lnd.xprv/macaroons/service.go

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package macaroons
import (
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"encoding/hex"
"fmt"
"os"
"path"
"google.golang.org/grpc"
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"google.golang.org/grpc/metadata"
"gopkg.in/macaroon-bakery.v2/bakery"
"gopkg.in/macaroon-bakery.v2/bakery/checkers"
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macaroon "gopkg.in/macaroon.v2"
"golang.org/x/net/context"
"github.com/coreos/bbolt"
)
var (
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// DBFilename is the filename within the data directory which contains
// the macaroon stores.
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DBFilename = "macaroons.db"
)
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// Service encapsulates bakery.Bakery and adds a Close() method that zeroes the
// root key service encryption keys, as well as utility methods to validate a
// macaroon against the bakery and gRPC middleware for macaroon-based auth.
type Service struct {
bakery.Bakery
rks *RootKeyStorage
}
// NewService returns a service backed by the macaroon Bolt DB stored in the
// passed directory. The `checks` argument can be any of the `Checker` type
// functions defined in this package, or a custom checker if desired. This
// constructor prevents double-registration of checkers to prevent panics, so
// listing the same checker more than once is not harmful. Default checkers,
// such as those for `allow`, `time-before`, `declared`, and `error` caveats
// are registered automatically and don't need to be added.
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func NewService(dir string, checks ...Checker) (*Service, error) {
// Ensure that the path to the directory exists.
if _, err := os.Stat(dir); os.IsNotExist(err) {
if err := os.MkdirAll(dir, 0700); err != nil {
return nil, err
}
}
// Open the database that we'll use to store the primary macaroon key,
// and all generated macaroons+caveats.
macaroonDB, err := bolt.Open(
path.Join(dir, DBFilename), 0600, bolt.DefaultOptions,
)
if err != nil {
return nil, err
}
rootKeyStore, err := NewRootKeyStorage(macaroonDB)
if err != nil {
return nil, err
}
macaroonParams := bakery.BakeryParams{
Location: "lnd",
RootKeyStore: rootKeyStore,
// No third-party caveat support for now.
// TODO(aakselrod): Add third-party caveat support.
Locator: nil,
Key: nil,
}
svc := bakery.New(macaroonParams)
// Register all custom caveat checkers with the bakery's checker.
// TODO(aakselrod): Add more checks as required.
checker := svc.Checker.FirstPartyCaveatChecker.(*checkers.Checker)
for _, check := range checks {
cond, fun := check()
if !isRegistered(checker, cond) {
checker.Register(cond, "std", fun)
}
}
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return &Service{*svc, rootKeyStore}, nil
}
// isRegistered checks to see if the required checker has already been
// registered in order to avoid a panic caused by double registration.
func isRegistered(c *checkers.Checker, name string) bool {
if c == nil {
return false
}
for _, info := range c.Info() {
if info.Name == name &&
info.Prefix == "" &&
info.Namespace == "std" {
return true
}
}
return false
}
// UnaryServerInterceptor is a GRPC interceptor that checks whether the
// request is authorized by the included macaroons.
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func (svc *Service) UnaryServerInterceptor(
permissionMap map[string][]bakery.Op) grpc.UnaryServerInterceptor {
return func(ctx context.Context, req interface{},
info *grpc.UnaryServerInfo,
handler grpc.UnaryHandler) (interface{}, error) {
if _, ok := permissionMap[info.FullMethod]; !ok {
return nil, fmt.Errorf("%s: unknown permissions "+
"required for method", info.FullMethod)
}
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err := svc.ValidateMacaroon(ctx, permissionMap[info.FullMethod])
if err != nil {
return nil, err
}
return handler(ctx, req)
}
}
// StreamServerInterceptor is a GRPC interceptor that checks whether the
// request is authorized by the included macaroons.
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func (svc *Service) StreamServerInterceptor(
permissionMap map[string][]bakery.Op) grpc.StreamServerInterceptor {
return func(srv interface{}, ss grpc.ServerStream,
info *grpc.StreamServerInfo, handler grpc.StreamHandler) error {
if _, ok := permissionMap[info.FullMethod]; !ok {
return fmt.Errorf("%s: unknown permissions required "+
"for method", info.FullMethod)
}
err := svc.ValidateMacaroon(
ss.Context(), permissionMap[info.FullMethod],
)
if err != nil {
return err
}
return handler(srv, ss)
}
}
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// ValidateMacaroon validates the capabilities of a given request given a
// bakery service, context, and uri. Within the passed context.Context, we
// expect a macaroon to be encoded as request metadata using the key
// "macaroon".
func (svc *Service) ValidateMacaroon(ctx context.Context,
requiredPermissions []bakery.Op) error {
// Get macaroon bytes from context and unmarshal into macaroon.
md, ok := metadata.FromIncomingContext(ctx)
if !ok {
return fmt.Errorf("unable to get metadata from context")
}
if len(md["macaroon"]) != 1 {
return fmt.Errorf("expected 1 macaroon, got %d",
len(md["macaroon"]))
}
// With the macaroon obtained, we'll now decode the hex-string
// encoding, then unmarshal it from binary into its concrete struct
// representation.
macBytes, err := hex.DecodeString(md["macaroon"][0])
if err != nil {
return err
}
mac := &macaroon.Macaroon{}
err = mac.UnmarshalBinary(macBytes)
if err != nil {
return err
}
// Check the method being called against the permitted operation and
// the expiration time and IP address and return the result.
authChecker := svc.Checker.Auth(macaroon.Slice{mac})
_, err = authChecker.Allow(ctx, requiredPermissions...)
return err
}
// Close closes the database that underlies the RootKeyStore and zeroes the
// encryption keys.
func (svc *Service) Close() error {
return svc.rks.Close()
}
// CreateUnlock calls the underlying root key store's CreateUnlock and returns
// the result.
func (svc *Service) CreateUnlock(password *[]byte) error {
return svc.rks.CreateUnlock(password)
}