More lenient AXML parsing: allow for non-standard attributes sizes and avoid index exceptions when decoding some strings#2210
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skylot merged 2 commits intoskylot:masterfrom Jul 3, 2024
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… must be at least 20 (0x14) bytes but can be greater. Extra bytes are just skipped. When decoding a string, if such decoding is impossible a placeholder string is returned instead of throwing an exception. This is necessary because some malware purposely add android:tag attributes with invalid string index to throw parsers off. They also employ non-standard attribute sizes.
skylot
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Jul 3, 2024
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@qfalconer nice fix! Thank you 👍 |
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Almost all malicious APKs are now shipped with corrupted manifest. The corruption seep in where the official Android parse is more lenient, particularly the manifest present in these malware has one or more of the following:
In this patch the attributes size of an XML element is now accounted for.
This size must be at least 20 (0x14) bytes but can be greater. Extra bytes are just skipped.
When decoding a string, if such decoding is impossible a placeholder string is returned instead of throwing an exception. Not all code paths has been inspected, though (just what was necessary to make jadx parse the corrupted manifests at hand).
The attached test-corrupted-manifest.zip is an empty APK (or ZIP, same thing) with just a corrupted manifest from a real BRATA malware campaign. This can be useful to test this PR.