Host Attribute Table

cTar

On an Ubuntu based Snort installation, very little configuration done, I was able to load my host-attribute-table.xml just fine. This is a PFSENSE issue.

Without any help in the forums from Netgate, the only path forward I see is to directly edit config files, or at least see if it is possible to get the table loaded that way.

bmeeks

@cTar said in Host Attribute Table:

On an Ubuntu based Snort installation, very little configuration done, I was able to load my host-attribute-table.xml just fine. This is a PFSENSE issue.

Without any help in the forums from Netgate, the only path forward I see is to directly edit config files, or at least see if it is possible to get the table loaded that way.

Okay. I will continue to look for the problem. I'm working on another Snort feature now and can look into this issue when I complete the other task. Have you tried your experiment on a FreeBSD machine configured the same as your Ubuntu box? In other words, just plain-vanilla FreeBSD 11.2 or 12.0 without pfSense. I'm wondering if it is potentially a library issue. I have changed absolutely nothing on pfSense in that part of the Snort binary. And it used to work and then mysteriously stopped -- like what you expect if some supporting library got updated/changed and that impacted Snort.

cTar

On FreeBSD 12 in a virtual machine I was able to run the Snort -Tv -c snort.conf command and after chasing down rule errors the command completed with a successful import of the attribute table.

Could this be something to do with how php writes to the config?

I did find the following in the Snort manual which gave me pause:

"config max_attribute_hosts: <hosts>

Sets a limit on the maximum number of hosts to read from the attribute table. Minimum value is 32 and the maximum is 524288 (512k). The default is 10000. If the number of hosts in the attribute table exceeds this value, an error is logged and the remainder of the hosts are ignored. This option is only supported with a Host Attribute Table"

This implies that if you use config max_attribute_hosts that a MINIMUM of 32 will be necessary.
Is this the problem since there is a max hosts setting in the pfSense gui?

bmeeks

For your first question, I think the answer is "quite possibly". That will be my first avenue of investigation and why I asked you to try it on vanilla FreeBSD installation.

As for the "config max_attribute_hosts" question, I think if that were the issue the error message would be more specific. I will look into this, though, when I work on this issue. I have it logged in my private "Open Bugs" list.

Feel free to also open a pfSense Redmine request if you would like. That will create a public tracker for the issue.

cTar

I just tried config max_attribute_hosts: 100 added to the Ubuntu installation and there was no error with less than 32 hosts. I will open that request. Thanks for the help
Bill

bmeeks

I have been troubleshooting this in debug mode for nearly a full day and still am coming up empty-handed in terms of finding the problem. The XML file is correct, but the parser within Snort thinks something is wrong.

Debugging is darn near impossible because the actual XML file parsing is done via a nested set of flex/yacc scripts that are used during compile time to produce C source and header files that then get compiled into the Snort executable. I can only trace the function execution a few steps and then lose it within all the unintentional obfuscation created by the nested flex/yacc scripts.

It keeps failing with the error message "... check the grammar around line 0 (<tag SNORT_ATTRIBUTES>) ..." and then gives the filename. However, the file validates just fine against the DTD file included with the Snort source code. I've searched for hidden characters within the file, tested with and without DOS line endings versus Linux line endings, and still have come up with nothing to identify the real issue.

I am going to put this bug search on pause while I work on completing the new Inline IPS mode feature. When finished with that, I will come back to this bug.

bmeeks

I'm happy to report SUCCESS in finding this problem! Turns out it is the choice to use yacc by the FreeBSD poudriere builder system instead of bison when compiling parts of the Snort binary. After some Google research, it seems bison is a newer program that implements the functionality of the older yacc program. bison is backwards compatible with yacc, but the opposite is not 100% true. The use of yacc during the pfSense Snort binary build produces some machine code that fails to properly read the host attributes XML file. When you compile Snort in a different environment, bison is most likely to be the default token parser and so Snort works when importing a host attributes XML file.

Look for this to be fixed in the upcoming release of Snort-2.9.13_1 on pfSense-2.5-DEVEL. We are forcing the Snort build on pfSense to use bison instead of defaulting to yacc. I am also going to report this issue to the FreeBSD upstream port maintainer for Snort.

cTar

That is great! Thank you for your efforts to address this. As I have a "production" system I will wait for the stable release.

Thanks again

Bill

bmeeks

@cTar said in Host Attribute Table:

That is great! Thank you for your efforts to address this. As I have a "production" system I will wait for the stable release.

Thanks again

Bill

Actually, the FreeBSD Ports maintainer incorporated my fix into the official release, so the pfSense team pulled that change into pfSense-2.4.4-RELEASE this morning. You should see an update for your Snort package in pfSense to version 3.2.9.8_6. That will install Snort binary version 2.9.12_2 which includes the Host Attribute Table fix. Test it and let me know how it works. My testing on pfSense-2.5 was successful.

cTar

I can confirm it is working on 2.4.4-RELEASE-p3 (amd64) with the latest Snort package,

Thanks again!

bmeeks

@cTar -- Good deal. Thanks for the feedback confirmation!