Serve a name the moment it is pointed, with nobody touching the box

scripts/moshpit-reconcile.sh

@@ -0,0 +1,169 @@
+#!/bin/sh
+# Serve every Moshpit name pointed at this box, without anybody touching it.
+#
+# `setup-origin.sh` turned serving one name into one command. This turns it
+# into none: it asks the registry which names point here, and configures the
+# ones that are not configured yet. Point a name at this host in the dashboard
+# and it is being served a minute later — no ssh, no command, no remembering
+# that a pin has to be published or the name stays refused.
+#
+#   sh scripts/moshpit-reconcile.sh                 # act
+#   sh scripts/moshpit-reconcile.sh --dry-run       # say what it would do
+#   sh scripts/moshpit-reconcile.sh --once          # exit non-zero on any failure
+#
+# Config, read from /etc/moshpit/reconcile.conf (override with MOSHPIT_CONF):
+#
+#   MOSHPIT_API_KEY=mck_...              # publishes pins; from /settings
+#   MOSHPIT_ENDINGS="hacker rank 2600"   # the endings this box answers for
+#   MOSHPIT_HOST=dev.profullstack.com    # what a name must point at to count
+#   MOSHPIT_REGISTRY=https://app.moshcode.sh
+#
+# ENDINGS is listed rather than discovered on purpose. `GET /api/moshpit/tlds`
+# returns 200 of the ~5,700 claimed endings — the default page size — so
+# discovery would silently serve a subset and look like it had covered
+# everything. A box that serves three endings should say so in one line.
+#
+# Idempotent, and quiet when there is nothing to do: a name is reconfigured
+# only when its nginx block is missing or the pin the registry publishes is not
+# the key this box actually serves. Without that check every run would reload
+# nginx, and a timer would reload it forever.
+set -eu
+
+CONF="${MOSHPIT_CONF:-/etc/moshpit/reconcile.conf}"
+[ -f "$CONF" ] && . "$CONF"
+
+REGISTRY="${MOSHPIT_REGISTRY:-https://app.moshcode.sh}"
+API_KEY="${MOSHPIT_API_KEY:-}"
+ENDINGS="${MOSHPIT_ENDINGS:-}"
+HOST="${MOSHPIT_HOST:-}"
+ENABLEDIR="${MOSHPIT_ENABLEDIR:-/etc/nginx/sites-enabled}"
+SETUP="${MOSHPIT_SETUP:-$(dirname "$0")/setup-origin.sh}"
+DRY_RUN=0
+FAILURES=0
+
+BOLD=''; DIM=''; RED=''; OFF=''
+if [ -t 2 ]; then BOLD=$(printf '\033[1m'); DIM=$(printf '\033[2m'); RED=$(printf '\033[31m'); OFF=$(printf '\033[0m'); fi
+say()  { printf '%s\n' "$*" >&2; }
+step() { printf '%s==>%s %s\n' "$BOLD" "$OFF" "$*" >&2; }
+warn() { printf '%swarning:%s %s\n' "$RED" "$OFF" "$*" >&2; FAILURES=$((FAILURES + 1)); }
+die()  { printf '%serror:%s %s\n' "$RED" "$OFF" "$*" >&2; exit 1; }
+
+while [ $# -gt 0 ]; do
+  case "$1" in
+    --dry-run) DRY_RUN=1 ;;
+    --once) : ;;  # accepted for the systemd unit; the script is always one pass
+    -h|--help) sed -n '2,28p' "$0" | sed 's/^# \{0,1\}//'; exit 0 ;;
+    *) die "unknown option: $1" ;;
+  esac
+  shift
+done
+
+[ -n "$API_KEY" ] || die "no MOSHPIT_API_KEY — set it in $CONF (get one at $REGISTRY/settings)"
+[ -n "$ENDINGS" ] || die "no MOSHPIT_ENDINGS — list the endings this box serves in $CONF"
+[ -n "$HOST" ]    || die "no MOSHPIT_HOST — set what a name must point at to count as ours"
+[ -f "$SETUP" ]   || die "cannot find setup-origin.sh at $SETUP (set MOSHPIT_SETUP)"
+
+# The addresses HOST has right now. A name may point at the hostname or at a
+# literal, and both mean this box — comparing only the string would skip names
+# pointed at the address and leave them silently unserved.
+OURS="$HOST
+$(getent ahosts "$HOST" 2>/dev/null | awk '{print $1}' | sort -u)"
+
+points_here() {
+  case "$1" in "") return 1 ;; esac
+  for ours in $OURS; do
+    [ "$1" = "$ours" ] && return 0
+  done
+  return 1
+}
+
+# The pin this box serves for a name, computed the same way the registry's
+# publisher computes it. Empty when nothing is listening for that name.
+served_pin() {
+  echo | openssl s_client -connect "127.0.0.1:443" -servername "$1" 2>/dev/null \
+    | openssl x509 -pubkey -noout 2>/dev/null \
+    | openssl pkey -pubin -outform der 2>/dev/null \
+    | openssl dgst -sha256 -binary 2>/dev/null \
+    | openssl enc -base64 2>/dev/null
+}
+
+published_pin() {
+  curl -fsS --max-time 15 "$REGISTRY/api/moshpit/tlds/$2/pins?label=$1" 2>/dev/null \
+    | grep -o '"pin":"[^"]*"' | head -1 | cut -d'"' -f4
+}
+
+# One field out of a flat JSON object. Enough for these payloads, and it keeps
+# this a POSIX shell script with no runtime to install on an origin box.
+json_field() { grep -o "\"$1\":\"[^\"]*\"" | head -1 | cut -d'"' -f4; }
+
+reconcile_name() {
+  name="$1"; label="$2"; tld="$3"
+
+  need=""
+  [ -f "$ENABLEDIR/$name" ] || need="no nginx block"
+  if [ -z "$need" ]; then
+    serving="$(served_pin "$name")"
+    publish="$(published_pin "$label" "$tld")"
+    if [ -z "$serving" ]; then
+      need="nothing is served for it"
+    elif [ -z "$publish" ]; then
+      need="no pin published"
+    elif [ "$serving" != "$publish" ]; then
+      # The published pin is what clients enforce, so a mismatch refuses the
+      # name outright. Worth naming both, because the usual cause is a
+      # certificate regenerated without republishing.
+      need="published pin does not match what is served ($publish vs $serving)"
+    fi
+  fi
+
+  if [ -z "$need" ]; then
+    say "  ${DIM}$name — already served${OFF}"
+    return 0
+  fi
+
+  step "$name — $need"
+  if [ "$DRY_RUN" = "1" ]; then
+    say "  ${DIM}would run: setup-origin.sh $name --target $HOST${OFF}"
+    return 0
+  fi
+
+  if MOSHPIT_API_KEY="$API_KEY" sh "$SETUP" "$name" --target "$HOST" --registry "$REGISTRY" >&2; then
+    say "  ${DIM}$name — now served${OFF}"
+  else
+    warn "$name — setup-origin.sh failed; leaving it alone and carrying on"
+  fi
+}
+
+RECORDS="$(mktemp)"
+trap 'rm -f "$RECORDS"' EXIT INT TERM
+
+step "reconciling against $REGISTRY as $HOST"
+
+for tld in $ENDINGS; do
+  body="$(curl -fsS --max-time 20 "$REGISTRY/api/moshpit/tlds/$tld/names" 2>/dev/null)" || {
+    # A registry that is briefly unreachable must not take the box's existing
+    # names down, and must not look like "no names are pointed here".
+    warn ".$tld — registry unreachable, skipping this pass"
+    continue
+  }
+
+  # One record per line, so the loop never has to parse nested JSON.
+  #
+  # Via a file rather than a pipe into `while`: a piped loop runs in a subshell,
+  # where the failure count increments a copy and the exit status below would
+  # always be 0 — the script would report success for a pass that fixed nothing.
+  printf '%s' "$body" | tr '{' '\n' | grep '"label"' > "$RECORDS" || true
+  while IFS= read -r record; do
+    label="$(printf '%s' "$record" | json_field label)"
+    target="$(printf '%s' "$record" | json_field target)"
+    [ -n "$label" ] || continue
+    points_here "$target" || continue
+    reconcile_name "$label.$tld" "$label" "$tld"
+  done < "$RECORDS"
+done
+
+if [ "$FAILURES" -gt 0 ]; then
+  say ""
+  warn "$FAILURES name(s) could not be reconciled this pass"
+  exit 1
+fi

systemd/moshpit-reconcile.service

@@ -0,0 +1,42 @@
+# Serve every Moshpit name pointed at this box.
+#
+# Oneshot, driven by moshpit-reconcile.timer. Each pass asks the registry which
+# names point here and configures the ones that are not configured yet, so
+# pointing a name in the dashboard is the only step there is.
+#
+# Install:
+#   cp systemd/moshpit-reconcile.* /etc/systemd/system/
+#   systemctl enable --now moshpit-reconcile.timer
+
+[Unit]
+Description=Serve Moshpit names pointed at this host
+Documentation=https://github.com/profullstack/moshpit-proxy
+# Reconfiguring nginx is the point, so do not race its startup.
+After=network-online.target nginx.service
+Wants=network-online.target
+
+[Service]
+Type=oneshot
+ExecStart=/opt/moshpit/scripts/moshpit-reconcile.sh --once
+
+# The API key lives here, not in this unit: unit files are world-readable and
+# `systemctl cat` prints them. 0600 the config instead.
+Environment=MOSHPIT_CONF=/etc/moshpit/reconcile.conf
+
+# A registry that is briefly unreachable is not a reason to give up until the
+# next tick, but retrying forever is not either.
+Restart=on-failure
+RestartSec=30s
+StartLimitBurst=3
+
+# It writes certificates, nginx config, and reloads nginx. That needs root, so
+# narrow what root can reach rather than pretending otherwise.
+ProtectHome=yes
+ProtectKernelTunables=yes
+ProtectKernelModules=yes
+ProtectControlGroups=yes
+RestrictAddressFamilies=AF_INET AF_INET6 AF_UNIX
+NoNewPrivileges=yes
+
+[Install]
+WantedBy=multi-user.target

systemd/moshpit-reconcile.timer

@@ -0,0 +1,26 @@
+# How often this box checks for names newly pointed at it.
+#
+# A minute is the gap between pointing a name in the dashboard and the site
+# being up. Passes with nothing to do cost one HTTPS request per ending and
+# change nothing on disk, so the cost of checking often is close to zero — and
+# the alternative is somebody ssh-ing in, which is the thing being removed.
+
+[Unit]
+Description=Check for Moshpit names newly pointed at this host
+Documentation=https://github.com/profullstack/moshpit-proxy
+
+[Timer]
+# Soon after boot, because a box that just came up may have missed changes.
+OnBootSec=30s
+OnUnitActiveSec=60s
+
+# Without this every box installed from the same instructions hits the registry
+# on the same second.
+RandomizedDelaySec=15s
+
+# A missed window (box asleep, timer disabled) should run once on return rather
+# than be skipped silently.
+Persistent=true
+
+[Install]
+WantedBy=timers.target