Implement user ownership validation in Extend Service Extension

Last updated on May 27, 2025

Overview

By default, Extend Service Extension app template only includes a basic user verification mechanism. However, if user validation is required for a specific set of data, you can easily implement it by customizing your code.

Prerequisites

You have cloned the Extend Service Extension app template.

C#

git clone https://github.com/AccelByte/extend-service-extension-csharp

Go

git clone https://github.com/AccelByte/extend-service-extension-go

Java

git clone https://github.com/AccelByte/extend-service-extension-java

Implement user ownership validation

As an example, Extend Service Extension app template can be extended to incorporate ownership information for each guild data. During guild data creation, it will assign the currently authenticated user ID as the owner ID and store this information along with guild data. Subsequently, when a user attempts to access the guild data, it will verify the user ID and denies access if it does not match with stored owner ID.

note

This mechanism relies on the user ID stored in the sub field of the user access token payload. Since OAuth client access tokens do not contain a sub field, ownership information will not be stored when using client credentials.

C#

1. Add OwnerId property in Model/GuildProgressData.cs under Namespace property.

...

[JsonPropertyName("owner_id")]
public string OwnerId { get; set; } = "";

...

2. Add user id from access token payload to gRpc context's UserState in Classes/AuthorizationInterceptor.cs.

...

qPermission = (new Regex(@"\{(namespace|NAMESPACE)\}")).Replace(qPermission, (m) => _ABProvider.Sdk.Namespace);
int actNum = (int)qAction;
bool b = _ABProvider.Sdk.ValidateToken(authParts[1], qPermission, actNum);
if (!b)
    throw new RpcException(new Status(StatusCode.PermissionDenied, $"Permission {qPermission} [{qAction}] is required."));

// Add these code below after ValidateToken
var tokenPayload = _ABProvider.Sdk.ParseAccessToken(authParts[1], false);
if (tokenPayload == null)
    throw new RpcException(new Status(StatusCode.Unauthenticated, $"Invalid access token payload."));

string userId = "";
if (tokenPayload.Sub != null)
    userId = tokenPayload.Sub;

context.UserState.Add("loginUserId", userId);

...

3. Modify CreateOrUpdateGuildProgress implementation in Service/MyService.cs file.

public override Task<CreateOrUpdateGuildProgressResponse> CreateOrUpdateGuildProgress(CreateOrUpdateGuildProgressRequest request, ServerCallContext context)
{
    string actualGuildId = request.GuildProgress.GuildId.Trim();
    if (actualGuildId == "")
        actualGuildId = Guid.NewGuid().ToString().Replace("-", "");

    string gpKey = $"guildProgress_{actualGuildId}";

    string loginUserId = "";
    if (context.UserState.TryGetValue("loginUserId", out object? tempValue))
    {
        if (tempValue != null)
            loginUserId = tempValue.ToString()!;
    }
    else
        throw new Exception("No login user id data in context.");
    
    try
    {
        //check whether guild data specified by guild is exists or not
        var guildData = _ABProvider.Sdk.Cloudsave.AdminGameRecord.AdminGetGameRecordHandlerV1Op
            .Execute<GuildProgressData>(gpKey, request.Namespace);
        if (guildData == null)
            throw new Exception("NULL response from cloudsave service.");

        //if it exists, check owner user id.
        if (guildData.Value != null)
        {
            if (guildData.Value.OwnerId != loginUserId)
                throw new Exception("You don't have access to this data.");
        }

        //Guild data exists and belong to login user. Proceed to update
    }
    catch (HttpResponseException hrx)
    {
        if (hrx.StatusCode != HttpStatusCode.NotFound)
            throw;

        //Guild data does not exists. Proceed to create.
    }

    var gpValue = GuildProgressData.FromGuildProgressGrpcData(request.GuildProgress);
    gpValue.GuildId = actualGuildId;
    gpValue.OwnerId = loginUserId;

    var response = _ABProvider.Sdk.Cloudsave.AdminGameRecord.AdminPostGameRecordHandlerV1Op
        .Execute<GuildProgressData>(gpValue, gpKey, request.Namespace);
    if (response == null)
        throw new Exception("NULL response from cloudsave service.");

    GuildProgressData savedData = response.Value!;

    return Task.FromResult(new CreateOrUpdateGuildProgressResponse()
    {
        GuildProgress = savedData.ToGuildProgressGrpcData()
    });
}

4. Modify GetGuildProgress implementation in Service/MyService.cs file.

public override Task<GetGuildProgressResponse> GetGuildProgress(GetGuildProgressRequest request, ServerCallContext context)
{
    string gpKey = $"guildProgress_{request.GuildId.Trim()}";

    string loginUserId = "";
    if (context.UserState.TryGetValue("loginUserId", out object? tempValue))
    {
        if (tempValue != null)
            loginUserId = tempValue.ToString()!;
    }
    else
        throw new Exception("No login user id data in context.");

    var response = _ABProvider.Sdk.Cloudsave.AdminGameRecord.AdminGetGameRecordHandlerV1Op
        .Execute<GuildProgressData>(gpKey, request.Namespace);
    if (response == null)
        throw new Exception("NULL response from cloudsave service.");

    //if it exists, check owner user id.
    if (response.Value != null)
    {
        if (response.Value.OwnerId != loginUserId)
            throw new Exception("You don't have access to this data.");
    }

    GuildProgressData savedData = response.Value!;
    return Task.FromResult(new GetGuildProgressResponse()
    {
        GuildProgress = savedData.ToGuildProgressGrpcData()
    });
}

Go

1. Add a proto field user_id in the GuildProgress message inside your pkg/proto/service.proto file.

  message GuildProgress {
      string guild_id = 1;
      string namespace = 2;
      map<string, int32> objectives = 3;
+     string owner_id = 4;
  }

2. Run make proto to regenerate all protobuf files.

make proto

You should be able to see some changes to your pkg/pb/service.pb.go file.

  // pkg/pb/service.pb.go

  ...

  type GuildProgress struct {
      state         protoimpl.MessageState
      sizeCache     protoimpl.SizeCache
      unknownFields protoimpl.UnknownFields
  
      GuildId    string           `protobuf:"bytes,1,opt,name=guild_id,json=guildId,proto3" json:"guild_id,omitempty"`
      Namespace  string           `protobuf:"bytes,2,opt,name=namespace,proto3" json:"namespace,omitempty"`
      Objectives map[string]int32 `protobuf:"bytes,3,rep,name=objectives,proto3" json:"objectives,omitempty" protobuf_key:"bytes,1,opt,name=key,proto3" protobuf_val:"varint,2,opt,name=value,proto3"`
+     OwnerId    string           `protobuf:"bytes,4,opt,name=owner_id,json=ownerId,proto3" json:"owner_id,omitempty"`
  }

  ...

+ func (x *GuildProgress) GetOwnerId() string {
+     if x != nil {
+         return x.OwnerId
+     }
+     return ""
+ }

  ...

3. You'll also need to add a new field in the MyServiceServerImpl struct in the pkg/service/myService.go file.

  // pkg/service/myService.go

  type MyServiceServerImpl struct {
      pb.UnimplementedServiceServer
      tokenRepo    repository.TokenRepository
      configRepo   repository.ConfigRepository
      refreshRepo  repository.RefreshTokenRepository
      storage      storage.Storage
+     oauthService iam.OAuth20Service
  }
  
  func NewMyServiceServer(
      tokenRepo repository.TokenRepository,
      configRepo repository.ConfigRepository,
      refreshRepo repository.RefreshTokenRepository,
      storage storage.Storage,
+     oauthService iam.OAuth20Service,
  ) *MyServiceServerImpl {
      return &MyServiceServerImpl{
          tokenRepo:    tokenRepo,
          configRepo:   configRepo,
          refreshRepo:  refreshRepo,
          storage:      storage,
+         oauthService: oauthService,
      }
  }

This will give you access to a function that will help you extract a user's ID from a bearer token.

You'll also need to modify pkg/main.go to pass on that value.

  // pkg/main.go

  oauthService := iam.OAuth20Service{...}

  ...

  // Register Guild Service
- myServiceServer := service.NewMyServiceServer(tokenRepo, configRepo, refreshRepo, cloudSaveStorage)
+ myServiceServer := service.NewMyServiceServer(tokenRepo, configRepo, refreshRepo, cloudSaveStorage, oauthService)
  pb.RegisterServiceServer(s, myServiceServer)

3. Add in 2 utility functions for the MyServiceServerImpl struct in the pkg/service/myService.go file.

// pkg/service/myService.go

func (g MyServiceServerImpl) getTokenFromContext(ctx context.Context) (string, error) {
    if meta, found := metadata.FromIncomingContext(ctx); found {
        if authorizationValue, ok := meta["authorization"]; ok && len(authorizationValue) == 1 {
            if authorization := authorizationValue[0]; strings.HasPrefix(authorization, "Bearer ") {
                if token := strings.TrimPrefix(authorization, "Bearer "); token != "" {
                    return token, nil
                }
            }
        }
    }

    return "", fmt.Errorf("unable to get token from context")
}

func (g MyServiceServerImpl) getUserIdFromToken(token string) (string, error) {
    claims, err := g.oauthService.ParseAccessTokenToClaims(token, false)
    if err != nil {
        return "", err
    }

    if claims.Subject != "" {
        return claims.Subject, nil
    }

    return "", fmt.Errorf("unable to get user ID from token")
}

4. Modify the CreateOrUpdateGuildProgress function in the pkg/service/myService.go file.

  // pkg/service/myService.go

  func (g MyServiceServerImpl) CreateOrUpdateGuildProgress(
      ctx context.Context, req *pb.CreateOrUpdateGuildProgressRequest,
  ) (*pb.CreateOrUpdateGuildProgressResponse, error) {
+     if token, err := g.getTokenFromContext(ctx); err == nil {
+         if requesterUserId, err := g.getUserIdFromToken(token); err == nil {
+             req.GuildProgress.OwnerId = requesterUserId
+         }
+     }
+
      // Create or update guild progress in CloudSave
      // This assumes we're storing guild progress as a JSON object
      namespace := req.Namespace
      guildProgressKey := fmt.Sprintf("guildProgress_%s", req.GuildProgress.GuildId)
      guildProgressValue := req.GuildProgress
      guildProgress, err := g.storage.SaveGuildProgress(namespace, guildProgressKey, guildProgressValue)
      if err != nil {
          return nil, status.Errorf(codes.Internal, "Error updating guild progress: %v", err)
      }

      // Return the updated guild progress
      return &pb.CreateOrUpdateGuildProgressResponse{GuildProgress: guildProgress}, nil
  }

This will fill-in the newly added field owner_id with the requester's user ID.

5. Modify the GetGuildProgress function in the pkg/service/myService.go file.

  // pkg/service/myService.go

  func (g MyServiceServerImpl) GetGuildProgress(
      ctx context.Context, req *pb.GetGuildProgressRequest,
  ) (*pb.GetGuildProgressResponse, error) {
      // Get guild progress in CloudSave
      namespace := req.Namespace
      guildProgressKey := fmt.Sprintf("guildProgress_%s", req.GuildId)
  
      guildProgress, err := g.storage.GetGuildProgress(namespace, guildProgressKey)
      if err != nil {
          return nil, status.Errorf(codes.Internal, "Error getting guild progress: %v", err)
      }

+     ownerUserId := guildProgress.OwnerId
+     if ownerUserId != "" {
+         if token, err := g.getTokenFromContext(ctx); err == nil {
+             if requesterUserId, err := g.getUserIdFromToken(token); err == nil {
+                 if ownerUserId != requesterUserId {
+                     return nil, status.Errorf(
+                         codes.PermissionDenied,
+                         "guild progress is owned by %s and it cannot be viewed by requester (%s)",
+                         ownerUserId,
+                         requesterUserId,
+                     )
+                 }
+             }
+         }
+     }
+
      return &pb.GetGuildProgressResponse{
          GuildProgress: guildProgress,
      }, nil
  }

This will reject any requests for guild progresses not coming from the original creator of the guild progress.

Java

1. Modify src/main/java/net/accelbyte/extend/serviceextension/grpc/AuthServerInterceptor.java to add grpc context.

...
// add this import
import net.accelbyte.sdk.core.AccessTokenPayload;
...

@Slf4j
@GRpcGlobalInterceptor
@Order(20)
public class AuthServerInterceptor implements ServerInterceptor {

    ...

    private String namespace;

    // add context for logged in user id data
    public static final Context.Key<String> LOGIN_USER_ID = Context.key("login_user_id");

    ...

    @Override
    public <ReqT, RespT> ServerCall.Listener<ReqT> interceptCall(ServerCall<ReqT, RespT> call, Metadata headers,
        ServerCallHandler<ReqT, RespT> next) {

    ...

    if (!sdk.validateToken(authContext, permission)) {
        throw new Exception("Auth token validation failed");
    }

    // get user if from tooen payload and store it in context

    final AccessTokenPayload payload = sdk.parseAccessToken(authToken, false);
    String loginUserId = "";
    if (payload.getSub() != null)
        loginUserId = payload.getSub().trim();

    Context context = Context.current()
        .withValue(LOGIN_USER_ID, loginUserId);

    // return call with context
    return Contexts.interceptCall(context, call, headers, next);

    ...

    }
}

2. Create GuildData model class in src/main/java/net/accelbyte/extend/serviceextension/storage/GuildData.java.

package net.accelbyte.extend.serviceextension.storage;

import lombok.Getter;
import lombok.Setter;
import lombok.Builder;
import net.accelbyte.extend.serviceextension.GuildProgress;

@Getter
@Setter
@Builder
public class GuildData {

    private GuildProgress guildProgress;

    private String ownerId;
}

3. Modify Storage interface in src/main/java/net/accelbyte/extend/serviceextension/storage/Storage.java.

package net.accelbyte.extend.serviceextension.storage;

import net.accelbyte.sdk.core.HttpResponseException;
import net.accelbyte.extend.serviceextension.GuildProgress;

public interface Storage {

    GuildProgress getGuildProgress(String namespace, String key) throws Exception;

    GuildProgress saveGuildProgress(String namespace, String key, GuildProgress value, String ownerId) throws Exception;

    GuildData getGuildData(String namespace, String key) throws Exception, HttpResponseException;
}

4. Add new import in src/main/java/net/accelbyte/extend/serviceextension/storage/CloudsaveStorage.java

...
import net.accelbyte.sdk.core.HttpResponseException;
...

5. Modify CloudsaveStorage.CloudSaveModel class in src/main/java/net/accelbyte/extend/serviceextension/storage/CloudsaveStorage.java

    ...

    // add owner id property
    @JsonProperty
    private String owner_id;

    ...

    // add method to get owner id
    public String getOwnerId() {
        return owner_id;
    }

    ...

6. Modify CloudsaveStorage class in src/main/java/net/accelbyte/extend/serviceextension/storage/CloudsaveStorage.java

    //update saveGuildProgress method to include owner id
    @Override
    public GuildProgress saveGuildProgress(String namespace, String key, GuildProgress value, String ownerId) throws Exception {
        CloudSaveModel cloudModel = new CloudSaveModel(value, ownerId);
        AdminPostGameRecordHandlerV1 input = AdminPostGameRecordHandlerV1.builder()
                .namespace(namespace)
                .key(key)
                .body(cloudModel)
                .build();
        ModelsGameRecordAdminResponse response = csStorage.adminPostGameRecordHandlerV1(input);
        CloudSaveModel model = mapper.convertValue(response.getValue(), CloudSaveModel.class);
        return model.toGuildProgress();
    }

    //implement getGuildData method
    @Override
    public GuildData getGuildData(String namespace, String key) throws Exception, HttpResponseException {
        AdminGetGameRecordHandlerV1 input = AdminGetGameRecordHandlerV1.builder()
                .namespace(namespace)
                .key(key)
                .build();
        ModelsGameRecordAdminResponse response = csStorage.adminGetGameRecordHandlerV1(input);
        CloudSaveModel model = mapper.convertValue(response.getValue(), CloudSaveModel.class);

        return GuildData.builder()
            .guildProgress(model.toGuildProgress())
            .ownerId(model.getOwnerId())
            .build();
    }

8. Add new imports in src/main/java/net/accelbyte/extend/serviceextension/service/MyService.java

...
import net.accelbyte.sdk.core.HttpResponseException;
import net.accelbyte.extend.serviceextension.grpc.AuthServerInterceptor;
import net.accelbyte.extend.serviceextension.storage.GuildData;
...

9. Modify MyService class in src/main/java/net/accelbyte/extend/serviceextension/service/MyService.java

    ...

    //update createOrUpdateGuildProgress method
    @Override
    public void createOrUpdateGuildProgress(
        CreateOrUpdateGuildProgressRequest request, StreamObserver<CreateOrUpdateGuildProgressResponse> responseObserver
    ) {
        String guildProgressKey = String.format("guildProgress_%s", request.getGuildProgress().getGuildId());

        final String loginUserId = (String)AuthServerInterceptor.LOGIN_USER_ID.get();
            
        try {
            //check whether guild data specified by guild is exists or not
            GuildData guildData = storage.getGuildData(namespace, guildProgressKey);
            final String ownerId = guildData.getOwnerId();

            if (!ownerId.equals(loginUserId))
                throw new Exception("You don't have access to this data.");

            //Guild data exists and belong to login user. Proceed to update

        } catch (HttpResponseException x) {

            //If guild data does not exists. Proceed to create.            
            if (x.getHttpCode() != 404) {
                throw new IllegalArgumentException(x);
            }
        } catch (Exception e) {
            throw new IllegalArgumentException(e);
        }

        GuildProgress guildProgressValue = request.getGuildProgress();

        CreateOrUpdateGuildProgressResponse response;
        try {
            GuildProgress result = storage.saveGuildProgress(namespace, guildProgressKey, guildProgressValue, loginUserId);
            response = CreateOrUpdateGuildProgressResponse.newBuilder()
                    .setGuildProgress(result)
                    .build();
        } catch (Exception e) {
            throw new IllegalArgumentException(e);
        }

        responseObserver.onNext(response);
        responseObserver.onCompleted();
    }

    //update getGuildProgress method
    @Override
    public void getGuildProgress(
        GetGuildProgressRequest request, StreamObserver<GetGuildProgressResponse> responseObserver
    ) {
        String guildProgressKey = String.format("guildProgress_%s", request.getGuildId());

        final String loginUserId = (String)AuthServerInterceptor.LOGIN_USER_ID.get();

        GetGuildProgressResponse response;
        try {
            GuildData guildData = storage.getGuildData(namespace, guildProgressKey);
            final String ownerId = guildData.getOwnerId();

            if (!ownerId.equals(loginUserId))
                throw new Exception("You don't have access to this data.");

            response = GetGuildProgressResponse.newBuilder()
                    .setGuildProgress(guildData.getGuildProgress())
                    .build();
        } catch (Exception e) {
            throw new IllegalArgumentException(e);
        }

        responseObserver.onNext(response);
        responseObserver.onCompleted();
    }

    ...

info

You could find more information about gRPC request handling here.