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validate NTP responses (fixes #3515)

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* purge old (not yet processes) NTP responses
* validate server responses before updating WLED time
* purge receive buffer when package is rejected (avoids mem leak on esp32)
This commit is contained in:
Frank 2023-11-20 12:24:34 +01:00
parent 75f6a53269
commit 1e29d9463e
2 changed files with 28 additions and 2 deletions
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3
wled00/const.h
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@ -375,7 +375,8 @@
#define SUBPAGE_JS 254
#define SUBPAGE_WELCOME 255
#define NTP_PACKET_SIZE 48
#define NTP_PACKET_SIZE 48 // size of NTP recive buffer
#define NTP_MIN_PACKET_SIZE 48 // min expected size - NTP v4 allows for "extended information" appended to the standard fields
//maximum number of rendered LEDs - this does not have to match max. physical LEDs, e.g. if there are virtual busses
#ifndef MAX_LEDS

27
wled00/ntp.cpp
View File

@ -199,6 +199,9 @@ void handleNetworkTime()
{
if (millis() - ntpPacketSentTime > 10000)
{
#ifdef ARDUINO_ARCH_ESP32 // I had problems using udp.flush() on 8266
while (ntpUdp.parsePacket() > 0) ntpUdp.flush(); // flush any existing packets
#endif
sendNTPPacket();
ntpPacketSentTime = millis();
}
@ -239,16 +242,38 @@ void sendNTPPacket()
ntpUdp.endPacket();
}
static bool isValidNtpResponse(byte * ntpPacket) {
// Perform a few validity checks on the packet
// based on https://github.com/taranais/NTPClient/blob/master/NTPClient.cpp
if((ntpPacket[0] & 0b11000000) == 0b11000000) return false; //reject LI=UNSYNC
// if((ntpPacket[0] & 0b00111000) >> 3 < 0b100) return false; //reject Version < 4
if((ntpPacket[0] & 0b00000111) != 0b100) return false; //reject Mode == Server
if((ntpPacket[1] < 1) || (ntpPacket[1] > 15)) return false; //reject invalid Stratum
if( ntpPacket[16] == 0 && ntpPacket[17] == 0 &&
ntpPacket[18] == 0 && ntpPacket[19] == 0 &&
ntpPacket[20] == 0 && ntpPacket[21] == 0 &&
ntpPacket[22] == 0 && ntpPacket[23] == 0) //reject ReferenceTimestamp == 0
return false;
return true;
}
bool checkNTPResponse()
{
int cb = ntpUdp.parsePacket();
if (!cb) return false;
if (cb < NTP_MIN_PACKET_SIZE) {
#ifdef ARDUINO_ARCH_ESP32 // I had problems using udp.flush() on 8266
if (cb > 0) ntpUdp.flush(); // this avoids memory leaks on esp32
#endif
return false;
}
uint32_t ntpPacketReceivedTime = millis();
DEBUG_PRINT(F("NTP recv, l="));
DEBUG_PRINTLN(cb);
byte pbuf[NTP_PACKET_SIZE];
ntpUdp.read(pbuf, NTP_PACKET_SIZE); // read the packet into the buffer
if (!isValidNtpResponse(pbuf)) return false; // verify we have a valid response to client
Toki::Time arrived = toki.fromNTP(pbuf + 32);
Toki::Time departed = toki.fromNTP(pbuf + 40);