You cannot select more than 25 topics Topics must start with a letter or number, can include dashes ('-') and can be up to 35 characters long.
loop/lsat/interceptor.go

333 lines
11 KiB
Go

package lsat
import (
"context"
"encoding/base64"
"fmt"
"regexp"
"sync"
"time"
"github.com/lightninglabs/loop/lndclient"
"github.com/lightningnetwork/lnd/lnrpc/routerrpc"
"github.com/lightningnetwork/lnd/lnwire"
"github.com/lightningnetwork/lnd/macaroons"
"github.com/lightningnetwork/lnd/zpay32"
"google.golang.org/grpc"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/metadata"
"google.golang.org/grpc/status"
)
const (
// GRPCErrCode is the error code we receive from a gRPC call if the
// server expects a payment.
GRPCErrCode = codes.Internal
// GRPCErrMessage is the error message we receive from a gRPC call in
// conjunction with the GRPCErrCode to signal the client that a payment
// is required to access the service.
GRPCErrMessage = "payment required"
// AuthHeader is is the HTTP response header that contains the payment
// challenge.
AuthHeader = "WWW-Authenticate"
// MaxRoutingFee is the maximum routing fee in satoshis that we are
// going to pay to acquire an LSAT token.
// TODO(guggero): make this configurable
MaxRoutingFeeSats = 10
// PaymentTimeout is the maximum time we allow a payment to take before
// we stop waiting for it.
PaymentTimeout = 60 * time.Second
// manualRetryHint is the error text we return to tell the user how a
// token payment can be retried if the payment fails.
manualRetryHint = "consider removing pending token file if error " +
"persists. use 'listauth' command to find out token file name"
)
var (
// authHeaderRegex is the regular expression the payment challenge must
// match for us to be able to parse the macaroon and invoice.
authHeaderRegex = regexp.MustCompile(
"LSAT macaroon='(.*?)' invoice='(.*?)'",
)
)
// Interceptor is a gRPC client interceptor that can handle LSAT authentication
// challenges with embedded payment requests. It uses a connection to lnd to
// automatically pay for an authentication token.
type Interceptor struct {
lnd *lndclient.LndServices
store Store
lock sync.Mutex
}
// NewInterceptor creates a new gRPC client interceptor that uses the provided
// lnd connection to automatically acquire and pay for LSAT tokens, unless the
// indicated store already contains a usable token.
func NewInterceptor(lnd *lndclient.LndServices, store Store) *Interceptor {
return &Interceptor{
lnd: lnd,
store: store,
}
}
// UnaryInterceptor is an interceptor method that can be used directly by gRPC
// for unary calls. If the store contains a token, it is attached as credentials
// to every call before patching it through. The response error is also
// intercepted for every call. If there is an error returned and it is
// indicating a payment challenge, a token is acquired and paid for
// automatically. The original request is then repeated back to the server, now
// with the new token attached.
func (i *Interceptor) UnaryInterceptor(ctx context.Context, method string,
req, reply interface{}, cc *grpc.ClientConn, invoker grpc.UnaryInvoker,
opts ...grpc.CallOption) error {
// To avoid paying for a token twice if two parallel requests are
// happening, we require an exclusive lock here.
i.lock.Lock()
defer i.lock.Unlock()
addLsatCredentials := func(token *Token) error {
macaroon, err := token.PaidMacaroon()
if err != nil {
return err
}
opts = append(opts, grpc.PerRPCCredentials(
macaroons.NewMacaroonCredential(macaroon),
))
return nil
}
// Let's see if the store already contains a token and what state it
// might be in. If a previous call was aborted, we might have a pending
// token that needs to be handled separately.
token, err := i.store.CurrentToken()
switch {
// If there is no token yet, nothing to do at this point.
case err == ErrNoToken:
// Some other error happened that we have to surface.
case err != nil:
log.Errorf("Failed to get token from store: %v", err)
return fmt.Errorf("getting token from store failed: %v", err)
// Only if we have a paid token append it. We don't resume a pending
// payment just yet, since we don't even know if a token is required for
// this call. We also never send a pending payment to the server since
// we know it's not valid.
case !token.isPending():
if err = addLsatCredentials(token); err != nil {
log.Errorf("Adding macaroon to request failed: %v", err)
return fmt.Errorf("adding macaroon failed: %v", err)
}
}
// We need a way to extract the response headers sent by the server.
// This can only be done through the experimental grpc.Trailer call
// option. We execute the request and inspect the error. If it's the
// LSAT specific payment required error, we might execute the same
// method again later with the paid LSAT token.
trailerMetadata := &metadata.MD{}
opts = append(opts, grpc.Trailer(trailerMetadata))
err = invoker(ctx, method, req, reply, cc, opts...)
// Only handle the LSAT error message that comes in the form of
// a gRPC status error.
if isPaymentRequired(err) {
paidToken, err := i.handlePayment(ctx, token, trailerMetadata)
if err != nil {
return err
}
if err = addLsatCredentials(paidToken); err != nil {
log.Errorf("Adding macaroon to request failed: %v", err)
return fmt.Errorf("adding macaroon failed: %v", err)
}
// Execute the same request again, now with the LSAT
// token added as an RPC credential.
return invoker(ctx, method, req, reply, cc, opts...)
}
return err
}
// handlePayment tries to obtain a valid token by either tracking the payment
// status of a pending token or paying for a new one.
func (i *Interceptor) handlePayment(ctx context.Context, token *Token,
md *metadata.MD) (*Token, error) {
switch {
// Resume/track a pending payment if it was interrupted for some reason.
case token != nil && token.isPending():
log.Infof("Payment of LSAT token is required, resuming/" +
"tracking previous payment from pending LSAT token")
err := i.trackPayment(ctx, token)
if err != nil {
return nil, err
}
return token, nil
// We don't have a token yet, try to get a new one.
case token == nil:
// We don't have a token yet, get a new one.
log.Infof("Payment of LSAT token is required, paying invoice")
return i.payLsatToken(ctx, md)
// We have a token and it's valid, nothing more to do here.
default:
log.Debugf("Found valid LSAT token to add to request")
return token, nil
}
}
// payLsatToken reads the payment challenge from the response metadata and tries
// to pay the invoice encoded in them, returning a paid LSAT token if
// successful.
func (i *Interceptor) payLsatToken(ctx context.Context, md *metadata.MD) (
*Token, error) {
// First parse the authentication header that was stored in the
// metadata.
authHeader := md.Get(AuthHeader)
if len(authHeader) == 0 {
return nil, fmt.Errorf("auth header not found in response")
}
matches := authHeaderRegex.FindStringSubmatch(authHeader[0])
if len(matches) != 3 {
return nil, fmt.Errorf("invalid auth header "+
"format: %s", authHeader[0])
}
// Decode the base64 macaroon and the invoice so we can store the
// information in our store later.
macBase64, invoiceStr := matches[1], matches[2]
macBytes, err := base64.StdEncoding.DecodeString(macBase64)
if err != nil {
return nil, fmt.Errorf("base64 decode of macaroon failed: "+
"%v", err)
}
invoice, err := zpay32.Decode(invoiceStr, i.lnd.ChainParams)
if err != nil {
return nil, fmt.Errorf("unable to decode invoice: %v", err)
}
// Create and store the pending token so we can resume the payment in
// case the payment is interrupted somehow.
token, err := tokenFromChallenge(macBytes, invoice.PaymentHash)
if err != nil {
return nil, fmt.Errorf("unable to create token: %v", err)
}
err = i.store.StoreToken(token)
if err != nil {
return nil, fmt.Errorf("unable to store pending token: %v", err)
}
// Pay invoice now and wait for the result to arrive or the main context
// being canceled.
payCtx, cancel := context.WithTimeout(ctx, PaymentTimeout)
defer cancel()
respChan := i.lnd.Client.PayInvoice(
payCtx, invoiceStr, MaxRoutingFeeSats, nil,
)
select {
case result := <-respChan:
if result.Err != nil {
return nil, result.Err
}
token.Preimage = result.Preimage
token.AmountPaid = lnwire.NewMSatFromSatoshis(result.PaidAmt)
token.RoutingFeePaid = lnwire.NewMSatFromSatoshis(
result.PaidFee,
)
return token, i.store.StoreToken(token)
case <-payCtx.Done():
return nil, fmt.Errorf("payment timed out. try again to track "+
"payment. %s", manualRetryHint)
case <-ctx.Done():
return nil, fmt.Errorf("parent context canceled. try again to"+
"track payment. %s", manualRetryHint)
}
}
// trackPayment tries to resume a pending payment by tracking its state and
// waiting for a conclusive result.
func (i *Interceptor) trackPayment(ctx context.Context, token *Token) error {
// Lookup state of the payment.
paymentStateCtx, cancel := context.WithCancel(ctx)
defer cancel()
payStatusChan, payErrChan, err := i.lnd.Router.TrackPayment(
paymentStateCtx, token.PaymentHash,
)
if err != nil {
log.Errorf("Could not call TrackPayment on lnd: %v", err)
return fmt.Errorf("track payment call to lnd failed: %v", err)
}
// We can't wait forever, so we give the payment tracking the same
// timeout as the original payment.
payCtx, cancel := context.WithTimeout(ctx, PaymentTimeout)
defer cancel()
// We'll consume status updates until we reach a conclusive state or
// reach the timeout.
for {
select {
// If we receive a state without an error, the payment has been
// initiated. Loop until the payment
case result := <-payStatusChan:
switch result.State {
// If the payment was successful, we have all the
// information we need and we can return the fully paid
// token.
case routerrpc.PaymentState_SUCCEEDED:
extractPaymentDetails(token, result)
return i.store.StoreToken(token)
// The payment is still in transit, we'll give it more
// time to complete.
case routerrpc.PaymentState_IN_FLIGHT:
// Any other state means either error or timeout.
default:
return fmt.Errorf("payment tracking failed "+
"with state %s. %s",
result.State.String(), manualRetryHint)
}
// Abort the payment execution for any error.
case err := <-payErrChan:
return fmt.Errorf("payment tracking failed: %v. %s",
err, manualRetryHint)
case <-payCtx.Done():
return fmt.Errorf("payment tracking timed out. %s",
manualRetryHint)
}
}
}
// isPaymentRequired inspects an error to find out if it's the specific gRPC
// error returned by the server to indicate a payment is required to access the
// service.
func isPaymentRequired(err error) bool {
statusErr, ok := status.FromError(err)
return ok &&
statusErr.Message() == GRPCErrMessage &&
statusErr.Code() == GRPCErrCode
}
// extractPaymentDetails extracts the preimage and amounts paid for a payment
// from the payment status and stores them in the token.
func extractPaymentDetails(token *Token, status lndclient.PaymentStatus) {
token.Preimage = status.Preimage
total := status.Route.TotalAmount
fees := status.Route.TotalFees()
token.AmountPaid = total - fees
token.RoutingFeePaid = fees
}