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Merge pull request github#10684 from joefarebrother/android-keyboard-cache
Java: Add query for Sensitive Keyboard Cache
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‎java/ql/lib/semmle/code/java/security/SensitiveKeyboardCacheQuery.qll

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/** Definitions for the keyboard cache query */
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import java
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import semmle.code.java.dataflow.DataFlow
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import semmle.code.java.security.SensitiveActions
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import semmle.code.xml.AndroidManifest
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/** An Android Layout XML file. */
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private class AndroidLayoutXmlFile extends XmlFile {
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AndroidLayoutXmlFile() { this.getRelativePath().matches("%/res/layout/%.xml") }
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}
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/** A component declared in an Android layout file. */
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class AndroidLayoutXmlElement extends XmlElement {
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AndroidXmlAttribute id;
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AndroidLayoutXmlElement() {
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this.getFile() instanceof AndroidLayoutXmlFile and
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id = this.getAttribute("id")
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}
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/** Gets the ID of this component. */
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string getId() { result = id.getValue() }
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/** Gets the class of this component. */
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Class getClass() {
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this.getName() = "view" and
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this.getAttribute("class").getValue() = result.getQualifiedName()
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or
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this.getName() = result.getQualifiedName()
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or
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result.hasQualifiedName(["android.widget", "android.view"], this.getName())
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}
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}
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/** An XML element that represents an editable text field. */
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class AndroidEditableXmlElement extends AndroidLayoutXmlElement {
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AndroidEditableXmlElement() {
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this.getClass().getASourceSupertype*().hasQualifiedName("android.widget", "EditText")
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}
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/** Gets the input type of this field, if any. */
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string getInputType() { result = this.getAttribute("inputType").(AndroidXmlAttribute).getValue() }
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}
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/** A `findViewById` or `requireViewById` method on `Activity` or `View`. */
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private class FindViewMethod extends Method {
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FindViewMethod() {
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this.hasQualifiedName("android.view", "View", ["findViewById", "requireViewById"])
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or
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exists(Method m |
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m.hasQualifiedName("android.app", "Activity", ["findViewById", "requireViewById"]) and
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this = m.getAnOverride*()
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)
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}
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}
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/** Gets a use of the view that has the given id. */
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private MethodAccess getAUseOfViewWithId(string id) {
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exists(string name, NestedClass r_id, Field id_field |
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id = "@+id/" + name and
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result.getMethod() instanceof FindViewMethod and
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r_id.getEnclosingType().hasName("R") and
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r_id.hasName("id") and
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id_field.getDeclaringType() = r_id and
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id_field.hasName(name)
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|
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DataFlow::localExprFlow(id_field.getAnAccess(), result.getArgument(0))
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)
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}
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/** Gets the argument of a use of `setInputType` called on the view with the given id. */
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private Argument setInputTypeForId(string id) {
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exists(MethodAccess setInputType |
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setInputType.getMethod().hasQualifiedName("android.widget", "TextView", "setInputType") and
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DataFlow::localExprFlow(getAUseOfViewWithId(id), setInputType.getQualifier()) and
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result = setInputType.getArgument(0)
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)
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}
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/** Holds if the given field is a constant flag indicating that an input with this type will not be cached. */
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private predicate inputTypeFieldNotCached(Field f) {
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f.getDeclaringType().hasQualifiedName("android.text", "InputType") and
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(
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not f.getName().matches("%TEXT%")
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or
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f.getName().matches("%PASSWORD%")
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or
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f.hasName("TYPE_TEXT_FLAG_NO_SUGGESTIONS")
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)
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}
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/** Configuration that finds uses of `setInputType` for non cached fields. */
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private class GoodInputTypeConf extends DataFlow::Configuration {
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GoodInputTypeConf() { this = "GoodInputTypeConf" }
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override predicate isSource(DataFlow::Node node) {
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inputTypeFieldNotCached(node.asExpr().(FieldAccess).getField())
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}
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override predicate isSink(DataFlow::Node node) { node.asExpr() = setInputTypeForId(_) }
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override predicate isAdditionalFlowStep(DataFlow::Node node1, DataFlow::Node node2) {
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exists(OrBitwiseExpr bitOr |
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node1.asExpr() = bitOr.getAChildExpr() and
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node2.asExpr() = bitOr
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)
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}
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}
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/** Gets a regex indicating that an input field may contain sensitive data. */
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private string getInputSensitiveInfoRegex() {
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result =
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[
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getCommonSensitiveInfoRegex(),
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"(?i).*(bank|credit|debit|(pass(wd|word|code|phrase))|security).*"
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]
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}
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/** Holds if input using the given input type (as written in XML) is not stored in the keyboard cache. */
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bindingset[ty]
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private predicate inputTypeNotCached(string ty) {
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not ty.matches("%text%")
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or
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ty.regexpMatch("(?i).*(nosuggestions|password).*")
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}
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/** Gets an input field whose contents may be sensitive and may be stored in the keyboard cache. */
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AndroidEditableXmlElement getASensitiveCachedInput() {
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result.getId().regexpMatch(getInputSensitiveInfoRegex()) and
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(
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not inputTypeNotCached(result.getInputType()) and
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not exists(GoodInputTypeConf conf, DataFlow::Node src, DataFlow::Node sink |
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conf.hasFlow(src, sink) and
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sink.asExpr() = setInputTypeForId(result.getId())
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)
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)
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}

‎java/ql/src/Security/CWE/CWE-524/Example.xml

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<?xml version="1.0" encoding="utf-8"?>
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<LinearLayout
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xmlns:android="http://schemas.android.com/apk/res/android"
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xmlns:app="http://schemas.android.com/apk/res-auto">
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<!-- BAD: This password field uses the `text` input type, which allows the input to be saved to the keyboard cache. -->
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<EditText
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android:id="@+id/password_bad"
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android:inputType="text"/>
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<!-- GOOD: This password field uses the `textPassword` input type, which ensures that the input is not saved to the keyboard cache. -->
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<EditText
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android:id="@+id/password_good"
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android:inputType="textPassword"/>
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</LinearLayout>

‎java/ql/src/Security/CWE/CWE-524/SensitiveKeyboardCache.qhelp

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<!DOCTYPE qhelp PUBLIC
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"-//Semmle//qhelp//EN"
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"qhelp.dtd">
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<qhelp>
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<overview>
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<p>When a user enters information in a text input field on an Android application, their input is saved to a keyboard cache which provides autocomplete suggestions and predictions. There is a risk that sensitive user data, such as passwords or banking information, may be leaked to other applications via the keyboard cache.</p>
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</overview>
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<recommendation>
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<p>For input fields expected to accept sensitive information, use input types such as <code>"textNoSuggestions"</code> (or <code>"textPassword"</code> for a password) to ensure the input does not get stored in the keyboard cache.</p>
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<p>Optionally, instead of declaring an input type through XML, you can set the input type in your code using <code>TextView.setInputType()</code>.</p>
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</recommendation>
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<example>
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<p>In the following example, the field labeled BAD allows the password to be saved to the keyboard cache,
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whereas the field labeled GOOD uses the <code>"textPassword"</code> input type to ensure the password is not cached.</p>
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<sample src="Example.xml" />
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</example>
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<references>
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<li>
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OWASP Mobile Application Security Testing Guide: <a href="https://github.com/OWASP/owasp-mastg/blob/b7a93a2e5e0557cc9a12e55fc3f6675f6986bb86/Document/0x05d-Testing-Data-Storage.md#determining-whether-the-keyboard-cache-is-disabled-for-text-input-fields-mstg-storage-5">Determining Whether the Keyboard Cache Is Disabled for Text Input Fields</a>.
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</li>
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<li>
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Android Developers: <a href="https://developer.android.com/reference/android/widget/TextView#attr_android:inputType">android:inputType attribute documentation.</a>
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</li>
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</references>
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</qhelp>

‎java/ql/src/Security/CWE/CWE-524/SensitiveKeyboardCache.ql

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/**
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* @name Android sensitive keyboard cache
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* @description Allowing the keyboard to cache sensitive information may result in information leaks to other applications.
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* @kind problem
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* @problem.severity warning
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* @security-severity 8.1
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* @id java/android/sensitive-keyboard-cache
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* @tags security
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* external/cwe/cwe-524
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* @precision medium
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*/
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import java
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import semmle.code.java.security.SensitiveKeyboardCacheQuery
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from AndroidEditableXmlElement el
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where el = getASensitiveCachedInput()
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select el, "This input field may contain sensitive information that is saved to the keyboard cache."

‎java/ql/src/change-notes/2022-10-07-sensitive-keyboard-cache.md

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---
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category: newQuery
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---
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* Added a new query, `java/android/sensitive-keyboard-cache`, to detect instances of sensitive information possibly being saved to the keyboard cache.

‎java/ql/test/query-tests/security/CWE-524/AndroidManifest.xml

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<?xml version="1.0" encoding="utf-8"?>
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<manifest xmlns:android="http://schemas.android.com/apk/res/android"
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xmlns:tools="http://schemas.android.com/tools"
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package="com.example.test">
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</manifest>

‎java/ql/test/query-tests/security/CWE-524/R.java

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package com.example.test;
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public final class R {
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public static final class id {
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public static final int test7_password = 1;
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public static final int test8_password = 2;
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}
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}

‎java/ql/test/query-tests/security/CWE-524/SensitiveKeyboardCache.expected

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‎java/ql/test/query-tests/security/CWE-524/SensitiveKeyboardCache.ql

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import java
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import semmle.code.java.security.SensitiveKeyboardCacheQuery
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import TestUtilities.InlineExpectationsTest
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class SensitiveKeyboardCacheTest extends InlineExpectationsTest {
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SensitiveKeyboardCacheTest() { this = "SensitiveKeyboardCacheTest" }
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override string getARelevantTag() { result = "hasResult" }
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override predicate hasActualResult(Location loc, string element, string tag, string value) {
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exists(AndroidEditableXmlElement el |
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el = getASensitiveCachedInput() and
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loc = el.getLocation() and
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element = el.toString() and
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tag = "hasResult" and
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value = ""
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)
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}
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}

‎java/ql/test/query-tests/security/CWE-524/Test.java

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package com.example.test;
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import android.app.Activity;
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import android.os.Bundle;
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import android.widget.EditText;
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import android.view.View;
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import android.text.InputType;
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class Test extends Activity {
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public void onCreate(Bundle b) {
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EditText test7pw = findViewById(R.id.test7_password);
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test7pw.setInputType(InputType.TYPE_CLASS_TEXT | InputType.TYPE_TEXT_FLAG_NO_SUGGESTIONS);
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EditText test8pw = requireViewById(R.id.test8_password);
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test8pw.setInputType(InputType.TYPE_CLASS_TEXT | InputType.TYPE_TEXT_VARIATION_PASSWORD);
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}
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}

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