Implement an append only mode.

README.md

@@ -43,6 +43,7 @@ Usage:
   rest-server [flags]
 
 Flags:
+      --append-only         Enable append only mode
       --cpuprofile string   write CPU profile to file
       --debug               output debug messages
   -h, --help                help for rest-server
@@ -88,6 +89,9 @@ keys with the following commands:
 % openssl req -new -x509 -key private_key -out public_key -days 365
 ```
 
+Append only mode allows creation of new backups but prevents deletion and modification of existing backups. This
+can be useful when backing up systems that have a potential of being hacked.
+
 Rest Server uses exactly the same directory structure as local backend, so you should be able to access it both locally
 and via HTTP, even simultaneously.
 

cmd/rest-server/main.go

@@ -29,6 +29,7 @@ func init() {
 	flags.StringVar(&restserver.Config.Log, "log", restserver.Config.Log, "log HTTP requests in the combined log format")
 	flags.StringVar(&restserver.Config.Path, "path", restserver.Config.Path, "data directory")
 	flags.BoolVar(&restserver.Config.TLS, "tls", restserver.Config.TLS, "turn on TLS support")
+	flags.BoolVar(&restserver.Config.AppendOnly, "append-only", restserver.Config.AppendOnly, "Enable append only mode")
 }
 
 var version = "manually"

handlers.go

@@ -194,6 +194,12 @@ func DeleteConfig(w http.ResponseWriter, r *http.Request) {
 	if Config.Debug {
 		log.Println("DeleteConfig()")
 	}
+
+	if Config.AppendOnly {
+		http.Error(w, http.StatusText(http.StatusForbidden), http.StatusForbidden)
+		return
+	}
+
 	cfg, err := getPath(r, "config")
 	if err != nil {
 		http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)
@@ -372,6 +378,11 @@ func DeleteBlob(w http.ResponseWriter, r *http.Request) {
 		log.Println("DeleteBlob()")
 	}
 
+	if Config.AppendOnly && pat.Param(r, "type") != "locks" {
+		http.Error(w, http.StatusText(http.StatusForbidden), http.StatusForbidden)
+		return
+	}
+
 	path, err := getFilePath(r, pat.Param(r, "type"), pat.Param(r, "name"))
 	if err != nil {
 		http.Error(w, http.StatusText(http.StatusInternalServerError), http.StatusInternalServerError)

mux.go

@@ -18,9 +18,11 @@ var Config = struct {
 	Log        string
 	CPUProfile string
 	Debug      bool
+	AppendOnly bool
 }{
 	Path:   "/tmp/restic",
 	Listen: ":8000",
+	AppendOnly: false,
 }
 
 func debugHandler(next http.Handler) http.Handler {