Throw if mismatched size when unserializing an array buffer

An exception will be thrown if the length of an unserialized
array buffer does not match exactly the original size at
serialization time.

src/js/storage.js

@@ -1020,8 +1020,7 @@ self.addEventListener('hiddenSettingsChanged', ( ) => {
             return;
         }
     } catch (ex) {
-        console.error(ex);
-        return;
+        log.info(ex);
     }
 
     const result = await this.assets.get(this.pslAssetKey);

src/js/utils.js

@@ -555,16 +555,19 @@
         const inbuf = new Uint32Array(arrbuf, 0, inputLength);
         const outputLength = this.magic.length + 7 + inputLength * 7;
         const outbuf = new Uint8Array(outputLength);
+        // magic bytes
         let j = 0;
         for ( let i = 0; i < this.magic.length; i++ ) {
             outbuf[j++] = this.magic.charCodeAt(i);
         }
+        // array size
         let v = inputLength;
         do {
             outbuf[j++] = this.valToDigit[v & 0b111111];
             v >>>= 6;
         } while ( v !== 0 );
         outbuf[j++] = 0x20 /* ' ' */;
+        // array content
         for ( let i = 0; i < inputLength; i++ ) {
             v = inbuf[i];
             do {
@@ -596,16 +599,18 @@
             throw new Error('Invalid µBlock.base64 encoding');
         }
         const inputLength = instr.length;
+        const outputLength = this.decodeSize(instr) >> 2;
         const outbuf = arrbuf instanceof ArrayBuffer === false
-            ? new Uint32Array(this.decodeSize(instr) >> 2)
+            ? new Uint32Array(outputLength)
             : new Uint32Array(arrbuf);
         let i = instr.indexOf(' ', this.magic.length) + 1;
         if ( i === -1 ) {
             throw new Error('Invalid µBlock.base64 encoding');
         }
+        // array content
         let j = 0;
         for (;;) {
-            if ( i === inputLength ) { break; }
+            if ( j === outputLength || i >= inputLength ) { break; }
             let v = 0, l = 0;
             for (;;) {
                 const c = instr.charCodeAt(i++);
@@ -615,6 +620,9 @@
             }
             outbuf[j++] = v;
         }
+        if ( i < inputLength || j < outputLength ) {
+            throw new Error('Invalid µBlock.base64 encoding');
+        }
         return outbuf;
     }