feat(auth-validator): [Auth/PM-22975] Client Version Validator (#6588)

* feat(auth-validator): [PM-22975] Client Version Validator - Implementation. * test(auth-validator): [PM-22975] Client Version Validator - Added tests.
2026-02-24 08:33:06 +00:00 · 2026-02-23 10:00:10 -05:00
parent b5554c6030
commit 3dbd17f61d
27 changed files with 732 additions and 83 deletions
--- a/test/Api.IntegrationTest/Factories/ApiApplicationFactory.cs
+++ b/test/Api.IntegrationTest/Factories/ApiApplicationFactory.cs
@@ -3,6 +3,7 @@ using Bit.Core.Auth.Models.Api.Request.Accounts;
 using Bit.Core.Enums;
 using Bit.IntegrationTestCommon;
 using Bit.IntegrationTestCommon.Factories;
+using Bit.Test.Common.Constants;
 using Microsoft.AspNetCore.Authentication.JwtBearer;
 using Microsoft.AspNetCore.TestHost;
 using Xunit;
@@ -66,10 +67,10 @@ public class ApiApplicationFactory : WebApplicationFactoryBase<Startup>
                KdfIterations = AuthConstants.PBKDF2_ITERATIONS.Default,
                UserAsymmetricKeys = new KeysRequestModel()
                {
-                    PublicKey = "public_key",
-                    EncryptedPrivateKey = "private_key"
+                    PublicKey = TestEncryptionConstants.PublicKey,
+                    EncryptedPrivateKey = TestEncryptionConstants.AES256_CBC_HMAC_Encstring
                },
-                UserSymmetricKey = "sym_key",
+                UserSymmetricKey = TestEncryptionConstants.AES256_CBC_HMAC_Encstring,
            });

        return await _identityApplicationFactory.TokenFromPasswordAsync(email, masterPasswordHash);
--- a/test/Common/Constants/TestEncryptionConstants.cs
+++ b/test/Common/Constants/TestEncryptionConstants.cs
@@ -0,0 +1,24 @@
+namespace Bit.Test.Common.Constants;
+
+public static class TestEncryptionConstants
+{
+
+    // Simple stubs for different encrypted string versions
+    [Obsolete]
+    public const string AES256_CBC_B64_Encstring = "0.stub";
+    public const string AES256_CBC_HMAC_EmptySuffix = "2.";
+    // Intended for use as a V1 encrypted string, accepted by validators
+    public const string AES256_CBC_HMAC_Encstring = "2.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==";
+    public const string RSA2048_OAEPSHA1_B64_Encstring = "4.stub";
+    public const string XCHACHA20POLY1305_B64_Encstring = "7.stub";
+
+    // Public key test placeholder
+    public const string PublicKey = "pk_test";
+
+    // V2-style values used across tests
+    // Private key indicating v2 (used in multiple tests to mark v2 state)
+    public const string V2PrivateKey = "7.cose";
+    // Wrapped signing key and verifying key values from real tests
+    public const string V2WrappedSigningKey = "7.cose_signing";
+    public const string V2VerifyingKey = "vk";
+}
--- a/test/Core.Test/AutoFixture/GlobalSettingsFixtures.cs
+++ b/test/Core.Test/AutoFixture/GlobalSettingsFixtures.cs
@@ -3,7 +3,6 @@ using System.Text;
 using AutoFixture;
 using AutoFixture.Kernel;
 using AutoFixture.Xunit2;
-using Bit.Core;
 using Bit.Core.Test.Helpers.Factories;
 using Microsoft.AspNetCore.DataProtection;
 using NSubstitute;
@@ -36,11 +35,11 @@ public class GlobalSettingsBuilder : ISpecimenBuilder
            var dataProtector = Substitute.For<IDataProtector>();
            dataProtector.Unprotect(Arg.Any<byte[]>())
                .Returns(data =>
-                    Encoding.UTF8.GetBytes(Constants.DatabaseFieldProtectedPrefix +
+                    Encoding.UTF8.GetBytes(Core.Constants.DatabaseFieldProtectedPrefix +
                                           Encoding.UTF8.GetString((byte[])data[0])));

            var dataProtectionProvider = Substitute.For<IDataProtectionProvider>();
-            dataProtectionProvider.CreateProtector(Constants.DatabaseFieldProtectorPurpose)
+            dataProtectionProvider.CreateProtector(Core.Constants.DatabaseFieldProtectorPurpose)
                .Returns(dataProtector);

            return dataProtectionProvider;
--- a/test/Core.Test/KeyManagement/Utilities/EncryptionParsingTests.cs
+++ b/test/Core.Test/KeyManagement/Utilities/EncryptionParsingTests.cs
@@ -0,0 +1,40 @@
+using Bit.Core.Enums;
+using Bit.Core.KeyManagement.Utilities;
+using Bit.Test.Common.Constants;
+using Xunit;
+
+namespace Bit.Core.Test.KeyManagement.Utilities;
+
+public class EncryptionParsingTests
+{
+    [Fact]
+    public void GetEncryptionType_WithNull_ThrowsArgumentNullException()
+    {
+        Assert.Throws<ArgumentNullException>(() => EncryptionParsing.GetEncryptionType(null));
+    }
+
+    [Theory]
+    [InlineData("2")] // missing '.' separator
+    [InlineData("abc.def")] // non-numeric prefix
+    [InlineData("8.any")] // undefined enum value
+    [InlineData("255.any")] // out of defined enum range
+    public void GetEncryptionType_WithInvalidString_ThrowsArgumentException(string input)
+    {
+        Assert.Throws<ArgumentException>(() => EncryptionParsing.GetEncryptionType(input));
+    }
+
+    [Theory]
+    [InlineData(TestEncryptionConstants.AES256_CBC_B64_Encstring, EncryptionType.AesCbc256_B64)]
+    [InlineData(TestEncryptionConstants.AES256_CBC_HMAC_Encstring, EncryptionType.AesCbc256_HmacSha256_B64)]
+    [InlineData(TestEncryptionConstants.RSA2048_OAEPSHA1_B64_Encstring, EncryptionType.Rsa2048_OaepSha1_B64)]
+    [InlineData(TestEncryptionConstants.V2PrivateKey, EncryptionType.XChaCha20Poly1305_B64)]
+    [InlineData(TestEncryptionConstants.V2WrappedSigningKey, EncryptionType.XChaCha20Poly1305_B64)]
+    [InlineData(TestEncryptionConstants.AES256_CBC_HMAC_EmptySuffix, EncryptionType.AesCbc256_HmacSha256_B64)] // empty suffix still valid
+    [InlineData(TestEncryptionConstants.XCHACHA20POLY1305_B64_Encstring, EncryptionType.XChaCha20Poly1305_B64)]
+    public void GetEncryptionType_WithValidString_ReturnsExpected(string input, EncryptionType expected)
+    {
+        var result = EncryptionParsing.GetEncryptionType(input);
+        Assert.Equal(expected, result);
+    }
+}
+
--- a/test/Events.IntegrationTest/EventsApplicationFactory.cs
+++ b/test/Events.IntegrationTest/EventsApplicationFactory.cs
@@ -3,6 +3,7 @@ using Bit.Core.Auth.Models.Api.Request.Accounts;
 using Bit.Core.Enums;
 using Bit.IntegrationTestCommon;
 using Bit.IntegrationTestCommon.Factories;
+using Bit.Test.Common.Constants;
 using Microsoft.AspNetCore.Authentication.JwtBearer;
 using Microsoft.AspNetCore.Hosting;
 using Microsoft.AspNetCore.TestHost;
@@ -58,10 +59,10 @@ public class EventsApplicationFactory : WebApplicationFactoryBase<Startup>
                KdfIterations = AuthConstants.PBKDF2_ITERATIONS.Default,
                UserAsymmetricKeys = new KeysRequestModel()
                {
-                    PublicKey = "public_key",
-                    EncryptedPrivateKey = "private_key"
+                    PublicKey = TestEncryptionConstants.PublicKey,
+                    EncryptedPrivateKey = TestEncryptionConstants.AES256_CBC_HMAC_Encstring
                },
-                UserSymmetricKey = "sym_key",
+                UserSymmetricKey = TestEncryptionConstants.AES256_CBC_HMAC_Encstring,
            });

        return await _identityApplicationFactory.TokenFromPasswordAsync(email, masterPasswordHash);
--- a/test/Identity.IntegrationTest/Endpoints/IdentityServerSsoTests.cs
+++ b/test/Identity.IntegrationTest/Endpoints/IdentityServerSsoTests.cs
@@ -15,7 +15,10 @@ using Bit.Core.Enums;
 using Bit.Core.Models.Data;
 using Bit.Core.Repositories;
 using Bit.Core.Utilities;
+using Bit.Identity.IdentityServer;
+using Bit.Identity.IdentityServer.RequestValidators;
 using Bit.IntegrationTestCommon.Factories;
+using Bit.Test.Common.Constants;
 using Bit.Test.Common.Helpers;
 using Duende.IdentityModel;
 using Duende.IdentityServer.Models;
@@ -310,8 +313,8 @@ public class IdentityServerSsoTests
        var user = await factory.Services.GetRequiredService<IUserRepository>().GetByEmailAsync(TestEmail);
        Assert.NotNull(user);

-        const string expectedPrivateKey = "2.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==";
-        const string expectedUserKey = "2.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==";
+        const string expectedPrivateKey = TestEncryptionConstants.AES256_CBC_HMAC_Encstring;
+        const string expectedUserKey = TestEncryptionConstants.AES256_CBC_HMAC_Encstring;

        var device = await deviceRepository.CreateAsync(new Device
        {
@@ -320,7 +323,7 @@ public class IdentityServerSsoTests
            Name = "Thing",
            UserId = user.Id,
            EncryptedPrivateKey = expectedPrivateKey,
-            EncryptedPublicKey = "2.QmFzZTY0UGFydA==|QmFzZTY0UGFydA==|QmFzZTY0UGFydA==",
+            EncryptedPublicKey = TestEncryptionConstants.AES256_CBC_HMAC_Encstring,
            EncryptedUserKey = expectedUserKey,
        });

@@ -540,21 +543,70 @@ public class IdentityServerSsoTests
        }, challenge, trustedDeviceEnabled);

        await configureFactory(factory);
-        var context = await factory.Server.PostAsync("/connect/token", new FormUrlEncodedContent(new Dictionary<string, string>
+        var context = await factory.Server.PostAsync("/connect/token", new FormUrlEncodedContent(
+            new Dictionary<string, string>
+            {
+                { "scope", "api offline_access" },
+                { "client_id", "web" },
+                { "deviceType", "10" },
+                { "deviceIdentifier", "test_id" },
+                { "deviceName", "firefox" },
+                { "twoFactorToken", "TEST" },
+                { "twoFactorProvider", "5" }, // RememberMe Provider
+                { "twoFactorRemember", "0" },
+                { "grant_type", "authorization_code" },
+                { "code", "test_code" },
+                { "code_verifier", challenge },
+                { "redirect_uri", "https://localhost:8080/sso-connector.html" }
+            }));
+
+        // If this fails, surface detailed error information to aid debugging
+        if (context.Response.StatusCode != StatusCodes.Status200OK)
        {
-            { "scope", "api offline_access" },
-            { "client_id", "web" },
-            { "deviceType", "10" },
-            { "deviceIdentifier", "test_id" },
-            { "deviceName", "firefox" },
-            { "twoFactorToken", "TEST"},
-            { "twoFactorProvider", "5" }, // RememberMe Provider
-            { "twoFactorRemember", "0" },
-            { "grant_type", "authorization_code" },
-            { "code", "test_code" },
-            { "code_verifier", challenge },
-            { "redirect_uri", "https://localhost:8080/sso-connector.html" }
-        }));
+            string contentType = context.Response.ContentType ?? string.Empty;
+            string rawBody = "<unreadable>";
+            try
+            {
+                if (context.Response.Body.CanSeek)
+                {
+                    context.Response.Body.Position = 0;
+                }
+                using var reader = new StreamReader(context.Response.Body, leaveOpen: true);
+                rawBody = await reader.ReadToEndAsync();
+            }
+            catch
+            {
+                // leave rawBody as unreadable
+            }
+
+            string? error = null;
+            string? errorDesc = null;
+            string? errorModelMsg = null;
+            try
+            {
+                using var doc = JsonDocument.Parse(rawBody);
+                var root = doc.RootElement;
+                if (root.TryGetProperty("error", out var e)) error = e.GetString();
+                if (root.TryGetProperty("error_description", out var ed)) errorDesc = ed.GetString();
+                if (root.TryGetProperty("ErrorModel", out var em) && em.ValueKind == JsonValueKind.Object)
+                {
+                    if (em.TryGetProperty("Message", out var msg) && msg.ValueKind == JsonValueKind.String)
+                    {
+                        errorModelMsg = msg.GetString();
+                    }
+                }
+            }
+            catch
+            {
+                // Not JSON, continue with raw body
+            }
+
+            var message =
+                $"Unexpected status {context.Response.StatusCode}." +
+                $" error='{error}' error_description='{errorDesc}' ErrorModel.Message='{errorModelMsg}'" +
+                $" ContentType='{contentType}' RawBody='{rawBody}'";
+            Assert.Fail(message);
+        }

        // Only calls that result in a 200 OK should call this helper
        Assert.Equal(StatusCodes.Status200OK, context.Response.StatusCode);
@@ -570,6 +622,13 @@ public class IdentityServerSsoTests
    {
        var factory = new IdentityApplicationFactory();

+        // Bypass client version gating to isolate SSO test behavior
+        factory.SubstituteService<IClientVersionValidator>(svc =>
+        {
+            svc.Validate(Arg.Any<User>(), Arg.Any<CustomValidatorRequestContext>())
+                .Returns(true);
+        });
+
        var authorizationCode = new AuthorizationCode
        {
            ClientId = "web",
@@ -584,6 +643,7 @@ public class IdentityServerSsoTests

        factory.SubstituteService<IAuthorizationCodeStore>(service =>
        {
+            // Return our pre-built authorization code regardless of handle representation
            service.GetAuthorizationCodeAsync("test_code")
                .Returns(authorizationCode);
        });
@@ -597,10 +657,10 @@ public class IdentityServerSsoTests
                KdfIterations = AuthConstants.PBKDF2_ITERATIONS.Default,
                UserAsymmetricKeys = new KeysRequestModel()
                {
-                    PublicKey = "public_key",
-                    EncryptedPrivateKey = "private_key"
+                    PublicKey = TestEncryptionConstants.PublicKey,
+                    EncryptedPrivateKey = TestEncryptionConstants.AES256_CBC_HMAC_Encstring // v1-format so parsing succeeds and user is treated as v1
                },
-                UserSymmetricKey = "sym_key",
+                UserSymmetricKey = TestEncryptionConstants.AES256_CBC_HMAC_Encstring,
            });

        var organizationRepository = factory.Services.GetRequiredService<IOrganizationRepository>();
--- a/test/Identity.IntegrationTest/Endpoints/IdentityServerTests.cs
+++ b/test/Identity.IntegrationTest/Endpoints/IdentityServerTests.cs
@@ -9,11 +9,14 @@ using Bit.Core.Enums;
 using Bit.Core.Platform.Installations;
 using Bit.Core.Repositories;
 using Bit.Core.Test.Auth.AutoFixture;
+using Bit.Identity.IdentityServer;
+using Bit.Identity.IdentityServer.RequestValidators;
 using Bit.IntegrationTestCommon.Factories;
 using Bit.Test.Common.AutoFixture.Attributes;
 using Bit.Test.Common.Helpers;
 using Microsoft.AspNetCore.TestHost;
 using Microsoft.EntityFrameworkCore;
+using NSubstitute;
 using Xunit;

 namespace Bit.Identity.IntegrationTest.Endpoints;
@@ -36,6 +39,14 @@ public class IdentityServerTests : IClassFixture<IdentityApplicationFactory>
    public IdentityServerTests(IdentityApplicationFactory factory)
    {
        _factory = factory;
+
+        // Bypass client version gating to isolate SSO test behavior
+        _factory.SubstituteService<IClientVersionValidator>(svc =>
+        {
+            svc.Validate(Arg.Any<User>(), Arg.Any<CustomValidatorRequestContext>())
+                .Returns(true);
+        });
+
        ReinitializeDbForTests(_factory);
    }

--- a/test/Identity.IntegrationTest/Endpoints/IdentityServerTwoFactorTests.cs
+++ b/test/Identity.IntegrationTest/Endpoints/IdentityServerTwoFactorTests.cs
@@ -387,10 +387,10 @@ public class IdentityServerTwoFactorTests : IClassFixture<IdentityApplicationFac
                KdfIterations = AuthConstants.PBKDF2_ITERATIONS.Default,
                UserAsymmetricKeys = new KeysRequestModel()
                {
-                    PublicKey = "public_key",
-                    EncryptedPrivateKey = "private_key"
+                    PublicKey = Bit.Test.Common.Constants.TestEncryptionConstants.PublicKey,
+                    EncryptedPrivateKey = Bit.Test.Common.Constants.TestEncryptionConstants.AES256_CBC_HMAC_Encstring
                },
-                UserSymmetricKey = "sym_key",
+                UserSymmetricKey = Bit.Test.Common.Constants.TestEncryptionConstants.AES256_CBC_HMAC_Encstring,
            });
        Assert.NotNull(user);

@@ -441,10 +441,10 @@ public class IdentityServerTwoFactorTests : IClassFixture<IdentityApplicationFac
                KdfIterations = AuthConstants.PBKDF2_ITERATIONS.Default,
                UserAsymmetricKeys = new KeysRequestModel()
                {
-                    PublicKey = "public_key",
-                    EncryptedPrivateKey = "private_key"
+                    PublicKey = Bit.Test.Common.Constants.TestEncryptionConstants.PublicKey,
+                    EncryptedPrivateKey = Bit.Test.Common.Constants.TestEncryptionConstants.AES256_CBC_HMAC_Encstring
                },
-                UserSymmetricKey = "sym_key",
+                UserSymmetricKey = Bit.Test.Common.Constants.TestEncryptionConstants.AES256_CBC_HMAC_Encstring,
            });

        var userService = factory.GetService<IUserService>();
--- a/test/Identity.IntegrationTest/Login/ClientVersionGateTests.cs
+++ b/test/Identity.IntegrationTest/Login/ClientVersionGateTests.cs
@@ -0,0 +1,149 @@
+using System.Text.Json;
+using Bit.Core.Auth.Models.Api.Request.Accounts;
+using Bit.Core.KeyManagement.Enums;
+using Bit.Core.Test.Auth.AutoFixture;
+using Bit.IntegrationTestCommon.Factories;
+using Bit.Test.Common.AutoFixture.Attributes;
+using Bit.Test.Common.Constants;
+using Microsoft.EntityFrameworkCore;
+using Xunit;
+
+namespace Bit.Identity.IntegrationTest.Login;
+
+public class ClientVersionGateTests : IClassFixture<IdentityApplicationFactory>
+{
+    private readonly IdentityApplicationFactory _factory;
+    private const string DefaultEncryptedString = "2.3Uk+WNBIoU5xzmVFNcoWzz==|1MsPIYuRfdOHfu/0uY6H2Q==|/98sp4wb6pHP1VTZ9JcNCYgQjEUMFPlqJgCwRk1YXKg=";
+
+    public ClientVersionGateTests(IdentityApplicationFactory factory)
+    {
+        _factory = factory;
+        ReinitializeDbForTests(_factory);
+    }
+
+    [Theory, BitAutoData, RegisterFinishRequestModelCustomize]
+    public async Task TokenEndpoint_GrantTypePassword_V2User_OnOldClientVersion_Blocked(RegisterFinishRequestModel requestModel)
+    {
+        NormalizeEncryptedStrings(requestModel);
+        var localFactory = new IdentityApplicationFactory
+        {
+            UseMockClientVersionValidator = false
+        };
+        var server = localFactory.Server;
+        var user = await localFactory.RegisterNewIdentityFactoryUserAsync(requestModel);
+
+        // Make user V2: set private key to COSE and add signature key pair
+        var db = localFactory.GetDatabaseContext();
+        var efUser = await db.Users.FirstAsync(u => u.Email == user.Email);
+        efUser.PrivateKey = TestEncryptionConstants.V2PrivateKey;
+        efUser.SecurityVersion = 2;
+        db.UserSignatureKeyPairs.Add(new Bit.Infrastructure.EntityFramework.Models.UserSignatureKeyPair
+        {
+            Id = Core.Utilities.CoreHelpers.GenerateComb(),
+            UserId = efUser.Id,
+            SignatureAlgorithm = SignatureAlgorithm.Ed25519,
+            SigningKey = TestEncryptionConstants.V2WrappedSigningKey,
+            VerifyingKey = TestEncryptionConstants.V2VerifyingKey,
+        });
+        await db.SaveChangesAsync();
+
+        var context = await server.PostAsync("/connect/token",
+            new FormUrlEncodedContent(new Dictionary<string, string>
+            {
+                { "scope", "api offline_access" },
+                { "client_id", "web" },
+                { "deviceType", "2" },
+                { "deviceIdentifier", IdentityApplicationFactory.DefaultDeviceIdentifier },
+                { "deviceName", "firefox" },
+                { "grant_type", "password" },
+                { "username", user.Email },
+                { "password", requestModel.MasterPasswordHash },
+            }),
+            http =>
+            {
+                http.Request.Headers.Append("Bitwarden-Client-Version", "2025.10.0");
+            });
+
+        Assert.Equal(StatusCodes.Status400BadRequest, context.Response.StatusCode);
+        var errorBody = await Bit.Test.Common.Helpers.AssertHelper.AssertResponseTypeIs<JsonDocument>(context);
+        var error = Bit.Test.Common.Helpers.AssertHelper.AssertJsonProperty(errorBody.RootElement, "ErrorModel", JsonValueKind.Object);
+        var message = Bit.Test.Common.Helpers.AssertHelper.AssertJsonProperty(error, "Message", JsonValueKind.String).GetString();
+        Assert.Equal("Please update your app to continue using Bitwarden", message);
+    }
+
+    [Theory, BitAutoData, RegisterFinishRequestModelCustomize]
+    public async Task TokenEndpoint_GrantTypePassword_V2User_OnMinClientVersion_Succeeds(RegisterFinishRequestModel requestModel)
+    {
+        NormalizeEncryptedStrings(requestModel);
+        var localFactory = new IdentityApplicationFactory
+        {
+            UseMockClientVersionValidator = false
+        };
+        var server = localFactory.Server;
+        var user = await localFactory.RegisterNewIdentityFactoryUserAsync(requestModel);
+
+        // Make user V2
+        var db = localFactory.GetDatabaseContext();
+        var efUser = await db.Users.FirstAsync(u => u.Email == user.Email);
+        efUser.PrivateKey = TestEncryptionConstants.V2PrivateKey;
+        efUser.SecurityVersion = 2;
+        db.UserSignatureKeyPairs.Add(new Bit.Infrastructure.EntityFramework.Models.UserSignatureKeyPair
+        {
+            Id = Core.Utilities.CoreHelpers.GenerateComb(),
+            UserId = efUser.Id,
+            SignatureAlgorithm = SignatureAlgorithm.Ed25519,
+            SigningKey = TestEncryptionConstants.V2WrappedSigningKey,
+            VerifyingKey = TestEncryptionConstants.V2VerifyingKey,
+        });
+        await db.SaveChangesAsync();
+
+        var context = await server.PostAsync("/connect/token",
+            new FormUrlEncodedContent(new Dictionary<string, string>
+            {
+                { "scope", "api offline_access" },
+                { "client_id", "web" },
+                { "deviceType", "2" },
+                { "deviceIdentifier", IdentityApplicationFactory.DefaultDeviceIdentifier },
+                { "deviceName", "firefox" },
+                { "grant_type", "password" },
+                { "username", user.Email },
+                { "password", requestModel.MasterPasswordHash },
+            }),
+            http =>
+            {
+                http.Request.Headers.Append("Bitwarden-Client-Version", "2025.11.0");
+            });
+
+        Assert.Equal(StatusCodes.Status200OK, context.Response.StatusCode);
+    }
+
+    private void ReinitializeDbForTests(IdentityApplicationFactory factory)
+    {
+        var databaseContext = factory.GetDatabaseContext();
+        databaseContext.Policies.RemoveRange(databaseContext.Policies);
+        databaseContext.OrganizationUsers.RemoveRange(databaseContext.OrganizationUsers);
+        databaseContext.Organizations.RemoveRange(databaseContext.Organizations);
+        databaseContext.Users.RemoveRange(databaseContext.Users);
+        databaseContext.SaveChanges();
+    }
+
+    private static void NormalizeEncryptedStrings(RegisterFinishRequestModel requestModel)
+    {
+        var accountKeys = requestModel.UserAsymmetricKeys.AccountKeys;
+        if (accountKeys == null)
+        {
+            return;
+        }
+
+        accountKeys.UserKeyEncryptedAccountPrivateKey = DefaultEncryptedString;
+        if (accountKeys.PublicKeyEncryptionKeyPair != null)
+        {
+            accountKeys.PublicKeyEncryptionKeyPair.WrappedPrivateKey = DefaultEncryptedString;
+        }
+        if (accountKeys.SignatureKeyPair != null)
+        {
+            accountKeys.SignatureKeyPair.WrappedSigningKey = DefaultEncryptedString;
+            accountKeys.SignatureKeyPair.SignatureAlgorithm = "ed25519";
+        }
+    }
+}
--- a/test/Identity.IntegrationTest/RequestValidation/VaultAccess/ResourceOwnerPasswordValidatorTests.cs
+++ b/test/Identity.IntegrationTest/RequestValidation/VaultAccess/ResourceOwnerPasswordValidatorTests.cs
@@ -613,10 +613,10 @@ public class ResourceOwnerPasswordValidatorTests : IClassFixture<IdentityApplica
                KdfIterations = AuthConstants.PBKDF2_ITERATIONS.Default,
                UserAsymmetricKeys = new KeysRequestModel
                {
-                    PublicKey = "public_key",
-                    EncryptedPrivateKey = "private_key"
+                    PublicKey = Bit.Test.Common.Constants.TestEncryptionConstants.PublicKey,
+                    EncryptedPrivateKey = Bit.Test.Common.Constants.TestEncryptionConstants.AES256_CBC_HMAC_Encstring
                },
-                UserSymmetricKey = "sym_key",
+                UserSymmetricKey = Bit.Test.Common.Constants.TestEncryptionConstants.AES256_CBC_HMAC_Encstring,
            });
    }

--- a/test/Identity.Test/IdentityServer/BaseRequestValidatorTests.cs
+++ b/test/Identity.Test/IdentityServer/BaseRequestValidatorTests.cs
@@ -58,6 +58,7 @@ public class BaseRequestValidatorTests
    private readonly IAuthRequestRepository _authRequestRepository;
    private readonly IMailService _mailService;
    private readonly IUserAccountKeysQuery _userAccountKeysQuery;
+    private readonly IClientVersionValidator _clientVersionValidator;

    private readonly BaseRequestValidatorTestWrapper _sut;

@@ -82,6 +83,7 @@ public class BaseRequestValidatorTests
        _authRequestRepository = Substitute.For<IAuthRequestRepository>();
        _mailService = Substitute.For<IMailService>();
        _userAccountKeysQuery = Substitute.For<IUserAccountKeysQuery>();
+        _clientVersionValidator = Substitute.For<IClientVersionValidator>();

        _sut = new BaseRequestValidatorTestWrapper(
            _userManager,
@@ -102,7 +104,13 @@ public class BaseRequestValidatorTests
            _policyRequirementQuery,
            _authRequestRepository,
            _mailService,
-            _userAccountKeysQuery);
+            _userAccountKeysQuery,
+            _clientVersionValidator);
+
+        // Default client version validator behavior: allow to pass unless a test overrides.
+        _clientVersionValidator
+            .Validate(Arg.Any<User>(), Arg.Any<CustomValidatorRequestContext>())
+            .Returns(true);
    }

    /* Logic path
@@ -1266,6 +1274,38 @@ public class BaseRequestValidatorTests
            "TwoFactorRecoveryRequested flag should be set for audit/logging");
    }

+    [Theory]
+    [BitAutoData]
+    public async Task ValidateAsync_ClientVersionValidator_IsInvoked(
+        [AuthFixtures.ValidatedTokenRequest] ValidatedTokenRequest tokenRequest,
+        [AuthFixtures.CustomValidatorRequestContext] CustomValidatorRequestContext requestContext,
+        GrantValidationResult grantResult)
+    {
+        // Arrange
+        var context = CreateContext(tokenRequest, requestContext, grantResult);
+        _sut.isValid = true; // ensure initial context validation passes
+
+        // Force a grant type that will evaluate SSO after client version validation
+        context.ValidatedTokenRequest.GrantType = "password";
+
+        // Make client version validation succeed but ensure it's invoked
+        _clientVersionValidator
+            .Validate(requestContext.User, requestContext)
+            .Returns(true);
+
+        // Ensure SSO requirement triggers an early stop after version validation to avoid success path setup
+        _policyService.AnyPoliciesApplicableToUserAsync(
+                Arg.Any<Guid>(), PolicyType.RequireSso, OrganizationUserStatusType.Confirmed)
+            .Returns(Task.FromResult(true));
+
+        // Act
+        await _sut.ValidateAsync(context);
+
+        // Assert
+        _clientVersionValidator.Received(1)
+            .Validate(requestContext.User, requestContext);
+    }
+
    /// <summary>
    /// Tests that when SSO validation returns a custom response, (e.g., with organization identifier),
    /// that custom response is properly propagated to the result.
--- a/test/Identity.Test/IdentityServer/RequestValidators/ClientVersionValidatorTests.cs
+++ b/test/Identity.Test/IdentityServer/RequestValidators/ClientVersionValidatorTests.cs
@@ -0,0 +1,127 @@
+using Bit.Core.Context;
+using Bit.Core.Entities;
+using Bit.Identity.IdentityServer.RequestValidators;
+using Bit.Test.Common.Constants;
+using NSubstitute;
+using Xunit;
+
+namespace Bit.Identity.Test.IdentityServer.RequestValidators;
+
+public class ClientVersionValidatorTests
+{
+    private static ICurrentContext MakeContext(Version? version)
+    {
+        var ctx = Substitute.For<ICurrentContext>();
+        ctx.ClientVersion = version;
+        return ctx;
+    }
+
+    private static User MakeValidV2User()
+    {
+        return new User
+        {
+            PrivateKey = TestEncryptionConstants.V2PrivateKey,
+            SecurityVersion = 2
+        };
+    }
+
+    [Fact]
+    public void Allows_When_ClientMeetsMinimumVersion()
+    {
+        // Arrange
+        var sut = new ClientVersionValidator(MakeContext(new Version("2025.11.0")));
+        var ctx = new Bit.Identity.IdentityServer.CustomValidatorRequestContext();
+        var user = MakeValidV2User();
+
+        // Act
+        var ok = sut.Validate(user, ctx);
+
+        // Assert
+        Assert.True(ok);
+    }
+
+    [Fact]
+    public void Blocks_When_ClientTooOld()
+    {
+        // Arrange
+        var sut = new ClientVersionValidator(MakeContext(new Version("2025.10.0")));
+        var ctx = new Bit.Identity.IdentityServer.CustomValidatorRequestContext();
+        var user = MakeValidV2User();
+
+        // Act
+        var ok = sut.Validate(user, ctx);
+
+        // Assert
+        Assert.False(ok);
+        Assert.NotNull(ctx.ValidationErrorResult);
+        Assert.True(ctx.ValidationErrorResult.IsError);
+        Assert.Equal("invalid_client_version", ctx.ValidationErrorResult.Error);
+    }
+
+    [Fact]
+    public void Blocks_When_NullUser()
+    {
+        // Arrange
+        var sut = new ClientVersionValidator(MakeContext(new Version("2025.11.0")));
+        var ctx = new Bit.Identity.IdentityServer.CustomValidatorRequestContext();
+        User? user = null;
+
+        // Act
+        var ok = sut.Validate(user, ctx);
+
+        // Assert
+        Assert.False(ok);
+        Assert.NotNull(ctx.ValidationErrorResult);
+        Assert.True(ctx.ValidationErrorResult.IsError);
+        Assert.Equal("no_user", ctx.ValidationErrorResult.Error);
+    }
+
+    [Fact]
+    public void Allows_When_NoPrivateKey()
+    {
+        // Arrange
+        var sut = new ClientVersionValidator(MakeContext(new Version("2025.11.0")));
+        var ctx = new Bit.Identity.IdentityServer.CustomValidatorRequestContext();
+        var user = MakeValidV2User();
+        user.PrivateKey = null;
+
+        // Act
+        var ok = sut.Validate(user, ctx);
+
+        // Assert
+        Assert.True(ok);
+    }
+
+    [Fact]
+    public void Allows_When_NoSecurityVersion()
+    {
+        // Arrange
+        var sut = new ClientVersionValidator(MakeContext(new Version("2025.11.0")));
+        var ctx = new Bit.Identity.IdentityServer.CustomValidatorRequestContext();
+
+        var user = MakeValidV2User();
+        user.SecurityVersion = null;
+        // Act
+        var ok = sut.Validate(user, ctx);
+        // Assert
+        Assert.True(ok);
+    }
+
+    [Fact]
+    public void Blocks_When_ClientVersionHeaderMissing()
+    {
+        // Arrange
+        var sut = new ClientVersionValidator(MakeContext(null));
+        var ctx = new Bit.Identity.IdentityServer.CustomValidatorRequestContext();
+        var user = MakeValidV2User();
+
+        // Act
+        var ok = sut.Validate(user, ctx);
+
+        // Assert
+        Assert.False(ok);
+        Assert.NotNull(ctx.ValidationErrorResult);
+        Assert.True(ctx.ValidationErrorResult.IsError);
+        Assert.Equal("version_header_missing", ctx.ValidationErrorResult.Error);
+    }
+}
--- a/test/Identity.Test/Wrappers/BaseRequestValidatorTestWrapper.cs
+++ b/test/Identity.Test/Wrappers/BaseRequestValidatorTestWrapper.cs
@@ -67,7 +67,8 @@ IBaseRequestValidatorTestWrapper
        IPolicyRequirementQuery policyRequirementQuery,
        IAuthRequestRepository authRequestRepository,
        IMailService mailService,
-        IUserAccountKeysQuery userAccountKeysQuery) :
+        IUserAccountKeysQuery userAccountKeysQuery,
+        IClientVersionValidator clientVersionValidator) :
         base(
            userManager,
            userService,
@@ -87,7 +88,8 @@ IBaseRequestValidatorTestWrapper
            policyRequirementQuery,
            authRequestRepository,
            mailService,
-            userAccountKeysQuery)
+            userAccountKeysQuery,
+            clientVersionValidator)
    {
    }

--- a/test/IntegrationTestCommon/Factories/IdentityApplicationFactory.cs
+++ b/test/IntegrationTestCommon/Factories/IdentityApplicationFactory.cs
@@ -12,6 +12,8 @@ using Bit.Core.Enums;
 using Bit.Core.KeyManagement.Models.Api.Request;
 using Bit.Core.Services;
 using Bit.Identity;
+using Bit.Identity.IdentityServer;
+using Bit.Identity.IdentityServer.RequestValidators;
 using Bit.Test.Common.Helpers;
 using LinqToDB;
 using Microsoft.AspNetCore.Hosting;
@@ -27,6 +29,7 @@ public class IdentityApplicationFactory : WebApplicationFactoryBase<Startup>
    public const string DefaultUserEmail = "DefaultEmail@bitwarden.com";
    public const string DefaultUserPasswordHash = "default_password_hash";
    private const string DefaultEncryptedString = "2.3Uk+WNBIoU5xzmVFNcoWzz==|1MsPIYuRfdOHfu/0uY6H2Q==|/98sp4wb6pHP1VTZ9JcNCYgQjEUMFPlqJgCwRk1YXKg=";
+    public bool UseMockClientVersionValidator { get; set; } = true;

    /// <summary>
    /// A dictionary to store registration tokens for email verification. We cannot substitute the IMailService more than once, so
@@ -50,6 +53,16 @@ public class IdentityApplicationFactory : WebApplicationFactoryBase<Startup>
                });
        });

+        if (UseMockClientVersionValidator)
+        {
+            // Bypass client version gating to isolate tests from client version behavior
+            SubstituteService<IClientVersionValidator>(svc =>
+            {
+                svc.Validate(Arg.Any<User>(), Arg.Any<CustomValidatorRequestContext>())
+                    .Returns(true);
+            });
+        }
+
        base.ConfigureWebHost(builder);
    }

@@ -296,7 +309,7 @@ public class IdentityApplicationFactory : WebApplicationFactoryBase<Startup>
    {
        try
        {
-            if (ctx?.Response?.Body == null)
+            if (ctx?.Response.Body == null)
            {
                return "<no body>";
            }