From 52d4b1a1aae176745dba871f0b01c06f081ab1ca Mon Sep 17 00:00:00 2001
From: Patric Mueller <bhaak@gmx.net>
Date: Fri, 11 Jan 2019 19:23:01 +0100
Subject: [PATCH] reseed during level change to prevent deduction of rng state

For platforms that read from the system's random number generator,
reseed during level change, before the map of a new level is created and
after level creation has finished.
---
 src/do.c      |  1 +
 src/hacklib.c | 11 +++++++++++
 src/mklev.c   |  4 ++++
 3 files changed, 16 insertions(+)

diff --git a/src/do.c b/src/do.c
index e069c3ac6..ad2e3045d 100644
--- a/src/do.c
+++ b/src/do.c
@@ -1420,6 +1420,7 @@ boolean at_stairs, falling, portal;
             /* we'll reach here if running in wizard mode */
             error("Cannot continue this game.");
         }
+        reseed_random();
         minit(); /* ZEROCOMP */
         getlev(fd, hackpid, new_ledger, FALSE);
         (void) nhclose(fd);
diff --git a/src/hacklib.c b/src/hacklib.c
index 8ceb9fcde..409c34007 100644
--- a/src/hacklib.c
+++ b/src/hacklib.c
@@ -917,6 +917,17 @@ init_random()
     set_random(seed);
 }
 
+/* Reshuffles the random number generator. */
+void
+reseed_random()
+{
+    /* only reseed if we are certain that the seed generation is unguessable
+     * by the players. */
+#ifdef DEV_RANDOM
+    init_random();
+#endif
+}
+
 time_t
 getnow()
 {
diff --git a/src/mklev.c b/src/mklev.c
index 16cc32bde..4cf5b9000 100644
--- a/src/mklev.c
+++ b/src/mklev.c
@@ -982,6 +982,8 @@ mklev()
     struct mkroom *croom;
     int ridx;
 
+    reseed_random();
+
     init_mapseen(&u.uz);
     if (getbones())
         return;
@@ -1009,6 +1011,8 @@ mklev()
        entered; rooms[].orig_rtype always retains original rtype value */
     for (ridx = 0; ridx < SIZE(rooms); ridx++)
         rooms[ridx].orig_rtype = rooms[ridx].rtype;
+
+    reseed_random();
 }
 
 void
-- 
2.40.0