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[PS-1471] Create Allocation Free EncryptedStringAttribute validation (#2273)

Browse Source 
* Add new logic for validating encrypted strings

* Add benchmarks

* Formatting & Comments

* Move Debug assertion to just be a test

* Address PR feedback pt.1

* Address more PR feedback

* Formatting

* merge branch 'master' into 'encrypted-string-perf'

* Revert "merge branch 'master' into 'encrypted-string-perf'"

This reverts commit a20e127c9c.
This commit is contained in:
Justin Baur
2022-10-20 16:10:02 -04:00
committed by GitHub
parent 63ae7c8b66
commit a349f28840
11 changed files with 3074 additions and 148 deletions
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2
src/Core/Enums/EncryptionType.cs
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@ -1,5 +1,7 @@
namespace Bit.Core.Enums;
// If the backing type here changes to a different type you will likely also need to change the value used in
// EncryptedStringAttribute
public enum EncryptionType : byte
{
AesCbc256_B64 = 0,

176
src/Core/Utilities/EncryptedStringAttribute.cs Normal file
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@ -0,0 +1,176 @@
using System.Buffers;
using System.ComponentModel.DataAnnotations;
using Bit.Core.Enums;
#nullable enable
namespace Bit.Core.Utilities;
/// <summary>
/// Validates a string that is in encrypted form: "head.b64iv=|b64ct=|b64mac="
/// </summary>
public class EncryptedStringAttribute : ValidationAttribute
{
internal static readonly Dictionary<EncryptionType, int> _encryptionTypeToRequiredPiecesMap = new()
{
[EncryptionType.AesCbc256_B64] = 2, // iv|ct
[EncryptionType.AesCbc128_HmacSha256_B64] = 3, // iv|ct|mac
[EncryptionType.AesCbc256_HmacSha256_B64] = 3, // iv|ct|mac
[EncryptionType.Rsa2048_OaepSha256_B64] = 1, // rsaCt
[EncryptionType.Rsa2048_OaepSha1_B64] = 1, // rsaCt
[EncryptionType.Rsa2048_OaepSha256_HmacSha256_B64] = 2, // rsaCt|mac
[EncryptionType.Rsa2048_OaepSha1_HmacSha256_B64] = 2, // rsaCt|mac
};
public EncryptedStringAttribute()
: base("{0} is not a valid encrypted string.")
{ }
public override bool IsValid(object? value)
{
try
{
if (value is null)
{
return true;
}
if (value is string stringValue)
{
// Fast path
return IsValidCore(stringValue);
}
// This attribute should only be placed on string properties, fail
return false;
}
catch
{
return false;
}
}
internal static bool IsValidCore(ReadOnlySpan<char> value)
{
if (!value.TrySplitBy('.', out var headerChunk, out var rest))
{
// We couldn't find a header part, this is the slow path, because we have to do two loops over
// the data.
// If it has 3 encryption parts that means it is AesCbc128_HmacSha256_B64
// else we assume it is AesCbc256_B64
var splitChars = rest.Count('|');
if (splitChars == 2)
{
return ValidatePieces(rest, _encryptionTypeToRequiredPiecesMap[EncryptionType.AesCbc128_HmacSha256_B64]);
}
else
{
return ValidatePieces(rest, _encryptionTypeToRequiredPiecesMap[EncryptionType.AesCbc256_B64]);
}
}
EncryptionType encryptionType;
// Using byte here because that is the backing type for EncryptionType
if (!byte.TryParse(headerChunk, out var encryptionTypeNumber))
{
// We can't read the header chunk as a number, this is the slow path
if (!Enum.TryParse(headerChunk, out encryptionType))
{
// Can't even get the enum from a non-number header, fail
return false;
}
// Since this value came from Enum.TryParse we know it is an enumerated object and we can therefore
// just access the dictionary
return ValidatePieces(rest, _encryptionTypeToRequiredPiecesMap[encryptionType]);
}
// Simply cast the number to the enum, this could be a value that doesn't actually have a backing enum
// entry but that is alright we will use it to look in the dictionary and non-valid
// numbers will be filtered out there.
encryptionType = (EncryptionType)encryptionTypeNumber;
if (!_encryptionTypeToRequiredPiecesMap.TryGetValue(encryptionType, out var encryptionPieces))
{
// Could not find a configuration map for the given header piece. This is an invalid string
return false;
}
return ValidatePieces(rest, encryptionPieces);
}
private static bool ValidatePieces(ReadOnlySpan<char> encryptionPart, int requiredPieces)
{
var rest = encryptionPart;
while (requiredPieces != 0)
{
if (requiredPieces == 1)
{
// Only one more part is needed so don't split and check the chunk
if (!IsValidBase64(rest))
{
return false;
}
// Make sure there isn't another split character possibly denoting another chunk
return rest.IndexOf('|') == -1;
}
else
{
// More than one part is required so split it out
if (!rest.TrySplitBy('|', out var chunk, out rest))
{
return false;
}
// Is the required chunk valid base 64?
if (!IsValidBase64(chunk))
{
return false;
}
}
// This current piece is valid so we can count down
requiredPieces--;
}
// No more parts are required, so check there are no extra parts
return rest.IndexOf('|') == -1;
}
private static bool IsValidBase64(ReadOnlySpan<char> input)
{
const int StackLimit = 256;
byte[]? pooledChunks = null;
var upperLimitLength = CalculateBase64ByteLengthUpperLimit(input.Length);
// Ref: https://vcsjones.dev/stackalloc/
var byteBuffer = upperLimitLength > StackLimit
? (pooledChunks = ArrayPool<byte>.Shared.Rent(upperLimitLength))
: stackalloc byte[StackLimit];
try
{
var successful = Convert.TryFromBase64Chars(input, byteBuffer, out var bytesWritten);
return successful && bytesWritten > 0;
}
finally
{
// Check if we rented the pool and if so, return it.
if (pooledChunks != null)
{
ArrayPool<byte>.Shared.Return(pooledChunks, true);
}
}
}
internal static int CalculateBase64ByteLengthUpperLimit(int charLength)
{
return 3 * (charLength / 4);
}
}

137
src/Core/Utilities/EncryptedValueAttribute.cs
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@ -1,137 +0,0 @@
using System.ComponentModel.DataAnnotations;
namespace Bit.Core.Utilities;
/// <summary>
/// Validates a string that is in encrypted form: "head.b64iv=|b64ct=|b64mac="
/// </summary>
public class EncryptedStringAttribute : ValidationAttribute
{
public EncryptedStringAttribute()
: base("{0} is not a valid encrypted string.")
{ }
public override bool IsValid(object value)
{
if (value == null)
{
return true;
}
try
{
var encString = value?.ToString();
if (string.IsNullOrWhiteSpace(encString))
{
return false;
}
var headerPieces = encString.Split('.');
string[] encStringPieces = null;
var encType = Enums.EncryptionType.AesCbc256_B64;
if (headerPieces.Length == 1)
{
encStringPieces = headerPieces[0].Split('|');
if (encStringPieces.Length == 3)
{
encType = Enums.EncryptionType.AesCbc128_HmacSha256_B64;
}
else
{
encType = Enums.EncryptionType.AesCbc256_B64;
}
}
else if (headerPieces.Length == 2)
{
encStringPieces = headerPieces[1].Split('|');
if (!Enum.TryParse(headerPieces[0], out encType))
{
return false;
}
}
switch (encType)
{
case Enums.EncryptionType.AesCbc256_B64:
case Enums.EncryptionType.Rsa2048_OaepSha1_HmacSha256_B64:
case Enums.EncryptionType.Rsa2048_OaepSha256_HmacSha256_B64:
if (encStringPieces.Length != 2)
{
return false;
}
break;
case Enums.EncryptionType.AesCbc128_HmacSha256_B64:
case Enums.EncryptionType.AesCbc256_HmacSha256_B64:
if (encStringPieces.Length != 3)
{
return false;
}
break;
case Enums.EncryptionType.Rsa2048_OaepSha256_B64:
case Enums.EncryptionType.Rsa2048_OaepSha1_B64:
if (encStringPieces.Length != 1)
{
return false;
}
break;
default:
return false;
}
switch (encType)
{
case Enums.EncryptionType.AesCbc256_B64:
case Enums.EncryptionType.AesCbc128_HmacSha256_B64:
case Enums.EncryptionType.AesCbc256_HmacSha256_B64:
var iv = Convert.FromBase64String(encStringPieces[0]);
var ct = Convert.FromBase64String(encStringPieces[1]);
if (iv.Length < 1 || ct.Length < 1)
{
return false;
}
if (encType == Enums.EncryptionType.AesCbc128_HmacSha256_B64 ||
encType == Enums.EncryptionType.AesCbc256_HmacSha256_B64)
{
var mac = Convert.FromBase64String(encStringPieces[2]);
if (mac.Length < 1)
{
return false;
}
}
break;
case Enums.EncryptionType.Rsa2048_OaepSha256_B64:
case Enums.EncryptionType.Rsa2048_OaepSha1_B64:
case Enums.EncryptionType.Rsa2048_OaepSha1_HmacSha256_B64:
case Enums.EncryptionType.Rsa2048_OaepSha256_HmacSha256_B64:
var rsaCt = Convert.FromBase64String(encStringPieces[0]);
if (rsaCt.Length < 1)
{
return false;
}
if (encType == Enums.EncryptionType.Rsa2048_OaepSha1_HmacSha256_B64 ||
encType == Enums.EncryptionType.Rsa2048_OaepSha256_HmacSha256_B64)
{
var mac = Convert.FromBase64String(encStringPieces[1]);
if (mac.Length < 1)
{
return false;
}
}
break;
default:
return false;
}
}
catch
{
return false;
}
return true;
}
}

38
src/Core/Utilities/SpanExtensions.cs Normal file
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@ -0,0 +1,38 @@
namespace Bit.Core.Utilities;
public static class SpanExtensions
{
public static bool TrySplitBy(this ReadOnlySpan<char> input,
char splitChar, out ReadOnlySpan<char> chunk, out ReadOnlySpan<char> rest)
{
var splitIndex = input.IndexOf(splitChar);
if (splitIndex == -1)
{
chunk = default;
rest = input;
return false;
}
chunk = input[..splitIndex];
rest = input[++splitIndex..];
return true;
}
// Replace with the implementation from .NET 8 when we upgrade
// Ref: https://github.com/dotnet/runtime/issues/59466
public static int Count<T>(this ReadOnlySpan<T> span, T value)
where T : IEquatable<T>
{
var count = 0;
int pos;
while ((pos = span.IndexOf(value)) >= 0)
{
span = span[++pos..];
count++;
}
return count;
}
}