util/rand_xor: add function to seed rand

V2: pass the seed to the seed function so that we can isolate
    its uses. Stop leaking fd when urandom couldn't be read.

Reviewed-by: Grazvydas Ignotas <[email protected]>
Reviewed-by: Nicolai Hähnle <[email protected]>

2 files changed, 69 insertions, 0 deletions

diff --git a/src/util/rand_xor.c b/src/util/rand_xor.c
index 07b4c22ee15..de05fa64b3c 100644
--- a/src/util/rand_xor.c
+++ b/src/util/rand_xor.c
@@ -1,3 +1,34 @@
+/*
+ * Copyright 2017 Timothy Arceri
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a
+ * copy of this software and associated documentation files (the "Software"),
+ * to deal in the Software without restriction, including without limitation
+ * the rights to use, copy, modify, merge, publish, distribute, sublicense,
+ * and/or sell copies of the Software, and to permit persons to whom the
+ * Software is furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice (including the next
+ * paragraph) shall be included in all copies or substantial portions of the
+ * Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT.  IN NO EVENT SHALL
+ * THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+ * SOFTWARE.
+ *
+ */
+
+#if defined(__linux__)
+#include <sys/file.h>
+#include <unistd.h>
+#else
+#include <time.h>
+#endif
+
 #include "rand_xor.h"
 
 /* Super fast random number generator.
@@ -18,3 +49,37 @@ rand_xorshift128plus(uint64_t *seed)
 
    return s[1] + s0;
 }
+
+void
+s_rand_xorshift128plus(uint64_t *seed, bool randomised_seed)
+{
+   if (!randomised_seed)
+      goto fixed_seed;
+
+#if defined(__linux__)
+   int fd = open("/dev/urandom", O_RDONLY);
+   if (fd < 0)
+      goto fixed_seed;
+
+   size_t seed_size = sizeof(uint64_t) * 2;
+   if (read(fd, seed, seed_size) != seed_size) {
+      close(fd);
+      goto fixed_seed;
+   }
+
+   close(fd);
+   return;
+
+#else
+   seed[0] = 0x3bffb83978e24f88;
+   seed[1] = time(NULL);
+
+   return;
+#endif
+
+fixed_seed:
+
+   /* Fallback to a fixed seed */
+   seed[0] = 0x3bffb83978e24f88;
+   seed[1] = 0x9238d5d56c71cd35;
+}
diff --git a/src/util/rand_xor.h b/src/util/rand_xor.h
index d5144e98230..532d549bcda 100644
--- a/src/util/rand_xor.h
+++ b/src/util/rand_xor.h
@@ -26,8 +26,12 @@
 #define RAND_XOR_H
 
 #include <stdint.h>
+#include <stdbool.h>
 
 uint64_t
 rand_xorshift128plus(uint64_t *seed);
 
+void
+s_rand_xorshift128plus(uint64_t *seed, bool randomised_seed);
+
 #endif /* RAND_XOR_H */