The following table lists the Java development guidelines in the book, "Java Coding Guidelines: 75 Recommendations for Reliable and Secure Programs", and states their applicability to the development of Android applications. Applicable means that the guideline can be applied to general Java platforms including Android. Applicable in principle means that the guideline can be applied to Android but the examples shown in the guideline are not relevant to Android, and in some cases the guideline's full description also needs edits (the latter are provided in the Comments column). Not applicable means that the guideline cannot be applied to Android platforms.
Contents
| Table of Contents |
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Rules
Rule | Comments |
| IDS00-J. Sanitize untrusted data passed across a trust boundary | The rule uses MS SQL Server as an example to show a database connection. However, on Android, DatabaseHelper from SQLite is used for a database connection. Because Android apps may receive untrusted data via network connections, the rule is applicable. |
| IDS01-J. Normalize strings before validating them | Android apps can receive string data from the outside and normalize it. |
| IDS02-J. Canonicalize path names before validating them | The rule is applicable in principle. Please refer to the Android specific instance of this rule: DRD08-J. Always canonicalize a URL received by a content provider. |
| IDS04-J. Safely extract files from ZipInputStream | Although not directly a violation of this rule, the Android Master Key vulnerability (insecure use of ZipEntry) is related to this rule. Another attack vector found by a Chinese researcher is also related to this rule. |
| IDS07-J. Do not pass untrusted, unsanitized data to the Runtime.exec() method | Runtime.exec() can be called from Android apps to execute operating system commands. |
| IDS09-J. Do not use locale-dependent methods on locale-dependent data without specifying the appropriate locale | A developer can specify locale on Android using java.util.Locale. |
| EXP01-J. Never dereference null pointers | Android applications are more sensitive to NullPointerException due to the constraint of the limited mobile device memory. Static members or members of an Activity may become null when memory runs out. |
| EXP06-J. Do not use side-effecting expressions in assertions | The assert statement is supported on the Dalvik VM but is ignored under the default configuration. Assertions may be enabled by setting the system property "debug.assert" via: adb shell setprop debug.assert 1 or by sending the command line argument "--enable-assert" to the Dalvik VM. |
| NUM00-J. Detect or prevent integer overflow | Mezzofanti for Android contained an integer overflow which prevented the use of a big SD card. Mezzofanti contained an expression:
to calculate the available memory in a SD card, which could result in a negative value when the available memory is bigger than Note these methods are deprecated in API level 18 and replaced by |
| NUM04-J. Do not use floating-point numbers if precise computation is required | The use of floating-point is not recommended for performance reasons on Android. |
| NUM06-J. Use the strictfp modifier for floating-point calculation consistency across platforms | |
| NUM11-J. Do not compare or inspect the string representation of floating-point values | Comparing or inspecting the string representation of floating-point values may have unexpected results on Android. |
| MET01-J. Never use assertions to validate method arguments | The assert statement is supported on the Dalvik VM but is ignored under the default configuration. Assertions may be enabled by setting the system property "debug.assert" via: adb shell setprop debug.assert 1 or by sending the command line argument "--enable-assert" to the Dalvik VM. |
| MET02-J. Do not use deprecated or obsolete classes or methods | The Android SDK also has deprecated or obsolete APIs. Also, there may exist incompatible APIs depending on the SDK version. Therefore, it is recommended that developers refer to the "Android API Difference report" and consider replacing the deprecated APIs. |
| MET03-J. Methods that perform a security check must be declared private or final | On Android, System.getSecurityManager() is not used and the use of a Security Manager is not exercised. However, an Android developer can implement security-sensitive methods so the principle may be applicable on Android. |
| ERR09-J. Do not allow untrusted code to terminate the JVM | On Android, System.exit() should not be used because it will terminate the virtual machine abruptly, ignoring the activity lifecycle which may prevent proper garbage collection. |
| LCK00-J. Use private final lock objects to synchronize classes that may interact with untrusted code | |
| LCK05-J. Synchronize access to static fields that can be modified by untrusted code | |
| LCK11-J. Avoid client-side locking when using classes that do not commit to their locking strategy | |
| THI00-J. Do not invoke Thread.run() | Android provides a couple of solutions for threading. The Android Developers Blog's article "Painless threading" discusses those solutions. |
| THI02-J. Notify all waiting threads rather than a single thread | |
| THI03-J. Always invoke wait() and await() methods inside a loop | |
| THI04-J. Ensure that threads performing blocking operations can be terminated | |
| THI05-J. Do not use Thread.stop() to terminate threads | On Android, Thread.stop() was deprecated in API level 1. |
| TPS00-J. Use thread pools to enable graceful degradation of service during traffic bursts | |
| TPS01-J. Do not execute interdependent tasks in a bounded thread pool | |
| TPS02-J. Ensure that tasks submitted to a thread pool are interruptible | |
| TPS03-J. Ensure that tasks executing in a thread pool do not fail silently | |
| TPS04-J. Ensure ThreadLocal variables are reinitialized when using thread pools | |
| TSM00-J. Do not override thread-safe methods with methods that are not thread-safe | |
| TSM01-J. Do not let the this reference escape during object construction | |
| TSM02-J. Do not use background threads during class initialization | |
| FIO00-J. Do not operate on files in shared directories | On Android, the SD card ( / sdcard or /mnt/ sdcard ) is shared among multiple applications, thus sensitive files should not be stored on the SD card. |
| FIO01-J. Create files with appropriate access permissions | Creating files with weak permissions may allow malicious applications to access the files. |
| FIO04-J. Release resources when they are no longer needed | The compliant solution (Java SE 7: try-with-resources) is not yet supported at API level 18 (Android 4.3). |
| FIO06-J. Do not create multiple buffered wrappers on a single InputStream | |
| FIO13-J. Do not log sensitive information outside a trust boundary | DRD04-J. Do not log sensitive information is an Android specific instance of this rule. |
| FIO14-J. Perform proper cleanup at program termination | Although most of the code examples are not applicable to the Android platform, the principle is applicable to Android. There are a number of ways to terminate a process on Android: android.app.Activity.finish(), and the related finish... methods, android.app.Activity.moveTaskToBack(boolean flag), android.os.Process.killProcess(int pid), System.exit(). |
| FIO15-J. Do not operate on untrusted file links | |
| SEC01-J. Do not allow tainted variables in privileged blocks | The code examples using the java.security package are not applicable to Android but the principle of the rule is applicable to Android apps. |
| SEC02-J. Do not base security checks on untrusted sources | The code examples using the java.security package are not applicable to Android but the principle of the rule is applicable to Android apps. |
| SEC03-J. Do not load trusted classes after allowing untrusted code to load arbitrary classes | On Android, the use of DexClassLoader or PathClassLoader requires caution. |
| SEC05-J. Do not use reflection to increase accessibility of classes, methods, or fields | Reflection can be used on Android so the rule is applicable. Also the use of reflection may allow a developer to access private Android APIs and so requires caution. |
| JNI 03-J. Do not use direct pointers to Java objects in JNI code | Applicable to API versions 14 and above, with NDK versions 7 and above. |
| ENV02-J. Do not trust the values of environment variables | On Android, the environment variable user.name is not used and is left blank. However, environment variables exist and are used on Android so the rule is applicable. |
| ENV04-J. Do not disable bytecode verification | Under the default settings, bytecode verification is enabled on the Dalvik VM. To change the settings use the adb shell to set the appropriate system property, for example: adb shell setprop dalvik.vm.dexopt-flags v=a or pass -Xverify:all as an argument to the Dalvik VM. |
| MSC03-J. Never hard code sensitive information | Hard coded information can be easily obtained on Android by using the apktool to decompile an application or by using dex2jar to convert a dex file to a jar file. |
...
| Guideline | Android app development applicable? | Original Comments | TC Comments | |
|---|---|---|---|---|
| OBJ03-J. Do not mix generic with nongeneric raw types in new code | [Applicable] | Could not find a page with this title. Should it go to this page, which has the same number? OBJ03-J. Prevent heap pollution | ||
| FIO08-J. Use an int to capture the return value of methods that read a character or byte | [Applicable] | This page was deleted. We can ask for it to be undeleted. Please advise.>= | ||
| FIO11-J. Do not attempt to read raw binary data as character data | [Applicable] | The link on the left does not work. Please advise.> Do you want to link to this page? STR03-J. Do not convert between strings and bytes without specifying a valid character encoding | ||
| OBJ56-J. Provide sensitive mutable classes with unmodifiable wrappers | Unknown | ? | How should this be categorized? | |
| SEC57-J. Do not let untrusted code misuse privileges of callback methods | Unknown | How should this be categorized? | ||
| IDS00-J. Sanitize untrusted data passed across a trust boundary | The rule uses MS SQL Server as an example to show a database connection. However, on Android, DatabaseHelper from SQLite is used for a database connection. Because Android apps may receive untrusted data via network connections, the rule is applicable. | Which page should this entry link to? |
Bibliography
| [Long 2013] | Java Coding Guidelines: 75 Recommendations for Reliable and Secure Programs |
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