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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Incorrect parsing of TarInfo header when GNU long name  and type AREGTYPE are combined","articleBody":"# Bug report\n\n### Bug description:\n\nWhen an entry uses GNU long name encoding the `tarfile` module reads in the data blocks for the name and then [calls self.fromtarfile() again](https://github.com/python/cpython/blob/4867f717e21c3b5f0ad0e81f950c69dac6c95e6e/Lib/tarfile.py#L1404) to get the 'actual' header. This second header is the source of truth for everything _except_ the name which is just garbage data.\n\nThe problem is that `fromtarfile()` eventually calls `frombuf()` where [this logic](https://github.com/python/cpython/blob/4867f717e21c3b5f0ad0e81f950c69dac6c95e6e/Lib/tarfile.py#L1310-L1311) incorrectly uses the garbage data and overrides the entry type to directory, corrupting the entry.\n\nBecause the entry is detected as a directory, the offset is not updated properly and the next call to read a TarInfo entry will usually result in an exception. However, the exception lands up in [this block](https://github.com/python/cpython/blob/4867f717e21c3b5f0ad0e81f950c69dac6c95e6e/Lib/tarfile.py#L2851-L2857) where neither of the `if` conditions are met, so the exception is silently discarded. `tarinfo` remains `None` and the code [eventually decides](https://github.com/python/cpython/blob/4867f717e21c3b5f0ad0e81f950c69dac6c95e6e/Lib/tarfile.py#L2881-L2882) that there are no more entries in the tar file.\n\nI initially ran into this issue due to reports of invalid sdists being generated by maturin.\nSee: https://github.com/PyO3/maturin/issues/2855\n\n### CPython versions tested on:\n\n3.9, 3.10, 3.11, 3.12, 3.13, 3.14\n\n### Operating systems tested on:\n\nmacOS, Linux\n\n\u003c!-- gh-linked-prs --\u003e\n### Linked PRs\n* gh-143157\n* gh-143934\n\u003c!-- /gh-linked-prs --\u003e\n","author":{"url":"https://github.com/e-nomem","@type":"Person","name":"e-nomem"},"datePublished":"2025-11-18T10:34:31.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/141707/cpython/issues/141707"}