Signing jar files with jarsigner
Most of the information in this note can be found in the `help' section of the jarsigner and keytool utilities:
Criteria for Signature Validity
The criteria of validity of a digital signature are the following:
- No modification of the archive resources after the signature,
- certificate not outdated (or not yet valid).
Moreover, the signer of the archive must be known, i.e. its public key certificate must be identified as trusted before the validation. Otherwise, any malicious third party can forge a similar certificate, potentially with the same signer name, and present a coherent signed archive.
Additional criteria of archive signature validity are defined in the context of the OSGi framework, that are specific to the deployment of components from third party repositories:
- No resource removed from the archive after the signature,
- No resource added from the archive after the signature,
- The digital signature must immediately follow the Manifest file of the archive, to prevent caching malicious files.
This means that according to the security level you need, the Sun criteria of signature validity may not be sufficient.