GHSA-hh9p-6wh2-4mfc: Infoleak

Summary

IndexFile.remove() and Head.checkout() forward kwargs into git rm and git checkout with no guard. Passing --pathspec-from-file=<file> together with --pathspec-file-nul makes Git treat the whole file as a single NUL-delimited pathspec, and the unmatched-pathspec error quotes it verbatim. GitPython surfaces that through GitCommandError.stderr, so the entire contents of a caller-chosen file are returned to the caller in band.

This is the same primitive as Instance 2 of GHSA-3f7w-8rr8-f37f - TagReference.create() with -F, arbitrary file read returned in band - at two sites that advisory assessed and cleared.

Prior art, and why I am filing rather than commenting

GHSA-3f7w-8rr8-f37f's sweep table lists these four sites with the assessment "--pathspec-from-file only reads a pathspec; no write or disclosure primitive found":

| Call site | git command | that advisory's assessment | |---|---|---| | IndexFile.remove() | rm | --pathspec-from-file only reads a pathspec; no write or disclosure primitive found | | IndexFile.move() | mv | same | | HEAD.reset() | reset | same | | HEAD.checkout() | checkout | same |

That assessment is very nearly right, and I think that is why it held: with --pathspec-from-file alone, Git splits on newlines and the error quotes only the first line, which reads as an uninteresting partial. Adding --pathspec-file-nul - a sibling flag of the same option, and the documented way to handle paths containing newlines - makes the whole file one pathspec.

Root cause

git/index/base.py:991-1043:

python def remove(self, items, workingtree=False, kwargs): ... removedpaths = self.repo.git.rm(args, paths, kwargs).splitlines() # line 1043

git/refs/head.py:237-268:

python def checkout(self, force: bool = False, kwargs: Any): ... self.repo.git.checkout(self, kwargs) # line 268

Neither has an allowunsafeoptions parameter or a checkunsafeoptions() call.

Proof of concept

python from git import Repo from git.exc import GitCommandError

repo = Repo("/path/to/repo") kw = dict(pathspecfromfile="/etc/passwd", pathspecfilenul=True)

try: repo.index.remove([], kw) # or: repo.heads[0].checkout(kw) except GitCommandError as e: print(e.stderr) # <- entire file contents

Observed on published 3.1.57, against a canary file holding three marked lines:

[PASS] IndexFile.remove() -> git rm returns ALL 3 canary lines in-band stderr: 'fatal: pathspec 'LINE1-CANARY-4242 LINE2-SECRET-7777 LINE3-TAIL-9999 ' did not match any files' [PASS] Head.checkout() -> git checkout returns ALL 3 canary lines in-band stderr: 'error: pathspec 'LINE1-CANARY-4242 LINE2-SECRET-7777 LINE3-TAIL-9999 ' did not match any file(s) known to git' [PASS] PRECISION: git status leaks 0/3 -- not every unguarded site discloses [PASS] PRECISION: the GUARDED checkout-index leaks 0/3

The two precision controls are there so the result is about these sinks and not about the canary being visible everywhere.

Scope correction to the table above

Of the four sites cleared with that sentence, two disclose and two do not:

| Call site | disclosed? | |---|---| | IndexFile.remove() → git rm | yes, full file | | Head.checkout() → git checkout | yes, full file | | HEAD.reset() → git reset | no - git reset does not error on unmatched pathspecs | | IndexFile.move() → git mv | no |

The two negatives are mentioned because "the dismissal was wrong" would overstate it: the dismissal was wrong for half of what it covered.