This chapter describes IPS package signing and how developers and quality assurance organizations can sign either new packages or existing, already signed packages.
The ability to validate that the software installed on the system is actually as originally specified by the publisher is an important feature of IPS. This ability to validate the installed system is key for both the user and the support engineering staff.
In addition to validation, signatures can also be used to indicate approval by other organizations or parties. For example, the internal QA organization could sign manifests of packages once the packages are qualified for production use. Such approvals could be required for installation.
Packages can be signed multiple times, to indicate approval at multiple levels. Signing a package adds a signature action to the manifest but does not alter the package in any other way. Signing a package does not remove or invalidate previous signatures.
Signature policies can be set for the image or for specific publishers. Policies include ignoring signatures, verifying existing signatures, requiring signatures, and requiring specific common names in the chain of trust.