Refactor backend code (#509)

* separate spire and tornjak APIs

Signed-off-by: Maia Iyer <maia.raj.iyer@gmail.com>

* refactored api/agent/server.go

Signed-off-by: Maia Iyer <maia.raj.iyer@gmail.com>

* Fix CodeQL check

Signed-off-by: Maia Iyer <maia.raj.iyer@gmail.com>

* nit indentation

Signed-off-by: Maia Iyer <maia.raj.iyer@gmail.com>

---------

Signed-off-by: Maia Iyer <maia.raj.iyer@gmail.com>

Author: maia-iyer

api/agent/config.go

@@ -0,0 +1,267 @@
+package api
+
+import (
+	"fmt"
+	"strings"
+	"time"
+
+	backoff "github.com/cenkalti/backoff/v4"
+	"github.com/hashicorp/hcl"
+	"github.com/hashicorp/hcl/hcl/ast"
+	"github.com/hashicorp/hcl/hcl/token"
+	"github.com/pkg/errors"
+
+	"github.com/spiffe/tornjak/pkg/agent/authentication/authenticator"
+	"github.com/spiffe/tornjak/pkg/agent/authorization"
+	agentdb "github.com/spiffe/tornjak/pkg/agent/db"
+)
+
+func stringFromToken(keyToken token.Token) (string, error) {
+	switch keyToken.Type {
+	case token.STRING, token.IDENT:
+	default:
+		return "", fmt.Errorf("expected STRING or IDENT but got %s", keyToken.Type)
+	}
+	value := keyToken.Value()
+	stringValue, ok := value.(string)
+	if !ok {
+		// purely defensive
+		return "", fmt.Errorf("expected %T but got %T", stringValue, value)
+	}
+	return stringValue, nil
+}
+
+// getPluginConfig returns first plugin configuration
+func getPluginConfig(plugin *ast.ObjectItem) (string, ast.Node, error) {
+	// extract plugin name and value
+	pluginName, err := stringFromToken(plugin.Keys[1].Token)
+	if err != nil {
+		return "", nil, fmt.Errorf("invalid plugin type name %q: %w", plugin.Keys[1].Token.Text, err)
+	}
+	// extract data
+	var hclPluginConfig hclPluginConfig
+	if err := hcl.DecodeObject(&hclPluginConfig, plugin.Val); err != nil {
+		return "", nil, fmt.Errorf("failed to decode plugin config for %q: %w", pluginName, err)
+	}
+	return pluginName, hclPluginConfig.PluginData, nil
+}
+
+// NewAgentsDB returns a new agents DB, given a DB connection string
+func NewAgentsDB(dbPlugin *ast.ObjectItem) (agentdb.AgentDB, error) {
+	key, data, err := getPluginConfig(dbPlugin)
+	if err != nil { // db is required config
+		return nil, errors.New("Required DataStore plugin not configured")
+	}
+
+	switch key {
+	case "sql":
+		// check if data is defined
+		if data == nil {
+			return nil, errors.New("SQL DataStore plugin ('config > plugins > DataStore sql > plugin_data') not populated")
+		}
+		fmt.Printf("SQL DATASTORE DATA: %+v\n", data)
+
+		// TODO can probably add this to config
+		expBackoff := backoff.NewExponentialBackOff()
+		expBackoff.MaxElapsedTime = time.Second
+
+		// decode config to struct
+		var config pluginDataStoreSQL
+		if err := hcl.DecodeObject(&config, data); err != nil {
+			return nil, errors.Errorf("Couldn't parse DB config: %v", err)
+		}
+
+		// create db
+		drivername := config.Drivername
+		dbfile := config.Filename
+
+		db, err := agentdb.NewLocalSqliteDB(drivername, dbfile, expBackoff)
+		if err != nil {
+			return nil, errors.Errorf("Could not start DB driver %s, filename: %s: %v", drivername, dbfile, err)
+		}
+		return db, nil
+	default:
+		return nil, errors.Errorf("Couldn't create datastore")
+	}
+}
+
+// NewAuthenticator returns a new Authenticator
+func NewAuthenticator(authenticatorPlugin *ast.ObjectItem) (authenticator.Authenticator, error) {
+	key, data, _ := getPluginConfig(authenticatorPlugin)
+
+	switch key {
+	case "Keycloak":
+		// check if data is defined
+		if data == nil {
+			return nil, errors.New("Keycloak Authenticator plugin ('config > plugins > Authenticator Keycloak > plugin_data') not populated")
+		}
+		fmt.Printf("Authenticator Keycloak Plugin Data: %+v\n", data)
+		// decode config to struct
+		var config pluginAuthenticatorKeycloak
+		if err := hcl.DecodeObject(&config, data); err != nil {
+			return nil, errors.Errorf("Couldn't parse Authenticator config: %v", err)
+		}
+
+		// Log warning if audience is nil that aud claim is not checked
+		if config.Audience == "" {
+			fmt.Println("WARNING: Auth plugin has no expected audience configured - `aud` claim will not be checked (please populate 'config > plugins > UserManagement KeycloakAuth > plugin_data > audience')")
+		}
+
+		// create authenticator TODO make json an option?
+		authenticator, err := authenticator.NewKeycloakAuthenticator(true, config.IssuerURL, config.Audience)
+		if err != nil {
+			return nil, errors.Errorf("Couldn't configure Authenticator: %v", err)
+		}
+		return authenticator, nil
+	default:
+		return nil, errors.Errorf("Invalid option for Authenticator named %s", key)
+	}
+}
+
+// NewAuthorizer returns a new Authorizer
+func NewAuthorizer(authorizerPlugin *ast.ObjectItem) (authorization.Authorizer, error) {
+	key, data, _ := getPluginConfig(authorizerPlugin)
+
+	switch key {
+	case "RBAC":
+		// check if data is defined
+		if data == nil {
+			return nil, errors.New("RBAC Authorizer plugin ('config > plugins > Authorizer RBAC > plugin_data') not populated")
+		}
+		fmt.Printf("Authorizer RBAC Plugin Data: %+v\n", data)
+
+		// decode config to struct
+		var config pluginAuthorizerRBAC
+		if err := hcl.DecodeObject(&config, data); err != nil {
+			return nil, errors.Errorf("Couldn't parse Authorizer config: %v", err)
+		}
+
+		// decode into role list and apiMapping
+		roleList := make(map[string]string)
+		apiMapping := make(map[string][]string)
+		apiV1Mapping := make(map[string]map[string][]string)
+		for _, role := range config.RoleList {
+			roleList[role.Name] = role.Desc
+			// print warning for empty string
+			if role.Name == "" {
+				fmt.Println("WARNING: using the empty string for an API enables access to all authenticated users")
+			}
+		}
+		for _, api := range config.APIRoleMappings {
+			apiMapping[api.Name] = api.AllowedRoles
+			fmt.Printf("API name: %s, Allowed Roles: %s \n", api.Name, api.AllowedRoles)
+		}
+		for _, apiV1 := range config.APIv1RoleMappings {
+			arr := strings.Split(apiV1.Name, " ")
+			apiV1.Method = arr[0]
+			apiV1.Path = arr[1]
+			fmt.Printf("API V1 method: %s, API V1 path: %s, API V1 allowed roles: %s \n", apiV1.Method, apiV1.Path, apiV1.AllowedRoles)
+			if _, ok := apiV1Mapping[apiV1.Path]; ok {
+				apiV1Mapping[apiV1.Path][apiV1.Method] = apiV1.AllowedRoles
+			} else {
+				apiV1Mapping[apiV1.Path] = map[string][]string{apiV1.Method: apiV1.AllowedRoles}
+			}
+		}
+		fmt.Printf("API V1 Mapping: %+v\n", apiV1Mapping)
+
+		authorizer, err := authorization.NewRBACAuthorizer(config.Name, roleList, apiMapping, apiV1Mapping)
+		if err != nil {
+			return nil, errors.Errorf("Couldn't configure Authorizer: %v", err)
+		}
+		return authorizer, nil
+	default:
+		return nil, errors.Errorf("Invalid option for Authorizer named %s", key)
+	}
+}
+
+func (s *Server) VerifyConfiguration() error {
+	if s.TornjakConfig == nil {
+		return errors.New("config not given")
+	}
+
+	/*  Verify server  */
+	if s.TornjakConfig.Server == nil { // must be defined
+		return errors.New("'config > server' field not defined")
+	}
+	if s.TornjakConfig.Server.SPIRESocket == "" {
+		return errors.New("'config > server > spire_socket_path' field not defined")
+	}
+
+	/*  Verify Plugins  */
+	if s.TornjakConfig.Plugins == nil {
+		return errors.New("'config > plugins' field not defined")
+	}
+	return nil
+}
+
+func (s *Server) ConfigureDefaults() error {
+	// no authorization is a default
+	s.Authenticator = authenticator.NewNullAuthenticator()
+	s.Authorizer = authorization.NewNullAuthorizer()
+	return nil
+}
+
+func (s *Server) Configure() error {
+	// Verify Config
+	err := s.VerifyConfiguration()
+	if err != nil {
+		return errors.Errorf("Tornjak Config error: %v", err)
+	}
+
+	/*  Configure Server  */
+	serverConfig := s.TornjakConfig.Server
+	s.SpireServerAddr = serverConfig.SPIRESocket // for convenience
+
+	/*  Configure Plugins  */
+	// configure defaults for optional plugins, reconfigured if given
+	// TODO maybe we should not have this step at all
+	// This is a temporary work around for optional plugin configs
+	err = s.ConfigureDefaults()
+	if err != nil {
+		return errors.Errorf("Tornjak Config error: %v", err)
+	}
+
+	pluginConfigs := *s.TornjakConfig.Plugins
+	pluginList, ok := pluginConfigs.(*ast.ObjectList)
+	if !ok {
+		return fmt.Errorf("expected plugins node type %T but got %T", pluginList, pluginConfigs)
+	}
+
+	// iterate over plugin list
+
+	for _, pluginObject := range pluginList.Items {
+		if len(pluginObject.Keys) != 2 {
+			return fmt.Errorf("plugin item expected to have two keys (type then name)")
+		}
+
+		pluginType, err := stringFromToken(pluginObject.Keys[0].Token)
+		if err != nil {
+			return fmt.Errorf("invalid plugin type key %q: %w", pluginObject.Keys[0].Token.Text, err)
+		}
+
+		// create plugin component based on type
+		switch pluginType {
+		// configure datastore
+		case "DataStore":
+			s.Db, err = NewAgentsDB(pluginObject)
+			if err != nil {
+				return errors.Errorf("Cannot configure datastore plugin: %v", err)
+			}
+		// configure Authenticator
+		case "Authenticator":
+			s.Authenticator, err = NewAuthenticator(pluginObject)
+			if err != nil {
+				return errors.Errorf("Cannot configure Authenticator plugin: %v", err)
+			}
+		// configure Authorizer
+		case "Authorizer":
+			s.Authorizer, err = NewAuthorizer(pluginObject)
+			if err != nil {
+				return errors.Errorf("Cannot configure Authorizer plugin: %v", err)
+			}
+		}
+		// TODO Handle when multiple plugins configured
+	}
+
+	return nil
+}