Base64 encode the signatrue when sending signature body from server and base64...

Base64 encode the signatrue when sending signature body from server and base64 decode signature when retriving signature  bodyfrom client

shim/runtime/signature/client/client.go

@@ -3,6 +3,7 @@ package client
 import (
 	"bytes"
 	"crypto/tls"
+	"encoding/base64"
 	"encoding/json"
 	"fmt"
 	"io/ioutil"
@@ -91,7 +92,12 @@ func (c *pkcs1Client) Sign(data []byte) (signature []byte, publicKey []byte, err
 		glog.Errorf("failed to unmarshal sign response,%v", err)
 		return nil, nil, err
 	}
-	return []byte(payload.Signature), []byte(payload.PublicKey), nil
+	decode, err := base64.StdEncoding.DecodeString(payload.Signature)
+	if err != nil {
+		glog.Errorf("failed to decode signature,%v", err)
+		return nil, nil, err
+	}
+	return decode, []byte(payload.PublicKey), nil
 }
 
 func (c *pkcs1Client) GetStandard() SignStandard {

shim/runtime/signature/server/api/handler.go

@@ -5,6 +5,7 @@ import (
 	"crypto/rand"
 	"crypto/rsa"
 	"crypto/sha256"
+	"encoding/base64"
 	"io/ioutil"
 	"net/http"
 
@@ -34,7 +35,7 @@ func (s *ApiServer) pkcs1Handler(c *gin.Context) {
 		return
 	}
 
-	payload.Signature = string(signedBytes)
+	payload.Signature = base64.StdEncoding.EncodeToString(signedBytes)
 	bytes, err := ioutil.ReadFile(s.publicKeyFilePath)
 	if err != nil {
 		glog.Errorf("failed to parse public key, public key path: %s, err:%v", s.publicKeyFilePath, err.Error())