Copy head@r302406 to stable/11 as part of the 11.0-RELEASE cycle.
Prune svn:mergeinfo from the new branch, as nothing has been merged
here.

Additional commits post-branch will follow.

Approved by: re (implicit)
Sponsored by: The FreeBSD Foundation

I just realized that the previous commit message makes no sense: the
first sentence should have read "Constify the AES and SHA-256 code and
wrappers". This allows us to feed zero_region (which is const) to the
hash function during reseeding and thereby implement the FS&K version of
SHAd-256 instead of the older F&S version.

Approved by: so (self)

Constify the AES code and propagate to consumers. This allows us to
update the Fortuna code to use SHAd-256 as defined in FS&K.

Approved by: so (self)

Interior decoration changes.

Optimize the size of the work-items by letting the mapping function
decide the largest size which stays inside the zone and does not
collide with a lock sector.

Run a revision on the GBDE encryption facility.

Replace ARC4 with SHA2-512.
Change lock-structure encoding to use random ordering rather for obscurity.
Encrypt lock-structure with AES/256 instead of AES/128.
Change kkey derivation to be MD5 hash based.
Watch for malloc(M_NOWAIT) failures and ditch our cache when they happen.
Remove clause 3 of the license with NAI Labs consent.

Many thanks to "Lucky Green" <shamrock@cypherpunks.to> and "David
Wagner" <daw@cs.berkeley.edu>, for code reading, inputs and
suggestions.

This code has still not been stared at for 10 years by a gang of
hard-core cryptographers. Discretion advised.

NB: These changes result in the on-disk format changing: dump/restore needed.

Sponsored by: DARPA & NAI Labs.

Change the kkey generation cherry-picker to use MD5.

Sponsored by: DARPA & NAI Labs

Constify input to the arc4 seed function.
Implement the lockfile hunting in sector zero.

Sponsored by: DARPA & NAI Labs.

Add Geom Based Disk Encryption to the tree.

This is an encryption module designed for to secure denial of access
to the contents of "cold disks" with or without destruction activation.

Major features:

* Based on AES, MD5 and ARC4 algorithms.
* Four cryptographic barriers:
1) Pass-phrase encrypts the master key.
2) Pass-phrase + Lock data locates master key.
3) 128 bit key derived from 2048 bit master key protects sector key.
3) 128 bit random single-use sector keys protect data payload.
* Up to four different changeable pass-phrases.
* Blackening feature for provable destruction of master key material.
* Isotropic disk contents offers no information about sector contents.
* Configurable destination sector range allows steganographic deployment.

This commit adds the kernel part, separate commits will follow for the
userland utility and documentation.

This software was developed for the FreeBSD Project by Poul-Henning Kamp and
NAI Labs, the Security Research Division of Network Associates, Inc. under
DARPA/SPAWAR contract N66001-01-C-8035 ("CBOSS"), as part of the DARPA CHATS
research program.

Many thanks to Robert Watson, CBOSS Principal Investigator for making this
possible.

Sponsored by: DARPA & NAI Labs.