An analysis by Tim Ruffing [1] shows that a length extension attack
adding valid extension fields to NTPv4 packets is possible with some
specific key lengths and hash functions using little-endian length like
MD5 and RIPEMD160.
chronyd currently doesn't process or generate any extension fields, but
it could be a problem in future when a non-authentication extension
field is supported.
Drop support for all RIPEMD functions as they don't seem to be secure in
the context of the NTPv4 MAC. MD5 is kept only for compatibility.
[1] https://mailarchive.ietf.org/arch/msg/ntp/gvibuB6bTbDRBumfHNdJ84Kq4kA
Setting maxsamples to 1 or 2 prevented the source from being selected as
the regression would always fail. Handle this as a special case with
disabled frequency tracking in order to enable a fast reference update
with the -q/-Q option.
Real-time scheduling and memory locking is available on posix compliant
OSs. This patch centralizes this functionality and brings support to
FreeBSD, NetBSD, and Solaris.
[ML: updated coding style]
Add an option to use the median filter to reduce noise in measurements
before they are accumulated to sourcestats, similarly to reference
clocks. The option specifies how many samples are reduced to a single
sample.
The filter is intended to be used with very short polling intervals in
local networks where it is acceptable to generate a lot of NTP traffic.
Instead of counting missing responses, switch to the offline state
immediately when sendmsg() fails.
This makes the option usable with servers and networks that may drop
packets, and the effect will be consistent with the onoffline command.
The onoffline command tells chronyd to switch all sources to the online
or offline status according to the current network configuration. A
source is considered online if it is possible to send requests to it,
i.e. a route to the network is present.
When the burst option is specified in the server/pool directive and the
current poll is longer than the minimum poll, initiate on each poll a
burst with 1 good sample and 2 or 4 total samples according to the
difference between the current and minimum poll.
This option is for indicating to chronyd that the reference clock is
kept in TAI and that chrony should attempt to convert from TAI to UTC by
using the timezone configured by the "leapsectz" directive.
Similarly to the maxdelaydevratio test, include in the maximum delay
dispersion which accumulated in the interval since the last sample.
Also, enable the test for symmetric associations.
If no rxfilter is specified in the hwtimestamp directive and the NIC
doesn't support the all or ntp filter, enable TX-only HW timestamping
with the none filter.
macOS 10.13 will implement the ntp_adjtime() system call, allowing
better control over the system clock than is possible with the existing
adjtime() system call. chronyd will support both the older and newer
calls, enabling binary code to run without recompilation on macOS 10.9
through macOS 10.13.
Early releases of macOS 10.13 have a very buggy adjtime() call. The
macOS driver tests adjtime() to see if the bug has been fixed. If the
bug persists then the timex driver is invoked otherwise the netbsd
driver.
If the -Q option is specified, disable by default pidfile, ntpport,
cmdport, Unix domain command socket, and clock control, in order to
allow starting chronyd without root privileges and/or when another
chronyd instance is already running.
Use the timezone specified by the leapsectz directive to get the
current TAI-UTC offset and set the offset of the system clock in order
to provide correct TAI time to applications using ntp_adjtime(),
ntp_gettime(), or clock_gettime(CLOCK_TAI).
Add a new clock driver that doesn't actually try to adjust the clock.
It allows chronyd to run without the capability to adjust/set the system
clock, e.g. in some containers. It can be enabled by the -x option.
Always write the measurement history on exit when the dump directory is
specified and silently ignore the dumponexit directive. There doesn't
seem to be a good use case for dumpdir and -r without dumponexit as the
history would be invalidated by adjustments of the clock that happened
between the dump command and chronyd exit.
While the measurements log can be useful for debugging problems in NTP
configuration (e.g. authentication failures with symmetric keys), it
seems most users are interested only in valid measurements (e.g. for
producing graphs) and don't expect/handle entries where some of the RFC
5905 tests 1-7 failed. Modify the measurements log option to log only
valid measurements, and for debugging purposes add a new rawmeasurements
option.
Change the default NTP rate limiting leak to 2 (25%). Change the default
command rate limiting interval to -4 (16 packets per second) and burst
to 8, so the interval is the only difference between NTP and command
rate limiting defaults.
This reverts commit 50022e9286.
Testing showed that ntpd as an NTP client performs poorly when it's
getting only 25% of responses. At least for now, disable rate limiting
by default again.
Change the default interval of both NTP and command rate limiting to -10
(1024 packets per second) and the burst to 16. The default NTP leak is 2
(rate limiting is enabled by default) and the default command leak is 0
(rate limiting is disabled by default).
The maxlockage option specifies in number of pulses how old can be
samples from the refclock specified by the lock option to be paired with
the pulses. Increasing this value is useful when the samples are
produced at a lower rate than the pulses.
The maxjitter directive sets the maximum allowed jitter of the sources
to not be rejected by the source selection algorithm. This prevents
synchronisation with sources that have a small root distance, but their
time is too variable. By default, the maximum jitter is 1 second.
Change default minsamples to 6 and polltarget to 8. This should improve
stability with extremely small jitters (e.g. HW timestamping) and not
decrease time accuracy at minimum polling interval too much.
This option sets a timeout (in seconds) after which chronyd will exit.
If the clock is not synchronised, it will exit with a non-zero status.
This is useful with the -q or -Q option to shorten the maximum time
waiting for measurements, or with the -r option to limit the time when
chronyd is running, but still allow it to adjust the frequency of the
system clock.
If the MAC in NTPv4 requests would be truncated, use version 3 by
default to avoid the truncation. This is necessary for compatibility
with older chronyd servers, which do not respond to messages with
truncated MACs.
This is an incompatible change in the output of the tracking command,
which may break some scripts, but it's necessary to avoid confusion with
IPv4 addresses when synchronised to an IPv6 server or reference clock.
In a burst of three requests (two presend + one normal) the server can
detect the client is using the interleaved mode and save the transmit
timestamp of the second response for the third response. This shortens
the interval in which the server has to keep the state.
Rework the code to make a real request for presend and process the
response, but don't accumulate the sample. This allows presend to work
in the interleaved client mode.
Add support for authenticating MS-SNTP responses in Samba (ntp_signd).
Supported is currently only the old MS-SNTP authenticator field. It's
disabled by default. It can be enabled with the --enable-ntp-signd
configure option and the ntpsigndsocket directive, which specifies the
location of the Samba ntp_signd socket.
Add offset option to the server/pool/peer directive. It specifies a
correction which will be applied to offsets measured with the NTP
source. It's particularly useful to compensate for a known asymmetry in
network delay or timestamping errors.
- fix word order, articles, consistency, and some typos
- avoid slashes, contractions, `may`, dashes in running text
- use colons before example and code blocks
- add Oxford commas
Add maxdrift directive to set the maximum assumed drift of the clock,
which sets the maximum frequency offset chronyd is allowed to use to
to correct the drift.
Similarly to unreachable sources and falsetickers, try to replace
sources with distance larger than the limit set by the maxdistance
directive with a newly resolved address of the hostname.
Add a new option (-c) to chronyc to enable printing of reports in a
column-separated values (CSV) format. IP addresses will not be resolved
to hostnames, time will be printed as number of seconds since the epoch
and values in seconds will not be converted to other units.
Split and convert the manual into four AsciiDoc documents, a document
about installation and three documents in the manpage type for
chrony.conf, chronyd and chronyc. The minimal man pages that were
maintained separately from the manual are replaced by full man pages
generated from AsciiDoc. Info files will no longer be provided.
Some parts of the manual are rewritten, updated or trimmed. The
introduction chapter is partially merged with README. The chapter about
typical operating scenarios is included in the chrony.conf man page.
Enable the PRV_Name2IPAddress() function with seccomp support and start
the helper process before loading the seccomp filter (but after dropping
root privileges). This will move the getaddrinfo() call outside the
seccomp filter and should make it more reliable as the list of required
system calls won't depend on what glibc NSS modules are used on the
system.
