[pbs-devel] [PATCH proxmox 0/5] sys: email: always format 'Date' header with C locale

[Lukas Wagner <l.wagner@proxmox.com>]

This patch series makes the formatting of the 'Date' header for sent emails
independent of the system locale. Previously, strftime was used to generate
the header, but since this function is locale-aware, invalid Date headers
could be generated.
As an example, if the locale was `de_DE.UTF-8`, then 

Date: Di, 05 Dez 2023 12:05:50 +0100
 instead of  
Date: Tue, 05 Dec 2023 12:05:50 +0100

would be generated, violating RFC2822 [1]. This trips up some email clients 
(e.g. KMail), making them fall back to Jan 1970 (epoch 0).

This is fixed by adding `strftime_l`, which allows passing a locale to
used. Additionally, `epoch_to_rfc2822` was added, which formats a 
unix epoch value to a valid RFC2822 date string (with a fixed "C" locale).

Popped up in our forum:
https://forum.proxmox.com/threads/pve-mail-notification-kein-datum-mehr-zum-korrekten-einsortieren.137556

The following projects need to be bumped and rebuilt:
  - proxmox_sys, and therefore
      - proxmox_notify, and therefore
          - libpve-rs-perl 
          - proxmox-mail-forward
      - proxmox-backup (uses proxmox_sys::email::sendmail directly)

[1] https://www.rfc-editor.org/rfc/rfc2822#section-3.3

Lukas Wagner (5):
  time: posix: use strftime from the `libc` crate.
  time: posix: inline vars in string formatting
  time: posix: add bindings for strftime_l
  time: posix: add epoch_to_rfc2822
  sys: email: use `epoch_to_rfc2822` from proxmox_time

 proxmox-sys/src/email.rs  |   3 +-
 proxmox-time/src/posix.rs | 150 +++++++++++++++++++++++++++++++-------
 2 files changed, 125 insertions(+), 28 deletions(-)

-- 
2.39.2