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Load credentials from secrets for GCP KMS
Signed-off-by: Somtochi Onyekwere <[email protected]>
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,174 @@ | ||
| // This Source Code Form is subject to the terms of the Mozilla Public | ||
| // License, v. 2.0. If a copy of the MPL was not distributed with this | ||
| // file, You can obtain one at https://mozilla.org/MPL/2.0/. | ||
|
|
||
| package gcpkms | ||
|
|
||
| import ( | ||
| "context" | ||
| "encoding/base64" | ||
| "fmt" | ||
| "regexp" | ||
| "time" | ||
|
|
||
| kms "cloud.google.com/go/kms/apiv1" | ||
| "google.golang.org/api/option" | ||
| kmspb "google.golang.org/genproto/googleapis/cloud/kms/v1" | ||
| "google.golang.org/grpc" | ||
| ) | ||
|
|
||
| var ( | ||
| // gcpkmsTTL is the duration after which a MasterKey requiers rotation. | ||
| gcpkmsTTL = time.Hour * 24 * 30 * 6 | ||
| ) | ||
|
|
||
| // CredentialJSON is the service account keys used for aythentication towards a GCP KMS service. | ||
| type CredentialJSON []byte | ||
|
|
||
| // ApplyToMasterKey configures the credentialJSON on the provided key. | ||
| func (c CredentialJSON) ApplyToMasterKey(key *MasterKey) { | ||
| key.credentialJSON = []byte(c) | ||
| } | ||
|
|
||
| // MasterKey is a GCP KMS key used to encrypt and decrypt the SOPS | ||
| // data key | ||
| // Adapted from https://github.com/mozilla/sops/blob/v3.7.2/gcpkms/keysource.go | ||
| // to be able to have fine-grain control over the credentials used to authenticate | ||
| // to GCP KMS Service. | ||
| type MasterKey struct { | ||
| // ResourceID is the resource id used to refer to the gcp kms key. | ||
| // It can be retrieved using the `gcloud` command. | ||
| ResourceID string | ||
| // EncryptedKey is the string returned after encrypting with GCP KMS | ||
| EncryptedKey string | ||
| CreationDate time.Time | ||
|
|
||
| // credentialJSON are the service account keys used to authenticate | ||
| // to Google Cloud | ||
| credentialJSON []byte | ||
| // custom grpc server that will be used for cloudkms service | ||
| // for cloudkms service. This allows for mocking test. | ||
| grpcClient *grpc.ClientConn | ||
| } | ||
|
|
||
| // MasterKeyFromResourceID creates a new MasterKey with the ResourceID set, | ||
| func MasterKeyFromResourceID(resourceID string) *MasterKey { | ||
| return &MasterKey{ | ||
| ResourceID: resourceID, | ||
| CreationDate: time.Now().UTC(), | ||
| } | ||
| } | ||
|
|
||
| // Encrypt takes a sops data key, encrypts it with GCP KMS | ||
| // and stores the result in the EncryptedKey field | ||
| func (key *MasterKey) Encrypt(datakey []byte) error { | ||
| cloudkmsService, err := key.createKMSService() | ||
| if err != nil { | ||
| return err | ||
| } | ||
| defer cloudkmsService.Close() | ||
|
|
||
| req := &kmspb.EncryptRequest{ | ||
| Name: key.ResourceID, | ||
| Plaintext: datakey, | ||
| } | ||
| ctx := context.Background() | ||
| resp, err := cloudkmsService.Encrypt(ctx, req) | ||
| if err != nil { | ||
| return fmt.Errorf("failed to encrypt sops data key with GCP KMS: %w", err) | ||
| } | ||
| key.EncryptedKey = base64.StdEncoding.EncodeToString(resp.Ciphertext) | ||
| return nil | ||
| } | ||
|
|
||
| // SetEncryptedDataKey sets the encrypted data key for this master key. | ||
| func (key *MasterKey) SetEncryptedDataKey(enc []byte) { | ||
| key.EncryptedKey = string(enc) | ||
| } | ||
|
|
||
| // EncryptedDataKey returns the encrypted data key this master key holds. | ||
| func (key *MasterKey) EncryptedDataKey() []byte { | ||
| return []byte(key.EncryptedKey) | ||
| } | ||
|
|
||
| // EncryptIfNeeded encrypts the provided SOPS data key, if it has not been | ||
| // encrypted yet. | ||
| func (key *MasterKey) EncryptIfNeeded(dataKey []byte) error { | ||
| if key.EncryptedKey == "" { | ||
| return key.Encrypt(dataKey) | ||
| } | ||
| return nil | ||
| } | ||
|
|
||
| // Decrypt decrypts the EncryptedKey field with GCP KMS and returns | ||
| // the result. | ||
| func (key *MasterKey) Decrypt() ([]byte, error) { | ||
| cloudkmsService, err := key.createKMSService() | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| defer cloudkmsService.Close() | ||
|
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||
| decodedCipher, err := base64.StdEncoding.DecodeString(string(key.EncryptedDataKey())) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
| req := &kmspb.DecryptRequest{ | ||
| Name: key.ResourceID, | ||
| Ciphertext: decodedCipher, | ||
| } | ||
| ctx := context.Background() | ||
| resp, err := cloudkmsService.Decrypt(ctx, req) | ||
| if err != nil { | ||
| return nil, fmt.Errorf("failed to decrypt sops data key with GCP KMS Key: %w", err) | ||
| } | ||
|
|
||
| return resp.Plaintext, nil | ||
| } | ||
|
|
||
| // NeedsRotation returns whether the data key needs to be rotated or not. | ||
| func (key *MasterKey) NeedsRotation() bool { | ||
| return time.Since(key.CreationDate) > (gcpkmsTTL) | ||
| } | ||
|
|
||
| // ToString converts the key to a string representation. | ||
| func (key *MasterKey) ToString() string { | ||
| return key.ResourceID | ||
| } | ||
|
|
||
| // ToMap converts the MasterKey to a map for serialization purposes. | ||
| func (key MasterKey) ToMap() map[string]interface{} { | ||
| out := make(map[string]interface{}) | ||
| out["resource_id"] = key.ResourceID | ||
| out["created_at"] = key.CreationDate.UTC().Format(time.RFC3339) | ||
| out["enc"] = key.EncryptedKey | ||
| return out | ||
| } | ||
|
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||
| // createCloudKMSService create a GCP KMS client configured with the JSON credentials | ||
| // stored in the credentialJSON field. | ||
| func (key *MasterKey) createKMSService() (*kms.KeyManagementClient, error) { | ||
| re := regexp.MustCompile(`^projects/[^/]+/locations/[^/]+/keyRings/[^/]+/cryptoKeys/[^/]+$`) | ||
| matches := re.FindStringSubmatch(key.ResourceID) | ||
| if matches == nil { | ||
| return nil, fmt.Errorf("no valid resourceId found in %q", key.ResourceID) | ||
| } | ||
|
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| ctx := context.Background() | ||
| opts := []option.ClientOption{} | ||
|
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| if key.credentialJSON != nil { | ||
| opts = append(opts, option.WithCredentialsJSON(key.credentialJSON)) | ||
| } | ||
|
|
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| if key.grpcClient != nil { | ||
| opts = append(opts, option.WithGRPCConn(key.grpcClient)) | ||
| } | ||
|
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| client, err := kms.NewKeyManagementClient(ctx, opts...) | ||
| if err != nil { | ||
| return nil, err | ||
| } | ||
|
|
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| return client, nil | ||
| } |
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