[Malleability C] flow.Block

[UlyanaAndrukhiv]

Problem description

flow.Block is a heavily used data structure currently malleable. Not all fields of a block are hashed properly. Payload's hash is wrong due to how the collection guarantees ID() method is implemented.

flow-go/model/flow/payload.go

Lines 7 to 24 in edf27b0

	// Payload is the actual content of each block.
	type Payload struct {
	// Guarantees are ordered in execution order. May be empty, in which case
	// only the system chunk is executed for this block.
	Guarantees []*CollectionGuarantee
	// Seals holds block seals for ancestor blocks.
	// The oldest seal must connect to the latest seal in the fork extended by this block.
	// Seals must be internally connected, containing no seals with duplicate block IDs or heights.
	// Seals may be empty. It presents a set, i.e. there is no protocol-defined ordering.
	Seals []*Seal
	Receipts ExecutionReceiptMetaList
	Results ExecutionResultList
	// ProtocolStateID is the root hash of protocol state. Per convention, this is the resulting
	// state after applying all identity-changing operations potentially contained in the block.
	// The block payload itself is validated wrt to the protocol state committed to by its parent.
	// Thereby, we are only accepting protocol states that have been certified by a valid QC.
	ProtocolStateID Identifier
	}

flow-go/model/flow/payload.go

Lines 53 to 60 in edf27b0

	// Hash returns the root hash of the payload.
	func (p Payload) Hash() Identifier {
	collHash := MerkleRoot(GetIDs(p.Guarantees)...)
	sealHash := MerkleRoot(GetIDs(p.Seals)...)
	recHash := MerkleRoot(GetIDs(p.Receipts)...)
	resHash := MerkleRoot(GetIDs(p.Results)...)
	return ConcatSum(collHash, sealHash, recHash, resHash, p.ProtocolStateID)
	}

flow-go/model/flow/collectionGuarantee.go

Lines 7 to 20 in edf27b0

	// CollectionGuarantee is a signed hash for a collection, which is used
	// to announce collections to consensus nodes.
	type CollectionGuarantee struct {
	CollectionID Identifier // ID of the collection being guaranteed
	ReferenceBlockID Identifier // defines expiry of the collection
	ChainID ChainID // the chainID of the cluster in order to determine which cluster this guarantee belongs to
	SignerIndices []byte // encoded indices of the signers
	Signature crypto.Signature // guarantor signatures
	}
	// ID returns the fingerprint of the collection guarantee.
	func (cg *CollectionGuarantee) ID() Identifier {
	return cg.CollectionID
	}

Proposed solution

Fix collection guarantee ID() implementation

P.S.

This is actually a copy of #6722