Initial KeyStore implementation

internal/crypto/algorithm.go → internal/crypto/algorithms/aes256cfb.go

@@ -12,54 +12,28 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
-package crypto
+package algorithms
 
 import (
 	"crypto/aes"
 	"crypto/cipher"
 	"crypto/rand"
-	"errors"
 	"io"
 
 	"golang.org/x/crypto/argon2"
 	"google.golang.org/grpc/codes"
 	"google.golang.org/grpc/status"
 )
 
-// EncryptionAlgorithm represents a crypto algorithm used by the Engine
-type EncryptionAlgorithm interface {
-	Encrypt(data []byte, salt []byte) ([]byte, error)
-	Decrypt(data []byte, salt []byte) ([]byte, error)
-}
-
-// EncryptionAlgorithmType is an enum of supported encryption algorithms
-type EncryptionAlgorithmType string
-
-const (
-	// Aes256Cfb is the AES-256-CFB algorithm
-	Aes256Cfb EncryptionAlgorithmType = "aes-256-cfb"
-)
-
-const maxSize = 32 * 1024 * 1024
-
-// ErrUnknownAlgorithm is used when an incorrect algorithm name is used.
-var ErrUnknownAlgorithm = errors.New("unexpected encryption algorithm")
-
-func newAlgorithm(key []byte) EncryptionAlgorithm {
-	// TODO: Make the type of algorithm selectable
-	return &aesCFBSAlgorithm{encryptionKey: key}
-}
-
-type aesCFBSAlgorithm struct {
-	encryptionKey []byte
-}
+// AES256CFBAlgorithm implements the AES-256-CFB algorithm
+type AES256CFBAlgorithm struct{}
 
 // Encrypt encrypts a row of data.
-func (a *aesCFBSAlgorithm) Encrypt(data []byte, salt []byte) ([]byte, error) {
+func (a *AES256CFBAlgorithm) Encrypt(data []byte, key []byte, salt []byte) ([]byte, error) {
 	if len(data) > maxSize {
 		return nil, status.Errorf(codes.InvalidArgument, "data is too large (>32MB)")
 	}
-	block, err := aes.NewCipher(a.deriveKey(salt))
+	block, err := aes.NewCipher(a.deriveKey(key, salt))
 	if err != nil {
 		return nil, status.Errorf(codes.Unknown, "failed to create cipher: %s", err)
 	}
@@ -78,8 +52,8 @@ func (a *aesCFBSAlgorithm) Encrypt(data []byte, salt []byte) ([]byte, error) {
 }
 
 // Decrypt decrypts a row of data.
-func (a *aesCFBSAlgorithm) Decrypt(ciphertext []byte, salt []byte) ([]byte, error) {
-	block, err := aes.NewCipher(a.deriveKey(salt))
+func (a *AES256CFBAlgorithm) Decrypt(ciphertext []byte, key []byte, salt []byte) ([]byte, error) {
+	block, err := aes.NewCipher(a.deriveKey(key, salt))
 	if err != nil {
 		return nil, status.Errorf(codes.Unknown, "failed to create cipher: %s", err)
 	}
@@ -95,6 +69,6 @@ func (a *aesCFBSAlgorithm) Decrypt(ciphertext []byte, salt []byte) ([]byte, erro
 }
 
 // Function to derive a key from a passphrase using Argon2
-func (a *aesCFBSAlgorithm) deriveKey(salt []byte) []byte {
-	return argon2.IDKey(a.encryptionKey, salt, 1, 64*1024, 4, 32)
+func (_ *AES256CFBAlgorithm) deriveKey(key []byte, salt []byte) []byte {
+	return argon2.IDKey(key, salt, 1, 64*1024, 4, 32)
 }

internal/crypto/algorithms/algorithm.go

@@ -0,0 +1,61 @@
+// Copyright 2024 Stacklok, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package algorithms contains implementations of various crypto algorithms
+// for the crypto engine.
+package algorithms
+
+import (
+	"errors"
+	"fmt"
+)
+
+// EncryptionAlgorithm represents a crypto algorithm used by the Engine
+type EncryptionAlgorithm interface {
+	Encrypt(data []byte, key []byte, salt []byte) ([]byte, error)
+	Decrypt(data []byte, key []byte, salt []byte) ([]byte, error)
+}
+
+// Type is an enum of supported encryption algorithms
+type Type string
+
+const (
+	// Aes256Cfb is the AES-256-CFB algorithm
+	Aes256Cfb Type = "aes-256-cfb"
+)
+
+const maxSize = 32 * 1024 * 1024
+
+// ErrUnknownAlgorithm is used when an incorrect algorithm name is used.
+var (
+	ErrUnknownAlgorithm = errors.New("unexpected encryption algorithm")
+)
+
+// TypeFromString attempts to map a string to a `Type` value.
+func TypeFromString(name string) (Type, error) {
+	// TODO: use switch when we support more than once type.
+	if name == string(Aes256Cfb) {
+		return Aes256Cfb, nil
+	}
+	return "", fmt.Errorf("%w: %s", ErrUnknownAlgorithm, name)
+}
+
+// NewFromType instantiates an encryption algorithm by name
+func NewFromType(algoType Type) (EncryptionAlgorithm, error) {
+	// TODO: use switch when we support more than once type.
+	if algoType == Aes256Cfb {
+		return &AES256CFBAlgorithm{}, nil
+	}
+	return nil, fmt.Errorf("%w: %s", ErrUnknownAlgorithm, algoType)
+}

internal/crypto/engine.go

@@ -21,10 +21,13 @@ import (
 	"encoding/json"
 	"errors"
 	"fmt"
+	"path/filepath"
 
 	"golang.org/x/oauth2"
 
 	serverconfig "github.com/stacklok/minder/internal/config/server"
+	"github.com/stacklok/minder/internal/crypto/algorithms"
+	"github.com/stacklok/minder/internal/crypto/keystores"
 )
 
 //go:generate go run go.uber.org/mock/mockgen -package mock_$GOPACKAGE -destination=./mock/$GOFILE -source=./$GOFILE
@@ -50,27 +53,44 @@ var (
 	ErrEncrypt = errors.New("unable to encrypt")
 )
 
+type algorithmsByName map[algorithms.Type]algorithms.EncryptionAlgorithm
+
 type engine struct {
-	algorithm EncryptionAlgorithm
+	keystore            keystores.KeyStore
+	supportedAlgorithms algorithmsByName
+	defaultKeyID        string
+	defaultAlgorithm    algorithms.Type
 }
 
-// NewEngineFromAuthConfig creates a new crypto engine from an auth config
-func NewEngineFromAuthConfig(authConfig *serverconfig.AuthConfig) (Engine, error) {
-	if authConfig == nil {
+// NewEngineFromAuthConfig creates a new crypto engine from the service config
+// TODO: modify to support multiple keys/algorithms
+func NewEngineFromAuthConfig(config *serverconfig.AuthConfig) (Engine, error) {
+	if config == nil {
 		return nil, errors.New("auth config is nil")
 	}
 
-	keyBytes, err := authConfig.GetTokenKey()
+	keystore, err := keystores.NewKeyStoreFromConfig(config)
 	if err != nil {
 		return nil, fmt.Errorf("failed to read token key file: %s", err)
 	}
 
-	return NewEngine(keyBytes), nil
-}
+	aes, err := algorithms.NewFromType(algorithms.Aes256Cfb)
+	if err != nil {
+		return nil, err
+	}
+	supportedAlgorithms := map[algorithms.Type]algorithms.EncryptionAlgorithm{
+		algorithms.Aes256Cfb: aes,
+	}
 
-// NewEngine creates the engine based on the specified algorithm and key.
-func NewEngine(key []byte) Engine {
-	return &engine{algorithm: newAlgorithm(key)}
+	return &engine{
+		keystore:            keystore,
+		supportedAlgorithms: supportedAlgorithms,
+		defaultAlgorithm:    algorithms.Aes256Cfb,
+		// Use the key filename as the key ID.
+		// This will be cleaned up in a future PR
+		// Right now, by the time we get here, this should return a valid result
+		defaultKeyID: filepath.Base(config.TokenKey),
+	}, nil
 }
 
 func (e *engine) EncryptOAuthToken(token *oauth2.Token) (EncryptedData, error) {
@@ -83,7 +103,7 @@ func (e *engine) EncryptOAuthToken(token *oauth2.Token) (EncryptedData, error) {
 	// Encrypt the JSON.
 	encrypted, err := e.encrypt(jsonData)
 	if err != nil {
-		return EncryptedData{}, fmt.Errorf("unable to encrypt token: %w", err)
+		return EncryptedData{}, err
 	}
 	return encrypted, nil
 }
@@ -114,38 +134,60 @@ func (e *engine) EncryptString(data string) (EncryptedData, error) {
 func (e *engine) DecryptString(encryptedString EncryptedData) (string, error) {
 	decrypted, err := e.decrypt(encryptedString)
 	if err != nil {
-		return "", fmt.Errorf("%w: %w", ErrDecrypt, err)
+		return "", err
 	}
 	return string(decrypted), nil
 }
 
 func (e *engine) encrypt(data []byte) (EncryptedData, error) {
-	encrypted, err := e.algorithm.Encrypt(data, legacySalt)
+	// Neither of these lookups should ever fail.
+	algorithm, ok := e.supportedAlgorithms[e.defaultAlgorithm]
+	if !ok {
+		return EncryptedData{}, fmt.Errorf("unable to find preferred algorithm: %s", e.defaultAlgorithm)
+	}
+
+	key, err := e.keystore.GetKey(e.defaultKeyID)
 	if err != nil {
-		return EncryptedData{}, err
+		return EncryptedData{}, fmt.Errorf("unable to find preferred key with ID: %s", e.defaultKeyID)
+	}
+
+	encrypted, err := algorithm.Encrypt(data, key, legacySalt)
+	if err != nil {
+		return EncryptedData{}, errors.Join(ErrEncrypt, err)
 	}
 
 	encoded := base64.StdEncoding.EncodeToString(encrypted)
-	// TODO:
-	// 1. when we support more than one algorithm, remove hard-coding.
-	// 2. Allow salt to be randomly generated per secret.
-	// 3. Set key version.
-	return NewBackwardsCompatibleEncryptedData(encoded), nil
+	// TODO: Allow salt to be randomly generated per secret.
+	return EncryptedData{
+		Algorithm:   e.defaultAlgorithm,
+		EncodedData: encoded,
+		Salt:        legacySalt,
+		KeyVersion:  e.defaultKeyID,
+	}, nil
 }
 
 func (e *engine) decrypt(data EncryptedData) ([]byte, error) {
-	// TODO: Select algorithm based on Algorithm field when we support
-	// more than one algorithm.
-	if data.Algorithm != Aes256Cfb {
-		return nil, fmt.Errorf("%w: %s", ErrUnknownAlgorithm, data.Algorithm)
+	algorithm, ok := e.supportedAlgorithms[data.Algorithm]
+	if !ok {
+		return nil, fmt.Errorf("%w: %s", algorithms.ErrUnknownAlgorithm, e.defaultAlgorithm)
+	}
+
+	key, err := e.keystore.GetKey(e.defaultKeyID)
+	if err != nil {
+		// error from keystore is good enough - we do not need more context
+		return nil, err
 	}
 
 	// base64 decode the string
 	encrypted, err := base64.StdEncoding.DecodeString(data.EncodedData)
 	if err != nil {
-		return nil, err
+		return nil, fmt.Errorf("error decoding secret: %w", err)
 	}
 
 	// decrypt the data
-	return e.algorithm.Decrypt(encrypted, data.Salt)
+	result, err := algorithm.Decrypt(encrypted, key, data.Salt)
+	if err != nil {
+		return nil, errors.Join(ErrDecrypt, err)
+	}
+	return result, nil
 }

internal/crypto/keystores/keystore.go

@@ -0,0 +1,70 @@
+// Copyright 2024 Stacklok, Inc.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package keystores contains logic for loading encryption keys from a keystores
+package keystores
+
+import (
+	"errors"
+	"fmt"
+	"path/filepath"
+
+	serverconfig "github.com/stacklok/minder/internal/config/server"
+)
+
+//go:generate go run go.uber.org/mock/mockgen -package mock_$GOPACKAGE -destination=./mock/$GOFILE -source=./$GOFILE
+
+// KeyStore represents a struct which stores or can fetch encryption keys.
+type KeyStore interface {
+	// GetKey retrieves the key for the specified algorithm by key ID.
+	GetKey(id string) ([]byte, error)
+}
+
+// ErrUnknownKeyID is returned when the Key ID cannot be found by the keystore.
+var ErrUnknownKeyID = errors.New("unknown key id")
+
+// This structure is used by the keystore implementation to manage keys.
+type keysByID map[string][]byte
+
+// NewKeyStoreFromConfig creates an instance of a KeyStore based on the
+// AuthConfig in Minder.
+// Since our only implementation is based on reading from the local disk, do
+// all key loading during construction of the struct.
+// TODO: allow support for multiple keys/algos
+func NewKeyStoreFromConfig(config *serverconfig.AuthConfig) (KeyStore, error) {
+	key, err := config.GetTokenKey()
+	if err != nil {
+		return nil, fmt.Errorf("unable to read encryption key from %s: %w", config.TokenKey, err)
+	}
+	// Use the key filename as the key ID.
+	name := filepath.Base(config.TokenKey)
+	keys := map[string][]byte{
+		name: key,
+	}
+	return &localFileKeyStore{
+		keys: keys,
+	}, nil
+}
+
+type localFileKeyStore struct {
+	keys keysByID
+}
+
+func (l *localFileKeyStore) GetKey(id string) ([]byte, error) {
+	key, ok := l.keys[id]
+	if !ok {
+		return nil, fmt.Errorf("%w: %s", ErrUnknownKeyID, id)
+	}
+	return key, nil
+}

internal/crypto/models.go

@@ -17,13 +17,15 @@ package crypto
 import (
 	"encoding/json"
 	"fmt"
+
+	"github.com/stacklok/minder/internal/crypto/algorithms"
 )
 
 // EncryptedData represents the structure we use to store encrypted data in the
 // database.
 type EncryptedData struct {
 	// The type of encryption used.
-	Algorithm EncryptionAlgorithmType
+	Algorithm algorithms.Type
 	// The encrypted data represented as a base64 encoded string.
 	EncodedData string
 	// The salt used in the encryption.
@@ -44,7 +46,7 @@ func (e *EncryptedData) Serialize() (json.RawMessage, error) {
 // and should be removed once we migrate to the new encryption model.
 func NewBackwardsCompatibleEncryptedData(encryptedData string) EncryptedData {
 	return EncryptedData{
-		Algorithm:   Aes256Cfb,
+		Algorithm:   algorithms.Aes256Cfb,
 		EncodedData: encryptedData,
 		Salt:        legacySalt,
 		KeyVersion:  "",