Sunday, February 22, 2015

Importing the New RDS CA Certificate Into the Java Keytool

A few days ago (Feb 2015), Amazon released a new CA certificate bundle (rds-combined-ca-bundle.pem) for use with AWS RDS databases. In order to connect with a MySQL, PostgreSQL, or SQL Server DB over SSL, your client app has to trust the certificates in this bundle. For java apps (using JDBC) this generally requires importing the certs into your java keystore via the java keytool utility.

The first RDS cert (from 2010) was released as a single certificate in a single file; but this new release is actually 10 separate new certificates (plus the old certificate) jammed into the same file. The java keytool, however, supports importing only one certificate at a time — so you have to first split up the bundle into individual certificates, and then import the certs one by one. If you try to import the whole bundle as a single file, you'll end up trusting only the first cert listed in that file (which happens, in this case, to be the old cert).

I wrote up a quick shell script that 1) downloads the new CA bundle, 2) splits up the bundle into individial certificate files, and 3) imports each file separately into the java keytool. It assumes that you already have the keytool installed and on your path; that the keystore location is /etc/ssl/certs/java/cacerts and the password is changeit (the defaults for the OpenJDK on Ubuntu); that you're running the script as a sudoer; and that you have OpenSSL installed. You'll have to tweak those things if that's not the case:

#!/bin/sh -e

# create a temp dir in which to work
mkdir /tmp/rds-ca && cd /tmp/rds-ca

# download the bundle
# split the bundle into individual certs (prefixed with xx)
csplit -sz rds-combined-ca-bundle.pem '/-BEGIN CERTIFICATE-/' '{*}'

# import each cert individually
for CERT in xx*; do
    # extract a human-readable alias from the cert
    ALIAS=$(openssl x509 -noout -text -in $CERT |
        perl -ne 'next unless /Subject:/; s/.*CN=//; print')
    echo "importing $ALIAS"
    # import the cert into the default java keystore
    sudo keytool -import \
        -keystore /etc/ssl/certs/java/cacerts \
        -storepass changeit -noprompt \
        -alias "$ALIAS" -file $CERT

# back out of the temp dir and delete it
cd "$OLDDIR"
rm -r /tmp/rds-ca

# list the imported rds certs as a sanity check
keytool -list \
    -keystore /etc/ssl/certs/java/cacerts \
    -storepass changeit -noprompt |
    grep -i rds

OpenSSL, in particular, is used by the script only to extract a convenient, unique alias for each certificate; so if you don't have OpenSSL installed, you could replace the alias-creating line with something like this (which will create aliases in the form of rdsxx00, rdsxx01, etc):