--- /dev/null
+// Copyright 2018 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#ifndef __SYS_RANDOM__
+#define __SYS_RANDOM__
+
+#include <sys/types.h>
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+ssize_t getrandom(void *buf, size_t buflen, unsigned int flags);
+
+#ifdef __cplusplus
+} // extern "C"
+#endif
+
+#endif //__SYS_RANDOM__
--- /dev/null
+// Copyright 2018 Espressif Systems (Shanghai) PTE LTD
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+// http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <sys/random.h>
+#include <sys/param.h>
+#include <assert.h>
+#include <errno.h>
+#include <string.h>
+#include "esp_system.h"
+#include "esp_log.h"
+
+static const char *TAG = "RANDOM";
+
+ssize_t getrandom(void *buf, size_t buflen, unsigned int flags)
+{
+ // Flags are ignored because:
+ // - esp_random is non-blocking so it works for both blocking and non-blocking calls,
+ // - don't have opportunity so set som other source of entropy.
+
+ ESP_LOGD(TAG, "getrandom(buf=0x%x, buflen=%d, flags=%u)", (int) buf, buflen, flags);
+
+ if (buf == NULL) {
+ errno = EFAULT;
+ ESP_LOGD(TAG, "getrandom returns -1 (EFAULT)");
+ return -1;
+ }
+
+ uint8_t *dst = (uint8_t *) buf;
+ ssize_t ret = 0;
+
+ while (ret < buflen) {
+ const uint32_t random = esp_random();
+ const int needed = buflen - ret;
+ const int copy_len = MIN(sizeof(random), needed);
+ memcpy(dst + ret, &random, copy_len);
+ ret += copy_len;
+ }
+
+ ESP_LOGD(TAG, "getrandom returns %d", ret);
+ return ret;
+}