Macem-macem aspek operasi DNS wis bola-bali disentuh dening penulis ing sawetara diterbitake minangka bagéan saka blog. Ing wektu sing padha, penekanan utama yaiku ningkatake keamanan layanan Internet utama iki.
Nganti saiki, senadyan kerentanan lalu lintas DNS sing jelas, sing isih, umume, ditularake kanthi jelas, kanggo tumindak ala saka panyedhiya sing pengin nambah penghasilan kanthi nambahake pariwara ing konten, lembaga keamanan pemerintah lan censorship, uga mung kriminal, proses , sanajan ana macem-macem teknologi kayata DNSSEC / DANE, DNScrypt, DNS-over-TLS lan DNS-over-HTTPS, macet. Lan yen solusi server, lan sawetara sing wis ana kanggo dangu, dikenal lan kasedhiya, dhukungan saka piranti lunak klien ninggalake akeh sing dikarepake.
Untunge, kahanan saya ganti. Utamane, pangembang browser Firefox sing populer babagan rencana ngaktifake mode dhukungan kanthi standar (DoH) enggal. Iki kudu mbantu nglindhungi lalu lintas DNS pangguna WWW saka ancaman ing ndhuwur, nanging bisa uga ngenalake sing anyar.
1. Masalah DNS-over-HTTPS
Sepisanan, introduksi massal DNS-over-HTTPS menyang piranti lunak Internet mung nyebabake reaksi positif. Nanging, setan, kaya sing dikandhakake, ana ing rincian.
Masalah pisanan sing mbatesi ruang lingkup panggunaan nyebar DoH yaiku fokus mung ing lalu lintas web. Pancen, protokol HTTP lan HTTP/2 versi saiki, sing didhasarake DoH, minangka basis saka WWW. Nanging Internet ora mung web. Ana akeh layanan populer, kayata email, macem-macem instant messenger, sistem transfer file, streaming multimedia, lan liya-liyane, sing ora nggunakake HTTP. Mangkono, sanajan persepsi dening akeh DoH minangka panacea, ternyata ora bisa ditrapake tanpa gaweyan tambahan (lan ora perlu) kanggo apa wae kajaba teknologi browser. Miturut cara, DNS-over-TLS katon kaya calon sing luwih pantes kanggo peran iki, sing ngetrapake enkapsulasi lalu lintas DNS standar ing protokol TLS standar sing aman.
Masalah kaloro, sing duweni potensi luwih penting tinimbang sing sepisanan, yaiku nglirwakake desentralisasi DNS kanthi desain kanggo nggunakake server DoH siji sing ditemtokake ing setelan browser. Utamane, Mozilla nyaranake nggunakake layanan saka Cloudflare. Layanan sing padha uga diluncurake dening tokoh Internet liyane, utamane Google. Pranyata yen implementasi DNS-over-HTTPS ing wangun sing saiki diusulake mung nambah katergantungan pangguna pungkasan ing layanan paling gedhe. Ora ana rahasia manawa informasi sing bisa diwenehake analisis pitakon DNS bisa ngumpulake data sing luwih akeh babagan, uga nambah akurasi lan relevansi.
Ing babagan iki, penulis lan tetep dadi panyengkuyung implementasi massal dudu DNS-over-HTTPS, nanging DNS-over-TLS bebarengan karo DNSSEC/DANE minangka universal, aman lan ora kondusif kanggo sentralisasi sarana Internet. kanggo njamin keamanan lalu lintas DNS. Sayange, amarga alasan sing jelas, siji ora bisa nyana introduksi kanthi cepet saka dhukungan massa kanggo alternatif DoH menyang piranti lunak klien, lan isih dadi domain para penggemar teknologi keamanan.
Nanging amarga kita saiki duwe DoH, kenapa ora nggunakake sawise uwal saka pengawasan potensial dening perusahaan liwat server menyang server DNS-over-HTTPS kita dhewe?
2. protokol DNS-over-HTTPS
Yen katon ing standar njlèntrèhaké protokol DNS-over-HTTPS, sampeyan bisa ndeleng manawa iku, nyatane, API web sing ngijini sampeyan kanggo encapsulate paket DNS standar ing protokol HTTP / 2. Iki ditindakake liwat header HTTP khusus, uga konversi format binar data DNS sing dikirim (pirsani. lan dokumen sakteruse) menyang formulir sing ngidini sampeyan ngirim lan nampa, uga nggarap metadata sing dibutuhake.
Miturut standar, mung HTTP/2 lan sambungan TLS aman sing didhukung.
Ngirim panjalukan DNS bisa ditindakake kanthi nggunakake metode GET lan POST standar. Ing kasus sing sepisanan, panyuwunan kasebut diowahi dadi string sing dienkode base64URL, lan sing kapindho, liwat awak panyuwunan POST ing wangun binar. Ing kasus iki, jinis data MIME khusus digunakake sajrone panjalukan lan respon DNS aplikasi/dns-pesen.
root@eprove:~ # curl -H 'accept: application/dns-message' 'https://my.domaint/dns-query?dns=q80BAAABAAAAAAAAB2V4YW1wbGUDY29tAAABAAE' -v
* Trying 2001:100:200:300::400:443...
* TCP_NODELAY set
* Connected to eprove.net (2001:100:200:300::400) port 443 (#0)
* ALPN, offering h2
* ALPN, offering http/1.1
* successfully set certificate verify locations:
* CAfile: /usr/local/share/certs/ca-root-nss.crt
CApath: none
* TLSv1.3 (OUT), TLS handshake, Client hello (1):
* TLSv1.3 (IN), TLS handshake, Server hello (2):
* TLSv1.3 (IN), TLS handshake, Encrypted Extensions (8):
* TLSv1.3 (IN), TLS handshake, Certificate (11):
* TLSv1.3 (IN), TLS handshake, CERT verify (15):
* TLSv1.3 (IN), TLS handshake, Finished (20):
* TLSv1.3 (OUT), TLS change cipher, Change cipher spec (1):
* TLSv1.3 (OUT), TLS handshake, Finished (20):
* SSL connection using TLSv1.3 / TLS_AES_256_GCM_SHA384
* ALPN, server accepted to use h2
* Server certificate:
* subject: CN=my.domain
* start date: Jul 22 00:07:13 2019 GMT
* expire date: Oct 20 00:07:13 2019 GMT
* subjectAltName: host "my.domain" matched cert's "my.domain"
* issuer: C=US; O=Let's Encrypt; CN=Let's Encrypt Authority X3
* SSL certificate verify ok.
* Using HTTP2, server supports multi-use
* Connection state changed (HTTP/2 confirmed)
* Copying HTTP/2 data in stream buffer to connection buffer after upgrade: len=0
* Using Stream ID: 1 (easy handle 0x801441000)
> GET /dns-query?dns=q80BAAABAAAAAAAAB2V4YW1wbGUDY29tAAABAAE HTTP/2
> Host: eprove.net
> User-Agent: curl/7.65.3
> accept: application/dns-message
>
* TLSv1.3 (IN), TLS handshake, Newsession Ticket (4):
* Connection state changed (MAX_CONCURRENT_STREAMS == 100)!
< HTTP/2 200
< server: h2o/2.3.0-beta2
< content-type: application/dns-message
< cache-control: max-age=86274
< date: Thu, 12 Sep 2019 13:07:25 GMT
< strict-transport-security: max-age=15768000; includeSubDomains; preload
< content-length: 45
<
Warning: Binary output can mess up your terminal. Use "--output -" to tell
Warning: curl to output it to your terminal anyway, or consider "--output
Warning: <FILE>" to save to a file.
* Failed writing body (0 != 45)
* stopped the pause stream!
* Connection #0 to host eprove.net left intactUga mbayar manungsa waé kanggo judhul kontrol cache: ing respon saka server web. Ing parameter maks-umur ngemot nilai TTL kanggo cathetan DNS sing bakal dibalekake (utawa nilai minimal yen sakumpulan kasebut dibalekake).
Adhedhasar ing ndhuwur, fungsi server DoH dumadi saka sawetara tahapan.
- Nampa panjalukan HTTP. Yen iki GET banjur decode paket saka base64URL encoding.
- Kirim paket iki menyang server DNS.
- Njaluk respon saka server DNS
- Temokake nilai TTL minimal ing cathetan sing ditampa.
- Mbalikake respon menyang klien liwat HTTP.
3. Server DNS-over-HTTPS sampeyan dhewe
Cara paling gampang, paling cepet lan paling efektif kanggo mbukak server DNS-over-HTTPS dhewe yaiku nggunakake server web HTTP/2. , sing wis ditulis dening penulis kanthi ringkes (pirsani "").
Pilihan iki didhukung dening kasunyatan manawa kabeh kode server DoH sampeyan bisa dileksanakake kanthi nggunakake interpreter sing terintegrasi menyang H2O dhewe. . Saliyane perpustakaan standar, kanggo ngganti data karo server DNS, sampeyan butuh perpustakaan Soket (mrbgem), sing, untunge, wis kalebu ing versi pangembangan saiki H2O 2.3.0-beta2. ing port FreeBSD. Nanging, ora angel ditambahake menyang versi sadurunge kanthi kloning repositori menyang katalog /deps sadurunge kompilasi.
root@beta:~ # uname -v
FreeBSD 12.0-RELEASE-p10 GENERIC
root@beta:~ # cd /usr/ports/www/h2o
root@beta:/usr/ports/www/h2o # make extract
===> License MIT BSD2CLAUSE accepted by the user
===> h2o-2.2.6 depends on file: /usr/local/sbin/pkg - found
===> Fetching all distfiles required by h2o-2.2.6 for building
===> Extracting for h2o-2.2.6.
=> SHA256 Checksum OK for h2o-h2o-v2.2.6_GH0.tar.gz.
===> h2o-2.2.6 depends on file: /usr/local/bin/ruby26 - found
root@beta:/usr/ports/www/h2o # cd work/h2o-2.2.6/deps/
root@beta:/usr/ports/www/h2o/work/h2o-2.2.6/deps # git clone https://github.com/iij/mruby-socket.git
Клонирование в «mruby-socket»…
remote: Enumerating objects: 385, done.
remote: Total 385 (delta 0), reused 0 (delta 0), pack-reused 385
Получение объектов: 100% (385/385), 98.02 KiB | 647.00 KiB/s, готово.
Определение изменений: 100% (208/208), готово.
root@beta:/usr/ports/www/h2o/work/h2o-2.2.6/deps # ll
total 181
drwxr-xr-x 9 root wheel 18 12 авг. 16:09 brotli/
drwxr-xr-x 2 root wheel 4 12 авг. 16:09 cloexec/
drwxr-xr-x 2 root wheel 5 12 авг. 16:09 golombset/
drwxr-xr-x 4 root wheel 35 12 авг. 16:09 klib/
drwxr-xr-x 2 root wheel 5 12 авг. 16:09 libgkc/
drwxr-xr-x 4 root wheel 26 12 авг. 16:09 libyrmcds/
drwxr-xr-x 13 root wheel 32 12 авг. 16:09 mruby/
drwxr-xr-x 5 root wheel 11 12 авг. 16:09 mruby-digest/
drwxr-xr-x 5 root wheel 10 12 авг. 16:09 mruby-dir/
drwxr-xr-x 5 root wheel 10 12 авг. 16:09 mruby-env/
drwxr-xr-x 4 root wheel 9 12 авг. 16:09 mruby-errno/
drwxr-xr-x 5 root wheel 14 12 авг. 16:09 mruby-file-stat/
drwxr-xr-x 5 root wheel 10 12 авг. 16:09 mruby-iijson/
drwxr-xr-x 5 root wheel 11 12 авг. 16:09 mruby-input-stream/
drwxr-xr-x 6 root wheel 11 12 авг. 16:09 mruby-io/
drwxr-xr-x 5 root wheel 10 12 авг. 16:09 mruby-onig-regexp/
drwxr-xr-x 4 root wheel 10 12 авг. 16:09 mruby-pack/
drwxr-xr-x 5 root wheel 10 12 авг. 16:09 mruby-require/
drwxr-xr-x 6 root wheel 10 12 сент. 16:10 mruby-socket/
drwxr-xr-x 2 root wheel 9 12 авг. 16:09 neverbleed/
drwxr-xr-x 2 root wheel 13 12 авг. 16:09 picohttpparser/
drwxr-xr-x 2 root wheel 4 12 авг. 16:09 picotest/
drwxr-xr-x 9 root wheel 16 12 авг. 16:09 picotls/
drwxr-xr-x 4 root wheel 8 12 авг. 16:09 ssl-conservatory/
drwxr-xr-x 8 root wheel 18 12 авг. 16:09 yaml/
drwxr-xr-x 2 root wheel 8 12 авг. 16:09 yoml/
root@beta:/usr/ports/www/h2o/work/h2o-2.2.6/deps # cd ../../..
root@beta:/usr/ports/www/h2o # make install clean
...Konfigurasi server web umume standar.
root@beta:/usr/ports/www/h2o # cd /usr/local/etc/h2o/
root@beta:/usr/local/etc/h2o # cat h2o.conf
# this sample config gives you a feel for how h2o can be used
# and a high-security configuration for TLS and HTTP headers
# see https://h2o.examp1e.net/ for detailed documentation
# and h2o --help for command-line options and settings
# v.20180207 (c)2018 by Max Kostikov http://kostikov.co e-mail: [email protected]
user: www
pid-file: /var/run/h2o.pid
access-log:
path: /var/log/h2o/h2o-access.log
format: "%h %v %l %u %t "%r" %s %b "%{Referer}i" "%{User-agent}i""
error-log: /var/log/h2o/h2o-error.log
expires: off
compress: on
file.dirlisting: off
file.send-compressed: on
file.index: [ 'index.html', 'index.php' ]
listen:
port: 80
listen:
port: 443
ssl:
cipher-suite: ECDHE-ECDSA-CHACHA20-POLY1305:ECDHE-RSA-CHACHA20-POLY1305:ECDHE-ECDSA-AES128-GCM-SHA256:ECDHE-RSA-AES128-GCM-SHA256:ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384:DHE-RSA-AES128-GCM-SHA256:DHE-RSA-AES256-GCM-SHA384:ECDHE-ECDSA-AES128-SHA256:ECDHE-RSA-AES128-SHA256:ECDHE-ECDSA-AES128-SHA:ECDHE-RSA-AES256-SHA384:ECDHE-RSA-AES128-SHA:ECDHE-ECDSA-AES256-SHA384:ECDHE-ECDSA-AES256-SHA:ECDHE-RSA-AES256-SHA:DHE-RSA-AES128-SHA256:DHE-RSA-AES128-SHA:DHE-RSA-AES256-SHA256:DHE-RSA-AES256-SHA:ECDHE-ECDSA-DES-CBC3-SHA:ECDHE-RSA-DES-CBC3-SHA:EDH-RSA-DES-CBC3-SHA:AES128-GCM-SHA256:AES256-GCM-SHA384:AES128-SHA256:AES256-SHA256:AES128-SHA:AES256-SHA:DES-CBC3-SHA:!DSS
cipher-preference: server
dh-file: /etc/ssl/dhparams.pem
certificate-file: /usr/local/etc/letsencrypt/live/eprove.net/fullchain.pem
key-file: /usr/local/etc/letsencrypt/live/my.domain/privkey.pem
hosts:
"*.my.domain":
paths: &go_tls
"/":
redirect:
status: 301
url: https://my.domain/
"my.domain:80":
paths: *go_tls
"my.domain:443":
header.add: "Strict-Transport-Security: max-age=15768000; includeSubDomains; preload"
paths:
"/dns-query":
mruby.handler-file: /usr/local/etc/h2o/h2odoh.rbPangecualian mung panangan URL /dns-query sing server DNS-over-HTTPS kita, ditulis ing mruby lan disebut liwat pilihan handler, bener tanggung jawab mruby.handler-file.
root@beta:/usr/local/etc/h2o # cat h2odoh.rb
# H2O HTTP/2 web server as DNS-over-HTTP service
# v.20190908 (c)2018-2019 Max Kostikov https://kostikov.co e-mail: [email protected]
proc {|env|
if env['HTTP_ACCEPT'] == "application/dns-message"
case env['REQUEST_METHOD']
when "GET"
req = env['QUERY_STRING'].gsub(/^dns=/,'')
# base64URL decode
req = req.tr("-_", "+/")
if !req.end_with?("=") && req.length % 4 != 0
req = req.ljust((req.length + 3) & ~3, "=")
end
req = req.unpack1("m")
when "POST"
req = env['rack.input'].read
else
req = ""
end
if req.empty?
[400, { 'content-type' => 'text/plain' }, [ "Bad Request" ]]
else
# --- ask DNS server
sock = UDPSocket.new
sock.connect("localhost", 53)
sock.send(req, 0)
str = sock.recv(4096)
sock.close
# --- find lowest TTL in response
nans = str[6, 2].unpack1('n') # number of answers
if nans > 0 # no DNS failure
shift = 12
ttl = 0
while nans > 0
# process domain name compression
if str[shift].unpack1("C") < 192
shift = str.index("x00", shift) + 5
if ttl == 0 # skip question section
next
end
end
shift += 6
curttl = str[shift, 4].unpack1('N')
shift += str[shift + 4, 2].unpack1('n') + 6 # responce data size
if ttl == 0 or ttl > curttl
ttl = curttl
end
nans -= 1
end
cc = 'max-age=' + ttl.to_s
else
cc = 'no-cache'
end
[200, { 'content-type' => 'application/dns-message', 'content-length' => str.size, 'cache-control' => cc }, [ str ] ]
end
else
[415, { 'content-type' => 'text/plain' }, [ "Unsupported Media Type" ]]
end
}Elinga yen server caching lokal tanggung jawab kanggo ngolah paket DNS, ing kasus iki saka distribusi FreeBSD standar. Saka sudut pandang keamanan, iki minangka solusi sing paling optimal. Nanging, ora ana sing ngalangi sampeyan ngganti localhost menyang alamat DNS liyane sing arep digunakake.
root@beta:/usr/local/etc/h2o # local-unbound verison
usage: local-unbound [options]
start unbound daemon DNS resolver.
-h this help
-c file config file to read instead of /var/unbound/unbound.conf
file format is described in unbound.conf(5).
-d do not fork into the background.
-p do not create a pidfile.
-v verbose (more times to increase verbosity)
Version 1.8.1
linked libs: mini-event internal (it uses select), OpenSSL 1.1.1a-freebsd 20 Nov 2018
linked modules: dns64 respip validator iterator
BSD licensed, see LICENSE in source package for details.
Report bugs to [email protected]
root@eprove:/usr/local/etc/h2o # sockstat -46 | grep unbound
unbound local-unbo 69749 3 udp6 ::1:53 *:*
unbound local-unbo 69749 4 tcp6 ::1:53 *:*
unbound local-unbo 69749 5 udp4 127.0.0.1:53 *:*
unbound local-unbo 69749 6 tcp4 127.0.0.1:53 *:*Kabeh sing isih ana yaiku miwiti maneh H2O lan ndeleng apa sing kedadeyan.
root@beta:/usr/local/etc/h2o # service h2o restart
Stopping h2o.
Waiting for PIDS: 69871.
Starting h2o.
start_server (pid:70532) starting now...4. Testing
Dadi, ayo mriksa asil kanthi ngirim panjaluk tes maneh lan ndeleng lalu lintas jaringan nggunakake sarana kasebut tcpdump.
root@beta/usr/local/etc/h2o # curl -H 'accept: application/dns-message' 'https://my.domain/dns-query?dns=q80BAAABAAAAAAAAB2V4YW1wbGUDY29tAAABAAE'
Warning: Binary output can mess up your terminal. Use "--output -" to tell
Warning: curl to output it to your terminal anyway, or consider "--output
Warning: <FILE>" to save to a file.
...
root@beta:~ # tcpdump -n -i lo0 udp port 53 -xx -XX -vv
tcpdump: listening on lo0, link-type NULL (BSD loopback), capture size 262144 bytes
16:32:40.420831 IP (tos 0x0, ttl 64, id 37575, offset 0, flags [none], proto UDP (17), length 57, bad cksum 0 (->e9ea)!)
127.0.0.1.21070 > 127.0.0.1.53: [bad udp cksum 0xfe38 -> 0x33e3!] 43981+ A? example.com. (29)
0x0000: 0200 0000 4500 0039 92c7 0000 4011 0000 ....E..9....@...
0x0010: 7f00 0001 7f00 0001 524e 0035 0025 fe38 ........RN.5.%.8
0x0020: abcd 0100 0001 0000 0000 0000 0765 7861 .............exa
0x0030: 6d70 6c65 0363 6f6d 0000 0100 01 mple.com.....
16:32:40.796507 IP (tos 0x0, ttl 64, id 37590, offset 0, flags [none], proto UDP (17), length 73, bad cksum 0 (->e9cb)!)
127.0.0.1.53 > 127.0.0.1.21070: [bad udp cksum 0xfe48 -> 0x43fa!] 43981 q: A? example.com. 1/0/0 example.com. A 93.184.216.34 (45)
0x0000: 0200 0000 4500 0049 92d6 0000 4011 0000 ....E..I....@...
0x0010: 7f00 0001 7f00 0001 0035 524e 0035 fe48 .........5RN.5.H
0x0020: abcd 8180 0001 0001 0000 0000 0765 7861 .............exa
0x0030: 6d70 6c65 0363 6f6d 0000 0100 01c0 0c00 mple.com........
0x0040: 0100 0100 0151 8000 045d b8d8 22 .....Q...].."
^C
2 packets captured
23 packets received by filter
0 packets dropped by kernelOutput nuduhake carane panjalukan kanggo mutusake masalah alamat example.com ditampa lan kasil diproses dening server DNS.
Saiki sing isih ana yaiku ngaktifake server kita ing browser Firefox. Kanggo nindakake iki, sampeyan kudu ngganti sawetara setelan ing kaca konfigurasi babagan: config.
Kaping pisanan, iki alamat API sing browser bakal njaluk informasi DNS jaringan.trr.uri. Sampeyan uga dianjurake kanggo nemtokake IP domain saka URL iki kanggo resolusi IP aman nggunakake browser dhewe tanpa ngakses DNS ing network.trr.bootstrapAddress. Lan pungkasanipun, parameter dhewe network.trr.mode kalebu nggunakake DoH. Nyetel nilai dadi "3" bakal meksa browser nggunakake DNS-over-HTTPS sacara eksklusif kanggo resolusi jeneng, dene "2" sing luwih dipercaya lan aman bakal menehi prioritas kanggo DoH, ninggalake pencarian DNS standar minangka pilihan mundur.
5. laba!
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Source: www.habr.com