fix edge case for initial chunked data
(bug introduced in lighttpd 1.4.56)
If chunked header received without data before response headers sent,
then initial chunked data might be sent to client without chunked header
if client made an HTTP/1.1 request and the response is Transfer-Encoding
chunked and lighttpd is configured to stream the response (non-zero
value for server.stream-response-body). This might occur if lighttpd
backend is connected via a unix domain socket and the initial chunk is
large and coming from a temporary file. It may be sent in a separate
packet since lighttpd does not use TCP_CORK on unix domain sockets.
x-ref:
"Failure on second request in http proxy backend"
https://redmine.lighttpd.net/issues/3046
"Socket errors after update to version 1.4.56"
https://redmine.lighttpd.net/issues/3044
rename log_error_multiline_buffer() to log_error_multiline()
and take (char *)ptr and (size_t)len instead of (buffer *)b
When debug printing request and response headers,
print each header on separate line for readability
and omit '\r' if "\r\n" ends line
If a system call returns EMFILE, then admin should increase
server.max-fds and check/increase rlimits for num files (ulimit -Hn)
Alternatively, the admin might decrease server.max-connections to limit
the number of connections served in parallel.
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
faster to use http_header_request_set_ptr() and buffer_copy_string_len()
than to use http_header_request_set() and http_header_request_get()
check r->http_host for NULL instead of relying on buffer_copy_* to do so
special-case OPTIONS * and CONNECT in http_response_prepare()
http_response_prepare() is no longer revisited if r->handler_module
is set, so it is no longer necessary to fill r->physical.path for
CONNECT
reuse cache lookup in common case of serving a static file
rather than repeating the stat_cache_entry lookup
(which is more work than memcmp() to re-check stat_cache_entry match)
optimize buffer_* primitives
Other than buffer_string_set_length(), reallocate with one power-2 step
in size (or use the requested size, if larger). This replaces the fixed
BUFFER_PIECE_SIZE round-up of only 64 bytes extension each reallocation,
which could lead to excessive reallocations in some scenarios.
buffer_extend() convenience routine to prep for batch append
(combines buffer_string_prepare_append() and buffer_commit())
mod_fastcgi, mod_scgi, mod_proxy and others now leverage buffer_extend()
mod_scgi directly performs little-endian encoding of short ints
http_response_write_header() optimizes writing response header,
leveraging buffer_extend()
modify mod_proxy to append line ends
similar to how it is done in http_response_write_header()
(removes one call to buffer_append_string_len())
RFC 7233 Range handling for all non-streaming responses,
including (non-streaming) dynamic responses
(previously Range responses handled only for static files)
(thx flynn)
When the backend sends Transfer-Encoding: chunked (which is HTTP/1.1,
not HTTP/1.0) and the client is HTTP/1.1, then lighttpd will transfer
the chunked encoding as it is sent from the backend without excess data
copying involved in decoding and then re-encoding. The bug is that if
the first data chunk (or chunks) is partially received at the same time
as the response headers, then the chunked encoding got corrupted.
x-ref:
"Socket errors after update to version 1.4.56"
https://redmine.lighttpd.net/issues/3044
use http_chunk_append_file_ref() and http_chunk_append_file_ref_range()
reduce resource usage (number of fds open) by reference counting open
fds to files served, and sharing the fd among FILE_CHUNKs in responses
relay 1xx from backend over HTTP/1.1, e.g. 103 Early Hints
(if client is connected using HTTP/1.1)
enabled by default unless disabled in lighttpd.conf with:
server.feature-flags += ( "server.h1-discard-backend-1xx" = "enable" )
Warning: backends which send 103 Early Hints should check User-Agent
before doing so since naive clients might not handle unexpected 1xx.
Some clients may take the 1xx response as the final response, expecting
only one response. Some clients might not properly handle 100 Continue
if the client did not send Expect: 100-continue with the request.
https://tools.ietf.org/html/rfc8297#section-3 Security Considerations
x-ref:
An HTTP Status Code for Indicating Hints (103 Early Hints)
https://tools.ietf.org/html/rfc8297
defer optimization to read small files into memory until after
response_start hooks have a chance to run, e.g. until after
mod_deflate chooses whether or not to serve file from compressed
cache, if deflate.cache-dir is configured
Glenn Strauss