Commit Graph

4 Commits

Author SHA1 Message Date
Glenn Strauss 309c1693ac [multiple] Y2038 32-bit signed time_t mitigations
Most OS platforms have already provided solutions to
Y2038 32-bit signed time_t 5 - 10 years ago (or more!)
Notable exceptions are Linux i686 and FreeBSD i386.

Since 32-bit systems tend to be embedded systems,
and since many distros take years to pick up new software,
this commit aims to provide Y2038 mitigations for lighttpd
running on 32-bit systems with Y2038-unsafe 32-bit signed time_t

* 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
              - Linux kernel 5.6 on 32-bit platforms does support 64-bit time_t
                "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
      - 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

* 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.

* Other references and blogs
2021-09-04 08:08:26 -04:00
Glenn Strauss 6b6252a3ba [core] move timegm() impl inline in sys-time.h
(for systems without timegm())
2021-04-26 12:50:20 -04:00
Glenn Strauss 122094e3e3 [multiple] employ http_date.h, sys-time.h
- replace use of strptime() w/ implementation specialized for HTTP dates
- use thread-safe gmtime_r(), localtime_r() (replace localtime, gmtime)
2020-12-24 16:13:20 -05:00
Glenn Strauss f928f6d827 [core] sys-time.h - localtime_r,gmtime_r macros
sys-time.h - localtime_r,gmtime_r macros if needed

provide rudimentary localtime_r() and gmtime_r() if not present
(wraps localtime() and gmtime() funtions, but are not thread-safe since
 they do not take a lock around access to localtime() and gmtime())

(import from one of my development branches from 2015)
2020-12-24 16:13:20 -05:00