[FAB-5673] Adds idemix-based MSP implementation

This commit adds an MSP implementation based on identity mixer,
allowing anonymous signing of transactions.

Change-Id: If13221756a019b5a4214ea1b2f06545600082427
Signed-off-by: Manu Drijvers <mdr@zurich.ibm.com>
Signed-off-by: Maria Dubovitskaya <mdu@zurich.ibm.com>

Author: Manu Drijvers

msp/configbuilder.go

@@ -1,35 +1,23 @@
 /*
-Copyright IBM Corp. 2017 All Rights Reserved.
+Copyright IBM Corp. All Rights Reserved.
 
-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.
+SPDX-License-Identifier: Apache-2.0
 */
 
 package msp
 
 import (
+	"encoding/pem"
 	"fmt"
 	"io/ioutil"
-
-	"github.com/golang/protobuf/proto"
-
-	"encoding/pem"
-	"path/filepath"
-
 	"os"
+	"path/filepath"
 
+	"github.com/golang/protobuf/proto"
 	"github.com/hyperledger/fabric/bccsp"
 	"github.com/hyperledger/fabric/bccsp/factory"
 	"github.com/hyperledger/fabric/protos/msp"
+	"github.com/pkg/errors"
 	"gopkg.in/yaml.v2"
 )
 
@@ -276,3 +264,25 @@ func getMspConfig(dir string, ID string, sigid *msp.SigningIdentityInfo) (*msp.M
 
 	return mspconf, nil
 }
+
+// IdemixConfig is the filename of the idemix msp config file
+const IdemixConfig = "idemixmspconfig"
+
+// GetIdemixMspConfig returns the configuration for the Idemix MSP
+func GetIdemixMspConfig(dir string) (*msp.MSPConfig, error) {
+	confStringBytes, err := readFile(filepath.Join(dir, IdemixConfig))
+	if err != nil {
+		return nil, errors.Wrapf(err, "error reading idemix config file")
+	}
+	config := &msp.IdemixMSPConfig{}
+	err = proto.UnmarshalText(string(confStringBytes), config)
+	if err != nil {
+		return nil, errors.Wrapf(err, "error unmarshalling idemix config")
+	}
+	confBytes, err := proto.Marshal(config)
+	if err != nil {
+		return nil, errors.Wrapf(err, "error creating idemix config")
+	}
+
+	return &msp.MSPConfig{Config: confBytes, Type: int32(IDEMIX)}, nil
+}