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Call to logging API

Call to logging API


This entry describes all the logging API calls used to write log entries. In Android, a logging mechanism called Logcat is introduced to view and filter series of circular buffers that contain logs from various applications and portions of the system. Log information in Logcat can be read out from other applications in the same device. Thus, the output of sensitive information to Logcat is considered that it has a vulnerability of the information leakage.


To output log messages to LogCat in a safe manner, pursue the following recommendations:

  • Sensitive information must not be included in operation log information. Construct the build system to Auto-delete codes which output development log information: For example, Log.d() and Log.v() should be deleted when building an application for release. ProGuard is a tool that can automatically delete them by specifying Log.d() and Log(v) as parameter of -assumenosideeffects option.
  • Use Log.d() or Log.v() when Outputting throwable Objects: When exceptions occur, stack trace is often output to LogCat by Log.e(), Log.w() or Log.i() methods. Thus, detail internal structure can be shown. For example, when SQLiteException is output as it is, type of SQL statement is revealed and it may give a clue for SQL injection attack.
  • Use only Methods of the android.util.Log class for Log Output.
  • Do not output log information using print() or println() method of System.out and System.err class since log information and development log information are output by the same method and it fosters the danger of dropped deletion by oversight. Moreover, using both android.util.Log and System.out/err will increase considered needs and, as a result the danger of occurring mistakes will increase.
  • Choose the right log level based on the information criticity. ( ERROR, WARN, INFO, DEBUG, VERBOSE )