Snort mailing list archives
Re: [Snort-Devel] SNORT Detection-Plugin just call once
From: John Eure <john.eure () gmail com>
Date: Sat, 15 Feb 2014 16:50:12 -0800
For a static detection plugin, which is what I'm using, I did have to add a new rule option type in src/rule_option_types.h, and add corresponding entries in src/detection-plugins/detection_options.c, not only in the option_type_str array, but also in all 4 switch statements. In particular, the switch statement in detection_option_node_evaluate() is where your MyDetectionPlugin_ MyRuleOption_Detect() will wind up being called from. So that might be a good place to stick a debugging breakpoint, if you don't mind it being called a lot? I also had to add MyDetectionPlugin_Setup() to src/plugbase.c, and add an entry to src/plugin_enum.h. And that's all the changes I needed to make to the existing source code, aside from adding header includes and editing makefiles. John On Thu, Feb 13, 2014 at 5:45 AM, Emiliano Fausto <emiliano.fausto () gmail com>wrote:
Hi John, another question would be, is it mandatory to add into the files rule_option_types.h and detection_options.c a new variable called: RULE_OPTION_TYPE_MY_DETECTION? Because, I've taken as an example the asn1 detection plugin, and that's the only difference I could notice. When debugging snort with gdb, and setting up a breakpoint when calling to function Asn1Detect(), it's called almost for each packet as you told me. But setting a breakpoint into MyDetectionPlugin_MyRuleOption_Detect() doesn't work properly as it's not called. I thought that the necessary thing to link to my detection plugin was to: 1) Register the keyword: RegisterRuleOption("my_option_name", MyDetectionPlugin_MyRuleOption_Init()); 2) Make sure that the linking to my processing function was established: OptFpList * fpl = AddOptFuncToList(MyDetectionPlugin_MyRuleOption_Detect()); 3) Create the function MyDetectionPlugin_MyRuleOption_Detect(); which will return DETECTION_OPTION_MATCH or DETECTION_OPTION_NOT_MATCH. Do you have any key on that? Thanks in advance, Emiliano. 2014-02-13 9:38 GMT-03:00 Emiliano Fausto <emiliano.fausto () gmail com>: Hello John,thanks a lot for you quick answer. You are totally right about the way my static Detection Plugin should be called. Then as you guessed, the problem is that MyDetectionPlugin_ MyRuleOption_Init() isn't called at all. I'll start researching in that line, again... Thanks for your help! Emiliano. 2014-02-12 18:56 GMT-03:00 John Eure <john.eure () gmail com>: I've only done this a few times before, but it sounds like you might besetting something up incorrectly? My static detection plugin setup code looks something like this (please pardon the incredibly simplified pseudocode): // called once, during setup MyDetectionPlugin_Setup() { RegisterRuleOption("my_option_name", MyDetectionPlugin_MyRuleOption_Init()); } // called once per rule that uses "my_option_name", during setup MyDetectionPlugin_MyRuleOption_Init() { OptFpList * fpl = AddOptFuncToList(MyDetectionPlugin_MyRuleOption_Detect()); } // called a lot, at most once per packet per rule, during detection MyDetectionPlugin_MyRuleOption_Detect() { return DETECTION_OPTION_MATCH; } If you're not seeing multiple calls to your equivalent of "MyDetectionPlugin_MyRuleOption_Init()", then that's probably the place to start investigating. If that's not the cause, then I'm guessing you're doing something wrong when assigning values to the state associated with the rules. You need to be setting up the OptTreeNode and OptFuncList correctly, including setting otn->ds_list[plugin_type] to something associated with your rule. But that's way more complicated than I feel comfortable explaining, so my suggestion would be to pick a few simple detection plugins, and follow their logic? Good luck, John On Wed, Feb 12, 2014 at 12:26 PM, Emiliano Fausto < emiliano.fausto () gmail com> wrote:Hello there, I'm debugging with gdb a detection plugin I've developed, and there's something I am not fully understanding. I have this function (which should be called every time a packet matches one of my rules which invokes a keyword named "MyDP"): ... typedef struct _MyDPData { u_int16_t num; } MyDPData; ... int MyDPCheck(void *context, Packet *p) { LogMessage("My processing function was called\n"); MyDPData* mydata; if (!p->tcph) return DETECTION_OPTION_NOT_MATCH; mydata = (MyDPData *) context; if (mydata->num == 90) { LogMessage("it matched\n"); return DETECTION_OPTION_MATCH; } return DETECTION_OPTION_NOT_MATCH; } I'm facing 2 problems here: 1) When I'm debugging with GDB it seems that this function is being called just once. The moment it's called, is when the SNORT is parsing all the snort.conf file, and detects there's a keyword into a rule which matches: "MyDP". Then it doesn't matter how much packets validate the rest of the rule, it doesn't seems to be called (because the breakpoint over the function MyDPCheck isn't triggered any more). Note: It's strange, because my /var/log/snort/alert file is full of alerts referring to this alert being triggered, although I don't see the "it matched" message. My question is, shouldn't it be logging the message: "It matched?" each time it matches a packet calling this rule with the num==90? Snort.Conf rule -> alert tcp any any -> any any (MyDP: 90; msg: "My DP was called"; sid: 5016666; rev:1;) 2) I realized that it doesn't matter the number I put into the rule (in the previous example I just put 90), the Detection Plugin always returns "True" --> DETECTION_OPTION_MATCH. So, it doesn't make any sense to me, as it's a really simply comparison between the number stored option value and the hard-coded value 90. In this case, I'm almost sure that the alert should NOT be triggered if I put numbers different than 90 in the keyword value, right? Thanks in advance to anyone which could give me some light on this matter! Emiliano. ------------------------------------------------------------------------------ Android apps run on BlackBerry 10 Introducing the new BlackBerry 10.2.1 Runtime for Android apps. Now with support for Jelly Bean, Bluetooth, Mapview and more. Get your Android app in front of a whole new audience. Start now. http://pubads.g.doubleclick.net/gampad/clk?id=124407151&iu=/4140/ostg.clktrk _______________________________________________ Snort-devel mailing list Snort-devel () lists sourceforge net https://lists.sourceforge.net/lists/listinfo/snort-devel Archive: http://sourceforge.net/mailarchive/forum.php?forum_name=snort-devel Please visit http://blog.snort.org for the latest news about Snort!
------------------------------------------------------------------------------ Android apps run on BlackBerry 10 Introducing the new BlackBerry 10.2.1 Runtime for Android apps. Now with support for Jelly Bean, Bluetooth, Mapview and more. Get your Android app in front of a whole new audience. Start now. http://pubads.g.doubleclick.net/gampad/clk?id=124407151&iu=/4140/ostg.clktrk
_______________________________________________ Snort-devel mailing list Snort-devel () lists sourceforge net https://lists.sourceforge.net/lists/listinfo/snort-devel Archive: http://sourceforge.net/mailarchive/forum.php?forum_name=snort-devel Please visit http://blog.snort.org for the latest news about Snort!
Current thread:
- [Snort-Devel] SNORT Detection-Plugin just call once Emiliano Fausto (Feb 12)
- Re: [Snort-Devel] SNORT Detection-Plugin just call once John Eure (Feb 12)
- Re: [Snort-Devel] SNORT Detection-Plugin just call once Emiliano Fausto (Feb 13)
- Re: [Snort-Devel] SNORT Detection-Plugin just call once Emiliano Fausto (Feb 13)
- Re: [Snort-Devel] SNORT Detection-Plugin just call once John Eure (Feb 15)
- Re: [Snort-Devel] SNORT Detection-Plugin just call once Emiliano Fausto (Feb 17)
- Re: [Snort-Devel] SNORT Detection-Plugin just call once Emiliano Fausto (Feb 13)
- Re: [Snort-Devel] SNORT Detection-Plugin just call once John Eure (Feb 12)