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fix(docker): validate HERMES_UID/GID to prevent privilege escalation in stage2-hook #34119

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fix(docker): validate HERMES_UID/GID to prevent privilege escalation in stage2-hook #34119

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11 changes: 9 additions & 2 deletions docker/stage2-hook.sh
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Original file line number Diff line number Diff line change
Expand Up @@ -32,12 +32,19 @@ INSTALL_DIR="/opt/hermes"
# is a no-op if the dir already exists. (#18482, salvages #18488)
mkdir -p "$HERMES_HOME"

# Numeric UID/GID validation: must be digits only, 1000-65534
validate_uid_gid() {
case "$1" in
''|*[!0-9]*) return 1 ;;
*) [ "$1" -ge 1000 ] && [ "$1" -le 65534 ] ;;
esac
}
# --- UID/GID remap ---
if [ -n "${HERMES_UID:-}" ] && [ "$HERMES_UID" != "$(id -u hermes)" ]; then
if [ -n "${HERMES_UID:-}" ] && validate_uid_gid "$HERMES_UID" && [ "$HERMES_UID" != "$(id -u hermes)" ]; then
echo "[stage2] Changing hermes UID to $HERMES_UID"
usermod -u "$HERMES_UID" hermes
fi
if [ -n "${HERMES_GID:-}" ] && [ "$HERMES_GID" != "$(id -g hermes)" ]; then
if [ -n "${HERMES_GID:-}" ] && validate_uid_gid "$HERMES_GID" && [ "$HERMES_GID" != "$(id -g hermes)" ]; then
echo "[stage2] Changing hermes GID to $HERMES_GID"
# -o allows non-unique GID (e.g. macOS GID 20 "staff" may already
# exist as "dialout" in the Debian-based container image).
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