Firing UP OpenAppID

 Installation of OpenAppID pre-processor for Snort IDS
I have heard many good things about OpenAppID pre-processor for snort and wanted to include it in my existing snort installation before up-gradation. This pre-processor allows you to detect application running on your network and can be a great aid in identifying suspicious applications or any application not confirming to your company policy.

There is a good installation note for OpenAppID from snort team but, I felt, there are some missing links. So, here is the sequence that is to be followed for enabling OpenAppID for your snort IDS installation on CentOS or its equivalent linux distribution system:

Make sure that the following rpms are present on the system. If not install them using yum.

# yum install ethtool make zlib zlib-devel gcc gcc-c++ libtool.x86_64 pcre-devel libpcap libpcap-devel flex bison tcpdump autoconf unzip python-setuptools python-devel lua lua-devel


Download snort and its associated libraries from snort site:

    Download snort-2.9.7.2
    Download daq-2.0.4
    Download libdnet-1.12
    Register yourself on snort.org site and download registered rule set - snortrules-snapshot-2972
    Download snort-openappid
    Download just-in-time compiler LuaJIT-2.0.3

All the downloaded packages are saved under /home/admin/install directory.

Now, let us compile and install them one-by-one.

# cd /home/admin/installs
# tar xzvf libdnet-1.12.tar.gz
# cd libdnet-1.12/
# ./configure
# make
# make install
# cd ..
# tar xzvf LuaJIT-2.0.3.tar.gz
# cd LuaJIT-2.0.3/
# make
# make install
# cd ..
# tar -xzvf daq-2.0.4.tar.gz
# cd daq-2.0.4/
# ./configure
# make
# make install
# ldconfig
# cd ..

Now, compile snort with openAppID pre-processor.

# tar -xvf snort-2.9.7.2.tar.gz
# cd snort-2.9.7.2
# ./configure --enable-sourcefire --enable-open-appid
# make
# make install
# which snort
/usr/local/bin/snort
# /usr/local/bin/snort --version

,,_ -*> Snort! <*-
o" )~ Version 2.9.7.2 GRE (Build 177)

Now, configure snort configuration files and create some directories:

# mkdir /etc/snort # For configuration
# mkdir /var/log/snort # For log data
# mkdir /usr/local/lib/snort_dynamicrules # For dynamic rules
# mkdir /etc/snort/rules # For normal text rules
# touch /etc/snort/white_list.rules # For white lists
# touch /etc/snort/black_list.rules # For black lists

A set of configuration files are included in the snort tarball. These files need be copied into /etc/snort/ directory.

# cd /home/admin/installs/snort-2.9.7.2
# cp etc/* /etc/snort/

This process will copy the files - file_magic.conf,snort.conf,unicode.map,classification.config,gen-msg.map,reference.config,threshold.conf to /etc/snort

Now, extract snort registered rules(snort-snapshot-2.9.7.2) and copy them to /etc/snort

# cd /home/admin/installs
# mkdir -p snort_rules
# mv snortrules-snapshot-2.9.7.2.tar.gz snort_rules
# cd snort_rules
# tar -zxvf snortrules-snapshot-2.9.7.2.tar.gz
# cp -r preproc_rules /etc/snort
# cp -r rules /etc/snort
# cp -r so_rules /etc/snort

The next step is configure  snort configuration file - /etc/snort/snort.conf. The following changes are required to be made:

# vim /etc/snort/snort.conf

RULE_PATH /etc/snort/rules
SO_RULE_PATH /etc/snort/so_rules
PREPROC_RULE_PATH /etc/snort/preproc_rules
WHITE_LIST_PATH /etc/snort
BLACK_LIST_PATH /etc/snort




# comment path to dynamic rules libraries
#dynamicdetection directory /usr/local/lib/snort_dynamicrules

The next step is to add the configuration for the OpenAppID preprocessor to the snort.conf file. Find the lines for the reputation preprocessor. Just after the reputation preprocessor and before Step 6 we will add another preprocessor setting.

preprocessor appid: app_stats_filename appstats-u2.log, \
   app_stats_period 60, \
   app_detector_dir /usr/local/snort

This will turn on the OpenAppID preprocessor. The first line names the configuration file to which application statistics will be logged, the second one indicates the time period used to sample this data and the third one specifies the directory which contains the odp directory we extracted from the Open App ID Detector package.

Now, let us configure output section in snort.conf.

Again open snort.conf file and look into Step 6 to find the lines explaining the unified2 output type.

In that section add the following line:
output unified2: filename snort_openappid.log, limit 128, appid_event_types

Now fire up Snort instance:

# /usr/local/snort/bin/snort -c /usr/local/snort/etc/snort.conf -i eth#

Where eth# is which ever interface you will be monitoring with (e.g. eth0).


Possible Errors

1) daq_static library not found:

# ./configure: line 15736: daq-modules-config: command not found
checking for daq_load_modules in -ldaq_static... no

   ERROR!  daq_static library not found, go get it from
   http://www.snort.org/.

This happens if daq_static library is not in the path. So. add "/usr/local/bin" to the path variable.

[root@psj snort-2.9.7.2]# which daq_static
/usr/bin/which: no daq_static in (/sbin:/bin:/usr/sbin:/usr/bin)
[root@psj snort-2.9.7.2]# which daq-modules-config
/usr/bin/which: no daq-modules-config in (/sbin:/bin:/usr/sbin:/usr/bin)
[root@psj snort-2.9.7.2]# export PATH=$PATH:/usr/local/bin


2) LuaJIT library not found:


[root@psj snort-2.9.7.2]# ./configure --enable-sourcefire --enable-open-appid
checking for a BSD-compatible install... /usr/bin/install -c

checking pkg-config is at least version 0.9.0... yes
checking for luajit... no

   ERROR!  LuaJIT library not found. For better performance, go get it from
   http://www.luajit.org/.
configure: error: "Fatal!"

To correct, install  latest version of LuaJIT from http://luajit.org/download.html

3) libluajit-5.1.so.2: cannot open shared object file: No such file or directory

  Loading dynamic preprocessor library /usr/local/lib/snort_dynamicpreprocessor//libsf_reputation_preproc.so... done
  Loading dynamic preprocessor library /usr/local/lib/snort_dynamicpreprocessor//libsf_dce2_preproc.so... done
  Loading dynamic preprocessor library /usr/local/lib/snort_dynamicpreprocessor//libsf_modbus_preproc.so... done
  Loading dynamic preprocessor library /usr/local/lib/snort_dynamicpreprocessor//libsf_appid_preproc.so... ERROR: Failed to load /usr/local/lib/snort_dynamicpreprocessor//libsf_appid_preproc.so: libluajit-5.1.so.2: cannot open shared object file: No such file or directory
Fatal Error, Quitting..

To correct it, do the following:

[root@psj snort-2.9.7.2]# ldd /usr/local/lib/snort_dynamicpreprocessor/libsf_appid_preproc.so
    linux-gate.so.1 =>  (0x007d8000)
    libluajit-5.1.so.2 => not found
    libdnet.1 => /usr/local/lib/libdnet.1 (0x00c79000)
    libpcre.so.0 => /lib/libpcre.so.0 (0x00a7c000)
    libnsl.so.1 => /lib/libnsl.so.1 (0x00d6f000)
    libm.so.6 => /lib/libm.so.6 (0x00667000)
    libcrypto.so.10 => /usr/lib/libcrypto.so.10 (0x007d9000)
    libdl.so.2 => /lib/libdl.so.2 (0x00eef000)
    libsfbpf.so.0 => /usr/local/lib/libsfbpf.so.0 (0x005c5000)
    libpcap.so.1 => /usr/local/lib/libpcap.so.1 (0x00114000)
    libz.so.1 => /lib/libz.so.1 (0x00e07000)
    libpthread.so.0 => /lib/libpthread.so.0 (0x006e5000)
    libc.so.6 => /lib/libc.so.6 (0x00aac000)
    /lib/ld-linux.so.2 (0x002b8000)

# find /usr/ -name libluajit-5.1.so.2 # Check where is the required .so
/usr/local/lib/libluajit-5.1.so.2

[root@psj snort-2.9.7.2]# ls -l /usr/local/lib/libluajit-5.1.so.2
lrwxrwxrwx 1 root root 22 Apr 10 12:31 /usr/local/lib/libluajit-5.1.so.2 -> libluajit-5.1.so.2.0.3

# ldconfig

Again, try to run snort instance:

# snort -c /etc/snort/snort.conf -T


If you wish to write your own OpenAppID plugins or extend/tailor the functionality, technical details are available in this document > https://usermanual.wiki/Pdf/OpenDetectorDeveloperGuide.729399446/html.

The following article were very useful while installing and configuring OpenAppID:
1) http://blog.snort.org/2014/03/firing-up-openappid.html
2) http://phucnw.blogspot.in/search?q=snort
3) http://puremonkey2010.blogspot.in/2014/10/snort-customized-appid-lua-script-as.html?m=1
4) https://www.bilgiguvenligi.gov.tr/saldiri-tespit-sistemleri/snort-openappid-ile-uygulama-farkindaligi.html

The following video nicely explains the concepts behind OpenAppID:
1) http://www.irongeek.com/i.php?page=videos/derbycon4/t402-snort-openappid-how-to-build-an-open-source-next-generation-firewall-adam-hogan
2) http://blog.snort.org/2014/06/openappid-training-videos-how-to-create.html

Presentation links:
1) https://www.snort.org/documents/openappid-detection-webinar
2) http://www.centralohioissa.org/wp-content/uploads/2014/07/OpenAppID-ISSA_Rafeeq-Rehman.pdf
3) https://www.snort.org/documents/55