Codesign (OSX): How to fix "unknown error -1009"?

Question

My already working command line call of codesign:

codesign -s <user> /path/to/app

has suddenly stopped working and outputs:

<app>: unknown error -1009=fffffffffffffc0f

What might cause this and how can this be fixed?

Answer 1

The DNS server was not properly configured, as the machine had been moved to another location. After fixing the network settings, it started working again.