstring = NULL; + char *keyinfo = NULL; + struct tpm_chip *chip; + struct key *key = NULL; + int i, ret; + + chip = tpm_default_chip(); + if (!chip) + return -ENODEV; + + if (!(tpm_is_tpm2(chip))) { + ret = -ENODEV; + goto out_dev; + } + + ret = tpm_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); + tpm_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. */ @@ -444,13 +628,18 @@ 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 6823e2eba7ec53..591b30bb213349 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 }; From patchwork Tue Aug 23 22:25:24 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Evan Green X-Patchwork-Id: 12952703 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 79305C38142 for ; Tue, 23 Aug 2022 22:27:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S234276AbiHWW1X (ORCPT ); Tue, 23 Aug 2022 18:27:23 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:53282 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S233453AbiHWW0e (ORCPT ); Tue, 23 Aug 2022 18:26:34 -0400 Received: from mail-pl1-x62d.google.com (mail-pl1-x62d.google.com [IPv6:2607:f8b0:4864:20::62d]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 28F4387692 for ; 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Tue, 23 Aug 2022 15:26:21 -0700 (PDT) Received: from evgreen-glaptop.lan ([98.45.66.167]) by smtp.gmail.com with ESMTPSA id f76-20020a62384f000000b0052f20d70845sm11256292pfa.150.2022.08.23.15.26.20 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 23 Aug 2022 15:26:21 -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 08/10] PM: hibernate: Mix user key in encrypted hibernate Date: Tue, 23 Aug 2022 15:25:24 -0700 Message-Id: <20220823152108.v2.8.I87952411cf83f2199ff7a4cc8c828d357b8c8ce3@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 Usermode may have their own data protection requirements when it comes to encrypting the hibernate image. For example, users may want a policy where the hibernate image is protected by a key derived both from platform-level security as well as authentication data (such as a password or PIN). This way, even if the platform is compromised (ie a stolen laptop), sensitive data cannot be exfiltrated via the hibernate image without additional data (like the user's password). The kernel is already doing the encryption, but will be protecting its key with the TPM alone. Allow usermode to mix in key content of their own for the data portion of the hibernate image, so that the image encryption key is determined both by a TPM-backed secret and user-defined data. To mix the user key in, we hash the kernel key followed by the user key, and use the resulting hash as the new key. This allows usermode to mix in its key material without giving it too much control over what key is actually driving the encryption (which might be used to attack the secret kernel key). Limiting this to the data portion allows the kernel to receive the page map and prepare its giant allocation even if this user key is not yet available (ie the user has not yet finished typing in their password). Once the user key becomes available, the data portion can be pushed through to the kernel as well. This enables "preloading" scenarios, where the hibernate image is loaded off of disk while the additional key material (eg password) is being collected. One annoyance of the "preloading" scheme is that hibernate image memory is effectively double-allocated: first by the usermode process pulling encrypted contents off of disk and holding it, and second by the kernel in its giant allocation in prepare_image(). An interesting future optimization would be to allow the kernel to accept and store encrypted page data before the user key is available. This would remove the double allocation problem, as usermode could push the encrypted pages loaded from disk immediately without storing them. The kernel could defer decryption of the data until the user key is available, while still knowing the correct page locations to store the encrypted data in. Signed-off-by: Evan Green --- Changes in v2: - Add missing static on snapshot_encrypted_byte_count() - Fold in only the used kernel key bytes to the user key. - Make the user key length 32 (Eric) - Use CRYPTO_LIB_SHA256 for less boilerplate (Eric) include/uapi/linux/suspend_ioctls.h | 15 ++- kernel/power/Kconfig | 1 + kernel/power/power.h | 1 + kernel/power/snapenc.c | 158 ++++++++++++++++++++++++++-- kernel/power/snapshot.c | 5 + kernel/power/user.c | 4 + kernel/power/user.h | 12 +++ 7 files changed, 185 insertions(+), 11 deletions(-) diff --git a/include/uapi/linux/suspend_ioctls.h b/include/uapi/linux/suspend_ioctls.h index b73026ef824bb9..f93a22eac52dc2 100644 --- a/include/uapi/linux/suspend_ioctls.h +++ b/include/uapi/linux/suspend_ioctls.h @@ -25,6 +25,18 @@ struct uswsusp_key_blob { __u8 nonce[USWSUSP_KEY_NONCE_SIZE]; } __attribute__((packed)); +/* + * Allow user mode to fold in key material for the data portion of the hibernate + * image. + */ +struct uswsusp_user_key { + /* Kernel returns the metadata size. */ + __kernel_loff_t meta_size; + __u32 key_len; + __u8 key[32]; + __u32 pad; +}; + #define SNAPSHOT_IOC_MAGIC '3' #define SNAPSHOT_FREEZE _IO(SNAPSHOT_IOC_MAGIC, 1) #define SNAPSHOT_UNFREEZE _IO(SNAPSHOT_IOC_MAGIC, 2) @@ -42,6 +54,7 @@ struct uswsusp_key_blob { #define SNAPSHOT_AVAIL_SWAP_SIZE _IOR(SNAPSHOT_IOC_MAGIC, 19, __kernel_loff_t) #define SNAPSHOT_ALLOC_SWAP_PAGE _IOR(SNAPSHOT_IOC_MAGIC, 20, __kernel_loff_t) #define SNAPSHOT_ENABLE_ENCRYPTION _IOWR(SNAPSHOT_IOC_MAGIC, 21, struct uswsusp_key_blob) -#define SNAPSHOT_IOC_MAXNR 21 +#define SNAPSHOT_SET_USER_KEY _IOWR(SNAPSHOT_IOC_MAGIC, 22, struct uswsusp_user_key) +#define SNAPSHOT_IOC_MAXNR 22 #endif /* _LINUX_SUSPEND_IOCTLS_H */ diff --git a/kernel/power/Kconfig b/kernel/power/Kconfig index ff15361c5d8fad..6ff14d92454711 100644 --- a/kernel/power/Kconfig +++ b/kernel/power/Kconfig @@ -98,6 +98,7 @@ config ENCRYPTED_HIBERNATION depends on CRYPTO_AEAD2=y depends on KEYS depends on TRUSTED_KEYS + select CRYPTO_LIB_SHA256 default n help Enable support for kernel-based encryption of hibernation snapshots diff --git a/kernel/power/power.h b/kernel/power/power.h index b4f43394320961..5955e5cf692302 100644 --- a/kernel/power/power.h +++ b/kernel/power/power.h @@ -151,6 +151,7 @@ struct snapshot_handle { extern unsigned int snapshot_additional_pages(struct zone *zone); extern unsigned long snapshot_get_image_size(void); +extern unsigned long snapshot_get_meta_page_count(void); extern int snapshot_read_next(struct snapshot_handle *handle); extern int snapshot_write_next(struct snapshot_handle *handle); extern void snapshot_write_finalize(struct snapshot_handle *handle); diff --git a/kernel/power/snapenc.c b/kernel/power/snapenc.c index 90079f6d4f184b..e0b902d2dcf13a 100644 --- a/kernel/power/snapenc.c +++ b/kernel/power/snapenc.c @@ -6,6 +6,7 @@ #include #include #include +#include #include #include #include @@ -21,6 +22,38 @@ static struct tpm_digest known_digest = { .alg_id = TPM_ALG_SHA256, 0xf1, 0x22, 0x38, 0x6c, 0x33, 0xb1, 0x14, 0xb7, 0xec, 0x05, 0x5f, 0x49}}; +/* Derive a key from the kernel and user keys for data encryption. */ +static int snapshot_use_user_key(struct snapshot_data *data) +{ + u8 digest[SHA256_DIGEST_SIZE]; + struct trusted_key_payload *payload = data->key->payload.data[0]; + struct sha256_state sha256_state; + + /* + * Hash the kernel key and the user key together. This folds in the user + * key, but not in a way that gives the user mode predictable control + * over the key bits. + */ + sha256_init(&sha256_state); + sha256_update(&sha256_state, payload->key, SNAPSHOT_ENCRYPTION_KEY_SIZE); + sha256_update(&sha256_state, data->user_key, sizeof(data->user_key)); + sha256_final(&sha256_state, digest); + return crypto_aead_setkey(data->aead_tfm, + digest, + SNAPSHOT_ENCRYPTION_KEY_SIZE); +} + +/* Check to see if it's time to switch to the user key, and do it if so. */ +static int snapshot_check_user_key_switch(struct snapshot_data *data) +{ + if (data->user_key_valid && data->meta_size && + data->crypt_total == data->meta_size) { + return snapshot_use_user_key(data); + } + + return 0; +} + /* Encrypt more data from the snapshot into the staging area. */ static int snapshot_encrypt_refill(struct snapshot_data *data) { @@ -32,6 +65,15 @@ static int snapshot_encrypt_refill(struct snapshot_data *data) DECLARE_CRYPTO_WAIT(wait); size_t total = 0; + if (data->crypt_total == 0) { + data->meta_size = snapshot_get_meta_page_count() << PAGE_SHIFT; + + } else { + res = snapshot_check_user_key_switch(data); + if (res) + return res; + } + /* * The first buffer is the associated data, set to the offset to prevent * attacks that rearrange chunks. @@ -42,6 +84,11 @@ static int snapshot_encrypt_refill(struct snapshot_data *data) for (pg_idx = 0; pg_idx < CHUNK_SIZE; pg_idx++) { void *buf = data->crypt_pages[pg_idx]; + /* Stop at the meta page boundary to potentially switch keys. */ + if (total && + ((data->crypt_total + total) == data->meta_size)) + break; + res = snapshot_read_next(&data->handle); if (res < 0) return res; @@ -114,10 +161,10 @@ static int snapshot_decrypt_drain(struct snapshot_data *data) sg_set_buf(&data->sg[1 + pg_idx], data->crypt_pages[pg_idx], PAGE_SIZE); /* - * It's possible this is the final decrypt, and there are fewer than - * CHUNK_SIZE pages. If this is the case we would have just written the - * auth tag into the first few bytes of a new page. Copy to the tag if - * so. + * It's possible this is the final decrypt, or the final decrypt of the + * meta region, and there are fewer than CHUNK_SIZE pages. If this is + * the case we would have just written the auth tag into the first few + * bytes of a new page. Copy to the tag if so. */ if ((page_count < CHUNK_SIZE) && (data->crypt_offset - total) == sizeof(data->auth_tag)) { @@ -172,7 +219,14 @@ static int snapshot_decrypt_drain(struct snapshot_data *data) total += PAGE_SIZE; } + if (data->crypt_total == 0) + data->meta_size = snapshot_get_meta_page_count() << PAGE_SHIFT; + data->crypt_total += total; + res = snapshot_check_user_key_switch(data); + if (res) + return res; + return 0; } @@ -221,8 +275,26 @@ static ssize_t snapshot_write_next_encrypted(struct snapshot_data *data, if (data->crypt_offset < (PAGE_SIZE * CHUNK_SIZE)) { size_t pg_idx = data->crypt_offset >> PAGE_SHIFT; size_t pg_off = data->crypt_offset & (PAGE_SIZE - 1); + size_t size_avail = PAGE_SIZE; *buf = data->crypt_pages[pg_idx] + pg_off; - return PAGE_SIZE - pg_off; + + /* + * If this is the boundary where the meta pages end, then just + * return enough for the auth tag. + */ + if (data->meta_size && (data->crypt_total < data->meta_size)) { + uint64_t total_done = + data->crypt_total + data->crypt_offset; + + if ((total_done >= data->meta_size) && + (total_done < + (data->meta_size + SNAPSHOT_AUTH_TAG_SIZE))) { + + size_avail = SNAPSHOT_AUTH_TAG_SIZE; + } + } + + return size_avail - pg_off; } /* Use offsets just beyond the size to return the tag. */ @@ -303,9 +375,15 @@ ssize_t snapshot_write_encrypted(struct snapshot_data *data, break; } - /* Drain the encrypted buffer if it's full. */ + /* + * Drain the encrypted buffer if it's full, or if we hit the end + * of the meta pages and need a key change. + */ if ((data->crypt_offset >= - ((PAGE_SIZE * CHUNK_SIZE) + SNAPSHOT_AUTH_TAG_SIZE))) { + ((PAGE_SIZE * CHUNK_SIZE) + SNAPSHOT_AUTH_TAG_SIZE)) || + (data->meta_size && (data->crypt_total < data->meta_size) && + ((data->crypt_total + data->crypt_offset) == + (data->meta_size + SNAPSHOT_AUTH_TAG_SIZE)))) { int rc; @@ -345,6 +423,8 @@ void snapshot_teardown_encryption(struct snapshot_data *data) data->crypt_pages[i] = NULL; } } + + memset(data->user_key, 0, sizeof(data->user_key)); } static int snapshot_setup_encryption_common(struct snapshot_data *data) @@ -354,6 +434,7 @@ static int snapshot_setup_encryption_common(struct snapshot_data *data) data->crypt_total = 0; data->crypt_offset = 0; data->crypt_size = 0; + data->user_key_valid = false; memset(data->crypt_pages, 0, sizeof(data->crypt_pages)); /* This only works once per hibernate. */ if (data->aead_tfm) @@ -655,15 +736,72 @@ int snapshot_set_encryption_key(struct snapshot_data *data, return rc; } -loff_t snapshot_get_encrypted_image_size(loff_t raw_size) +static loff_t snapshot_encrypted_byte_count(loff_t plain_size) { - loff_t pages = raw_size >> PAGE_SHIFT; + loff_t pages = plain_size >> PAGE_SHIFT; loff_t chunks = (pages + (CHUNK_SIZE - 1)) / CHUNK_SIZE; /* * The encrypted size is the normal size, plus a stitched in * authentication tag for every chunk of pages. */ - return raw_size + (chunks * SNAPSHOT_AUTH_TAG_SIZE); + return plain_size + (chunks * SNAPSHOT_AUTH_TAG_SIZE); +} + +static loff_t snapshot_get_meta_data_size(void) +{ + loff_t pages = snapshot_get_meta_page_count(); + + return snapshot_encrypted_byte_count(pages << PAGE_SHIFT); +} + +int snapshot_set_user_key(struct snapshot_data *data, + struct uswsusp_user_key __user *key) +{ + struct uswsusp_user_key user_key; + unsigned int key_len; + int rc; + loff_t size; + + /* + * Return the metadata size, the number of bytes that can be fed in before + * the user data key is needed at resume time. + */ + size = snapshot_get_meta_data_size(); + rc = put_user(size, &key->meta_size); + if (rc) + return rc; + + rc = copy_from_user(&user_key, key, sizeof(struct uswsusp_user_key)); + if (rc) + return rc; + + key_len = min_t(__u32, user_key.key_len, sizeof(data->user_key)); + if (key_len < 8) + return -EINVAL; + + /* Don't allow it if it's too late. */ + if (data->crypt_total > data->meta_size) + return -EBUSY; + + memset(data->user_key, 0, sizeof(data->user_key)); + memcpy(data->user_key, user_key.key, key_len); + data->user_key_valid = true; + /* Install the key if the user is just under the wire. */ + rc = snapshot_check_user_key_switch(data); + if (rc) + return rc; + + return 0; +} + +loff_t snapshot_get_encrypted_image_size(loff_t raw_size) +{ + loff_t pages = raw_size >> PAGE_SHIFT; + loff_t meta_size; + + pages -= snapshot_get_meta_page_count(); + meta_size = snapshot_get_meta_data_size(); + return snapshot_encrypted_byte_count(pages << PAGE_SHIFT) + meta_size; } int snapshot_finalize_decrypted_image(struct snapshot_data *data) diff --git a/kernel/power/snapshot.c b/kernel/power/snapshot.c index 2a406753af9049..026ee511633bc9 100644 --- a/kernel/power/snapshot.c +++ b/kernel/power/snapshot.c @@ -2083,6 +2083,11 @@ unsigned long snapshot_get_image_size(void) return nr_copy_pages + nr_meta_pages + 1; } +unsigned long snapshot_get_meta_page_count(void) +{ + return nr_meta_pages + 1; +} + static int init_header(struct swsusp_info *info) { memset(info, 0, sizeof(struct swsusp_info)); diff --git a/kernel/power/user.c b/kernel/power/user.c index 348e55f623b7e1..e24fc9bda873a4 100644 --- a/kernel/power/user.c +++ b/kernel/power/user.c @@ -423,6 +423,10 @@ static long snapshot_ioctl(struct file *filp, unsigned int cmd, error = snapshot_set_encryption_key(data, (void __user *)arg); break; + case SNAPSHOT_SET_USER_KEY: + error = snapshot_set_user_key(data, (void __user *)arg); + break; + default: error = -ENOTTY; diff --git a/kernel/power/user.h b/kernel/power/user.h index 591b30bb213349..1b0743b36eee14 100644 --- a/kernel/power/user.h +++ b/kernel/power/user.h @@ -32,6 +32,9 @@ struct snapshot_data { uint64_t nonce_low; uint64_t nonce_high; struct key *key; + u8 user_key[SNAPSHOT_ENCRYPTION_KEY_SIZE]; + bool user_key_valid; + uint64_t meta_size; #endif }; @@ -54,6 +57,9 @@ int snapshot_get_encryption_key(struct snapshot_data *data, int snapshot_set_encryption_key(struct snapshot_data *data, struct uswsusp_key_blob __user *key); +int snapshot_set_user_key(struct snapshot_data *data, + struct uswsusp_user_key __user *key); + loff_t snapshot_get_encrypted_image_size(loff_t raw_size); int snapshot_finalize_decrypted_image(struct snapshot_data *data); @@ -87,6 +93,12 @@ static int snapshot_set_encryption_key(struct snapshot_data *data, return -ENOTTY; } +static int snapshot_set_user_key(struct snapshot_data *data, + struct uswsusp_user_key __user *key) +{ + return -ENOTTY; +} + static loff_t snapshot_get_encrypted_image_size(loff_t raw_size) { return raw_size; 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 ; 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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; From patchwork Tue Aug 23 22:25:26 2022 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Evan Green X-Patchwork-Id: 12952705 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 0470AC32793 for ; Tue, 23 Aug 2022 22:27:45 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233231AbiHWW1m (ORCPT ); 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Tue, 23 Aug 2022 15:26:27 -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 , Hao Wu , Len Brown , Matthew Garrett , "Rafael J. Wysocki" , axelj Subject: [PATCH v2 10/10] PM: hibernate: seal the encryption key with a PCR policy Date: Tue, 23 Aug 2022 15:25:26 -0700 Message-Id: <20220823152108.v2.10.Ifce072ae1ef1ce39bd681fff55af13a054045d9f@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 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 for PCs or 0 for Chrome OS. Sourced-from: Matthew Garrett Signed-off-by: Evan Green Signed-off-by: Matthew Garrett <...> --- The original version of this patch is here: https://patchwork.kernel.org/project/linux-pm/patch/20210220013255.1083202-10-matthewgarrett@google.com/ Changes in v2: - Fix sparse warnings - Fix session type comment (Andrey) - Eliminate extra label in get/create_kernel_key() (Andrey) - Call tpm_try_get_ops() before calling tpm2_flush_context(). include/linux/tpm.h | 4 + kernel/power/snapenc.c | 164 ++++++++++++++++++++++++++++++++++++++++- 2 files changed, 164 insertions(+), 4 deletions(-) diff --git a/include/linux/tpm.h b/include/linux/tpm.h index 438f8bc0a50582..cd520efc515bca 100644 --- a/include/linux/tpm.h +++ b/include/linux/tpm.h @@ -233,18 +233,22 @@ 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/snapenc.c b/kernel/power/snapenc.c index 1f08942450775a..02d25f9500cb7f 100644 --- a/kernel/power/snapenc.c +++ b/kernel/power/snapenc.c @@ -433,6 +433,111 @@ void snapshot_teardown_encryption(struct snapshot_data *data) memset(data->user_key, 0, sizeof(data->user_key)); } +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); + + /* Session type - policy */ + 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(u32) + sizeof(u16) + sizeof(nonce)) { + rc = -EINVAL; + goto out; + } + + *session_handle = be32_to_cpu(*(__be32 *)&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 snapshot_setup_encryption_common(struct snapshot_data *data) { int i, rc; @@ -492,7 +597,12 @@ 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\tcreationpcrs=0x00800000"; + char *keyinfo = NULL; + const char *keytemplate = + "new\t32\tkeyhandle=0x81000000\tcreationpcrs=0x00800000\tpolicydigest=%s"; + char policy[SHA256_DIGEST_SIZE]; + char *policydigest = NULL; + int session_handle = -1; chip = tpm_default_chip(); if (!chip) @@ -524,6 +634,28 @@ static int snapshot_create_kernel_key(struct snapshot_data *data) if (ret != 0) goto out; + policydigest = kmalloc(SHA256_DIGEST_SIZE * 2 + 1, GFP_KERNEL); + if (!policydigest) { + ret = -ENOMEM; + goto out; + } + + ret = tpm_setup_policy(chip, &session_handle); + if (ret != 0) + goto out; + + ret = tpm_policy_get_digest(chip, session_handle, policy); + if (ret != 0) + goto out; + + bin2hex(policydigest, policy, SHA256_DIGEST_SIZE); + policydigest[SHA256_DIGEST_SIZE * 2] = '\0'; + keyinfo = kasprintf(GFP_KERNEL, keytemplate, policydigest); + 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); @@ -548,7 +680,16 @@ static int snapshot_create_kernel_key(struct snapshot_data *data) key_put(key); } + if (session_handle != -1) { + if (tpm_try_get_ops(chip) == 0) { + tpm2_flush_context(chip, session_handle); + tpm_put_ops(chip); + } + } + kfree(digests); + kfree(keyinfo); + kfree(policydigest); tpm_pcr_reset(chip, 23); out_dev: @@ -613,13 +754,14 @@ static int snapshot_load_kernel_key(struct snapshot_data *data, char certhash[SHA256_DIGEST_SIZE]; const struct cred *cred = current_cred(); - char *keytemplate = "load\t%s\tkeyhandle=0x81000000"; + char *keytemplate = "load\t%s\tkeyhandle=0x81000000\tpolicyhandle=0x%x"; struct tpm_digest *digests = NULL; char *blobstring = NULL; char *keyinfo = NULL; struct tpm_chip *chip; struct key *key = NULL; struct trusted_key_payload *payload; + int session_handle = -1; int i, ret; chip = tpm_default_chip(); @@ -652,14 +794,21 @@ static int snapshot_load_kernel_key(struct snapshot_data *data, if (ret != 0) goto out; - blobstring = kmalloc(blob->blob_len * 2, GFP_KERNEL); + ret = tpm_setup_policy(chip, &session_handle); + if (ret != 0) + goto out; + + blobstring = kmalloc(blob->blob_len * 2 + 1, GFP_KERNEL); if (!blobstring) { ret = -ENOMEM; goto out; } bin2hex(blobstring, blob->blob, blob->blob_len); - keyinfo = kasprintf(GFP_KERNEL, keytemplate, blobstring); + blobstring[blob->blob_len * 2] = '\0'; + keyinfo = kasprintf(GFP_KERNEL, keytemplate, blobstring, + session_handle); + if (!keyinfo) { ret = -ENOMEM; goto out; @@ -742,6 +891,13 @@ static int snapshot_load_kernel_key(struct snapshot_data *data, key_put(key); } + if (session_handle != -1) { + if (tpm_try_get_ops(chip) == 0) { + tpm2_flush_context(chip, session_handle); + tpm_put_ops(chip); + } + } + kfree(keyinfo); kfree(blobstring); kfree(digests);