rsa2azure: convert ssh key to public key suitable for azure

rsa2azure

#!/bin/sh
# vi: ts=4 noexpandtab
# rsa2azure

Usage() {
   cat <<EOF
Usage: ${0##*/} [options] [private-key]
   convert private-key in ssh private key format to the format
   needed by windows azure as described at
      http://utlemming.azurewebsites.net/?p=91

   options:
    -o | --output FILE    write output to F. default stdout.

   Default private-key is ~/.ssh/id_rsa)
EOF
}
fail() { echo "$@" 1>&2; exit 1; }

short_opts="ho:"
long_opts="output:,help"
getopt_out=$(getopt --name "${0##*/}" \
	--options "ho:" --long "output:,help" -- "$@") &&
	eval set -- "${getopt_out}" ||
	{ Usage 1>&2; fail "bad usage"; }

umask 066

outfile=/dev/stdout
echo $@
while [ $# -ne 0 ]; do
	case "$1" in
		-h|--help) Usage; exit 0;;
		-o|--output) outfile=${2}; shift;;
		   --) shift; break;;
	esac
	shift;
done

[ $# -eq 0 -o $# -eq 1 ] || { Usage 1>&2; exit 1; }

key_in=$1
if [ $# -eq 0 ]; then
	key_in=~/.ssh/id_rsa
	[ -f "$key_in" ] || fail "no default key found in $key_in";
fi

[ "$key_in" = "-" ] && key_in=/dev/stdin
[ -f "$key_in" ] || fail "${key_in}: not a file"

out=$(openssl rsa -in "$key_in" -out /dev/stdout 2>/dev/null) ||
	fail "failed to decrypt private key in $key_in"
printf "%s" "$out" |
	openssl req -new -x509 -nodes -days 999 -batch -outform DER -batch \
		-key /dev/stdin -out "${outfile}" 2>/dev/null