Jail the control-panel terminal to the customer's home (chroot)

SECURITY: the browser terminal ran an unconfined login shell as the account's system user, so customers could browse the whole host (/var/www, other tenants, /etc). Run it inside a jailkit chroot instead: a vetted, sudo-scoped launcher (/usr/local/sbin/ladill-jailsh) enters a private mount namespace, bind-mounts ONLY that user's home into /home/jail, and chroots as the user. They can no longer see anything outside their own home. Provisioning committed in deployment/ (setup-terminal-jail.sh + ladill-jailsh) so it is reproducible. Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
2026-06-26 23:41:18 +00:00
parent e86f95ddc7
commit 2a1228b40e
4 changed files with 95 additions and 1 deletions
@@ -0,0 +1,25 @@
+#!/bin/bash
+# Ladill jailed shell for the hosting browser terminal. Confines a hosting
+# account to /home/jail with only its own home bind-mounted (private mount ns).
+# Usage: ladill-jailsh <username> [relpath]
+set -euo pipefail
+JAIL=/home/jail
+U=${1:-}
+REL=${2:-/public_html}
+[ -n "$U" ] || { echo 'usage: ladill-jailsh <user> [relpath]'; exit 2; }
+# resolve + validate the target user (must be a real hosting account)
+UID_=$(id -u "$U" 2>/dev/null || true)
+GID_=$(id -g "$U" 2>/dev/null || true)
+[ -n "$UID_" ] && [ "$UID_" -ge 1000 ] || { echo 'refusing: not a hosting user'; exit 1; }
+HOMEDIR=/home/$U
+[ -d "$HOMEDIR" ] || { echo 'no home directory'; exit 1; }
+case "$REL" in *..*) REL=/public_html;; esac
+mkdir -p "$JAIL/home/$U"
+# re-exec into a private mount namespace so the bind is per-session
+if [ -z "${LADILL_JAIL_NS:-}" ]; then
+  exec env LADILL_JAIL_NS=1 unshare --mount --propagation private -- "$0" "$U" "$REL"
+fi
+mount --bind "$HOMEDIR" "$JAIL/home/$U"
+export HOME="/home/$U" USER="$U" LOGNAME="$U" SHELL=/bin/bash PATH=/usr/bin:/bin
+export TERM="${TERM:-xterm-256color}"
+exec /usr/sbin/chroot --userspec="$UID_:$GID_" "$JAIL" /bin/bash -l -c "cd '/home/$U$REL' 2>/dev/null || cd ~; exec /bin/bash -l"
@@ -0,0 +1,40 @@
+#!/usr/bin/env bash
+# Provision the jailkit chroot used by the control-panel browser terminal so the
+# customer shell is confined to its own home (cannot see /var/www, other tenants,
+# /etc, or secrets). Idempotent; run as root on each hosting node.
+set -Eeuo pipefail
+
+JAIL=/home/jail
+
+echo "==> Installing jailkit"
+export DEBIAN_FRONTEND=noninteractive
+command -v jk_init >/dev/null 2>&1 || apt-get install -y jailkit
+
+echo "==> Building jail tree at $JAIL"
+jk_init -j "$JAIL" uidbasics netbasics basicshell interactiveshell extendedshell editors netutils terminfo || true
+jk_cp -j "$JAIL" /usr/bin/id /usr/bin/whoami /usr/bin/find /usr/bin/grep /usr/bin/less \
+  /usr/bin/head /usr/bin/tail /usr/bin/du /usr/bin/df /usr/bin/wc /usr/bin/clear /usr/bin/sed /usr/bin/awk || true
+
+# Terminal definitions (xterm*) for a usable TTY.
+mkdir -p "$JAIL/usr/share/terminfo"
+cp -rn /usr/share/terminfo/x "$JAIL/usr/share/terminfo/" 2>/dev/null || true
+
+# Non-listable jail /home (each session bind-mounts only its own home here).
+install -d -o root -g root -m 711 "$JAIL/home"
+install -d -m 1777 "$JAIL/tmp"
+
+echo "==> Syncing hosting users into the jail passwd/group (for name resolution)"
+while IFS=: read -r name _ uid gid _ home shell; do
+  [ "$uid" -ge 1000 ] 2>/dev/null || continue
+  [ -d "/home/$name" ] || continue
+  grep -q "^$name:" "$JAIL/etc/passwd" || getent passwd "$name" >> "$JAIL/etc/passwd"
+  grep -q "^$name:" "$JAIL/etc/group" || getent group "$name" >> "$JAIL/etc/group"
+done < <(getent passwd)
+
+echo "==> Installing the jailed-shell launcher + scoped sudoers"
+install -o root -g root -m 755 "$(dirname "$0")/ladill-jailsh" /usr/local/sbin/ladill-jailsh
+echo 'www-data ALL=(root) NOPASSWD: /usr/local/sbin/ladill-jailsh *' > /etc/sudoers.d/ladill-jailsh
+chmod 440 /etc/sudoers.d/ladill-jailsh
+visudo -cf /etc/sudoers.d/ladill-jailsh
+
+echo "==> Done. Customer terminals now run jailed in $JAIL."