VineLinuxパフォーマンスアッププロジェクト:0159

■SSL通信を実装してみよう!(2)■

 SSL通信を実装してみよう!(1)ではサーバの証明書を作成する部分まで紹介しました。このページではApacheにSSL通信を設定する処理や実際にSSL通信時に表示される画面について説明していきます。

●Apache設定ファイルの編集

 ApacheのSSL設定ファイルであるssl.confを編集します。このファイルは/etc/apache2/conf.d/以下にありますので、テキストエディタ等で開いてください。
 そして真ん中ほどから始まる"SSL Virtual Host Context"セクションに対して、以下の赤字部分をご自分の設定した環境に合わせて編集します。

##
## SSL Virtual Host Context
##

<VirtualHost _default_:443>

#  General setup for the virtual host
DocumentRoot "/home/httpd/html" ←Apacheのドキュメントルートディレクトリ名を指定する
ServerName mkserver.dip.jp:443 ←ドメイン名とSSLに使用するポート番号(443)を指定する
ServerAdmin root@localhost ←連絡先メールアドレスを指定する(ウソでもOK)
ErrorLog /home/httpd/html/log/ssl_error_log ←アクセスエラーログの出力先を指定する(事前にディレクトリを作成しておく必要があります)
TransferLog /home/httpd/html/log/ssl_access_log ←アクセスログの出力先を指定する(事前にディレクトリを作成しておく必要があります)

#   SSL Engine Switch:
#   Enable/Disable SSL for this virtual host.
SSLEngine on

#   SSL Cipher Suite:
#   List the ciphers that the client is permitted to negotiate.
#   See the mod_ssl documentation for a complete list.
SSLCipherSuite ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP:+eNULL

#   Server Certificate:
#   Point SSLCertificateFile at a PEM encoded certificate.  If
#   the certificate is encrypted, then you will be prompted for a
#   pass phrase.  Note that a kill -HUP will prompt again. A test
#   certificate can be generated with `make certificate' under
#   built time. Keep in mind that if you've both a RSA and a DSA
#   certificate you can configure both in parallel (to also allow
#   the use of DSA ciphers, etc.)
SSLCertificateFile /usr/share/ssl/certs/server.pem ←CA(認証局)の証明書があるファイルまでのディレクトリを指定する(通常はこの指定でOK)
#SSLCertificateFile /etc/apache2/conf/ssl.crt/server.crt
#SSLCertificateFile /etc/apache2/conf/ssl.crt/server-dsa.crt

#   Server Private Key:
#   If the key is not combined with the certificate, use this
#   directive to point at the key file.  Keep in mind that if
#   you've both a RSA and a DSA private key you can configure
#   both in parallel (to also allow the use of DSA ciphers, etc.)
SSLCertificateKeyFile /usr/share/ssl/certs/server.key ←作成したサーバの秘密かぎがあるファイルまでのディレクトリを指定する
#SSLCertificateKeyFile /etc/apache2/conf/ssl.key/server.key
#SSLCertificateKeyFile /etc/apache2/conf/ssl.key/server-dsa.key

#   Server Certificate Chain:
#   Point SSLCertificateChainFile at a file containing the
#   concatenation of PEM encoded CA certificates which form the
#   certificate chain for the server certificate. Alternatively
#   the referenced file can be the same as SSLCertificateFile
#   when the CA certificates are directly appended to the server
#   certificate for convinience.
#SSLCertificateChainFile /etc/apache2/conf/ssl.crt/ca.crt

#   Certificate Authority (CA):
#   Set the CA certificate verification path where to find CA
#   certificates for client authentication or alternatively one
#   huge file containing all of them (file must be PEM encoded)
#   Note: Inside SSLCACertificatePath you need hash symlinks
#         to point to the certificate files. Use the provided
#         Makefile to update the hash symlinks after changes.
#SSLCACertificatePath /etc/apache2/conf/ssl.crt
#SSLCACertificateFile /etc/apache2/conf/ssl.crt/ca-bundle.crt

#   Certificate Revocation Lists (CRL):
#   Set the CA revocation path where to find CA CRLs for client
#   authentication or alternatively one huge file containing all
#   of them (file must be PEM encoded)
#   Note: Inside SSLCARevocationPath you need hash symlinks
#         to point to the certificate files. Use the provided
#         Makefile to update the hash symlinks after changes.
#SSLCARevocationPath /etc/apache2/conf/ssl.crl
#SSLCARevocationFile /etc/apache2/conf/ssl.crl/ca-bundle.crl

#   Client Authentication (Type):
#   Client certificate verification type and depth.  Types are
#   none, optional, require and optional_no_ca.  Depth is a
#   number which specifies how deeply to verify the certificate
#   issuer chain before deciding the certificate is not valid.
#SSLVerifyClient require
#SSLVerifyDepth  10

#   Access Control:
#   With SSLRequire you can do per-directory access control based
#   on arbitrary complex boolean expressions containing server
#   variable checks and other lookup directives.  The syntax is a
#   mixture between C and Perl.  See the mod_ssl documentation
#   for more details.
#<Location />
#SSLRequire (    %{SSL_CIPHER} !~ m/^(EXP|NULL)/ \
#            and %{SSL_CLIENT_S_DN_O} eq "Snake Oil, Ltd." \
#            and %{SSL_CLIENT_S_DN_OU} in {"Staff", "CA", "Dev"} \
#            and %{TIME_WDAY} >= 1 and %{TIME_WDAY} <= 5 \
#            and %{TIME_HOUR} >= 8 and %{TIME_HOUR} <= 20       ) \
#           or %{REMOTE_ADDR} =~ m/^192\.76\.162\.[0-9]+$/
#</Location>

#   SSL Engine Options:
#   Set various options for the SSL engine.
#   o FakeBasicAuth:
#     Translate the client X.509 into a Basic Authorisation.  This means that
#     the standard Auth/DBMAuth methods can be used for access control.  The
#     user name is the `one line' version of the client's X.509 certificate.
#     Note that no password is obtained from the user. Every entry in the user
#     file needs this password: `xxj31ZMTZzkVA'.
#   o ExportCertData:
#     This exports two additional environment variables: SSL_CLIENT_CERT and
#     SSL_SERVER_CERT. These contain the PEM-encoded certificates of the
#     server (always existing) and the client (only existing when client
#     authentication is used). This can be used to import the certificates
#     into CGI scripts.
#   o StdEnvVars:
#     This exports the standard SSL/TLS related `SSL_*' environment variables.
#     Per default this exportation is switched off for performance reasons,
#     because the extraction step is an expensive operation and is usually
#     useless for serving static content. So one usually enables the
#     exportation for CGI and SSI requests only.
#   o CompatEnvVars:
#     This exports obsolete environment variables for backward compatibility
#     to Apache-SSL 1.x, mod_ssl 2.0.x, Sioux 1.0 and Stronghold 2.x. Use this
#     to provide compatibility to existing CGI scripts.
#   o StrictRequire:
#     This denies access when "SSLRequireSSL" or "SSLRequire" applied even
#     under a "Satisfy any" situation, i.e. when it applies access is denied
#     and no other module can change it.
#   o OptRenegotiate:
#     This enables optimized SSL connection renegotiation handling when SSL
#     directives are used in per-directory context. 
#SSLOptions +FakeBasicAuth +ExportCertData +CompatEnvVars +StrictRequire
<Files ~ "\.(cgi|shtml|phtml|php3?)$">
    SSLOptions +StdEnvVars
</Files>
<Directory "/var/www/cgi-bin">
    SSLOptions +StdEnvVars
</Directory>

#   SSL Protocol Adjustments:
#   The safe and default but still SSL/TLS standard compliant shutdown
#   approach is that mod_ssl sends the close notify alert but doesn't wait for
#   the close notify alert from client. When you need a different shutdown
#   approach you can use one of the following variables:
#   o ssl-unclean-shutdown:
#     This forces an unclean shutdown when the connection is closed, i.e. no
#     SSL close notify alert is send or allowed to received.  This violates
#     the SSL/TLS standard but is needed for some brain-dead browsers. Use
#     this when you receive I/O errors because of the standard approach where
#     mod_ssl sends the close notify alert.
#   o ssl-accurate-shutdown:
#     This forces an accurate shutdown when the connection is closed, i.e. a
#     SSL close notify alert is send and mod_ssl waits for the close notify
#     alert of the client. This is 100% SSL/TLS standard compliant, but in
#     practice often causes hanging connections with brain-dead browsers. Use
#     this only for browsers where you know that their SSL implementation
#     works correctly. 
#   Notice: Most problems of broken clients are also related to the HTTP
#   keep-alive facility, so you usually additionally want to disable
#   keep-alive for those clients, too. Use variable "nokeepalive" for this.
#   Similarly, one has to force some clients to use HTTP/1.0 to workaround
#   their broken HTTP/1.1 implementation. Use variables "downgrade-1.0" and
#   "force-response-1.0" for this.
SetEnvIf User-Agent ".*MSIE.*" \
         nokeepalive ssl-unclean-shutdown \
         downgrade-1.0 force-response-1.0

#   Per-Server Logging:
#   The home of a custom SSL log file. Use this when you want a
#   compact non-error SSL logfile on a virtual host basis.
CustomLog /home/httpd/html/log/ssl_request_log \
          "%t %h %{SSL_PROTOCOL}x %{SSL_CIPHER}x \"%r\" %b"
 ↑SSLリクエストログの出力先を指定する(事前にディレクトリを作成しておく必要があります)
</VirtualHost>                                  

 修正が終わったら一度Apacheを再起動させます。

  /etc/rc.d/init.d/apache2 restart

 これで起動失敗しなければSSL処理ができているはずです。

●さあSSL通信の出番です!

 SSL通信を許可するためにはルータの設定で443番ポートを空ける必要があります。市販のブロードバンドルータをご使用の場合は説明書等に従って空けてください。

 iptablesを使用してルータを構築されている場合には

  iptables -L

 で空いているか確認してください。もし空いていない場合には以下のコマンドを実行して空けてください。

  iptables -A INPUT -p tcp --dport 443 -j ACCEPT
  iptables -A INPUT -p tcp --sport 443 -j ACCEPT
  /etc/init.d/iptables save
  /etc/init.d/iptables restart


 ちゃんと空いていることを確認できたらhttps://ドメイン名(またはIPアドレス)でアクセスしてみましょう。すると下のような画面が表示されるはずです。

certificate.png(80479 byte)

↑SSL通信警告画面(1)


 ここで「今後この証明書を受け入れる」を選択してOKをクリックすることで証明書のインストールが自動的に行われ、以降このような警告画面は表示されなくなります。

●こんな画面が出たら・・・

 実験機やプライベートネットワーク内でSSL通信を構築した場合、上の画面に続いて以下のような画面が表示されることがあります。

certificate2.png(42791 byte)

↑SSL通信警告画面(2)


 これは証明書に記述されているドメイン名と実際のドメイン名とが一致しないために表示されるものです。実際SSL通信を行いたいWebサーバで構築し、インターネット経由でアクセスすれば表示されなくなるはずです。

 ※今回紹介したSSL通信の実装はごく簡単なものなので、セキュリティは完全ではありません。完璧に近づけたい場合、外部の証明書発行サービスなどにお願いして証明書を管理してもらうような流れになります。

●Special Thanks!: Vine Linuxで自宅サーバー 〜Webサーバー通信暗号化(Apache2 + mod_SSL)〜
http://vine.1-max.net/apache2-ssl.html




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