Setup your own mail paste service

Last modification on

How it works

  • The user sends a mail with an attachment to a certain mail address, for example: paste@somehost.org
  • The mail daemon configuration has an mail alias to pipe the raw mail to a shellscript.
  • This shellscript processes the raw mail contents from stdin.

What it does

  • Process a mail with the attachments automatically.
  • The script processes the attachments in the mail and stores them.
  • It will mail (back) the URL where the file(s) are stored.

This script is tested on OpenBSD using OpenBSD smtpd and OpenBSD httpd and the gopher daemon geomyidae.

Install dependencies

On OpenBSD:

pkg_add mblaze

smtpd mail configuration

In your mail aliases (for example /etc/mail/aliases) put:

paste: |/usr/local/bin/paste-mail

This pipes the mail to the script paste-mail for processing, this script is described below. Copy the below contents in /usr/local/bin/paste-mail

Script:

#!/bin/sh

d="/home/www/domains/www.codemadness.org/htdocs/mailpaste"
tmpmsg=$(mktemp)
tmpmail=$(mktemp)

cleanup() {
	rm -f "$tmpmail" "$tmpmsg"
}

# store whole mail from stdin temporarily, on exit remove temporary file.
trap "cleanup" EXIT
cat > "$tmpmail"

# mblaze: don't store mail sequence.
MAILSEQ=/dev/null
export MAILSEQ

# get from address (without display name).
from=$(maddr -a -h 'From' /dev/stdin < "$tmpmail")

# check if allowed or not.
case "$from" in
"hiltjo@codemadness.org")
	;;
*)
	exit 0;;
esac

# prevent mail loop.
if printf '%s' "$from" | grep -q "paste@"; then
	exit 0
fi

echo "Thank you for using the enterprise paste service." > "$tmpmsg"
echo "" >> "$tmpmsg"
echo "Your file(s) are available at:" >> "$tmpmsg"
echo "" >> "$tmpmsg"

# process each attachment.
mshow -n -q -t /dev/stdin < "$tmpmail" | sed -nE 's@.*name="(.*)".*@\1@p' | while read -r name; do
	test "$name" = "" && continue

	# extract attachment.
	tmpfile=$(mktemp -p "$d" XXXXXXXXXXXX)
	mshow -n -O /dev/stdin "$name" < "$tmpmail" > "$tmpfile"

	# use file extension.
	ext="${name##*/}"
	case "$ext" in
	*.tar.*)
		# special case: support .tar.gz, tar.bz2, etc.
		ext="tar.${ext##*.}";;
	*.*)
		ext="${ext##*.}";;
	*)
		ext="";;
	esac
	ext="${ext%%*.}"

	# use file extension if it is set.
	outputfile="$tmpfile"
	if test "$ext" != ""; then
		outputfile="$tmpfile.$ext"
	fi
	mv "$tmpfile" "$outputfile"
	b=$(basename "$outputfile")

	chmod 666 "$outputfile"
	url="gopher://codemadness.org/9/mailpaste/$b"

	echo "$name:" >> "$tmpmsg"
	echo "	Text   file: gopher://codemadness.org/0/mailpaste/$b" >> "$tmpmsg"
	echo "	Image  file: gopher://codemadness.org/I/mailpaste/$b" >> "$tmpmsg"
	echo "	Binary file: gopher://codemadness.org/9/mailpaste/$b" >> "$tmpmsg"
	echo "" >> "$tmpmsg"
done

echo "" >> "$tmpmsg"
echo "Sincerely," >> "$tmpmsg"
echo "Your friendly paste_bot" >> "$tmpmsg"

# mail back the user.
mail -r "$from" -s "Your files" "$from" < "$tmpmsg"

cleanup

The mail daemon processing the mail needs of course to be able to have permissions to write to the specified directory. The user who received the mail needs to be able to read it from a location they can access and have permissions for it also.

Room for improvements

This is just an example script. There is room for many improvements. Feel free to change it in any way you like.

References

Bye bye

I hope this enterprise(tm) mail service is inspirational or something ;)