For CentOS, this is now available in the EPEL repo

mod_auth_cas (https://github.com/Jasig/mod_auth_cas) is an Apache module that plugs into the Apache mod_auth framework, to provide authentication against a Jasig CAS SSO server.  Unfortunately development on it seems to have stalled, and it currently doesn’t support Apache 2.4 – https://github.com/Jasig/mod_auth_cas/issues/49.

There is a fork that does support Apache 2.4, so this willl cover how to build and install it.

# Clone the forked github repo
git clone https://github.com/klausdieterkrannich/mod_auth_cas.git .

# install development libraries
yum install gcc httpd-devel openssl-devel libcurl-devel automake

# Run configure
./configure

# Run Make
make

# If you get errors like:
/opt/mod_auth_cas/missing: line 81: aclocal-1.12: command not found
WARNING: 'aclocal-1.12' is missing on your system.
# then symlink the binaries as follows:
ln -s /usr/bin/aclocal /usr/bin/aclocal-1.12
ln -s /usr/bin/automake /usr/bin/automake-1.12
# and run make again

# Assuming it built OK, then install it:
make install

# On CentOS this will put the binaries into:
#/usr/lib64/httpd/modules
# and you can then copy them from here to your production systems.