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Add SafeReadBytes from VM #71

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merged 7 commits into from
Dec 10, 2018
Merged

Add SafeReadBytes from VM #71

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ec3d576
removed ReadVarBytes from VM
igormcoelho Dec 9, 2018
aedcf10
using SafeReadBytes instead of ReadBytes
igormcoelho Dec 9, 2018
a369e79
Fix compilation error
erikzhang Dec 10, 2018
3cab9ab
re-add `ReadVarBytes()`
erikzhang Dec 10, 2018
c899f15
Update `SafeReadBytes()`
erikzhang Dec 10, 2018
6384e15
Update `ReadVarBytes()`
erikzhang Dec 10, 2018
67df28c
Fix max value
shargon Dec 10, 2018
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15 changes: 8 additions & 7 deletions src/neo-vm/ExecutionEngine.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -58,7 +58,7 @@ public void Execute()
private void ExecuteOp(OpCode opcode, ExecutionContext context)
{
if (opcode >= OpCode.PUSHBYTES1 && opcode <= OpCode.PUSHBYTES75)
context.EvaluationStack.Push(context.OpReader.ReadBytes((byte)opcode));
context.EvaluationStack.Push(context.OpReader.SafeReadBytes((byte)opcode));
else
switch (opcode)
{
Expand All @@ -67,13 +67,13 @@ private void ExecuteOp(OpCode opcode, ExecutionContext context)
context.EvaluationStack.Push(new byte[0]);
break;
case OpCode.PUSHDATA1:
context.EvaluationStack.Push(context.OpReader.ReadBytes(context.OpReader.ReadByte()));
context.EvaluationStack.Push(context.OpReader.SafeReadBytes(context.OpReader.ReadByte()));
break;
case OpCode.PUSHDATA2:
context.EvaluationStack.Push(context.OpReader.ReadBytes(context.OpReader.ReadUInt16()));
context.EvaluationStack.Push(context.OpReader.SafeReadBytes(context.OpReader.ReadUInt16()));
break;
case OpCode.PUSHDATA4:
context.EvaluationStack.Push(context.OpReader.ReadBytes(context.OpReader.ReadInt32()));
context.EvaluationStack.Push(context.OpReader.SafeReadBytes(context.OpReader.ReadInt32()));
break;
case OpCode.PUSHM1:
case OpCode.PUSH1:
Expand Down Expand Up @@ -166,7 +166,7 @@ private void ExecuteOp(OpCode opcode, ExecutionContext context)
return;
}

byte[] script_hash = context.OpReader.ReadBytes(20);
byte[] script_hash = context.OpReader.SafeReadBytes(20);
if (script_hash.All(p => p == 0))
{
script_hash = context.EvaluationStack.Pop().GetByteArray();
Expand All @@ -189,7 +189,8 @@ private void ExecuteOp(OpCode opcode, ExecutionContext context)
}
break;
case OpCode.SYSCALL:
if (Service?.Invoke(context.OpReader.ReadVarBytes(252), this) != true)
int length = context.OpReader.ReadByte();
if ((length > 252) || (Service?.Invoke(context.OpReader.SafeReadBytes(length), this) != true))
State |= VMState.FAULT;
break;

Expand Down Expand Up @@ -987,7 +988,7 @@ private void ExecuteOp(OpCode opcode, ExecutionContext context)
if (opcode == OpCode.CALL_ED || opcode == OpCode.CALL_EDT)
script_hash = context.EvaluationStack.Pop().GetByteArray();
else
script_hash = context.OpReader.ReadBytes(20);
script_hash = context.OpReader.SafeReadBytes(20);
byte[] script = table.GetScript(script_hash);
if (script == null)
{
Expand Down
22 changes: 4 additions & 18 deletions src/neo-vm/Helper.cs
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Original file line number Diff line number Diff line change
Expand Up @@ -5,25 +5,11 @@ namespace Neo.VM
{
internal static class Helper
{
public static byte[] ReadVarBytes(this BinaryReader reader, int max = 0X7fffffc7)
public static byte[] SafeReadBytes(this BinaryReader reader, int max = 0x1000000)
{
return reader.ReadBytes((int)reader.ReadVarInt((ulong)max));
}

public static ulong ReadVarInt(this BinaryReader reader, ulong max = ulong.MaxValue)
{
byte fb = reader.ReadByte();
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You can't remove this logic

ulong value;
if (fb == 0xFD)
value = reader.ReadUInt16();
else if (fb == 0xFE)
value = reader.ReadUInt32();
else if (fb == 0xFF)
value = reader.ReadUInt64();
else
value = fb;
if (value > max) throw new FormatException();
return value;
if((max > 0x1000000) || (!reader.BaseStream.CanSeek) || (reader.BaseStream.Length - reader.BaseStream.Position) < max))
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If we want to throw an exception, then is not needed to check CanSeek, because this could throw an exception when you access to length in wrong streams

throw new FormatException;
return reader.ReadBytes(max);
}
}
}