// managedVerifyChallengeResponse will verify that the renter's response to the
// challenge provided by the host is correct. In the process, the storage
// obligation and file contract revision will be loaded and returned.
//
// The storage obligation is returned under a storage obligation lock.
func (h *Host) managedVerifyChallengeResponse(fcid types.FileContractID, challenge crypto.Hash, challengeResponse crypto.Signature) (so storageObligation, recentRevision types.FileContractRevision, revisionSigs []types.TransactionSignature, err error) {
// Grab a lock before it is possible to perform any operations on the
// storage obligation. Defer a call to unlock in the event of an error. If
// there is no error, the storage obligation will be returned with a lock.
err = h.managedTryLockStorageObligation(fcid)
if err != nil {
err = extendErr("could not get "+fcid.String()+" lock: ", ErrorInternal(err.Error()))
return storageObligation{}, types.FileContractRevision{}, nil, err
}
defer func() {
if err != nil {
h.managedUnlockStorageObligation(fcid)
}
}()
// Fetch the storage obligation, which has the revision, which has the
// renter's public key.
h.mu.RLock()
defer h.mu.RUnlock()
err = h.db.View(func(tx *bolt.Tx) error {
so, err = getStorageObligation(tx, fcid)
return err
})
if err != nil {
err = extendErr("could not fetch "+fcid.String()+": ", ErrorInternal(err.Error()))
return storageObligation{}, types.FileContractRevision{}, nil, err
}
// Pull out the file contract revision and the revision's signatures from
// the transaction.
revisionTxn := so.RevisionTransactionSet[len(so.RevisionTransactionSet)-1]
recentRevision = revisionTxn.FileContractRevisions[0]
for _, sig := range revisionTxn.TransactionSignatures {
// Checking for just the parent id is sufficient, an over-signed file
// contract is invalid.
if sig.ParentID == crypto.Hash(fcid) {
revisionSigs = append(revisionSigs, sig)
}
}
// Verify that the challegne response matches the public key.
var renterPK crypto.PublicKey
// Sanity check - there should be two public keys.
if len(recentRevision.UnlockConditions.PublicKeys) != 2 {
// The error has to be set here so that the defered error check will
// unlock the storage obligation.
h.log.Critical("wrong public key count in file contract revision")
err = errRevisionWrongPublicKeyCount
err = extendErr("wrong public key count for "+fcid.String()+": ", ErrorInternal(err.Error()))
return storageObligation{}, types.FileContractRevision{}, nil, err
}
copy(renterPK[:], recentRevision.UnlockConditions.PublicKeys[0].Key)
err = crypto.VerifyHash(challenge, renterPK, challengeResponse)
if err != nil {
err = extendErr("bad signature from renter: ", ErrorCommunication(err.Error()))
return storageObligation{}, types.FileContractRevision{}, nil, err
}
return so, recentRevision, revisionSigs, nil
}
