[bug#73955] [PATCH v2 1/2] services: wireguard: Make the private-key field optional.

[Richard Sent <richard@freakingpenguin.com>]

Users who retrieve the private-key via a PreUp field need to be able to
disable the default retrieval mechanism.

* gnu/services/vpn.scm (<wireguard-configuration>)[private-key]: Change
comment.
(wireguard-configuration-file): Conditionally serialize private-key.
* gnu/services/vpn.scm (wireguard-activation): Do not create private-key if
the field is #f.
* doc/guix.texi (VPN Services)[wireguard-configuration]: Document it.

Change-Id: Iac419809ae94eb76e97ff1f1749e2f4b3e65bb04
---
 doc/guix.texi        |  5 ++++-
 gnu/services/vpn.scm | 36 ++++++++++++++++++++----------------
 2 files changed, 24 insertions(+), 17 deletions(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index ac3a7adef0..5558bd7d44 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -34453,7 +34453,10 @@ VPN Services
 
 @item @code{private-key} (default: @code{"/etc/wireguard/private.key"})
 The private key file for the interface.  It is automatically generated
-if the file does not exist.
+if the file does not exist.  If this field is @code{#f}, a private key
+is not created and the path is not serialized to the configuration file.
+This allows for retrieving the private key programmatically with a PreUp
+command.
 
 @item @code{peers} (default: @code{'()})
 The authorized peers on this interface.  This is a list of
diff --git a/gnu/services/vpn.scm b/gnu/services/vpn.scm
index 7fb4775757..b62e0ac838 100644
--- a/gnu/services/vpn.scm
+++ b/gnu/services/vpn.scm
@@ -741,7 +741,7 @@ (define-record-type* <wireguard-configuration>
                       (default '("10.0.0.1/32")))
   (port               wireguard-configuration-port ;integer
                       (default 51820))
-  (private-key        wireguard-configuration-private-key ;string
+  (private-key        wireguard-configuration-private-key ;maybe-string
                       (default "/etc/wireguard/private.key"))
   (peers              wireguard-configuration-peers ;list of <wiregard-peer>
                       (default '()))
@@ -805,9 +805,12 @@ (define (wireguard-configuration-file config)
                     #$@(if (null? pre-up)
                            '()
                            (list (format #f "~{PreUp = ~a~%~}" pre-up)))
-                    (format #f "PostUp = ~a set %i private-key ~a\
-~{ peer ~a preshared-key ~a~}" #$(file-append wireguard "/bin/wg")
-#$private-key '#$peer-keys)
+                    (if #$private-key
+                        (format #f "PostUp = ~a set %i private-key ~a\
+~{ peer ~a preshared-key ~a~}"
+                                #$(file-append wireguard "/bin/wg")
+                                #$private-key '#$peer-keys)
+                        "")
                     #$@(if (null? post-up)
                            '()
                            (list (format #f "~{PostUp = ~a~%~}" post-up)))
@@ -838,18 +841,19 @@ (define (wireguard-activation config)
         (use-modules (guix build utils)
                      (ice-9 popen)
                      (ice-9 rdelim))
-        (mkdir-p (dirname #$private-key))
-        (unless (file-exists? #$private-key)
-          (let* ((pipe
-                  (open-input-pipe (string-append
-                                    #$(file-append wireguard "/bin/wg")
-                                    " genkey")))
-                 (key (read-line pipe)))
-            (call-with-output-file #$private-key
-              (lambda (port)
-                (display key port)))
-            (chmod #$private-key #o400)
-            (close-pipe pipe))))))
+        (when #$private-key
+          (mkdir-p (dirname #$private-key))
+          (unless (file-exists? #$private-key)
+            (let* ((pipe
+                    (open-input-pipe (string-append
+                                      #$(file-append wireguard "/bin/wg")
+                                      " genkey")))
+                   (key (read-line pipe)))
+              (call-with-output-file #$private-key
+                (lambda (port)
+                  (display key port)))
+              (chmod #$private-key #o400)
+              (close-pipe pipe)))))))
 
 ;;; XXX: Copied from (guix scripts pack), changing define to define*.
 (define-syntax-rule (define-with-source (variable args ...) body body* ...)
-- 
2.46.0