Use standard RNG

The custom random number generator can now be replaced with a C++11
RNG. This greatly improves the reliability and trustworthiness of it.

In addition to this, the conversion of the RNG to a thread-local object
removes the race condition that was present in the previous
implementation. It also theoretically improves performance by a tiny bit.

include/maxscale/random.h

@@ -16,13 +16,6 @@
 
 MXS_BEGIN_DECLS
 
-/**
- * @brief Initialize the random number generator
- *
- * Uses /dev/urandom if available, and warms the generator up with 1000 iterations.
- */
-void random_jkiss_init(void);
-
 /**
  * @brief Return a pseudo-random number
  *
@@ -30,6 +23,6 @@ void random_jkiss_init(void);
  *
  * @return A random number
  */
-unsigned int random_jkiss(void);
+unsigned int mxs_random(void);
 
 MXS_END_DECLS

server/core/CMakeLists.txt

@@ -36,7 +36,7 @@ add_library(maxscale-common SHARED
   poll.cc
   queryclassifier.cc
   query_classifier.cc
-  random_jkiss.cc
+  random.cc
   resultset.cc
   resource.cc
   router.cc

server/core/gateway.cc

@@ -53,7 +53,7 @@
 #include <maxscale/session.h>
 #include <maxscale/utils.h>
 #include <maxscale/version.h>
-#include <maxscale/random_jkiss.h>
+#include <maxscale/random.h>
 
 #include "internal/admin.hh"
 #include "internal/config.hh"
@@ -1783,9 +1783,6 @@ int main(int argc, char **argv)
         goto return_main;
     }
 
-    /** Initialize the random number generator */
-    random_jkiss_init();
-
     if (!utils_init())
     {
         const char* logerr = "Failed to initialise utility library.";

server/core/maxkeys.c

@@ -29,7 +29,7 @@
 
 #include <maxscale/log_manager.h>
 #include <maxscale/paths.h>
-#include <maxscale/random_jkiss.h>
+#include <maxscale/random.h>
 
 #ifdef HAVE_GLIBC
 struct option options[] =
@@ -101,7 +101,6 @@ int main(int argc, char **argv)
     }
 
     mxs_log_init(NULL, NULL, MXS_LOG_TARGET_DEFAULT);
-    random_jkiss_init();
 
     if (secrets_write_keys(directory) != 0)
     {

server/core/maxpasswd.c

@@ -32,7 +32,7 @@
 
 #include <maxscale/paths.h>
 #include <maxscale/log_manager.h>
-#include <maxscale/random_jkiss.h>
+#include <maxscale/random.h>
 #include <maxscale/alloc.h>
 
 #include "internal/secrets.h"
@@ -163,8 +163,6 @@ int main(int argc, char **argv)
     mxs_log_set_priority_enabled(LOG_INFO, false);
     mxs_log_set_priority_enabled(LOG_DEBUG, false);
 
-    random_jkiss_init();
-
     size_t len = strlen(password);
 
     if (len > MXS_PASSWORD_MAXLEN)

server/core/random.cc

@@ -0,0 +1,28 @@
+/*
+ * Copyright (c) 2016 MariaDB Corporation Ab
+ *
+ * Use of this software is governed by the Business Source License included
+ * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
+ *
+ * Change Date: 2022-01-01
+ *
+ * On the date above, in accordance with the Business Source License, use
+ * of this software will be governed by version 2 or later of the General
+ * Public License.
+ */
+
+#include <maxscale/random.h>
+
+#include <random>
+
+namespace
+{
+
+thread_local std::mt19937 generator(std::random_device{}());
+
+}
+
+unsigned int mxs_random(void)
+{
+    return generator();
+}

server/core/random_jkiss.cc

@@ -1,109 +0,0 @@
-/*
- * Copyright (c) 2016 MariaDB Corporation Ab
- *
- * Use of this software is governed by the Business Source License included
- * in the LICENSE.TXT file and at www.mariadb.com/bsl11.
- *
- * Change Date: 2022-01-01
- *
- * On the date above, in accordance with the Business Source License, use
- * of this software will be governed by version 2 or later of the General
- * Public License.
- */
-
-/**
- * @file random_jkiss.c  -  Random number generator for the MariaDB Corporation MaxScale
- *
- * See http://www0.cs.ucl.ac.uk/staff/d.jones/GoodPracticeRNG.pdf for discussion of random
- * number generators (RNGs).
- */
-
-#include <stdbool.h>
-#include <sys/types.h>
-#include <sys/stat.h>
-#include <fcntl.h>
-#include <unistd.h>
-#include <maxscale/random_jkiss.h>
-#include <maxscale/debug.h>
-
-/* Public domain code for JKISS RNG - Comment header added */
-
-/* If possible, the seed variables will be set from /dev/urandom but
- * should that fail, these arbitrary numbers will be used as a last resort.
- */
-static unsigned int x = 123456789, y = 987654321, z = 43219876, c = 6543217; /* Seed variables */
-static bool init = false;
-
-unsigned int random_jkiss(void)
-{
-    unsigned long long t;
-    unsigned int result;
-    ss_dassert(init);
-
-    x = 314527869 * x + 1234567;
-    y ^= y << 5;
-    y ^= y >> 7;
-    y ^= y << 22;
-    t = 4294584393ULL * z + c;
-    c = t >> 32;
-    z = t;
-    result = x + y + z;
-    return result;
-}
-
-/* Own code adapted from http://www0.cs.ucl.ac.uk/staff/d.jones/GoodPracticeRNG.pdf */
-
-/***
- *
- * Obtain a seed random number from /dev/urandom if available.
- *
- * @return  uint    Random number
- *
- */
-static unsigned int random_jkiss_devrand(void)
-{
-    int fn;
-    unsigned int r;
-
-    if ((fn = open("/dev/urandom", O_RDONLY)) == -1)
-    {
-        return 0;
-    }
-
-    if (read(fn, &r, sizeof(r)) != sizeof(r))
-    {
-        r = 0;
-    }
-    close(fn);
-    return r;
-}
-
-void random_jkiss_init(void)
-{
-    if (!init)
-    {
-        int newrand, i;
-
-        if ((newrand = random_jkiss_devrand()) != 0)
-        {
-            x = newrand;
-        }
-
-        if ((newrand = random_jkiss_devrand()) != 0)
-        {
-            y = newrand;
-        }
-
-        if ((newrand = random_jkiss_devrand()) != 0)
-        {
-            z = newrand;
-        }
-
-        if ((newrand = random_jkiss_devrand()) != 0)
-        {
-            c = newrand % 698769068 + 1; /* Should be less than 698769069 */
-        }
-
-        init = true;
-    }
-}

server/core/secrets.cc

@@ -22,7 +22,7 @@
 #include <maxscale/log_manager.h>
 #include <maxscale/paths.h>
 #include <maxscale/protocol/mysql.h>
-#include <maxscale/random_jkiss.h>
+#include <maxscale/random.h>
 #include <maxscale/utils.h>
 
 #include "internal/secrets.h"
@@ -35,7 +35,7 @@
 static unsigned char
 secrets_randomchar()
 {
-    return (char) ((random_jkiss() % ('~' - ' ')) + ' ');
+    return (char) ((mxs_random() % ('~' - ' ')) + ' ');
 }
 
 static int

server/core/test/test_logthrottling.cc

@@ -21,7 +21,7 @@
 #include <sched.h>
 #include <semaphore.h>
 #include <maxscale/log_manager.h>
-#include <maxscale/random_jkiss.h>
+#include <maxscale/random.h>
 
 using std::cerr;
 using std::cout;
@@ -161,7 +161,6 @@ int main(int argc, char* argv[])
     int rc;
 
     std::ios::sync_with_stdio();
-    random_jkiss_init();
     rc = sem_init(&u_semstart, 0, 0);
     ensure(rc == 0);
 

server/core/utils.cc

@@ -48,7 +48,7 @@
 #include <maxscale/limits.h>
 #include <maxscale/pcre2.h>
 #include <maxscale/poll.h>
-#include <maxscale/random_jkiss.h>
+#include <maxscale/random.h>
 #include <maxscale/secrets.h>
 #include <maxscale/session.h>
 
@@ -161,7 +161,7 @@ char *gw_strend(register const char *s)
  *****************************************/
 static char gw_randomchar()
 {
-    return (char)((random_jkiss() % 78) + 30);
+    return (char)((mxs_random() % 78) + 30);
 }
 
 /*****************************************

server/modules/routing/avrorouter/avro.cc

@@ -35,7 +35,7 @@
 #include <maxscale/modulecmd.h>
 #include <maxscale/paths.h>
 #include <maxscale/protocol/mysql.h>
-#include <maxscale/random_jkiss.h>
+#include <maxscale/random.h>
 #include <maxscale/router.h>
 #include <maxscale/server.h>
 #include <maxscale/service.h>

server/modules/routing/avrorouter/avro_main.cc

@@ -30,7 +30,7 @@
 #include <maxscale/modulecmd.h>
 #include <maxscale/paths.h>
 #include <maxscale/protocol/mysql.h>
-#include <maxscale/random_jkiss.h>
+#include <maxscale/random.h>
 #include <maxscale/router.h>
 #include <maxscale/server.h>
 #include <maxscale/service.h>