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fusesource / jansi

Jansi is a small java library that allows you to use ANSI escape sequences to format your console output which works even on windows.
http://fusesource.github.io/jansi/
Apache License 2.0
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Fix invalid string input #253

Closed arthurscchan closed 10 months ago

arthurscchan commented 11 months ago

This fixes a possible unwrapped StringIndexOutOfBoundException in src/main/java/org/fusesource/jansi/AnsiRenderer.java.

In line 85, line 95 and line 101 of the AnsiRenderer class. The method tries to determine the necessary index j and k for doing a substring operation on the input string. If the input string is malformed, it could cause j larger than k and result in StringIndexOutOfBoundException. For example, if the EndToken appears before the BeginToken, or there is no EndToken in the input string, then j is larger than k for sure.

This PR fixes the bug by adding a conditional check before doing the substring to ensure k is larger or equals to j. Otherwise, the input string is considered as malformed and an IllegalArgumentException is thrown.

We found this bug using fuzzing by way of OSS-Fuzz, where we recently integrated jansi (https://github.com/google/oss-fuzz/pull/10705). OSS-Fuzz is a free service run by Google for fuzzing important open source software. If you'd like to know more about this then I'm happy to go in details and also set up things so you can receive emails and detailed reports when bugs are found.

gnodet commented 11 months ago

@arthurscchan do you think you can add a simple unit test for this issue ?

arthurscchan commented 11 months ago

@gnodet Thanks for your reply. Yes I could add a unit test. Will do so soon.