CentOS 6
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Basic Auth + PAM
Limit accesses on specific web pages and use OS users for authentication with SSL connection.
[2] For example, set Basic Auth under the [/var/www/html/auth-pam] directory.
# install from EPEL

[root@www ~]#
yum --enablerepo=epel -y install mod_authnz_external pwauth
[root@www ~]#
vi /etc/httpd/conf.d/authnz_external.conf
# add follows to the end

<Directory /var/www/html/auth-pam>
    AuthType Basic
    AuthName "PAM Authentication"
    AuthBasicProvider external
    AuthExternal pwauth
    require valid-user

# create a test page

[root@www ~]#
mkdir /var/www/html/auth-pam

[root@www ~]#
vi /var/www/html/auth-pam/index.html
<div style="width: 100%; font-size: 40px; font-weight: bold; text-align: center;">
Test Page for PAM Auth

[root@www ~]#
/etc/rc.d/init.d/httpd restart

Stopping httpd:     [  OK  ]
Starting httpd:     [  OK  ]
[3] Access to the test page with a Web browser on Client and authenticate with a user which is on OS.
[4] Just accessed.