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dns-suite.js
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tried commenting out some code from befferconsumer to trace down more of the problem

This commit is contained in:
Daplie 2017-01-14 10:08:07 -07:00
parent 3353d096ae
commit fc6aee5ddc
3 changed files with 39 additions and 12 deletions
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31
howto.md
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@ -15,7 +15,7 @@ How to duplicate DNS crash:
Then in another terminal enter: Then in another terminal enter:
``` ```
dig @224.0.0.251 -p 5353 -t PTR _cloud._tcp.local >> dig @224.0.0.251 -p 5353 -t PTR _cloud._tcp.local
``` ```
The listener then crashes with an output of: The listener then crashes with an output of:
@ -39,11 +39,38 @@ Error: Buffer overflow
at Object.module.exports.respond (/home/daplie/dns_test/cloud-respond.js:10:11) at Object.module.exports.respond (/home/daplie/dns_test/cloud-respond.js:10:11)
``` ```
After commenting out lines 45-53 in dns_test/node_modules/dns-js/lib/bufferconsumer.js
and rerunning the previous commands, the result is a new error:
```
START DNS PACKET
buffer.js:829
throw new RangeError('Index out of range');
^
RangeError: Index out of range
at checkOffset (buffer.js:829:11)
at Buffer.readUInt8 (buffer.js:867:5)
at BufferConsumer.byte (/home/daplie/dns_test/node_modules/dns-js/lib/bufferconsumer.js:67:22)
at BufferConsumer.name (/home/daplie/dns_test/node_modules/dns-js/lib/bufferconsumer.js:120:14)
at Function.DNSRecord.parse (/home/daplie/dns_test/node_modules/dns-js/lib/dnsrecord.js:187:14)
at /home/daplie/dns_test/node_modules/dns-js/lib/dnspacket.js:164:30
at Array.forEach (native)
at Function.DNSPacket.parse (/home/daplie/dns_test/node_modules/dns-js/lib/dnspacket.js:159:17)
at /home/daplie/dns_test/cloud-respond.js:86:31
at Array.forEach (native)
```
which is located in the node.js buffer module. The API is [here](https://nodejs.org/api/buffer.html).
When can a Buffer overflow problem occur in js?
How to print out hex values of the DNS message? What are the possible problems?
How to print out hex values of the DNS message in node.js?
```javascript ```javascript
socket.on('message', function (message, rinfo) { socket.on('message', function (message, rinfo) {

2
listen.js
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@ -15,7 +15,7 @@ socket.on('message', function (message, rinfo) {
console.log('Received %d bytes from %s:%d\n', console.log('Received %d bytes from %s:%d\n',
message.length, rinfo.address, rinfo.port); message.length, rinfo.address, rinfo.port);
//console.log(msg.toString('utf8')); //console.log(msg.toString('utf8'));
buf.forEach parseInt(byte.toString('hex'), 16).toString(2); message.forEach(parseInt(byte.toString('hex'), 16).toString(2));
console.log(message.toString('hex')); console.log(message.toString('hex'));
var packets; var packets;

18
node_modules/dns-js/lib/bufferconsumer.js generated vendored
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@ -42,15 +42,15 @@ BufferConsumer.prototype.slice = function (length) {
return v; return v;
} }
else { else {
if ((this._offset + length) > this.length) { // if ((this._offset + length) > this.length) {
debug('Buffer owerflow. Slice beyond buffer.', { // debug('Buffer owerflow. Slice beyond buffer.', {
offset: this._offset, // offset: this._offset,
length: length, // length: length,
bufferLength: this.length // bufferLength: this.length
}); // });
debug('so far', this); // debug('so far', this);
throw new Error('Buffer overflow'); // throw new Error('Buffer overflow');
} // }
v = this.buffer.slice(this._offset, this._offset + length); v = this.buffer.slice(this._offset, this._offset + length);
this._offset += length; this._offset += length;
return v; return v;