From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from sog-mx-1.v43.ch3.sourceforge.com ([172.29.43.191] helo=mx.sourceforge.net) by sfs-ml-2.v29.ch3.sourceforge.com with esmtp (Exim 4.76) (envelope-from ) id 1R4ANT-0008Us-HH for bitcoin-development@lists.sourceforge.net; Thu, 15 Sep 2011 11:45:11 +0000 Received-SPF: pass (sog-mx-1.v43.ch3.sourceforge.com: domain of gmail.com designates 74.125.82.53 as permitted sender) client-ip=74.125.82.53; envelope-from=mh.in.england@gmail.com; helo=mail-ww0-f53.google.com; Received: from mail-ww0-f53.google.com ([74.125.82.53]) by sog-mx-1.v43.ch3.sourceforge.com with esmtps (TLSv1:RC4-SHA:128) (Exim 4.76) id 1R4ANS-0002uT-Bw for bitcoin-development@lists.sourceforge.net; Thu, 15 Sep 2011 11:45:11 +0000 Received: by wwg14 with SMTP id 14so3184614wwg.10 for ; Thu, 15 Sep 2011 04:45:04 -0700 (PDT) MIME-Version: 1.0 Received: by 10.216.198.12 with SMTP id u12mr983212wen.65.1316087104202; Thu, 15 Sep 2011 04:45:04 -0700 (PDT) Sender: mh.in.england@gmail.com Received: by 10.216.52.81 with HTTP; Thu, 15 Sep 2011 04:45:04 -0700 (PDT) In-Reply-To: References: Date: Thu, 15 Sep 2011 13:45:04 +0200 X-Google-Sender-Auth: OH9fwVj3rFvb-L4g7cbV4ML61yA Message-ID: From: Mike Hearn To: Gavin Andresen Content-Type: multipart/alternative; boundary=0016e6d7e6b456e74904acf968d7 X-Spam-Score: -0.5 (/) X-Spam-Report: Spam Filtering performed by mx.sourceforge.net. See http://spamassassin.org/tag/ for more details. -1.5 SPF_CHECK_PASS SPF reports sender host as permitted sender for sender-domain 0.0 FREEMAIL_FROM Sender email is commonly abused enduser mail provider (mh.in.england[at]gmail.com) -0.0 SPF_PASS SPF: sender matches SPF record 1.0 HTML_MESSAGE BODY: HTML included in message 0.1 DKIM_SIGNED Message has a DKIM or DK signature, not necessarily valid -0.1 DKIM_VALID Message has at least one valid DKIM or DK signature X-Headers-End: 1R4ANS-0002uT-Bw Cc: Bitcoin Dev Subject: Re: [Bitcoin-development] Request review: drop misbehaving peers X-BeenThere: bitcoin-development@lists.sourceforge.net X-Mailman-Version: 2.1.9 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 15 Sep 2011 11:45:11 -0000 --0016e6d7e6b456e74904acf968d7 Content-Type: text/plain; charset=UTF-8 Probabilistic disconnections could make it quite hard to debug protocol implementations and increases the risk of flaky behaviour in the wild significantly. I don't see why a simpler solution isn't better. The most likely failure mode of this is not an attack but the same as previous breakages - scaling or legitimate version skew that causes problems as the network evolves. Agree with Luke that non-standard transactions should not be considered an attack. If you stay with the scoring system I'd be tempted to have a flag (defaults to 100) that sets a minimum threshold for the badness scores and ignores any below that. Attacks based on sending transactions that aren't syntactically valid don't seem likely to me, this isn't a good way to DoS somebody because discarding them is so cheap. If it turns out later there is a problem, people under attack could flip the flag until a new version is released. The formula for the DoS score in the case of invalid signatures/merkle roots seem unnecessarily elaborate. An invalid signature should never occur and could always result in immediate disconnection. Treating a block with too many sigops as invalid means legitimate relayers might be treated as an attacker if/when the constant changes in future. I'd suggest not treating this as an attacking situation at all. Why use a mutable field with a const setter? Unit tests that rely on sleeps like this can be flaky because the OS delay isn't always precise, not to mention slow/irritating to run. It's better if tests can override the clock, eg, if GetTime() did something like if (nMockTime) { return nMockTime} else { ... } then unit tests could reliably modify and advance the clock in a fast/efficient manner. --0016e6d7e6b456e74904acf968d7 Content-Type: text/html; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Probabilistic disconnections could make it quite hard to debug protocol imp= lementations and increases the risk of flaky behaviour in the wild signific= antly. I don't see why a simpler solution isn't better.

The most likely failure mode of this is not an attack but th= e same as previous breakages - scaling or legitimate version skew that caus= es problems as the network evolves.=C2=A0

Agree wi= th Luke that non-standard transactions should not be considered an attack.<= /div>

If you stay with the scoring system I'd be tempted = to have a flag (defaults to 100) that sets a minimum threshold for the badn= ess scores and ignores any below that. Attacks based on sending transaction= s that aren't syntactically valid don't seem likely to me, this isn= 't a good way to DoS somebody because discarding them is so cheap. If i= t turns out later there is a problem, people under attack could flip the fl= ag until a new version is released.

The formula for the DoS score in the case of invalid si= gnatures/merkle roots seem unnecessarily elaborate. An invalid signature sh= ould never occur and could always result in immediate disconnection.

Treating a block with too many sigops as invalid means = legitimate relayers might be treated as an attacker if/when the constant ch= anges in future. I'd suggest not treating this as an attacking situatio= n at all.

Why use a mutable field with a const setter?
=
Unit tests that rely on sleeps like this can be flaky becaus= e the OS delay isn't always precise, not to mention slow/irritating to = run. It's better if tests can override the clock, eg, if GetTime() did = something like

=C2=A0 =C2=A0if (nMockTime) { return nMockTime} else { = ... }

then unit tests could reliably modify and ad= vance the clock in a fast/efficient manner.
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