Merge pull request #2312 from gmaxwell/random_random

ApproximateBestSubset internal RNG to prevent degenerate behavior.

1 files changed, 20 insertions, 6 deletions

diff --git a/src/util.cpp b/src/util.cpp
index 1f66aff609..4eff6ce71b 100644
--- a/src/util.cpp
+++ b/src/util.cpp
@@ -1281,12 +1281,26 @@ void AddTimeData(const CNetAddr& ip, int64 nTime)
     }
 }
 
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+uint32_t insecure_rand_Rz = 11;
+uint32_t insecure_rand_Rw = 11;
+void seed_insecure_rand(bool fDeterministic)
+{
+    //The seed values have some unlikely fixed points which we avoid.
+    if(fDeterministic)
+    {
+        insecure_rand_Rz = insecure_rand_Rw = 11;
+    } else {
+        uint32_t tmp;
+        do{
+            RAND_bytes((unsigned char*)&tmp,4);
+        }while(tmp==0 || tmp==0x9068ffffU);
+        insecure_rand_Rz=tmp;
+        do{
+            RAND_bytes((unsigned char*)&tmp,4);
+        }while(tmp==0 || tmp==0x464fffffU);
+        insecure_rand_Rw=tmp;
+    }
+}
 
 string FormatVersion(int nVersion)
 {