DWS/chrony
1
0
Fork 0
mirror of https://gitlab.com/chrony/chrony.git synced 2025-12-03 20:45:07 -05:00
Code Issues Packages Projects Releases Wiki Activity

Fuzz transmit timestamp

Browse Source 
Add random bits below clock precision to the timestamp to make
it less predictable.
This commit is contained in:
Miroslav Lichvar
2012-05-22 17:16:41 +02:00
parent d0acfc2652
commit df6c2a432f
6 changed files with 41 additions and 13 deletions
Download Patch File Download Diff File Expand all files Collapse all files

13
ntp_core.c
View File

@@ -419,7 +419,7 @@ transmit_packet(NTP_Mode my_mode, /* The mode this machine wants to be */
/* Parameters read from reference module */
int are_we_synchronised, our_stratum;
NTP_Leap leap_status;
uint32_t our_ref_id;
uint32_t our_ref_id, ts_fuzz;
struct timeval our_ref_time;
double our_root_delay, our_root_dispersion;
@@ -458,7 +458,7 @@ transmit_packet(NTP_Mode my_mode, /* The mode this machine wants to be */
message.reference_id = htonl((NTP_int32) our_ref_id);
/* Now fill in timestamps */
UTI_TimevalToInt64(&our_ref_time, &message.reference_ts);
UTI_TimevalToInt64(&our_ref_time, &message.reference_ts, 0);
/* Originate - this comes from the last packet the source sent us */
message.originate_ts = *orig_ts;
@@ -467,7 +467,10 @@ transmit_packet(NTP_Mode my_mode, /* The mode this machine wants to be */
This timestamp will have been adjusted so that it will now look to
the source like we have been running on our latest estimate of
frequency all along */
UTI_TimevalToInt64(local_rx, &message.receive_ts);
UTI_TimevalToInt64(local_rx, &message.receive_ts, 0);
/* Prepare random bits which will be added to the transmit timestamp. */
ts_fuzz = UTI_GetNTPTsFuzz(message.precision);
/* Transmit - this our local time right now! Also, we might need to
store this for our own use later, next time we receive a message
@@ -481,7 +484,7 @@ transmit_packet(NTP_Mode my_mode, /* The mode this machine wants to be */
take to generate the authentication data. */
local_transmit.tv_usec += KEY_GetAuthDelay(key_id);
UTI_NormaliseTimeval(&local_transmit);
UTI_TimevalToInt64(&local_transmit, &message.transmit_ts);
UTI_TimevalToInt64(&local_transmit, &message.transmit_ts, ts_fuzz);
auth_len = KEY_GenerateAuth(key_id, (unsigned char *) &message,
offsetof(NTP_Packet, auth_keyid),
@@ -492,7 +495,7 @@ transmit_packet(NTP_Mode my_mode, /* The mode this machine wants to be */
sizeof (message.auth_keyid) + auth_len);
}
} else {
UTI_TimevalToInt64(&local_transmit, &message.transmit_ts);
UTI_TimevalToInt64(&local_transmit, &message.transmit_ts, ts_fuzz);
NIO_SendNormalPacket(&message, where_to);
}