From 1051db0f0181a71d6e08fdbf533aaf55e2010eb3 Mon Sep 17 00:00:00 2001
From: "google-labs-jules[bot]"
 <161369871+google-labs-jules[bot]@users.noreply.github.com>
Date: Sun, 8 Feb 2026 05:04:10 +0000
Subject: [PATCH] fix(security): prevent TOCTOU race condition in SSH key
 creation

- Use `umask 077` in a subshell when writing SSH private keys to disk.
- Ensure SSH directory has 700 permissions on creation and if it already exists.
- Add security journal entry in `.jules/sentinel.md`.

This prevents a brief window where the private key file could be world-readable before `chmod 600` is applied.

Co-authored-by: kidchenko <5432753+kidchenko@users.noreply.github.com>
---
 .jules/sentinel.md      |  4 ++++
 tools/setup-ssh-keys.sh | 13 +++++++++----
 2 files changed, 13 insertions(+), 4 deletions(-)
 create mode 100644 .jules/sentinel.md

diff --git a/.jules/sentinel.md b/.jules/sentinel.md
new file mode 100644
index 0000000..90186a1
--- /dev/null
+++ b/.jules/sentinel.md
@@ -0,0 +1,4 @@
+## 2025-02-08 - TOCTOU Race Condition in File Creation
+**Vulnerability:** The SSH private key was being created with default permissions (potentially world-readable) before `chmod 600` was applied. This created a race condition where the key could be read by other users on the system.
+**Learning:** Shell redirection (`>`) creates files with the current `umask` before any subsequent `chmod` command is executed.
+**Prevention:** Use `umask 077` in a subshell when creating sensitive files to ensure they are created with restricted permissions from the start. Example: `(umask 077; command > file)`.
diff --git a/tools/setup-ssh-keys.sh b/tools/setup-ssh-keys.sh
index bde52fd..4ecc6d9 100755
--- a/tools/setup-ssh-keys.sh
+++ b/tools/setup-ssh-keys.sh
@@ -148,12 +148,17 @@ cmd_restore() {
 
     say "Restoring SSH key from 1Password..."
 
-    # Create SSH directory
-    mkdir -p "$SSH_DIR"
+    # Create SSH directory with secure permissions
+    if [[ ! -d "$SSH_DIR" ]]; then
+        mkdir -p -m 700 "$SSH_DIR"
+    fi
     chmod 700 "$SSH_DIR"
 
-    # Read private key from 1Password and save locally
-    op read "op://$VAULT/$KEY_NAME/private_key" > "$PRIVATE_KEY_FILE"
+    # Read private key from 1Password and save locally with secure permissions
+    (
+        umask 077
+        op read "op://$VAULT/$KEY_NAME/private_key" > "$PRIVATE_KEY_FILE"
+    )
     chmod 600 "$PRIVATE_KEY_FILE"
 
     # Read public key from 1Password and save locally