Failing extracting proposal during check policy on channel [

Error message

Failing extracting proposal during check policy on channel [%s] with policy [%s]: [%s]

What it means

In CheckPolicy, the SignedProposal's ProposalBytes field is unmarshalled into a pb.Proposal via protoutil.UnmarshalProposal. If the bytes are empty, truncated, or not a valid serialized Proposal protobuf, the check policy flow aborts with this wrapped error, including the channel ID, policy name, and the underlying unmarshal error.

Source

Thrown at core/policy/policy.go:83

	if policyName == "" {
		return fmt.Errorf("Invalid policy name during check policy on channel [%s]. Name must be different from nil.", channelID)
	}

	if signedProp == nil {
		return fmt.Errorf("Invalid signed proposal during check policy on channel [%s] with policy [%s]", channelID, policyName)
	}

	// Get Policy
	policyManager := p.channelPolicyManagerGetter.Manager(channelID)
	if policyManager == nil {
		return fmt.Errorf("Failed to get policy manager for channel [%s]", channelID)
	}

	// Prepare SignedData
	proposal, err := protoutil.UnmarshalProposal(signedProp.ProposalBytes)
	if err != nil {
		return fmt.Errorf("Failing extracting proposal during check policy on channel [%s] with policy [%s]: [%s]", channelID, policyName, err)
	}

	header, err := protoutil.UnmarshalHeader(proposal.Header)
	if err != nil {
		return fmt.Errorf("Failing extracting header during check policy on channel [%s] with policy [%s]: [%s]", channelID, policyName, err)
	}

	shdr, err := protoutil.UnmarshalSignatureHeader(header.SignatureHeader)
	if err != nil {
		return fmt.Errorf("Invalid Proposal's SignatureHeader during check policy on channel [%s] with policy [%s]: [%s]", channelID, policyName, err)
	}

	sd := []*protoutil.SignedData{{
		Data:      signedProp.ProposalBytes,
		Identity:  shdr.Creator,
		Signature: signedProp.Signature,
	}}

View on GitHub (pinned to 2736b63f8f)

Solutions

Rebuild the SignedProposal using the official SDK proposal creation API so ProposalBytes is a correctly serialized pb.Proposal
Inspect the wrapped err in the message to identify whether bytes are empty or malformed
Check that no intermediary (proxy, chaincode handler) truncates or re-encodes ProposalBytes
Verify the client SDK and peer protobuf versions are compatible

Example fix

// before
signedProp := &pb.SignedProposal{ ProposalBytes: rawPayloadFromClient, Signature: sig }
// after
prop, _ := protoutil.Marshal(proposal)
signedProp := &pb.SignedProposal{ ProposalBytes: prop, Signature: sig }

Defensive patterns

Strategy: try-catch

Validate before calling

// Java-style equivalent: validate ProposalBytes before invoking peer policy check
if (proposalBytes == null || proposalBytes.length == 0) {
    throw new IllegalArgumentException("ProposalBytes must be a serialized Proposal");
}

Type guard

function isValidSignedProposal(sp) {
  return sp && sp.proposal_bytes && sp.proposal_bytes.length > 0;
}

Try / catch

err := checker.CheckPolicy(policyName, signedProp)
if err != nil {
    if strings.Contains(err.Error(), "Failing extracting proposal during check policy") {
        // treat as client protocol error: reject the proposal
    }
    return err
}

Prevention

Build proposals only via SDK factories
Never mutate ProposalBytes after signing
Keep proto libraries in sync
Surface the wrapped cause in logs

When it happens

Trigger: Calling CheckPolicy (via Evaluate) with a SignedProposal whose ProposalBytes is nil/empty, corrupted in transit, or serialized by an incompatible protobuf version.

Common situations: Clients building the SignedProposal manually instead of using the SDK's proposal factory; a gateway/proxy mangling the proposal payload; protobuf/marshaling mismatches between client SDK and peer (e.g. proto3 vs legacy opaque Proposal bytes).

Understand the failure class

Background: "cannot parse invalid wire-format data", "cannot unmarshal", "failed unmarshalling": protobuf unmarshal errors explained — this error's family across 10 libraries.

Related errors

AI-assisted analysis of hyperledger/fabric@2736b63f8f (2026-09-04). Data as JSON: /api/errors/1487371caa06ebc5. Report an issue: GitHub.