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ntpquery: Add some more validation of the response header

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Nico Weber 2020-10-16 22:44:20 -04:00 • committed by Andreas Kling
parent 18d88e0eaa
commit 0658051996
Notes: sideshowbarker 2024-07-19 01:52:40 +09:00
1 changed files with 24 additions and 3 deletions
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27
Userland/ntpquery.cpp
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@ -58,6 +58,10 @@ struct [[gnu::packed]] NtpPacket
NtpTimestamp origin_timestamp;
NtpTimestamp receive_timestamp;
NtpTimestamp transmit_timestamp;
uint8_t leap_information() const { return li_vn_mode >> 6; }
uint8_t version_number() const { return (li_vn_mode >> 3) & 7; }
uint8_t mode() const { return li_vn_mode & 7; }
};
static_assert(sizeof(NtpPacket) == 48);
@ -218,10 +222,27 @@ int main(int argc, char** argv)
timeval kernel_receive_time;
memcpy(&kernel_receive_time, CMSG_DATA(cmsg), sizeof(kernel_receive_time));
// Checks 3 and 4 from end of section 5 of rfc4330.
if (packet.version_number() != 3 && packet.version_number() != 4) {
fprintf(stderr, "unexpected version number %d\n", packet.version_number());
return 1;
}
if (packet.mode() != 4) { // 4 means "server", which should be the reply to our 3 ("client") request.
fprintf(stderr, "unexpected mode %d\n", packet.mode());
return 1;
}
if (packet.stratum == 0 || packet.stratum >= 16) {
fprintf(stderr, "unexpected stratum value %d\n", packet.stratum);
return 1;
}
if (packet.origin_timestamp != random_transmit_timestamp) {
fprintf(stderr, "expected %#016llx as origin timestamp, got %#016llx\n", random_transmit_timestamp, packet.origin_timestamp);
return 1;
}
if (packet.transmit_timestamp == 0) {
fprintf(stderr, "got transmit_timestamp 0\n");
return 1;
}
NtpTimestamp origin_timestamp = ntp_timestamp_from_timeval(local_transmit_time);
NtpTimestamp receive_timestamp = be64toh(packet.receive_timestamp);
@ -242,9 +263,9 @@ int main(int argc, char** argv)
if (verbose) {
printf("NTP response from %s:\n", inet_ntoa(peer_address.sin_addr));
printf("Leap Information: %d\n", packet.li_vn_mode >> 6);
printf("Version Number: %d\n", (packet.li_vn_mode >> 3) & 7);
printf("Mode: %d\n", packet.li_vn_mode & 7);
printf("Leap Information: %d\n", packet.leap_information());
printf("Version Number: %d\n", packet.version_number());
printf("Mode: %d\n", packet.mode());
printf("Stratum: %d\n", packet.stratum);
printf("Poll: %d\n", packet.stratum);
printf("Precision: %d\n", packet.precision);