fix: write the admin password file without following symlinks

In Docker, migrate runs as root while data/ belongs to www-data, so a
planted data/admin_password symlink would make root overwrite its target.
Remove any existing path first and create the file with
O_CREAT|O_EXCL|O_NOFOLLOW (mode set via fchmod). install.sh's /tmp
fallback log is now created with mktemp instead of a fixed name.

accounts/apps.py

@@ -40,10 +40,14 @@ def _store_generated_password(password):
     path = os.path.join(str(settings.BASE_DIR), "data", "admin_password")
     try:
         os.makedirs(os.path.dirname(path), exist_ok=True)
-        fd = os.open(path, os.O_WRONLY | os.O_CREAT | os.O_TRUNC, 0o600)
+        # Never write through a pre-existing file or symlink (this runs as
+        # root in Docker, while data/ belongs to www-data).
+        if os.path.lexists(path):
+            os.unlink(path)
+        fd = os.open(path, os.O_WRONLY | os.O_CREAT | os.O_EXCL | os.O_NOFOLLOW, 0o600)
+        os.fchmod(fd, 0o600)
         with os.fdopen(fd, "w") as f:
             f.write(password + "\n")
-        os.chmod(path, 0o600)
         print(f"\033[1m* \033[93mGenerated admin password written to {path}\033[0m")
     except OSError:
         print(f"\033[1m* \033[93mGenerated random admin password: {password}\033[0m")

accounts/test_admin_password.py

@@ -38,3 +38,17 @@ class GeneratedAdminPasswordTestCase(TestCase):
             self.assertNotIn(password, output)
             self.assertIn(str(password_file), output)
             self.assertIsNotNone(authenticate(username="admin", password=password))
+
+    def test_does_not_follow_a_planted_symlink(self):
+        with tempfile.TemporaryDirectory() as tmp:
+            (Path(tmp) / "data").mkdir()
+            victim = Path(tmp) / "victim"
+            victim.write_text("original\n")
+            (Path(tmp) / "data" / "admin_password").symlink_to(victim)
+
+            self._run_create_admin(tmp)
+
+            password_file = Path(tmp) / "data" / "admin_password"
+            self.assertEqual(victim.read_text(), "original\n")
+            self.assertFalse(password_file.is_symlink())
+            self.assertEqual(stat.S_IMODE(password_file.stat().st_mode), 0o600)

install.sh

@@ -83,8 +83,7 @@ chmod 744 "$INSTALLER"
 LOG_FILE="/var/log/webvirtcloud-install.log"
 mkdir -p "$(dirname "$LOG_FILE")" 2>/dev/null || true
 if ! touch "$LOG_FILE" 2>/dev/null; then
-    LOG_FILE="/tmp/webvirtcloud-install.log"
-    touch "$LOG_FILE"
+    LOG_FILE="$(mktemp /tmp/webvirtcloud-install.XXXXXX)"
 fi
 chmod 600 "$LOG_FILE" 2>/dev/null || true