// negotiateContract establishes a connection to a host and negotiates an
// initial file contract according to the terms of the host.
func negotiateContract(conn net.Conn, addr modules.NetAddress, fc types.FileContract, txnBuilder modules.TransactionBuilder, tpool modules.TransactionPool) (hostContract, error) {
// allow 30 seconds for negotiation
conn.SetDeadline(time.Now().Add(30 * time.Second))
// read host key
var hostPublicKey types.SiaPublicKey
if err := encoding.ReadObject(conn, &hostPublicKey, 256); err != nil {
return hostContract{}, errors.New("couldn't read host's public key: " + err.Error())
}
// create our key
ourSK, ourPK, err := crypto.GenerateKeyPair()
if err != nil {
return hostContract{}, errors.New("failed to generate keypair: " + err.Error())
}
ourPublicKey := types.SiaPublicKey{
Algorithm: types.SignatureEd25519,
Key: ourPK[:],
}
// send our public key
if err := encoding.WriteObject(conn, ourPublicKey); err != nil {
return hostContract{}, errors.New("couldn't send our public key: " + err.Error())
}
// create unlock conditions
uc := types.UnlockConditions{
PublicKeys: []types.SiaPublicKey{ourPublicKey, hostPublicKey},
SignaturesRequired: 2,
}
// add UnlockHash to file contract
fc.UnlockHash = uc.UnlockHash()
// build transaction containing fc
err = txnBuilder.FundSiacoins(fc.Payout)
if err != nil {
return hostContract{}, err
}
txnBuilder.AddFileContract(fc)
txn, parents := txnBuilder.View()
txnSet := append(parents, txn)
// calculate contract ID
fcid := txn.FileContractID(0) // TODO: is it actually 0?
// send txn
if err := encoding.WriteObject(conn, txnSet); err != nil {
return hostContract{}, errors.New("couldn't send our proposed contract: " + err.Error())
}
// read back acceptance
var response string
if err := encoding.ReadObject(conn, &response, 128); err != nil {
return hostContract{}, errors.New("couldn't read the host's response to our proposed contract: " + err.Error())
}
if response != modules.AcceptResponse {
return hostContract{}, errors.New("host rejected proposed contract: " + response)
}
// read back txn with host collateral.
var hostTxnSet []types.Transaction
if err := encoding.ReadObject(conn, &hostTxnSet, types.BlockSizeLimit); err != nil {
return hostContract{}, errors.New("couldn't read the host's updated contract: " + err.Error())
}
// check that txn is okay. For now, no collateral will be added, so the
// transaction sets should be identical.
if len(hostTxnSet) != len(txnSet) {
return hostContract{}, errors.New("host sent bad collateral transaction")
}
for i := range hostTxnSet {
if hostTxnSet[i].ID() != txnSet[i].ID() {
return hostContract{}, errors.New("host sent bad collateral transaction")
}
}
// sign the txn and resend
// NOTE: for now, we are assuming that the transaction has not changed
// since we sent it. Otherwise, the txnBuilder would have to be updated
// with whatever fields were added by the host.
signedTxnSet, err := txnBuilder.Sign(true)
if err != nil {
return hostContract{}, err
}
if err := encoding.WriteObject(conn, signedTxnSet); err != nil {
return hostContract{}, errors.New("couldn't send the contract signed by us: " + err.Error())
}
// read signed txn from host
var signedHostTxnSet []types.Transaction
if err := encoding.ReadObject(conn, &signedHostTxnSet, types.BlockSizeLimit); err != nil {
return hostContract{}, errors.New("couldn't read the contract signed by the host: " + err.Error())
}
// submit to blockchain
err = tpool.AcceptTransactionSet(signedHostTxnSet)
if err == modules.ErrDuplicateTransactionSet {
// this can happen if the renter is uploading to itself
err = nil
}
if err != nil {
return hostContract{}, err
}
// create host contract
hc := hostContract{
IP: addr,
ID: fcid,
FileContract: fc,
LastRevision: types.FileContractRevision{
ParentID: fcid,
UnlockConditions: uc,
NewRevisionNumber: fc.RevisionNumber,
NewFileSize: fc.FileSize,
NewFileMerkleRoot: fc.FileMerkleRoot,
NewWindowStart: fc.WindowStart,
NewWindowEnd: fc.WindowEnd,
NewValidProofOutputs: []types.SiacoinOutput{fc.ValidProofOutputs[0], fc.ValidProofOutputs[1]},
NewMissedProofOutputs: []types.SiacoinOutput{fc.MissedProofOutputs[0], fc.MissedProofOutputs[1]},
NewUnlockHash: fc.UnlockHash,
},
LastRevisionTxn: types.Transaction{},
SecretKey: ourSK,
}
return hc, nil
}
