Merge #9693: Prevent integer overflow in ReadVarInt.

45f0961 Prevent integer overflow in ReadVarInt. (Gregory Maxwell)

Tree-SHA512: 385ea0efb6b59d44c45a49227e5f6fff236b4775544cbeb236312a3fd87fd75c226ac56f7aa1bca66b853639da75a579610074f7582f92cf2ebd4a74bc40f6f0

src/serialize.h

@@ -336,12 +336,19 @@ I ReadVarInt(Stream& is)
     I n = 0;
     while(true) {
         unsigned char chData = ser_readdata8(is);
+        if (n > (std::numeric_limits<I>::max() >> 7)) {
+           throw std::ios_base::failure("ReadVarInt(): size too large");
+        }
         n = (n << 7) | (chData & 0x7F);
-        if (chData & 0x80)
+        if (chData & 0x80) {
+            if (n == std::numeric_limits<I>::max()) {
+                throw std::ios_base::failure("ReadVarInt(): size too large");
+            }
             n++;
-        else
+        } else {
             return n;
         }
+    }
 }
 
 #define FLATDATA(obj) REF(CFlatData((char*)&(obj), (char*)&(obj) + sizeof(obj)))