add Google HMAC auth

google_geocoder.go

@@ -2,6 +2,9 @@ package geo
 
 import (
 	"bytes"
+	"crypto/hmac"
+	"crypto/sha1"
+	"encoding/base64"
 	"encoding/json"
 	"errors"
 	"fmt"
@@ -44,6 +47,9 @@ var googleGeocodeURL = "https://maps.googleapis.com/maps/api/geocode/json"
 
 var GoogleAPIKey = ""
 
+var GoogleClientId = ""
+var GooglePrivateKey []byte
+
 // Note:  In the next major revision (1.0.0), it is planned
 //        That Geocoders should adhere to the `geo.Geocoder`
 //        interface and provide versioning of APIs accordingly.
@@ -56,6 +62,19 @@ func SetGoogleAPIKey(newAPIKey string) {
 	GoogleAPIKey = newAPIKey
 }
 
+func SetGoogleClientId(newClientId string) {
+	GoogleClientId = newClientId
+}
+
+func SetGooglePrivateKey(newBase64PrivateKey string) error {
+	privateKey, err := base64.URLEncoding.DecodeString(newBase64PrivateKey)
+	if err != nil {
+		return err
+	}
+	GooglePrivateKey = privateKey
+	return nil
+}
+
 // Issues a request to the google geocoding service and forwards the passed in params string
 // as a URL-encoded entity.  Returns an array of byes as a result, or an error if one occurs during the process.
 // Note: Since this is an arbitrary request, you are responsible for passing in your API key if you want one.
@@ -130,6 +149,15 @@ func googleGeocodeQueryStr(address string) (string, error) {
 		if err != nil {
 			return "", err
 		}
+	} else if GoogleClientId != "" && len(GooglePrivateKey) != 0 {
+		queryStr.WriteString(fmt.Sprintf("&client=%s", GoogleClientId))
+
+		signature, signatureErr := calculateSignature(string(queryStr.Bytes()))
+		if signatureErr != nil {
+			return "", err
+		}
+
+		queryStr.WriteString(fmt.Sprintf("&signature=%s", signature))
 	}
 
 	return queryStr.String(), err
@@ -173,7 +201,34 @@ func googleReverseGeocodeQueryStr(p *Point) (string, error) {
 		if err != nil {
 			return "", err
 		}
+	} else if GoogleClientId != "" && len(GooglePrivateKey) != 0 {
+		queryStr.WriteString(fmt.Sprintf("&client=%s", GoogleClientId))
+
+		signature, signatureErr := calculateSignature(string(queryStr.Bytes()))
+		if signatureErr != nil {
+			return "", err
+		}
+
+		queryStr.WriteString(fmt.Sprintf("&signature=%s", signature))
 	}
 
 	return queryStr.String(), err
 }
+
+func calculateSignature(queryString string) (signature string, err error) {
+	url, parseErr := url.Parse(googleGeocodeURL)
+	if parseErr != nil {
+		return "", parseErr
+	}
+
+	var pathAndQuery bytes.Buffer
+	pathAndQuery.WriteString(url.Path)
+	pathAndQuery.WriteString("?")
+	pathAndQuery.WriteString("sensor=false&") //is added in the Request method, so we have to supply it in our string to hash
+	pathAndQuery.WriteString(queryString)
+
+	h := hmac.New(sha1.New, GooglePrivateKey)
+	h.Write(pathAndQuery.Bytes())
+
+	return base64.URLEncoding.EncodeToString(h.Sum(nil)), nil
+}