Requiring the user to input their password in order to unlock a device is not
always reasonable, so having an option to unlock the device using a key file
is a nice quality of life change.
* gnu/system/mapped-devices.scm (open-luks-device): Add #:key-file argument.
(luks-device-mapping-with-options): New procedure.
* doc/guix.texi (Mapped Devices): Describe the new procedure.
Change-Id: I1de4e045f8c2c11f9a94f1656e839c785b0c11c4
---
doc/guix.texi | 25 +++++++++++++
gnu/system/mapped-devices.scm | 67 ++++++++++++++++++++++-------------
2 files changed, 67 insertions(+), 25 deletions(-)
Toggle diff (160 lines)
diff --git a/doc/guix.texi b/doc/guix.texi
index 395545bed7..b1202f2182 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -123,6 +123,7 @@
Copyright @copyright{} 2023 Thomas Ieong@*
Copyright @copyright{} 2023 Saku Laesvuori@*
Copyright @copyright{} 2023 Graham James Addis@*
+Copyright @copyright{} 2023 Tomas Volf@*
Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.3 or
@@ -17992,6 +17993,30 @@ Mapped Devices
@code{dm-crypt} Linux kernel module.
@end defvar
+@deffn {Procedure} luks-device-mapping-with-options [#:key-file]
+Return a @code{luks-device-mapping} object, which defines LUKS block
+device encryption using the @command{cryptsetup} command from the
+package with the same name. It relies on the @code{dm-crypt} Linux
+kernel module.
+
+If @code{key-file} is provided, unlocking is first attempted using that
+key file. This has an advantage of not requiring a password entry, so
+it can be used (for example) to unlock RAID arrays automatically on
+boot. If key file unlock fails, password unlock is attempted as well.
+Key file is not stored in the store and needs to be available at the
+given location at the time of the unlock attempt.
+
+@lisp
+;; Following definition would be equivalent to running:
+;; cryptsetup open --key-file /crypto.key /dev/sdb1 data
+(mapped-device
+ (source "/dev/sdb1)
+ (target "data)
+ (type (luks-device-mapping-with-options
+ #:key-file "/crypto.key")))
+@end lisp
+@end deffn
+
@defvar raid-device-mapping
This defines a RAID device, which is assembled using the @code{mdadm}
command from the package with the same name. It requires a Linux kernel
diff --git a/gnu/system/mapped-devices.scm b/gnu/system/mapped-devices.scm
index e6b8970c12..c19a818453 100644
--- a/gnu/system/mapped-devices.scm
+++ b/gnu/system/mapped-devices.scm
@@ -2,6 +2,7 @@
;;; Copyright © 2014-2022 Ludovic Courtès <ludo@gnu.org>
;;; Copyright © 2016 Andreas Enge <andreas@enge.fr>
;;; Copyright © 2017, 2018 Mark H Weaver <mhw@netris.org>
+;;; Copyright © 2024 Tomas Volf <~@wolfsden.cz>
;;;
;;; This file is part of GNU Guix.
;;;
@@ -64,6 +65,7 @@ (define-module (gnu system mapped-devices)
check-device-initrd-modules ;XXX: needs a better place
luks-device-mapping
+ luks-device-mapping-with-options
raid-device-mapping
lvm-device-mapping))
@@ -188,7 +190,7 @@ (define (check-device-initrd-modules device linux-modules location)
;;; Common device mappings.
;;;
-(define (open-luks-device source targets)
+(define* (open-luks-device source targets #:key key-file)
"Return a gexp that maps SOURCE to TARGET as a LUKS device, using
'cryptsetup'."
(with-imported-modules (source-module-closure
@@ -198,7 +200,8 @@ (define (open-luks-device source targets)
((target)
#~(let ((source #$(if (uuid? source)
(uuid-bytevector source)
- source)))
+ source))
+ (keyfile #$key-file))
;; XXX: 'use-modules' should be at the top level.
(use-modules (rnrs bytevectors) ;bytevector?
((gnu build file-systems)
@@ -215,29 +218,35 @@ (define (open-luks-device source targets)
;; 'cryptsetup open' requires standard input to be a tty to allow
;; for interaction but shepherd sets standard input to /dev/null;
;; thus, explicitly request a tty.
- (zero? (system*/tty
- #$(file-append cryptsetup-static "/sbin/cryptsetup")
- "open" "--type" "luks"
-
- ;; Note: We cannot use the "UUID=source" syntax here
- ;; because 'cryptsetup' implements it by searching the
- ;; udev-populated /dev/disk/by-id directory but udev may
- ;; be unavailable at the time we run this.
- (if (bytevector? source)
- (or (let loop ((tries-left 10))
- (and (positive? tries-left)
- (or (find-partition-by-luks-uuid source)
- ;; If the underlying partition is
- ;; not found, try again after
- ;; waiting a second, up to ten
- ;; times. FIXME: This should be
- ;; dealt with in a more robust way.
- (begin (sleep 1)
- (loop (- tries-left 1))))))
- (error "LUKS partition not found" source))
- source)
-
- #$target)))))))
+ (let ((partition
+ ;; Note: We cannot use the "UUID=source" syntax here
+ ;; because 'cryptsetup' implements it by searching the
+ ;; udev-populated /dev/disk/by-id directory but udev may
+ ;; be unavailable at the time we run this.
+ (if (bytevector? source)
+ (or (let loop ((tries-left 10))
+ (and (positive? tries-left)
+ (or (find-partition-by-luks-uuid source)
+ ;; If the underlying partition is
+ ;; not found, try again after
+ ;; waiting a second, up to ten
+ ;; times. FIXME: This should be
+ ;; dealt with in a more robust way.
+ (begin (sleep 1)
+ (loop (- tries-left 1))))))
+ (error "LUKS partition not found" source))
+ source)))
+ ;; We want to fallback to the password unlock if the keyfile fails.
+ (or (and keyfile
+ (zero? (system*/tty
+ #$(file-append cryptsetup-static "/sbin/cryptsetup")
+ "open" "--type" "luks"
+ "--key-file" keyfile
+ partition #$target)))
+ (zero? (system*/tty
+ #$(file-append cryptsetup-static "/sbin/cryptsetup")
+ "open" "--type" "luks"
+ partition #$target)))))))))
(define (close-luks-device source targets)
"Return a gexp that closes TARGET, a LUKS device."
@@ -276,6 +285,14 @@ (define luks-device-mapping
(close close-luks-device)
(check check-luks-device)))
+(define* (luks-device-mapping-with-options #:key key-file)
+ "Return a luks-device-mapping object with open modified to pass the arguments
+into the open-luks-device procedure."
+ (mapped-device-kind
+ (inherit luks-device-mapping)
+ (open (λ (source targets) (open-luks-device source targets
+ #:key-file key-file)))))
+
(define (open-raid-device sources targets)
"Return a gexp that assembles SOURCES (a list of devices) to the RAID device
TARGET (e.g., \"/dev/md0\"), using 'mdadm'."
base-commit: 5c0f77f4241c9beac0c82deae946bfdc70b49ff0
--
2.41.0
