Tor

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Tor は第2世代オニオンルーティングのオープンソース実装で、匿名プロクシネットワークへのアクセスを提供します。Tor の目標はトラフィック解析攻撃を防いでネットワークの匿名性を守ることです。

イントロダクション

Tor ネットワークのユーザーはマシン上でオニオンプロクシを実行します。このソフトウェアは Tor に接続し、定期的に Tor ネットワークの仮想回線を構築します。Tor は層状の (つまり 'タマネギ' のような) 暗号化をすることで、ルーター間の完全な匿名性を保証しています。同時に、オニオンプロクシソフトウェアにはクライアントのために SOCKS インターフェースがあります。つまり SOCKS を利用できるアプリケーションは Tor に接続可能で、多様な通信が Tor 仮想回線を利用することができます。

警告: あなたが匿名性を維持するのに必要なのは Tor だけではありません。注意するべき落とし穴がいくつか存在します (参照: Want Tor to really work?)。

Through this process the onion proxy manages networking traffic for end-user anonymity. It keeps a user anonymous by encrypting traffic, sending it through other nodes of the Tor network, and decrypting it at the last node to receive your traffic before forwarding it to the server you specified. One trade off that has to be made for the anonymity Tor provides is that it can be considerably slower than a regular direct connection, due to the large amount of traffic re-routing. Additionally, although Tor provides protection against traffic analysis it cannot prevent traffic confirmation at the boundaries of the Tor network (i.e. the traffic entering and exiting the network).

インストール

公式リポジトリにある tor をインストールしてください。

さらに、Tor の Qt フロントエンドである vidalia が利用できます。Tor プロセスの操作に加えて、Vidalia では Tor の状態の回覧・設定、利用帯域の監視、ログメッセージの回覧・フィルター・検索が可能です。

設定

Tor をより深く理解するために、設定ファイルの /etc/tor/torrc をよく見て下さい。設定オプションの説明は man tor や Tor website で見られます。ほとんどの場合はデフォルト設定で問題なく Tor は動作します。

TOR_MAX_FD 変数を使って /etc/conf.d/tor の Tor のファイル記述子の ulimits をカスタムすることができます。これは開くファイルの最大数の制限を設定します。

デフォルトでは Tor はログレベル "notice" で標準出力にログを出力します。システムログインが torrc 設定ファイルで有効になっている場合は、ログのデフォルトは /usr/local/var/log/tor/ にあります。

The "RunAsDaemon" setting conflicts with the default runtype of "simple" in the service file. You should not need to enable it. systemd handles the daemonization of tor. If you do enable it for whatever reason, you will need to override the service file to change the runtype to "Type=forking" so systemd allows tor to fork itself.

Tor を Chroot で実行する

セキュリティを高めるために、chroot で Tor を実行するのが望ましい場合があります。以下のスクリプトは /opt/torchroot に適切な chroot を作成します:

~/torchroot-setup.sh

#!/bin/bash
export TORCHROOT=/opt/torchroot

mkdir -p $TORCHROOT
mkdir -p $TORCHROOT/etc/tor
mkdir -p $TORCHROOT/dev
mkdir -p $TORCHROOT/usr/bin
mkdir -p $TORCHROOT/usr/lib
mkdir -p $TORCHROOT/var/lib

ln -s /usr/lib  $TORCHROOT/lib
cp /etc/hosts           $TORCHROOT/etc/
cp /etc/host.conf       $TORCHROOT/etc/
cp /etc/localtime       $TORCHROOT/etc/
cp /etc/nsswitch.conf   $TORCHROOT/etc/
cp /etc/resolv.conf     $TORCHROOT/etc/
cp /etc/tor/torrc       $TORCHROOT/etc/tor/

cp /usr/bin/tor         $TORCHROOT/usr/bin/
cp /lib/libnss* /lib/libnsl* /lib/ld-linux.so* /lib/libresolv* /lib/libgcc_s.so* $TORCHROOT/usr/lib/
cp $(ldd /usr/bin/tor | awk '{print $3}'|grep --color=never "^/") $TORCHROOT/usr/lib/
cp -r /var/lib/tor      $TORCHROOT/var/lib/
chown -R tor:tor $TORCHROOT/var/lib/tor

sh -c "grep --color=never ^tor /etc/passwd > $TORCHROOT/etc/passwd"
sh -c "grep --color=never ^tor /etc/group > $TORCHROOT/etc/group"

mknod -m 644 $TORCHROOT/dev/random c 1 8
mknod -m 644 $TORCHROOT/dev/urandom c 1 9
mknod -m 666 $TORCHROOT/dev/null c 1 3

if [[ "$(uname -m)" == "x86_64" ]]; then
  cp /usr/lib/ld-linux-x86-64.so* $TORCHROOT/usr/lib/.
  ln -s /usr/lib64 $TORCHROOT/lib64
  ln -s $TORCHROOT/usr/lib ${TORCHROOT}/usr/lib64
fi

このスクリプトを root で実行した後、次のコマンドで chroot に Tor を起動できます: # chroot --userspec=tor:tor /opt/torchroot /usr/bin/tor

使用方法

systemd を使って tor.service を起動・有効にしてください。

もしくは、vidalia インターフェースからも tor を起動出来ます。

プログラムに Tor を通すには、SOCKS5 プロクシーとして 127.0.0.1 か localhost をポート 9050 (tor の標準設定) 又は 9051 (vidalia の標準設定) で使うようにプログラムを設定してください。 Tor が正しく機能しているか確認するために Tor , Harvard , Xenobite.eu などのウェブサイトを開いてみましょう。

ウェブブラウズ

Tor プロジェクトは現在 tor を使ったウェブブラウズは Tor Browser Bundle だけサポートしています。このブラウザは AUR からダウンロード可能です (tor-browser-en^AUR)。Firefox にパッチをあてたバージョンにサポートを拡張して作られています。普通の Firefox や Chromium など他のブラウザで Tor を使うこともできますが、Tor プロジェクトからは推奨されていません。

ヒント: For makepkg to verify the signature on the AUR source tarball download for TBB, signing keys from the Tor Project (currently 0x63FEE659) must be downloaded from the keyservers and added to the user gpg keyring with:

$ gpg --recv-keys 0x63FEE659

Firefox

設定 > 詳細 > ネットワークタブ > 接続設定 から SOCKS の localhost ポート 9050 を使うように手動で Firefox を設定してください。そしてアドレスバーに about:config と入力してください。network.proxy.socks_remote_dns を true に変更してブラウザを再起動してください。これで、全ての DNS リクエストは TOR の socks プロクシを通過するようになります。

Chromium

次のコマンドで chromium を起動してください:

$ chromium --proxy-server="socks://localhost:9050"

Just as with Firefox, you can setup a fast switch for example through Proxy SwitchySharp.

Once installed enter in its configuration page. Under the tab Proxy Profiles add a new profile Tor, if ticked untick the option Use the same proxy server for all protocols, then add localhost as SOCKS Host, 9050 to the respective port and select SOCKS v5.

Optionally you can enable the quick switch under the General tab to be able to switch beetween normal navigation and Tor network just by left-clicking on the Proxy SwitchySharp's icon.

Luakit

You can simply run:

$ torify luakit

HTTP プロクシー

Tor can be used with an HTTP proxy like Polipo or Privoxy, however the Tor dev team recommends using the SOCKS5 library since browsers directly support it.

Firefox

The FoxyProxy add-on allows you to specify multiple proxies for different URLs or for all your browsing. After restarting Firefox manually set Firefox to port 8118 on localhost, which is where Polipo or Privoxy are running. These settings can be access under Add > Standard proxy type. Select a proxy label (e.g Tor) and enter the port and host into the HTTP Proxy and SSL Proxy fields. To check if Tor is functioning properly visit the Tor Check website and toggle Tor.

Polipo

The Tor Project has created a custom Polipo configuration file to prevent potential problems with Polipo as well to provide better anonymity.

Keep in mind that Polipo is not required if you can use a SOCKS 5 proxy, which Tor starts automatically on port 9050. If you want to use Chromium with Tor, you do not need the Polipo package (see: #Chromium).

Privoxy

You can also use this setup in other applications like messaging (e.g. Jabber, IRC). Applications that support HTTP proxies you can connect to Privoxy (i.e. 127.0.0.1:8118). To use SOCKS proxy directly, you can point your application at Tor (i.e. 127.0.0.1:9050). A problem with this method though is that applications doing DNS resolves by themselves may leak information. Consider using Socks4A (e.g. with Privoxy) instead.

インスタントメッセージ

In order to use an IM client with tor, we do not need an http proxy like polipo/privoxy. We will be using tor's daemon directly which listens to port 9050 by default.

Pidgin

You can set up Pidgin to use Tor globally, or per account. To use Tor globally, go to Tools -> Preferences -> Proxy. To use Tor for specific accounts, go to Accounts > Manage Accounts, select the desired account, click Modify, then go to the Proxy tab. The proxy settings are as follows:

Proxy type 	SOCKS5
Host 	        127.0.0.1
Port 	        9150

Note that some time in 2013 the Port has changed from 9050 to 9150 if you use the Tor Browser Bundle. Try the other value if you receive a "Connection refused" message.

Irssi

Freenode does not recommend that you use Privoxy with Irssi. Instead they recommend using the mapaddress approach and running torify irssi to start it up. Therefore, add the following to /etc/tor/torrc:

mapaddress  10.40.40.40 p4fsi4ockecnea7l.onion

Freenode requires charybdis and ircd-seven's SASL mechanism for identifying to nickserv during connection. Download cap_sasl.pl, which enables SASL in Irssi, from the Freenode website (i.e. http://www.freenode.net/sasl/cap_sasl.pl) and save it to ~/.irssi/scripts/cap_sasl.pl

Then install perl-crypt-openssl-bignum, perl-crypt-blowfish and then perl-crypt-dh^AUR from the AUR.

Alternatively, you can install the modules using perl:

$ perl -MCPAN -e 'install Crypt::OpenSSL::Bignum Crypt::DH Crypt::Blowfish'

Start irssi

$ torify irssi

Load the script that will employ the SASL mechanism.

/script load cap_sasl.pl

Set your identification to nickserv, which will be read when connecting. Supported mechanisms are PLAIN and DH-BLOWFISH.

/sasl set network username password mechanism

Connect to Freenode:

/connect -network network 10.40.40.40

For more information check Accessing freenode Via Tor and the SASL README at freenode.net or the IRC/SILC Wiki article at torproject.org.

If you are receiving errors check the Cannot Connect to Freenode IRC using Irssi & Tor thread on the Arch Linux forums.

Pacman

Pacman のダウンロード操作 (リポジトリ DB, パッケージ, パブリックキー) を Tor ネットワークを通して行うことが可能です。 Though relatively extreme, this measure is useful to prevent an adversary (most likely at one's LAN or the mirror) from knowing a subset of the packages you have installed, at the cost of longer latency, lower throughput, possible suspicion, and possible failure (if Tor is being filtered via the current connection).

警告: It would be arguably simpler for an adversary, specifically one who desires to indiscriminately disseminate malware, to perform his/her activity by deploying malicious Tor exit node(s). Always use signed packages and verify new public keys by out-of-band means.

/etc/pacman.conf

...
XferCommand = /usr/bin/curl --socks5-hostname localhost:9050 -C - -f %u > %o
...

Tor サーバーを実行する

Tor ネットワークは人々が提供する帯域に頼っています。ネットワークに貢献する方法は複数あります。

Running a Tor bridge

This involves making your machine an 'entry node' for people who are having trouble connecting to Tor through traditional methods.

設定

According to https://www.torproject.org/docs/bridges , make your torrc be just these four lines:

   SocksPort 0
   ORPort 443
   BridgeRelay 1
   Exitpolicy reject *:*

トラブルシューティング

If you get "Could not bind to 0.0.0.0:443: Permission denied" errors on startup, you'll need to pick a higher ORPort (e.g. 8080), or perhaps forward the port in your router.

Running a "Middleman" relay

This means that your machine will contribute bandwidth to the 'internal' part of the network, acting as neither an entry nor exit point, merely forwarding bits to and from other Tor nodes/relays.

設定

You should at least share 20KiB/s:

Nickname tornickname
ORPort 9001
BandwidthRate 20 KB            # Throttle traffic to 20KB/s
BandwidthBurst 50 KB           # But allow bursts up to 50KB/s

Run Tor as middleman ( a relay):

ExitPolicy reject *:*

Running a Tor exit node

Any requests from a Tor user to the regular internet obviously need to exit the network somewhere, and exit nodes provide this vital service. To the accessed host, the request will appear as having originated from your machine. This means that running an exit node is generally considered more legally onerous than running other forms of Tor relays. Before becoming an exit relay, you may want to read Tips for Running an Exit Node With Minimal Harrasment.

Configuration

Using the torrc, you can configure which services you wish to allow through your exit node. Allow all traffic:

ExitPolicy accept	*:*

Allow only irc ports 6660-6667 to exit from node:

ExitPolicy accept *:6660-6667,reject *:* # Allow irc ports but no more

By default, Tor will block certain ports. You can use the torrc to overide this.

ExitPolicy accept *:119        # Accept nntp as well as default exit policy

TorDNS

The Tor 0.2.x series provides a built-in DNS forwarder. To enable it add the following lines to the Tor configuration file and restart the daemon:

/etc/tor/torrc

DNSPort 9053
AutomapHostsOnResolve 1
AutomapHostsSuffixes .exit,.onion

This will allow Tor to accept DNS requests (listening on port 9053 in this example) like a regular DNS server, and resolve the domain via the Tor network. A downside is that it's only able to resolve DNS queries for A-records; MX and NS queries are never answered. For more information see this Debian-based introduction.

DNS queries can also be performed through a command line interface by using tor-resolve. For example:

$ tor-resolve archlinux.org
66.211.214.131

Using TorDNS for all DNS queries

It is possible to configure your system, if so desired, to use TorDNS for all queries your system makes, regardless of whether or not you eventually use Tor to connect to your final destination. To do this, configure your system to use 127.0.0.1 as its DNS server and edit the 'DNSPort' line in /etc/tor/torrc to show:

DNSPort 53

Alternatively, you can use a local caching DNS server, such as dnsmasq or pdnsd, which will also compensate for TorDNS being a little slower than traditional DNS servers. The following instructions will show how to set up dnsmasq for this purpose.

Change the tor setting to listen for the DNS request in port 9053 and install dnsmasq.

Modify its configuration file so that it contains:

/etc/dnsmasq.conf

no-resolv
server=127.0.0.1#9053
listen-address=127.0.0.1

These configurations set dnsmasq to listen only for requests from the local computer, and to use TorDNS at its sole upstream provider. It is now neccessary to edit /etc/resolv.conf so that your system will query only the dnsmasq server.

/etc/resolv.conf

nameserver 127.0.0.1

Start the dnsmasq daemon.

Finally if you use dhcpd you would need to change its settings to that it does not alter the resolv configuration file. Just add this line in the configuration file:

/etc/dhcpcd.conf

nohook resolv.conf

If you already have an nohook line, just add resolv.conf separated with a comma.

Torify

torify will allow you use an application via the Tor network without the need to make configuration changes to the application involved. From the man page:

torify is a simple wrapper that calls tsocks with a tor specific configuration file. tsocks itself is a wrapper between the tsocks library and the application that you would like to run socksified

Usage example:

$ torify elinks checkip.dyndns.org
$ torify wget -qO- https://check.torproject.org/ | grep -i congratulations

Torify will not, however, perform DNS lookups through the Tor network. A workaround is to use it in conjunction with tor-resolve (described above). In this case, the procedure for the first of the above examples would look like this:

$ tor-resolve checkip.dyndns.org

208.78.69.70

$ torify elinks 208.78.69.70

トラブルシューティング

Problem with user value

If the tor daemon failed to start, then run the following command as root (or use sudo)

# tor

If you get the following error

May 23 00:27:24.624 [warn] Error setting groups to gid 43: "Operation not permitted".
May 23 00:27:24.624 [warn] If you set the "User" option, you must start Tor as root.
May 23 00:27:24.624 [warn] Failed to parse/validate config: Problem with User value. See logs for details.
May 23 00:27:24.624 [err] Reading config failed--see warnings above.

Then it means that the problem is with the User value, which likely means that one or more files or directories in your /var/lib/tor directory is not owned by tor. This can be determined by using the following find command:

find /var/lib/tor/ ! -user tor

Any files or directories listed in the output from this command needs to have its ownership changed. This can be done individually for each file like so:

chown tor:tor /var/lib/tor/filename

Or to change everything listed by the above find example, modify the command to this:

find /var/lib/tor/ ! -user tor -exec chown tor:tor {} \;

Tor should now start up correctly.

Still if you cannot start the tor service, run the service using root (this will switch back to the tor user). To do this, change the user name in the /etc/tor/torrc file:

User tor

Now modify the systemd's tor service file /usr/lib/systemd/system/tor.service as follows

[Service]
User=root
Group=root
Type=simple

The process will be run as tor user. For this purpose change user and group ID to tor and also make it writable:

# chown -R tor:tor /var/lib/tor/
# chmod -R 755 /var/lib/tor

Now save changes and run the daemon:

# systemctl --system daemon-reload
# systemctl start tor.service

Daemon fails on restart

If after issuing a daemon restart you have log entries similar to

Interrupt: we have stopped accepting new connections, and will shut down in 30 seconds. Interrupt again to exit now

and the daemon fails to start back up, a simple workaround is to open /etc/rc.d/tor in your favourite editor and increase the time waited between the shutting down and starting up again of the daemon. For example:

/etc/rc.d/tor

    ;;
  restart)
    $0 stop
    sleep 35
    $0 start
    ;;

This will allow Tor to shutdown cleanly, and restart after a safe period of time. Remember that this file may be overwritten by upgrades.

参照

• Running the Tor client on Linux/BSD/Unix
• Unix-based Tor Articles
• Software commonly integrated with Tor
• How to set up a Tor Hidden Service