Miroslav Lichvar [Mon, 27 Jul 2015 10:24:13 +0000 (12:24 +0200)]
sys: add new log message for kernel status reset after leap second
When a leap second is applied by the kernel, it doesn't actually clear
the STA_INS|STA_DEL bits from the status word, but the state returned
by ntp_adjtime()/adjtimex() is TIME_WAIT until the application clears
the bits.
Add "System clock status reset after leap second" log message for this
case.
Miroslav Lichvar [Wed, 22 Jul 2015 15:42:42 +0000 (17:42 +0200)]
makefile: install chrony.txt in install-doc only
Don't install chrony.txt in make install to avoid dependency on makeinfo
since chrony.texi is prepared by configure to set the default paths in
the documentation.
Miroslav Lichvar [Tue, 23 Jun 2015 12:48:31 +0000 (14:48 +0200)]
sys: fix clock stepping by integer number of seconds on Linux
The kernel requires in the ADJ_SETOFFSET | ADJ_NANO mode that the
timex.time.tv_usec value is smaller than 10^9 nanosecond, which wasn't
the case with a negative integer offset (e.g. inserted leap second).
Miroslav Lichvar [Mon, 22 Jun 2015 09:09:31 +0000 (11:09 +0200)]
ntp: use specific reference ID when smoothing served time
Set refid in server/broadcast packets to 127.127.1.255 when a time
smoothing offset is applied to the timestamps. This allows the clients
and administrators to detect that the server is not serving its best
estimate of the true time.
sched: detect timeout overflow in SCH_AddTimeoutByDelay()
Abort when the system time gets so close to the end of 32-bit time_t
that timeouts added by delay start to overflow. This is an addition to
the loop detector in dispatch_timeouts().
sources: fix marking of non-preferred selectable sources
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.
smooth: add option to smooth out only leap seconds
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.
Miroslav Lichvar [Fri, 15 May 2015 16:38:03 +0000 (18:38 +0200)]
ntp: replace non-pool sources when unreachable or falsetickers
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.
Miroslav Lichvar [Fri, 10 Apr 2015 07:30:52 +0000 (09:30 +0200)]
util: don't allow time too close to 32-bit time_t overflow
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.
sys: allow drivers to fail when applying step offset
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.
Miroslav Lichvar [Mon, 30 Mar 2015 13:13:27 +0000 (15:13 +0200)]
cmdmon: fix initialization of allocated reply slots
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.
Miroslav Lichvar [Mon, 30 Mar 2015 12:41:37 +0000 (14:41 +0200)]
addrfilt: fix access configuration with subnet size indivisible by 4
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.
Miroslav Lichvar [Tue, 31 Mar 2015 13:47:11 +0000 (15:47 +0200)]
ntp: add server time smoothing
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.
ntp: protect authenticated symmetric associations against DoS attacks
An attacker knowing that NTP hosts A and B are peering with each other
(symmetric association) can send a packet with random timestamps to host
A with source address of B which will set the NTP state variables on A
to the values sent by the attacker. Host A will then send on its next
poll to B a packet with originate timestamp that doesn't match the
transmit timestamp of B and the packet will be dropped. If the attacker
does this periodically for both hosts, they won't be able to synchronize
to each other. It is a denial-of-service attack.
According to [1], NTP authentication is supposed to protect symmetric
associations against this attack, but in the NTPv3 (RFC 1305) and NTPv4
(RFC 5905) specifications the state variables are updated before the
authentication check is performed, which means the association is
vulnerable to the attack even when authentication is enabled.
To fix this problem in chrony, save the originate and local timestamps
only when the authentication check (test5) passed.
projects / thirdparty / chrony.git / log
