148 lines
3.3 KiB
Markdown
148 lines
3.3 KiB
Markdown
mDNS howto Documentation
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=====
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How to create a JSON file with information about your project:
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```bash
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npm init
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```
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How to duplicate DNS crash:
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```
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>> cd ~/dns_test
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>> node listen.jss
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```
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Then in another terminal enter:
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```
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>> dig @224.0.0.251 -p 5353 -t PTR _cloud._tcp.local
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```
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The listener then crashes with an output of:
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```
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START DNS PACKET
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/home/daplie/dns_test/node_modules/dns-js/lib/bufferconsumer.js:52
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throw new Error('Buffer overflow')
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^
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Error: Buffer overflow
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at BufferConsumer.slice (/home/daplie/dns_test/node_modules/dns-js/lib/bufferconsumer.js:52:13)
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s at Function.DNSRecord.parse (/home/daplie/dns_test/node_modules/dns-js/lib/dnsrecord.js:237:46)
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at /home/daplie/dns_test/node_modules/dns-js/lib/dnspacket.js:164:30
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at Array.forEach (native)
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at Function.DNSPacket.parse (/home/daplie/dns_test/node_modules/dns-js/lib/dnspacket.js:159:17)
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at /home/daplie/dns_test/cloud-respond.js:86:31
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at Array.forEach (native)
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at /home/daplie/dns_test/cloud-respond.js:11:21
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at Array.forEach (native)
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at Object.module.exports.respond (/home/daplie/dns_test/cloud-respond.js:10:11)
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```
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After commenting out lines 45-53 in dns_test/node_modules/dns-js/lib/bufferconsumer.js
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and rerunning the previous commands, the result is a new error:
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```
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START DNS PACKET
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buffer.js:829
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throw new RangeError('Index out of range');
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^
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RangeError: Index out of range
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at checkOffset (buffer.js:829:11)
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at Buffer.readUInt8 (buffer.js:867:5)
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at BufferConsumer.byte (/home/daplie/dns_test/node_modules/dns-js/lib/bufferconsumer.js:67:22)
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at BufferConsumer.name (/home/daplie/dns_test/node_modules/dns-js/lib/bufferconsumer.js:120:14)
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at Function.DNSRecord.parse (/home/daplie/dns_test/node_modules/dns-js/lib/dnsrecord.js:187:14)
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at /home/daplie/dns_test/node_modules/dns-js/lib/dnspacket.js:164:30
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at Array.forEach (native)
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at Function.DNSPacket.parse (/home/daplie/dns_test/node_modules/dns-js/lib/dnspacket.js:159:17)
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at /home/daplie/dns_test/cloud-respond.js:86:31
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at Array.forEach (native)
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```
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which is located in the node.js buffer module. The API is [here](https://nodejs.org/api/buffer.html).
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However, the error we are working with will most likely be dealt with by parsing through the binary
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and putting it in a format that is acceptable to a custom buffer, since the current buffer.js does doesn't seem to do the trick.
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Using
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```javascript
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function pad(str, len, ch) {
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while (str.length < len) {
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str = ch + str;
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}
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return str;
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}
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```
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the binary output comes out as:
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```
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11100001
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10001000
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00000001
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00100000
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00000000
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00000001
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00000000
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00000000
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00000000
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00000000
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00000000
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00000001
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00000110
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01011111
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01100011
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01101100
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01101111
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01110101
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01100100
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00000100
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01011111
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01110100
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01100011
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01110000
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00000101
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01101100
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01101111
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01100011
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01100001
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01101100
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00000000
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00000000
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00001100
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00000000
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00000001
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00000000
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00000000
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00101001
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00010000
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00000000
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00000000
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00000000
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00000000
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00000000
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00000000
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00000000
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```
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What are the possible problems?
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How to print out hex values of the DNS message in node.js?
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```javascript
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socket.on('message', function (message, rinfo) {
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console.log('Received %d bytes from %s:%d\n',
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message.length, rinfo.address, rinfo.port);
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//console.log(msg.toString('utf8'));
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console.log(message.toString('hex'));
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```
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### Objective
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