Add new logic for validating encrypted strings

src/Core/Enums/EncryptionType.cs

@@ -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,

src/Core/Utilities/EncryptedStringAttribute.cs

@@ -0,0 +1,185 @@
+using System.Buffers;
+using System.ComponentModel.DataAnnotations;
+using System.Diagnostics;
+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
+{
+    private static readonly Dictionary<EncryptionType, int> _encryptionTypeMap;
+
+    static EncryptedStringAttribute()
+    {
+        _encryptionTypeMap = new()
+        {
+            [EncryptionType.AesCbc256_B64] = 2,
+            [EncryptionType.AesCbc128_HmacSha256_B64] = 3,
+            [EncryptionType.AesCbc256_HmacSha256_B64] = 3,
+            [EncryptionType.Rsa2048_OaepSha256_B64] = 1,
+            [EncryptionType.Rsa2048_OaepSha1_B64] = 1,
+            [EncryptionType.Rsa2048_OaepSha256_HmacSha256_B64] = 2,
+            [EncryptionType.Rsa2048_OaepSha1_HmacSha256_B64] = 2,
+        };
+
+#if DEBUG
+        var enumValues = Enum.GetValues<EncryptionType>();
+        Debug.Assert(enumValues.Length == _encryptionTypeMap.Count, 
+            $"New {nameof(EncryptionType)} enums should be added to the {nameof(_encryptionTypeMap)}");
+#endif
+    }
+
+    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);
+            }
+
+            // Slow path (ish)
+            return IsValidCore(value.ToString());
+        }
+        catch
+        {
+            return false;
+        }
+    }
+
+    internal static bool IsValidCore(ReadOnlySpan<char> value)
+    {
+        if (!value.TrySplitBy('.', out var headerChunk, out var rest))
+        {
+            // We coundn'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 encryptionPiecesChunk = rest;
+
+            var pieces = 1;
+            var findIndex = encryptionPiecesChunk.IndexOf('|');
+
+            while(findIndex != -1)
+            {
+                pieces++;
+                encryptionPiecesChunk = encryptionPiecesChunk[++findIndex..];
+                findIndex = encryptionPiecesChunk.IndexOf('|');
+            }
+
+            if (pieces == 3)
+            {
+                return ValidatePieces(rest, _encryptionTypeMap[EncryptionType.AesCbc128_HmacSha256_B64]);
+            }
+            else
+            {
+                return ValidatePieces(rest, _encryptionTypeMap[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, _encryptionTypeMap[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 (!_encryptionTypeMap.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)
+            {
+                if (!IsValidBase64(rest))
+                {
+                    return false;
+                }
+
+                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;
+                }
+            }
+
+            requiredPieces--;
+        }
+
+        // No more parts are required, so check there are no extra parts
+        return rest.IndexOf('|') == -1;
+    }
+
+    private static bool IsValidBase64(ReadOnlySpan<char> input)
+    {
+        byte[]? pooledChunks = null;
+
+        // Ref: https://vcsjones.dev/stackalloc/
+        var byteBuffer = input.Length > 128
+            ? (pooledChunks = ArrayPool<byte>.Shared.Rent(input.Length * 2))
+            : stackalloc byte[256];
+
+        try
+        {
+            var successful = Convert.TryFromBase64Chars(input, byteBuffer, out var bytesWritten);
+            return successful && bytesWritten > 0;
+        }
+        finally
+        {
+            if (pooledChunks != null)
+            {
+                ArrayPool<byte>.Shared.Return(pooledChunks);
+            }
+        }
+    }
+}

src/Core/Utilities/EncryptedValueAttribute.cs

@@ -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;
-    }
-}

src/Core/Utilities/SpanExtensions.cs

@@ -0,0 +1,21 @@
+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;
+    }
+}

test/Core.Test/Utilities/EncryptedStringAttributeTests.cs

@@ -10,6 +10,20 @@ public class EncryptedStringAttributeTests
     [InlineData("aXY=|Y3Q=")] // Valid AesCbc256_B64
     [InlineData("aXY=|Y3Q=|cnNhQ3Q=")] // Valid AesCbc128_HmacSha256_B64
     [InlineData("Rsa2048_OaepSha256_B64.cnNhQ3Q=")]
+    [InlineData("0.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Valid AesCbc256_B64 as a number
+    [InlineData("AesCbc256_B64.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Valid AesCbc256_B64 as a number
+    [InlineData("1.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Valid AesCbc128_HmacSha256_B64 as a number
+    [InlineData("AesCbc128_HmacSha256_B64.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Valid AesCbc128_HmacSha256_B64 as a string
+    [InlineData("2.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Valid AesCbc256_HmacSha256_B64 as a number
+    [InlineData("AesCbc256_HmacSha256_B64.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Valid AesCbc256_HmacSha256_B64 as a string
+    [InlineData("3.QmFzZTY0UGFydA==")] // Valid Rsa2048_OaepSha256_B64 as a number
+    [InlineData("Rsa2048_OaepSha256_B64.QmFzZTY0UGFydA==")] // Valid Rsa2048_OaepSha256_B64 as a string
+    [InlineData("4.QmFzZTY0UGFydA==")] // Valid Rsa2048_OaepSha1_B64 as a number
+    [InlineData("Rsa2048_OaepSha1_B64.QmFzZTY0UGFydA==")] // Valid Rsa2048_OaepSha1_B64 as a string
+    [InlineData("5.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Valid Rsa2048_OaepSha256_HmacSha256_B64 as a number
+    [InlineData("Rsa2048_OaepSha256_HmacSha256_B64.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Valid Rsa2048_OaepSha256_HmacSha256_B64 as a string
+    [InlineData("6.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Valid Rsa2048_OaepSha1_HmacSha256_B64 as a number
+    [InlineData("Rsa2048_OaepSha1_HmacSha256_B64.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")]
     public void IsValid_ReturnsTrue_WhenValid(string input)
     {
         var sut = new EncryptedStringAttribute();
@@ -20,9 +34,10 @@ public class EncryptedStringAttributeTests
     }
 
     [Theory]
-    [InlineData("")]
+    [InlineData("")] // Empty string
-    [InlineData(".")]
+    [InlineData(".")] // Split Character but two empty parts
-    [InlineData("|")]
+    [InlineData("|")] // One encrypted part split character but empty parts
+    [InlineData("||")] // Two encrypted part split character but empty parts
     [InlineData("!|!")] // Invalid base 64
     [InlineData("Rsa2048_OaepSha1_HmacSha256_B64.1")] // Invalid length
     [InlineData("Rsa2048_OaepSha1_HmacSha256_B64.|")] // Empty iv & ct
@@ -31,6 +46,21 @@ public class EncryptedStringAttributeTests
     [InlineData("Rsa2048_OaepSha1_HmacSha256_B64.aXY=|Y3Q=|")] // Empty mac
     [InlineData("Rsa2048_OaepSha256_B64.1|2")] // Invalid length
     [InlineData("Rsa2048_OaepSha1_HmacSha256_B64.aXY=|")] // Empty mac
+    [InlineData("254.QmFzZTY0UGFydA==")] // Bad Encryption type number
+    [InlineData("0.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Invalid AesCbc256_B64 as a number
+    [InlineData("AesCbc256_B64.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Invalid AesCbc256_B64 as a number
+    [InlineData("1.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Invalid AesCbc128_HmacSha256_B64 as a number
+    [InlineData("AesCbc128_HmacSha256_B64.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Invalid AesCbc128_HmacSha256_B64 as a string
+    [InlineData("2.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Invalid AesCbc256_HmacSha256_B64 as a number
+    [InlineData("AesCbc256_HmacSha256_B64.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Invalid AesCbc256_HmacSha256_B64 as a string
+    [InlineData("3.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Invalid Rsa2048_OaepSha256_B64 as a number
+    [InlineData("Rsa2048_OaepSha256_B64.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Invalid Rsa2048_OaepSha256_B64 as a string
+    [InlineData("4.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Invalid Rsa2048_OaepSha1_B64 as a number
+    [InlineData("Rsa2048_OaepSha1_B64.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Invalid Rsa2048_OaepSha1_B64 as a string
+    [InlineData("5.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Invalid Rsa2048_OaepSha256_HmacSha256_B64 as a number
+    [InlineData("Rsa2048_OaepSha256_HmacSha256_B64.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Invalid Rsa2048_OaepSha256_HmacSha256_B64 as a string
+    [InlineData("6.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==")] // Invalid Rsa2048_OaepSha1_HmacSha256_B64 as a number
+    [InlineData("Rsa2048_OaepSha1_HmacSha256_B64.QmFzZTY0UGFydA==")] // Invalid Rsa2048_OaepSha1_HmacSha256_B64 as a string
     public void IsValid_ReturnsFalse_WhenInvalid(string input)
     {
         var sut = new EncryptedStringAttribute();