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zkey-cryptsetup: Use PBKDF2 as default PBKDF for new key slots

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LUKS2 encrypted volumes use Argon2i as default password based key
derivation function (PBKDF). Argon2i is a so-called memory-hard
function. It requires a certain amount of physical memory to make
dictionary attacks more costly.

Unfortunately, when multiple encrypted volumes are unlocked
automatically during system startup via /etc/crypttab, the use of
Argon2i will most likely cause an out-of-memory error in systemd.

To avoid the out-of-memory error, use PBKDF2 instead. Because PAES
uses secure keys as volume keys, the security of the key derivation
function used to derive the key to encrypt the volume key in the LUKS
key slots is of less relevance. Thus it is safe to use a weaker key
derivation function.

Signed-off-by: Ingo Franzki <ifranzki@linux.ibm.com>
Reviewed-by: Harald Freudenberger <freude@linux.ibm.com>
Signed-off-by: Jan Höppner <hoeppner@linux.ibm.com>
This commit is contained in:
Ingo Franzki
2019-02-04 14:35:58 +01:00
committed by Jan Höppner
parent b26dbfe832
commit a69470d7e0
2 changed files with 40 additions and 4 deletions
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28
zkey/zkey-cryptsetup.1
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@@ -180,6 +180,20 @@ and
to control which part of the key file is used as passphrase. These options
behave in the same way as with \fBcryptsetup\fP.
.PP
The
.B reencipher
command creates a new key slot with the re-enciphered secure AES volume key.
The new key slot uses
.B PBKDF2
as password based key derivation function. LUKS2 volumes typically default to
.B Argon2i
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.
.PP
.B Note:
The \fBreencipher\fP command requires the CCA host library (libcsulcca.so)
to be installed. For the supported environments and downloads, see:
@@ -288,6 +302,20 @@ and
.B \-\-keyfile\-size
to control which part of the key file is used as passphrase. These options
behave in the same way the same as with \fBcryptsetup\fP.
.PP
The
.B setkey
command creates a new key slot with the re-enciphered secure AES volume key.
The new key slot uses
.B PBKDF2
as password based key derivation function. LUKS2 volumes typically default to
.B Argon2i
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.
.
.
.