Platform: Add boot seed support
Add a getter function to platform code, which makes possible
to get the boot seed value. Boot seed is a mandatory claim
in the initial attestation token.
Change-Id: Ifd547c541a51093f0766b57ba9e9cdd124cd840d
Signed-off-by: Tamas Ban <tamas.ban@arm.com>
diff --git a/platform/include/tfm_plat_boot_seed.h b/platform/include/tfm_plat_boot_seed.h
new file mode 100644
index 0000000..11b79f0
--- /dev/null
+++ b/platform/include/tfm_plat_boot_seed.h
@@ -0,0 +1,56 @@
+/*
+ * Copyright (c) 2018, Arm Limited. All rights reserved.
+ *
+ * SPDX-License-Identifier: BSD-3-Clause
+ *
+ */
+
+#ifndef __TFM_PLAT_BOOT_SEED_H__
+#define __TFM_PLAT_BOOT_SEED_H__
+/**
+ * \file tfm_plat_boot_seed.h
+ *
+ * Boot seed is used by a validating entity to ensure multiple reports were
+ * generated in the same boot session. Boot seed is a random number, generated
+ * only once during a boot cycle and its value is constant in the same cycle.
+ * Size recommendation is 256-bit to meet the statistically improbable property.
+ * Boot seed can be generated by secure boot loader an included to the measured
+ * boot state or can be generated by PRoT SW.
+ */
+
+/**
+ * \note The interfaces defined in this file must be implemented for each
+ * SoC.
+ */
+
+#include <stdint.h>
+#include "tfm_plat_defs.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/*!
+ * \def BOOT_SEED_SIZE
+ *
+ * \brief Size of boot seed in bytes.
+ */
+#define BOOT_SEED_SIZE (32u)
+
+/**
+ * \brief Gets the boot seed, which is a constant random number during a boot
+ * cycle.
+ *
+ * \param[in] size The required size of boot seed in bytes
+ * \param[out] buf Pointer to the buffer to store boot seed
+ *
+ * \return TFM_PLAT_ERR_SUCCESS if the value is generated correctly. Otherwise,
+ * it returns TFM_PLAT_ERR_SYSTEM_ERR.
+ */
+enum tfm_plat_err_t tfm_plat_get_boot_seed(uint32_t size, uint8_t *buf);
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif /* __TFM_PLAT_BOOT_SEED_H__ */