apache2のhttpd-vhosts.conf、httpd-ssl.confにおける複数ドメインに対応したSSL設定例を紹介してみます。
/usr/local/apache2/conf/extra/httpd-vhosts.confの設定例
DocumentRoot /usr/local/apache2/htdocs/vhost1
ServerName www.vhost1.com
ServerAlias www.vhost1.com
ErrorLog logs/wwww.vhost1.com-error_log
CustomLog logs/www.vhost1.com-access_log common
DocumentRoot /usr/local/apache2/htdocs/vhost2
ServerName www.vhost2.com
ServerAlias www.vhost2.com
ErrorLog logs/wwww.vhost2.com-error_log
CustomLog logs/www.vhost2.com-access_log common
/usr/local/apache2/conf/extra/httpd-ssl.confの設定例
NameVirtualHost *:443//この行の記述が必要
DocumentRoot "/usr/local/apache2/htdocs/vhost1"
ServerName www.vhost1.com
SSLEngine on
SSLCipherSuite ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP:+eNULL
SSLCertificateFile /usr/local/apache2/conf/server1.crt
SSLCertificateKeyFile /usr/local/apache2/conf/server1.key
DocumentRoot "/usr/local/apache2/htdocs/vhost2"
ServerName www.vhost2.com
SSLEngine on
SSLCipherSuite ALL:!ADH:!EXPORT56:RC4+RSA:+HIGH:+MEDIUM:+LOW:+SSLv2:+EXP:+eNULL
SSLCertificateFile /usr/local/apache2/conf/server2.crt
SSLCertificateKeyFile /usr/local/apache2/conf/server2.key
上記の様に１組のserver.crt、server.keyで複数のドメインでSSLの証明を可能に出来るようです。
下記サイトを参考にしました
https://centossrv.com/apache-ssl.shtml
http://d.hatena.ne.jp/eth0jp/20090920/1253394739
http://cmshikaku.com/feature/?p=1429