Add documentation to the module with testing steps

documentation/modules/auxiliary/scanner/ntp/ntp_nak_to_the_future.rb.md

@@ -0,0 +1,68 @@
+## Vulnerable Application
+
+## Verification Steps
+
+1. Use the supplied Dockerfile to start a vulnerable instance of the application
+   1. Build it with: `docker build -t ntpd:4.2.8p3 .`
+   1. Run it with: `docker run --rm -it --name ntp-server -p 123:123/udp ntpd:4.2.8p3`
+1. Start `msfconsole` and use the module
+1. Set the `RHOSTS` value as necessary
+1. Run the module and see that the target is vulnerable
+
+### Dockerfile
+
+```
+ARG version=4.2.8p3
+FROM ubuntu:16.04
+ARG version
+
+# Install dependencies
+RUN apt-get update && apt-get install -y \
+    wget \
+    build-essential \
+    libcap-dev \
+    libssl-dev && \
+    apt-get clean
+
+# Download and build NTPD
+WORKDIR /tmp
+RUN wget https://www.eecis.udel.edu/~ntp/ntp_spool/ntp4/ntp-4.2/ntp-$version.tar.gz && \
+    tar -xzf ntp-$version.tar.gz && \
+    cd ntp-$version && \
+    ./configure --prefix=/usr/local --enable-linuxcaps && \
+    make && \
+    make install && \
+    cd .. && \
+    rm -rf ntp-$version*
+
+# Add configuration file
+COPY ntp.conf /etc/ntp.conf
+
+# Expose NTP port (123)
+EXPOSE 123/udp
+
+# Run ntpd
+ENTRYPOINT ["/usr/local/bin/ntpd"]
+CMD ["-g", "-d", "-d"]
+```
+
+## Options
+
+## Scenarios
+
+### Ubuntu 16.04 NTPd 4.2.8p3
+
+```
+metasploit-framework (S:0 J:0) auxiliary(scanner/ntp/ntp_nak_to_the_future) > set RHOSTS 192.168.159.128, 192.168.159.10
+RHOSTS => 192.168.159.128, 192.168.159.10
+metasploit-framework (S:0 J:0) auxiliary(scanner/ntp/ntp_nak_to_the_future) > run
+[+] 192.168.159.128:123 - NTP - VULNERABLE: Accepted a NTP symmetric active association
+[*] Scanned 1 of 2 hosts (50% complete)
+[*] Scanned 1 of 2 hosts (50% complete)
+[*] Scanned 1 of 2 hosts (50% complete)
+[*] Scanned 1 of 2 hosts (50% complete)
+[*] Scanned 1 of 2 hosts (50% complete)
+[*] Scanned 2 of 2 hosts (100% complete)
+[*] Auxiliary module execution completed
+metasploit-framework (S:0 J:0) auxiliary(scanner/ntp/ntp_nak_to_the_future) >
+```