Ensure key is not nil

If the public key is nil, the key validation function from
ParseWithClaims should NOT return the issuer public Key.

The code snippet checks if the EcdsaPublic field of the issuer
(an instance of TokenIssuer) is nil. The EcdsaPublic field
holds the public key used to verify the token's signature.
If this field is nil, it means that the public key is not available,
and the method cannot proceed with the token verification.

If the EcdsaPublic field is indeed nil, the method now
returns nil and an error. This ensures that the caller
of the VerifyToken method is informed about the missing public key,
which is crucial for debugging and handling the error appropriately.

This check is essential to prevent the method from attempting to
verify the token without a valid public key,
which would result in a runtime error or incorrect verification results.

cmd/api/main.go

@@ -37,7 +37,15 @@ func main() {
 		utils.Log.Fatal().Msgf("Unable to read ECDSA public key: %v", err)
 	}
 
-	tokenIssuer, err := services.NewTokenIssuer(ecdsaPem, ecdsaPubPem, utils.Config.TokenLifeTime, utils.Config.ExtraTokenLifeTime, utils.Config.Locator, utils.Config.PublicApiServerURL, utils.Config.Tenant)
+	tokenIssuer, err := services.NewTokenIssuer(
+		ecdsaPem,
+		ecdsaPubPem,
+		config.TokenLifeTime,
+		config.ExtraTokenLifeTime,
+		config.Locator,
+		config.PublicApiServerURL,
+		config.Tenant,
+	)
 	if err != nil {
 		utils.Log.Fatal().Msgf("Unable to create token issuer: %v", err)
 	}

internal/services/token-provider.go

@@ -292,7 +292,10 @@ func generateKubeConfig(serverURL string, CA string, user types.User, token *str
 func (issuer *TokenIssuer) VerifyToken(usertoken string) (*types.AuthJWTClaims, error) {
 
 	// this verifies the token and its signature
-	token, err := jwt.ParseWithClaims(usertoken, &types.AuthJWTClaims{}, func(token *jwt.Token) (interface{}, error) {
+	token, err := jwt.ParseWithClaims(usertoken, types.AuthJWTClaims{}, func(token *jwt.Token) (interface{}, error) {
+		if issuer.EcdsaPublic == nil {
+			return nil, fmt.Errorf("the public key is nil")
+		}
 		return issuer.EcdsaPublic, nil
 	})
 	if err != nil {