Make the docker environment variables available to cron jobs (#1158)

cron jobs don't have access to the docker environment variables.
This, on instance launch, writes the environment to a file and
configured the mozdef crontab to use this on disk environment

docker/compose/docker-compose-cloudy-mozdef.yml

@@ -84,7 +84,7 @@ services:
     env_file:
       - cloudy_mozdef.env
     restart: always
-    command: bash -c 'crond -n'
+    command: bash -c 'cd / && bash launch_cron'
     volumes:
       - cron:/opt/mozdef/envs/mozdef/cron
       - geolite_db:/opt/mozdef/envs/mozdef/data/

docker/compose/mozdef_cron/Dockerfile

@@ -20,7 +20,12 @@ COPY docker/compose/mozdef_cron/files/syncAlertsToMongo.conf /opt/mozdef/envs/mo
 
 RUN chown -R mozdef:mozdef /opt/mozdef/envs/mozdef/cron
 
+# https://stackoverflow.com/a/48651061/168874
+COPY docker/compose/mozdef_cron/files/launch_cron /launch_cron
+
 USER mozdef
 RUN crontab /cron_entries.txt
 
 USER root
+WORKDIR /
+CMD ['./launch_cron']

docker/compose/mozdef_cron/files/cron_entries.txt

@@ -1,3 +1,4 @@
+BASH_ENV=/env
 * * * * * /opt/mozdef/envs/mozdef/cron/healthAndStatus.sh
 * * * * * /opt/mozdef/envs/mozdef/cron/healthToMongo.sh
 * * * * * /opt/mozdef/envs/mozdef/cron/collectAttackers.sh

docker/compose/mozdef_cron/files/launch_cron

@@ -0,0 +1,5 @@
+#!/bin/bash
+
+# Export all root users environment variables, filtering out non custom variables and write them into /env
+declare -p | egrep -v ' HOSTNAME=| LS_COLORS=| TERM=| PATH=| PWD=| TZ=| SHLVL=| HOME=| LESSOPEN=| _=| affinity:container=| BASHOPTS=| BASH_VERSINFO=| EUID=| PPID=| SHELLOPTS=| UID=' > /env
+crond -n -x ext,sch,proc