// Copyright (c) 2015-2021 MinIO, Inc.
//
// This file is part of MinIO Object Storage stack
//
// This program is free software: you can redistribute it and/or modify
// it under the terms of the GNU Affero General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// This program is distributed in the hope that it will be useful
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU Affero General Public License for more details.
//
// You should have received a copy of the GNU Affero General Public License
// along with this program.  If not, see <http://www.gnu.org/licenses/>.

package cmd

import (
	"bytes"
	"context"
	"fmt"
	"path"
	"time"
	"unicode/utf8"

	"github.com/minio/minio/cmd/config"
	"github.com/minio/minio/cmd/logger"
	"github.com/minio/minio/pkg/auth"
	"github.com/minio/minio/pkg/kms"
	"github.com/minio/minio/pkg/madmin"
	etcd "go.etcd.io/etcd/clientv3"
)

func handleEncryptedConfigBackend(objAPI ObjectLayer) error {
	encrypted, err := checkBackendEncrypted(objAPI)
	if err != nil {
		return fmt.Errorf("Unable to encrypt config %w", err)
	}
	if err = migrateConfigPrefixToEncrypted(objAPI, encrypted); err != nil {
		return fmt.Errorf("Unable to migrate all config at .minio.sys/config/: %w", err)
	}
	return nil
}

const backendEncryptedFile = "backend-encrypted"

var backendEncryptedMigrationComplete = []byte("encrypted")

func checkBackendEtcdEncrypted(ctx context.Context, client *etcd.Client) (bool, error) {
	data, err := readKeyEtcd(ctx, client, backendEncryptedFile)
	if err != nil && err != errConfigNotFound {
		return false, err
	}
	return err == nil && bytes.Equal(data, backendEncryptedMigrationComplete), nil
}

func checkBackendEncrypted(objAPI ObjectLayer) (bool, error) {
	data, err := readConfig(GlobalContext, objAPI, backendEncryptedFile)
	if err != nil && err != errConfigNotFound {
		return false, err
	}
	return err == nil && bytes.Equal(data, backendEncryptedMigrationComplete), nil
}

// decryptData - decrypts input data with more that one credentials,
func decryptData(edata []byte, creds ...auth.Credentials) ([]byte, error) {
	var err error
	var data []byte
	for _, cred := range creds {
		data, err = madmin.DecryptData(cred.String(), bytes.NewReader(edata))
		if err != nil {
			if err == madmin.ErrMaliciousData {
				continue
			}
			return nil, err
		}
		break
	}
	return data, err
}

func migrateIAMConfigsEtcdToEncrypted(ctx context.Context, client *etcd.Client) error {
	encrypted, err := checkBackendEtcdEncrypted(ctx, client)
	if err != nil {
		return err
	}

	if encrypted {
		if GlobalKMS != nil {
			stat, err := GlobalKMS.Stat()
			if err != nil {
				return err
			}
			logger.Info("Attempting to re-encrypt config, IAM users and policies on MinIO with %q (%s)", stat.DefaultKey, stat.Name)
		} else {
			logger.Info("Attempting to migrate encrypted config, IAM users and policies on MinIO to a plaintext format. To encrypt all MinIO config data a KMS is needed")
		}
	}

	listCtx, cancel := context.WithTimeout(ctx, 1*time.Minute)
	defer cancel()

	r, err := client.Get(listCtx, minioConfigPrefix, etcd.WithPrefix(), etcd.WithKeysOnly())
	if err != nil {
		return err
	}

	for _, kv := range r.Kvs {
		data, err := readKeyEtcd(ctx, client, string(kv.Key))
		if err == errConfigNotFound { // Perhaps not present or someone deleted it.
			continue
		}
		if err != nil {
			return err
		}

		if !utf8.Valid(data) {
			data, err = decryptData(data, globalActiveCred)
			if err != nil {
				return fmt.Errorf("Decrypting config failed %w, possibly credentials are incorrect", err)
			}
		}

		if GlobalKMS != nil {
			data, err = config.EncryptBytes(GlobalKMS, data, kms.Context{
				minioMetaBucket: string(kv.Key),
			})
			if err != nil {
				return err
			}
		}

		if err = saveKeyEtcd(ctx, client, string(kv.Key), data); err != nil {
			return err
		}
	}

	if encrypted {
		if GlobalKMS != nil {
			logger.Info("Migration of encrypted config data completed. All config data is now encrypted with the KMS")
		} else {
			logger.Info("Migration of encrypted config data completed. All config data is now stored in plaintext")
		}
	}
	return deleteKeyEtcd(ctx, client, backendEncryptedFile)
}

func migrateConfigPrefixToEncrypted(objAPI ObjectLayer, encrypted bool) error {
	if !encrypted {
		return nil
	}
	if encrypted {
		if GlobalKMS != nil {
			stat, err := GlobalKMS.Stat()
			if err != nil {
				return err
			}
			logger.Info("Attempting to re-encrypt config, IAM users and policies on MinIO with %q (%s)", stat.DefaultKey, stat.Name)
		} else {
			logger.Info("Attempting to migrate encrypted config, IAM users and policies on MinIO to a plaintext format. To encrypt all MinIO config data a KMS is needed")
		}
	}

	var marker string
	for {
		res, err := objAPI.ListObjects(GlobalContext, minioMetaBucket, minioConfigPrefix, marker, "", maxObjectList)
		if err != nil {
			return err
		}
		for _, obj := range res.Objects {
			data, err := readConfig(GlobalContext, objAPI, obj.Name)
			if err != nil {
				return err
			}

			if !utf8.Valid(data) {
				data, err = decryptData(data, globalActiveCred)
				if err != nil {
					return fmt.Errorf("Decrypting config failed %w, possibly credentials are incorrect", err)
				}
			}
			if GlobalKMS != nil {
				data, err = config.EncryptBytes(GlobalKMS, data, kms.Context{
					obj.Bucket: path.Join(obj.Bucket, obj.Name),
				})
				if err != nil {
					return err
				}
			}
			if err = saveConfig(GlobalContext, objAPI, obj.Name, data); err != nil {
				return err
			}
		}

		if !res.IsTruncated {
			break
		}
		marker = res.NextMarker
	}
	if encrypted {
		if GlobalKMS != nil {
			logger.Info("Migration of encrypted config data completed. All config data is now encrypted with the KMS")
		} else {
			logger.Info("Migration of encrypted config data completed. All config data is now stored in plaintext")
		}
	}
	return deleteConfig(GlobalContext, globalObjectAPI, backendEncryptedFile)
}