Added page to site that documents how to take daily snapshots of the NVD,

and run D-C cli against those snapshots.

src/site/markdown/data/cachenvd.md

@@ -0,0 +1,93 @@
+Snapshotting the NVD
+====================
+
+The [Mirroring the NVD from NIST](./mirrornvd.html) topic describes briefly
+how to use the [Nist-Data-Mirror](https://github.com/stevespringett/nist-data-mirror/)
+project to cache the NVD locally and run Dependency Check (D-C) against the
+local cache.
+
+This topic goes into a bit more depth with the [cli](../dependency-check-cli/index.html)
+client, focusing on the following use case.
+
+1. You wish to have daily local snapshots of the NVD, so that
+2. in order to compare later runs of D-C with earlier runs, you can compare
+   "apples with apples".
+
+In other words: It is sometimes desirable to run a comparison D-C analysis
+against the same NVD snapshot that an earlier D-C report used.
+
+In the steps below, concrete examples will be given assuming an Ubuntu Linux
+system. Hopefully, enough explanation is provided that the steps can easily be
+translated to other systems.
+
+Build Nist-Data-Mirror
+----------------------
+
+1. Perform a "git clone" of [Nist-Data-Mirror](https://github.com/stevespringett/nist-data-mirror/)
+2. Install gradle, if necessary. See [here](http://gradle.org/gradle-download/)
+   or your Linux distributions package management system. (e.g.,
+   `sudo apt-get install gradle`).
+3. Follow the [build instructions](https://github.com/stevespringett/nist-data-mirror/blob/master/README.md#user-content-build).
+   You will be left with a build artifact called `nist-data-mirror-1.0.0.jar`.
+
+Set Up a Daily NVD Download Job
+-------------------------------
+
+On Linux, the way to do this using the [cron daemon](http://linux.die.net/man/8/cron).
+"Cron jobs" are configured by invoking [crontab](http://linux.die.net/man/5/crontab).
+For example, invoke `crontab -e` to add a line like the following to your
+crontab file:
+
+    4 5 * * * ~/.local/bin/nvd_download.sh ~/NVD ~/.local/jars
+
+This would run a job on your system at 4:05 AM daily to run the
+[nvd_download.sh](general/nvd_download.sh) shell script with the two given
+arguments. The script is simple:
+
+```sh
+#!/bin/sh
+NVD_ROOT=$1/`date -I`
+JAR_PATH=$2/nist-data-mirror-1.0.0.jar
+java -jar $JAR_PATH $NVD_ROOT
+rm $NVD_ROOT/*.xml # D-C works directly with .gz files anyway.
+```
+
+Nist-Data-Mirror will automatically create the directory, download the
+.xml.gz files, and extract the .xml files alongside them. Given the parameters
+in the cron example above, the new directory will be `~/NVD/2015-08-03` if
+executed on August 3<sup>rd</sup>, 2015. The download for 2015-08-03 pulled 47
+MiB, and took up a total of 668 MiB after extracting from the compressed
+archive format. It turns out that D-C works directly with the .xml.gz files,
+so the above script preserves disk space by deleting the .xml files.
+
+Invoke the Command-Line Using a Specific Daily Snapshot
+-------------------------------------------------------
+
+An example script named [dep-check-date.sh](general/dep-check-date.sh) is
+shown below, which facilitates a D-C scan against an arbitrary NVD snapshot:
+
+```sh
+#!/bin/sh
+CLI_LOCATION=~/.local/dependency-check-1.2.11
+CLI_SCRIPT=$CLI_LOCATION/bin/dependency-check.sh
+NVD_PATH=$1/`date -I -d $2`
+NVD=file://$NVD_PATH
+shift 2 # We've used the first two params. The rest go to CLI_SCRIPT.
+$CLI_SCRIPT --cveUrl20Base $NVD/nvdcve-2.0-%d.xml.gz \
+    --cveUrl12Base $NVD/nvdcve-%d.xml.gz \
+    --cveUrl20Modified $NVD/nvdcve-2.0-Modified.xml.gz \
+    --cveUrl12Modified $NVD/nvdcve-Modified.xml.gz \
+    --data $NVD_PATH $@
+```
+
+The script takes advantage of the `date` command's ability to parse a variety
+of date formats. The following invokation would successfully point to the
+`~/NVD/2015-08-03` folder.
+
+    $ ./dep-check-date.sh ~/NVD "08/03/2015" -app Foo -scan /path/to/Foo --out ~/DCreports/FooFollowup/
+
+If today happened to be August 4th, 2015, `"yesterday"` would also have worked
+as well. Also notice the usage of the `--data` parameter. This places the
+H2 database file directly in the folder alongside the .xml.gz files. This is
+critical, so that D-C doesn't run against another version of the database,
+like the usual default in `$CLI_LOCATION/data`.

src/site/resources/general/dep-check-date.sh

@@ -0,0 +1,11 @@
+#!/bin/sh
+CLI_LOCATION=~/.local/dependency-check-1.2.11
+CLI_SCRIPT=$CLI_LOCATION/bin/dependency-check.sh
+NVD_PATH=$1/`date -I -d $2`
+NVD=file://$NVD_PATH
+shift 2 # We've used the first two params. The rest go to CLI_SCRIPT.
+$CLI_SCRIPT --cveUrl20Base $NVD/nvdcve-2.0-%d.xml.gz \
+    --cveUrl12Base $NVD/nvdcve-%d.xml.gz \
+    --cveUrl20Modified $NVD/nvdcve-2.0-Modified.xml.gz \
+    --cveUrl12Modified $NVD/nvdcve-Modified.xml.gz \
+    --data $NVD_PATH $@

src/site/resources/general/nvd_download.sh

@@ -0,0 +1,5 @@
+#!/bin/sh
+NVD_ROOT=$1/`date -I`
+JAR_PATH=$2/nist-data-mirror-1.0.0.jar
+java -jar $JAR_PATH $NVD_ROOT
+rm $NVD_ROOT/*.xml # D-C works directly with .gz files anyway.

src/site/site.xml

@@ -87,6 +87,7 @@ Copyright (c) 2013 Jeremy Long. All Rights Reserved.
                 <item collapse="true" name="Internet Access Required" href="./data/index.html">
                     <item name="Proxy" href="./data/proxy.html" />
                     <item name="Mirroring NVD" href="./data/mirrornvd.html" />
+                    <item name="Snapshotting the NVD" href="./data/cachenvd.html" />
                     <item name="Central DB" href="./data/database.html" />
                 </item>
                 <item name="Related Work" href="./related.html">