1 files changed, 125 insertions, 0 deletions
diff --git a/dnsdist-random.cc b/dnsdist-random.cc
new file mode 100644
index 0000000..01e3ba4
--- /dev/null
+++ b/dnsdist-random.cc
@@ -0,0 +1,125 @@
+/*
+ * This file is part of PowerDNS or dnsdist.
+ * Copyright -- PowerDNS.COM B.V. and its contributors
+ *
+ * This program is free software; you can redistribute it and/or modify
+ * it under the terms of version 2 of the GNU General Public License as
+ * published by the Free Software Foundation.
+ *
+ * In addition, for the avoidance of any doubt, permission is granted to
+ * link this program with OpenSSL and to (re)distribute the binaries
+ * produced as the result of such linking.
+ *
+ * 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, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
+ */
+#include "config.h"
+
+#include <stdexcept>
+#include <sys/time.h>
+#include <unistd.h>
+#ifdef HAVE_LIBSODIUM
+#include <sodium.h>
+#endif /* HAVE_LIBSODIUM */
+#ifdef HAVE_RAND_BYTES
+#include <openssl/rand.h>
+#endif /* HAVE_RAND_BYTES */
+
+#if defined(HAVE_GETRANDOM)
+#include <sys/random.h>
+#endif
+
+#include "dnsdist-random.hh"
+#include "dns_random.hh"
+#include "dolog.hh"
+#include "misc.hh"
+
+namespace dnsdist
+{
+#if !defined(HAVE_LIBSODIUM) && defined(HAVE_GETRANDOM)
+static bool s_useGetRandom{true};
+#endif
+
+void initRandom()
+{
+#ifdef HAVE_LIBSODIUM
+  srandom(randombytes_random());
+#else
+  {
+    auto getSeed = []() {
+#if defined(HAVE_GETRANDOM)
+      char buf[1];
+      // some systems define getrandom but it does not really work, e.g. because it's
+      // not present in kernel.
+      if (getrandom(buf, sizeof(buf), 0) == -1 && errno != EINTR) {
+        warnlog("getrandom() failed %s", stringerror());
+        s_useGetRandom = false;
+      }
+#endif /* HAVE_GETRANDOM */
+#ifdef HAVE_RAND_BYTES
+      unsigned int seed;
+      if (RAND_bytes(reinterpret_cast<unsigned char*>(&seed), sizeof(seed)) == 1) {
+        return seed;
+      }
+#endif /* HAVE_RAND_BYTES */
+      struct timeval tv;
+      gettimeofday(&tv, 0);
+      return static_cast<unsigned int>(tv.tv_sec ^ tv.tv_usec ^ getpid());
+    };
+
+    srandom(getSeed());
+  }
+#endif
+}
+
+uint32_t getRandomValue(uint32_t upperBound)
+{
+#ifdef HAVE_LIBSODIUM
+  return randombytes_uniform(upperBound);
+#else /* HAVE_LIBSODIUM */
+  uint32_t result = 0;
+  unsigned int min = pdns::random_minimum_acceptable_value(upperBound);
+
+#if defined(HAVE_GETRANDOM)
+  if (s_useGetRandom) {
+    do {
+      auto got = getrandom(&result, sizeof(result), 0);
+      if (got == -1 && errno == EINTR) {
+        continue;
+      }
+      if (got != sizeof(result)) {
+        throw std::runtime_error("Error getting a random value via getrandom(): " + stringerror());
+      }
+    } while (result < min);
+
+    return result % upperBound;
+  }
+#endif /* HAVE_GETRANDOM */
+#ifdef HAVE_RAND_BYTES
+  do {
+    if (RAND_bytes(reinterpret_cast<unsigned char*>(&result), sizeof(result)) != 1) {
+      throw std::runtime_error("Error getting a random value via RAND_bytes");
+    }
+  } while (result < min);
+
+  return result % upperBound;
+#endif /* HAVE_RAND_BYTES */
+  do {
+    result = random();
+  } while (result < min);
+
+  return result % upperBound;
+#endif /* HAVE_LIBSODIUM */
+}
+
+uint16_t getRandomDNSID()
+{
+  return getRandomValue(65536);
+}
+}