zeek/scripts/base/protocols/ntp/main.zeek
2021-02-04 12:18:46 -08:00

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module NTP;
export {
redef enum Log::ID += { LOG };
global log_policy: Log::PolicyHook;
type Info: record {
## Timestamp for when the event happened.
ts: time &log;
## Unique ID for the connection.
uid: string &log;
## The connection's 4-tuple of endpoint addresses/ports.
id: conn_id &log;
## The NTP version number (1, 2, 3, 4).
version: count &log;
## The NTP mode being used.
mode: count &log;
## The stratum (primary server, secondary server, etc.).
stratum: count &log;
## The maximum interval between successive messages.
poll: interval &log;
## The precision of the system clock.
precision: interval &log;
## Total round-trip delay to the reference clock.
root_delay: interval &log;
## Total dispersion to the reference clock.
root_disp: interval &log;
## For stratum 0, 4 character string used for debugging.
## For stratum 1, ID assigned to the reference clock by IANA.
## Above stratum 1, when using IPv4, the IP address of the reference
## clock. Note that the NTP protocol did not originally specify a
## large enough field to represent IPv6 addresses, so they use
## the first four bytes of the MD5 hash of the reference clock's
## IPv6 address (i.e. an IPv4 address here is not necessarily IPv4).
ref_id: string &log;
## Time when the system clock was last set or correct.
ref_time: time &log;
## Time at the client when the request departed for the NTP server.
org_time: time &log;
## Time at the server when the request arrived from the NTP client.
rec_time: time &log;
## Time at the server when the response departed for the NTP client.
xmt_time: time &log;
## Number of extension fields (which are not currently parsed).
num_exts: count &default=0 &log;
};
## Event that can be handled to access the NTP record as it is sent on
## to the logging framework.
global log_ntp: event(rec: Info);
}
redef record connection += {
ntp: Info &optional;
};
const ports = { 123/udp };
redef likely_server_ports += { ports };
event zeek_init() &priority=5
{
Analyzer::register_for_ports(Analyzer::ANALYZER_NTP, ports);
Log::create_stream(NTP::LOG, [$columns = Info, $ev = log_ntp, $path="ntp", $policy=log_policy]);
}
event ntp_message(c: connection, is_orig: bool, msg: NTP::Message) &priority=5
{
local info: Info &is_assigned; # for case where no $std_msg
info$ts = network_time();
info$uid = c$uid;
info$id = c$id;
info$version = msg$version;
info$mode = msg$mode;
if ( msg?$std_msg )
{
info$stratum = msg$std_msg$stratum;
info$poll = msg$std_msg$poll;
info$precision = msg$std_msg$precision;
info$root_delay = msg$std_msg$root_delay;
info$root_disp = msg$std_msg$root_disp;
if ( msg$std_msg?$kiss_code )
info$ref_id = msg$std_msg$kiss_code;
else if ( msg$std_msg?$ref_id )
info$ref_id = msg$std_msg$ref_id;
else if ( msg$std_msg?$ref_addr )
info$ref_id= cat(msg$std_msg$ref_addr);
info$ref_time = msg$std_msg$ref_time;
info$org_time = msg$std_msg$org_time;
info$rec_time = msg$std_msg$rec_time;
info$xmt_time = msg$std_msg$xmt_time;
info$num_exts = msg$std_msg$num_exts;
}
# Copy the present packet info into the connection record
# If more ntp packets are sent on the same connection, the newest one
# will overwrite the previous
c$ntp = info;
}
event ntp_message(c: connection, is_orig: bool, msg: NTP::Message) &priority=-5
{
if ( c?$ntp && msg$mode <= 5 )
Log::write(NTP::LOG, c$ntp);
}