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Alert system DoS prevention

This fixes two alert system vulnerabilities found by
Sergio Lerner; you could send peers unlimited numbers
of invalid alert message to try to either fill up their
debug.log with messages and/or keep their CPU busy
checking signatures.

Fixed by disconnecting/banning peers if they send 10 or more
bad (invalid/expired/cancelled) alerts.
0.8
Gavin Andresen 12 years ago
parent
commit
d5a52d9b3e
  1. 25
      src/main.cpp
  2. 2
      src/main.h

25
src/main.cpp

@ -2997,14 +2997,27 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv) @@ -2997,14 +2997,27 @@ bool static ProcessMessage(CNode* pfrom, string strCommand, CDataStream& vRecv)
CAlert alert;
vRecv >> alert;
if (alert.ProcessAlert())
uint256 alertHash = alert.GetHash();
if (pfrom->setKnown.count(alertHash) == 0)
{
// Relay
pfrom->setKnown.insert(alert.GetHash());
if (alert.ProcessAlert())
{
LOCK(cs_vNodes);
BOOST_FOREACH(CNode* pnode, vNodes)
alert.RelayTo(pnode);
// Relay
pfrom->setKnown.insert(alertHash);
{
LOCK(cs_vNodes);
BOOST_FOREACH(CNode* pnode, vNodes)
alert.RelayTo(pnode);
}
}
else {
// Small DoS penalty so peers that send us lots of
// duplicate/expired/invalid-signature/whatever alerts
// eventually get banned.
// This isn't a Misbehaving(100) (immediate ban) because the
// peer might be an older or different implementation with
// a different signature key, etc.
pfrom->Misbehaving(10);
}
}
}

2
src/main.h

@ -1535,7 +1535,7 @@ public: @@ -1535,7 +1535,7 @@ public:
uint256 GetHash() const
{
return SerializeHash(*this);
return Hash(this->vchMsg.begin(), this->vchMsg.end());
}
bool IsInEffect() const

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