Add tests for arc4random_buf() and an implementation for those without.

lib/util/arc4random_buf.c

@@ -0,0 +1,69 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2020 Todd C. Miller <Todd.Miller@sudo.ws>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * This is an open source non-commercial project. Dear PVS-Studio, please check it.
+ * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+ */
+
+#include <config.h>
+
+#ifndef HAVE_ARC4RANDOM_BUF
+
+#include <sys/types.h>
+#include <stdlib.h>
+#if defined(HAVE_STDINT_H)
+# include <stdint.h>
+#elif defined(HAVE_INTTYPES_H)
+# include <inttypes.h>
+#endif
+
+#include "sudo_compat.h"
+#include "sudo_rand.h"
+
+/*
+ * Call arc4random() repeatedly to fill buf with n bytes of random data.
+ */
+void
+sudo_arc4random_buf(void *buf, size_t n)
+{
+	char *cp = buf;
+
+	while (n != 0) {
+		size_t m = minimum(n, 4);
+		uint32_t val = arc4random();
+
+		switch (m) {
+		case 4:
+			*cp++ = (val >> 24) & 0xff;
+			/* FALLTHROUGH */
+		case 3:
+			*cp++ = (val >> 16) & 0xff;
+			/* FALLTHROUGH */
+		case 2:
+			*cp++ = (val >> 8) & 0xff;
+			/* FALLTHROUGH */
+		case 1:
+			*cp++ = val & 0xff;
+			break;
+		}
+		n -= m;
+	}
+}
+
+#endif /* HAVE_ARC4RANDOM_BUF */