ANN: dnslib-0.9.0 - DNS library for Python (with Py2/3 support)
Hello, I have just uploaded a new version of 'dnslib' to PyPi: https://pypi.python.org/pypi/dnslib/0.9.0 'dnslib' is a simple but very flexible library for encoding & decoding DNS data and creating custom DNS resolvers for Python 2/3. This is the first version that supports Python 3.2+ (and 2.7) and also includes a large number of fixes and additional functionality. (README included below). This is a major release - please submit any issues to the BitBucket issue tracker (https://bitbucket.org/paulc/dnslib). Thanks, PaulC dnslib ------ A library to encode/decode DNS wire-format packets supporting both Python 2.7 and Python 3.2+. The library provides: * Support for encoding/decoding DNS packets between wire format, python objects, and Zone/DiG textual representation (dnslib.dns) * A server framework allowing the simple creation of custom DNS resolvers (dnslib.server) and a number of example servers created using this frameowork * A number of utilities for testing (dnslib.client, dnslib.proxy, dnslib.intercept) Python 3 support was added in Version 0.9.0 which represented a fairly major update to the library - the key changes include: * Python 2.7/3.2+ support (the last version supporting Python 2.6 or earlier was version 0.8.3) * Support for encoding/decoding resource records in 'Zone' (BIND) file format * Support for encoding/decoding backets in 'DiG' format * Server framework allowing (in most cases) custom resolvers to be created by just subclassing the DNSResolver class and overringing the 'resolve' method * A lot of fixes to error detection/handling which should make the library much more robust to invalid/unsupported data. The library should now either return a valid DNSRecord instance or raise DNSError (tested via fuzzing) * Improved utilities (dnslib.client, dnslib.proxy, dnslib.intercept) * Improvements to encoding/decoding tests including the ability to generate test data automatically in test_decode.py (comparing outputs against DiG) * Ability to compare and diff DNSRecords This is a large release and despite the testing there therefore are likely to be some bugs. Once the 0.9 release is sufficiently stable I would expect to release as 1.0.0 (and stabilise th api) The key DNS packet handling classes are in dnslib.dns and map to the standard DNS packet sections: * DNSRecord - container for DNS packet. Contains: - DNSHeader - Question section containing zero or more DNSQuestion objects - Answer section containing zero or more RR objects - Authority section containing zero or more RR objects - Additional section containing zero or more RR objects * DNS RRs (resource records) contain an RR header and an RD object) * Specific RD types are implemented as subclasses of RD * DNS labels are represented by a DNSLabel class - in most cases this handles conversion to/from textual representation however does support arbitatry labels via a tuple of bytes objects) Version 0.9 of the library was a major rewrite to support Python 3.2+ (retaining support for Python 2.7+). As part of the Py3 changes a number of other significant changes were intrtoduced: - Much better error handling (packet decoding errors should be caught and DNSError raised) Usage: ------ To decode a DNS packet:
packet = binascii.unhexlify(b'd5ad818000010005000000000377777706676f6f676c6503636f6d0000010001c00c0005000100000005000803777777016cc010c02c0001000100000005000442f95b68c02c0001000100000005000442f95b63c02c0001000100000005000442f95b67c02c0001000100000005000442f95b93') d = DNSRecord.parse(packet) d <DNS Header: id=0xd5ad type=RESPONSE opcode=QUERY flags=RD,RA rcode='NOERROR' q=1 a=5 ns=0 ar=0> <DNS Question: 'www.google.com.' qtype=A qclass=IN> <DNS RR: 'www.google.com.' rtype=CNAME rclass=IN ttl=5 rdata='www.l.google.com.'> <DNS RR: 'www.l.google.com.' rtype=A rclass=IN ttl=5 rdata='66.249.91.104'> <DNS RR: 'www.l.google.com.' rtype=A rclass=IN ttl=5 rdata='66.249.91.99'> <DNS RR: 'www.l.google.com.' rtype=A rclass=IN ttl=5 rdata='66.249.91.103'> <DNS RR: 'www.l.google.com.' rtype=A rclass=IN ttl=5 rdata='66.249.91.147'>
The default text representation of the DNSRecord is in zone file format:
print(d) ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 54701 ;; flags: qr rd ra; QUERY: 1, ANSWER: 5, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;www.google.com. IN A ;; ANSWER SECTION: www.google.com. 5 IN CNAME www.l.google.com. www.l.google.com. 5 IN A 66.249.91.104 www.l.google.com. 5 IN A 66.249.91.99 www.l.google.com. 5 IN A 66.249.91.103 www.l.google.com. 5 IN A 66.249.91.147
To create a DNS Request Packet:
d = DNSRecord.question("google.com")
(This is equivalent to: d = DNSRecord(q=DNSQuestion("google.com") )
d <DNS Header: id=... type=QUERY opcode=QUERY flags=RD rcode='NOERROR' q=1 a=0 ns=0 ar=0> <DNS Question: 'google.com.' qtype=A qclass=IN>
str(DNSRecord.parse(d.pack())) == str(d) True
print(d) ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: ... ;; flags: rd; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;google.com. IN A
d = DNSRecord.question("google.com","MX")
(This is equivalent to: d = DNSRecord(q=DNSQuestion("google.com",QTYPE.MX) )
str(DNSRecord.parse(d.pack())) == str(d) True
print(d) ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: ... ;; flags: rd; QUERY: 1, ANSWER: 0, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;google.com. IN MX
To create a DNS Response Packet:
d = DNSRecord(DNSHeader(qr=1,aa=1,ra=1), ... q=DNSQuestion("abc.com"), ... a=RR("abc.com",rdata=A("1.2.3.4"))) d <DNS Header: id=... type=RESPONSE opcode=QUERY flags=AA,RD,RA rcode='NOERROR' q=1 a=1 ns=0 ar=0> <DNS Question: 'abc.com.' qtype=A qclass=IN> <DNS RR: 'abc.com.' rtype=A rclass=IN ttl=0 rdata='1.2.3.4'> str(DNSRecord.parse(d.pack())) == str(d) True
print(d) ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: ... ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;abc.com. IN A ;; ANSWER SECTION: abc.com. 0 IN A 1.2.3.4
It is also possible to create RRs from a string in zone file format
RR.fromZone("abc.com IN A 1.2.3.4") [<DNS RR: 'abc.com.' rtype=A rclass=IN ttl=0 rdata='1.2.3.4'>]
(Note: this produces a list of RRs which should be unpacked if being passed to add_answer/add_auth/add_ar etc)
q = DNSRecord.question("abc.com") a = q.reply() a.add_answer(*RR.fromZone("abc.com 60 A 1.2.3.4")) print(a) ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: ... ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;abc.com. IN A ;; ANSWER SECTION: abc.com. 60 IN A 1.2.3.4
The zone file can contain multiple entries and supports most of the normal format defined in RFC1035 (specifically not $INCLUDE)
z = ''' ... $TTL 300 ... $ORIGIN abc.com ... ... @ IN MX 10 mail.abc.com. ... www IN A 1.2.3.4 ... IN TXT "Some Text" ... mail IN CNAME www.abc.com. ... ''' for rr in RR.fromZone(textwrap.dedent(z)): ... print(rr) abc.com. 300 IN MX 10 mail.abc.com. www.abc.com. 300 IN A 1.2.3.4 www.abc.com. 300 IN TXT "Some Text" mail.abc.com. 300 IN CNAME www.abc.com.
To create a skeleton reply to a DNS query:
q = DNSRecord(q=DNSQuestion("abc.com",QTYPE.ANY)) a = q.reply() a.add_answer(RR("abc.com",QTYPE.A,rdata=A("1.2.3.4"),ttl=60)) str(DNSRecord.parse(a.pack())) == str(a) True print(a) ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: ... ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;abc.com. IN ANY ;; ANSWER SECTION: abc.com. 60 IN A 1.2.3.4
Add additional RRs:
a.add_answer(RR("xxx.abc.com",QTYPE.A,rdata=A("1.2.3.4"))) a.add_answer(RR("xxx.abc.com",QTYPE.AAAA,rdata=AAAA("1234:5678::1"))) str(DNSRecord.parse(a.pack())) == str(a) True print(a) ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: ... ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 3, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;abc.com. IN ANY ;; ANSWER SECTION: abc.com. 60 IN A 1.2.3.4 xxx.abc.com. 0 IN A 1.2.3.4 xxx.abc.com. 0 IN AAAA 1234:5678::1
It is also possible to create a reply from a string in zone file format:
q = DNSRecord(q=DNSQuestion("abc.com",QTYPE.ANY)) a = q.replyZone("abc.com 60 IN CNAME xxx.abc.com") print(a) ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: ... ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;abc.com. IN ANY ;; ANSWER SECTION: abc.com. 60 IN CNAME xxx.abc.com.
str(DNSRecord.parse(a.pack())) == str(a) True
q = DNSRecord(q=DNSQuestion("abc.com",QTYPE.ANY)) a = q.replyZone(textwrap.dedent(z)) print(a) ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: ... ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 4, AUTHORITY: 0, ADDITIONAL: 0 ;; QUESTION SECTION: ;abc.com. IN ANY ;; ANSWER SECTION: abc.com. 300 IN MX 10 mail.abc.com. www.abc.com. 300 IN A 1.2.3.4 www.abc.com. 300 IN TXT "Some Text" mail.abc.com. 300 IN CNAME www.abc.com.
The library also includes a simple framework for generating custom DNS resolvers in dnslib.server (see module docs). In post cases this just requires implementing a custom 'resolve' method which receives a question object and returns a response. A number of sample resolvers are provided as examples (see CLI --help): dnslib.fixedresolver - Respond to all requests with fixed response dnslib.zoneresolver - Respond from Zone file dnslib.shellresolver - Call shell script to generate response The library includes a number of client utilities which can be run using: DiG like client library # python -m dnslib.client --help DNS Proxy Server # python -m dnslib.proxy --help Intercepting DNS Proxy Server (replace proxy responses for specified domains) # python -m dnslib.intercept --help Changelog: ---------- * 0.1 2010-09-19 Initial Release * 0.2 2010-09-22 Minor fixes * 0.3 2010-10-02 Add DNSLabel class to support arbitrary labels (embedded '.') * 0.4 2012-02-26 Merge with dbslib-circuits * 0.5 2012-09-13 Add support for RFC2136 DDNS updates Patch provided by Wesley Shields <wxs@FreeBSD.org> - thanks * 0.6 2012-10-20 Basic AAAA support * 0.7 2012-10-20 Add initial EDNS0 support (untested) * 0.8 2012-11-04 Add support for NAPTR, Authority RR and additional RR Patch provided by Stefan Andersson (https://bitbucket.org/norox) - thanks * 0.8.1 2012-11-05 Added NAPTR test case and fixed logic error Patch provided by Stefan Andersson (https://bitbucket.org/norox) - thanks * 0.8.2 2012-11-11 Patch to fix IPv6 formatting Patch provided by Torbjörn Lönnemark (https://bitbucket.org/tobbezz) - thanks * 0.8.3 2013-04-27 Don't parse rdata if rdlength is 0 Patch provided by Wesley Shields <wxs@FreeBSD.org> - thanks * 0.9.0 2014-05-05 Major update including Py3 support (see docs) License: -------- * BSD Author: ------- * Paul Chakravarti (paul.chakravarti@gmail.com) Master Repository/Issues: ------------------------- * https://bitbucket.org/paulc/dnslib (Cloned on GitHub: https://github.com/paulchakravarti/dnslib)
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Paul Chakravarti