security/vboot: Add store/validate methods for AMD VBIOS FMAP cache

Add methods to store and retrieve the hash of the data stored in the
VBIOS cache FMAP region. Add a dedicated index in TPM NVRAM to store
the hash, and methods to calculate/read/write it.

Modeled after mrc_cache_hash_tpm.{c,h}

BUG=b:255812886
TEST=tested with rest of patch train

Change-Id: I030017d3bf956b8593bc09073ad6545b80a5b52b
Signed-off-by: Matt DeVillier <matt.devillier@amd.corp-partner.google.com>
Reviewed-on: https://review.coreboot.org/c/coreboot/+/72401
Tested-by: build bot (Jenkins) <no-reply@coreboot.org>
Reviewed-by: Martin L Roth <gaumless@gmail.com>

src/security/vboot/Makefile.inc

@@ -127,6 +127,8 @@ postcar-y += common.c
 romstage-$(CONFIG_MRC_SAVE_HASH_IN_TPM) += mrc_cache_hash_tpm.c
 ramstage-$(CONFIG_MRC_SAVE_HASH_IN_TPM) += mrc_cache_hash_tpm.c
 
+ramstage-$(CONFIG_SOC_AMD_GFX_CACHE_VBIOS_IN_FMAP) += vbios_cache_hash_tpm.c
+
 ifeq ($(CONFIG_VBOOT_SEPARATE_VERSTAGE),y)
 
 $(eval $(call vboot-for-stage,verstage))

src/security/vboot/antirollback.h

@@ -29,6 +29,7 @@ enum vb2_pcr_digest;
 #define MRC_RW_HASH_NV_INDEX            0x100d
 #define HASH_NV_SIZE                    VB2_SHA256_DIGEST_SIZE
 #define ENT_ROLLBACK_SPACE_INDEX        0x100e
+#define VBIOS_CACHE_NV_INDEX            0x100f
 /* Widevine Secure Counter space */
 #define WIDEVINE_COUNTER_NV_INDEX(n)	(0x3000 + (n))
 #define NUM_WIDEVINE_COUNTERS		4
@@ -99,4 +100,17 @@ uint32_t antirollback_write_space_mrc_hash(uint32_t index, const uint8_t *data,
 */
 uint32_t antirollback_lock_space_mrc_hash(uint32_t index);
 
+/*
+ * Read VBIOS hash data from TPM.
+ * @param data  pointer to buffer where hash from TPM read into
+ * @param size  size of buffer
+ */
+uint32_t antirollback_read_space_vbios_hash(uint8_t *data, uint32_t size);
+/*
+ * Write new hash data to VBIOS space in TPM.
+ * @param data  pointer to buffer of hash value to be written
+ * @param size  size of buffer
+*/
+uint32_t antirollback_write_space_vbios_hash(const uint8_t *data, uint32_t size);
+
 #endif  /* ANTIROLLBACK_H_ */

src/security/vboot/secdata_mock.c

@@ -69,3 +69,13 @@ vb2_error_t antirollback_write_space_mrc_hash(uint32_t index, const uint8_t *dat
 {
 	return VB2_SUCCESS;
 }
+
+vb2_error_t antirollback_read_space_vbios_hash(uint8_t *data, uint32_t size)
+{
+	return VB2_SUCCESS;
+}
+
+vb2_error_t antirollback_write_space_vbios_hash(const uint8_t *data, uint32_t size)
+{
+	return VB2_SUCCESS;
+}

src/security/vboot/secdata_tpm.c

@@ -481,6 +481,52 @@ uint32_t antirollback_lock_space_mrc_hash(uint32_t index)
 	return tlcl_lock_nv_write(index);
 }
 
+static uint32_t read_space_vbios_hash(uint8_t *data)
+{
+	RETURN_ON_FAILURE(tlcl_read(VBIOS_CACHE_NV_INDEX, data, HASH_NV_SIZE));
+	return TPM_SUCCESS;
+}
+
+uint32_t antirollback_read_space_vbios_hash(uint8_t *data, uint32_t size)
+{
+	if (size != HASH_NV_SIZE) {
+		VBDEBUG("TPM: Incorrect buffer size for hash idx 0x%x. "
+			"(Expected=0x%x Actual=0x%x).\n", VBIOS_CACHE_NV_INDEX, HASH_NV_SIZE,
+			size);
+		return TPM_E_READ_FAILURE;
+	}
+	return read_space_vbios_hash(data);
+}
+
+uint32_t antirollback_write_space_vbios_hash(const uint8_t *data, uint32_t size)
+{
+	uint8_t spc_data[HASH_NV_SIZE];
+	uint32_t rv;
+
+	if (size != HASH_NV_SIZE) {
+		VBDEBUG("TPM: Incorrect buffer size for hash idx 0x%x. "
+			"(Expected=0x%x Actual=0x%x).\n", VBIOS_CACHE_NV_INDEX, HASH_NV_SIZE,
+			size);
+		return TPM_E_WRITE_FAILURE;
+	}
+
+	rv = read_space_vbios_hash(spc_data);
+	if (rv == TPM_E_BADINDEX) {
+		/*
+		 * If space is not defined already for hash, define
+		 * new space.
+		 */
+		VBDEBUG("TPM: Initializing hash space.\n");
+		return setup_space("VBIOS Cache Hash", VBIOS_CACHE_NV_INDEX, data, HASH_NV_SIZE,
+				   rw_space_attributes, NULL, 0);
+	}
+
+	if (rv != TPM_SUCCESS)
+		return rv;
+
+	return safe_write(VBIOS_CACHE_NV_INDEX, data, size);
+}
+
 #else
 
 /**

src/security/vboot/vbios_cache_hash_tpm.c

@@ -0,0 +1,75 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#include <security/vboot/antirollback.h>
+#include <program_loading.h>
+#include <vb2_api.h>
+#include <security/tpm/tss.h>
+#include <security/vboot/misc.h>
+#include <security/vboot/vbios_cache_hash_tpm.h>
+#include <console/console.h>
+#include <string.h>
+
+void vbios_cache_update_hash(const uint8_t *data, size_t size)
+{
+	struct vb2_hash hash;
+
+	/* Initialize TPM driver. */
+	if (tlcl_lib_init() != VB2_SUCCESS) {
+		printk(BIOS_ERR, "VBIOS_CACHE: TPM driver initialization failed.\n");
+		return;
+	}
+
+	/* Calculate hash of vbios data. */
+	if (vb2_hash_calculate(vboot_hwcrypto_allowed(), data, size,
+			       VB2_HASH_SHA256, &hash)) {
+		printk(BIOS_ERR, "VBIOS_CACHE: SHA-256 calculation failed for data; "
+		       "clearing TPM hash space.\n");
+		/*
+		 * Since data is being updated in vbios cache, the hash
+		 * currently stored in TPM hash space is no longer
+		 * valid. If we are not able to calculate hash of the
+		 * data being updated, reset all the bits in TPM hash
+		 * space to zero to invalidate it.
+		 */
+		memset(hash.raw, 0, VB2_SHA256_DIGEST_SIZE);
+	}
+
+	/* Write hash of data to TPM space. */
+	if (antirollback_write_space_vbios_hash(hash.sha256, sizeof(hash.sha256))
+			!= TPM_SUCCESS) {
+		printk(BIOS_ERR, "VBIOS_CACHE: Could not save hash to TPM.\n");
+		return;
+	}
+
+	printk(BIOS_INFO, "VBIOS_CACHE: TPM NV idx 0x%x updated successfully.\n",
+			VBIOS_CACHE_NV_INDEX);
+}
+
+enum cb_err vbios_cache_verify_hash(const uint8_t *data, size_t size)
+{
+	struct vb2_hash tpm_hash = { .algo = VB2_HASH_SHA256 };
+
+	/* Initialize TPM driver. */
+	if (tlcl_lib_init() != VB2_SUCCESS) {
+		printk(BIOS_ERR, "VBIOS_CACHE: TPM driver initialization failed.\n");
+		return CB_ERR;
+	}
+
+	/* Read hash of VBIOS data saved in TPM. */
+	if (antirollback_read_space_vbios_hash(tpm_hash.sha256,	sizeof(tpm_hash.sha256))
+			!= TPM_SUCCESS) {
+		printk(BIOS_ERR, "VBIOS_CACHE: Could not read hash from TPM.\n");
+		return CB_ERR;
+	}
+
+	/* Calculate hash of data read from VBIOS FMAP CACHE and compare. */
+	if (vb2_hash_verify(vboot_hwcrypto_allowed(), data, size, &tpm_hash)) {
+		printk(BIOS_ERR, "VBIOS_CACHE: Hash comparison failed.\n");
+		return CB_ERR;
+	}
+
+	printk(BIOS_INFO, "VBIOS_CACHE: Hash idx 0x%x comparison successful.\n",
+			VBIOS_CACHE_NV_INDEX);
+
+	return CB_SUCCESS;
+}

src/security/vboot/vbios_cache_hash_tpm.h

@@ -0,0 +1,18 @@
+/* SPDX-License-Identifier: GPL-2.0-only */
+
+#ifndef _VBIOS_CACHE_HASH_TPM_H_
+#define _VBIOS_CACHE_HASH_TPM_H_
+
+#include <types.h>
+
+/*
+ * Updates vbios cache hash.
+ */
+void vbios_cache_update_hash(const uint8_t *data, size_t size);
+
+/*
+ * Verifies vbios cache hash which is stored in FMAP region.
+ */
+enum cb_err vbios_cache_verify_hash(const uint8_t *data, size_t size);
+
+#endif /* _VBIOS_CACHE_HASH_TPM_H_ */