Add token generation using go macaroon (#437)

* Add Go macaroon library

Signed-off-by: Anant Prakash <anantprakashjsr@gmail.com>

* Add macaroon generation and serialization, for login token.

Signed-off-by: Anant Prakash <anantprakashjsr@gmail.com>

* Remove copyright, trim empty lines

* Make Serialize functions private

* Fix typos

src/github.com/matrix-org/dendrite/clientapi/auth/tokens/tokens.go

@@ -0,0 +1,132 @@
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tokens
+
+import (
+	"encoding/base64"
+	"errors"
+	"fmt"
+	"strconv"
+	"time"
+
+	"github.com/go-macaroon/macaroon"
+)
+
+const (
+	macaroonVersion = macaroon.V2
+	defaultDuration = 2 * 60
+	// UserPrefix is a common prefix for every user_id caveat
+	UserPrefix = "user_id = "
+	// TimePrefix is a common prefix for every expiry caveat
+	TimePrefix = "time < "
+	// Gen is a common caveat for every token
+	Gen = "gen = 1"
+)
+
+// TokenOptions represent parameters of Token
+type TokenOptions struct {
+	ServerPrivateKey []byte `yaml:"private_key"`
+	ServerName       string `yaml:"server_name"`
+	UserID           string `json:"user_id"`
+	Duration         int    // optional
+}
+
+// GenerateLoginToken generates a short term login token to be used as
+// token authentication ("m.login.token")
+func GenerateLoginToken(op TokenOptions) (string, error) {
+	if !isValidTokenOptions(op) {
+		return "", errors.New("The given TokenOptions is invalid")
+	}
+
+	mac, err := generateBaseMacaroon(op.ServerPrivateKey, op.ServerName, op.UserID)
+	if err != nil {
+		return "", err
+	}
+
+	if op.Duration == 0 {
+		op.Duration = defaultDuration
+	}
+	now := time.Now().Second()
+	expiryCaveat := TimePrefix + strconv.Itoa(now+op.Duration)
+	err = mac.AddFirstPartyCaveat([]byte(expiryCaveat))
+	if err != nil {
+		return "", macaroonError(err)
+	}
+
+	urlSafeEncode, err := serializeMacaroon(*mac)
+	if err != nil {
+		return "", macaroonError(err)
+	}
+	return urlSafeEncode, nil
+}
+
+// isValidTokenOptions checks for required fields in a TokenOptions
+func isValidTokenOptions(op TokenOptions) bool {
+	if op.ServerPrivateKey == nil || op.ServerName == "" || op.UserID == "" {
+		return false
+	}
+	return true
+}
+
+// generateBaseMacaroon generates a base macaroon common for accessToken & loginToken.
+// Returns a macaroon tied with userID,
+// returns an error if something goes wrong.
+func generateBaseMacaroon(
+	secret []byte, ServerName string, userID string,
+) (*macaroon.Macaroon, error) {
+	mac, err := macaroon.New(secret, []byte(userID), ServerName, macaroonVersion)
+	if err != nil {
+		return nil, macaroonError(err)
+	}
+
+	err = mac.AddFirstPartyCaveat([]byte(Gen))
+	if err != nil {
+		return nil, macaroonError(err)
+	}
+
+	err = mac.AddFirstPartyCaveat([]byte(UserPrefix + userID))
+	if err != nil {
+		return nil, macaroonError(err)
+	}
+
+	return mac, nil
+}
+
+func macaroonError(err error) error {
+	return fmt.Errorf("Macaroon creation failed: %s", err.Error())
+}
+
+// serializeMacaroon takes a macaroon to be serialized.
+// returns its base64 encoded string, URL safe, which can be sent via web, email, etc.
+func serializeMacaroon(m macaroon.Macaroon) (string, error) {
+	bin, err := m.MarshalBinary()
+	if err != nil {
+		return "", err
+	}
+
+	urlSafeEncode := base64.RawURLEncoding.EncodeToString(bin)
+	return urlSafeEncode, nil
+}
+
+// deSerializeMacaroon takes a base64 encoded string of a macaroon to be de-serialized.
+// Returns a macaroon. On failure returns error with description.
+func deSerializeMacaroon(urlSafeEncode string) (macaroon.Macaroon, error) {
+	var mac macaroon.Macaroon
+	bin, err := base64.RawURLEncoding.DecodeString(urlSafeEncode)
+	if err != nil {
+		return mac, err
+	}
+
+	err = mac.UnmarshalBinary(bin)
+	return mac, err
+}

src/github.com/matrix-org/dendrite/clientapi/auth/tokens/tokens_test.go

@@ -0,0 +1,80 @@
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package tokens
+
+import (
+	"testing"
+)
+
+var (
+	validTokenOp = TokenOptions{
+		ServerPrivateKey: []byte("aSecretKey"),
+		ServerName:       "aRandomServerName",
+		UserID:           "aRandomUserID",
+	}
+	invalidTokenOps = map[string]TokenOptions{
+		"ServerPrivateKey": {
+			ServerName: "aRandomServerName",
+			UserID:     "aRandomUserID",
+		},
+		"ServerName": {
+			ServerPrivateKey: []byte("aSecretKey"),
+			UserID:           "aRandomUserID",
+		},
+		"UserID": {
+			ServerPrivateKey: []byte("aSecretKey"),
+			ServerName:       "aRandomServerName",
+		},
+	}
+)
+
+func TestGenerateLoginToken(t *testing.T) {
+	// Test valid
+	_, err := GenerateLoginToken(validTokenOp)
+	if err != nil {
+		t.Errorf("Token generation failed for valid TokenOptions with err: %s", err.Error())
+	}
+
+	// Test invalids
+	for missing, invalidTokenOp := range invalidTokenOps {
+		_, err := GenerateLoginToken(invalidTokenOp)
+		if err == nil {
+			t.Errorf("Token generation should fail for TokenOptions with missing %s", missing)
+		}
+	}
+}
+
+func serializationTestError(err error) string {
+	return "Token Serialization test failed with err: " + err.Error()
+}
+
+func TestSerialization(t *testing.T) {
+	fakeToken, err := GenerateLoginToken(validTokenOp)
+	if err != nil {
+		t.Errorf(serializationTestError(err))
+	}
+
+	fakeMacaroon, err := deSerializeMacaroon(fakeToken)
+	if err != nil {
+		t.Errorf(serializationTestError(err))
+	}
+
+	sameFakeToken, err := serializeMacaroon(fakeMacaroon)
+	if err != nil {
+		t.Errorf(serializationTestError(err))
+	}
+
+	if sameFakeToken != fakeToken {
+		t.Errorf("Token Serialization mismatch")
+	}
+}