Tuesday, April 5, 2011

A dead simple certificate authority for testing purposes

I don't know about you, but I know I'd rather spend an hour writing a script to automate something than 30 minutes figuring out how to use an existing but annoying/terrible tool. I do that not because I am a glutton for punishment, but because I know I'll have to use that terrible tool again in the future and I won't remember how to use it anyway.

So when I needed certificates for a test environment I checked out OpenSSL's built in CA tool, quickly decided against using it, and then wrote my own simpler tool.


Update: There's a new version of this script available in a new post

To use:

  1. make a directory to contain the script and the keys and certs it will generate
  2. copy/paste this code into a file in that directory. I called it make-cert, but use whatever name you like
  3. run it

The script takes one or more parameters that specify the CN of the cert you want it to generate. So

$ ./make-cert myserver.mydomain.com
will make a cert for myserver.mydomain.com. It will also take more than one CN on the command line, so
$ ./make-cert myserver.mydomain.com login.mydomain.com
will make a certificate for myserver.mydomain.com and another one for login.mydomain.com.

NOTE: There's a new version of this script available in a new post

And here's the code


# a very, very simple cert authority
# Copyright 2011 Oracle
# christopher.johnson@oracle.com

# License agreement:
# ------------------
# This script is intended as a simple sample and/or for my own
# purposes. If you get any benefit from it then that's GREAT but
# there are NO warranties and NO support. If this script burns down
# your house, chases your dog away and spoils your milk please don't
# come crying to me.

baseAnswers() {
    echo US
    echo Massachusetts
    echo Boston
    echo Oracle
    echo A-Team
    echo $1
    echo root@`hostname`

answers() {
    baseAnswers $1
    echo ''
    echo ''

# better safe than sorry
umask 077

# these next two lines figure out where the script is on disk
SCRIPTPATH=`readlink -f $0`
SCRIPTDIR=`dirname $0`

# if you're running this from somewhere else...
if [  $SCRIPTDIR != "."    -a   $SCRIPTDIR != $PWD  ]; then
    # then CD to that directory
    echo "Certificate and key files (.crt and .key) will be placed in $PWD"

if [ ! -e ca.crt -o ! -e ca.key ]; then
    echo "Creating cert authority key & certificate"
    baseAnswers "My Cert Authority" | openssl req -newkey rsa:1024 -keyout ca.key -nodes -x509 -days 365 -out ca.crt 2> /dev/null

if [ $# -eq 0 ] ; then
    echo "This script creates one or more certificates."
    echo "Provide one or more certificate CNs on the command line."
    echo "Usage: `basename $0`  [certcn [...]]"
    exit -1

for certCN in $@ ; do
    echo Certificate for CN \"$certCN\"
    echo =============================================


    if [ -e $KEY ] ; then
 echo " ERROR: Key file $KEY already exists"
    if [ -e $REQ ] ; then
 echo " ERROR: Request file $REQ already exists"
    if [ -e $CRT ] ; then
 echo " ERROR: Certificate file $CRT already exists"
    if [ $ABORT -eq 1 ] ; then
 echo ''
 echo "If you wish to recreate a certificate for you must delete"
 echo "any preexisting files for that CN before running this script."
 echo ''
 echo ''
 answers $certCN | openssl req -newkey rsa:1024 -keyout $KEY -nodes -days 365 -out $REQ  2> /dev/null
        # at this point we have a key file, but the cert is not signed by the CA
 openssl x509 -req -in $REQ -out $CRT -CA ca.crt -CAkey ca.key -CAcreateserial -CAserial ca.serial 2> /dev/null

 echo "Certificate created."
 ls -l $KEY $REQ $CRT
 echo 'Certificate information:'
 openssl x509 -in $CRT -noout -issuer -subject -serial

Note: an earlier version of this script was missing a $1 in the answers() function. The above script contains the correction.

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