From: Markus Valentin <m...@denx.de>
Introduce functions that check the integrity of U-Boot by utilising
the hashes stored in the OEM-data block in Secure Boot Manifest.
The verification functions get called in fsp_init()
Signed-off-by: Markus Valentin <m...@denx.de>
Signed-off-by: Anatolij Gustschin <ag...@denx.de>
---
Changes in v3:
- lower case in hex numbers
- fix RAM stage payload hash calculation and add comments
for associated macros
- add comments explaining used stage indexes, s/*_ID/*_IDX
- fixed two spaces in comment
- s/devicetree/device tree
- extend the output messages to give more hints when FIT key
verification fails
-
Changes in v2:
- use 'const void *' for fdt property ptr, drop cast
- s/u-boot/U-Boot/
- fix function comment style and move comments to header with
prototypes. Use fsp_ prefix
- fix multiline comment style
- s/SB:/Secure Boot/ for non-debug messages
arch/x86/cpu/baytrail/Makefile | 1 +
arch/x86/cpu/baytrail/secure_boot.c | 117 +++++++++++++++++++++
.../include/asm/arch-baytrail/fsp/fsp_configs.h | 24 +++++
arch/x86/lib/fsp/fsp_support.c | 18 ++++
4 files changed, 160 insertions(+)
create mode 100644 arch/x86/cpu/baytrail/secure_boot.c
diff --git a/arch/x86/cpu/baytrail/Makefile b/arch/x86/cpu/baytrail/Makefile
index a0216f3059..dbf9a82c39 100644
--- a/arch/x86/cpu/baytrail/Makefile
+++ b/arch/x86/cpu/baytrail/Makefile
@@ -8,4 +8,5 @@ obj-y += cpu.o
obj-y += early_uart.o
obj-y += fsp_configs.o
obj-y += valleyview.o
+obj-$(CONFIG_BAYTRAIL_SECURE_BOOT) += secure_boot.o
obj-$(CONFIG_GENERATE_ACPI_TABLE) += acpi.o
diff --git a/arch/x86/cpu/baytrail/secure_boot.c
b/arch/x86/cpu/baytrail/secure_boot.c
new file mode 100644
index 0000000000..eaf35c6e24
--- /dev/null
+++ b/arch/x86/cpu/baytrail/secure_boot.c
@@ -0,0 +1,117 @@
+/*
+ * Copyright (C) 2017 Markus Valentin <m...@denx.de>
+ *
+ * SPDX-License-Identifier: GPL-2.0+
+ */
+
+#include <common.h>
+
+#define SB_MANIFEST_BASE 0xfffe0000
+#define SB_MANIFEST_SIZE 0x400
+#define SB_MANIFEST_OEM_DATA_OFFSET 0x58
+#define SB_MANIFEST_OEM_HASH_OFFSET (SB_MANIFEST_OEM_DATA_OFFSET + 4)
+#define SB_MANIFEST_OEM_HASH_BASE (SB_MANIFEST_BASE + \
+ SB_MANIFEST_OEM_HASH_OFFSET)
+#define SB_MANIFEST_END (SB_MANIFEST_BASE +
SB_MANIFEST_SIZE)
+
+#define FIT_KEY_NAME "dev"
+#define PUB_KEY_MODULUS_SIZE 0x100
+
+/*
+ * U-Boot in RAM stage payload from reset vector to FSP Stage2:
+ * 0xfff0000 to 0xfffc0000
+ */
+#define U_BOOT_STAGE_START CONFIG_SYS_TEXT_BASE
+#define U_BOOT_STAGE_SIZE 0xc0000
+
+/*
+ * Indexes of 32-byte blocks in the OEM-data area containing sha256 hashes
+ * of RAM stage payload, FSP Stage2 and other OEM specific data. The order
+ * of RAM stage payload and FSP Stage2 blocks is fixed (idx 0 and 1),
+ * do not change it. We do not verify FSP Stage2 here, it will be verified
+ * in FSP (FSP Stage2 idx 1 is not used). So, the first index of OEM specific
+ * data block hash must start from 2.
+ */
+#define SHA256_U_BOOT_STAGE_IDX 0
+#define SHA256_FIT_PUB_KEY_IDX 2
+
+/**
+ * verify_oem_sha256() - oem data block verification
+ *
+ * This function compares a hash which gets retrieved from the oem data block
+ * with the runtime calculated hash of start_address+size. If they match,
+ * this function returns true. If not, it returns false.
+ *
+ * @hash_idx: index of oem-data block with hash to compare
+ * @start_address: address where the hash calculation should start
+ * @size: length of the region for hash calculation
+ *
+ * @retval: true on success, false on error
+ */
+static bool verify_oem_sha256(unsigned int hash_idx,
+ const void *start_address,
+ size_t size)
+{
+ uint8_t value[SHA256_SUM_LEN];
+ int value_len;
+
+ /* Calculate address of hash to compare in the oemdata block */
+ void *hash_to_verify = (void *)SB_MANIFEST_OEM_HASH_BASE +
+ (SHA256_SUM_LEN * hash_idx);
+#ifdef DEBUG
+ unsigned int i = 0;
+ uint8_t oem_value[SHA256_SUM_LEN];
+
+ memcpy(oem_value, hash_to_verify, SHA256_SUM_LEN);
+ printf("SB: hash to verify:\t");
+ for (i = 0; i < SHA256_SUM_LEN; i++)
+ printf("%02X", oem_value[i]);
+ printf("\n");
+#endif
+
+ /* Calculate the hash of the binary */
+ calculate_hash(start_address, size, "sha256", value, &value_len);
+
+#ifdef DEBUG
+ printf("SB: calculated hash:\t");
+ for (i = 0; i < SHA256_SUM_LEN; i++)
+ printf("%02X", value[i]);
+ printf("\n");
+#endif
+ /* Compare the two hash values */
+ if (memcmp(hash_to_verify, value, SHA256_SUM_LEN))
+ return false;
+ return true;
+}
+
+bool fsp_verify_u_boot_bin(void)
+{
+ return verify_oem_sha256(SHA256_U_BOOT_STAGE_IDX,
+ (const void *)U_BOOT_STAGE_START,
+ U_BOOT_STAGE_SIZE);
+}
+
+bool fsp_verify_public_key(void)
+{
+ const void *fit_public_key_modulus;
+ int offset = fdt_node_offset_by_prop_value(gd->fdt_blob, -1,
+ "key-name-hint",
+ FIT_KEY_NAME,
+ 4);
+ int ret;
+
+ fit_public_key_modulus = fdt_getprop(gd->fdt_blob, offset,
+ "rsa,modulus", NULL);
+ if (!fit_public_key_modulus) {
+ puts("No FIT public key in U-Boot device tree\n");
+ return false;
+ }
+
+ ret = verify_oem_sha256(SHA256_FIT_PUB_KEY_IDX,
+ fit_public_key_modulus,
+ PUB_KEY_MODULUS_SIZE);
+ if (!ret)
+ puts("FIT public key checksum wrong\n");
+
+ return ret;
+}
diff --git a/arch/x86/include/asm/arch-baytrail/fsp/fsp_configs.h
b/arch/x86/include/asm/arch-baytrail/fsp/fsp_configs.h
index 1c6c2479f0..2c8c32b9bf 100644
--- a/arch/x86/include/asm/arch-baytrail/fsp/fsp_configs.h
+++ b/arch/x86/include/asm/arch-baytrail/fsp/fsp_configs.h
@@ -103,4 +103,28 @@ struct fspinit_rtbuf {
#define SCC_MODE_ACPI 0
#define SCC_MODE_PCI 1
+#ifndef __ASSEMBLY__
+/**
+ * fsp_verify_u_boot_bin() - U-Boot binary verification
+ *
+ * This function verifies the integrity for U-Boot, its device tree and the
+ * ucode appended or inserted to the device tree.
+ *
+ * @retval: true on success, false on error
+ */
+bool fsp_verify_u_boot_bin(void);
+
+/**
+ * fsp_verify_public_key() - integrity of public key for fit image verification
+ *
+ * This function verifies the integrity for the modulus of the public key which
+ * is stored in the U-Boot device tree for fit image verification. It tries to
+ * find the "rsa,modulus" property in the dtb and then verifies it with the
+ * checksum stored in the oem-data block
+ *
+ * @retval: true on success, false on error
+ */
+bool fsp_verify_public_key(void);
+#endif
+
#endif /* __FSP_CONFIGS_H__ */
diff --git a/arch/x86/lib/fsp/fsp_support.c b/arch/x86/lib/fsp/fsp_support.c
index d79a6e900a..c7e0a9eff4 100644
--- a/arch/x86/lib/fsp/fsp_support.c
+++ b/arch/x86/lib/fsp/fsp_support.c
@@ -152,6 +152,24 @@ void fsp_init(u32 stack_top, u32 boot_mode, void *nvs_buf)
*/
printf("FSP: Secure Boot %sabled\n",
fsp_vpd->enable_secure_boot == 1 ? "en" : "dis");
+
+ if (!fsp_verify_u_boot_bin()) {
+ /*
+ * If our U-Boot binary checksum isn't equal to
+ * our expected checksum we need to stop booting
+ */
+ printf("%s Failed to verify U-Boot and dtb\n", SB_PRFX);
+ hang();
+ }
+
+ /*
+ * Verification of the public key happens with verification of
+ * the device tree binary (that's where it's stored), this check
+ * is not necessary, but nice to see it's integer
+ */
+ if (!fsp_verify_public_key())
+ printf("%s Failed to verify public key for FIT image\n",
+ SB_PRFX);
#endif
/* Copy default data from Flash */
--
2.11.0
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