// verifyRecentRevision confirms that the host and contractor agree upon the current
// state of the contract being revised.
func verifyRecentRevision(conn net.Conn, contract modules.RenterContract) error {
// send contract ID
if err := encoding.WriteObject(conn, contract.ID); err != nil {
return errors.New("couldn't send contract ID: " + err.Error())
}
// read challenge
var challenge crypto.Hash
if err := encoding.ReadObject(conn, &challenge, 32); err != nil {
return errors.New("couldn't read challenge: " + err.Error())
}
// sign and return
sig, err := crypto.SignHash(challenge, contract.SecretKey)
if err != nil {
return err
} else if err := encoding.WriteObject(conn, sig); err != nil {
return errors.New("couldn't send challenge response: " + err.Error())
}
// read acceptance
if err := modules.ReadNegotiationAcceptance(conn); err != nil {
return errors.New("host did not accept revision request: " + err.Error())
}
// read last revision and signatures
var lastRevision types.FileContractRevision
var hostSignatures []types.TransactionSignature
if err := encoding.ReadObject(conn, &lastRevision, 2048); err != nil {
return errors.New("couldn't read last revision: " + err.Error())
}
if err := encoding.ReadObject(conn, &hostSignatures, 2048); err != nil {
return errors.New("couldn't read host signatures: " + err.Error())
}
// Check that the unlock hashes match; if they do not, something is
// seriously wrong. Otherwise, check that the revision numbers match.
if lastRevision.UnlockConditions.UnlockHash() != contract.LastRevision.UnlockConditions.UnlockHash() {
return errors.New("unlock conditions do not match")
} else if lastRevision.NewRevisionNumber != contract.LastRevision.NewRevisionNumber {
return &recentRevisionError{contract.LastRevision.NewRevisionNumber, lastRevision.NewRevisionNumber}
}
// NOTE: we can fake the blockheight here because it doesn't affect
// verification; it just needs to be above the fork height and below the
// contract expiration (which was checked earlier).
return modules.VerifyFileContractRevisionTransactionSignatures(lastRevision, hostSignatures, contract.FileContract.WindowStart-1)
}
// createRevisionSignature creates a signature for a file contract revision
// that signs on the file contract revision. The renter should have already
// provided the signature. createRevisionSignature will check to make sure that
// the renter's signature is valid.
func createRevisionSignature(fcr types.FileContractRevision, renterSig types.TransactionSignature, secretKey crypto.SecretKey, blockHeight types.BlockHeight) (types.Transaction, error) {
hostSig := types.TransactionSignature{
ParentID: crypto.Hash(fcr.ParentID),
PublicKeyIndex: 1,
CoveredFields: types.CoveredFields{
FileContractRevisions: []uint64{0},
},
}
txn := types.Transaction{
FileContractRevisions: []types.FileContractRevision{fcr},
TransactionSignatures: []types.TransactionSignature{renterSig, hostSig},
}
sigHash := txn.SigHash(1)
encodedSig, err := crypto.SignHash(sigHash, secretKey)
if err != nil {
return types.Transaction{}, err
}
txn.TransactionSignatures[1].Signature = encodedSig[:]
err = modules.VerifyFileContractRevisionTransactionSignatures(fcr, txn.TransactionSignatures, blockHeight)
if err != nil {
return types.Transaction{}, err
}
return txn, nil
}