To prevent an attacker using chronyd in an amplification attack, change
the protocol to include padding in request packets so that the largest
possible reply is not larger than the request. Request packets that
don't include this padding are ignored as invalid.
This is an incompatible change in the protocol. Clients from chrony
1.27, 1.28 and 1.29 will receive NULL reply with STT_BADPKTVERSION and
print "Protocol version mismatch". Clients from 1.26 and older will not
receive a reply as it would be larger than the request if it was padded
to be compatible with their protocol.
Support for the SUBNETS_ACCESSED and CLIENT_ACCESSES commands was
enabled in chronyd, but in chronyc it was always disabled and the
CLIENT_ACCESSES_BY_INDEX command was used instead. As there is no plan
to enable it in the future, remove the support completely.
When the length of the REQ_SUBNETS_ACCESSED, REQ_CLIENT_ACCESSES
command requests and the RPY_SUBNETS_ACCESSED, RPY_CLIENT_ACCESSES,
RPY_CLIENT_ACCESSES_BY_INDEX, RPY_MANUAL_LIST command replies is
calculated, the number of items stored in the packet is not validated.
A crafted command request/reply can be used to crash the server/client.
Only clients allowed by cmdallow (by default only localhost) can crash
the server.
With chrony versions 1.25 and 1.26 this bug has a smaller security
impact as the server requires the clients to be authenticated in order
to process the subnet and client accesses commands. In 1.27 and 1.28,
however, the invalid calculated length is included also in the
authentication check which may cause another crash.
Combine only sources whose distance is shorter than distance of the
selected source multiplied by the value of combinelimit and their
estimated frequencies are close to the frequency of the selected source.
Add outlyer status for sources which are selectable, but not included in
the combining. The status is displayed as '-' in the chronyc sources
output.
- normalize command line before parsing
- compare whole words
- check for missing/extra arguments in config parsing
- use strdup for string allocation
- share code for reporting syntax errors
- avoid using function pointers
- cleanup the code a bit
Allow different hash functions to be used in the NTP and cmdmon
protocols. This breaks the cmdmon protocol compatibility. Extended key
file format is used to specify the hash functions for chronyd and new
authhash command is added to chronyc. MD5 is the default and the only
function included in the chrony source code, other functions will be
available from libraries.
Require that the ratio of the increase in delay from the minimum one in
the stats data register to the standard deviation of the offsets in the
register is less than maxdelaydevratio or the difference between
measured offset and predicted offset is larger than the increase in
delay. In the allowed delay increase is included also skew and maximum
clock frequency error.
maxdelaydevratio is 10.0 by default.
Instead of following skew changes, adjust polling interval so that the
number of measurements used in the regression algorithm remains close to
a target value. It can be configured with a new polltarget option
(6 by default).
