apko affected by unbounded resource consumption in expandapk.Split on attacker-controlled .apk streams

expandapk.Split drains the first gzip stream of an APK archive via io.Copy(io.Discard, gzi) without explicit bounds. With an attacker-controlled input stream, this can force large gzip inflation work and lead to resource exhaustion (availability impact).

The Split function reads the first tar header, then drains the remainder of the gzip stream by reading from the gzip reader directly without any maximum uncompressed byte limit or inflate-ratio cap. A caller that parses attacker-controlled APK streams may be forced to spend excessive CPU time inflating gzip data, leading to timeouts or process slowdown.

Fix: Fixed with 2be3903, Released in v1.1.0.

Acknowledgements

apko thanks Oleh Konko from 1seal for discovering and reporting this issue.