accounts: Add /etc/subuid and /etc/subgid support.

This commit adds a new record type, <subid-entry> and serializers
and deserializers for it in (gnu build accounts).  Each instance of this
record represents one line in either /etc/subuid or /etc/subgid.  Since
Shadow uses the same representation for both files, it should be ok if
we do it as well.

This commit adds also <subid-range>, a user facing representation of
<subid-entry>. It is supposed to be usable directly in OS configurations.

* gnu/build/accounts.scm (subid-entry): New record;
(write-subgid): add serializer for subgids;
(write-subuid): add serializer for subuids;
(read-subgid): add serializer for subgids;
(read-subuid): add serializer for subuids.
* gnu/system/accounts.scm (subid-range): New record.
* test/accounts.scm: Test them.

Change-Id: I6b037e40e354c069bf556412bb5b626bd3ea1b2c
Signed-off-by: Giacomo Leidi <goodoldpaul@autistici.org>
Signed-off-by: Ludovic Courtès <ludo@gnu.org>

1 files changed, 17 insertions, 0 deletions

diff --git a/gnu/system/accounts.scm b/gnu/system/accounts.scm
index 586cff1842e..9a006c188db 100644
--- a/gnu/system/accounts.scm
+++ b/gnu/system/accounts.scm
@@ -1,5 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2018, 2019 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2024 Giacomo Leidi <goodoldpaul@autistici.org>
 ;;;
 ;;; This file is part of GNU Guix.
 ;;;
@@ -39,6 +40,12 @@
             user-group-id
             user-group-system?
 
+            subid-range
+            subid-range?
+            subid-range-name
+            subid-range-start
+            subid-range-count
+
             sexp->user-account
             sexp->user-group
 
@@ -85,6 +92,16 @@
   (system?        user-group-system?              ; Boolean
                   (default #f)))
 
+(define-record-type* <subid-range>
+  subid-range make-subid-range
+  subid-range?
+  (name           subid-range-name)
+  (start          subid-range-start (default #f))    ; number
+  (count          subid-range-count                  ; number
+                  ; from find_new_sub_gids.c and
+                  ; find_new_sub_uids.c
+                  (default 65536)))
+
 (define (default-home-directory account)
   "Return the default home directory for ACCOUNT."
   (string-append "/home/" (user-account-name account)))