Introduce STS client grants API and OPA policy integration (#6168)

This PR introduces two new features

- AWS STS compatible STS API named AssumeRoleWithClientGrants

```
POST /?Action=AssumeRoleWithClientGrants&Token=<jwt>
```

This API endpoint returns temporary access credentials, access
tokens signature types supported by this API

  - RSA keys
  - ECDSA keys

Fetches the required public key from the JWKS endpoints, provides
them as rsa or ecdsa public keys.

- External policy engine support, in this case OPA policy engine

- Credentials are stored on disks

cmd/config-migrate.go

@@ -18,6 +18,7 @@ package cmd
 
 import (
 	"context"
+	"encoding/json"
 	"fmt"
 	"os"
 	"path"
@@ -29,6 +30,8 @@ import (
 	"github.com/minio/minio/pkg/dns"
 	"github.com/minio/minio/pkg/event"
 	"github.com/minio/minio/pkg/event/target"
+	"github.com/minio/minio/pkg/iam/policy"
+	"github.com/minio/minio/pkg/iam/validator"
 	xnet "github.com/minio/minio/pkg/net"
 	"github.com/minio/minio/pkg/quick"
 )
@@ -2410,7 +2413,7 @@ func migrateV27ToV28() error {
 	return nil
 }
 
-// Migrates '.minio.sys/config.json' to v30.
+// Migrates '.minio.sys/config.json' to v31.
 func migrateMinioSysConfig(objAPI ObjectLayer) error {
 	if err := migrateV27ToV28MinioSys(objAPI); err != nil {
 		return err
@@ -2418,73 +2421,167 @@ func migrateMinioSysConfig(objAPI ObjectLayer) error {
 	if err := migrateV28ToV29MinioSys(objAPI); err != nil {
 		return err
 	}
-	return migrateV29ToV30MinioSys(objAPI)
+	if err := migrateV29ToV30MinioSys(objAPI); err != nil {
+		return err
+	}
+	return migrateV30ToV31MinioSys(objAPI)
 }
 
-func migrateV29ToV30MinioSys(objAPI ObjectLayer) error {
+func checkConfigVersion(objAPI ObjectLayer, configFile string, version string) (bool, []byte, error) {
+	data, err := readConfig(context.Background(), objAPI, configFile)
+	if err != nil {
+		return false, nil, err
+	}
+
+	var versionConfig struct {
+		Version string `json:"version"`
+	}
+
+	vcfg := &versionConfig
+	if err = json.Unmarshal(data, vcfg); err != nil {
+		return false, nil, err
+	}
+	return vcfg.Version == version, data, nil
+}
+
+func migrateV27ToV28MinioSys(objAPI ObjectLayer) error {
 	configFile := path.Join(minioConfigPrefix, minioConfigFile)
-	srvConfig, err := readServerConfig(context.Background(), objAPI)
+	ok, data, err := checkConfigVersion(objAPI, configFile, "27")
 	if err == errConfigNotFound {
 		return nil
 	} else if err != nil {
 		return fmt.Errorf("Unable to load config file. %v", err)
 	}
-	if srvConfig.Version != "29" {
+	if !ok {
 		return nil
 	}
 
-	srvConfig.Version = "30"
-	// Init compression config.For future migration, Compression config needs to be copied over from previous version.
-	srvConfig.Compression.Enabled = false
-	srvConfig.Compression.Extensions = globalCompressExtensions
-	srvConfig.Compression.MimeTypes = globalCompressMimeTypes
-	if err = saveServerConfig(context.Background(), objAPI, srvConfig); err != nil {
-		return fmt.Errorf("Failed to migrate config from  29  to  30 . %v", err)
+	cfg := &serverConfigV28{}
+	if err = json.Unmarshal(data, cfg); err != nil {
+		return err
 	}
 
-	logger.Info(configMigrateMSGTemplate, configFile, "29", "30")
+	cfg.Version = "28"
+	cfg.KMS = crypto.KMSConfig{}
+
+	data, err = json.Marshal(cfg)
+	if err != nil {
+		return err
+	}
+
+	if err = saveConfig(context.Background(), objAPI, configFile, data); err != nil {
+		return fmt.Errorf("Failed to migrate config from ‘27’ to ‘28’. %v", err)
+	}
+
+	logger.Info(configMigrateMSGTemplate, configFile, "27", "28")
 	return nil
 }
 
 func migrateV28ToV29MinioSys(objAPI ObjectLayer) error {
 	configFile := path.Join(minioConfigPrefix, minioConfigFile)
-	srvConfig, err := readServerConfig(context.Background(), objAPI)
+
+	ok, data, err := checkConfigVersion(objAPI, configFile, "28")
 	if err == errConfigNotFound {
 		return nil
 	} else if err != nil {
 		return fmt.Errorf("Unable to load config file. %v", err)
 	}
-	if srvConfig.Version != "28" {
+	if !ok {
 		return nil
 	}
 
-	srvConfig.Version = "29"
-	if err = saveServerConfig(context.Background(), objAPI, srvConfig); err != nil {
-		return fmt.Errorf("Failed to migrate config from ‘28’ to ‘29’. %v", err)
+	cfg := &serverConfigV29{}
+	if err = json.Unmarshal(data, cfg); err != nil {
+		return err
+	}
+
+	cfg.Version = "29"
+	data, err = json.Marshal(cfg)
+	if err != nil {
+		return err
+	}
+
+	if err = saveConfig(context.Background(), objAPI, configFile, data); err != nil {
+		return fmt.Errorf("Failed to migrate config from ‘28’ to ‘29’. %v", err)
 	}
 
 	logger.Info(configMigrateMSGTemplate, configFile, "28", "29")
 	return nil
 }
 
-func migrateV27ToV28MinioSys(objAPI ObjectLayer) error {
+func migrateV29ToV30MinioSys(objAPI ObjectLayer) error {
 	configFile := path.Join(minioConfigPrefix, minioConfigFile)
-	srvConfig, err := readServerConfig(context.Background(), objAPI)
+
+	ok, data, err := checkConfigVersion(objAPI, configFile, "29")
 	if err == errConfigNotFound {
 		return nil
 	} else if err != nil {
 		return fmt.Errorf("Unable to load config file. %v", err)
 	}
-	if srvConfig.Version != "27" {
+	if !ok {
 		return nil
 	}
 
-	srvConfig.Version = "28"
-	srvConfig.KMS = crypto.KMSConfig{}
-	if err = saveServerConfig(context.Background(), objAPI, srvConfig); err != nil {
-		return fmt.Errorf("Failed to migrate config from ‘27’ to ‘28’. %v", err)
+	cfg := &serverConfigV30{}
+	if err = json.Unmarshal(data, cfg); err != nil {
+		return err
 	}
 
-	logger.Info(configMigrateMSGTemplate, configFile, "27", "28")
+	cfg.Version = "30"
+	// Init compression config.For future migration, Compression config needs to be copied over from previous version.
+	cfg.Compression.Enabled = false
+	cfg.Compression.Extensions = globalCompressExtensions
+	cfg.Compression.MimeTypes = globalCompressMimeTypes
+
+	data, err = json.Marshal(cfg)
+	if err != nil {
+		return err
+	}
+
+	if err = saveConfig(context.Background(), objAPI, configFile, data); err != nil {
+		return fmt.Errorf("Failed to migrate config from ‘29’ to ‘30’. %v", err)
+	}
+
+	logger.Info(configMigrateMSGTemplate, configFile, "29", "30")
+	return nil
+}
+
+func migrateV30ToV31MinioSys(objAPI ObjectLayer) error {
+	configFile := path.Join(minioConfigPrefix, minioConfigFile)
+
+	ok, data, err := checkConfigVersion(objAPI, configFile, "30")
+	if err == errConfigNotFound {
+		return nil
+	} else if err != nil {
+		return fmt.Errorf("Unable to load config file. %v", err)
+	}
+	if !ok {
+		return nil
+	}
+
+	cfg := &serverConfigV31{}
+	if err = json.Unmarshal(data, cfg); err != nil {
+		return err
+	}
+
+	cfg.Version = "31"
+	cfg.OpenID.JWKS = validator.JWKSArgs{
+		URL: &xnet.URL{},
+	}
+	cfg.Policy.OPA = iampolicy.OpaArgs{
+		URL:       &xnet.URL{},
+		AuthToken: "",
+	}
+
+	data, err = json.Marshal(cfg)
+	if err != nil {
+		return err
+	}
+
+	if err = saveConfig(context.Background(), objAPI, configFile, data); err != nil {
+		return fmt.Errorf("Failed to migrate config from ‘30’ to ‘31’. %v", err)
+	}
+
+	logger.Info(configMigrateMSGTemplate, configFile, "30", "31")
 	return nil
 }