wireguard: netdev file can leak private key

[Andreas Hasenack]

When using netplan with wireguard, netplan will render the /run/systemd/network/10-netplan-${name}.netdev file with 0644 permissions.

That file contains the wireguard private key, which, if specified literally (instead of using a file), will leak that key to all local users of the system. This may not be desirable.

For example, I have this yaml in /etc/netplan/home0.yaml:
network:
  version: 2
  tunnels:
    home0:
      mode: wireguard
      key: <base64 private key contents>
      port: 51000
      addresses: [10.10.11.2/24]
      peers:
        - keys:
            public: <base64 public key contents>
          endpoint: 10.48.132.39:51000
          allowed-ips: [10.10.11.0/24,10.10.10.0/24]
      routes:
        - to: 10.10.10.0/24
          from: 10.10.11.2
          scope: link

When that is rendered and applied with `netplan apply`, this error is logged in /var/log/syslog:
Aug 26 14:23:30 laptop-coffee-shop systemd-networkd[537]: /run/systemd/network/10-netplan-home0.netdev has 0644 mode that is too permissive, please adjust the ownership and access mode.

And indeed, that file contains the same literal private key, as expected:

# cat /run/systemd/network/10-netplan-home0.netdev
[NetDev]
Name=home0
Kind=wireguard

[WireGuard]
PrivateKey=<base64 private key contents>
ListenPort=51000

[WireGuardPeer]
PublicKey=<base64 public key contents>
AllowedIPs=10.10.11.0/24,10.10.10.0/24
Endpoint=10.48.132.39:51000

Its permissions should probably be 0640 root:systemd-networkd.

This is not an issue if the private key is specified via a file, in which case systemd-networkd won't even issue that warning.

[Lukas Märdian (slyon)]

ACK. The rendered files should not be world readable.

[Lukas Märdian (slyon)]

see also bug #2065738

[Mark Esler (eslerm)]

Please refer to this issue as CVE-2022-4968.

[Launchpad Janitor (janitor)]

This bug was fixed in the package netplan.io - 1.0-2ubuntu1.1

---------------
netplan.io (1.0-2ubuntu1.1) noble-security; urgency=medium

  * SECURITY UPDATE: weak permissions on secret files, command injection
    - d/p/lp2065738/0014-libnetplan-use-more-restrictive-file-permissions.patch:
      Use more restrictive file permissions to prevent unprivileged users to
      read sensitive data from back end files (LP: #2065738, #1987842)
    - CVE-2022-4968
    - d/p/lp2066258/0015-libnetplan-escape-control-characters.patch:
      Escape control characters in the parser and double quotes in backend
      files.
    - d/p/lp2066258/0016-backends-escape-file-paths.patch:
      Escape special characters in file paths.
    - d/p/lp2066258/0017-backends-escape-semicolons-in-service-units.patch:
      Escape isolated semicolons in systemd service units. (LP: #2066258)
  * debian/netplan-generator.postinst: Add a postinst maintainer script to call
    the generator. It's needed so the file permissions fixes will be applied
    automatically, thanks to danilogondolfo

 -- Sudhakar Verma <email address hidden> Tue, 25 Jun 2024 00:13:00 +0530

[Launchpad Janitor (janitor)]

This bug was fixed in the package netplan.io - 0.104-0ubuntu2~20.04.5

---------------
netplan.io (0.104-0ubuntu2~20.04.5) focal-security; urgency=medium

  * SECURITY UPDATE: weak permissions on secret files, command injection
    - d/p/lp2065738/0015-libnetplan-use-more-restrictive-file-permissions.patch:
      Use more restrictive file permissions to prevent unprivileged users to
      read sensitive data from back end files (LP: #2065738, #1987842)
    - CVE-2022-4968
    - d/p/lp2066258/0016-libnetplan-escape-control-characters.patch:
      Escape control characters in the parser and double quotes in backend files
    - d/p/lp2066258/0017-libnetplan-escape-file-paths.patch:
      Escape special characters in file paths
    - d/p/lp2066258/0018-libnetplan-escape-semicolons-in-service-units.patch:
      Escape isolated semicolons in systemd service units (LP: #2066258)
  * debian/netplan.io.postinst: Add a postinst maintainer script to call the
    generator. It's needed so the file permissions fixes will be applied
    automatically, thanks to danilogondolfo

 -- Sudhakar Verma <email address hidden> Mon, 24 Jun 2024 22:03:31 +0530

[Launchpad Janitor (janitor)]

This bug was fixed in the package netplan.io - 0.106.1-7ubuntu0.22.04.3

---------------
netplan.io (0.106.1-7ubuntu0.22.04.3) jammy-security; urgency=medium

  * SECURITY UPDATE: weak permissions on secret files, command injection
    - d/p/lp2065738/0028-libnetplan-use-more-restrictive-file-permissions.patch:
      Use more restrictive file permissions to prevent unprivileged users to
      read sensitive data from back end files (LP: #2065738, #1987842)
    - CVE-2022-4968
    - d/p/lp2066258/0029-libnetplan-escape-control-characters.patch:
      Escape control characters in the parser and double quotes in backend
      files
    - d/p/lp2066258/0030-backends-escape-file-paths.patch:
      Escape special characters in file paths
    - d/p/lp2066258/0031-backends-escape-semicolons-in-service-units.patch:
      Escape isolated semicolons in systemd service units (LP: #2066258)
  * debian/netplan.io.postinst: Add a postinst maintainer script to call the
    generator. It's needed so the file permissions fixes will be applied
    automatically, thanks to danilogondolfo

 -- Sudhakar Verma <email address hidden> Mon, 24 Jun 2024 23:20:42 +0530

[Launchpad Janitor (janitor)]

This bug was fixed in the package netplan.io - 0.107-5ubuntu0.3

---------------
netplan.io (0.107-5ubuntu0.3) mantic-security; urgency=medium

  * SECURITY UPDATE: weak permissions on secret files, command injection
    - d/p/lp2065738/0012-libnetplan-use-more-restrictive-file-permissions.patch:
      Use more restrictive file permissions to prevent unprivileged users to
      read sensitive data from back end files (LP: #2065738, #1987842)
    - CVE-2022-4968
    - d/p/lp2065738/0013-cli-generate-call-daemon-reload-after-generate.patch:
      Call systemd daemon-reload as part of the netplan generate cli command
    - d/p/lp2066258/0014-libnetplan-escape-control-characters.patch:
      Escape control characters in the parser and double quotes in backend
      files.
    - d/p/lp2066258/0015-backends-escape-file-paths.patch:
      Escape special characters in file paths.
    - d/p/lp2066258/0016-backends-escape-semicolons-in-service-units.patch:
      Escape isolated semicolons in systemd service units. (LP: #2066258)
  * debian/netplan-generator.postinst: Add a postinst maintainer script to call
    the generator. It's needed so the file permissions fixes will be applied
    automatically, thanks to danilogondolfo

 -- Sudhakar Verma <email address hidden> Mon, 24 Jun 2024 23:58:40 +0530