135 lines
5.4 KiB
Bash
Executable File
135 lines
5.4 KiB
Bash
Executable File
#!/usr/bin/bash
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#############################################################################################################
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# check-postfix.sh #
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#############################################################################################################
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# #
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# This script is just something I cooked up for work. I setup a server with posftix configured as an` #
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# email/smtp relay so that some of our old equipment can still function without having to try and #
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# configure our commercial Email Server to accept unauthed requests to send email. #
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# #
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# This requres a few packages to be installed: #
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# - postfix (of course) #
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# - telnet #
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# - sendmail #
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# #
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# The issue is if the postfix service dies and fails to come back up after a restart via this script, #
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# you will be unable to send any emails via a smtp client (as they will try to contact the service #
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# on the server itself). So the only workaround I was able to find is to manually send the email via #
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# telnet using a coproc. You could use a smtp library with python or perl, but I like to keep these #
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# scripts using a single language wherever possible. #
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# #
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# Since telnet is just a basic tcp client we are able to interact with the smpt port on a mailserver #
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# (port 25). So setting it up as coproc allows us to run a concurrent process and pipe commands into #
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# the file-descriptor to send the commands to the mailserver. Which allows us to manually send an email #
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# to an authoritative email server (provided they don't have your IP blocklisted or are filtering #
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# traffic on port 25). #
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# #
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#############################################################################################################
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# BEGIN: Variables
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## Duration to wait to see if service has come back up
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DURATION=10
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## Wait duration to send next part of message
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WAIT=1
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## Test flag
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TEST=0
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## Email addresses
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NOTIFY_EMAIL=recipient@domain.com
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MAIL_FROM=username@domain.net
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FROM_DOMAIN=` echo $FROM_EMAIL | cut -d @ -f 2 `
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DAMAIN=` echo $NOTIFY_EMAIL | cut -d @ -f 2 `
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# END: Variables
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# BEGIN: Helper Functions
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send_email () {
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local MESSAGE="${1:?"send_email: No message was passed through"}"
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sendmail $NOTIFY_EMAIL <<< "$MESSAGE"
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}
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: "
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The only option is to manually telnet to the smtp port on the authoritative mailserver for the target domain. As otherwise unless a mail-host is configured as an email relay, you will be unable to send an email to a user outside of the mailservers domain (without authentication).
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"
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do_emergency_email () {
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local MESSAGE="${1:-"The Postfix service has failed to come up on `hostname` (`hostname -i`) after a service restart. Please ssh into server to troubleshoot the issues."}"
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## Getting a mailserver IP for manual message
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MAILSERVER=`dig $DOMAIN mx | grep -Eo '[0-9]+\.[0-9]+\.[0-9]+\.[0-9]+' | head -n 1`
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## Setting up coprocess to send commands to telnet session coproc TELNET { telnet $MAILSERVER 25; }
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coproc TELNET { telnet $MAILSERVER 25; }
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## Commands to send email manually
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local -a commands=(
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"ehlo $FROM_DOMAIN\n"
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"mail from: <$MAIL_FROM>\n"
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"rcpt to: <$NOTIFY_EMAIL>\n"
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"data\n"
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"Subject: Postfix Service Failure\nFrom: $MAIL_FROM\nTo: $NOTIFY_EMAIL\n"
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"$MESSAGE\n\n.\n"
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"quit\n"
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)
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## Iterate through commands and send them to coprocesses
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### We need to wait before each command as the remote mailserver will not catch everything otherwise.
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for i in ${!commands[@]}; do
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COMMAND="${commands[$i]}"
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echo -e "$COMMAND" >&${TELNET[1]}
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sleep $WAIT
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done
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}
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# END: Helper Functions
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# BEGIN: Test Check
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if [[ $TEST -eq 1 ]]; then
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MESSAGE_1="
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This is a test message to verify that postfix can send an email
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"
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send_email "$MESSAGE_1"
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MESSAGE_2="This is a test email to make sure the postfix crash workaround email works"
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do_emergency_email "$MESSAGE_2"
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exit
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fi
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# END: Test Check
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# BEGIN: Work
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if [[ `systemctl is-active postfix` != 'active' ]]; then
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systemctl restart postfix
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sleep $DURATION
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SERVICE_STATUS=` systemctl is-active postfix `
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if [[ "$SERVICE_STATUS" == 'active' ]]; then
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MESSAGE="
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SUBJECT: Postfix Service Failure
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FROM: root
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TO: $NOTIFY_EMAIL
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The postfix service on `hostname` (`hostname -i`) was found to be not running.
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The service has been restarted, and after waiting $DURATION seconds it was found to be $SERVICE_STATUS.
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"
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send_email "$MESSAGE"
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else
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do_emergency_email
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fi
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fi
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# END: Work
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