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Merge pull request #5947
36cba8f Alert if it is very likely we are getting a bad chain (Gavin Andresen)
2 parents e1412d3 + 36cba8f commit e9af4e6

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‎src/init.cpp‎

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@@ -39,7 +39,9 @@
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#include <boost/algorithm/string/predicate.hpp>
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#include <boost/algorithm/string/replace.hpp>
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#include <boost/bind.hpp>
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#include <boost/filesystem.hpp>
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#include <boost/function.hpp>
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#include <boost/interprocess/sync/file_lock.hpp>
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#include <boost/thread.hpp>
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#include <openssl/crypto.h>
@@ -1392,6 +1394,12 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
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StartNode(threadGroup, scheduler);
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// Monitor the chain, and alert if we get blocks much quicker or slower than expected
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int64_t nPowTargetSpacing = Params().GetConsensus().nPowTargetSpacing;
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CScheduler::Function f = boost::bind(&PartitionCheck, &IsInitialBlockDownload,
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boost::ref(cs_main), boost::cref(chainActive), nPowTargetSpacing);
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scheduler.scheduleEvery(f, nPowTargetSpacing);
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#ifdef ENABLE_WALLET
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// Generate coins in the background
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if (pwalletMain)

‎src/main.cpp‎

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@@ -28,6 +28,7 @@
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#include <boost/algorithm/string/replace.hpp>
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#include <boost/filesystem.hpp>
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#include <boost/filesystem/fstream.hpp>
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#include <boost/math/distributions/poisson.hpp>
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#include <boost/thread.hpp>
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using namespace std;
@@ -1685,6 +1686,64 @@ void ThreadScriptCheck() {
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scriptcheckqueue.Thread();
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}
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//
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// Called periodically asynchronously; alerts if it smells like
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// we're being fed a bad chain (blocks being generated much
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// too slowly or too quickly).
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//
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void PartitionCheck(bool (*initialDownloadCheck)(), CCriticalSection& cs, const CChain& chain, int64_t nPowTargetSpacing)
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{
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if (initialDownloadCheck()) return;
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static int64_t lastAlertTime = 0;
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int64_t now = GetAdjustedTime();
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if (lastAlertTime > now-60*60*24) return; // Alert at most once per day
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const int SPAN_HOURS=4;
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const int SPAN_SECONDS=SPAN_HOURS*60*60;
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int BLOCKS_EXPECTED = SPAN_SECONDS / nPowTargetSpacing;
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boost::math::poisson_distribution<double> poisson(BLOCKS_EXPECTED);
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std::string strWarning;
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int64_t startTime = GetAdjustedTime()-SPAN_SECONDS;
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LOCK(cs);
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int h = chain.Height();
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while (h > 0 && chain[h]->GetBlockTime() >= startTime)
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--h;
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int nBlocks = chain.Height()-h;
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// How likely is it to find that many by chance?
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double p = boost::math::pdf(poisson, nBlocks);
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LogPrint("partitioncheck", "%s : Found %d blocks in the last %d hours\n", __func__, nBlocks, SPAN_HOURS);
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LogPrint("partitioncheck", "%s : likelihood: %g\n", __func__, p);
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// Aim for one false-positive about every fifty years of normal running:
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const int FIFTY_YEARS = 50*365*24*60*60;
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double alertThreshold = 1.0 / (FIFTY_YEARS / SPAN_SECONDS);
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if (p <= alertThreshold && nBlocks < BLOCKS_EXPECTED)
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{
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// Many fewer blocks than expected: alert!
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strWarning = strprintf(_("WARNING: check your network connection, %d blocks received in the last %d hours (%d expected)"),
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nBlocks, SPAN_HOURS, BLOCKS_EXPECTED);
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}
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else if (p <= alertThreshold && nBlocks > BLOCKS_EXPECTED)
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{
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// Many more blocks than expected: alert!
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strWarning = strprintf(_("WARNING: abnormally high number of blocks generated, %d blocks received in the last %d hours (%d expected)"),
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nBlocks, SPAN_HOURS, BLOCKS_EXPECTED);
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}
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if (!strWarning.empty())
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{
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strMiscWarning = strWarning;
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CAlert::Notify(strWarning, true);
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lastAlertTime = now;
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}
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}
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static int64_t nTimeVerify = 0;
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static int64_t nTimeConnect = 0;
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static int64_t nTimeIndex = 0;

‎src/main.h‎

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@@ -194,6 +194,8 @@ bool ProcessMessages(CNode* pfrom);
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bool SendMessages(CNode* pto, bool fSendTrickle);
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/** Run an instance of the script checking thread */
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void ThreadScriptCheck();
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/** Try to detect Partition (network isolation) attacks against us */
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void PartitionCheck(bool (*initialDownloadCheck)(), CCriticalSection& cs, const CChain& chain, int64_t nPowTargetSpacing);
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/** Check whether we are doing an initial block download (synchronizing from disk or network) */
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bool IsInitialBlockDownload();
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/** Format a string that describes several potential problems detected by the core */

‎src/test/alert_tests.cpp‎

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//
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#include "alert.h"
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#include "chain.h"
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#include "chainparams.h"
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#include "clientversion.h"
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#include "data/alertTests.raw.h"
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#include "chainparams.h"
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#include "main.h"
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#include "serialize.h"
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#include "streams.h"
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#include "util.h"
@@ -193,4 +196,65 @@ BOOST_AUTO_TEST_CASE(AlertNotify)
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SetMockTime(0);
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}
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static bool falseFunc() { return false; }
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BOOST_AUTO_TEST_CASE(PartitionAlert)
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{
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// Test PartitionCheck
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CCriticalSection csDummy;
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CChain chainDummy;
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CBlockIndex indexDummy[100];
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CChainParams& params = Params(CBaseChainParams::MAIN);
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int64_t nPowTargetSpacing = params.GetConsensus().nPowTargetSpacing;
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// Generate fake blockchain timestamps relative to
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// an arbitrary time:
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int64_t now = 1427379054;
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SetMockTime(now);
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for (int i = 0; i < 100; i++)
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{
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indexDummy[i].phashBlock = NULL;
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if (i == 0) indexDummy[i].pprev = NULL;
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else indexDummy[i].pprev = &indexDummy[i-1];
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indexDummy[i].nHeight = i;
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indexDummy[i].nTime = now - (100-i)*nPowTargetSpacing;
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// Other members don't matter, the partition check code doesn't
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// use them
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}
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chainDummy.SetTip(&indexDummy[99]);
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// Test 1: chain with blocks every nPowTargetSpacing seconds,
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// as normal, no worries:
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PartitionCheck(falseFunc, csDummy, chainDummy, nPowTargetSpacing);
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BOOST_CHECK(strMiscWarning.empty());
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// Test 2: go 3.5 hours without a block, expect a warning:
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now += 3*60*60+30*60;
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SetMockTime(now);
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PartitionCheck(falseFunc, csDummy, chainDummy, nPowTargetSpacing);
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BOOST_CHECK(!strMiscWarning.empty());
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BOOST_TEST_MESSAGE(std::string("Got alert text: ")+strMiscWarning);
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strMiscWarning = "";
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// Test 3: test the "partition alerts only go off once per day"
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// code:
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now += 60*10;
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SetMockTime(now);
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PartitionCheck(falseFunc, csDummy, chainDummy, nPowTargetSpacing);
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BOOST_CHECK(strMiscWarning.empty());
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// Test 4: get 2.5 times as many blocks as expected:
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now += 60*60*24; // Pretend it is a day later
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SetMockTime(now);
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int64_t quickSpacing = nPowTargetSpacing*2/5;
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for (int i = 0; i < 100; i++) // Tweak chain timestamps:
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indexDummy[i].nTime = now - (100-i)*quickSpacing;
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PartitionCheck(falseFunc, csDummy, chainDummy, nPowTargetSpacing);
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BOOST_CHECK(!strMiscWarning.empty());
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BOOST_TEST_MESSAGE(std::string("Got alert text: ")+strMiscWarning);
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strMiscWarning = "";
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SetMockTime(0);
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}
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BOOST_AUTO_TEST_SUITE_END()

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