[Bro-Dev] [JIRA] (BIT-1045) Review usage of InternalError when parsing network traffic

Robin Sommer (JIRA) jira at bro-tracker.atlassian.net
Fri Oct 11 11:43:28 PDT 2013

    [ https://bro-tracker.atlassian.net/browse/BIT-1045?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14211#comment-14211 ] 

Robin Sommer commented on BIT-1045:

Going through, I see number of places where I'd argue it's actually a programming/logic error that's not something that can be directly/just triggered by crafted network traffic. Examples are the RefCnt() checks in ~ConnectionTimer() and the indent_level check in ODesc. I'm inclined to leave them as they were, with the argument being that those kinds of error actually *are* best to trigger an abort. E.g, if the reference counting goes awry, pretty much all bets are off anyways, and I'd rather have Bro terminate than trying to continue. 

So I think the guideline should be avoiding internal errors that happen *directly* because of broken network input; not because of (for lack of a better term) "infrastructure problems" in other parts of Bro. (Although I'm sure as I go further, I'll find more cases where that definition is  ambiguous  as well.)

What's your opinion on cases like the above? 

What I could do is go through your diffs and adapt with the above in mind, and then we can do another iteration and see if/where we agree. 

> Review usage of InternalError when parsing network traffic
> ----------------------------------------------------------
>                 Key: BIT-1045
>                 URL: https://bro-tracker.atlassian.net/browse/BIT-1045
>             Project: Bro Issue Tracker
>          Issue Type: Task
>          Components: Bro
>    Affects Versions: git/master, 2.1
>            Reporter: Vlad Grigorescu
>            Assignee: Robin Sommer
> Creating issue for tracking purposes.
> Reporter->InternalError denotes a fatal error, and will cause Bro to stop. Calling this function when parsing network traffic creates the possibility for an attacker using a "packet of death," which could stop Bro.
> I suspect that in most cases, a weird should be generated instead, and Bro should just move on to the next packet. A quick grep shows some likely candidates for incorrect use of InternalError:
> src/Sessions.cc:		reporter->InternalError("Bad IP protocol version in DoNextInnerPacket");
> src/Sessions.cc:		reporter->InternalError("fragment block not in dictionary");
> src/Sessions.cc:		reporter->InternalError("fragment block missing");
> src/Sessions.cc:			reporter->InternalError("unknown transport protocol");
> src/Frag.cc:		reporter->InternalError("bad IP version in fragment reassembly");
> src/IP.cc:		reporter->InternalError("IPv6_HdrChain::Init with truncated IP header");
> src/IP.cc:			reporter->InternalError("IPv6_Hdr_Chain bad header %d", type);
> src/IP.h:			reporter->InternalError("bad IP version in IP_Hdr ctor");
> src/RSH.cc:		reporter->InternalError("multiple rsh client names");
> src/RSH.cc:		reporter->InternalError("multiple rsh initial client names");
> src/POP3.cc:		reporter->InternalError("command not known");
> src/Rlogin.cc:		reporter->InternalError("multiple rlogin client names");
> src/ICMP.cc:			reporter->InternalError("unexpected IP proto in ICMP analyzer: %d",
> src/ICMP.cc:		reporter->InternalError("unexpected next protocol in ICMP::DeliverPacket()");
> src/SMB.cc:		reporter->InternalError("command mismatch for ParseTransaction");
> src/HTTP.cc:		reporter->InternalError("unrecognized HTTP message event");
> src/HTTP.cc:		reporter->InternalError("HTTP ParseRequest failed");
> src/DPM.cc:		reporter->InternalError("unknown protocol");
> src/RPC.cc:		reporter->InternalError("RPC underflow");
> src/RPC.cc:			reporter->InternalError("RPC resync: skipping over data failed");
> src/RPC.cc:					reporter->InternalError("inconsistent RPC record marker extraction");

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