diff --git a/NetfluxWebsocketSrv.js b/NetfluxWebsocketSrv.js
index 0108659fb..2d894a5c0 100644
--- a/NetfluxWebsocketSrv.js
+++ b/NetfluxWebsocketSrv.js
@@ -214,7 +214,7 @@ const handleMessage = function (ctx, user, msg) {
                 var rpc_call = parsed.slice(1);
 
                 // slice off the sequence number and pass in the rest of the message
-                ctx.rpc(rpc_call, function (err, output) {
+                ctx.rpc(ctx, rpc_call, function (err, output) {
                     if (err) {
                         console.error('[' + err + ']', output); // TODO make this disableable
                         sendMsg(ctx, user, [seq, 'ACK']);
diff --git a/rpc.js b/rpc.js
index 66973039b..053d8cf6e 100644
--- a/rpc.js
+++ b/rpc.js
@@ -11,11 +11,15 @@ var getHash = function (ctx, cb) { };
 var getTotalSize = function (ctx, cb) { };
 var getFileSize = function (ctx, cb) { };
 
+var isValidChannel = function (chan) {
+    return /^[a-fA-F0-9]/.test(chan);
+};
+
 RPC.create = function (config, cb) {
     // load pin-store...
 
     console.log('loading rpc module...');
-    rpc = function (msg, respond) {
+    rpc = function (ctx, msg, respond) {
         switch (msg[0]) {
             case 'ECHO':
                 respond(void 0, msg);
@@ -25,7 +29,14 @@ RPC.create = function (config, cb) {
             case 'GET_HASH':
             case 'GET_TOTAL_SIZE':
             case 'GET_FILE_SIZE':
-
+                if (!isValidChannel(msg[1])) {
+                    return void respond('INVALID_CHAN');
+                }
+
+                return void ctx.store.getChannelSize(msg[1], function (e, size) {
+                    if (e) { return void respond(e.code); }
+                    respond(void 0, size);
+                });
             default:
                 respond('UNSUPPORTED_RPC_CALL', msg);
                 break;