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//-----------------------------------------------------------------------
// <copyright file="SymbolHelper.cs" company="Microsoft Corporation">
// Copyright (c) Microsoft Corporation. All rights reserved.
// </copyright>
//-----------------------------------------------------------------------
namespace System.Activities.Debugger.Symbol
{
using System.Diagnostics.CodeAnalysis;
using System.IO;
using System.Linq;
using System.Runtime;
using System.Security;
using System.Security.Cryptography;
internal static class SymbolHelper
{
static readonly Guid Md5IdentifierGuid = new Guid("406ea660-64cf-4c82-b6f0-42d48172a799");
static readonly Guid Sha1IdentifierGuid = new Guid("ff1816ec-aa5e-4d10-87f7-6f4963833460");
public static Guid ChecksumProviderId
{
get
{
if (LocalAppContextSwitches.UseMD5ForWFDebugger)
{
return Md5IdentifierGuid;
}
else
{
return Sha1IdentifierGuid;
}
}
}
// This is the same Encode/Decode logic as the WCF FramingEncoder
public static int ReadEncodedInt32(BinaryReader reader)
{
int value = 0;
int bytesConsumed = 0;
while (true)
{
int next = reader.ReadByte();
value |= (next & 0x7F) << (bytesConsumed * 7);
bytesConsumed++;
if ((next & 0x80) == 0)
{
break;
}
}
return value;
}
// This is the same Encode/Decode logic as the WCF FramingEncoder
public static void WriteEncodedInt32(BinaryWriter writer, int value)
{
Fx.Assert(value >= 0, "Must be non-negative");
while ((value & 0xFFFFFF80) != 0)
{
writer.Write((byte)((value & 0x7F) | 0x80));
value >>= 7;
}
writer.Write((byte)value);
}
public static int GetEncodedSize(int value)
{
Fx.Assert(value >= 0, "Must be non-negative");
int count = 1;
while ((value & 0xFFFFFF80) != 0)
{
count++;
value >>= 7;
}
return count;
}
public static byte[] CalculateChecksum(string fileName)
{
Fx.Assert(!string.IsNullOrEmpty(fileName), "fileName should not be empty or null");
byte[] checksum;
try
{
using (StreamReader streamReader = new StreamReader(fileName))
{
using (HashAlgorithm hashAlgorithm = CreateHashProvider())
{
checksum = hashAlgorithm.ComputeHash(streamReader.BaseStream);
}
}
}
catch (IOException)
{
// DirectoryNotFoundException and FileNotFoundException are expected
checksum = null;
}
catch (UnauthorizedAccessException)
{
// UnauthorizedAccessException is expected
checksum = null;
}
catch (SecurityException)
{
// Must not have had enough permissions to access the file.
checksum = null;
}
return checksum;
}
[Fx.Tag.SecurityNote(Critical = "Used to get a string from checksum that is provided by the user/from a file.",
Safe = "We not exposing any critical data. Just converting the byte array to a hex string.")]
[SecuritySafeCritical]
public static string GetHexStringFromChecksum(byte[] checksum)
{
return checksum == null ? string.Empty : string.Join(string.Empty, checksum.Select(x => x.ToString("X2")).ToArray());
}
[Fx.Tag.SecurityNote(Critical = "Used to validate checksum that is provided by the user/from a file.",
Safe = "We not exposing any critical data. Just validating that the provided checksum meets the format for the checksums we produce.")]
[SecuritySafeCritical]
internal static bool ValidateChecksum(byte[] checksumToValidate)
{
// We are using MD5.ComputeHash, which will return a 16 byte array.
if (LocalAppContextSwitches.UseMD5ForWFDebugger)
{
return checksumToValidate.Length == 16;
}
else
{
return checksumToValidate.Length == 20;
}
}
[SuppressMessage("Microsoft.Cryptographic.Standard", "CA5350:MD5CannotBeUsed",
Justification = "Design has been approved. We are not using MD5 for any security or cryptography purposes but rather as a hash.")]
static HashAlgorithm CreateHashProvider()
{
if (LocalAppContextSwitches.UseMD5ForWFDebugger)
{
return new MD5CryptoServiceProvider();
}
else
{
return new SHA1CryptoServiceProvider();
}
}
}
}
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