Allow S3 buckets in different regions, implements #2007

This commit allows additional configuration
for the `audit_sessions_uri` parameter:

`audit_sessions_uri: s3://example.com/path?region=us-east-1`

Additional query parameter `region` will override
default `audit` section `region` if set.

constants.go

@@ -277,6 +277,9 @@ const (
 	// storage
 	SchemeS3 = "s3"
 
+	// Region is AWS region parameter
+	Region = "region"
+
 	// SchemeFile is a local disk file storage
 	SchemeFile = "file"
 

lib/events/s3sessions/s3handler.go

@@ -88,7 +88,7 @@ func NewHandler(cfg Config) (*Handler, error) {
 		client:     s3.New(cfg.Session),
 	}
 	start := time.Now()
-	h.Infof("Setting up bucket %q.", h.Bucket)
+	h.Infof("Setting up bucket %q, sessions path %q in region %q.", h.Bucket, h.Path, h.Region)
 	if err := h.ensureBucket(); err != nil {
 		return nil, trace.Wrap(err)
 	}

lib/service/service.go

@@ -730,9 +730,13 @@ func initUploadHandler(auditConfig services.AuditConfig) (events.UploadHandler,
 
 	switch uri.Scheme {
 	case teleport.SchemeS3:
+		region := auditConfig.Region
+		if uriRegion := uri.Query().Get(teleport.Region); uriRegion != "" {
+			region = uriRegion
+		}
 		handler, err := s3sessions.NewHandler(s3sessions.Config{
 			Bucket: uri.Host,
-			Region: auditConfig.Region,
+			Region: region,
 			Path:   uri.Path,
 		})
 		if err != nil {