The volume key structure may often be in configuration
where 'key' member does not contain real data. Some
examples:
- volume key acquired by querring device-mapper where key
was originaly passed by kernel keyring reference.
- volume key allocated by crypt_alloc_volume_key(size, NULL)
With this patch access to internal 'uninitialized' data result
in failed assert().
For use cases where key data are not needed (keyring reference wrapper,
key length info only) we do not have to allocate and lock the safe
buffer in memory.
Further improvements might to completely hide the volume key internals
and access only via setter and getter functions.
Switch current code to use following volume key helpers
for accessing internal properties:
crypt_volume_key_length(), crypt_volume_key_get_key(),
crypt_volume_key_description() and crypt_volume_key_kernel_key_type()
Remaining direct access to volume key internals will be dealt with in
later commits since it requires some further changes.
This patch switches code to SPDX one-line license identifiers according to
https://spdx.dev/learn/handling-license-info/
and replacing long license text headers.
I used C++ format on the first line in style
// SPDX-License-Identifier: <id>
except exported libcryptsetup.h, when only C comments are used.
The only additional changes are:
- switch backend utf8.c from LGPL2+ to LGPL2.1+ (as in systemd)
- add some additional formatting lines.
We already support activation of a device using a volume key in keyring.
However, in case of multi-key devices (i.e. device with reencryption
running) we need to supply two volume keys.
Adds support for LUKS2 decryption of devices with a
header put in the head of data device. During the initialization
header is exported to a file and first data segment
is moved to head of data device in place of original header.
The feature introduces several new resilience modes (combination
of existing modes datashift and "checksum" or "journal").
Where datashift resilience mode is applied for data moved towards
the first segment and first segment is decrypted in-place.
The mode is not backward compatible with prior LUKS2 reencryption
and therefor interrupted operation in progress can not be resumed
using older cryptsetup releases.
Fixes: #669.
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.
