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dns-suite.js
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fixed a bug in message compression pointer handling

This commit is contained in:
tigerbot 2017-05-30 16:18:48 -06:00
parent a295f9c3e7
commit a09dd27c7d
3 changed files with 73 additions and 12 deletions
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26
dns.unpack-labels.js
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@ -29,18 +29,19 @@ exports.DNS_UNPACK_LABELS = function (ui8, ptr, q) {
break; break;
} }
if (0xc0 === len) { // Handle message compression pointers. See 4.1.4 of RFC1035 for details.
var cpptr = ui8[total + 1]; if (len >= 0xc0) {
var cpptr = ((ui8[total] & 0x3f) << 8) | ui8[total + 1];
// we're not coming back! // We're not coming back, so if this is the first time we're following one of
ptr = cpptr; // these pointers we up the byteLength to mark the pointer as part of the label
if (!q.cpcount) { if (!q.cpcount) {
q.byteLength += 2; // cp and len q.byteLength += 2; // cp and len
} }
q.cpcount += 1; q.cpcount += 1;
// recursion // recursion
return exports.DNS_UNPACK_LABELS(ui8, ptr, q); return exports.DNS_UNPACK_LABELS(ui8, cpptr, q);
} }
//str.length = 0; // fast empty array //str.length = 0; // fast empty array
@ -51,27 +52,28 @@ exports.DNS_UNPACK_LABELS = function (ui8, ptr, q) {
); );
} }
// Advance the pointer to after the length indicator, then read the string in.
total += 1;
for (i = 0; i < len; i += 1) { for (i = 0; i < len; i += 1) {
total += 1;
// TODO check url-allowable characters // TODO check url-allowable characters
label.push(String.fromCharCode(ui8[total])); label.push(String.fromCharCode(ui8[total]));
total += 1;
} }
if (label.length) { if (label.length) {
q.labels.push(label.join('')); q.labels.push(label.join(''));
} }
total += 1; // It is important this be done every time, so that if we run into a message compression
// pointer later we still have a record of what was consumed before that.
if (0 === q.cpcount) {
q.byteLength = total - ptr;
}
} while (0 !== len && undefined !== len); } while (0 !== len && undefined !== len);
//str.pop(); // remove trailing '.' //str.pop(); // remove trailing '.'
q.name = q.labels.join('.'); q.name = q.labels.join('.');
if (0 === q.cpcount) {
q.byteLength = total - ptr;
}
return q; return q;
}; };

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test/fixtures/canone30522.local.bin vendored Normal file
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59
test/fixtures/canone30522.local.js vendored Normal file
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@ -0,0 +1,59 @@
module.exports = {
"header": {
"id": 0,
"qr": 1,
"opcode": 0,
"aa": 0,
"tc": 0,
"rd": 0,
"ra": 0,
"res1": 0,
"res2": 0,
"res3": 0,
"rcode": 0
},
"question": [],
"answer": [
{
"name": "_pdl-datastream._tcp.local",
"type": 12,
"class": 1,
"ttl": 255,
"data": "Canon MF620C Series._pdl-datastream._tcp.local"
}
],
"additional": [
{
"name": "Canone30522.local",
"type": 1,
"class": 32769,
"ttl": 255,
},
{
"name": "Canon MF620C Series._pdl-datastream._tcp.local",
"type": 33,
"class": 32769,
"ttl": 255,
},
{
"name": "Canon MF620C Series._pdl-datastream._tcp.local",
"type": 16,
"class": 32769,
"ttl": 255,
},
{
"name": "Canone30522.local",
"type": 47,
"class": 32769,
"ttl": 255,
},
{
"name": "Canon MF620C Series._pdl-datastream._tcp.local",
"type": 47,
"class": 32769,
"ttl": 255,
}
],
"authority": [],
"edns_options": []
};