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Add packet validity checks #4

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Jun 4, 2021
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Add packet validity checks #4

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73 changes: 50 additions & 23 deletions src/NTPClient_Generic_Impl.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -58,40 +58,67 @@ void NTPClient::begin(int port)
this->_udpSetup = true;
}

bool NTPClient::checkResponse()
// Perform some validity checks on the packet
// https://datatracker.ietf.org/doc/html/rfc4330#section-4
// Check length before calling
static bool isValid(byte const *ntpPacket)
{
unsigned long highWord = word(ntpPacket[16], ntpPacket[17]);
unsigned long lowWord = word(ntpPacket[18], ntpPacket[19]);
unsigned long refTimeInt = highWord << 16 | lowWord;
highWord = word(ntpPacket[20], ntpPacket[21]);
lowWord = word(ntpPacket[22], ntpPacket[23]);
unsigned long refTimeFrac = highWord << 16 | lowWord;

byte leapIndicator = ((ntpPacket[0] & 0b11000000) >> 6);
byte version = ((ntpPacket[0] & 0b00111000) >> 3);
byte stratum = ntpPacket[1];

return
(
(leapIndicator != 3) && // LI != UNSYNC
(version >= 1) &&
(stratum >= 1) &&
(stratum <= 15) &&
((refTimeInt != 0) || (refTimeFrac != 0))
);
}

bool NTPClient::checkResponse()
{
if (this->_udp->parsePacket())
{
this->_lastUpdate = millis();
this->_lastRequest = 0; // no outstanding request
this->_udp->read(this->_packetBuffer, NTP_PACKET_SIZE);
int numBytesRead = this->_udp->read(this->_packetBuffer, NTP_PACKET_SIZE);

unsigned long highWord = word(this->_packetBuffer[40], this->_packetBuffer[41]);
unsigned long lowWord = word(this->_packetBuffer[42], this->_packetBuffer[43]);

// combine the four bytes (two words) into a long integer
// this is NTP time (seconds since Jan 1 1900):
unsigned long secsSince1900 = highWord << 16 | lowWord;
if ((numBytesRead == NTP_PACKET_SIZE) && isValid(this->_packetBuffer))
{
this->_lastUpdate = millis();

this->_currentEpoc = secsSince1900 - SEVENTYYEARS;
unsigned long highWord = word(this->_packetBuffer[40], this->_packetBuffer[41]);
unsigned long lowWord = word(this->_packetBuffer[42], this->_packetBuffer[43]);

highWord = word(this->_packetBuffer[44], this->_packetBuffer[45]);
lowWord = word(this->_packetBuffer[46], this->_packetBuffer[47]);
this->_currentFraction = highWord << 16 | lowWord;
// combine the four bytes (two words) into a long integer
// this is NTP time (seconds since Jan 1 1900):
unsigned long secsSince1900 = highWord << 16 | lowWord;

// if the user has set a callback function for when the time is updated, call it
if (_updateCallback)
{
_updateCallback(this);
}
this->_currentEpoc = secsSince1900 - SEVENTYYEARS;

return true;
}
else
{
return false;
highWord = word(this->_packetBuffer[44], this->_packetBuffer[45]);
lowWord = word(this->_packetBuffer[46], this->_packetBuffer[47]);
this->_currentFraction = highWord << 16 | lowWord;

// if the user has set a callback function for when the time is updated, call it
if (_updateCallback)
{
_updateCallback(this);
}

return true;
}
}

return false;
}

bool NTPClient::forceUpdate()
Expand Down
73 changes: 50 additions & 23 deletions src_cpp/NTPClient_Generic.cpp
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -58,40 +58,67 @@ void NTPClient::begin(int port)
this->_udpSetup = true;
}

bool NTPClient::checkResponse()
// Perform some validity checks on the packet
// https://datatracker.ietf.org/doc/html/rfc4330#section-4
// Check length before calling
static bool isValid(byte const *ntpPacket)
{
unsigned long highWord = word(ntpPacket[16], ntpPacket[17]);
unsigned long lowWord = word(ntpPacket[18], ntpPacket[19]);
unsigned long refTimeInt = highWord << 16 | lowWord;
highWord = word(ntpPacket[20], ntpPacket[21]);
lowWord = word(ntpPacket[22], ntpPacket[23]);
unsigned long refTimeFrac = highWord << 16 | lowWord;

byte leapIndicator = ((ntpPacket[0] & 0b11000000) >> 6);
byte version = ((ntpPacket[0] & 0b00111000) >> 3);
byte stratum = ntpPacket[1];

return
(
(leapIndicator != 3) && // LI != UNSYNC
(version >= 1) &&
(stratum >= 1) &&
(stratum <= 15) &&
((refTimeInt != 0) || (refTimeFrac != 0))
);
}

bool NTPClient::checkResponse()
{
if (this->_udp->parsePacket())
{
this->_lastUpdate = millis();
this->_lastRequest = 0; // no outstanding request
this->_udp->read(this->_packetBuffer, NTP_PACKET_SIZE);
int numBytesRead = this->_udp->read(this->_packetBuffer, NTP_PACKET_SIZE);

unsigned long highWord = word(this->_packetBuffer[40], this->_packetBuffer[41]);
unsigned long lowWord = word(this->_packetBuffer[42], this->_packetBuffer[43]);

// combine the four bytes (two words) into a long integer
// this is NTP time (seconds since Jan 1 1900):
unsigned long secsSince1900 = highWord << 16 | lowWord;
if ((numBytesRead == NTP_PACKET_SIZE) && isValid(this->_packetBuffer))
{
this->_lastUpdate = millis();

this->_currentEpoc = secsSince1900 - SEVENTYYEARS;
unsigned long highWord = word(this->_packetBuffer[40], this->_packetBuffer[41]);
unsigned long lowWord = word(this->_packetBuffer[42], this->_packetBuffer[43]);

highWord = word(this->_packetBuffer[44], this->_packetBuffer[45]);
lowWord = word(this->_packetBuffer[46], this->_packetBuffer[47]);
this->_currentFraction = highWord << 16 | lowWord;
// combine the four bytes (two words) into a long integer
// this is NTP time (seconds since Jan 1 1900):
unsigned long secsSince1900 = highWord << 16 | lowWord;

// if the user has set a callback function for when the time is updated, call it
if (_updateCallback)
{
_updateCallback(this);
}
this->_currentEpoc = secsSince1900 - SEVENTYYEARS;

return true;
}
else
{
return false;
highWord = word(this->_packetBuffer[44], this->_packetBuffer[45]);
lowWord = word(this->_packetBuffer[46], this->_packetBuffer[47]);
this->_currentFraction = highWord << 16 | lowWord;

// if the user has set a callback function for when the time is updated, call it
if (_updateCallback)
{
_updateCallback(this);
}

return true;
}
}

return false;
}

bool NTPClient::forceUpdate()
Expand Down
73 changes: 50 additions & 23 deletions src_h/NTPClient_Generic_Impl.h
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -58,40 +58,67 @@ void NTPClient::begin(int port)
this->_udpSetup = true;
}

bool NTPClient::checkResponse()
// Perform some validity checks on the packet
// https://datatracker.ietf.org/doc/html/rfc4330#section-4
// Check length before calling
static bool isValid(byte const *ntpPacket)
{
unsigned long highWord = word(ntpPacket[16], ntpPacket[17]);
unsigned long lowWord = word(ntpPacket[18], ntpPacket[19]);
unsigned long refTimeInt = highWord << 16 | lowWord;
highWord = word(ntpPacket[20], ntpPacket[21]);
lowWord = word(ntpPacket[22], ntpPacket[23]);
unsigned long refTimeFrac = highWord << 16 | lowWord;

byte leapIndicator = ((ntpPacket[0] & 0b11000000) >> 6);
byte version = ((ntpPacket[0] & 0b00111000) >> 3);
byte stratum = ntpPacket[1];

return
(
(leapIndicator != 3) && // LI != UNSYNC
(version >= 1) &&
(stratum >= 1) &&
(stratum <= 15) &&
((refTimeInt != 0) || (refTimeFrac != 0))
);
}

bool NTPClient::checkResponse()
{
if (this->_udp->parsePacket())
{
this->_lastUpdate = millis();
this->_lastRequest = 0; // no outstanding request
this->_udp->read(this->_packetBuffer, NTP_PACKET_SIZE);
int numBytesRead = this->_udp->read(this->_packetBuffer, NTP_PACKET_SIZE);

unsigned long highWord = word(this->_packetBuffer[40], this->_packetBuffer[41]);
unsigned long lowWord = word(this->_packetBuffer[42], this->_packetBuffer[43]);

// combine the four bytes (two words) into a long integer
// this is NTP time (seconds since Jan 1 1900):
unsigned long secsSince1900 = highWord << 16 | lowWord;
if ((numBytesRead == NTP_PACKET_SIZE) && isValid(this->_packetBuffer))
{
this->_lastUpdate = millis();

this->_currentEpoc = secsSince1900 - SEVENTYYEARS;
unsigned long highWord = word(this->_packetBuffer[40], this->_packetBuffer[41]);
unsigned long lowWord = word(this->_packetBuffer[42], this->_packetBuffer[43]);

highWord = word(this->_packetBuffer[44], this->_packetBuffer[45]);
lowWord = word(this->_packetBuffer[46], this->_packetBuffer[47]);
this->_currentFraction = highWord << 16 | lowWord;
// combine the four bytes (two words) into a long integer
// this is NTP time (seconds since Jan 1 1900):
unsigned long secsSince1900 = highWord << 16 | lowWord;

// if the user has set a callback function for when the time is updated, call it
if (_updateCallback)
{
_updateCallback(this);
}
this->_currentEpoc = secsSince1900 - SEVENTYYEARS;

return true;
}
else
{
return false;
highWord = word(this->_packetBuffer[44], this->_packetBuffer[45]);
lowWord = word(this->_packetBuffer[46], this->_packetBuffer[47]);
this->_currentFraction = highWord << 16 | lowWord;

// if the user has set a callback function for when the time is updated, call it
if (_updateCallback)
{
_updateCallback(this);
}

return true;
}
}

return false;
}

bool NTPClient::forceUpdate()
Expand Down