[crypto/entropy] Make the entropy source ready for use

sw/device/lib/base/BUILD

@@ -274,6 +274,7 @@ cc_library(
     deps = [
         ":bitfield",
         ":hardened",
+        "//sw/device/lib/crypto/drivers:rv_core_ibex",
     ],
 )
 

sw/device/lib/base/random_order.c

@@ -6,6 +6,7 @@
 
 #include "sw/device/lib/base/bitfield.h"
 #include "sw/device/lib/base/hardened.h"
+#include "sw/device/lib/crypto/drivers/rv_core_ibex.h"
 
 void random_order_init(random_order_t *ctx, size_t min_len) {
   ctx->ctr = 0;

sw/device/lib/crypto/impl/BUILD

@@ -385,3 +385,14 @@ cc_library(
         "//sw/device/lib/crypto/include:datatypes",
     ],
 )
+
+cc_library(
+    name = "entropy_src",
+    srcs = ["entropy_src.c"],
+    hdrs = ["//sw/device/lib/crypto/include:entropy_src.h"],
+    deps = [
+        "//sw/device/lib/base:hardened_memory",
+        "//sw/device/lib/crypto/drivers:entropy",
+        "//sw/device/lib/crypto/include:datatypes",
+    ],
+)

sw/device/lib/crypto/impl/entropy_src.c

@@ -0,0 +1,23 @@
+// Copyright lowRISC contributors (OpenTitan project).
+// Licensed under the Apache License, Version 2.0, see LICENSE for details.
+// SPDX-License-Identifier: Apache-2.0
+
+#include "sw/device/lib/crypto/include/entropy_src.h"
+
+#include <stdbool.h>
+
+#include "sw/device/lib/crypto/drivers/entropy.h"
+#include "sw/device/lib/crypto/impl/status.h"
+
+// Module ID for status codes.
+#define MODULE_ID MAKE_MODULE_ID('e', 't', 's')
+
+otcrypto_status_t otcrypto_entropy_init(void) {
+  HARDENED_TRY(entropy_complex_init());
+  return OTCRYPTO_OK;
+}
+
+otcrypto_status_t otcrypto_entropy_check(void) {
+  HARDENED_TRY(entropy_complex_check());
+  return OTCRYPTO_OK;
+}

sw/device/lib/crypto/include/BUILD

@@ -41,6 +41,7 @@ cc_library(
         "ecc_curve25519.h",
         "ecc_p256.h",
         "ecc_p384.h",
+        "entropy_src.h",
         "hkdf.h",
         "hmac.h",
         "integrity.h",
@@ -79,6 +80,7 @@ cc_library(
         "ecc_curve25519.h",
         "ecc_p256.h",
         "ecc_p384.h",
+        "entropy_src.h",
         "hkdf.h",
         "hmac.h",
         "integrity.h",

sw/device/lib/crypto/include/entropy_src.h

@@ -0,0 +1,50 @@
+// Copyright lowRISC contributors (OpenTitan project).
+// Licensed under the Apache License, Version 2.0, see LICENSE for details.
+// SPDX-License-Identifier: Apache-2.0
+
+#ifndef OPENTITAN_SW_DEVICE_LIB_CRYPTO_INCLUDE_ENTROPY_SRC_H_
+#define OPENTITAN_SW_DEVICE_LIB_CRYPTO_INCLUDE_ENTROPY_SRC_H_
+
+#include "datatypes.h"
+
+/**
+ * @file
+ * @brief Entropy source functions for the OpenTitan cryptography library.
+ *
+ * Instantiate and use the TRNG. Acts as a wrapper to the entropy driver.
+ */
+
+#ifdef __cplusplus
+extern "C" {
+#endif  // __cplusplus
+
+/**
+ * Configures the entropy source in continuous mode with FIPS thresholds.
+ *
+ * @return Operation status in `otcrypto_status_t` format.
+ */
+OT_WARN_UNUSED_RESULT
+otcrypto_status_t otcrypto_entropy_init(void);
+
+/**
+ * Ensures that the entropy complex is ready for use and verify the health
+ * checks of the generated randomness.
+ *
+ * Ensures that the entropy complex is running and that `entropy_src` is in
+ * FIPS mode, and verifies the thresholds for health tests in `entropy_src`.
+ * This function should be called periodically while the entropy complex is in
+ * use, because the threshold registers are not shadowed.
+ *
+ * The test also verifies the health checks of the generated randomness
+ * providing a status error if a health test jumped.
+ *
+ * @return Operation status in `otcrypto_status_t` format.
+ */
+OT_WARN_UNUSED_RESULT
+otcrypto_status_t otcrypto_entropy_check(void);
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif  // __cplusplus
+
+#endif  // OPENTITAN_SW_DEVICE_LIB_CRYPTO_INCLUDE_ENTROPY_SRC_H_