Currently fastsync build block by PeekTwoBlocks，if VerifyCommit fail，It'll disconnect both block's peer (ref #2457 ) and try fetch block from other peers.
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first, second := bcR.pool.PeekTwoBlocks() |
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//bcR.Logger.Info("TrySync peeked", "first", first, "second", second) |
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if first == nil || second == nil { |
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// We need both to sync the first block. |
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continue FOR_LOOP |
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} else { |
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// Try again quickly next loop. |
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didProcessCh <- struct{}{} |
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} |
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|
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firstParts := first.MakePartSet(types.BlockPartSizeBytes) |
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firstPartsHeader := firstParts.Header() |
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firstID := types.BlockID{first.Hash(), firstPartsHeader} |
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// Finally, verify the first block using the second's commit |
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// NOTE: we can probably make this more efficient, but note that calling |
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// first.Hash() doesn't verify the tx contents, so MakePartSet() is |
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// currently necessary. |
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err := state.Validators.VerifyCommit( |
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chainID, firstID, first.Height, second.LastCommit) |
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if err != nil { |
This is inefficient, and once there is an malicious peer send two block which can pass VerifyCommit，fastsync will panic when ApplyBlock.
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// TODO: batch saves so we dont persist to disk every block |
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bcR.store.SaveBlock(first, firstParts, second.LastCommit) |
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|
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// TODO: same thing for app - but we would need a way to |
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// get the hash without persisting the state |
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var err error |
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state, err = bcR.blockExec.ApplyBlock(state, firstID, first) |
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if err != nil { |
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// TODO This is bad, are we zombie? |
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cmn.PanicQ(fmt.Sprintf("Failed to process committed block (%d:%X): %v", |
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first.Height, first.Hash(), err)) |
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} |
Was it can just PeekNextBlock，and try verify it with the latest block（for height 1， it was genesis），this could indicate which block is wrong #2489 (comment)
I have write a test case to show the condition:
Running tool: /usr/bin/go test -timeout 30s github.com/tendermint/tendermint/blockchain -run ^TestBadBlockPeer$
panic: Panicked questionably: Failed to process committed block (1:83BDC43F11F110373A4E4494A599F68895B133A3): Wrong Block.Header.ValidatorsHash. Expected 3286812CA7377B35AF3B52B51E291F6A9D721EEF, got 3D045F7BA9EA70FBF2B0C641876F0CB147923A68