feat: encrypt private keys saved on disk and in database (#682)

Co-authored-by: Kyle Mendell <kmendell@ofkm.us>

backend/internal/service/jwt_service.go

@@ -2,23 +2,20 @@ package service
 
 import (
 	"context"
-	"crypto/rand"
-	"crypto/rsa"
 	"encoding/json"
 	"errors"
 	"fmt"
 	"log"
-	"os"
-	"path/filepath"
 	"time"
 
 	"github.com/lestrrat-go/jwx/v3/jwa"
 	"github.com/lestrrat-go/jwx/v3/jwk"
 	"github.com/lestrrat-go/jwx/v3/jwt"
+	"gorm.io/gorm"
 
 	"github.com/pocket-id/pocket-id/backend/internal/common"
 	"github.com/pocket-id/pocket-id/backend/internal/model"
-	"github.com/pocket-id/pocket-id/backend/internal/utils"
+	jwkutils "github.com/pocket-id/pocket-id/backend/internal/utils/jwk"
 )
 
 const (
@@ -26,8 +23,9 @@ const (
 	// This is a JSON file containing a key encoded as JWK
 	PrivateKeyFile = "jwt_private_key.json"
 
-	// RsaKeySize is the size, in bits, of the RSA key to generate if none is found
-	RsaKeySize = 2048
+	// PrivateKeyFileEncrypted is the path in the data/keys folder where the encrypted key is stored
+	// This is a encrypted JSON file containing a key encoded as JWK
+	PrivateKeyFileEncrypted = "jwt_private_key.json.enc"
 
 	// KeyUsageSigning is the usage for the private keys, for the "use" property
 	KeyUsageSigning = "sig"
@@ -59,58 +57,74 @@ const (
 )
 
 type JwtService struct {
+	envConfig        *common.EnvConfigSchema
 	privateKey       jwk.Key
 	keyId            string
 	appConfigService *AppConfigService
 	jwksEncoded      []byte
 }
 
-func NewJwtService(appConfigService *AppConfigService) *JwtService {
+func NewJwtService(db *gorm.DB, appConfigService *AppConfigService) *JwtService {
 	service := &JwtService{}
 
 	// Ensure keys are generated or loaded
-	if err := service.init(appConfigService, common.EnvConfig.KeysPath); err != nil {
+	err := service.init(db, appConfigService, &common.EnvConfig)
+	if err != nil {
 		log.Fatalf("Failed to initialize jwt service: %v", err)
 	}
 
 	return service
 }
 
-func (s *JwtService) init(appConfigService *AppConfigService, keysPath string) error {
+func (s *JwtService) init(db *gorm.DB, appConfigService *AppConfigService, envConfig *common.EnvConfigSchema) (err error) {
 	s.appConfigService = appConfigService
+	s.envConfig = envConfig
 
 	// Ensure keys are generated or loaded
-	return s.loadOrGenerateKey(keysPath)
+	return s.loadOrGenerateKey(db)
 }
 
-// loadOrGenerateKey loads the private key from the given path or generates it if not existing.
-func (s *JwtService) loadOrGenerateKey(keysPath string) error {
-	var key jwk.Key
-
-	// First, check if we have a JWK file
-	// If we do, then we just load that
-	jwkPath := filepath.Join(keysPath, PrivateKeyFile)
-	ok, err := utils.FileExists(jwkPath)
+func (s *JwtService) loadOrGenerateKey(db *gorm.DB) error {
+	// Get the key provider
+	keyProvider, err := jwkutils.GetKeyProvider(db, s.envConfig, s.appConfigService.GetDbConfig().InstanceID.Value)
 	if err != nil {
-		return fmt.Errorf("failed to check if private key file (JWK) exists at path '%s': %w", jwkPath, err)
+		return fmt.Errorf("failed to get key provider: %w", err)
 	}
-	if ok {
-		key, err = s.loadKeyJWK(jwkPath)
-		if err != nil {
-			return fmt.Errorf("failed to load private key file (JWK) at path '%s': %w", jwkPath, err)
-		}
 
-		// Set the key, and we are done
+	// Try loading a key
+	key, err := keyProvider.LoadKey()
+	if err != nil {
+		return fmt.Errorf("failed to load key (provider type '%s'): %w", s.envConfig.KeysStorage, err)
+	}
+
+	// If we have a key, store it in the object and we're done
+	if key != nil {
 		err = s.SetKey(key)
 		if err != nil {
 			return fmt.Errorf("failed to set private key: %w", err)
 		}
-
 		return nil
 	}
 
 	// If we are here, we need to generate a new key
-	key, err = s.generateNewRSAKey()
+	err = s.generateKey()
+	if err != nil {
+		return fmt.Errorf("failed to generate key: %w", err)
+	}
+
+	// Save the newly-generated key
+	err = keyProvider.SaveKey(s.privateKey)
+	if err != nil {
+		return fmt.Errorf("failed to save private key (provider type '%s'): %w", s.envConfig.KeysStorage, err)
+	}
+
+	return nil
+}
+
+// generateKey generates a new key and stores it in the object
+func (s *JwtService) generateKey() error {
+	// Default is to generate RS256 (RSA-2048) keys
+	key, err := jwkutils.GenerateKey(jwa.RS256().String(), "")
 	if err != nil {
 		return fmt.Errorf("failed to generate new private key: %w", err)
 	}
@@ -121,12 +135,6 @@ func (s *JwtService) loadOrGenerateKey(keysPath string) error {
 		return fmt.Errorf("failed to set private key: %w", err)
 	}
 
-	// Save the key as JWK
-	err = SaveKeyJWK(s.privateKey, jwkPath)
-	if err != nil {
-		return fmt.Errorf("failed to save private key file at path '%s': %w", jwkPath, err)
-	}
-
 	return nil
 }
 
@@ -192,13 +200,13 @@ func (s *JwtService) GenerateAccessToken(user model.User) (string, error) {
 		Subject(user.ID).
 		Expiration(now.Add(s.appConfigService.GetDbConfig().SessionDuration.AsDurationMinutes())).
 		IssuedAt(now).
-		Issuer(common.EnvConfig.AppURL).
+		Issuer(s.envConfig.AppURL).
 		Build()
 	if err != nil {
 		return "", fmt.Errorf("failed to build token: %w", err)
 	}
 
-	err = SetAudienceString(token, common.EnvConfig.AppURL)
+	err = SetAudienceString(token, s.envConfig.AppURL)
 	if err != nil {
 		return "", fmt.Errorf("failed to set 'aud' claim in token: %w", err)
 	}
@@ -229,8 +237,8 @@ func (s *JwtService) VerifyAccessToken(tokenString string) (jwt.Token, error) {
 		jwt.WithValidate(true),
 		jwt.WithKey(alg, s.privateKey),
 		jwt.WithAcceptableSkew(clockSkew),
-		jwt.WithAudience(common.EnvConfig.AppURL),
-		jwt.WithIssuer(common.EnvConfig.AppURL),
+		jwt.WithAudience(s.envConfig.AppURL),
+		jwt.WithIssuer(s.envConfig.AppURL),
 		jwt.WithValidator(TokenTypeValidator(AccessTokenJWTType)),
 	)
 	if err != nil {
@@ -246,7 +254,7 @@ func (s *JwtService) BuildIDToken(userClaims map[string]any, clientID string, no
 	token, err := jwt.NewBuilder().
 		Expiration(now.Add(1 * time.Hour)).
 		IssuedAt(now).
-		Issuer(common.EnvConfig.AppURL).
+		Issuer(s.envConfig.AppURL).
 		Build()
 	if err != nil {
 		return nil, fmt.Errorf("failed to build token: %w", err)
@@ -305,7 +313,7 @@ func (s *JwtService) VerifyIdToken(tokenString string, acceptExpiredTokens bool)
 		jwt.WithValidate(true),
 		jwt.WithKey(alg, s.privateKey),
 		jwt.WithAcceptableSkew(clockSkew),
-		jwt.WithIssuer(common.EnvConfig.AppURL),
+		jwt.WithIssuer(s.envConfig.AppURL),
 		jwt.WithValidator(TokenTypeValidator(IDTokenJWTType)),
 	)
 
@@ -335,7 +343,7 @@ func (s *JwtService) BuildOAuthAccessToken(user model.User, clientID string) (jw
 		Subject(user.ID).
 		Expiration(now.Add(1 * time.Hour)).
 		IssuedAt(now).
-		Issuer(common.EnvConfig.AppURL).
+		Issuer(s.envConfig.AppURL).
 		Build()
 	if err != nil {
 		return nil, fmt.Errorf("failed to build token: %w", err)
@@ -377,7 +385,7 @@ func (s *JwtService) VerifyOAuthAccessToken(tokenString string) (jwt.Token, erro
 		jwt.WithValidate(true),
 		jwt.WithKey(alg, s.privateKey),
 		jwt.WithAcceptableSkew(clockSkew),
-		jwt.WithIssuer(common.EnvConfig.AppURL),
+		jwt.WithIssuer(s.envConfig.AppURL),
 		jwt.WithValidator(TokenTypeValidator(OAuthAccessTokenJWTType)),
 	)
 	if err != nil {
@@ -393,7 +401,7 @@ func (s *JwtService) GenerateOAuthRefreshToken(userID string, clientID string, r
 		Subject(userID).
 		Expiration(now.Add(RefreshTokenDuration)).
 		IssuedAt(now).
-		Issuer(common.EnvConfig.AppURL).
+		Issuer(s.envConfig.AppURL).
 		Build()
 	if err != nil {
 		return "", fmt.Errorf("failed to build token: %w", err)
@@ -430,7 +438,7 @@ func (s *JwtService) VerifyOAuthRefreshToken(tokenString string) (userID, client
 		jwt.WithValidate(true),
 		jwt.WithKey(alg, s.privateKey),
 		jwt.WithAcceptableSkew(clockSkew),
-		jwt.WithIssuer(common.EnvConfig.AppURL),
+		jwt.WithIssuer(s.envConfig.AppURL),
 		jwt.WithValidator(TokenTypeValidator(OAuthRefreshTokenJWTType)),
 	)
 	if err != nil {
@@ -488,7 +496,7 @@ func (s *JwtService) GetPublicJWK() (jwk.Key, error) {
 		return nil, fmt.Errorf("failed to get public key: %w", err)
 	}
 
-	utils.EnsureAlgInKey(pubKey)
+	jwkutils.EnsureAlgInKey(pubKey, "", "")
 
 	return pubKey, nil
 }
@@ -517,56 +525,6 @@ func (s *JwtService) GetKeyAlg() (jwa.KeyAlgorithm, error) {
 	return alg, nil
 }
 
-func (s *JwtService) loadKeyJWK(path string) (jwk.Key, error) {
-	data, err := os.ReadFile(path)
-	if err != nil {
-		return nil, fmt.Errorf("failed to read key data: %w", err)
-	}
-
-	key, err := jwk.ParseKey(data)
-	if err != nil {
-		return nil, fmt.Errorf("failed to parse key: %w", err)
-	}
-
-	return key, nil
-}
-
-func (s *JwtService) generateNewRSAKey() (jwk.Key, error) {
-	// We generate RSA keys only
-	rawKey, err := rsa.GenerateKey(rand.Reader, RsaKeySize)
-	if err != nil {
-		return nil, fmt.Errorf("failed to generate RSA private key: %w", err)
-	}
-
-	// Import the raw key
-	return utils.ImportRawKey(rawKey)
-}
-
-// SaveKeyJWK saves a JWK to a file
-func SaveKeyJWK(key jwk.Key, path string) error {
-	dir := filepath.Dir(path)
-	err := os.MkdirAll(dir, 0700)
-	if err != nil {
-		return fmt.Errorf("failed to create directory '%s' for key file: %w", dir, err)
-	}
-
-	keyFile, err := os.OpenFile(path, os.O_RDWR|os.O_CREATE|os.O_TRUNC, 0600)
-	if err != nil {
-		return fmt.Errorf("failed to create key file: %w", err)
-	}
-	defer keyFile.Close()
-
-	// Write the JSON file to disk
-	enc := json.NewEncoder(keyFile)
-	enc.SetEscapeHTML(false)
-	err = enc.Encode(key)
-	if err != nil {
-		return fmt.Errorf("failed to write key file: %w", err)
-	}
-
-	return nil
-}
-
 // GetIsAdmin returns the value of the "isAdmin" claim in the token
 func GetIsAdmin(token jwt.Token) (bool, error) {
 	if !token.Has(IsAdminClaim) {