feat: Disallow unknown config fields (#4531)

Signed-off-by: maksim.nabokikh <max.nabokih@gmail.com>

cmd/dex/config.go

@@ -1,6 +1,7 @@
 package main
 
 import (
+	"bytes"
 	"encoding/base64"
 	"encoding/json"
 	"fmt"
@@ -23,6 +24,15 @@ import (
 	"github.com/dexidp/dex/storage/sql"
 )
 
+func configUnmarshaller(b []byte, v interface{}) error {
+	if featureflags.ConfigDisallowUnknownFields.Enabled() {
+		return json.Unmarshal(b, v)
+	}
+	dec := json.NewDecoder(bytes.NewReader(b))
+	dec.DisallowUnknownFields()
+	return dec.Decode(v)
+}
+
 // Config is the config format for the main application.
 type Config struct {
 	Issuer    string    `json:"issuer"`
@@ -109,7 +119,7 @@ func (p *password) UnmarshalJSON(b []byte) error {
 		HashFromEnv       string   `json:"hashFromEnv"`
 		Groups            []string `json:"groups"`
 	}
-	if err := json.Unmarshal(b, &data); err != nil {
+	if err := configUnmarshaller(b, &data); err != nil {
 		return err
 	}
 	*p = password(storage.Password{
@@ -333,7 +343,7 @@ func (s *Storage) UnmarshalJSON(b []byte) error {
 		Type   string          `json:"type"`
 		Config json.RawMessage `json:"config"`
 	}
-	if err := json.Unmarshal(b, &store); err != nil {
+	if err := configUnmarshaller(b, &store); err != nil {
 		return fmt.Errorf("parse storage: %v", err)
 	}
 	f, ok := storages[store.Type]
@@ -346,7 +356,7 @@ func (s *Storage) UnmarshalJSON(b []byte) error {
 		data := []byte(store.Config)
 		if featureflags.ExpandEnv.Enabled() {
 			var rawMap map[string]interface{}
-			if err := json.Unmarshal(store.Config, &rawMap); err != nil {
+			if err := configUnmarshaller(store.Config, &rawMap); err != nil {
 				return fmt.Errorf("unmarshal config for env expansion: %v", err)
 			}
 
@@ -363,7 +373,7 @@ func (s *Storage) UnmarshalJSON(b []byte) error {
 			data = expandedData
 		}
 
-		if err := json.Unmarshal(data, storageConfig); err != nil {
+		if err := configUnmarshaller(data, storageConfig); err != nil {
 			return fmt.Errorf("parse storage config: %v", err)
 		}
 	}
@@ -462,7 +472,7 @@ func (c *Connector) UnmarshalJSON(b []byte) error {
 
 		Config json.RawMessage `json:"config"`
 	}
-	if err := json.Unmarshal(b, &conn); err != nil {
+	if err := configUnmarshaller(b, &conn); err != nil {
 		return fmt.Errorf("parse connector: %v", err)
 	}
 	f, ok := server.ConnectorsConfig[conn.Type]
@@ -475,7 +485,7 @@ func (c *Connector) UnmarshalJSON(b []byte) error {
 		data := []byte(conn.Config)
 		if featureflags.ExpandEnv.Enabled() {
 			var rawMap map[string]interface{}
-			if err := json.Unmarshal(conn.Config, &rawMap); err != nil {
+			if err := configUnmarshaller(conn.Config, &rawMap); err != nil {
 				return fmt.Errorf("unmarshal config for env expansion: %v", err)
 			}
 
@@ -492,7 +502,7 @@ func (c *Connector) UnmarshalJSON(b []byte) error {
 			data = expandedData
 		}
 
-		if err := json.Unmarshal(data, connConfig); err != nil {
+		if err := configUnmarshaller(data, connConfig); err != nil {
 			return fmt.Errorf("parse connector config: %v", err)
 		}
 	}

cmd/dex/serve.go

@@ -97,10 +97,16 @@ func runServe(options serveOptions) error {
 	}
 
 	var c Config
-	if err := yaml.Unmarshal(configData, &c); err != nil {
+
+	jsonConfigData, err := yaml.YAMLToJSON(configData)
+	if err != nil {
 		return fmt.Errorf("error parse config file %s: %v", configFile, err)
 	}
 
+	if err := configUnmarshaller(jsonConfigData, &c); err != nil {
+		return fmt.Errorf("error unmarshalling config file %s: %v", configFile, err)
+	}
+
 	applyConfigOverrides(options, &c)
 
 	logger, err := newLogger(c.Logger.Level, c.Logger.Format)

pkg/featureflags/set.go

@@ -14,4 +14,7 @@ var (
 
 	// ContinueOnConnectorFailure allows the server to start even if some connectors fail to initialize.
 	ContinueOnConnectorFailure = newFlag("continue_on_connector_failure", true)
+
+	// ConfigDisallowUnknownFields enables to forbid unknown fields in the config while unmarshaling.
+	ConfigDisallowUnknownFields = newFlag("config_disallow_unknown_fields", false)
 )

storage/etcd/config.go

@@ -15,10 +15,10 @@ var defaultDialTimeout = 2 * time.Second
 
 // SSL represents SSL options for etcd databases.
 type SSL struct {
-	ServerName string `json:"serverName" yaml:"serverName"`
-	CAFile     string `json:"caFile" yaml:"caFile"`
-	KeyFile    string `json:"keyFile" yaml:"keyFile"`
-	CertFile   string `json:"certFile" yaml:"certFile"`
+	ServerName string `json:"serverName"`
+	CAFile     string `json:"caFile"`
+	KeyFile    string `json:"keyFile"`
+	CertFile   string `json:"certFile"`
 }
 
 // Etcd options for connecting to etcd databases.
@@ -26,11 +26,11 @@ type SSL struct {
 // configure an etcd namespace either via Namespace field or using `etcd grpc-proxy
 // --namespace=<prefix>`
 type Etcd struct {
-	Endpoints []string `json:"endpoints" yaml:"endpoints"`
-	Namespace string   `json:"namespace" yaml:"namespace"`
-	Username  string   `json:"username" yaml:"username"`
-	Password  string   `json:"password" yaml:"password"`
-	SSL       SSL      `json:"ssl" yaml:"ssl"`
+	Endpoints []string `json:"endpoints"`
+	Namespace string   `json:"namespace"`
+	Username  string   `json:"username"`
+	Password  string   `json:"password"`
+	SSL       SSL      `json:"ssl"`
 }
 
 // Open creates a new storage implementation backed by Etcd

storage/sql/config.go

@@ -78,7 +78,7 @@ type SSL struct {
 type Postgres struct {
 	NetworkDB
 
-	SSL SSL `json:"ssl" yaml:"ssl"`
+	SSL SSL `json:"ssl"`
 }
 
 // Open creates a new storage implementation backed by Postgres.
@@ -206,7 +206,7 @@ func (p *Postgres) open(logger *slog.Logger) (*conn, error) {
 type MySQL struct {
 	NetworkDB
 
-	SSL SSL `json:"ssl" yaml:"ssl"`
+	SSL SSL `json:"ssl"`
 
 	// TODO(pborzenkov): used by tests to reduce lock wait timeout. Should
 	// we make it exported and allow users to provide arbitrary params?

storage/storage.go

@@ -149,28 +149,28 @@ type Storage interface {
 //   - Public clients: https://developers.google.com/api-client-library/python/auth/installed-app
 type Client struct {
 	// Client ID and secret used to identify the client.
-	ID        string `json:"id" yaml:"id"`
-	IDEnv     string `json:"idEnv" yaml:"idEnv"`
-	Secret    string `json:"secret" yaml:"secret"`
-	SecretEnv string `json:"secretEnv" yaml:"secretEnv"`
+	ID        string `json:"id"`
+	IDEnv     string `json:"idEnv"`
+	Secret    string `json:"secret"`
+	SecretEnv string `json:"secretEnv"`
 
 	// A registered set of redirect URIs. When redirecting from dex to the client, the URI
 	// requested to redirect to MUST match one of these values, unless the client is "public".
-	RedirectURIs []string `json:"redirectURIs" yaml:"redirectURIs"`
+	RedirectURIs []string `json:"redirectURIs"`
 
 	// TrustedPeers are a list of peers which can issue tokens on this client's behalf using
 	// the dynamic "oauth2:server:client_id:(client_id)" scope. If a peer makes such a request,
 	// this client's ID will appear as the ID Token's audience.
 	//
 	// Clients inherently trust themselves.
-	TrustedPeers []string `json:"trustedPeers" yaml:"trustedPeers"`
+	TrustedPeers []string `json:"trustedPeers"`
 
 	// Public clients must use either use a redirectURL 127.0.0.1:X or "urn:ietf:wg:oauth:2.0:oob"
-	Public bool `json:"public" yaml:"public"`
+	Public bool `json:"public"`
 
 	// Name and LogoURL used when displaying this client to the end user.
-	Name    string `json:"name" yaml:"name"`
-	LogoURL string `json:"logoURL" yaml:"logoURL"`
+	Name    string `json:"name"`
+	LogoURL string `json:"logoURL"`
 }
 
 // Claims represents the ID Token claims supported by the server.