🛡️ Sentinel: [HIGH] Fix environment hijacking and arbitrary file move/deletion in install.sh

[google-labs-jules]

🚨 Severity: HIGH

💡 Vulnerability:

Critical variables used within the installer's exit/cleanup trap (ANTIGRAVITY_BAK, ANTIGRAVITY_VA39_BAK, INSTALL_BIN_DIR, SECURE_TMP_DIR) were not explicitly initialized at script startup. An attacker or user could pre-set these variables in their environment. If the script exited prematurely (e.g., during env/prerequisite checks or SIGINT/cancellation), the cleanup trap was invoked using those parent environment values, causing arbitrary files to be moved or deleted (rm -f or mv -f).

🔧 Fix:

• Explicitly initialize ANTIGRAVITY_BAK, ANTIGRAVITY_VA39_BAK, INSTALL_BIN_DIR, SECURE_TMP_DIR, and INSTALL_SUCCESS to safe defaults ("" and 0) at script entry.
• Prevent parent environment hijacking.
• Added strict non-empty checks for INSTALL_BIN_DIR before attempting restore mv commands in the trap logic.

✅ Verification:

• Verified that pre-setting ANTIGRAVITY_BAK=dummy_sensitive_file no longer deletes or moves the file during early script exits.
• Ran script syntax checks (bash -n install.sh) and existing test suites (python3 test_statusline.py) successfully with zero regressions.

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PR created automatically by Jules for task 9289392815037441823 started by @qapdex-maker

[google-labs-jules]

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