To ensure the security of your metadata refresh process, you must verify the XML signature on each and every metadata aggregate you consume. To do that, you need an authentic copy of the metadata signing certificate, that is, the certificate that contains the public key corresponding to the private InCommon metadata signing key. The certificate must be obtained securely since all subsequent operations depend on it.
To obtain an authentic copy of the metadata signing certificate, perform the following steps:
- Download a copy of the metadata signing certificate via a secure channel
- Compute the SHA-1 and SHA-256 fingerprints of the metadata signing certificate
- Compare the computed fingerprints to the actual fingerprints
The latter two steps guarantee the integrity of the metadata signing certificate.
Check the integrity of the metadata signing certificate!
To bootstrap your trusted metadata process, you MUST check the integrity of the metadata signing certificate configured into that process. It is not sufficient to fetch the certificate via a TLS-protected HTTPS connection.
You may check the integrity of the downloaded certificate in a variety of ways. For example, on a GNU/Linux system, you could use
openssl to check the integrity of the metadata signing certificate as follows:
The third and final step is to compare the computed fingerprints to the actual fingerprints. The latter are obtained by clicking this link:
If the computed fingerprints match the actual fingerprints, you are done. You may now use the certificate to verify the signature on the metadata file.