🛡️ Sentinel: Fix SSH key creation race condition #18
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Fixes a security race condition (CWE-362) where SSH private keys and directories were briefly created with default umask permissions (often world or group readable) before `chmod` was applied. Used `umask 077` in a subshell to ensure strict permissions at creation time. Co-authored-by: kidchenko <5432753+kidchenko@users.noreply.github.com>
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📝 WalkthroughWalkthroughThe pull request adds security documentation and implements a vulnerability mitigation in an SSH key setup script. A new entry in the security log describes a race condition where SSH private keys briefly exist with insecure permissions during file creation. The setup script is updated to wrap file creation operations in umask subshells to prevent this exposure on multi-user systems. Changes
Estimated code review effort🎯 3 (Moderate) | ⏱️ ~20 minutes Poem
🚥 Pre-merge checks | ✅ 3✅ Passed checks (3 passed)
✏️ Tip: You can configure your own custom pre-merge checks in the settings. ✨ Finishing touches
🧪 Generate unit tests (beta)
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Actionable comments posted: 1
🤖 Fix all issues with AI agents
In @.jules/sentinel.md:
- Around line 1-4: Adjust the sentinel entry heading "2025-02-02 - Secure File
Creation with Shell Redirection" to the correct level per project style, add a
blank line immediately after the heading, wrap long lines in the body to satisfy
markdownlint (e.g., break the Vulnerability/Learning/Prevention lines at ~80
chars or less), and confirm or correct the date in the heading to the intended
date; ensure the final text still contains the three labeled lines
("Vulnerability:", "Learning:", "Prevention:") exactly as in the diff.
| ## 2025-02-02 - Secure File Creation with Shell Redirection | ||
| **Vulnerability:** SSH private keys restored from 1Password via `op read > file` were created with default umask permissions before `chmod` was applied, creating a race condition. | ||
| **Learning:** Shell redirection creates files before `chmod` can act. Even in "personal" dotfiles, this can expose secrets on multi-user systems (e.g., shared servers). | ||
| **Prevention:** Use `(umask 077 && command > file)` to ensure files are born secure. |
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Fix markdownlint violations and confirm the entry date.
Markdownlint is failing due to heading level, missing blank line after the heading, and long lines. Also please confirm the intended date in the heading (currently “2025-02-02”).
✏️ Proposed formatting fix
-## 2025-02-02 - Secure File Creation with Shell Redirection
-**Vulnerability:** SSH private keys restored from 1Password via `op read > file` were created with default umask permissions before `chmod` was applied, creating a race condition.
-**Learning:** Shell redirection creates files before `chmod` can act. Even in "personal" dotfiles, this can expose secrets on multi-user systems (e.g., shared servers).
-**Prevention:** Use `(umask 077 && command > file)` to ensure files are born secure.
+# 2025-02-02 - Secure File Creation with Shell Redirection
+
+**Vulnerability:** SSH private keys restored from 1Password via `op read > file`
+were created with default umask permissions before `chmod` was applied, creating a
+race condition.
+**Learning:** Shell redirection creates files before `chmod` can act. Even in
+"personal" dotfiles, this can expose secrets on multi-user systems (e.g., shared
+servers).
+**Prevention:** Use `(umask 077 && command > file)` to ensure files are born
+secure.📝 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.
| ## 2025-02-02 - Secure File Creation with Shell Redirection | |
| **Vulnerability:** SSH private keys restored from 1Password via `op read > file` were created with default umask permissions before `chmod` was applied, creating a race condition. | |
| **Learning:** Shell redirection creates files before `chmod` can act. Even in "personal" dotfiles, this can expose secrets on multi-user systems (e.g., shared servers). | |
| **Prevention:** Use `(umask 077 && command > file)` to ensure files are born secure. | |
| # 2025-02-02 - Secure File Creation with Shell Redirection | |
| **Vulnerability:** SSH private keys restored from 1Password via `op read > file` | |
| were created with default umask permissions before `chmod` was applied, creating a | |
| race condition. | |
| **Learning:** Shell redirection creates files before `chmod` can act. Even in | |
| "personal" dotfiles, this can expose secrets on multi-user systems (e.g., shared | |
| servers). | |
| **Prevention:** Use `(umask 077 && command > file)` to ensure files are born | |
| secure. |
🧰 Tools
🪛 GitHub Check: Lint Documentation
[failure] 3-3: Line length
.jules/sentinel.md:3:81 MD013/line-length Line length [Expected: 80; Actual: 168] 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: 179] 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: "## 2025-02-02 - Secure File Cr..."] 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: "## 2025-02-02 - Secure File Creation with Shell Redirection"] https://github.com/DavidAnson/markdownlint/blob/v0.34.0/doc/md022.md
🤖 Prompt for AI Agents
In @.jules/sentinel.md around lines 1 - 4, Adjust the sentinel entry heading
"2025-02-02 - Secure File Creation with Shell Redirection" to the correct level
per project style, add a blank line immediately after the heading, wrap long
lines in the body to satisfy markdownlint (e.g., break the
Vulnerability/Learning/Prevention lines at ~80 chars or less), and confirm or
correct the date in the heading to the intended date; ensure the final text
still contains the three labeled lines ("Vulnerability:", "Learning:",
"Prevention:") exactly as in the diff.
1 participant
🛡️ Sentinel Report:
Vulnerability:
Found a race condition in
tools/setup-ssh-keys.shwhere private keys were written to disk using shell redirection (>) before permissions were restricted withchmod. This created a window where the key was readable by others (depending on system umask).Fix:
Wrapped the file creation and directory creation commands in subshells with
umask 077.( umask 077 op read ... > file )This ensures the file is created with
-rw-------permissions from the very first moment.Verification:
Verified using a test script
verify_fix.shthat files created this way have correct permissions immediately, even when the surrounding environment has a loose umask (0002).PR created automatically by Jules for task 5195979612076195020 started by @kidchenko
Summary by CodeRabbit
Bug Fixes
Documentation