It's not expected we will work with such large arrays anytime soon, but
better be safe than sorry.
Also, limit the number of elements to 2^31-1 to prevent infinite loop in
the calculation of allocated elements.
When reducing the list of selectable sources to sources with the prefer
option, sources before the first preferred source were left with the
SRC_OK status, which triggered an assertion failure in the next
selection.
The leaponly option can be used to enable a mode where only leap seconds
are smoothed out and normal offset/frequency changes are ignored. This
is useful to make the interval in which a leap second is smoothed out
constant and allow an NTP client to use multiple leap smearing servers
safely.
Sources that are not specified as a pool and have a name (i.e. not
specified by an IP address or added from chronyc) will be replaced with
a newly resolved address of the name when they become unreachable or
falseticker too.
In UTI_IsTimeOffsetSane() consider time in one year interval before
32-bit time_t overflow (in 2038) as invalid. Hopefully everything will
be using 64-bit time_t when that time comes.
Different systems may consider different time values to be valid.
Don't exit on settimeofday()/adjtimex() error in case the check in
UTI_IsTimeOffsetSane() isn't restrictive enough.
When allocating memory to save unacknowledged replies to authenticated
command requests, the last "next" pointer was not initialized to NULL.
When all allocated reply slots were used, the next reply could be
written to an invalid memory instead of allocating a new slot for it.
An attacker that has the command key and is allowed to access cmdmon
(only localhost is allowed by default) could exploit this to crash
chronyd or possibly execute arbitrary code with the privileges of the
chronyd process.
When NTP or cmdmon access was configured (from chrony.conf or via
authenticated cmdmon) with a subnet size that is indivisible by 4 and
an address that has nonzero bits in the 4-bit subnet remainder (e.g.
192.168.15.0/22 or f000::/3), the new setting was written to an
incorrect location, possibly outside the allocated array.
An attacker that has the command key and is allowed to access cmdmon
(only localhost is allowed by default) could exploit this to crash
chronyd or possibly execute arbitrary code with the privileges of the
chronyd process.
Time smoothing determines an offset that needs to be applied to the
cooked time to make it smooth for external observers. Observed offset
and frequency change slowly and there are no discontinuities. This can
be used on an NTP server to make it easier for the clients to track the
time and keep their clocks close together even when large offset or
frequency corrections are applied to the server's clock (e.g. after
being offline for longer time).
Accumulated offset and frequency are smoothed out in three stages. In
the first stage, the frequency is changed at a constant rate (wander) up
to a maximum, in the second stage the frequency stays at the maximum for
as long as needed and in the third stage the frequency is brought back
to zero.
Time smoothing is configured by the smoothtime directive. It takes two
arguments, maximum frequency offset and maximum wander. It's disabled by
default.
