[PM-31191] New Argon2id configuration into prelogin

src/Core/KeyManagement/Kdf/KdfConstants.cs

@@ -1,11 +1,16 @@
 namespace Bit.Core.KeyManagement.Kdf;
 
+/// <summary>
+/// These defaults are used by the prelogin enumeration-protection pool in
+/// Identity/AccountsController. Changes here will affect prelogin responses
+/// for non-existent users. See AccountsControllerTests for coverage.
+/// </summary>
 public static class KdfConstants
 {
     public static readonly RangeConstant PBKDF2_ITERATIONS = new(600_000, 2_000_000, 600_000);
 
-    public static readonly RangeConstant ARGON2_ITERATIONS = new(2, 10, 3);
-    public static readonly RangeConstant ARGON2_MEMORY = new(15, 1024, 64);
+    public static readonly RangeConstant ARGON2_ITERATIONS = new(2, 10, 6);
+    public static readonly RangeConstant ARGON2_MEMORY = new(15, 1024, 32);
     public static readonly RangeConstant ARGON2_PARALLELISM = new(1, 16, 4);
 }
 

src/Identity/Controllers/AccountsController.cs

@@ -34,7 +34,7 @@ public class AccountsController : Controller
     private readonly IDataProtectorTokenFactory<RegistrationEmailVerificationTokenable> _registrationEmailVerificationTokenDataFactory;
 
     private readonly byte[]? _defaultKdfHmacKey = null;
-    private static readonly List<UserKdfInformation> _defaultKdfResults =
+    internal static readonly List<UserKdfInformation> _defaultKdfResults =
     [
         // The first result (index 0) should always return the "normal" default.
         new()
@@ -60,6 +60,14 @@ public class AccountsController : Controller
             KdfIterations = 5_000,
         },
         new()
+        {
+            Kdf = KdfType.Argon2id,
+            KdfIterations = 3,
+            KdfMemory = 64,
+            KdfParallelism = 4,
+        },
+        // Mobile-friendly Argon2id default, tuned for iOS memory constraints.
+        new()
         {
             Kdf = KdfType.Argon2id,
             KdfIterations = KdfConstants.ARGON2_ITERATIONS.Default,

test/Identity.Test/Controllers/AccountsControllerTests.cs

@@ -207,11 +207,7 @@ public async Task PostPasswordPrelogin_WhenUserDoesNotExistAndDefaultKdfHmacKeyI
 
         _userRepository.GetKdfInformationByEmailAsync(Arg.Any<string>()).Returns(Task.FromResult<UserKdfInformation?>(null));
 
-        var fieldInfo = typeof(AccountsController).GetField("_defaultKdfResults", BindingFlags.NonPublic | BindingFlags.Static);
-        if (fieldInfo == null)
-            throw new InvalidOperationException("Field '_defaultKdfResults' not found.");
-
-        var defaultKdfResults = (List<UserKdfInformation>)fieldInfo.GetValue(null)!;
+        var defaultKdfResults = AccountsController._defaultKdfResults;
 
         var expectedIndex = GetExpectedKdfIndex(email, defaultKey, defaultKdfResults);
         var expectedKdf = defaultKdfResults[expectedIndex];
@@ -1249,6 +1245,42 @@ public void RegisterFinishRequestModel_Validate_Throws_WhenAuthHashAndRootHashMi
         Assert.Contains("MasterPasswordHash", mismatchResult.MemberNames);
     }
 
+    [Fact]
+    public void DefaultKdfResults_ShouldContainExpectedEntries()
+    {
+        var pool = AccountsController._defaultKdfResults;
+
+        Assert.Equal(6, pool.Count);
+
+        // Index 0 — PBKDF2 600k (normal default)
+        Assert.Equal(KdfType.PBKDF2_SHA256, pool[0].Kdf);
+        Assert.Equal(600_000, pool[0].KdfIterations);
+
+        // Index 1 — PBKDF2 600k (weight duplicate)
+        Assert.Equal(KdfType.PBKDF2_SHA256, pool[1].Kdf);
+        Assert.Equal(600_000, pool[1].KdfIterations);
+
+        // Index 2 — PBKDF2 100k (historical)
+        Assert.Equal(KdfType.PBKDF2_SHA256, pool[2].Kdf);
+        Assert.Equal(100_000, pool[2].KdfIterations);
+
+        // Index 3 — PBKDF2 5k (historical)
+        Assert.Equal(KdfType.PBKDF2_SHA256, pool[3].Kdf);
+        Assert.Equal(5_000, pool[3].KdfIterations);
+
+        // Index 4 — Argon2id 3 iterations, 64MB, 4 parallelism (historical)
+        Assert.Equal(KdfType.Argon2id, pool[4].Kdf);
+        Assert.Equal(3, pool[4].KdfIterations);
+        Assert.Equal(64, pool[4].KdfMemory);
+        Assert.Equal(4, pool[4].KdfParallelism);
+
+        // Index 5 — Argon2id 6 iterations, 32MB, 4 parallelism
+        Assert.Equal(KdfType.Argon2id, pool[5].Kdf);
+        Assert.Equal(6, pool[5].KdfIterations);
+        Assert.Equal(32, pool[5].KdfMemory);
+        Assert.Equal(4, pool[5].KdfParallelism);
+    }
+
     private void SetDefaultKdfHmacKey(byte[]? newKey)
     {
         var fieldInfo = typeof(AccountsController).GetField("_defaultKdfHmacKey", BindingFlags.NonPublic | BindingFlags.Instance);