[Oisf-users] real time alert on tcp stream and flowint
Peter Manev
petermanev at gmail.com
Sat Feb 11 20:11:23 UTC 2012
On Sat, Feb 11, 2012 at 8:27 PM, Nikolay Denev <ndenev at gmail.com> wrote:
>
> On Feb 11, 2012, at 9:14 PM, Peter Manev wrote:
>
>
>
> On Sat, Feb 11, 2012 at 7:42 PM, Nikolay Denev <ndenev at gmail.com> wrote:
>
>>
>> On Feb 11, 2012, at 7:52 PM, Peter Manev wrote:
>>
>>
>>
>> On Sat, Feb 11, 2012 at 4:31 PM, Nikolay Denev <ndenev at gmail.com> wrote:
>>
>>>
>>> On Feb 11, 2012, at 12:11 PM, Peter Manev wrote:
>>>
>>>
>>>
>>> On Fri, Feb 10, 2012 at 6:43 AM, Nikolay Denev <ndenev at gmail.com> wrote:
>>>
>>>>
>>>> On Feb 9, 2012, at 10:04 PM, Nikolay Denev wrote:
>>>>
>>>> > On Feb 9, 2012, at 10:03 PM, Nikolay Denev wrote:
>>>> >
>>>> >> Hi all,
>>>> >>
>>>> >> It's probably stupid question and I'm missing something but I don't
>>>> seem to be able
>>>> >> to generate alert immediately when for example a given string is
>>>> found inside a TCP stream.
>>>> >> When the TCP connection closes, suricata immediately prints the
>>>> alert in fast.log.
>>>> >> How can I make the alert be generated immediately when the rule
>>>> condition is matched?
>>>> >>
>>>> >> Also I don't know if its because of this I don't seem to be able to
>>>> trigger the rule to match several times on the same stream,
>>>> >> while I have the string that should fire the alert several times in
>>>> the stream.
>>>> >>
>>>> >> Here's an example :
>>>> >>
>>>> >> alert tcp $HOME_NET 6666 -> any any \
>>>> >> (msg:"got one"; content:"something"; flowint:something,notset;
>>>> flowint:something,=,1; sid:10;)
>>>> >>
>>>> >> alert tcp $HOME_NET 6666 -> any any \
>>>> >> (msg:"got five or more"; content:"something";
>>>> flowint:something,isset; flowint:something,+,1; flowint:something,>,5;
>>>> sid:11;)
>>>> >>
>>>> >> This never works, I just have the first rule fire once when the TCP
>>>> session is terminated.
>>>> >>
>>>> >>
>>>> >> P.S.: As a side note the wiki should be updated to include probably
>>>> "sid"s for the rules, as currently when I try to run the examples
>>>> >> suricata complains about duplicated rules.
>>>> >>
>>>> >> Thanks,
>>>> >>
>>>> >
>>>> > I'm running 1.2.1 RELEASE on FreeBSD-9.0-STABLE.
>>>>
>>>> This seems to work :
>>>>
>>>> alert tcp $HOME_NET 6666 -> any any \
>>>> (msg:"got one"; content:"something"; flowint:something,notset;
>>>> flowint:something,=,1; noalert; sid:10; priority: 1;)
>>>>
>>>> alert tcp $HOME_NET 6666 -> any any \
>>>> (msg:"got more"; content:"something"; flowint:something,isset;
>>>> flowint:something,+,1; noalert; sid:11; priority: 2;)
>>>>
>>>
>>>> alert tcp $HOME_NET 6666 -> any any \
>>>> (msg:"got too many"; content:"something";
>>>> flowint:something,isset; flowint:something,>,2; sid:12; priority: 3;)
>>>>
>>>>
>>>> _______________________________________________
>>>> Oisf-users mailing list
>>>> Oisf-users at openinfosecfoundation.org
>>>> http://lists.openinfosecfoundation.org/mailman/listinfo/oisf-users
>>>>
>>>
>>>
>>> Hi Nikolay,
>>> I think this is the way it is supposed to work. (last example, by you).
>>>
>>> When you take out "noalert" form sid 11 - does it fire ?
>>>
>>> And are these the only rules that are loaded in terms of flowint or you
>>> have others before that?
>>>
>>> thanks
>>>
>>>
>>>
>>> --
>>> Peter Manev
>>>
>>>
>>>
>>> Yes, It fires, the problem I have is that it doesn't fire for each
>>> occurence of "content".
>>> Is alert supposed to fire once per packet if it matches, or for each
>>> match in the stream?
>>>
>>> For example now I'm using these rules to catch if there are more than
>>> some defined amount of email addresses in a given stream :
>>>
>>>
>>> alert tcp $HOME_NET 80 -> any any \
>>> (msg:"got one email addr"; content:"|40|";
>>> pcre:"/[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,4}/i"; \
>>> flow:established,from_server; flowint:something,notset;
>>> flowint:something,=,1; sid:10; priority:3; noalert;)
>>>
>>> alert tcp $HOME_NET 80 -> any any \
>>> (msg:"got more email addrs"; content:"|40|";
>>> pcre:"/[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,4}/i"; \
>>> flow:established,from_server; flowint:something,isset;
>>> flowint:something,+,1; sid:11; priority:2; noalert;)
>>>
>>> alert tcp $HOME_NET 80 -> any any \
>>> (msg:"Got too many email addrs!"; content:"|40|";
>>> pcre:"/[a-z0-9._%+-]+@[a-z0-9.-]+\.[a-z]{2,4}/i"; \
>>> flow:established,from_server; flowint:something,isset;
>>> flowint:something,>,10; sid:12; priority:1; classtype:policy-violation;)
>>>
>>>
>>> This for example works, but would not match for a simple plain text file
>>> with 10 email adresses, I need to have maybe 40-50 or more for this to
>>> match.
>>> Maybe I'm missing something…
>>>
>> And yes, these are my only rules that I'm testing with. No other rules
>>> with or without flowint whatsoever.
>>>
>>>
>> Hi ,
>> Just so I understand you correctly - you have a text file (in the stream)
>> and in that text file you have 10 e-mail addresses and it wold not fire.
>> correct ?
>>
>>
>> thanks
>>
>>
>> --
>> Peter Manev
>>
>>
>> Exactly.
>>
>> For example if I try to fetch the file emails.txt via http which has the
>> following content :
>>
>> # cat emails.txt
>> edin at email.com
>> edin at email.com
>> edin at email.com
>> edin at email.com
>> edin at email.com
>> edin at email.com
>> edin at email.com
>> edin at email.com
>> edin at email.com
>> edin at email.com
>>
>> $ curl http://testserver/emails.txt
>> edin at email.com
>> edin at email.com
>> edin at email.com
>> edin at email.com
>> edin at email.com
>> edin at email.com
>> edin at email.com
>> edin at email.com
>> edin at email.com
>> edin at email.com
>> $
>>
>> And I also remove the "noalert" option from the rules, this is what I get
>> in fast.log :
>>
>> 02/11/2012-20:37:23.988271 [**] [1:10:0] got one email addr [**]
>> [Classification: (null)] [Priority: 3] {TCP} X.X.X.X:80 -> Y.Y.Y.Y:57923
>> 02/11/2012-20:37:23.988271 [**] [1:11:0] got more email addrs [**]
>> [Classification: (null)] [Priority: 2] {TCP} X.X.X.X:80 -> Y.Y.Y.Y:57923
>>
>>
>> If I change the third rule to fire if the flowint var is more than 1, it
>> is being triggered.
>>
>> If I insert some random data between the email addresses in the text
>> file, then I get 4 maybe 5 matches. Doesn't it have to match all 10 of them?
>>
>
> 1. What happens if you take out the PCRE expressions from all the rules ?
> 2. sid:12 - should not fire because you have >10 , and there are exactly
> 10 e-mails in the file
> 3. how big is the stream itself? i think it is below 2KB, correct?
> 4. is the PCRE matching the e-mails, under the unix shell ?
> 5. yes i think you should get more sid:11 alerts - but first lets
> investigate the above 4.
>
> thanks
>
> --
> Peter Manev
>
>
> The file with only the 10 emails is 160 bytes. Even without pcre I get the
> same result :
>
> alert tcp $HOME_NET 80 -> any any \
> (msg:"got one email addr"; content:"|40|"; \
> flow:established,from_server; flowint:something,notset;
> flowint:something,=,1; sid:10; priority:3;)
>
> alert tcp $HOME_NET 80 -> any any \
> (msg:"got more email addrs"; content:"|40|"; \
> flow:established,from_server; flowint:something,isset;
> flowint:something,+,1; sid:11; priority:2;)
>
> alert tcp $HOME_NET 80 -> any any \
> (msg:"Got too many email addrs!"; content:"|40|"; \
> flow:established,from_server; flowint:something,isset;
> flowint:something,>,9; sid:12; priority:1; classtype:policy-violation;)
>
>
> alerts I get :
>
> 02/11/2012-21:23:14.567194 [**] [1:10:0] got one email addr [**]
> [Classification: (null)] [Priority: 3] {TCP} X.X.X.X:80 -> Y.Y.Y.Y:58158
> 02/11/2012-21:23:14.567194 [**] [1:11:0] got more email addrs [**]
> [Classification: (null)] [Priority: 2] {TCP} X.X.X.X:80 -> Y.Y.Y.Y:58158
>
> If I put some '#' symbols between the emails in the file so that it gets
> about 9K big and I fetch it I get these alerts :
>
> 02/11/2012-21:25:37.755214 [**] [1:10:0] got one email addr [**]
> [Classification: (null)] [Priority: 3] {TCP} X.X.X.X:80 -> Y.Y.Y.Y:58166
> 02/11/2012-21:25:37.755214 [**] [1:11:0] got more email addrs [**]
> [Classification: (null)] [Priority: 2] {TCP} X.X.X.X:80 -> Y.Y.Y.Y:58166
> 02/11/2012-21:25:37.761077 [**] [1:11:0] got more email addrs [**]
> [Classification: (null)] [Priority: 2] {TCP} X.X.X.X:80 -> Y.Y.Y.Y:58166
> 02/11/2012-21:25:37.764451 [**] [1:11:0] got more email addrs [**]
> [Classification: (null)] [Priority: 2] {TCP} X.X.X.X:80 -> Y.Y.Y.Y:58166
>
>
Hi Nikolay,
Can you please post this as a bug - please be detailed (as you were in your
2 previous e-mails).
Personally i think here sid 11 is the problem , may be it does not
count/increment correctly....
thanks
--
Peter Manev
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