crypt_reencrypt_status() returns this flag if old
online-reencrypt requirement is detected and reencryption
keyslot digest is missing.
crypt_reencrypt_init_by_passphrase() with same flag applied
repairs (upgrade) reencryption metadata so that
automatic reencryption recovery during activation
is again possible and reencryption operation can be resumed
post CVE-2021-4122 fix.
Fix possible attacks against data confidentiality through LUKS2 online
reencryption extension crash recovery.
An attacker can modify on-disk metadata to simulate decryption in
progress with crashed (unfinished) reencryption step and persistently
decrypt part of the LUKS device.
This attack requires repeated physical access to the LUKS device but
no knowledge of user passphrases.
The decryption step is performed after a valid user activates
the device with a correct passphrase and modified metadata.
There are no visible warnings for the user that such recovery happened
(except using the luksDump command). The attack can also be reversed
afterward (simulating crashed encryption from a plaintext) with
possible modification of revealed plaintext.
The problem was caused by reusing a mechanism designed for actual
reencryption operation without reassessing the security impact for new
encryption and decryption operations. While the reencryption requires
calculating and verifying both key digests, no digest was needed to
initiate decryption recovery if the destination is plaintext (no
encryption key). Also, some metadata (like encryption cipher) is not
protected, and an attacker could change it. Note that LUKS2 protects
visible metadata only when a random change occurs. It does not protect
against intentional modification but such modification must not cause
a violation of data confidentiality.
The fix introduces additional digest protection of reencryption
metadata. The digest is calculated from known keys and critical
reencryption metadata. Now an attacker cannot create correct metadata
digest without knowledge of a passphrase for used keyslots.
For more details, see LUKS2 On-Disk Format Specification version 1.1.0.
Right now, cryptsetup makes an attempt to include the correct
definitions in all of its header files, allowing the headers to
compile regardless of the context in which they are included.
A few files were missed, this change fixes them by adding the minimal
set of #includes needed to get them to compile.
Signed-off-by: Joe Richey <joerichey@google.com>
When creating LUKS2 header with specified --offset much larger
then LUKS2 header size we needlessly also wipe (allocate up to
--offset) much larger file than needed.
Currently hard memory limit is 1 GiB. Soft limit is
1/4 of system memory.
Note that --hotzone-size cryptsetup parameter can only further
lower hard and soft memory limit on hotzone size and not bypass
it.
- Remove all 'LUKS2_' name prefixes from internal routines
- Make all internal routines prefixed with 'reencrypt_' instead
- Drop few static routines by refactoring
- Rename all variables and routines containing 'pre' prefix to
contain 'hot' prefix instead (when referring to segments
undergoing reencryption)
- Rename all variables and routines containing 'after' prefix to
contain 'post' prefix instead
- Rename all routines prefixed with '_' to 'reencrypt_' instead
It's useful to reencrypt only initial device part only.
For example with golden image reencryption it may be useful
to reencrypt only first X bytes of device because we know
the rest of device is empty.
If passed key matches any existing digest we will not create
new digest but assign the keyslot to already existing one.
Because reencryption should be able to create more than one
keyslot assigned to new key digest.
TODO: Tests for the new feature
