LPI 202-450 - LPIC-2 - Exam 202 (part 2 of 2), version 4.5

Server Name Indication (SNI) is an extension to the Transport Layer Security (TLS) protocol that allows a client to indicate which hostname it is trying to connect to at the start of the handshaking process1. This enables the server to present the appropriate certificate for the requested hostname, and thus allows multiple SSL/TLS secured virtual HTTP hosts to coexist on the same IP address12. SNI does not support transparent failover of TLS sessions from one web server to another, as this would require session resumption or renegotiation mechanisms1. SNI does not enable HTTP servers to update the DNS of their virtual hosts’ names using the X 509 certificates of the virtual hosts, as this would require a different protocol such as Dynamic DNS1. SNI does not provide a list of available virtual hosts to the client during the TLS handshake, as this would expose the server’s configuration and potentially compromise its security1. SNI submits the host name of the requested URL during the TLS handshake, as this is the information that the client needs to communicate to the server in order to select the correct certificate12. References:

Server Name Indication - IBM

Server Name Indication - Wikipedia

The standard port used by OpenVPN is 1194. OpenVPN is a VPN daemon that supports SSL/TLS security, ethernet bridging, TCP or UDP tunnel transport, and other features. OpenVPN can be configured to listen on any port, but the default port is 1194, which is registered with the IANA for OpenVPN. The port number can be specified in the OpenVPN configuration file using the port directive. For example:

port 1194

This will instruct OpenVPN to listen on port 1194. The port number must match on both the server and the client sides of the connection. The port number can also be specified as an argument to the openvpn command. For example:

openvpn --port 1194

This will run OpenVPN with port 1194 as the default port.

References:

Reference Manual For OpenVPN 2.6 | OpenVPN

Reference Manual For OpenVPN 2.0 | OpenVPN

Which ports to open for VPN PPTP, L2TP, IPsec, OpenVPN and … - ITIGIC

The root directive in Nginx defines the file system path from which the content of the server is retrieved. It can be placed in the http, server, or location contexts. The root directive specifies the root directory that will be used to search for a file. To obtain the path of a requested file, Nginx appends the request URI to the path specified by the root directive. For example, if the root directive is set to /var/www/html and the request URI is /index.php, Nginx will look for the file /var/www/html/index.php. References: Serving Static Content | NGINX DocumentationUnderstanding and Implementing FastCGI Proxying in Nginx

The option for BIND that is required in the global options to disable recursive queries on the DNS server by default is recursion no;. This option tells the server not to provide recursive query behavior to any client, unless overridden by a view or a zone statement. Recursive queries are queries that the server will try to resolve by contacting other servers if it does not have the answer in its cache or zones. Disabling recursive queries can improve the security and performance of the server, especially if it is only meant to serve authoritative zones123 References:

BIND: Stop Recursion DNS Under Linux / UNIX - nixCraft

How to Disable External DNS Recursion in BIND? | DeviceTests

bind - How to Disable External DNS recursion? - Ask Ubuntu

 PAM modules are organized and stored as shared object files within the /lib/ directory hierarchy. A shared object file is a file that contains executable code and data that can be loaded into memory and used by one or more programs. This allows PAM modules to be dynamically loaded and unloaded by the PAM library as needed, without requiring recompilation or relinking of the programs that use them. The /lib/ directory hierarchy contains subdirectories for different architectures and operating systems, such as /lib/x86_64-linux-gnu/ or /lib64/. The PAM modules are usually located in a subdirectory named security, such as /lib/x86_64-linux-gnu/security/ or /lib64/security/. The PAM modules have names that start with pam_ and end with .so, such as pam_unix.so or pam_cracklib.so12.

References:

PAM Modules: A section from the Linux-PAM System Administrators’ Guide that explains what PAM modules are, how they are named, and where they are located.

An introduction to Pluggable Authentication Modules (PAM) in Linux: An article from Red Hat that introduces the concept and usage of PAM in Linux, which includes a description of PAM modules and their location.