random: Introduce a random generator

This adds flb_randombytes(), which fills the given buffer with random
numbers using each OS's built-in Crypt API.

The most common use scenario is:

    unsigned char buf[64]

    if (get_randombytes(buf, 64)) {
        flb_error("cannot get random bytes");
    }

This function supports both UNIX and Windows. You can use this
function without caring the underlying OS.

Signed-off-by: Fujimoto Seiji <[email protected]>

include/fluent-bit/flb_random.h

@@ -0,0 +1,30 @@
+/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+
+/*  Fluent Bit
+ *  ==========
+ *  Copyright (C) 2019-2020 The Fluent Bit Authors
+ *  Copyright (C) 2015-2018 Treasure Data Inc.
+ *
+ *  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 FLB_RANDOM_H
+#define FLB_RANDOM_H
+
+/*
+ * Fill buffer with the random bytes. Return 0 on success;
+ * -1 on error.
+ */
+int flb_randombytes(unsigned char *buf, int len);
+
+#endif

src/CMakeLists.txt

@@ -42,6 +42,7 @@ set(src
   flb_time.c
   flb_sosreport.c
   flb_sha512.c
+  flb_random.c
   flb_plugin.c
   flb_gzip.c
   flb_http_client.c
@@ -195,6 +196,7 @@ if(CMAKE_SYSTEM_NAME MATCHES "Windows")
   set(FLB_DEPS
     "ws2_32.lib"
     "crypt32.lib"
+    "Bcrypt.lib"
     )
 else()
   set(FLB_DEPS

src/flb_random.c

@@ -0,0 +1,64 @@
+/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+
+/*  Fluent Bit
+ *  ==========
+ *  Copyright (C) 2019-2020 The Fluent Bit Authors
+ *  Copyright (C) 2015-2018 Treasure Data Inc.
+ *
+ *  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>
+
+/*
+ * 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 Unix, we use /dev/urandom as a secure random source.
+ */
+
+int flb_randombytes(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;
+    int bytes;
+
+    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
+}

tests/internal/CMakeLists.txt

@@ -16,6 +16,7 @@ set(UNIT_TESTS_FILES
   utils.c
   gzip.c
   gelf.c
+  random.c
   config_map.c
   )
 

tests/internal/random.c

@@ -0,0 +1,33 @@
+/* -*- Mode: C; tab-width: 4; indent-tabs-mode: nil; c-basic-offset: 4 -*- */
+
+#include <fluent-bit/flb_random.h>
+
+#include "flb_tests_internal.h"
+
+void test_randombytes()
+{
+    int ret;
+    unsigned char buf1[64] = {0};
+    unsigned char buf2[64] = {0};
+
+    /* The following tests check whether:
+     *
+     * (1) the random generator fills the buffer with numbers at all.
+     * (2) a successive call generates different numbers.
+     *
+     * These tests are probabilistic by nature; If we assume an ideal random
+     * generator, they are expected to fail once in 2^192 (= 10^57) runs.
+     */
+    ret = flb_randombytes(buf1, 64);
+    TEST_CHECK(ret == 0);
+    TEST_CHECK(memcmp(buf1, buf2, 64) != 0);
+
+    ret = flb_randombytes(buf2, 64);
+    TEST_CHECK(ret == 0);
+    TEST_CHECK(memcmp(buf1, buf2, 64) != 0);
+}
+
+TEST_LIST = {
+    {"randombytes", test_randombytes},
+    { 0 }
+};