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zkey: use default benchmarked Argon2i with LUKS2.

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cryptsetup 2.1.0 requires excessive amount of RAM (1GB) to luksOpen encrypted
drives (LP: #1820049).
LUKS2 introduced support for Argon2i and Argon2id as a Password-Based Key
Derivation Function (PBKDF).
Argon2 is the winner of Password Hashing Competition and is now officially
recommended by RFC 9106.
PBKDF2 is currently used in zkey to mitigate out-of-memory errors when
multiple LUKS2 volumes are opened automatically via /etc/crypttab.

This patch is to use Argon2i (the deflaut algorithm) as key derivation function
for LUKS2 volumes, but with options for low memory and time requirements.
Using the default Argon2i options might still cause out-of-memory errors.

Link: https://bugs.launchpad.net/ubuntu/+source/cryptsetup/+bug/1820049
Closes: https://github.com/ibm-s390-linux/s390-tools/pull/138
Signed-off-by: Frank Heimes <frank.heimes@canonical.com>
Acked-by: Ingo Franzki ifranzki@linux.ibm.com
[hoeppner@linux.ibm.com: fix whitespace, line break, and commit message]
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
This commit is contained in:
Frank Heimes
2022-06-15 12:18:37 +02:00
committed by Jan Höppner
parent e9d0e267c5
commit 51b9504720
2 changed files with 13 additions and 12 deletions
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12
zkey/keystore.c
View File

@@ -4312,15 +4312,17 @@ static int _keystore_process_cryptsetup(struct keystore *keystore,
}
} else {
/*
* Use PBKDF2 as key derivation function for LUKS2
* volumes. LUKS2 uses Argon2i as default, but this
* might cause out-of-memory errors when multiple LUKS2
* volumes are opened automatically via /etc/crypttab
* Use Argon2i as key derivation function for LUKS2
* volumes, but with options for low memory and time requirements.
* Using the default Argon2i options might cause out-of-memory
* errors when multiple LUKS2 volumes are opened automatically
* via /etc/crypttab
*/
util_asprintf(&cmd,
"cryptsetup luksFormat %s%s--type luks2 "
"--master-key-file '%s' --key-size %lu "
"--cipher %s --pbkdf pbkdf2 %s%s%s",
"--cipher %s --pbkdf argon2i --pbkdf-memory 32 "
"--pbkdf-force-iterations 4 %s%s%s",
info->batch_mode ? "-q " : "",
keystore->verbose ? "-v " : "",
key_file_name, key_file_size * 8,

13
zkey/zkey.1
View File

@@ -734,13 +734,12 @@ type, this is the default. If specified for the plain volume type, then no
command is generated.
.P
For LUKS2 volumes, the generated \fBcryptsetup luksFormat\fP contains
option \fB\-\-pbkdf pbkdf2\fP to set \fBPBKDF2\fP as password based key
derivation function. LUKS2 volumes typically default to \fBArgon2i\fP as
password based key derivation function, but this might cause out-of-memory
errors when multiple encrypted volumes are unlocked automatically at boot
through /etc/crypttab. Because PAES uses secure AES keys as volume keys, the
security of the key derivation function used to encrypt the volume key in the
LUKS key slots is of less relevance.
options \fB-\-pbkdf argon2i \-\-pbkdf\-memory 32 \-\-pbkdf\-force\-iterations 4
\fP for low memory and time requirements. Using the default \fBArgon2i\fP
options might cause out-of-memory errors when multiple encrypted volumes are
unlocked automatically at boot through /etc/crypttab. Because PAES uses secure
AES keys as volume keys, the security of the key derivation function used to encrypt
the volume key in the LUKS key slots is of less relevance.
.P
For LUKS2 volumes, a passphrase is required. You are prompted for the
passphrase when running the generated commands, unless option