puppet: Always set the RabbitMQ nodename to zulip@localhost.

This is required in order to lock down the RabbitMQ port to only
listen on localhost.  If the nodename is `rabbit@hostname`, in most
circumstances the hostname will resolve to an external IP, which the
rabbitmq port will not be bound to.

Installs which used `rabbit@hostname`, due to RabbitMQ having been
installed before Zulip, would not have functioned if the host or
RabbitMQ service was restarted, as the localhost restrictions in the
RabbitMQ configuration would have made rabbitmqctl (and Zulip cron
jobs that call it) unable to find the rabbitmq server.

The previous commit ensures that configure-rabbitmq is re-run after
the nodename has changed.  However, rabbitmq needs to be stopped
before `rabbitmq-env.conf` is changed; we use an `onlyif` on an `exec`
to print the warning about the node change, and let the subsequent
config change and notify of the service and configure-rabbitmq to
complete the re-configuration.

docs/overview/changelog.md

@@ -121,6 +121,11 @@ log][commit-log] for an up-to-date list of raw changes.
 
 ## Zulip 4.x series
 
+- Removed the `rabbitmq.nodename` configuration in `zulip.conf`; all
+  RabbitMQ instances will be reconfigured to have a nodename of
+  `zulip@localhost`. You can remove this setting from your
+  `zulip.conf` configuration file, if it exists.
+
 ## Zulip 4.8 -- 2021-12-01
 
 - CVE-2021-43791: Zulip could fail to enforce expiration dates

docs/production/deployment.md

@@ -728,12 +728,6 @@ connections.
 The version of PostgreSQL that is in use. Do not set by hand; use the
 [PostgreSQL upgrade tool](../production/upgrade-or-modify.html#upgrading-postgresql).
 
-### `[rabbitmq]`
-
-#### `nodename`
-
-The name used to identify the local RabbitMQ server; do not modify.
-
 ### `[memcached]`
 
 #### `memory`

puppet/zulip/files/rabbitmq/rabbitmq-env.conf

@@ -3,12 +3,8 @@
 # combination. See the clustering on a single machine guide for details:
 # http://www.rabbitmq.com/clustering.html#single-machine
 #
-# By default, we set nodename to rabbit@localhost so it will always resolve
-<% if @rabbitmq_nodename != '' -%>
-NODENAME=<%= @rabbitmq_nodename %>
-<% else -%>
-NODENAME=rabbit
-<% end -%>
+# By default, we set nodename to zulip@localhost so it will always resolve
+NODENAME=zulip@localhost
 
 # By default RabbitMQ will bind to all interfaces, on IPv4 and IPv6 if
 # available. Set this if you only want to bind to one network interface or#

puppet/zulip/manifests/profile/rabbitmq.pp

@@ -16,6 +16,12 @@ class zulip::profile::rabbitmq {
     ensure => absent,
   }
 
+  file { '/etc/rabbitmq':
+    ensure => 'directory',
+    owner  => 'root',
+    group  => 'root',
+    mode   => '0755',
+  }
   file { '/etc/rabbitmq/rabbitmq.config':
     ensure  => file,
     require => Package[rabbitmq-server],
@@ -24,26 +30,27 @@ class zulip::profile::rabbitmq {
     mode    => '0644',
     source  => 'puppet:///modules/zulip/rabbitmq/rabbitmq.config',
   }
-
-  $rabbitmq_nodename = zulipconf('rabbitmq', 'nodename', '')
-  if $rabbitmq_nodename != '' {
-    file { '/etc/rabbitmq':
-      ensure => 'directory',
-      owner  => 'root',
-      group  => 'root',
-      mode   => '0755',
+  exec { 'warn-rabbitmq-nodename-change':
+    command   => "${::zulip_scripts_path}/lib/warn-rabbitmq-nodename-change",
+    onlyif    => '[ -f /etc/rabbitmq/rabbitmq-env.conf ] && ! grep -xq NODENAME=zulip@localhost /etc/rabbitmq/rabbitmq-env.conf',
+    before    => [
+      File['/etc/rabbitmq/rabbitmq-env.conf'],
+      Service['rabbitmq-server'],
+    ],
+    logoutput => true,
+    loglevel  => 'warning',
   }
-
   file { '/etc/rabbitmq/rabbitmq-env.conf':
     ensure => file,
-      require => File['/etc/rabbitmq'],
-      before  => [Package[rabbitmq-server], Service[rabbitmq-server]],
-      notify  => Exec['configure-rabbitmq'],
     owner  => 'root',
     group  => 'root',
     mode   => '0644',
-      content => template('zulip/rabbitmq-env.conf.template.erb'),
-    }
+    source => 'puppet:///modules/zulip/rabbitmq/rabbitmq-env.conf',
+    before => Package['rabbitmq-server'],
+    notify => [
+      Service['rabbitmq-server'],
+      Exec['configure-rabbitmq'],
+    ],
   }
   # epmd doesn't have an init script, so we just check if it is
   # running, and if it isn't, start it.  Even in case of a race, this

scripts/lib/install

@@ -433,29 +433,6 @@ EOF
     if [ -n "$POSTGRESQL_DATABASE_USER" ]; then
         crudini --set /etc/zulip/zulip.conf postgresql database_user "$POSTGRESQL_DATABASE_USER"
     fi
-
-    # Note: there are four dpkg-query outputs to consider:
-    #
-    # root@host# dpkg-query --showformat '${Status}\n' -W rabbitmq-server 2>/dev/null
-    # root@host# apt install rabbitmq-server
-    # root@host# dpkg-query --showformat '${Status}\n' -W rabbitmq-server 2>/dev/null
-    # install ok installed
-    # root@host# apt remove rabbitmq-server
-    # root@host# dpkg-query --showformat '${Status}\n' -W rabbitmq-server 2>/dev/null
-    # deinstall ok config-files
-    # root@host# apt purge rabbitmq-server
-    # root@host# dpkg-query --showformat '${Status}\n' -W rabbitmq-server 2>/dev/null
-    # unknown ok not-installed
-    #
-    # (There are more possibilities in the case of dpkg errors.)  Here
-    # we are checking for either empty or not-installed.
-    if ! dpkg-query --showformat '${Status}\n' -W rabbitmq-server 2>/dev/null | grep -vq ' not-installed$'; then
-        cat <<EOF >>/etc/zulip/zulip.conf
-
-[rabbitmq]
-nodename = zulip@localhost
-EOF
-    fi
 fi
 
 if has_class "zulip::app_frontend_base"; then

scripts/lib/warn-rabbitmq-nodename-change

@@ -0,0 +1,29 @@
+#!/usr/bin/env bash
+
+# For security reasons, we need to configure RabbitMQ to listen only
+# on localhost, which we cannot do if the nodename contains the
+# hostname (e.g. rabbit@zulip-host).  Containing the hostname also
+# makes it brittle to hostname changes, which are (for example) common
+# in containerized environments.
+
+set -eu
+
+# Try to find the current nodename
+CURRENT=$(sh -c 'cd /usr/lib/rabbitmq/bin/ && . ./rabbitmq-env && echo $NODENAME')
+if [ "$CURRENT" != "zulip@localhost" ]; then
+    cat <<EOF
+
+***** WARNING *****
+
+We are renaming the rabbitmq server's nodename from '$CURRENT' to
+'zulip@localhost', as rabbitmq is being reconfigured to listen only on
+localhost.  This will also make the server more resilient to hostname
+changes.  This will only affect you if you were using the rabbitmq
+server for other, non-Zulip uses.
+
+*******************
+
+EOF
+
+    service rabbitmq-server stop || true
+fi