rOACCT/node_modules/dns-packet5d92ed19fb80paginated-inlines
README.md
dns-packet
   
An abstract-encoding compliant module for encoding / decoding DNS packets. Lifted out of multicast-dns as a separate module.
npm install dns-packet
UDP Usage
js
const dnsPacket = require('dns-packet')
const dgram = require('dgram')
const socket = dgram.createSocket('udp4')
const buf = dnsPacket.encode({
type: 'query',
id: 1,
flags: dnsPacket.RECURSION_DESIRED,
questions: [{
type: 'A',
name: 'google.com'
}]
})
socket.on('message', message => {
console.log(dnsPacket.decode(message)) // prints out a response from google dns
})
socket.send(buf, 0, buf.length, 53, '8.8.8.8')Also see [the UDP example](examples/udp.js).
TCP, TLS, HTTPS
While DNS has traditionally been used over a datagram transport, it is increasingly being carried over TCP for larger responses commonly including DNSSEC responses and TLS or HTTPS for enhanced security. See below examples on how to use dns-packet to wrap DNS packets in these protocols:
- [TCP](examples/tcp.js)
- [DNS over TLS](examples/tls.js)
- [DNS over HTTPS](examples/doh.js)
API
var buf = packets.encode(packet, [buf], [offset])
Encodes a DNS packet into a buffer containing a UDP payload.
var packet = packets.decode(buf, [offset])
Decode a DNS packet from a buffer containing a UDP payload.
var buf = packets.streamEncode(packet, [buf], [offset])
Encodes a DNS packet into a buffer containing a TCP payload.
var packet = packets.streamDecode(buf, [offset])
Decode a DNS packet from a buffer containing a TCP payload.
var len = packets.encodingLength(packet)
Returns how many bytes are needed to encode the DNS packet
Packets
Packets look like this
js
{
type: 'query|response',
id: optionalIdNumber,
flags: optionalBitFlags,
questions: [...],
answers: [...],
additionals: [...],
authorities: [...]
}The bit flags available are
js packet.RECURSION_DESIRED packet.RECURSION_AVAILABLE packet.TRUNCATED_RESPONSE packet.AUTHORITATIVE_ANSWER packet.AUTHENTIC_DATA packet.CHECKING_DISABLED
To use more than one flag bitwise-or them together
js var flags = packet.RECURSION_DESIRED | packet.RECURSION_AVAILABLE
And to check for a flag use bitwise-and
js var isRecursive = message.flags & packet.RECURSION_DESIRED
A question looks like this
js
{
type: 'A', // or SRV, AAAA, etc
class: 'IN', // one of IN, CS, CH, HS, ANY. Default: IN
name: 'google.com' // which record are you looking for
}And an answer, additional, or authority looks like this
js
{
type: 'A', // or SRV, AAAA, etc
class: 'IN', // one of IN, CS, CH, HS
name: 'google.com', // which name is this record for
ttl: optionalTimeToLiveInSeconds,
(record specific data, see below)
}Supported record types
A
js
{
data: 'IPv4 address' // fx 127.0.0.1
}AAAA
js
{
data: 'IPv6 address' // fx fe80::1
}CAA
js
{
flags: 128, // octet
tag: 'issue|issuewild|iodef',
value: 'ca.example.net',
issuerCritical: false
}CNAME
js
{
data: 'cname.to.another.record'
}DNAME
js
{
data: 'dname.to.another.record'
}DNSKEY
js
{
flags: 257, // 16 bits
algorithm: 1, // octet
key: Buffer
}DS
js
{
keyTag: 12345,
algorithm: 8,
digestType: 1,
digest: Buffer
}HINFO
js
{
data: {
cpu: 'cpu info',
os: 'os info'
}
}MX
js
{
preference: 10,
exchange: 'mail.example.net'
}NS
js
{
data: nameServer
}NSEC
js
{
nextDomain: 'a.domain',
rrtypes: ['A', 'TXT', 'RRSIG']
}NSEC3
js
{
algorithm: 1,
flags: 0,
iterations: 2,
salt: Buffer,
nextDomain: Buffer, // Hashed per RFC5155
rrtypes: ['A', 'TXT', 'RRSIG']
}NULL
js
{
data: Buffer('any binary data')
}OPT
EDNS0 options.
js
{
type: 'OPT',
name: '.',
udpPayloadSize: 4096,
flags: packet.DNSSEC_OK,
options: [{
// pass in any code/data for generic EDNS0 options
code: 12,
data: Buffer.alloc(31)
}, {
// Several EDNS0 options have enhanced support
code: 'PADDING',
length: 31,
}, {
code: 'CLIENT_SUBNET',
family: 2, // 1 for IPv4, 2 for IPv6
sourcePrefixLength: 64, // used to truncate IP address
scopePrefixLength: 0,
ip: 'fe80::',
}, {
code: 'TCP_KEEPALIVE',
timeout: 150 // increments of 100ms. This means 15s.
}, {
code: 'KEY_TAG',
tags: [1, 2, 3],
}]
}The options PADDING, CLIENT_SUBNET, TCP_KEEPALIVE and KEY_TAG support enhanced de/encoding. See optionscodes.js for all supported option codes. If the data property is present on a option, it takes precedence. On decoding, data will always be defined.
PTR
js
{
data: 'points.to.another.record'
}RP
js
{
mbox: 'admin.example.com',
txt: 'txt.example.com'
}SSHFP
js
{
algorithm: 1,
hash: 1,
fingerprint: 'A108C9F834354D5B37AF988141C9294822F5BC00'
}
`RRSIG
js
{
typeCovered: 'A',
algorithm: 8,
labels: 1,
originalTTL: 3600,
expiration: timestamp,
inception: timestamp,
keyTag: 12345,
signersName: 'a.name',
signature: Buffer
}SOA
js
{
data:
{
mname: domainName,
rname: mailbox,
serial: zoneSerial,
refresh: refreshInterval,
retry: retryInterval,
expire: expireInterval,
minimum: minimumTTL
}
}SRV
js
{
data: {
port: servicePort,
target: serviceHostName,
priority: optionalServicePriority,
weight: optionalServiceWeight
}
}TXT
js
{
data: 'text' || Buffer || [ Buffer || 'text' ]
}When encoding, scalar values are converted to an array and strings are converted to UTF-8 encoded Buffers. When decoding, the return value will always be an array of Buffer.
If you need another record type, open an issue and we'll try to add it.
License
MIT