The strategy of hex encoding a random byte array only uses the
following characters:
0123456789abcdef
Instead of the entire bootstrapping token character set:
0123456789abcdefghijklmnopqrstuvwxyz
Update the token generation to use the entire character set. This
increases the token secret from 48 bits of entropy to ~82 bits.
256^8 (1.8e+19) vs. 36^16 (7.9e+24).
- Factor out token constants to kubeadmconstants.
- Move cmd/kubeadm/app/util/{,token/}tokens.go
- Use the token-id, token-secret, etc constants provided by the bootstrapapi package
- Move cmd/kubeadm/app/master/tokens.go to cmd/kubeadm/app/phases/token/csv.go
This refactor basically makes it possible to hook up kubeadm to the BootstrapSigner controller later on
