Library dns
Simple DNS library supporting packet creation, encoding, decoding, and querying.
The most common interface to this module are the query and
reverse functions. query performs a DNS query,
and reverse prepares an ip address to have a reverse query
performed.
query takes two options - a domain name to look up and an
optional table of options. For more information on the options table,
see the documentation for query.
Example usage:
-- After this call, <code>statusis
true and result is "72.14.204.104"
local status, result = dns.query('www.google.ca')
-- After this call, status is false and result is "No such name"
local status, result = dns.query('www.google.abc')
-- After this call, status is true and result is the table {"72.14.204.103", "72.14.204.104", "72.14.204.147", "72.14.204.99"}
local status, result = dns.query('www.google.ca', {retAll=true})
-- After this call, status is true and result is the "2001:19f0:0:0:0:dead:beef:cafe"
local status, result = dns.query('irc.ipv6.efnet.org', {dtype='AAAA'})
</code>
Copyright© Same as Nmap--See http://nmap.org/book/man-legal.html
Source: http://nmap.org/svn/nselib/dns.lua
Functions
| addClientSubnet (pkt, Z, subnet, client_subnet) |
Adds an client-subnet paylod to the OPT packet implementing http://tools.ietf.org/html/draft-vandergaast-edns-client-subnet-00 |
| addNSID (pkt, Z) |
Adds an NSID paylod to the OPT packet |
| addOPT (pkt, Z, opt) |
Adds an OPT RR to a DNS packet's additional section. Only the table of Z flags is supported (i.e., not RDATA). See RFC 2671 section 4.3. |
| addQuestion (pkt, dname, dtype, class) |
Adds a question to a DNS packet table. |
| addUpdate (pkt, dname, dtype, ttl, data, class) |
Adds a update to a DNS packet table |
| addZone (pkt, dname) |
Adds a zone to a DNS packet table |
| decode (data) |
Decodes a DNS packet. |
| decStr (data, pos) |
Decodes a domain in a DNS packet. Handles "compressed" data too. |
| encode (pkt) |
Encode a DNS packet. |
| findNiceAdditional (dtype, dec, retAll) |
Calls the answer fetcher for |
| findNiceAnswer (dtype, dec, retAll) |
Calls the answer fetcher for |
| newPacket () |
Creates a new table representing a DNS packet. |
| query (dname, options) |
Query DNS servers for a DNS record. |
| reverse (ip) |
Formats an IP address for reverse lookup. |
| update (dname, options) |
Adds a record to the Zone |
Tables
| types |
Table of DNS resource types. |
Functions
- addClientSubnet (pkt, Z, subnet, client_subnet)
-
Adds an client-subnet paylod to the OPT packet implementing http://tools.ietf.org/html/draft-vandergaast-edns-client-subnet-00
Parameters
- pkt: Table representing DNS packet.
- Z: Table of Z flags. Only DO is supported.
- subnet:
-
client_subnet:
table containing the following fields
family- 1 IPv4, 2 - IPv6mask- byte containing the length of the subnet maskaddress- string containing the IP address
- addNSID (pkt, Z)
-
Adds an NSID paylod to the OPT packet
Parameters
- pkt: Table representing DNS packet.
- Z: Table of Z flags. Only DO is supported.
- addOPT (pkt, Z, opt)
-
Adds an OPT RR to a DNS packet's additional section. Only the table of Z flags is supported (i.e., not RDATA). See RFC 2671 section 4.3.
Parameters
- pkt: Table representing DNS packet.
- Z: Table of Z flags. Only DO is supported.
- opt:
- addQuestion (pkt, dname, dtype, class)
-
Adds a question to a DNS packet table.
Parameters
- pkt: Table representing DNS packet.
- dname: Domain name to be asked.
- dtype: RR to be asked.
- class:
- addUpdate (pkt, dname, dtype, ttl, data, class)
-
Adds a update to a DNS packet table
Parameters
- pkt: Table representing DNS packet.
- dname: Domain name to be asked.
- dtype: to be updated
- ttl: the time-to-live of the record
- data: type specific data
- class:
- addZone (pkt, dname)
-
Adds a zone to a DNS packet table
Parameters
- pkt: Table representing DNS packet.
- dname: Domain name to be asked.
- decode (data)
-
Decodes a DNS packet.
Parameters
- data: Encoded DNS packet.
Return value:
Table representing DNS packet. - decStr (data, pos)
-
Decodes a domain in a DNS packet. Handles "compressed" data too.
Parameters
- data: Complete DNS packet.
- pos: Starting position in packet.
Return values:
- Position after decoding.
- Decoded domain, or
nilon error.
- encode (pkt)
-
Encode a DNS packet.
Caution: doesn't encode answer and authority part.
Parameters
-
pkt:
Table representing DNS packet, initialized by
newPacket.
Return value:
Encoded DNS packet. -
pkt:
Table representing DNS packet, initialized by
- findNiceAdditional (dtype, dec, retAll)
-
Calls the answer fetcher for
dtypeor returns an error code in case of a "no such name" error.Parameters
- dtype: DNS resource record type.
- dec: Decoded DNS response.
- retAll: If true, return all entries, not just the first.
Return values:
- True if one or more answers of the required type were found - otherwise false.
- Answer according to the answer fetcher for
dtypeor an Error message.
- findNiceAnswer (dtype, dec, retAll)
-
Calls the answer fetcher for
dtypeor returns an error code in case of a "no such name" error.Parameters
- dtype: DNS resource record type.
- dec: Decoded DNS response.
- retAll: If true, return all entries, not just the first.
Return values:
- True if one or more answers of the required type were found - otherwise false.
- Answer according to the answer fetcher for
dtypeor an Error message.
- newPacket ()
-
Creates a new table representing a DNS packet.
Return value:
Table representing a DNS packet. - query (dname, options)
-
Query DNS servers for a DNS record.
Parameters
- dname: Desired domain name entry.
-
options:
A table containing any of the following fields:
dtype: Desired DNS record type (default:"A").host: DNS server to be queried (default: DNS servers known to Nmap).port: Port of DNS server to connect to (default:53).tries: How often shouldquerytry to contact another server (for non-recursive queries).retAll: Return all answers, not just the first.retPkt: Return the packet instead of using the answer-fetching mechanism.norecurse: If true, do not set the recursion (RD) flag.noauth: If true, do not try to find authoritative servermultiple: If true, expects multiple hosts to respond to multicast requestflags: numeric value to set flags in the DNS query to a specific valueid: numeric value to use for the DNS transaction idnsid: If true, queries the server for the nameserver identifier (RFC 5001)subnet: table, if set perform a edns-client-subnet lookup. The table should contain the fields:
family- string can be either inet or inet6address- string containing the originating subnet IP addressmask- number containing the number of subnet bits
Return values:
trueif a dns response was received and contained an answer of the requested type, or the decoded dns response was requested (retPkt) and is being returned - orfalseotherwise.- String answer of the requested type, table of answers or a String error message of one of the following: "No Such Name", "No Servers", "No Answers", "Unable to handle response"
- reverse (ip)
-
Formats an IP address for reverse lookup.
Parameters
- ip: IP address string.
Return value:
"Domain"-style representation of IP as subdomain of in-addr.arpa or ip6.arpa. - update (dname, options)
-
Adds a record to the Zone
Parameters
- dname: containing the hostname to add
-
options:
A table containing any of the following fields:
dtype: Desired DNS record type (default:"A").host: DNS server to be queried (default: DNS servers known to Nmap).timeout: The time to wait for a responsesendCount: The number of send attempts to performzone: If not supplied deduced from hostnamedata: Table or string containing update data (depending on record type):
pref,mxSRV - Table containingprio,weight,port,target
Return values:
- status true on success false on failure
- msg containing the error message Examples Adding different types of records to a server * update( "www.cqure.net", { host=host, port=port, dtype="A", data="10.10.10.10" } ) * update( "alias.cqure.net", { host=host, port=port, dtype="CNAME", data="www.cqure.net" } ) * update( "cqure.net", { host=host, port=port, dtype="MX", data={ pref=10, mx="mail.cqure.net"} }) * update( "_ldap._tcp.cqure.net", { host=host, port=port, dtype="SRV", data={ prio=0, weight=100, port=389, target="ldap.cqure.net" } } ) Removing the above records by setting an empty data and a ttl of zero * update( "www.cqure.net", { host=host, port=port, dtype="A", data="", ttl=0 } ) * update( "alias.cqure.net", { host=host, port=port, dtype="CNAME", data="", ttl=0 } ) * update( "cqure.net", { host=host, port=port, dtype="MX", data="", ttl=0 } ) * update( "_ldap._tcp.cqure.net", { host=host, port=port, dtype="SRV", data="", ttl=0 } )