Snort mailing list archives
Re: Help Developing Snort "Hello World" Dynamic Preprocessor
From: Ryan Jordan <ryan.jordan () sourcefire com>
Date: Wed, 18 Aug 2010 13:29:32 -0400
If your initialization function "HelloInit()" is working, make sure that it registers your detection function. Since we're using SSH as an example, here's the important part of SSH init: void SetupSSH(void) { _dpd.registerPreproc( "ssh", SSHInit ); } static void SSHInit(char *argp) { // prereq checks and config parsing... // ... _dpd.addPreproc( ProcessSSH, PRIORITY_APPLICATION, PP_SSH, PROTO_BIT__TCP ); // ... } SetupSSH() will always get called at Snort start-up. It registers the string "ssh" as a preprocessor name. SSHInit() only gets called if snort.conf contains "preprocessor ssh:". SSHInit() is responsible for parsing the preprocessor's config and registering the detection function. Once SSHInit() has been called, ProcessSSH() will be added to the list of preprocessor functions that get called on every packet. To get your preprocessor working, make sure that you're following each of these steps. I'd guess that you either left out a call to _dpd.registerPreproc(), or didn't add your preprocessor to snort.conf. -Ryan On Wed, Aug 18, 2010 at 12:51 PM, Fuat Yosanto <mbahe_suro () students ittelkom ac id> wrote:
Thanks Russ, Actually, for my works, I decided to modify Dynamic Preprocessor Example. It works so far. May be I will try fixing my dynamic preprocessor later. I'm still figuring out what's wrong with my dynamic preprocessor. So I make a simpler & similar dynamic preprocessor, that's the "Hello World". Ok, talking about "Hello World" Dynamic Preprocessor. I think the initialization function (HelloInit) is working. Since it was loaded successfully when snort starting up. May be the problem is in the process function (HelloProcess). In my opinion, when a packet passes and captured by Snort, Snort always call all process function in all registered preprocessor (including Dynamic Preprocesssor). Am I right? In this case, it looks like that Snort doesn't call process function in "Hello World" Dynamic Preprocessor. I have tried modifying process function in SSH Dynamic Preprocessor to do exactly the same algorithm with "Hello World" Dynamic Preprocessor. (except the output messages) I compiled them together, all dynamic preprocessor were loaded & registered successfully (including "Hello World", because I saw it was listed in Dynamic Plugin list after Snort Pig ASCII art). Then, when a packet came, only SSH Dynamic Preprocessor can output a messages (done by calling _dpd.logMsg()), but "Hello World" it self didn't say "Hello" at all. It means Snort doesn't call process function in "Hello World", right? Is it because I did not make any configuration in snort.conf for "Hello World" dynamic preprocessor? Because I think it is not necessary to make any configuration for this simple preprocessor. Regards, ------------- Fuat Yosanto On Mon, 16 Aug 2010 10:33:51 -0400, Russ Combs <rcombs () sourcefire com> wrote:Hi Fuat, Rolling your own dynamic preprocessor is not as easy as it could be.I'mputting a blog post together to remedy that. In the mean time, here are some pointers: * ensure the dpp is compiled with exactly same options as snort * ensure visibility is correct to get InitializePreprocessor() and LibVersion() exported * use DebugMessage() instead of _dpd.debugMsg() so file and line are set correctly * use the SNORT_DEBUG environment variable to get helpful output And be sure to add the preprocessor config to your snort.conf! Russ On Sat, Jul 31, 2010 at 2:35 AM, Fuat Yosanto < mbahe_suro () students ittelkom ac id> wrote:Hi all, Actually I have a problem when creating my own dynamic-preprocessor. (See my previous email with subject : Linking custom dynamic-preprocessor) Seems like my dynamic-preprocessor hasn't been executed by Snort(loadedsuccessfully but didn't work). I can't figure out what's wrong with it. May be something is missing. I have tried modifying Snort dynamic-preprocessor example to do same process with my dynamic-preprocessor. It works, but I can't satisfy my needs, because of its directory position, and naming problem. So to understand what are the minimum requirements to build dynamic-preprocessor, I am looking for a basic example code like "hello world" Snort dynamic-preprocessor. Here, I have created the prototype of "hello world" Snort dynamic-preprocessor. The idea is simple, it will log message when it finds any kind ofpacket.Additionally it can identify TCP, UDP, and ICMP packet. Assume that we have done any setup things to integrate this dynamic-preprocessor in Snort sources such as editing generators.h, preprocids.h, Makefile.am, re-running autotools, etc. These are the sources : Directory : src/dynamic-preprocessor/hello ======================== File name : spp_hello.c ======================== #include "preprocids.h" #include "sf_snort_packet.h" #include "sf_dynamic_preprocessor.h" #include "sf_dynamic_preproc_lib.h" #include "sf_snort_plugin_api.h" #include "sfPolicy.h" #include "sfPolicyUserData.h" #define GENERATOR_SPP_HELLO 230 extern DynamicPreprocessorData _dpd; static void HelloInit(char *); static void HelloProcess(void *, void *); void HelloSetup() { _dpd.registerPreproc("hello", HelloInit); } static void HelloInit(char *args) { _dpd.addPreproc(HelloProcess, PRIORITY_TRANSPORT, PP_HELLO, PROTO_BIT__TCP | PROTO_BIT__UDP | PROTO_BIT__ICMP); } static void HelloProcess(void *pkt, void *context) { SFSnortPacket *p = (SFSnortPacket *)pkt; if(IsTCP(p)) { _dpd.logMsg("Hello : Got TCP packet!\n"); } else if(IsUDP(p)) { _dpd.logMsg("Hello : Got UDP packet!\n"); } else if(IsICMP(p)) { _dpd.logMsg("Hello : Got ICMP packet!\n"); } else { _dpd.logMsg("Hello : Got unknown packet!\n"); } } =============================== File name : sf_preproc_info.h : =============================== #ifndef SF_PREPROC_INFO_H_ #define SF_PREPROC_INFO_H_ #define MAJOR_VERSION 1 #define MINOR_VERSION 0 #define BUILD_VERSION 1 #define PREPROC_NAME "HelloWorld_Preprocessor" #define DYNAMIC_PREPROC_SETUP HelloSetup extern void HelloSetup(); #endif So here I need a help to fix & improve them, beacuse those are stillnotworking. There should be something missing, something wrong, or something unnecessary.------------------------------------------------------------------------------The Palm PDK Hot Apps Program offers developers who use the Plug-In Development Kit to bring their C/C++ apps to Palm for a share of $1 Million in cash or HP Products. Visit us here for more details: http://p.sf.net/sfu/dev2dev-palm _______________________________________________ Snort-devel mailing list Snort-devel () lists sourceforge net https://lists.sourceforge.net/lists/listinfo/snort-devel------------------------------------------------------------------------------ This SF.net email is sponsored by Make an app they can't live without Enter the BlackBerry Developer Challenge http://p.sf.net/sfu/RIM-dev2dev _______________________________________________ Snort-devel mailing list Snort-devel () lists sourceforge net https://lists.sourceforge.net/lists/listinfo/snort-devel
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Current thread:
- Help Developing Snort "Hello World" Dynamic Preprocessor Fuat Yosanto (Jul 30)
- Re: Help Developing Snort "Hello World" Dynamic Preprocessor Russ Combs (Aug 16)
- Re: Help Developing Snort "Hello World" Dynamic Preprocessor Fuat Yosanto (Aug 18)
- Re: Help Developing Snort "Hello World" Dynamic Preprocessor Ryan Jordan (Aug 18)
- Re: Help Developing Snort "Hello World" Dynamic Preprocessor Fuat Yosanto (Aug 23)
- Re: Help Developing Snort "Hello World" Dynamic Preprocessor Fuat Yosanto (Aug 18)
- Re: Help Developing Snort "Hello World" Dynamic Preprocessor Russ Combs (Aug 16)