diff --git a/scripts/entrypoint.sh b/scripts/entrypoint.sh index 109fbc7..7e70b2d 100755 --- a/scripts/entrypoint.sh +++ b/scripts/entrypoint.sh @@ -19,8 +19,53 @@ else echo "User $user already exists" fi -mkdir -p /home/$user/app -mkdir -p /home/$user/logs/{nginx,nodejs} +# ---- root never follows customer symlinks under /home/$user ---- +# /home/$user is the customer's bind mount: they can plant symlinks in it, and +# root touching/chowning/writing through one (e.g. logs/nginx -> /etc) gives +# them that target. logs/ is WHP-owned and nginx opens files in it as root, so +# symlinks there are removed and logged; everything under /home/$user is created/written AS THE CUSTOMER. +as_user() { + if command -v setpriv >/dev/null 2>&1; then + setpriv --reuid="$uid" --regid="$uid" --init-groups -- "$@" + else + runuser -u "$user" -- "$@" + fi +} +# Fail closed: refusing to start only hurts the customer who planted the path, +# which is preferred to root following it. +die() { + echo "entrypoint: FATAL: $* - refusing to start" >&2 + exit 1 +} +# Unlink AS THE CUSTOMER: rm on the final component never touches the link +# target, and if a parent dir is swapped for a symlink mid-way the customer can +# only delete what they already could. Still a symlink afterwards -> refuse to +# start (fail closed). +drop_symlink() { + if [ -L "$1" ]; then + echo "entrypoint: SECURITY: $1 was a symlink to '$(readlink "$1")' - removing" >&2 + as_user rm -f -- "$1" + [ -L "$1" ] && die "could not remove symlink $1" + fi + return 0 +} +if [ -L /home/$user ] || [ ! -d /home/$user ]; then + die "/home/$user is not a real directory" +fi +chown -h $user:$user /home/$user +# app/ may legitimately be a symlink (releases/current deploys): it is left +# alone, and every root-side operation on it below runs as the customer. +drop_symlink /home/$user/logs +if [ -d /home/$user/logs ]; then + # nginx opens its logs here as root. As the customer: find without -L never + # follows symlinks, -delete unlinks the link itself, and a raced parent swap + # can only reach what the customer could already delete. Re-checked + # fail-closed immediately before nginx starts. + as_user find /home/$user/logs -xdev -type l \ + -printf 'entrypoint: SECURITY: %p was a symlink to %l - removed\n' -delete >&2 || true +fi + +as_user mkdir -p /home/$user/app /home/$user/logs/nginx /home/$user/logs/nodejs # Link log directories rm -rf /var/log/nginx @@ -30,9 +75,31 @@ ln -s /home/$user/logs/nodejs /var/log/nodejs # Configure nginx for reverse proxy /scripts/create-nginx-config.sh -# Set ownership and permissions +# Set ownership and permissions. GNU chown -R defaults to -P: symlinks are +# lchown()ed, never followed. chown -R $user:$user /home/$user -chmod -R 755 /home/$user +# Do NOT `chmod -R 755` here. /home/$user is the customer's bind-mounted +# directory; a recursive 755 on every start made every file (.env, app +# secrets) world-readable AND executable, and reverted any tighter +# permissions the customer had set. nginx workers run as `nginx` (not the +# customer) and serve /static/ straight from /home/$user/app/public/, so they +# only need to traverse directories. Normalise that and nothing else: open the +# home dir itself (adduser -m creates it 0700 when it does not exist yet), and +# add o+x to directories that lack it. Regular files are never touched. +# The find runs AS THE CUSTOMER: `-type d` without -L skips symlinks, and if a +# dir is swapped for a symlink before chmod runs, the customer can only reach +# what they already own. +chmod 755 /home/$user +as_user find /home/$user -type d ! -perm -o=x -exec chmod o+x {} + 2>/dev/null || true + +# nginx opens its logs under /home/$user/logs as root: last fail-closed check +# immediately before it starts. logs/, logs/nginx, logs/nodejs must be real +# dirs and nothing under logs/ may be other than a regular file or directory. +for d in /home/$user/logs /home/$user/logs/nginx /home/$user/logs/nodejs; do + [ -d "$d" ] && [ ! -L "$d" ] || die "$d is not a real directory" +done +bad=$(find /home/$user/logs -xdev ! -type f ! -type d -print -quit 2>&1) +[ -z "$bad" ] || die "unsafe entry under /home/$user/logs: $bad" # Start nginx nginx @@ -59,15 +126,13 @@ fi # Create app directory if it doesn't exist if [ ! -d /home/$user/app ]; then echo "Creating app directory at /home/$user/app" - mkdir -p /home/$user/app - chown -R $user:$user /home/$user/app + as_user mkdir -p /home/$user/app fi # If app directory is empty, copy the simple-website example if [ -z "$(ls -A /home/$user/app)" ]; then echo "App directory is empty, copying simple-website example..." - cp -r /examples/simple-website/* /home/$user/app/ - chown -R $user:$user /home/$user/app + as_user cp -r /examples/simple-website/. /home/$user/app/ echo "Copied simple-website example to provide a working application" fi @@ -85,8 +150,9 @@ su -c "npm install" $user # Check if ecosystem.config.js exists, if not generate it if [ ! -f /home/$user/app/ecosystem.config.js ]; then echo "No ecosystem.config.js found, generating from package.json..." - /scripts/generate-ecosystem-config.sh "$user" "/home/$user/app" - chown $user:$user /home/$user/app/ecosystem.config.js + # As the customer: it reads their package.json and writes into their app dir. + drop_symlink /home/$user/app/ecosystem.config.js + as_user /scripts/generate-ecosystem-config.sh "$user" "/home/$user/app" fi # Mirror logs to docker logs in the background.