1 files changed, 97 insertions, 0 deletions
diff --git a/fluent-bit/src/flb_random.c b/fluent-bit/src/flb_random.c
new file mode 100644
index 000000000..2425ec258
--- /dev/null
+++ b/fluent-bit/src/flb_random.c
@@ -0,0 +1,97 @@
+/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+
+/*  Fluent Bit
+ *  ==========
+ *  Copyright (C) 2015-2022 The Fluent Bit Authors
+ *
+ *  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 <fluent-bit/flb_compat.h>
+#include <fcntl.h>
+
+#ifdef FLB_HAVE_GETENTROPY
+#include <unistd.h>
+#endif
+#ifdef FLB_HAVE_GETENTROPY_SYS_RANDOM
+#include <sys/random.h>
+#endif
+
+#define MAX_GETENTROPY_LEN 256
+
+/*
+ * This module provides a random number generator for common use cases.
+ *
+ * On Windows, we use BCryptGenRandom() from CNG API. This function
+ * is available since Windows Vista, and should be compliant to the
+ * official recommendation.
+ *
+ * On other platforms, we use getentropy(3) if available, otherwise
+ * /dev/urandom as a secure random source.
+ */
+
+int flb_random_bytes(unsigned char *buf, int len)
+{
+#ifdef FLB_SYSTEM_WINDOWS
+    NTSTATUS ret;
+    ret = BCryptGenRandom(NULL, buf, len, BCRYPT_USE_SYSTEM_PREFERRED_RNG);
+    if (!BCRYPT_SUCCESS(ret)) {
+        return -1;
+    }
+    return 0;
+#else
+    int     fd;
+    ssize_t bytes;
+
+#if defined(FLB_HAVE_GETENTROPY) || defined(FLB_HAVE_GETENTROPY_SYS_RANDOM)
+    while (len > 0) {
+        if (len > MAX_GETENTROPY_LEN) {
+            bytes = MAX_GETENTROPY_LEN;
+        }
+        else {
+            bytes = len;
+        }
+        if (getentropy(buf, bytes) < 0) {
+#ifdef ENOSYS
+            /* Fall back to urandom if the syscall is not available (Linux only) */
+            if (errno == ENOSYS) {                
+                goto try_urandom;
+            }
+#endif
+            return -1;
+        }
+        len -= bytes;
+        buf += bytes;
+    }
+    return 0;
+
+try_urandom:
+#endif /* FLB_HAVE_GETENTROPY || FLB_HAVE_GETENTROPY_SYS_RANDOM */
+    fd = open("/dev/urandom", O_RDONLY);
+    if (fd == -1) {
+        return -1;
+    }
+
+    while (len > 0) {
+        bytes = read(fd, buf, len);
+        if (bytes <= 0) {
+            close(fd);
+            return -1;
+        }
+        len -= bytes;
+        buf += bytes;
+    }
+    close(fd);
+    return 0;
+#endif /* FLB_SYSTEM_WINDOWS */
+}