Y2038¶

Y2038: lighttpd 1.4.60 and later report Y2038 safety¶

  $ lighttpd -V
    + Y2038 support                                    # Y2038-SAFE
  $ lighttpd -V
    - Y2038 support (unsafe 32-bit signed time_t)      # Y2038-UNSAFE

Y2038: general platform info¶

• Y2038-SAFE: lighttpd 64-bit builds on platforms using 64-bit time_t
  • all major 64-bit platforms (known to this author) use 64-bit time_t
• Y2038-SAFE: lighttpd 32-bit builds on platforms using 64-bit time_t
  • Linux x32 ABI (different from i686)
  • FreeBSD all 32-bit and 64-bit architectures except 32-bit i386
  • NetBSD 6.0 (released Oct 2012) all 32-bit and 64-bit architectures
  • OpenBSD 5.5 (released May 2014) all 32-bit and 64-bit architectures
  • Microsoft Windows XP and Visual Studio 2005 (? unsure ?)
    Another reference suggests Visual Studio 2015 defaults to 64-bit time_t
  • MacOS 10.15 Catalina (released 2019) drops support for 32-bit apps
• Y2038-SAFE: lighttpd 32-bit builds on platforms using 32-bit unsigned time_t
  • e.g. OpenVMS (unknown if lighttpd builds on this platform)
• Y2038-UNSAFE: lighttpd 32-bit builds on platforms using 32-bit signed time_t
  • Linux 32-bit (including i686)
    • glibc 32-bit library support not yet available for 64-bit time_t
      - https://sourceware.org/glibc/wiki/Y2038ProofnessDesign
      - Linux kernel 5.6 on 32-bit platforms does support 64-bit time_t
      https://itsubuntu.com/linux-kernel-5-6-to-fix-the-year-2038-issue-unix-y2k/
      - https://www.gnu.org/software/libc/manual/html_node/64_002dbit-time-symbol-handling.html
      "Note: at this point, 64-bit time support in dual-time configurations is work-in-progress, so for these configurations, the public API only makes the 32-bit time support available. In a later change, the public API will allow user code to choose the time size for a given compilation unit."
      - compiling with -D_TIME_BITS=64 currently has no effect
    • glibc recent (Jul 2021) mailing list discussion
      - https://public-inbox.org/bug-gnulib/878s2ozq70.fsf@oldenburg.str.redhat.com/T/
    • glibc master contains some commits for -D_TIME_BITS=64
      - https://www.phoronix.com/scan.php?page=news_item&px=Glibc-More-Y2038-Work
  • FreeBSD i386
  • DragonFlyBSD 32-bit

Y2038: mitigations attempted on Y2038-UNSAFE platforms (32-bit signed time_t)¶

• lighttpd prefers system monotonic clock instead of realtime clock in places where realtime clock is not required
• lighttpd treats negative time_t values as after 19 Jan 2038 03:14:07 GMT
  (lighttpd presumes that lighttpd will not encounter dates before 1970 during normal operation.)
• lighttpd casts struct stat st.st_mtime (and st.st_*time) through uint64_t to convert negative timestamps for comparisions with 64-bit timestamps
  (treating negative timestamp values as after 19 Jan 2038 03:14:07 GMT)
• lighttpd provides unix_time64_t (int64_t) and
• lighttpd provides struct unix_timespec64 (unix_timespec64_t)
  (struct timespec equivalent using unix_time64_t tv_sec member)
• lighttpd provides gmtime64_r() and localtime64_r() wrappers for platforms 32-bit platforms using 32-bit time_t and lighttpd temporarily shifts the year in order to use gmtime_r() and localtime_r() (or gmtime() and localtime()) from standard libraries, before readjusting year and passing struct tm to formatting functions such as strftime()
• lighttpd provides TIME64_CAST() macro to cast signed 32-bit time_t to unsigned 32-bit and then to unix_time64_t

Y2038: Warning¶

Note: while lighttpd tries handle times past 19 Jan 2038 03:14:07 GMT on 32-bit platforms using 32-bit signed time_t, underlying libraries and underlying filesystems might not behave properly after 32-bit signed time_t overflows (19 Jan 2038 03:14:08 GMT). If a given 32-bit OS does not work properly using negative time_t values, then lighttpd likely will not work properly on that system.

Y2038: Other references and blogs¶

https://en.wikipedia.org/wiki/Year_2038_problem
https://en.wikipedia.org/wiki/Time_formatting_and_storage_bugs
http://www.lieberbiber.de/2017/03/14/a-look-at-the-year-20362038-problems-and-time-proofness-in-various-systems/