1 files changed, 82 insertions, 0 deletions
diff --git a/common/trng.c b/common/trng.c
new file mode 100644
index 0000000000..273a078d7a
--- /dev/null
+++ b/common/trng.c
@@ -0,0 +1,82 @@
+/* Copyright 2023 The ChromiumOS Authors
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+/* Common Random Number Generation (RNG) routines */
+
+#include "common.h"
+#include "console.h"
+#include "cpu.h"
+#include "host_command.h"
+#include "panic.h"
+#include "printf.h"
+#include "registers.h"
+#include "system.h"
+#include "task.h"
+#include "trng.h"
+#include "util.h"
+
+test_mockable void trng_rand_bytes(void *buffer, size_t len)
+{
+	while (len) {
+		uint32_t number = trng_rand();
+		size_t cnt = 4;
+		/* deal with the lack of alignment guarantee in the API */
+		uintptr_t align = (uintptr_t)buffer & 3;
+
+		if (len < 4 || align) {
+			cnt = MIN(4 - align, len);
+			memcpy(buffer, &number, cnt);
+		} else {
+			*(uint32_t *)buffer = number;
+		}
+		len -= cnt;
+		buffer += cnt;
+	}
+}
+
+#if defined(CONFIG_CMD_RAND)
+/*
+ * We want to avoid accidentally exposing debug commands in RO since we can't
+ * update RO once in production.
+ */
+#if defined(SECTION_IS_RW)
+static int command_rand(int argc, const char **argv)
+{
+	uint8_t data[32];
+	char str_buf[hex_str_buf_size(sizeof(data))];
+
+	trng_init();
+	trng_rand_bytes(data, sizeof(data));
+	trng_exit();
+	snprintf_hex_buffer(str_buf, sizeof(str_buf),
+			    HEX_BUF(data, sizeof(data)));
+	ccprintf("rand %s\n", str_buf);
+
+	return EC_RES_SUCCESS;
+}
+DECLARE_CONSOLE_COMMAND(rand, command_rand, NULL,
+			"Output random bytes to console.");
+
+static enum ec_status host_command_rand(struct host_cmd_handler_args *args)
+{
+	const struct ec_params_rand_num *p = args->params;
+	struct ec_response_rand_num *r = args->response;
+	uint16_t num_rand_bytes = p->num_rand_bytes;
+
+	if (system_is_locked())
+		return EC_RES_ACCESS_DENIED;
+	if (num_rand_bytes > args->response_max)
+		return EC_RES_OVERFLOW;
+	trng_init();
+	trng_rand_bytes(r->rand, num_rand_bytes);
+	trng_exit();
+	args->response_size = num_rand_bytes;
+
+	return EC_RES_SUCCESS;
+}
+DECLARE_HOST_COMMAND(EC_CMD_RAND_NUM, host_command_rand,
+		     EC_VER_MASK(EC_VER_RAND_NUM));
+#endif /* SECTION_IS_RW */
+#endif /* CONFIG_CMD_RAND */