fix: Address layer / image extraction issues in user namespaces (4.1) #2701
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If we are running from within a user namespace, then use rootless OCI layer with umoci. This permits the extraction to complete when singularity is run under `unshare -r`. Part of sylabs#2698
If singularity is executed with `--userns/-u` then where possible it should also use a user namespace where it executes `unsquashfs` in a wrapped manner. Previously the `unsquashfs` wrapping was without `--userns/-u` in a setuid installation. This caused extraction to fail from within a non-root-mapped user namespace (e.g. `unshare -c`). Part of sylabs#2698
wobito
approved these changes
Mar 4, 2024
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Description of the Pull Request (PR):
Pick #2699
Note - there are no e2e tests for the nested containers / nested namespaces situations that are fixed by the commits in this PR. However, our e2e tests do confirm the changes don't cause regressions in non-nested cases.
The e2e framework doesn't offer a great way of executing singularity nested, and I've opened an issue (#2700) to address this to verify functionality more generally than a messy one-off for this PR would handle.
fix: use rootless umoci inside user namespace
If we are running from within a user namespace, then use rootless OCI layer extrraction with umoci.
This permits the extraction to complete when singularity is run under
unshare -r.fix: honor --userns in unsquashfs wrapping
If singularity is executed with
--userns/-uthen it should also use a user namespace where it executesunsquashfsin a wrapped manner.Previously the
unsquashfswrapping was without--userns/-uin a setuid installation. This caused extraction to fail from within a non-root-mapped user namespace (e.g.unshare -c).This fixes or addresses the following GitHub issues:
Before submitting a PR, make sure you have done the following:
make checkand tested this PR locally with amake test, andmake testallif possible (see CONTRIBUTING.md).