1 files changed, 51 insertions, 0 deletions
diff --git a/lib/getentropy.c b/lib/getentropy.c
new file mode 100644
index 0000000000..2b6c3f55fa
--- /dev/null
+++ b/lib/getentropy.c
@@ -0,0 +1,51 @@
+/* Fill a buffer with random bytes.
+   Copyright 2020 Free Software Foundation, Inc.
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU General Public License as published by
+   the Free Software Foundation; either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU General Public License for more details.
+
+   You should have received a copy of the GNU General Public License
+   along with this program.  If not, see <https://www.gnu.org/licenses/>.  */
+
+/* Written by Paul Eggert.  */
+
+#include <config.h>
+
+#include <unistd.h>
+
+#include <errno.h>
+#include <sys/random.h>
+
+/* Overwrite BUFFER with random data.  BUFFER contains LENGTH bytes.
+   LENGTH must be at most 256.  Return 0 on success, -1 (setting
+   errno) on failure.  */
+int
+getentropy (void *buffer, size_t length)
+{
+  char *buf = buffer;
+
+  if (length <= 256)
+    for (;;)
+      {
+        ssize_t bytes;
+        if (length == 0)
+          return 0;
+        while ((bytes = getrandom (buf, length, 0)) < 0)
+          if (errno != EINTR)
+            return -1;
+        if (bytes == 0)
+          break;
+        buf += bytes;
+        length -= bytes;
+      }
+
+  errno = EIO;
+  return -1;
+}