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
- 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/
- 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
- 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/
This commit is a large set of code changes and results in removal of
hundreds, perhaps thousands, of CPU instructions, a portion of which
are on hot code paths.
Most (buffer *) used by lighttpd are not NULL, especially since buffers
were inlined into numerous larger structs such as request_st and chunk.
In the small number of instances where that is not the case, a NULL
check is often performed earlier in a function where that buffer is
later used with a buffer_* func. In the handful of cases that remained,
a NULL check was added, e.g. with r->http_host and r->conf.server_tag.
- check for empty strings at config time and set value to NULL if blank
string will be ignored at runtime; at runtime, simple pointer check
for NULL can be used to check for a value that has been set and is not
blank ("")
- use buffer_is_blank() instead of buffer_string_is_empty(),
and use buffer_is_unset() instead of buffer_is_empty(),
where buffer is known not to be NULL so that NULL check can be skipped
- use buffer_clen() instead of buffer_string_length() when buffer is
known not to be NULL (to avoid NULL check at runtime)
- use buffer_truncate() instead of buffer_string_set_length() to
truncate string, and use buffer_extend() to extend
Examples where buffer known not to be NULL:
- cpv->v.b from config_plugin_values_init is not NULL if T_CONFIG_BOOL
(though we might set it to NULL if buffer_is_blank(cpv->v.b))
- address of buffer is arg (&foo)
(compiler optimizer detects this in most, but not all, cases)
- buffer is checked for NULL earlier in func
- buffer is accessed in same scope without a NULL check (e.g. b->ptr)
internal behavior change:
callers must not pass a NULL buffer to some funcs.
- buffer_init_buffer() requires non-null args
- buffer_copy_buffer() requires non-null args
- buffer_append_string_buffer() requires non-null args
- buffer_string_space() requires non-null arg
HTTP/2 requires that TLS protocol >= TLSv1.2
HTTP/2 requires that TLS record compression be disabled
HTTP/2 requires that TLSv1.2 renegotiation be disabled
HTTP/2 requires that TLS SNI extension be presented with ALPN h2
(not enforced;
SNI omitted by client when connecting to IP instead of to name)
RFC 7540 9.2 Use of TLS Features
"Implementations are encouraged to provide defaults that comply,
but it is recognized that deployments are ultimately responsible
for compliance."
If TLS record compression or renegotiation are for some reason required
(which is strongly discouraged), then disable HTTP/2 in lighttpd with
server.feature-flags = ("server.h2proto" => "disable")
rename to reflect use for verifying client certificate
(old names are still accepted, but are discouraged)
ssl.ca-file -> ssl.verifyclient.ca-file
ssl.ca-dn-file -> ssl.verifyclient.ca-dn-file
ssl.ca-crl-file -> ssl.verifyclient.ca-crl-file
recognize and translate a common recommended cipherstring
"ECDHE+AESGCM:ECDHE+AES256:CHACHA20:!SHA1:!SHA256:!SHA384"
(basically: ECDHE+AESGCM:ECDHE+AES256:CHACHA20
without CBC ciphers reported as weak by SSLLabs)
(removed two commits ago)
must check selected ALPN after client hello has completed
for case where hctx->conf.ssl_acme_tls_1 is not enabled
or else ALPN "h2" will not be detected
mbedtls does not provide a callback for ALPN and expects certificate to
be set in SNI callback (if set), while still in MBEDTLS_SSL_CLIENT_HELLO
state. Waiting until after MBEDTLS_SSL_CLIENT_HELLO would be fine for
using ALPN for "h2", but is too late to set acme-tls/1 challenge cert.
Therefore, parse client hello for ALPN prior to initiating mbedtls
processing of handshake.
recognize and translate a common recommended cipherstring
"EECDH+AESGCM:AES256+EECDH:CHACHA20:!SHA1:!SHA256:!SHA384"
(basically: EECDH+AESGCM:AES256+EECDH:CHACHA20
without CBC ciphers reported as weak by SSLLabs)
flagged by coverity
final segment of colon (':') separated string was being ignored
in some TLS config strings in mod_gnutls and mod_mbedtls
workaround: add ':' at end of config string (or apply this patch)
On some older gcc, strncmp is a macro and expects three arguments,
but does not see expansion of lighttpd CONST_STR_LEN() macro before
warning/error about incorrect number of arguments
include mbedtls/platform_util.h for mbedtls_platform_zeroize()
(instead of relying on an indirect include)
(fixes build with (very old) mbedtls-2.14.0)
disabled by default, but can be enabled
(session tickets should be preferred)
applies to mod_openssl, mod_wolfssl, mod_nss
session cache is not currently implemented in mod_mbedtls or mod_gnutls
difference from mod_openssl:
Admin should schedule an independent job to periodically
generate a new STEK up to 2 times during key lifetime
(mbedtls internals store up to 2 keys)
(more details in prior commit message for mod_openssl)
(experimental)
mod_mbedtls supports most ssl.* config options supported by mod_openssl
thx Ward Willats for the initial discussion and attempt in the comments
https://redmine.lighttpd.net/boards/3/topics/7029
Glenn Strauss