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🛡️ Sentinel: [CRITICAL] Fix TOCTOU vulnerability in SSH key creation #90

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Merged
kidchenko merged 2 commits into from
Apr 17, 2026
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🛡️ Sentinel: [CRITICAL] Fix TOCTOU vulnerability in SSH key creation #90

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🛡️ Sentinel: [CRITICAL] Fix TOCTOU vulnerability in SSH key creation
google-labs-jules[bot] Apr 15, 2026
77dc448
Merge branch 'main' into sentinel-fix-toctou-ssh-key-creation-1111852…
kidchenko Apr 17, 2026
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15 changes: 15 additions & 0 deletions .jules/sentinel.md
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Original file line number Diff line number Diff line change
@@ -1,4 +1,19 @@
# Sentinel Journal

## 2026-04-15 - Prevent TOCTOU in SSH Key Restoration

**Vulnerability:** A Time-of-Check to Time-of-Use (TOCTOU) vulnerability where an
SSH private key is briefly world-readable upon creation before `chmod 600` is
applied.

**Learning:** Redirecting output to a file creates the file with default
permissions (often `644`), which exposes sensitive data for a fraction of a
second.

**Prevention:** Wrap commands that create sensitive files in a subshell using
`umask 077` to ensure the file is created with secure permissions (`600`)
natively.
# Sentinel Security Journal

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.jules/sentinel.md:16 MD025/single-title/single-h1 Multiple top-level headings in the same document [Context: "# Sentinel Security Journal"] https://github.com/DavidAnson/markdownlint/blob/v0.34.0/doc/md025.md

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## 2026-04-16 - Prevent TOCTOU and Symlink Attacks via Insecure Temporary Directories

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2 changes: 1 addition & 1 deletion tools/setup-ssh-keys.sh
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Expand Up @@ -153,7 +153,7 @@ cmd_restore() {
chmod 700 "$SSH_DIR"

# Read private key from 1Password and save locally
op read "op://$VAULT/$KEY_NAME/private_key" > "$PRIVATE_KEY_FILE"
(umask 077 && op read "op://$VAULT/$KEY_NAME/private_key" > "$PRIVATE_KEY_FILE")
chmod 600 "$PRIVATE_KEY_FILE"

# Read public key from 1Password and save locally
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