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util: rework timestamp fuzzing

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Use UTI_GetRandomBytes() instead of random() to generate random bits
below precision. Save the result in NTP_int64 in the network order and
allow precision in the full range from -32 to 32. With precision 32
the fuzzing now makes the timestamp completely random and can be used to
hide the time.
This commit is contained in:
Miroslav Lichvar
2015-11-10 17:26:59 +01:00
parent 6199a89170
commit 116c697282
3 changed files with 37 additions and 27 deletions
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17
ntp_core.c
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@@ -286,8 +286,8 @@ do_time_checks(void)
NTP_int64 ntv1, ntv2;
int r;
UTI_TimevalToInt64(&tv1, &ntv1, 0);
UTI_TimevalToInt64(&tv2, &ntv2, 0);
UTI_TimevalToInt64(&tv1, &ntv1, NULL);
UTI_TimevalToInt64(&tv2, &ntv2, NULL);
UTI_Int64ToTimeval(&ntv1, &tv1);
UTI_Int64ToTimeval(&ntv2, &tv2);
@@ -783,11 +783,12 @@ transmit_packet(NTP_Mode my_mode, /* The mode this machine wants to be */
NTP_Packet message;
int leap, auth_len, length, ret;
struct timeval local_receive, local_transmit;
NTP_int64 ts_fuzz;
/* Parameters read from reference module */
int are_we_synchronised, our_stratum, smooth_time;
NTP_Leap leap_status;
uint32_t our_ref_id, ts_fuzz;
uint32_t our_ref_id;
struct timeval our_ref_time;
double our_root_delay, our_root_dispersion, smooth_offset;
@@ -855,7 +856,7 @@ transmit_packet(NTP_Mode my_mode, /* The mode this machine wants to be */
/* Now fill in timestamps */
UTI_TimevalToInt64(&our_ref_time, &message.reference_ts, 0);
UTI_TimevalToInt64(&our_ref_time, &message.reference_ts, NULL);
/* Originate - this comes from the last packet the source sent us */
message.originate_ts = *orig_ts;
@@ -864,10 +865,10 @@ 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_receive, &message.receive_ts, 0);
UTI_TimevalToInt64(&local_receive, &message.receive_ts, NULL);
/* Prepare random bits which will be added to the transmit timestamp. */
ts_fuzz = UTI_GetNTPTsFuzz(message.precision);
UTI_GetInt64Fuzz(&ts_fuzz, 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
@@ -885,7 +886,7 @@ 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, ts_fuzz);
UTI_TimevalToInt64(&local_transmit, &message.transmit_ts, &ts_fuzz);
auth_len = KEY_GenerateAuth(key_id, (unsigned char *) &message,
offsetof(NTP_Packet, auth_keyid),
@@ -905,7 +906,7 @@ transmit_packet(NTP_Mode my_mode, /* The mode this machine wants to be */
message.auth_keyid = 0;
length += sizeof (message.auth_keyid);
}
UTI_TimevalToInt64(&local_transmit, &message.transmit_ts, ts_fuzz);
UTI_TimevalToInt64(&local_transmit, &message.transmit_ts, &ts_fuzz);
}
ret = NIO_SendPacket(&message, where_to, from, length);