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There is a known social engineering attack that takes advantage of the fact that a working tree can include an entire bare repository, including a config file. A user could run a Git command inside the bare repository thinking that the config file of the 'outer' repository would be used, but in reality, the bare repository's config file (which is attacker-controlled) is used, which may result in arbitrary code execution. See [1] for a fuller description and deeper discussion. A simple mitigation is to forbid bare repositories unless specified via `--git-dir` or `GIT_DIR`. In environments that don't use bare repositories, this would be minimally disruptive. Create a config variable, `safe.bareRepository`, that tells Git whether or not to die() when working with a bare repository. This config is an enum of: - "all": allow all bare repositories (this is the default) - "explicit": only allow bare repositories specified via --git-dir or GIT_DIR. If we want to protect users from such attacks by default, neither value will suffice - "all" provides no protection, but "explicit" is impractical for bare repository users. A more usable default would be to allow only non-embedded bare repositories ([2] contains one such proposal), but detecting if a repository is embedded is potentially non-trivial, so this work is not implemented in this series. [1]: https://lore.kernel.org/git/kl6lsfqpygsj.fsf@chooglen-macbookpro.roam.corp.google.com [2]: https://lore.kernel.org/git/5b969c5e-e802-c447-ad25-6acc0b784582@github.com Signed-off-by: Glen Choo <chooglen@google.com> Signed-off-by: Junio C Hamano <gitster@pobox.com>
55 lines
1.3 KiB
Bash
Executable file
55 lines
1.3 KiB
Bash
Executable file
#!/bin/sh
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test_description='verify safe.bareRepository checks'
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TEST_PASSES_SANITIZE_LEAK=true
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. ./test-lib.sh
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pwd="$(pwd)"
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expect_accepted () {
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git "$@" rev-parse --git-dir
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}
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expect_rejected () {
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test_must_fail git "$@" rev-parse --git-dir 2>err &&
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grep -F "cannot use bare repository" err
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}
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test_expect_success 'setup bare repo in worktree' '
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git init outer-repo &&
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git init --bare outer-repo/bare-repo
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'
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test_expect_success 'safe.bareRepository unset' '
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expect_accepted -C outer-repo/bare-repo
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'
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test_expect_success 'safe.bareRepository=all' '
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test_config_global safe.bareRepository all &&
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expect_accepted -C outer-repo/bare-repo
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'
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test_expect_success 'safe.bareRepository=explicit' '
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test_config_global safe.bareRepository explicit &&
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expect_rejected -C outer-repo/bare-repo
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'
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test_expect_success 'safe.bareRepository in the repository' '
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# safe.bareRepository must not be "explicit", otherwise
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# git config fails with "fatal: not in a git directory" (like
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# safe.directory)
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test_config -C outer-repo/bare-repo safe.bareRepository \
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all &&
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test_config_global safe.bareRepository explicit &&
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expect_rejected -C outer-repo/bare-repo
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'
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test_expect_success 'safe.bareRepository on the command line' '
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test_config_global safe.bareRepository explicit &&
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expect_accepted -C outer-repo/bare-repo \
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-c safe.bareRepository=all
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'
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test_done
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