Insecure SD-Card / External Storage

← Insecure Data Storage

insecure_sdcard_external_storage   EASY

CategoryInsecure Data Storage
OWASP Mobile (2024)M9
MASVSMASVS-STORAGE-1MASVS-STORAGE-2
MASWEMASWE-0002
MASTG (v2 tests)iOSNoneAndroidMASTG-TEST-0200MASTG-TEST-0201MASTG-TEST-0202
MASTG demosiOSNoneAndroidMASTG-DEMO-0003MASTG-DEMO-0001
CWECWE-312CWE-921
PlatformAndroid

Description

Writes sensitive files to shared/external storage where any app with storage access can read them.

How it works

The secret is written as a cleartext file into shared / external storage. On a real device, external storage is world-readable to any app with storage access (and to adb or any file-manager app), so the file leaks the moment it is written; on Android it goes into the external files directory, elsewhere into app documents. Sensitive data must stay in app-private, encrypted storage.

How to exercise it. DVMA is the harness - open this module from the home index and tap the demo action. The screen ships the malicious input and simulates the attacker (e.g. the companion app, crafted intent, or scanned payload) in-process, and the evidence panel prints the proof. The Tools (optional) and Attack inputs below are only needed to reproduce the exploit end-to-end on a real device.

Exploit steps

  1. Set up. Build DVMA with a flavor that enables the Insecure Data Storage category (e.g. --dart-define-from-file=config/flavors/dev.json) and run on an Android emulator you control. The demo needs no external tooling; for the optional on-device reproduction the relevant tools are: adb, run-as, objection, SharedPreferences/XML inspection, sqlite3.
  2. Locate the target. From the home index, open Insecure SD-Card / External Storage (insecure_sdcard_external_storage). The How it works section above describes this module’s specific weakness; the screen states the intended-secure behavior and exposes the vulnerable action.
  3. Exploit. Exercise the flow that persists data, then inspect on-device storage (adb shell run-as <pkg> / pull the app sandbox, or objection’s android keystore/ios nsuserdefaults helpers) and confirm the sensitive value is present in cleartext or without hardware backing.
  4. Observe the evidence. Trigger the vulnerable action and read the evidence panel - it prints the concrete proof (leaked value, accepted replay, executed payload, or unauthorized result).
  5. Contrast with the secure path. Run the module’s secure/hardened action (where provided) and confirm the same attack is rejected - this is what a correct implementation should do.
  6. Map it back. Cross-reference the MASTG v2 test(s) MASTG-TEST-0200, MASTG-TEST-0201, MASTG-TEST-0202 for the canonical procedure and remediation.

Tools (optional)