Implementation of an Android Framework for USB storage access without root rights

TL;DR

This paper presents the development of an Android framework enabling USB mass storage device access without root privileges, focusing on FAT32 file system support and practical implementation details.

Contribution

It introduces a novel Android framework for USB mass storage access without root rights, including architecture, implementation, and testing across devices.

Findings

Framework successfully accesses USB storage devices on Android without root

Supports FAT32 file system for common external storage

Demonstrates compatibility across various Android devices

Abstract

This bachelor thesis describes the implementation of an Android framework to access mass storage devices over the USB interface of a smartphone. First the basics of USB (i.e. interfaces, endpoints and USB On the go) and accessing USB devices via the official Android API are discussed. Next the USB mass storage class is explained, which was de- signed by the USB-IF to access mobile mass storage like USB pen drives or external HDDs. For communication with mass storage devices, most important are the bulk-only transfer and the SCSI transparent command set. Furthermore file systems, for accessing directo- ries and files, are described. This thesis focuses on the FAT32 file system from Microsoft, because it is the most commonly used file system on such devices. After the theory part it is time to look at the implementation of the framework. In this section, the first concern is the purpose in general. Then the architecture of the framework and the actual implementation are presented. Important parts are discussed in detail. The thesis finishes with an overview of the test results on various Android devices, a short conclusion and an outlook to future developments. Moreover the current status of the developed framework is visualized.