If you may get an error cannot find SSL libraries, while configuring NRPE for Nagios,
 

./configure 

checking for type of socket size... size_t
checking for SSL headers... SSL headers found in /usr
checking for SSL libraries... configure: error: Cannot find ssl libraries


You need to install libssl-dev package and configure with openssl
 
# sudo apt-get install libssl-dev

To find out package information,
 
# apt-file search libssl | grep libssl-dev

libssl-dev: /usr/lib/x86_64-linux-gnu/libssl.a
libssl-dev: /usr/lib/x86_64-linux-gnu/libssl.so
libssl-dev: /usr/lib/x86_64-linux-gnu/pkgconfig/libssl.pc
libssl-dev: /usr/share/doc/libssl-dev/changelog.Debian.gz
libssl-dev: /usr/share/doc/libssl-dev/changelog.gz
libssl-dev: /usr/share/doc/libssl-dev/copyright


Then, execute the below command,
 
./configure --with-ssl=/usr/bin/openssl --with-ssl-lib=/usr/lib/x86_64-linux-gnu

Sample Output:

...
 General Options:
 -------------------------
 NRPE port:    5666
 NRPE user:    nagios
 NRPE group:   nagios
 Nagios user:  nagios
 Nagios group: nagios

Review the options above for accuracy.  If they look okay,
type 'make all' to compile the NRPE daemon and client.


Note : If you are using CentOS/Fedora run the below command,
# yum install openssl-devel