bashmail.sh

#!/bin/bash

#This script sends an email using as little dependencies as possible
#Copyright (C) 2019 Eduardo Diaz Comellas - ediaz@ultreia.es
#
#This program is free software: you can redistribute it and/or modify it
#under the terms of the GNU General Public License as published by the
#Free Software Foundation, either version 3 of the License, or (at your
#option) any later version.
#
#This program is distributed in the hope that it will be useful, but
#WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY
#or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
#for more details.
#
#You should have received a copy of the GNU General Public License
#along with this program. If not, see http://www.gnu.org/licenses/.

# Several ideas taken from dldnh at
#https://stackoverflow.com/questions/9998710/is-it-possible-to-send-mails-by-bash-script-via-smtp
#Contribution by eXtremeSHOK


#Customize smtp server, protocol, port, login and password.
#Server to use as MTA
SMTPSERVER=my.mail.server.com
#Port (can be left blank and will be deduced). We rather use 587 for submission,
#as 25 is usually firewalled
SMTPPORT=
#USESSL=1 -> send using SSL, USESSL=2 -> send with STARTTLS
#USESSL=0 -> no encryption... beware that password will be sent in plaintext
#If USESSL is different to [012], will use no encryption and default to port 25
USESSL=2
#Auth type to use, can be login, plain or none. If left empty, "none" is selected
USEAUTH=login
#Login and password to use
LOGIN=mylogincredential
PASSWORD=mypassword
#How much seconds to wait for an SMTP answer from the server
#Beware that a value under 5 may cause timeouts in normal operation
SMTPTIMEOUT=10
#How will we identify ourselves at the HELO time. Leave empty for system hostname
HELOHOSTNAME=
#Optional openssl command modifiers
OPENSSLOPTIONS=""
#Override system config file
#If set to 1, we will not read the /etc/bashmail.conf file
SYSCONFOVERRIDE=0

#Now we try to discover several variables if they are not previously declared
#No modifications below this line should be neccesary . Jump to the section
#called #MYEMAILMESSAGEHERE

# If there is a system configuration file and we can read it, then source it
if [ ${SYSCONFOVERRIDE:=0} -eq 0 ]
then
    if [ -r bashmail.conf ]
    then
        echo "Reading system variables from bashmail.con"
        . bashmail.conf
elif [ -r /etc/bashmail.conf ]
    then
        echo "Reading system variables from /etc/bashmail.conf"
        . /etc/bashmail.conf
    fi
fi

#Deduce hostname, if not previously set
DHELOHOSTNAME=${HELOHOSTNAME:-$(hostname)}

#Set a default for USESSL (SSL, port 465)
DUSESSL=${USESSL:-1}

#Provide a SMTPPORT, if empty
if [ -z $SMTPPORT ]
then
    case $DUSESSL in
        0)
            SMTPPORT=587
            ;;
        1)
            SMTPPORT=465
            ;;
        2)
            SMTPPORT=587
            ;;
        *)
            echo >&2 "Warning: USESSL has unrecognized value. Defaulting to port 25 and no encryption"
            SMTPPORT=25
            ;;
    esac
fi

if [ $DUSESSL -eq 2 ]
then
    OPENSSLOPTIONS=" -starttls smtp $OPENSSLOPTIONS "
fi

if [ $SMTPPORT -eq 25 ]
then
    echo >&2 "Warning: using port 25 can be problematic. Consider 587"
fi

if [ -z $USEAUTH ]
then
    USEAUTH=none
elif [ $USEAUTH != "none" ] && [ $USEAUTH != "login" ] && [ $USEAUTH != "plain" ]
then
    echo >&2 "ERROR: Unrecognized value for USEAUTH. Please set it to none, plain or login"
    exit 1
fi


#Make sure we have an SMTPTIMEOUT value
DSMTPTIMEOUT=${SMTPTIMEOUT:-4}

# Check that we have cut and grep. Should be in any sensible UNIX-like system anyway
hash cut 2>/dev/null || { echo >&2 "ERROR: cut command is required but not available. Aborting."; exit 1; }
hash grep 2>/dev/null || { echo >&2 "ERROR: grep command is required but not available. Aborting."; exit 1; }

# Check if we have base64 (needed for auth)
if [ $USEAUTH == "plain" ] || [ $USEAUTH == "login" ]
then
    hash base64 2>/dev/null || { echo >&2 "ERROR: base64 command is required but not available. Aborting."; exit 1; }
fi

#Some other things needed if we use ssl
if [ $USESSL -eq 1 -o $USESSL -eq 2 ]
then
    hash openssl 2>/dev/null || { echo >&2 "ERROR: Encryption required but openssl is not available. Aborting."; exit 1; }
    hash mkfifo 2>/dev/null || { echo >&2 "ERROR: mkfifo command is required but not available. Aborting."; exit 1; }
    hash mktemp 2>/dev/null || { echo >&2 "ERROR: mktemp command is required but not available. Aborting."; exit 1; }
fi



#Function used to check the SMTP status
function checkStatus {
    #echo call: checkStatus $1 $2
    expect=250
    code=`echo $1 | cut -d- -f1`
    line=$2
    numparams=$#
    if [ $numparams -eq 3 ] ; then
        expect="${3}"
    else
        if [ $numparams -ne 2 ] ; then
            echo >&2 "Error on call to checkStatus. Incorrect number of parameters $#"
            exit 2
        fi
    fi
    if [ -z $code ]
    then
        echo >&2 "Error: was expecting ${expect} but received blank. ${1} ${2}"
        exit 2
elif [ $code -ne $expect ]
    then
        echo >&2  "Error: was expecting ${expect} but received ${1}:  ${2}"
        exit 2
    fi
}

#Where all the magic happens
bashmail () {
    from_addr="$1"
    to_addr="$2"
    cc_addr="$3"
    subject="$4"
    body="$5"
    #This vars are initialized at the top of the script
    myhostname=$DHELOHOSTNAME
    smtpserver=$SMTPSERVER
    smtpport=$SMTPPORT
    ssl=$USESSL
    auth=$USEAUTH
    username=$LOGIN
    password=$PASSWORD
    timeout=$DSMTPTIMEOUT


    #Flag initialization. Dont modify
    loginsupported=0
    plainsupported=0


    if [ $ssl -eq 1 ] || [ $ssl -eq 2 ]
    then
        FIFODIR=`mktemp -d`
        mkfifo ${FIFODIR}/sto
        mkfifo ${FIFODIR}/ots
        #This has to be in background
        openssl s_client -connect ${smtpserver}:${smtpport} ${OPENSSLOPTIONS} -ign_eof  -quiet -verify_quiet >& ${FIFODIR}/ots < ${FIFODIR}/sto &
        #This is tricky... dont change order
        exec 4< ${FIFODIR}/ots
        exec 3> ${FIFODIR}/sto
        OUTFD=3
        INFD=4
    else
        exec 3<>/dev/tcp/${smtpserver}/${smtpport}
        OUTFD=3
        INFD=3
    fi

    read -t ${timeout} -u ${INFD} line
    #If using openssl and connection fails, an error line is captured
    echo $line | grep -i error  > /dev/null
    if [ $? -eq 0 ]
    then
        echo >&2 "ERROR: Connection to ${smtpserver}:${smtpport} failed"
        exit 4
    fi

    #checkStatus "$sts" "$line" 220

    echo "EHLO ${myhostname}" >&${OUTFD}

    read -t ${timeout} -u ${INFD} sts line
    checkStatus "$sts" "$line"

    SAL=0
    while [ $SAL -eq 0 ]
    do
        #We are going to read all the remainder lines, one at a time
        #until it timeouts (1sec)
        read -u ${INFD}  -t 1 linea
        SAL=$?
        #Check if auth login is supported
        echo $linea |grep -i auth | grep -i login > /dev/null
        if [ $? -eq 0 ]; then
            loginsupported=1
        fi
        echo $linea |grep -i auth | grep -i plain > /dev/null
        if [ $? -eq 0 ]; then
            plainsupported=1
        fi
    done

    if [ ${auth} == "login" ]
    then
        if [ ${loginsupported} -ne 1 ]
        then
            echo >&2 "ERROR: AUTH LOGIN requested, but not advertised"
            exit 3
        fi
        #echo "Voy a autenticarme ${sts} ${line}"
        userB64=`echo -ne ${username} | base64`
        passB64=`echo -ne ${password} | base64`
        echo "AUTH LOGIN" >&${OUTFD}
        read -t ${timeout} -u ${INFD} sts line
        checkStatus "$sts" "$line" 334
        echo ${userB64} >&${OUTFD}
        read -t ${timeout} -u ${INFD} sts line
        checkStatus "$sts" "$line" 334
        echo ${passB64} >&${OUTFD}
        read -t ${timeout} -u ${INFD} sts line
        checkStatus "$sts" "$line" 235
elif [ ${auth} == "plain" ]
    then
        if [ ${plainsupported} -ne 1 ]
        then
            echo >&2 "ERROR: PLAIN LOGIN requested, but not advertised"
            exit 3
        fi
        #echo "Voy a autenticarme ${sts} ${line}"
        userpassB64=`echo -ne "\0${username}\0${password}" | base64`
        echo "AUTH PLAIN ${userpassB64}" >&${OUTFD}
        read -t ${timeout} -u ${INFD} sts line
        checkStatus "$sts" "$line" 235

    fi

    echo "MAIL FROM: ${from_addr}" >&${OUTFD}

    read -t ${timeout} -u ${INFD} sts line
    checkStatus "$sts" "$line"

    echo "RCPT TO: ${to_addr}" >&${OUTFD}

    read -t ${timeout} -u ${INFD} sts line
    checkStatus "$sts" "$line"

    echo "DATA" >&${OUTFD}

    read -t ${timeout} -u ${INFD} sts line
    checkStatus "$sts" "$line" 354

    if [ ! -z "${cc_addr}" ]
    then
        echo "Cc: ${cc_addr}" >&${OUTFD}
    fi

    echo "Subject: ${subject}" >&${OUTFD}
    echo "" >&${OUTFD}
    echo "${body}" >&${OUTFD}
    echo "." >&${OUTFD}

    read -t ${timeout} -u ${INFD} sts line
    checkStatus "$sts" "$line"

    #Clean up and go home
    exec {OUTFD}>&-
    if [ $ssl -eq 1 -o $ssl -eq 2 ]
    then
        exec {INFD}<&-
        rm ${FIFODIR}/sto ${FIFODIR}/ots
        rm -d  ${FIFODIR}
    fi
}

#MYEMAILMESSAGEHERE
#The sintax is: bashmail from to cc subject body

#You can substitute this variables, set them outside of the script or
#write the command directly below. Comment out the option you don't want

## OPTION1
## If you substitute this variables, please leave the "-" before the default value
FROMADDRESS=${FROMADDRESS:-fromaddress@mydomain.com}
TOADDRESS=${TOADDRESS:-toaddress@receiversdomain.com}
## BEWARE the CC. It you don't want to set a default, just comment out the next line
CCADDRESS=${CCADDRESS:-ccaddress@ccreceiversdomain.com}
SUBJECT=${SUBJECT:-Test mail at `date`}
if [ -z $BODY ]
then
    read -r -d '' BODY << BODYDELIMITER
In a village of La Mancha, the name of which I have no desire to call
to mind, there lived not long since one of those gentlemen that keep
a lance in the lance-rack, an old buckler, a lean hack, and a greyhound
for coursing.

An olla of rather more beef than mutton, a salad on most nights, scraps
on Saturdays, lentils on Fridays, and a pigeon or so extra on Sundays,
made away with three-quarters of his income.
BODYDELIMITER
fi

bashmail "${FROMADDRESS}" "${TOADDRESS}" "${CCADDRESS}" "${SUBJECT}" "${BODY}"

## OPTION 2
## If you wish, just write the email below as shown
#bashmail "fromaddress@mydomain.com" "toaddress@receiversdomain.com" "ccaddress@ccreceiversdomain.com" "test mail at: `date`" "In a village of La Macha
#the name of which I have no desire to call to mind
#there lived not long since one of those gentlemen..."