[adilalperenciftci]

Summary

I reproduced an allowed execve dropping cross-process containment whenever the caller supplied its own envp. Omitting the sandbox entries, or replacing them with empty/stale values, started the child without the preload layer and grant source.

This change:

• rebuilds explicit child environments on the stack while a preload sandbox is active;
• preserves application-provided non-control entries;
• removes caller-provided sandbox control values and appends the current process's LD_PRELOAD, AETHER_SANDBOX_*, and AETHER_CAPSICUM entries;
• refuses the exec with EPERM if an active sandbox has no non-empty preload or grant source to carry forward;
• caps environment scanning at 4096 entries and returns E2BIG beyond that bound.

Verification

• BEFORE: both omitted-control and overridden-control explicit environments read a file outside the child grants and exited zero.
• AFTER: both cases remain contained and the read is denied.
• Allowed exec with an inherited read grant: passed.
• Explicit ONLY=explicit plus current LD_PRELOAD and grant source all reached the child.
• Sandbox fork-grant, clone-fence, preload-lookup, and child signal-safety integrations: passed.
• make check-tests: passed.
• make test: 634 passed, 0 failed on Ubuntu VM.
• make check-changelog: passed.

The optional i386 clone probe skipped because Zig is not installed in the VM.

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[paul-hammant]

Thanks, reviewed and folded into the batch #3456 with your authorship kept on the commit. One change on top: the controls are snapshotted at startup rather than copied from live environ, which the contained process can edit (f92a672, with a test of that case). This PR will be closed when #3456 merges.

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[paul-hammant]

Merged as part of #3456 (merge 9364d6b), with your authorship on the commit. Thank you, @adilalperenciftci: this was a real fix, carefully tested, and it's appreciated.

🤖 Generated with Claude Code