Remove automatic download and compilation of clknetsim. If clknetsim is
not found, skip all simulation tests, but don't fail "make check".
Also, respect the CLKNETSIM_PATH environment variable.
There was an incompatible change in the client access report. To avoid
bumping the protocol version drop support for the original request/reply
types and define new CLIENT_ACCESSES_BY_INDEX2 types as a newer version
of the command.
The clientlog record still uses 16-bit integers to count dropped
packets, but this will avoid an incompatible change in the command
reply if there will be a need to count more than 2^16 drops.
After restricting authentication of servers and peers to the specified
key, a short key in the key file is a security problem from the client's
point of view only if it's specified for a source.
Count total number of NTP and command hits. Count also number of log
records that were replaced when the hash table couldn't be resized due
to the memory limit.
When a server/peer was specified with a key number to enable
authentication with a symmetric key, packets received from the
server/peer were accepted if they were authenticated with any of
the keys contained in the key file and not just the specified key.
This allowed an attacker who knew one key of a client/peer to modify
packets from its servers/peers that were authenticated with other
keys in a man-in-the-middle (MITM) attack. For example, in a network
where each NTP association had a separate key and all hosts had only
keys they needed, a client of a server could not attack other clients
of the server, but it could attack the server and also attack its own
clients (i.e. modify packets from other servers).
To not allow the server/peer to be authenticated with other keys
extend the authentication test to check if the key ID in the received
packet is equal to the configured key number. As a consequence, it's
no longer possible to authenticate two peers to each other with two
different keys, both peers have to be configured to use the same key.
This issue was discovered by Matt Street of Cisco ASIG.
