feat(OTP): [PM-18612] Change email OTP to six digits

* Change email OTP to 6 digits

* Added comment on base class

* Added tests

* Renamed tests.

* Fixed tests

* Renamed file to match class

src/Core/Auth/Identity/TokenProviders/EmailTokenProvider.cs

@@ -1,5 +1,6 @@
 using System.Text;
 using Bit.Core.Entities;
+using Bit.Core.Services;
 using Bit.Core.Utilities;
 using Microsoft.AspNetCore.Identity;
 using Microsoft.Extensions.Caching.Distributed;
@@ -7,6 +8,9 @@ using Microsoft.Extensions.DependencyInjection;
 
 namespace Bit.Core.Auth.Identity.TokenProviders;
 
+/// <summary>
+/// Generates and validates tokens for email OTPs.
+/// </summary>
 public class EmailTokenProvider : IUserTwoFactorTokenProvider<User>
 {
     private const string CacheKeyFormat = "EmailToken_{0}_{1}_{2}";
@@ -16,16 +20,25 @@ public class EmailTokenProvider : IUserTwoFactorTokenProvider<User>
 
     public EmailTokenProvider(
         [FromKeyedServices("persistent")]
-        IDistributedCache distributedCache)
+        IDistributedCache distributedCache,
+        IFeatureService featureService)
     {
         _distributedCache = distributedCache;
         _distributedCacheEntryOptions = new DistributedCacheEntryOptions
         {
             AbsoluteExpirationRelativeToNow = TimeSpan.FromMinutes(5)
         };
+        if (featureService.IsEnabled(FeatureFlagKeys.Otp6Digits))
+        {
+            TokenLength = 6;
+        }
+        else
+        {
+            TokenLength = 8;
+        }
     }
 
-    public int TokenLength { get; protected set; } = 8;
+    public int TokenLength { get; protected set; }
     public bool TokenAlpha { get; protected set; } = false;
     public bool TokenNumeric { get; protected set; } = true;
 

src/Core/Auth/Identity/TokenProviders/EmailTwoFactorTokenProvider.cs

@@ -4,19 +4,27 @@
 using Bit.Core.Auth.Enums;
 using Bit.Core.Auth.Models;
 using Bit.Core.Entities;
+using Bit.Core.Services;
 using Microsoft.AspNetCore.Identity;
 using Microsoft.Extensions.Caching.Distributed;
 using Microsoft.Extensions.DependencyInjection;
 
 namespace Bit.Core.Auth.Identity.TokenProviders;
 
+/// <summary>
+/// Generates tokens for email two-factor authentication.
+/// It inherits from the EmailTokenProvider class, which manages the persistence and validation of tokens, 
+/// and adds additional validation to ensure that 2FA is enabled for the user.
+/// </summary>
 public class EmailTwoFactorTokenProvider : EmailTokenProvider
 {
     public EmailTwoFactorTokenProvider(
         [FromKeyedServices("persistent")]
-        IDistributedCache distributedCache) :
+        IDistributedCache distributedCache,
-        base(distributedCache)
+        IFeatureService featureService) :
+        base(distributedCache, featureService)
     {
+        // This can be removed when the pm-18612-otp-6-digits feature flag is removed because the base implementation will match.
         TokenAlpha = false;
         TokenNumeric = true;
         TokenLength = 6;

src/Core/Constants.cs

@@ -124,6 +124,7 @@ public static class FeatureFlagKeys
     public const string SetInitialPasswordRefactor = "pm-16117-set-initial-password-refactor";
     public const string ChangeExistingPasswordRefactor = "pm-16117-change-existing-password-refactor";
     public const string RecoveryCodeLogin = "pm-17128-recovery-code-login";
+    public const string Otp6Digits = "pm-18612-otp-6-digits";
 
     /* Autofill Team */
     public const string IdpAutoSubmitLogin = "idp-auto-submit-login";

test/Core.Test/Auth/Identity/AuthenticationTwoFactorTokenProviderTests.cs

@@ -7,7 +7,7 @@ using Xunit;
 
 namespace Bit.Core.Test.Auth.Identity;
 
-public class AuthenticationTokenProviderTests : BaseTokenProviderTests<AuthenticatorTokenProvider>
+public class AuthenticationTwoFactorTokenProviderTests : BaseTwoFactorTokenProviderTests<AuthenticatorTokenProvider>
 {
     public override TwoFactorProviderType TwoFactorProviderType => TwoFactorProviderType.Authenticator;
 

test/Core.Test/Auth/Identity/BaseTwoFactorTokenProviderTests.cs

@@ -14,7 +14,7 @@ using Xunit;
 namespace Bit.Core.Test.Auth.Identity;
 
 [SutProviderCustomize]
-public abstract class BaseTokenProviderTests<T>
+public abstract class BaseTwoFactorTokenProviderTests<T>
     where T : IUserTwoFactorTokenProvider<User>
 {
     public abstract TwoFactorProviderType TwoFactorProviderType { get; }

test/Core.Test/Auth/Identity/DuoUniversalTwoFactorTokenProviderTests.cs

@@ -12,7 +12,7 @@ using Duo = DuoUniversal;
 
 namespace Bit.Core.Test.Auth.Identity;
 
-public class DuoUniversalTwoFactorTokenProviderTests : BaseTokenProviderTests<DuoUniversalTokenProvider>
+public class DuoUniversalTwoFactorTokenProviderTests : BaseTwoFactorTokenProviderTests<DuoUniversalTokenProvider>
 {
     private readonly IDuoUniversalTokenService _duoUniversalTokenService = Substitute.For<IDuoUniversalTokenService>();
     public override TwoFactorProviderType TwoFactorProviderType => TwoFactorProviderType.Duo;

test/Core.Test/Auth/Identity/EmailTokenProviderTests.cs

@@ -0,0 +1,68 @@
+using Bit.Core;
+using Bit.Core.Auth.Identity.TokenProviders;
+using Bit.Core.Entities;
+using Bit.Core.Services;
+using Bit.Test.Common.AutoFixture.Attributes;
+using Microsoft.AspNetCore.Identity;
+using Microsoft.Extensions.Caching.Distributed;
+using Microsoft.Extensions.Logging;
+using Microsoft.Extensions.Options;
+using NSubstitute;
+using Xunit;
+
+[SutProviderCustomize]
+public class EmailTokenProviderTests
+{
+    private readonly IDistributedCache _cache;
+
+    public EmailTokenProviderTests()
+    {
+        _cache = Substitute.For<IDistributedCache>();
+    }
+
+    [Theory]
+    [BitAutoData]
+    public async Task GenerateAsync_GeneratesSixDigitToken_WhenFeatureFlagIsEnabled(User user)
+    {
+        // Arrange
+        var purpose = "test-purpose";
+        var featureService = Substitute.For<IFeatureService>();
+        featureService.IsEnabled(FeatureFlagKeys.Otp6Digits).Returns(true);
+        var tokenProvider = new EmailTokenProvider(_cache, featureService);
+
+        // Act
+        var code = await tokenProvider.GenerateAsync(purpose, SubstituteUserManager(), user);
+
+        // Assert
+        Assert.Equal(6, code.Length);
+    }
+
+    [Theory]
+    [BitAutoData]
+    public async Task GenerateAsync_GeneratesEightDigitToken_WhenFeatureFlagIsDisabled(User user)
+    {
+        // Arrange
+        var purpose = "test-purpose";
+        var featureService = Substitute.For<IFeatureService>();
+        featureService.IsEnabled(FeatureFlagKeys.Otp6Digits).Returns(false);
+        var tokenProvider = new EmailTokenProvider(_cache, featureService);
+        // Act
+        var code = await tokenProvider.GenerateAsync(purpose, SubstituteUserManager(), user);
+
+        // Assert
+        Assert.Equal(8, code.Length);
+    }
+
+    protected static UserManager<User> SubstituteUserManager()
+    {
+        return new UserManager<User>(Substitute.For<IUserStore<User>>(),
+            Substitute.For<IOptions<IdentityOptions>>(),
+            Substitute.For<IPasswordHasher<User>>(),
+            Enumerable.Empty<IUserValidator<User>>(),
+            Enumerable.Empty<IPasswordValidator<User>>(),
+            Substitute.For<ILookupNormalizer>(),
+            Substitute.For<IdentityErrorDescriber>(),
+            Substitute.For<IServiceProvider>(),
+            Substitute.For<ILogger<UserManager<User>>>());
+    }
+}

test/Core.Test/Auth/Identity/EmailTwoFactorTokenProviderTests.cs

@@ -1,13 +1,15 @@
 using Bit.Core.Auth.Enums;
 using Bit.Core.Auth.Identity.TokenProviders;
 using Bit.Core.Entities;
+using Bit.Core.Services;
 using Bit.Test.Common.AutoFixture;
 using Bit.Test.Common.AutoFixture.Attributes;
+using NSubstitute;
 using Xunit;
 
 namespace Bit.Core.Test.Auth.Identity;
 
-public class EmailTwoFactorTokenProviderTests : BaseTokenProviderTests<EmailTwoFactorTokenProvider>
+public class EmailTwoFactorTokenProviderTests : BaseTwoFactorTokenProviderTests<EmailTwoFactorTokenProvider>
 {
     public override TwoFactorProviderType TwoFactorProviderType => TwoFactorProviderType.Email;
 
@@ -42,4 +44,48 @@ public class EmailTwoFactorTokenProviderTests : BaseTokenProviderTests<EmailTwoF
     {
         await base.RunCanGenerateTwoFactorTokenAsync(metaData, expectedResponse, user, sutProvider);
     }
+
+    [Theory]
+    [BitAutoData]
+    public async Task GenerateAsync_ShouldReturnSixDigitToken_WithFeatureFlagEnabled(
+        User user, SutProvider<EmailTwoFactorTokenProvider> sutProvider)
+    {
+        // Arrange
+        user.TwoFactorProviders = GetTwoFactorEmailProvidersJson();
+        sutProvider.GetDependency<IFeatureService>()
+            .IsEnabled(FeatureFlagKeys.Otp6Digits)
+            .Returns(true);
+
+        // Act
+        var token = await sutProvider.Sut.GenerateAsync("purpose", SubstituteUserManager(), user);
+
+        // Assert
+        Assert.NotNull(token);
+        Assert.Equal(6, token.Length);
+    }
+
+    [Theory]
+    [BitAutoData]
+    public async Task GenerateAsync_ShouldReturnSixDigitToken_WithFeatureFlagDisabled(
+        User user, SutProvider<EmailTwoFactorTokenProvider> sutProvider)
+    {
+        // Arrange
+        user.TwoFactorProviders = GetTwoFactorEmailProvidersJson();
+        sutProvider.GetDependency<IFeatureService>()
+            .IsEnabled(FeatureFlagKeys.Otp6Digits)
+            .Returns(false);
+
+        // Act
+        var token = await sutProvider.Sut.GenerateAsync("purpose", SubstituteUserManager(), user);
+
+        // Assert
+        Assert.NotNull(token);
+        Assert.Equal(6, token.Length);
+    }
+
+    private string GetTwoFactorEmailProvidersJson()
+    {
+        return
+            "{\"1\":{\"Enabled\":true,\"MetaData\":{\"Email\":\"test@email.com\"}}}";
+    }
 }