[SLOF] [PATCH 2/2] tcgbios: Only measure size indicated in UEFI partition table header

[Stefan Berger]

From: Stefan Berger <stefanb at linux.ibm.com>

Remove the reserved byte array from the UEFI_PARTITION_TABLE_HEADER
to avoid measuring zero bytes. Only log and measure the header as
indicated by its size. This size is expected to be exactly the size
of UEFI_PARTITION_TABLE_HEADER (= 92 bytes).

Fixes: 16a1867425ee ("tcgbios: Measure the GPT table")
Signed-off-by: Stefan Berger <stefanb at linux.ibm.com>
---
 lib/libtpm/tcgbios.c     | 19 +++++++++++++++++--
 lib/libtpm/tcgbios_int.h |  1 -
 2 files changed, 17 insertions(+), 3 deletions(-)

diff --git a/lib/libtpm/tcgbios.c b/lib/libtpm/tcgbios.c
index 9a10dbe..8fd404e 100644
--- a/lib/libtpm/tcgbios.c
+++ b/lib/libtpm/tcgbios.c
@@ -1080,6 +1080,9 @@ uint32_t tpm_measure_bcv_mbr(uint32_t bootdrv, const uint8_t *addr,
  */
 void tpm_gpt_set_lba1(const uint8_t *addr, uint32_t length)
 {
+	UEFI_PARTITION_TABLE_HEADER *upth;
+	size_t to_copy;
+
 	if (!tpm_is_working())
 		return;
 
@@ -1090,8 +1093,20 @@ void tpm_gpt_set_lba1(const uint8_t *addr, uint32_t length)
 	if (!uefi_gpt_data)
 		return;
 
-	memcpy(&uefi_gpt_data->EfiPartitionHeader,
-	       addr, MIN(sizeof(uefi_gpt_data->EfiPartitionHeader), length));
+	upth = (UEFI_PARTITION_TABLE_HEADER *)addr;
+
+	/* check whether header.size is part of @addr array */
+	if (length < offset_of(UEFI_PARTITION_TABLE_HEADER, header.size) +
+			sizeof(upth->header.size))
+		return;
+	to_copy = le32_to_cpu(upth->header.size);
+
+	/* Expecting to copy exactly the size of EfiPartitionHeader (92bytes) */
+	if (length < to_copy ||
+	    to_copy != sizeof(uefi_gpt_data->EfiPartitionHeader))
+		return;
+
+	memcpy(&uefi_gpt_data->EfiPartitionHeader, addr, to_copy);
 	uefi_gpt_data->NumberOfPartitions = cpu_to_le64(0);
 }
 
diff --git a/lib/libtpm/tcgbios_int.h b/lib/libtpm/tcgbios_int.h
index cc38455..5bbd9d5 100644
--- a/lib/libtpm/tcgbios_int.h
+++ b/lib/libtpm/tcgbios_int.h
@@ -116,7 +116,6 @@ typedef struct {
 	uint32_t numPartEntry;
 	uint32_t partEntrySize;
 	uint32_t partArrayCrc32;
-	uint8_t reserved[420];
 } __attribute__((packed)) UEFI_PARTITION_TABLE_HEADER;
 
 typedef struct {
-- 
2.25.1