ukhomeoffice / csca-checker

CSCA Checker

Service to check MRTD document signing certificates for trust against a master list of Country-signing CAs.

Building

Requires JDK 8+

./gradlew clean test

Running

See the bootrun block in build.gradle for how to specify the location of the masterlist keystore.

./gradlew bootRun

Example Masterlist

The German government produces a masterlist which can be downloaded (along with the certificates used to sign the list) from their website.

Parsing the CSCA masterlist

The CSCA masterlists are received as a CMS message, signed by a particular certificate. The list first needs to be extracted from the CMS wrapper with openSSL, and then split up into its constituent certificates before importing into a Java keystore. We also need to check the message signature, and that we trust the certificate used to sign the message.

Splitting up the extracted message is relatively simple: it's a binary file, which lists the certificates one after the other. openssl asn1parse can be used to get the offsets and lengths for each, see the example script. This script also converts from DER to PEM format.

Some of the certificates use EC cryptography without specifying the curve name. This is not supported by the Oracle JDK provider, so BouncyCastle must be used instead. To use this with keytool add the jar to the lib/ext directory of the JDK, and add the BouncyCastle provider as the first provider in java.security

A second verification step is needed to verify the certificate that is used to sign the CMS message. This certificate should be checked against a predetermined CA certificate from a trusted origin, using openssl verify. Alternatively, we can check that we trust the signing certificate directly.