[bug#47013] [PATCH] gnu: Harden filesystem links.

[Leo Famulari <leo@famulari.name>]

[-- Attachment #1.1: Type: text/plain, Size: 122 bytes --]

Here is an updated patch that can be composed with other
sysctl-service-types that the user may have added to config.scm.

[-- Attachment #1.2: 0001-system-Harden-filesystem-links.patch --]
[-- Type: text/plain, Size: 2209 bytes --]

From 1e3bd831899a4ec9dfa7199a381421adbfe0dcf7 Mon Sep 17 00:00:00 2001
From: Leo Famulari <leo@famulari.name>
Date: Fri, 12 Mar 2021 17:03:26 -0500
Subject: [PATCH] system: Harden filesystem links.

These sysctl options are enabled on most GNU/Linux distros, including
Debian, Fedora, NixOS, and OpenSUSE.

I've tested this patch on Guix System for several weeks, and it doesn't
appear to break anything. Plus, we know that Guix works on other distros
that enable these restrictions.

References:

https://sysctl-explorer.net/fs/protected_hardlinks/
https://sysctl-explorer.net/fs/protected_symlinks/

* gnu/services/base.scm (default-sysctl-settings): New variable.
(%base-services): Add default-sysctl-settings.
---
 gnu/services/base.scm | 10 ++++++++++
 1 file changed, 10 insertions(+)

diff --git a/gnu/services/base.scm b/gnu/services/base.scm
index f6a490f712..64aac36401 100644
--- a/gnu/services/base.scm
+++ b/gnu/services/base.scm
@@ -35,6 +35,7 @@
   #:use-module (gnu services)
   #:use-module (gnu services admin)
   #:use-module (gnu services shepherd)
+  #:use-module (gnu services sysctl)
   #:use-module (gnu system pam)
   #:use-module (gnu system shadow)                ; 'user-account', etc.
   #:use-module (gnu system uuid)
@@ -2484,6 +2485,11 @@ to handle."
                                            (requirement requirement)
                                            (name-servers name-servers)))))
 
+(define (default-sysctl-settings default-settings)
+  (simple-service 'base-sysctl-settings
+                  sysctl-service-type
+                  default-settings))
+
 \f
 (define %base-services
   ;; Convenience variable holding the basic services.
@@ -2532,6 +2538,10 @@ to handle."
                  (udev-configuration
                    (rules (list lvm2 fuse alsa-utils crda))))
 
+        (default-sysctl-settings
+          '(("fs.protected_hardlinks" . "1")
+            ("fs.protected_symlinks" . "1")))
+
         (service special-files-service-type
                  `(("/bin/sh" ,(file-append bash "/bin/sh"))
                    ("/usr/bin/env" ,(file-append coreutils "/bin/env"))))))
-- 
2.30.2


[-- Attachment #2: signature.asc --]
[-- Type: application/pgp-signature, Size: 833 bytes --]