cgdconfig(8): Add support for generating shared-key parameters files.

Usage model:

- Generate a parameters file that supports sharing its main key:

cgdconfig -g -S -o /etc/cgd/wd0e -V gpt adiantu

cgdconfig(8): Add support for generating shared-key parameters files.

Usage model:

- Generate a parameters file that supports sharing its main key:

cgdconfig -g -S -o /etc/cgd/wd0e -V gpt adiantum

- Make another parameters file that uses the same shared main key but
derives an independent subkey from it:

cgdconfig -g -S -P /etc/cgd/wd0e -o /etc/cgd/ld1e \
-V disklabel aes-cbc 256

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cgdconfig(8): Add support for shared keys.

New clause `shared <id> algorithm <alg> subkey <info>' in a keygen
block enables `cgdconfig -C' to reuse a key between different params
files, so you can,

cgdconfig(8): Add support for shared keys.

New clause `shared <id> algorithm <alg> subkey <info>' in a keygen
block enables `cgdconfig -C' to reuse a key between different params
files, so you can, e.g., use a single password for multiple disks.
This is better than simply caching the password itself because:

- Hashing the password is expensive, so it should only be done once.

Suppose your budget is time t before you get bored, and you
calibrate password hash parameters to unlock n disks before you get
bored waiting for `cgdconfig -C'.

. With n password hashings the adversary's cost goes up only by a
factor of t/n.
. With one password hashing and n subkeys the adversary's cost goes
up by a factor of n.

And if you ever add a disk, rehashing it will make `cgdconfig -C'
go over budget, whereas another subkey adds negligible cost to you.

- Subkeys work for other types of keygen blocks, like shell_cmd,
which could be used to get a key from a hardware token that needs a
button press.

The <info> parameter must be different for each params file;
everything else in the keygen block must be the same. With this
clause, the keygen block determines a shared key used only to derive
keys; the actual key used by cgdconfig is derived from the shared key
by the specified algorithm.

The only supported algorithm is hkdf-hmac-sha256, which uses
HKDF-Expand of RFC 5869 instantiated with SHA-256.

Example:

algorithm aes-cbc;
iv-method encblkno1;
keylength 128;
verify_method none;
keygen pkcs5_pbkdf2/sha1 {
iterations 39361;
salt AAAAgMoHiYonye6KogdYJAobCHE=;
shared "pw" algorithm hkdf-hmac-sha256
subkey AAAAgFlw0BMQ5gY+haYkZ6JC+yY=;
};

The key used for this disk will be derived by

HKDF-HMAC-SHA256_k(WXDQExDmBj6FpiRnokL7Jg==),

where k is the outcome of PBKDF2-SHA1 with the given parameters.

Note that <info> encodes a four-byte prefix giving the big-endian
length in bits of the info argument to HKDF, just like all other bit
strings in cgdconfig parameters files.

If you have multiple disks configured using the same keygen block
except for the info parameter, `cgdconfig -C' will only prompt once
for your passphrase, generate a shared key k with PBKDF2 as usual,
and then reuse it for each of the disks.

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cgdconfig(8): Add an argon2id password-based key generation method

This provides an extra level of side-channel and cracking resistance
compared to the pre-existing pkcs5_pbkdf2/sha1 method used for

cgdconfig(8): Add an argon2id password-based key generation method

This provides an extra level of side-channel and cracking resistance
compared to the pre-existing pkcs5_pbkdf2/sha1 method used for
password-based disk encryption.

Several new keygen parameters are supported:

memory (integer, in kilobytes)
parallelism (integer, usually the number of CPU cores)
version (integer, usually 19...)

We do our best to calibrate these automatically when the paramsfile
is initially generated.

lgtm riastradh@

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Make adiantum a first class citizen

Avoid crash when no algorithm is specified in parameter file.

Add aes-xts to cgdconfig(8).

CID 1340063: fix TOCTOU

Don't chdir to the config directory; just form the parameters file with a
path if needed.

fix error messages containing \n

Add validation methods "mbr" and "gpt" for disks without a valid disklabel.

PR/39525: Joachim Schueth, Frederik Sausmikat:
cgd inadvertently encrypts blkno eight times to generate IV

Add a new keygen method which will execute an external command and
take its output as the key. I've been meaning to do this for quite
a while...

Remove clause 3 and 4 from TNF licenses

simplify and fix the combination code. Hi pooka.

3 month roland feedback timeout:
- Pass lint
- knf
- convert ints to size_t's

Use warn() and warnx().

crypt_defaults_lookup():
* Avoid comparison of int with unsigned.
* Simplified.

Remove more duplicate #includes,
from Slava Semushin <slava.semushin@gmail.com>

Programs that use efun.

Proper bounds check, found by Coverity, CID 1468.

- constify.
- don't dup extern declarations on each file because they end up being
inconsistent (yyerror).

Centralize error checking for malloc,calloc,strdup.

Fix comment. We're using microseconds not milliseconds.

Fix bits vs. bytes problem in call to calibration routine.

Add "urandomkey" key generation method as described in PR kern/22766;
useful for configuring a throwaway key for cgd-on-swap at boot time.