232 lines
3.3 KiB
Markdown
232 lines
3.3 KiB
Markdown
# dns-packet
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An [abstract-encoding](https://github.com/mafintosh/abstract-encoding) compliant module for encoding / decoding DNS packets.
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Lifted out of [multicast-dns](https://github.com/mafintosh/multicast-dns) as a separate module.
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```
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npm install dns-packet
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```
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[](https://travis-ci.org/mafintosh/dns-packet)
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## Usage
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``` js
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var packet = require('dns-packet')
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var dgram = require('dgram')
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var socket = dgram.createSocket('udp4')
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var buf = packet.encode({
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type: 'query',
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id: 1,
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flags: packet.RECURSION_DESIRED,
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questions: [{
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type: 'A',
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name: 'google.com'
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}]
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})
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socket.on('message', function (message) {
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console.log(packet.decode(message)) // prints out a response from google dns
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})
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socket.send(buf, 0, buf.length, 53, '8.8.8.8')
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```
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## API
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#### `var buf = packets.encode(packet, [buf], [offset])`
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Encodes a DNS packet into a buffer.
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#### `var packet = packets.decode(buf, [offset])`
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Decode a DNS packet from a buffer
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#### `var len = packets.encodingLength(packet)`
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Returns how many bytes are needed to encode the DNS packet
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## Packets
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Packets look like this
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``` js
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{
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type: 'query|response',
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id: optionalIdNumber,
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flags: optionalBitFlags,
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questions: [...],
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answers: [...],
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additionals: [...],
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authorities: [...]
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}
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```
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The bit flags available are
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``` js
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packet.RECURSION_DESIRED
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packet.RECURSION_AVAILABLE
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packet.TRUNCATED_RESPONSE
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packet.AUTHORITATIVE_ANSWER
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packet.AUTHENTIC_DATA
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packet.CHECKING_DISABLED
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```
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To use more than one flag bitwise-or them together
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``` js
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var flags = packet.RECURSION_DESIRED | packet.RECURSION_AVAILABLE
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```
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And to check for a flag use bitwise-and
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``` js
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var isRecursive = message.flags & packet.RECURSION_DESIRED
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```
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A question looks like this
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``` js
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{
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type: 'A', // or SRV, AAAA, etc
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name: 'google.com' // which record are you looking for
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}
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```
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And an answers, additional, or authority looks like this
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``` js
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{
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type: 'A', // or SRV, AAAA, etc
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name: 'google.com', // which name is this record for
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ttl: optionalTimeToLiveInSeconds,
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(record specific data, see below)
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}
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```
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Currently the different available records are
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#### `A`
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``` js
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{
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data: 'IPv4 address' // fx 127.0.0.1
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}
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```
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#### `AAAA`
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``` js
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{
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data: 'IPv6 address' // fx fe80::1
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}
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```
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#### `TXT`
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``` js
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{
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data: Buffer('some text')
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}
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```
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#### `NS`
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``` js
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{
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data: nameServer
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}
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```
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#### `NULL`
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``` js
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{
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data: Buffer('any binary data')
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}
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```
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#### `SOA`
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``` js
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{
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data:
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{
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mname: domainName,
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rname: mailbox,
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serial: zoneSerial,
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refresh: refreshInterval,
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retry: retryInterval,
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expire: expireInterval,
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minimum: minimumTTL
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}
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}
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```
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#### `SRV`
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``` js
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{
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data: {
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port: servicePort,
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target: serviceHostName,
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priority: optionalServicePriority,
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weight: optionalServiceWeight
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}
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}
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```
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#### `HINFO`
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``` js
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{
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data: {
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cpu: 'cpu info',
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os: 'os info'
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}
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}
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```
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#### `PTR`
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``` js
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{
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data: 'points.to.another.record'
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}
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```
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#### `CNAME`
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``` js
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{
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data: 'cname.to.another.record'
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}
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```
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#### `DNAME`
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``` js
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{
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data: 'dname.to.another.record'
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}
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```
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#### `CAA`
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``` js
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{
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flags: 128, // octet
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tag: 'issue|issuewild|iodef',
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value: 'ca.example.net'
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}
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```
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If you need another one, open an issue and we'll try to add it.
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## License
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MIT
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