lnd.xprv/macaroons/service.go

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package macaroons
import (
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"context"
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"encoding/hex"
"fmt"
"os"
"path"
"github.com/lightningnetwork/lnd/channeldb/kvdb"
"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"
)
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"
// ErrMissingRootKeyID specifies the root key ID is missing.
ErrMissingRootKeyID = fmt.Errorf("missing root key ID")
// ErrDeletionForbidden is used when attempting to delete the
// DefaultRootKeyID or the encryptedKeyID.
ErrDeletionForbidden = fmt.Errorf("the specified ID cannot be deleted")
// PermissionEntityCustomURI is a special entity name for a permission
// that does not describe an entity:action pair but instead specifies a
// specific URI that needs to be granted access to. This can be used for
// more fine-grained permissions where a macaroon only grants access to
// certain methods instead of a whole list of methods that define the
// same entity:action pairs. For example: uri:/lnrpc.Lightning/GetInfo
// only gives access to the GetInfo call.
PermissionEntityCustomURI = "uri"
)
// MacaroonValidator is an interface type that can check if macaroons are valid.
type MacaroonValidator interface {
// ValidateMacaroon extracts the macaroon from the context's gRPC
// metadata, checks its signature, makes sure all specified permissions
// for the called method are contained within and finally ensures all
// caveat conditions are met. A non-nil error is returned if any of the
// checks fail.
ValidateMacaroon(ctx context.Context,
requiredPermissions []bakery.Op, fullMethod string) error
}
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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
// externalValidators is a map between an absolute gRPC URIs and the
// corresponding external macaroon validator to be used for that URI.
// If no external validator for an URI is specified, the service will
// use the internal validator.
externalValidators map[string]MacaroonValidator
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}
// 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.
func NewService(dir, location 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 := kvdb.Create(
kvdb.BoltBackendName, path.Join(dir, DBFilename), true,
)
if err != nil {
return nil, err
}
rootKeyStore, err := NewRootKeyStorage(macaroonDB)
if err != nil {
return nil, err
}
macaroonParams := bakery.BakeryParams{
Location: location,
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)
}
}
return &Service{
Bakery: *svc,
rks: rootKeyStore,
externalValidators: make(map[string]MacaroonValidator),
}, 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
}
// RegisterExternalValidator registers a custom, external macaroon validator for
// the specified absolute gRPC URI. That validator is then fully responsible to
// make sure any macaroon passed for a request to that URI is valid and
// satisfies all conditions.
func (svc *Service) RegisterExternalValidator(fullMethod string,
validator MacaroonValidator) error {
if validator == nil {
return fmt.Errorf("validator cannot be nil")
}
_, ok := svc.externalValidators[fullMethod]
if ok {
return fmt.Errorf("external validator for method %s already "+
"registered", fullMethod)
}
svc.externalValidators[fullMethod] = validator
return nil
}
// 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) {
uriPermissions, ok := permissionMap[info.FullMethod]
if !ok {
return nil, fmt.Errorf("%s: unknown permissions "+
"required for method", info.FullMethod)
}
// Find out if there is an external validator registered for
// this method. Fall back to the internal one if there isn't.
validator, ok := svc.externalValidators[info.FullMethod]
if !ok {
validator = svc
}
// Now that we know what validator to use, let it do its work.
err := validator.ValidateMacaroon(
ctx, uriPermissions, 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 {
uriPermissions, ok := permissionMap[info.FullMethod]
if !ok {
return fmt.Errorf("%s: unknown permissions required "+
"for method", info.FullMethod)
}
// Find out if there is an external validator registered for
// this method. Fall back to the internal one if there isn't.
validator, ok := svc.externalValidators[info.FullMethod]
if !ok {
validator = svc
}
// Now that we know what validator to use, let it do its work.
err := validator.ValidateMacaroon(
ss.Context(), uriPermissions, 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, fullMethod string) error {
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// 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...)
// If the macaroon contains broad permissions and checks out, we're
// done.
if err == nil {
return nil
}
// To also allow the special permission of "uri:<FullMethod>" to be a
// valid permission, we need to check it manually in case there is no
// broader scope permission defined.
_, err = authChecker.Allow(ctx, bakery.Op{
Entity: PermissionEntityCustomURI,
Action: fullMethod,
})
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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)
}
// NewMacaroon wraps around the function Oven.NewMacaroon with the defaults,
// - version is always bakery.LatestVersion;
// - caveats is always nil.
// In addition, it takes a rootKeyID parameter, and puts it into the context.
// The context is passed through Oven.NewMacaroon(), in which calls the function
// RootKey(), that reads the context for rootKeyID.
func (svc *Service) NewMacaroon(
ctx context.Context, rootKeyID []byte,
ops ...bakery.Op) (*bakery.Macaroon, error) {
// Check rootKeyID is not called with nil or empty bytes. We want the
// caller to be aware the value of root key ID used, so we won't replace
// it with the DefaultRootKeyID if not specified.
if len(rootKeyID) == 0 {
return nil, ErrMissingRootKeyID
}
// // Pass the root key ID to context.
ctx = ContextWithRootKeyID(ctx, rootKeyID)
return svc.Oven.NewMacaroon(ctx, bakery.LatestVersion, nil, ops...)
}
// ListMacaroonIDs returns all the root key ID values except the value of
// encryptedKeyID.
func (svc *Service) ListMacaroonIDs(ctxt context.Context) ([][]byte, error) {
return svc.rks.ListMacaroonIDs(ctxt)
}
// DeleteMacaroonID removes one specific root key ID. If the root key ID is
// found and deleted, it will be returned.
func (svc *Service) DeleteMacaroonID(ctxt context.Context,
rootKeyID []byte) ([]byte, error) {
return svc.rks.DeleteMacaroonID(ctxt, rootKeyID)
}