linux-kernel - [PATCH 2/2] efi/libstub: measure EFI LoadOptions

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Message-Id: <20220916081441.1993492-2-ilias.apalodimas@linaro.org>
Date:   Fri, 16 Sep 2022 11:14:35 +0300
From:   Ilias Apalodimas <ilias.apalodimas@...aro.org>
To:     ardb@...nel.org
Cc:     pjones@...hat.com, daniel.kiper@...cle.com,
        James.Bottomley@...senpartnership.com, leif@...iainc.com,
        jroedel@...e.de, Ilias Apalodimas <ilias.apalodimas@...aro.org>,
        Sunil V L <sunilvl@...tanamicro.com>,
        Baskov Evgeniy <baskov@...ras.ru>,
        Palmer Dabbelt <palmer@...osinc.com>,
        linux-efi@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 2/2] efi/libstub: measure EFI LoadOptions

The EFI TCG spec, in §10.2.6 Measuring UEFI Variables and UEFI GPT Data,
is  measuring the entire UEFI_LOAD_OPTION (in PCR5).  As a result boot
variables that point to the same UEFI application but with different
optional data,  will have distinct measurements.

However, PCR5 is used for more than that and there might be a need to use
a PCR with a more limited scope which measures our initramfs and
LoadOptions.

So add a measurement in PCR9 (which we already use for our initrd) and
extend it with the LoadOption measurements

Signed-off-by: Ilias Apalodimas <ilias.apalodimas@...aro.org>
---
 .../firmware/efi/libstub/efi-stub-helper.c    | 21 +++++++++++++++++++
 drivers/firmware/efi/libstub/efistub.h        |  1 +
 2 files changed, 22 insertions(+)

diff --git a/drivers/firmware/efi/libstub/efi-stub-helper.c b/drivers/firmware/efi/libstub/efi-stub-helper.c
index 3ef4867344b9..5b03248527c6 100644
--- a/drivers/firmware/efi/libstub/efi-stub-helper.c
+++ b/drivers/firmware/efi/libstub/efi-stub-helper.c
@@ -370,6 +370,27 @@ char *efi_convert_cmdline(efi_loaded_image_t *image, int *cmd_line_len)
 	int options_bytes = 0, safe_options_bytes = 0;  /* UTF-8 bytes */
 	bool in_quote = false;
 	efi_status_t status;
+	static const struct efi_measured_event load_options_tcg2_event = {
+		{
+			sizeof(load_options_tcg2_event) + sizeof("Load Options"),
+			{
+				sizeof(load_options_tcg2_event.event_data.event_header),
+				EFI_TCG2_EVENT_HEADER_VERSION,
+				9,
+				EV_EVENT_TAG,
+			},
+		},
+		{
+			LOAD_OPTIONS_EVENT_TAG_ID,
+			sizeof("Load Options"),
+		},
+		{ "Load Options" },
+	};
+
+	if (options_chars > 0)
+		efi_measure_tagged_event((unsigned long) options,
+					 (unsigned long) options_chars,
+					 &load_options_tcg2_event);
 
 	efi_apply_loadoptions_quirk((const void **)&options, &options_chars);
 	options_chars /= sizeof(*options);
diff --git a/drivers/firmware/efi/libstub/efistub.h b/drivers/firmware/efi/libstub/efistub.h
index cb7eb5ed9f14..e3605b383964 100644
--- a/drivers/firmware/efi/libstub/efistub.h
+++ b/drivers/firmware/efi/libstub/efistub.h
@@ -741,6 +741,7 @@ union apple_properties_protocol {
 typedef u32 efi_tcg2_event_log_format;
 
 #define INITRD_EVENT_TAG_ID 0x8F3B22ECU
+#define LOAD_OPTIONS_EVENT_TAG_ID 0x8F3B22EDU
 #define EV_EVENT_TAG 0x00000006U
 #define EFI_TCG2_EVENT_HEADER_VERSION	0x1
 
-- 
2.34.1