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Merged
WyriHaximus merged 2 commits into from
Nov 11, 2018
Merged

Reject parsing malformed record data and incomplete DNS response messages #117

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a57d3d9
Reject parsing incomplete DNS response messages
clue Nov 2, 2018
901ba58
Reject malformed record data in DNS response messages
clue Nov 3, 2018
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139 changes: 76 additions & 63 deletions src/Protocol/Parser.php
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Original file line number Diff line number Diff line change
Expand Up @@ -66,7 +66,7 @@ private function parse($data, Message $message)

public function parseHeader(Message $message)
{
if (strlen($message->data) < 12) {
if (!isset($message->data[12 - 1])) {
return;
}

Expand Down Expand Up @@ -97,19 +97,11 @@ public function parseHeader(Message $message)

public function parseQuestion(Message $message)
{
if (strlen($message->data) < 2) {
return;
}

$consumed = $message->consumed;

list($labels, $consumed) = $this->readLabels($message->data, $consumed);

if (null === $labels) {
return;
}

if (strlen($message->data) - $consumed < 4) {
if ($labels === null || !isset($message->data[$consumed + 4 - 1])) {
return;
}

Expand All @@ -133,19 +125,11 @@ public function parseQuestion(Message $message)

public function parseAnswer(Message $message)
{
if (strlen($message->data) < 2) {
return;
}

$consumed = $message->consumed;

list($labels, $consumed) = $this->readLabels($message->data, $consumed);
list($name, $consumed) = $this->readDomain($message->data, $consumed);

if (null === $labels) {
return;
}

if (strlen($message->data) - $consumed < 10) {
if ($name === null || !isset($message->data[$consumed + 10 - 1])) {
return;
}

Expand All @@ -163,68 +147,85 @@ public function parseAnswer(Message $message)
list($rdLength) = array_values(unpack('n', substr($message->data, $consumed, 2)));
$consumed += 2;

$rdata = null;
if (!isset($message->data[$consumed + $rdLength - 1])) {
return;
}

if (Message::TYPE_A === $type || Message::TYPE_AAAA === $type) {
$ip = substr($message->data, $consumed, $rdLength);
$consumed += $rdLength;
$rdata = null;
$expected = $consumed + $rdLength;

$rdata = inet_ntop($ip);
if (Message::TYPE_A === $type) {
if ($rdLength === 4) {
$rdata = inet_ntop(substr($message->data, $consumed, $rdLength));
$consumed += $rdLength;
}
} elseif (Message::TYPE_AAAA === $type) {
if ($rdLength === 16) {
$rdata = inet_ntop(substr($message->data, $consumed, $rdLength));
$consumed += $rdLength;
}
} elseif (Message::TYPE_CNAME === $type || Message::TYPE_PTR === $type || Message::TYPE_NS === $type) {
list($bodyLabels, $consumed) = $this->readLabels($message->data, $consumed);

$rdata = implode('.', $bodyLabels);
list($rdata, $consumed) = $this->readDomain($message->data, $consumed);
} elseif (Message::TYPE_TXT === $type) {
$rdata = array();
$remaining = $rdLength;
while ($remaining) {
while ($consumed < $expected) {
$len = ord($message->data[$consumed]);
$rdata[] = substr($message->data, $consumed + 1, $len);
$rdata[] = (string)substr($message->data, $consumed + 1, $len);
$consumed += $len + 1;
$remaining -= $len + 1;
}
} elseif (Message::TYPE_MX === $type) {
list($priority) = array_values(unpack('n', substr($message->data, $consumed, 2)));
list($bodyLabels, $consumed) = $this->readLabels($message->data, $consumed + 2);

$rdata = array(
'priority' => $priority,
'target' => implode('.', $bodyLabels)
);
if ($rdLength > 2) {
list($priority) = array_values(unpack('n', substr($message->data, $consumed, 2)));
list($target, $consumed) = $this->readDomain($message->data, $consumed + 2);

$rdata = array(
'priority' => $priority,
'target' => $target
);
}
} elseif (Message::TYPE_SRV === $type) {
list($priority, $weight, $port) = array_values(unpack('n*', substr($message->data, $consumed, 6)));
list($bodyLabels, $consumed) = $this->readLabels($message->data, $consumed + 6);

$rdata = array(
'priority' => $priority,
'weight' => $weight,
'port' => $port,
'target' => implode('.', $bodyLabels)
);
if ($rdLength > 6) {
list($priority, $weight, $port) = array_values(unpack('n*', substr($message->data, $consumed, 6)));
list($target, $consumed) = $this->readDomain($message->data, $consumed + 6);

$rdata = array(
'priority' => $priority,
'weight' => $weight,
'port' => $port,
'target' => $target
);
}
} elseif (Message::TYPE_SOA === $type) {
list($primaryLabels, $consumed) = $this->readLabels($message->data, $consumed);
list($mailLabels, $consumed) = $this->readLabels($message->data, $consumed);
list($serial, $refresh, $retry, $expire, $minimum) = array_values(unpack('N*', substr($message->data, $consumed, 20)));
$consumed += 20;

$rdata = array(
'mname' => implode('.', $primaryLabels),
'rname' => implode('.', $mailLabels),
'serial' => $serial,
'refresh' => $refresh,
'retry' => $retry,
'expire' => $expire,
'minimum' => $minimum
);
list($mname, $consumed) = $this->readDomain($message->data, $consumed);
list($rname, $consumed) = $this->readDomain($message->data, $consumed);

if ($mname !== null && $rname !== null && isset($message->data[$consumed + 20 - 1])) {
list($serial, $refresh, $retry, $expire, $minimum) = array_values(unpack('N*', substr($message->data, $consumed, 20)));
$consumed += 20;

$rdata = array(
'mname' => $mname,
'rname' => $rname,
'serial' => $serial,
'refresh' => $refresh,
'retry' => $retry,
'expire' => $expire,
'minimum' => $minimum
);
}
} else {
// unknown types simply parse rdata as an opaque binary string
$rdata = substr($message->data, $consumed, $rdLength);
$consumed += $rdLength;
}

// ensure parsing record data consumes expact number of bytes indicated in record length
if ($consumed !== $expected || $rdata === null) {
return;
}

$message->consumed = $consumed;

$name = implode('.', $labels);
$record = new Record($name, $type, $class, $ttl, $rdata);

$message->answers[] = $record;
Expand All @@ -236,6 +237,17 @@ public function parseAnswer(Message $message)
return $message;
}

private function readDomain($data, $consumed)
{
list ($labels, $consumed) = $this->readLabels($data, $consumed);

if ($labels === null) {
return array(null, null);
}

return array(implode('.', $labels), $consumed);
}

private function readLabels($data, $consumed)
{
$labels = array();
Expand All @@ -262,6 +274,7 @@ private function readLabels($data, $consumed)

$consumed += 2;
list($newLabels) = $this->readLabels($data, $offset);

if ($newLabels === null) {
return array(null, null);
}
Expand Down
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