Merge pull request #1137 from guggero/macaroon-tests

macaroons: add unit tests and documentation

docs/macaroons.md

@@ -36,7 +36,8 @@ legitimate user.
 A macaroon is delegated by adding restrictions (called caveats) and an
 authentication code similar to a signature (technically an HMAC) to it. The
 technical method of doing this is outside the scope of this overview
-documentation, but the macaroon paper linked above describes it quite well. The
+documentation, but the [README in the macaroons package](../macaroons/README.md)
+or the macaroon paper linked above describe it in more detail. The
 user must remember several things:
 
 * Sharing a macaroon allows anyone in possession of that macaroon to use it to

lnd.go

@@ -791,8 +791,9 @@ func genCertPair(certFile, keyFile string) error {
 	return nil
 }
 
-// genMacaroons generates a pair of macaroon files; one admin-level and one
-// read-only. These can also be used to generate more granular macaroons.
+// genMacaroons generates three macaroon files; one admin-level, one
+// for invoice access and one read-only. These can also be used
+// to generate more granular macaroons.
 func genMacaroons(ctx context.Context, svc *macaroons.Service,
 	admFile, roFile, invoiceFile string) error {
 

macaroons/README.md

@@ -0,0 +1,89 @@
+# macaroons
+
+This is a more detailed, technical description of how macaroons work and how
+authentication and authorization is implemented in `lnd`.
+
+For a more high-level overview see
+[macaroons.md in the docs](../docs/macaroons.md).
+
+## Root key
+
+At startup, if the option `--no-macaroons` is **not** used, a Bolt DB key/value
+store named `data/macaroons.db` is created with a bucket named `macrootkeys`.
+In this DB the following two key/value pairs are stored:
+
+* Key `0`: the encrypted root key (32 bytes).
+  * If the root key does not exist yet, 32 bytes of pseudo-random data is
+    generated and used.
+* Key `enckey`: the parameters used to derive a secret encryption key from a
+  passphrase.
+  * The following parameters are stored: `<salt><digest><N><R><P>`
+    * `salt`: 32 byte of random data used as salt for the `scrypt` key
+      derivation.
+    * `digest`: sha256 hashed key derived from the `scrypt` operation. Is used
+      to verify if the password is correct.
+    * `N`, `P`, `R`: Parameters used for the `scrypt` operation.
+  * The root key is symmetrically encrypted with the derived secret key, using
+    the `secretbox` method of the library
+    [btcsuite/golangcrypto](https://github.com/btcsuite/golangcrypto).
+  * If the option `--noencryptwallet` is used, then the default passphrase
+    `hello` is used to encrypt the root key.
+
+## Generated macaroons
+
+With the root key set up, `lnd` continues with creating three macaroon files:
+
+* `invoice.macaroon`: Grants read and write access to all invoice related gRPC
+  commands (like generating an address or adding an invoice). Can be used for a
+  web shop application for example. Paying an invoice is not possible, even if
+  the name might suggest it. The permission `offchain` is needed to pay an
+  invoice which is currently only granted in the admin macaroon.
+* `readonly.macaroon`: Grants read-only access to all gRPC commands. Could be
+  given to  a monitoring application for example.
+* `admin.macaroon`: Grants full read and write access to all gRPC commands.
+  This is used by the `lncli` client.
+
+These three macaroons all have the location field set to `lnd` and have no
+conditions/first party caveats or third party caveats set.
+
+The access restrictions are implemented with a list of entity/action pairs that
+is mapped to the gRPC functions by the `rpcserver.go`. 
+For example, the permissions for the `invoice.macaroon` looks like this:
+
+```go
+	// invoicePermissions is a slice of all the entities that allows a user
+	// to only access calls that are related to invoices, so: streaming
+	// RPCs, generating, and listening invoices.
+	invoicePermissions = []bakery.Op{
+		{
+			Entity: "invoices",
+			Action: "read",
+		},
+		{
+			Entity: "invoices",
+			Action: "write",
+		},
+		{
+			Entity: "address",
+			Action: "read",
+		},
+		{
+			Entity: "address",
+			Action: "write",
+		},
+	}
+```
+
+## Constraints / First party caveats
+
+There are currently two constraints implemented that can be used by `lncli` to
+restrict the macaroon it uses to communicate with the gRPC interface. These can
+be found in `constraints.go`:
+
+* `TimeoutConstraint`: Set a timeout in seconds after which the macaroon is no
+  longer valid.
+  This constraint can be set by adding the parameter `--macaroontimeout xy` to
+  the `lncli` command.
+* `IPLockConstraint`: Locks the macaroon to a specific IP address.
+  This constraint can be set by adding the parameter `--macaroonip a.b.c.d` to
+  the `lncli` command.

macaroons/constraints_test.go

@@ -0,0 +1,108 @@
+package macaroons_test
+
+import (
+	"testing"
+	"github.com/lightningnetwork/lnd/macaroons"
+	"gopkg.in/macaroon.v2"
+	"time"
+	"strings"
+)
+
+var (
+	testRootKey                 = []byte("dummyRootKey")
+	testId                      = []byte("dummyId")
+	testLocation                = "lnd"
+	testVersion                 = macaroon.LatestVersion
+	expectedTimeCaveatSubstring = "time-before " + string(time.Now().Year())
+)
+
+func createDummyMacaroon(t *testing.T) *macaroon.Macaroon {
+	dummyMacaroon, err := macaroon.New(testRootKey, testId,
+		testLocation, testVersion)
+	if err != nil {
+		t.Fatalf("Error creating initial macaroon: %v", err)
+	}
+	return dummyMacaroon
+}
+
+// TestAddConstraints tests that constraints can be added to an existing
+// macaroon and therefore tighten its restrictions.
+func TestAddConstraints(t *testing.T) {
+	// We need a dummy macaroon to start with. Create one without
+	// a bakery, because we mock everything anyway.
+	initialMac := createDummyMacaroon(t)
+
+	// Now add a constraint and make sure we have a cloned macaroon
+	// with the constraint applied instead of a mutated initial one.
+	newMac, err := macaroons.AddConstraints(initialMac,
+		macaroons.TimeoutConstraint(1))
+	if err != nil {
+		t.Fatalf("Error adding constraint: %v", err)
+	}
+	if &newMac == &initialMac {
+		t.Fatalf("Initial macaroon has been changed, something " +
+			"went wrong!")
+	}
+
+	// Finally, test that the constraint has been added.
+	if len(initialMac.Caveats()) == len(newMac.Caveats()) {
+		t.Fatalf("No caveat has been added to the macaroon when " +
+			"constraint was applied")
+	}
+}
+
+// TestTimeoutConstraint tests that a caveat for the lifetime of
+// a macaroon is created.
+func TestTimeoutConstraint(t *testing.T) {
+	// Get a configured version of the constraint function.
+	constraintFunc := macaroons.TimeoutConstraint(3)
+
+	// Now we need a dummy macaroon that we can apply the constraint
+	// function to.
+	testMacaroon := createDummyMacaroon(t)
+	err := constraintFunc(testMacaroon)
+	if err != nil {
+		t.Fatalf("Error applying timeout constraint: %v", err)
+	}
+
+	// Finally, check that the created caveat has an
+	// acceptable value
+	if strings.HasPrefix(string(testMacaroon.Caveats()[0].Id),
+		expectedTimeCaveatSubstring) {
+		t.Fatalf("Added caveat '%s' does not meet the expectations!",
+			testMacaroon.Caveats()[0].Id)
+	}
+}
+
+// TestTimeoutConstraint tests that a caveat for the lifetime of
+// a macaroon is created.
+func TestIpLockConstraint(t *testing.T) {
+	// Get a configured version of the constraint function.
+	constraintFunc := macaroons.IPLockConstraint("127.0.0.1")
+
+	// Now we need a dummy macaroon that we can apply the constraint
+	// function to.
+	testMacaroon := createDummyMacaroon(t)
+	err := constraintFunc(testMacaroon)
+	if err != nil {
+		t.Fatalf("Error applying timeout constraint: %v", err)
+	}
+
+	// Finally, check that the created caveat has an
+	// acceptable value
+	if string(testMacaroon.Caveats()[0].Id) != "ipaddr 127.0.0.1" {
+		t.Fatalf("Added caveat '%s' does not meet the expectations!",
+			testMacaroon.Caveats()[0].Id)
+	}
+}
+
+// TestIPLockBadIP tests that an IP constraint cannot be added if the
+// provided string is not a valid IP address.
+func TestIPLockBadIP(t *testing.T) {
+	constraintFunc := macaroons.IPLockConstraint("127.0.0/800");
+	testMacaroon := createDummyMacaroon(t)
+	err := constraintFunc(testMacaroon)
+	if err == nil {
+		t.Fatalf("IPLockConstraint with bad IP should fail.")
+	}
+}

macaroons/service.go

@@ -85,7 +85,9 @@ func isRegistered(c *checkers.Checker, name string) bool {
 	}
 
 	for _, info := range c.Info() {
-		if info.Name == name && info.Prefix == "std" {
+		if info.Name == name &&
+			info.Prefix == "" &&
+			info.Namespace == "std" {
 			return true
 		}
 	}

macaroons/service_test.go

@@ -0,0 +1,136 @@
+package macaroons_test
+
+import (
+	"testing"
+	"path"
+	"os"
+	"context"
+	"io/ioutil"
+	"encoding/hex"
+
+	"github.com/coreos/bbolt"
+	"github.com/lightningnetwork/lnd/macaroons"
+	"gopkg.in/macaroon-bakery.v2/bakery/checkers"
+	"gopkg.in/macaroon-bakery.v2/bakery"
+	"google.golang.org/grpc/metadata"
+)
+
+var (
+	testOperation = bakery.Op{
+		Entity: "testEntity",
+		Action: "read",
+	}
+	defaultPw = []byte("hello")
+)
+
+// setupTestRootKeyStorage creates a dummy root key storage by
+// creating a temporary macaroons.db and initializing it with the
+// default password of 'hello'. Only the path to the temporary
+// DB file is returned, because the service will open the file
+// and read the store on its own.
+func setupTestRootKeyStorage(t *testing.T) string {
+	tempDir, err := ioutil.TempDir("", "macaroonstore-")
+	if err != nil {
+		t.Fatalf("Error creating temp dir: %v", err)
+	}
+	db, err := bolt.Open(path.Join(tempDir, "macaroons.db"), 0600,
+		bolt.DefaultOptions)
+	if err != nil {
+		t.Fatalf("Error opening store DB: %v", err)
+	}
+	store, err := macaroons.NewRootKeyStorage(db)
+	if err != nil {
+		db.Close()
+		t.Fatalf("Error creating root key store: %v", err)
+	}
+	defer store.Close()
+	err = store.CreateUnlock(&defaultPw)
+	return tempDir
+}
+
+// TestNewService tests the creation of the macaroon service.
+func TestNewService(t *testing.T) {
+	// First, initialize a dummy DB file with a store that the service
+	// can read from. Make sure the file is removed in the end.
+	tempDir := setupTestRootKeyStorage(t)
+	defer os.RemoveAll(tempDir)
+
+	// Second, create the new service instance, unlock it and pass in a
+	// checker that we expect it to add to the bakery.
+	service, err := macaroons.NewService(tempDir, macaroons.IPLockChecker)
+	defer service.Close()
+	if err != nil {
+		t.Fatalf("Error creating new service: %v", err)
+	}
+	err = service.CreateUnlock(&defaultPw)
+	if err != nil {
+		t.Fatalf("Error unlocking root key storage: %v", err)
+	}
+
+	// Third, check if the created service can bake macaroons.
+	macaroon, err := service.Oven.NewMacaroon(nil, bakery.LatestVersion,
+		nil, testOperation)
+	if err != nil {
+		t.Fatalf("Error creating macaroon from service: %v", err)
+	}
+	if macaroon.Namespace().String() != "std:" {
+		t.Fatalf("The created macaroon has an invalid namespace: %s",
+			macaroon.Namespace().String())
+	}
+
+	// Finally, check if the service has been initialized correctly and
+	// the checker has been added.
+	var checkerFound = false
+	checker := service.Checker.FirstPartyCaveatChecker.(*checkers.Checker)
+	for _, info := range checker.Info() {
+		if info.Name == "ipaddr" &&
+			info.Prefix == "" &&
+			info.Namespace == "std" {
+			checkerFound = true
+		}
+	}
+	if !checkerFound {
+		t.Fatalf("Checker '%s' not found in service.", "ipaddr")
+	}
+}
+
+// TestValidateMacaroon tests the validation of a macaroon that is in an
+// incoming context.
+func TestValidateMacaroon(t *testing.T) {
+	// First, initialize the service and unlock it.
+	tempDir := setupTestRootKeyStorage(t)
+	defer os.RemoveAll(tempDir)
+	service, err := macaroons.NewService(tempDir, macaroons.IPLockChecker)
+	defer service.Close()
+	if err != nil {
+		t.Fatalf("Error creating new service: %v", err)
+	}
+	err = service.CreateUnlock(&defaultPw)
+	if err != nil {
+		t.Fatalf("Error unlocking root key storage: %v", err)
+	}
+
+	// Then, create a new macaroon that we can serialize.
+	macaroon, err := service.Oven.NewMacaroon(nil, bakery.LatestVersion,
+		nil, testOperation)
+	if err != nil {
+		t.Fatalf("Error creating macaroon from service: %v", err)
+	}
+	macaroonBinary, err := macaroon.M().MarshalBinary()
+	if err != nil {
+		t.Fatalf("Error serializing macaroon: %v", err)
+	}
+
+	// Because the macaroons are always passed in a context, we need to
+	// mock one that has just the serialized macaroon as a value.
+	md := metadata.New(map[string]string{
+		"macaroon": hex.EncodeToString(macaroonBinary),
+	})
+	mockContext := metadata.NewIncomingContext(context.Background(), md)
+
+	// Finally, validate the macaroon against the required permissions.
+	err = service.ValidateMacaroon(mockContext, []bakery.Op{testOperation})
+	if err != nil {
+		t.Fatalf("Error validating the macaroon: %v", err)
+	}
+}

rpcserver.go

@@ -110,7 +110,7 @@ var (
 
 	// invoicePermissions is a slice of all the entities that allows a user
 	// to only access calls that are related to invoices, so: streaming
-	// RPC's, generating, and listening invoices.
+	// RPCs, generating, and listening invoices.
 	invoicePermissions = []bakery.Op{
 		{
 			Entity: "invoices",