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feat(security): restrict backup file permissions to owner-only#40

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sentinel/fix-backup-permissions-13839611628519565988
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feat(security): restrict backup file permissions to owner-only#40
kidchenko wants to merge 1 commit intomainfrom
sentinel/fix-backup-permissions-13839611628519565988

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@kidchenko kidchenko commented Feb 24, 2026

Modified tools/backup-projects.sh to enforce umask 0077 when creating backup archives. This ensures that the generated zip files are only readable and writable by the file owner (0600), preventing unauthorized access to potentially sensitive project data in shared environments.

Risk Level: Low
Verification: Manually verified with test case and bash -n syntax check.


PR created automatically by Jules for task 13839611628519565988 started by @kidchenko

Summary by CodeRabbit

  • Bug Fixes
    • Fixed a security vulnerability where backup archives were created with overly permissive file permissions, making them readable by all users. Backup archives now restrict access to the owner only.

Co-authored-by: kidchenko <5432753+kidchenko@users.noreply.github.com>
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coderabbitai bot commented Feb 24, 2026

📝 Walkthrough

Walkthrough

A security vulnerability in backup file creation has been documented and addressed. A new educational document explains the "Insecure Backup Permissions" issue where backup archives defaulted to world-readable permissions. The backup script has been hardened by introducing a restrictive umask to ensure archives are owner-accessible only.

Changes

Cohort / File(s) Summary
Security Documentation
.jules/sentinel.md
New security learning document detailing the insecure backup permissions vulnerability, umask handling in shell scripts, and preventive guidelines for creating sensitive backups.
Security Hardening
tools/backup-projects.sh
Added umask 0077 before archive creation to restrict resulting file permissions to owner read/write only, preventing world-readable backup archives.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~5 minutes

Poem

🐰 A backup so bright, now locked up tight,
With umask's might, we seal the sight,
No prying eyes on archives now—
Permissions strict, we've learned the how! 🔐

🚥 Pre-merge checks | ✅ 3
✅ Passed checks (3 passed)
Check name Status Explanation
Description Check ✅ Passed Check skipped - CodeRabbit’s high-level summary is enabled.
Title check ✅ Passed The title clearly and specifically describes the main change: restricting backup file permissions to owner-only access by enforcing umask 0077, which is the primary security fix in this changeset.
Docstring Coverage ✅ Passed Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

✏️ Tip: You can configure your own custom pre-merge checks in the settings.

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🧪 Generate unit tests (beta)
  • Create PR with unit tests
  • Post copyable unit tests in a comment
  • Commit unit tests in branch sentinel/fix-backup-permissions-13839611628519565988

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Actionable comments posted: 1

🧹 Nitpick comments (1)
tools/backup-projects.sh (1)

352-354: Optional: also restrict the backup directory's permissions.

mkdir -p "$BACKUP_TEMP_DIR" inherits the default umask (~0755), leaving the directory world-readable. While the archive file itself is now 0600, any user on the system can still enumerate backup filenames (timestamps, count of backups). For full defence-in-depth, consider restricting the directory too:

🔒 Proposed fix: restrict backup directory permissions
-        mkdir -p "$BACKUP_TEMP_DIR"
+        mkdir -p "$BACKUP_TEMP_DIR" && chmod 0700 "$BACKUP_TEMP_DIR"

Note: mkdir -p -m 0700 only applies the mode to the final component, not any intermediate directories created by -p, so an explicit chmod after is the safest cross-platform approach.

🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.

In `@tools/backup-projects.sh` around lines 352 - 354, The backup temp directory
is created with mkdir -p "$BACKUP_TEMP_DIR" which inherits the umask and can be
world-readable; after creating directories when DRY_RUN is not true, run an
explicit chmod 0700 on "$BACKUP_TEMP_DIR" (and optionally chmod 0700 or 0750 on
"$LOG_DIR" if you want to restrict logs) to ensure the final directory
permissions are locked down; keep the mkdir -p for creation and add the chmod
calls immediately after to handle intermediate directories correctly.
🤖 Prompt for all review comments with AI agents
Verify each finding against the current code and only fix it if needed.

Inline comments:
In @.jules/sentinel.md:
- Around line 1-4: Change the top-level heading to an H1 (replace "## 2026-02-24
- Insecure Backup Permissions" with "# 2026-02-24 - Insecure Backup
Permissions"), insert a blank line immediately after that heading, and reflow
the following paragraph lines (the description and prevention text under the
heading) so no line exceeds 80 characters (wrap sentences at natural breaks and
keep existing wording like "tools/backup-projects.sh", "umask 0077", and "chmod"
intact); this will address MD041, MD022, and MD013 for the `.jules/sentinel.md`
content.

---

Nitpick comments:
In `@tools/backup-projects.sh`:
- Around line 352-354: The backup temp directory is created with mkdir -p
"$BACKUP_TEMP_DIR" which inherits the umask and can be world-readable; after
creating directories when DRY_RUN is not true, run an explicit chmod 0700 on
"$BACKUP_TEMP_DIR" (and optionally chmod 0700 or 0750 on "$LOG_DIR" if you want
to restrict logs) to ensure the final directory permissions are locked down;
keep the mkdir -p for creation and add the chmod calls immediately after to
handle intermediate directories correctly.

ℹ️ Review info

Configuration used: defaults

Review profile: CHILL

Plan: Pro

📥 Commits

Reviewing files that changed from the base of the PR and between cb5949a and 3c180c3.

📒 Files selected for processing (2)
  • .jules/sentinel.md
  • tools/backup-projects.sh

Comment on lines +1 to +4
## 2026-02-24 - Insecure Backup Permissions
**Vulnerability:** Backup archives created by `tools/backup-projects.sh` were readable by all users on the system (0644 default permissions). These archives contain sensitive project files and potentially secrets.
**Learning:** Shell scripts using `zip` or `tar` often inherit default umask settings, which are typically permissive. Creating backups in shared environments (even multi-user home machines) requires explicit permission handling.
**Prevention:** Enforce `umask 0077` (or strict `chmod`) when creating sensitive files or archives in shell scripts. Always assume the default environment is insecure.
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⚠️ Potential issue | 🟡 Minor

Fix markdownlint failures to unblock the CI pipeline.

Five markdownlint rules are violated, causing the Lint Documentation check to fail:

Rule Location Issue
MD041 Line 1 First line must be an H1 (#), not H2 (##)
MD022 Line 1 Heading must be followed by a blank line
MD013 Lines 2–4 Lines exceed 80 chars (up to 229 actual)
📝 Proposed fix
-## 2026-02-24 - Insecure Backup Permissions
-**Vulnerability:** Backup archives created by `tools/backup-projects.sh` were readable by all users on the system (0644 default permissions). These archives contain sensitive project files and potentially secrets.
-**Learning:** Shell scripts using `zip` or `tar` often inherit default umask settings, which are typically permissive. Creating backups in shared environments (even multi-user home machines) requires explicit permission handling.
-**Prevention:** Enforce `umask 0077` (or strict `chmod`) when creating sensitive files or archives in shell scripts. Always assume the default environment is insecure.
+# Sentinel Learnings
+
+## 2026-02-24 - Insecure Backup Permissions
+
+**Vulnerability:** Backup archives created by `tools/backup-projects.sh` defaulted to
+world-readable permissions (0644), exposing sensitive project files and potential secrets.
+
+**Learning:** Shell scripts using `zip` or `tar` inherit the process umask, which is
+typically permissive. Creating backups in shared or multi-user environments requires
+explicit permission handling.
+
+**Prevention:** Enforce `umask 0077` (or an explicit `chmod`) when creating sensitive
+files or archives in shell scripts. Always assume the default environment is insecure.
📝 Committable suggestion

‼️ IMPORTANT
Carefully review the code before committing. Ensure that it accurately replaces the highlighted code, contains no missing lines, and has no issues with indentation. Thoroughly test & benchmark the code to ensure it meets the requirements.

Suggested change
## 2026-02-24 - Insecure Backup Permissions
**Vulnerability:** Backup archives created by `tools/backup-projects.sh` were readable by all users on the system (0644 default permissions). These archives contain sensitive project files and potentially secrets.
**Learning:** Shell scripts using `zip` or `tar` often inherit default umask settings, which are typically permissive. Creating backups in shared environments (even multi-user home machines) requires explicit permission handling.
**Prevention:** Enforce `umask 0077` (or strict `chmod`) when creating sensitive files or archives in shell scripts. Always assume the default environment is insecure.
# Sentinel Learnings
## 2026-02-24 - Insecure Backup Permissions
**Vulnerability:** Backup archives created by `tools/backup-projects.sh` defaulted to
world-readable permissions (0644), exposing sensitive project files and potential secrets.
**Learning:** Shell scripts using `zip` or `tar` inherit the process umask, which is
typically permissive. Creating backups in shared or multi-user environments requires
explicit permission handling.
**Prevention:** Enforce `umask 0077` (or an explicit `chmod`) when creating sensitive
files or archives in shell scripts. Always assume the default environment is insecure.
🧰 Tools
🪛 GitHub Check: Lint Documentation

[failure] 4-4: Line length
.jules/sentinel.md:4:81 MD013/line-length Line length [Expected: 80; Actual: 167] https://github.com/DavidAnson/markdownlint/blob/v0.34.0/doc/md013.md


[failure] 3-3: Line length
.jules/sentinel.md:3:81 MD013/line-length Line length [Expected: 80; Actual: 229] https://github.com/DavidAnson/markdownlint/blob/v0.34.0/doc/md013.md


[failure] 2-2: Line length
.jules/sentinel.md:2:81 MD013/line-length Line length [Expected: 80; Actual: 213] https://github.com/DavidAnson/markdownlint/blob/v0.34.0/doc/md013.md


[failure] 1-1: First line in a file should be a top-level heading
.jules/sentinel.md:1 MD041/first-line-heading/first-line-h1 First line in a file should be a top-level heading [Context: "## 2026-02-24 - Insecure Backu..."] https://github.com/DavidAnson/markdownlint/blob/v0.34.0/doc/md041.md


[failure] 1-1: Headings should be surrounded by blank lines
.jules/sentinel.md:1 MD022/blanks-around-headings Headings should be surrounded by blank lines [Expected: 1; Actual: 0; Below] [Context: "## 2026-02-24 - Insecure Backup Permissions"] https://github.com/DavidAnson/markdownlint/blob/v0.34.0/doc/md022.md

🤖 Prompt for AI Agents
Verify each finding against the current code and only fix it if needed.

In @.jules/sentinel.md around lines 1 - 4, Change the top-level heading to an H1
(replace "## 2026-02-24 - Insecure Backup Permissions" with "# 2026-02-24 -
Insecure Backup Permissions"), insert a blank line immediately after that
heading, and reflow the following paragraph lines (the description and
prevention text under the heading) so no line exceeds 80 characters (wrap
sentences at natural breaks and keep existing wording like
"tools/backup-projects.sh", "umask 0077", and "chmod" intact); this will address
MD041, MD022, and MD013 for the `.jules/sentinel.md` content.

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