{"record":{"id":"31b3aa97d29db038","repo":"hyperledger/fabric","slug":"failed-getting-channel-id-from-block-with-id-d","errorCode":null,"errorMessage":"Failed getting channel id from block with id [%d] on channel [%s]: [%s]","messagePattern":"Failed getting channel id from block with id \\[(.+?)\\] on channel \\[(.+?)\\]: \\[(.+?)\\]","errorType":"error_code","errorClass":null,"httpStatus":null,"severity":"error","filePath":"internal/peer/gossip/mcs.go","lineNumber":141,"sourceCode":"}\n\n// VerifyBlock returns nil if the block is properly signed, and the claimed seqNum is the\n// sequence number that the block's header contains.\n// else returns error\nfunc (s *MSPMessageCryptoService) VerifyBlock(chainID common.ChannelID, seqNum uint64, block *pcommon.Block) error {\n\tif block.Header == nil {\n\t\treturn fmt.Errorf(\"Invalid Block on channel [%s]. Header must be different from nil.\", chainID)\n\t}\n\n\tblockSeqNum := block.Header.Number\n\tif seqNum != blockSeqNum {\n\t\treturn fmt.Errorf(\"Claimed seqNum is [%d] but actual seqNum inside block is [%d]\", seqNum, blockSeqNum)\n\t}\n\n\t// - Extract channelID and compare with chainID\n\tchannelID, err := protoutil.GetChannelIDFromBlock(block)\n\tif err != nil {\n\t\treturn fmt.Errorf(\"Failed getting channel id from block with id [%d] on channel [%s]: [%s]\", block.Header.Number, chainID, err)\n\t}\n\n\tif channelID != string(chainID) {\n\t\treturn fmt.Errorf(\"Invalid block's channel id. Expected [%s]. Given [%s]\", chainID, channelID)\n\t}\n\n\t// - Unmarshal medatada\n\tif block.Metadata == nil || len(block.Metadata.Metadata) == 0 {\n\t\treturn fmt.Errorf(\"Block with id [%d] on channel [%s] does not have metadata. Block not valid.\", block.Header.Number, chainID)\n\t}\n\n\tdataHash, err := protoutil.BlockDataHash(block.Data)\n\tif err != nil {\n\t\treturn err\n\t}\n\t// - Verify that Header.DataHash is equal to the hash of block.Data\n\t// This is to ensure that the header is consistent with the data carried by this block\n\tif !bytes.Equal(dataHash, block.Header.DataHash) {","sourceCodeStart":123,"sourceCodeEnd":159,"githubUrl":"https://github.com/hyperledger/fabric/blob/2736b63f8fd5932511d56fe68b7039d15977f7f6/internal/peer/gossip/mcs.go#L123-L159","documentation":"After extracting the channel ID embedded in the block (via protoutil.GetChannelIDFromBlock), VerifyBlock compares it to the channel the message was received on. A mismatch means a block from one channel is being presented on another — invalid for gossip security. Note this branch runs only when GetChannelIDFromBlock succeeded.","triggerScenarios":"VerifyBlock called with chainID X but the block's metadata/header encodes channel Y — cross-channel block delivery or caller passing the wrong channel identifier.","commonSituations":"Bugs in gossip message routing after joining multiple channels; tests reusing a block from another channel; caller building ChannelID from wrong config value.","solutions":["Confirm the block was received on the correct channel — inspect gossip state for cross-channel leakage","Verify the caller passes the correct common.ChannelID matching the block","Re-join/sync the peer on the intended channel to get correct blocks"],"exampleFix":"// before\nerr := svc.VerifyBlock(common.ChannelID(\"channelB\"), seq, blockFromChannelA)\n// after\nerr := svc.VerifyBlock(common.ChannelID(\"channelA\"), seq, blockFromChannelA)","handlingStrategy":"validation","validationCode":"func blockChannel(b *pcommon.Block) (string, error) {\n    if b == nil || b.Header == nil {\n        return \"\", errors.New(\"block or header nil\")\n    }\n    ch, err := protoutil.GetChannelIDFromBlock(b)\n    if err != nil {\n        return \"\", err\n    }\n    return ch, nil\n}\n\n// before VerifyBlock:\n// ch, err := blockChannel(block); if err != nil || ch != string(chainID) { skip }","typeGuard":"func channelMatches(b *pcommon.Block, chainID common.ChannelID) bool {\n    ch, err := protoutil.GetChannelIDFromBlock(b)\n    return err == nil && ch == string(chainID)\n}","tryCatchPattern":"if err := cryptoService.VerifyBlock(chainID, seqNum, block); err != nil {\n    if strings.Contains(err.Error(), \"Failed getting channel id\") {\n        log.Warnf(\"unparseable block on %s: %v\", chainID, err)\n        return nil\n    }\n    return err\n}","preventionTips":["Verify the ChannelID passed to gossip handlers comes from the same channel the block arrived on","Decode blocks with configtxlator to debug channel attribution issues","In multi-channel peers, key block caches by channel ID to avoid cross-channel reuse"],"tags":["fabric","gossip","channel-mismatch"],"backgroundTag":"channel-id-mismatch","analyzedSha":"2736b63f8fd5932511d56fe68b7039d15977f7f6","analyzedAt":"2026-09-04T08:52:36.465Z","contentChangedAt":"2026-09-04T08:52:36.465Z","schemaVersion":2},"datasetVersion":"2026-09-08T10:18:20.063Z"}