From da8ae9e511a94d828877d6c12467f4dc8e2a4383 Mon Sep 17 00:00:00 2001 From: W-Mark Kubacki <wmark@hurrikane.de> Date: Wed, 11 May 2016 20:48:47 +0200 Subject: [PATCH] systemd: Run caddy with even less privileges and more confined The exemplary unit file for systemd is intentionally redundant at times, for example dropping privileges which an unprivileged user "www-data" did not have in the first place: To aid as fallback in case the file gets copied and an operator setting UID to 0 (which reportedly happened in the past). --- dist/init/linux-systemd/README.md | 25 +++++++++++++ dist/init/linux-systemd/caddy.service | 50 ++++++++++++++++++++++++++ dist/init/linux-systemd/caddy@.service | 23 ------------ 3 files changed, 75 insertions(+), 23 deletions(-) create mode 100644 dist/init/linux-systemd/caddy.service delete mode 100644 dist/init/linux-systemd/caddy@.service diff --git a/dist/init/linux-systemd/README.md b/dist/init/linux-systemd/README.md index 61ffb3381..908954c6d 100644 --- a/dist/init/linux-systemd/README.md +++ b/dist/init/linux-systemd/README.md @@ -4,6 +4,25 @@ Please do not hesitate to ask if you have any questions. ## Quickstart +The provided unit file assumes that you want to run caddy as `www-data` and group `www-data`, +both having UID and GID 33 here. +Adjust this to your liking according to the preferences of you Linux distribution! + +```bash +groupadd -g 33 www-data +useradd \ + -g www-data --no-user-group \ + --home-dir /var/www --no-create-home \ + --shell /usr/sbin/nologin \ + --system --uid 33 www-data + +mkdir /etc/caddy +chown -R root:www-data /etc/caddy +mkdir /etc/ssl/caddy +chown -R www-data:root /etc/ssl/caddy +chmod 0770 /etc/ssl/caddy +``` + - Install the unit configuration file: `cp caddy.service /etc/systemd/system/` - Reload the systemd daemon: `systemctl daemon-reload` - Make sure to [configure](#configuration) the service unit before starting caddy. @@ -52,3 +71,9 @@ sudo -u www-data -g www-data -s \ `systemctl kill --signal=USR1 caddy.service` - If you have more files that start with `caddy` – like a `caddy.timer`, `caddy.path`, or `caddy.socket` – then it is important to append `.service`. Although if `caddy.service` is all you have, then you can just use `caddy` without any extension, such as in: `systemctl status caddy` + +- You can make your other certificates and private key files accessible to a user `www-data` by command `setfacl`, if you must: + +```bash +setfacl -m user:www-data:r-- /etc/ssl/private/my.key +``` diff --git a/dist/init/linux-systemd/caddy.service b/dist/init/linux-systemd/caddy.service new file mode 100644 index 000000000..aa5020ebd --- /dev/null +++ b/dist/init/linux-systemd/caddy.service @@ -0,0 +1,50 @@ +[Unit] +Description=Caddy HTTP/2 web server +Documentation=https://caddyserver.com/docs +After=network-online.target +Wants=network-online.target systemd-networkd-wait-online.service + +[Service] +Restart=on-failure + +; User and group the process will run as. +User=www-data +Group=www-data + +; Letsencrypt-issued certificates will be written to this directory. +Environment=HOME=/etc/ssl/caddy + +; Always set "-root" to something safe in case it gets forgotten in the Caddyfile. +ExecStart=/usr/bin/caddy -log stdout -agree=true -conf=/etc/caddy/Caddyfile -root=/var/tmp +ExecReload=/bin/kill -USR1 $MAINPID + +; Limit the number of file descriptors; see `man systemd.exec` for more limit settings. +LimitNOFILE=1048576 +; Unmodified caddy is not expected to use more than that. +LimitNPROC=64 + +; Use private /tmp and /var/tmp, which are discarded after caddy stops. +PrivateTmp=true +; Use a minimal /dev +PrivateDevices=true +; Hide /home, /root, and /run/user. Nobody will steal your SSH-keys. +ProtectHome=true +; Make /usr, /boot, /etc and possibly some more folders read-only. +ProtectSystem=full +; … except /etc/ssl/caddy, because we want Letsencrypt-certificates there. +; This merely retains r/w access rights, it does not add any new. Must still be writable on the host! +ReadWriteDirectories=/etc/ssl/caddy + +; Drop all other capabilities. Important if you run caddy as privileged user (which you should not). +CapabilityBoundingSet=CAP_NET_BIND_SERVICE +; … but permit caddy to open ports reserved for system services. +; This could be redundant here, but is needed in case caddy runs as nobody:nogroup. +AmbientCapabilities=CAP_NET_BIND_SERVICE +; … and prevent gaining any new privileges. +NoNewPrivileges=true + +; Caveat: Some plugins need additional capabilities. Add them to both above lines. +; - plugin "upload" needs: CAP_LEASE + +[Install] +WantedBy=multi-user.target diff --git a/dist/init/linux-systemd/caddy@.service b/dist/init/linux-systemd/caddy@.service deleted file mode 100644 index 0baaac108..000000000 --- a/dist/init/linux-systemd/caddy@.service +++ /dev/null @@ -1,23 +0,0 @@ -; see `man systemd.unit` for configuration details -; the man section also explains *specifiers* `%x` - -[Unit] -Description=Caddy HTTP/2 web server %I -Documentation=https://caddyserver.com/docs -After=network-online.target -Wants=network-online.target -Wants=systemd-networkd-wait-online.service - -[Service] -; run user and group for caddy -User=%i -Group=http -ExecStart=/usr/bin/caddy -agree=true -conf=/etc/caddy/Caddyfile -Restart=on-failure -; create a private temp folder that is not shared with other processes -PrivateTmp=true -; limit the number of file descriptors, see `man systemd.exec` for more limit settings -LimitNOFILE=8192 - -[Install] -WantedBy=multi-user.target