added hmac sha256 support

sha256.go

@@ -0,0 +1,34 @@
+package jwt
+
+import (
+	"crypto/sha256"
+	"crypto/hmac"
+	"bytes"
+	"errors"
+)
+
+type SigningMethodHS256 struct{}
+
+func init() {
+	RegisterSigningMethod("HS256", func() SigningMethod {
+		return new(SigningMethodHS256)
+	})
+}
+
+func (m *SigningMethodHS256) Verify(signingString, signature string, key []byte) (err error) {
+	// Key
+	var sig []byte
+	if sig, err = DecodeSegment(signature); err == nil {
+		hasher := hmac.New(sha256.New, key)
+		hasher.Write([]byte(signingString))
+
+		if !bytes.Equal(sig, hasher.Sum(nil)) {
+			err = errors.New("Signature is invalid")
+		}
+	}
+	return
+}
+
+func (m *SigningMethodHS256) Sign(token *Token, key []byte) error {
+	return nil
+}

sha256_test.go

@@ -0,0 +1,48 @@
+package jwt
+
+import (
+	"strings"
+	"testing"
+)
+
+var sha256TestData = []struct {
+	name        string
+	tokenString string
+	claims      map[string]interface{}
+	valid       bool
+}{
+	{
+		"web sample",
+		"eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ.dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXk",
+		map[string]interface{}{"iss": "joe", "exp": 1300819380, "http://example.com/is_root": true},
+		true,
+	},
+	{
+		"web sample: invalid",
+		"eyJ0eXAiOiJKV1QiLA0KICJhbGciOiJIUzI1NiJ9.eyJpc3MiOiJqb2UiLA0KICJleHAiOjEzMDA4MTkzODAsDQogImh0dHA6Ly9leGFtcGxlLmNvbS9pc19yb290Ijp0cnVlfQ.dBjftJeZ4CVP-mB92K27uhbUJU1p1r_wW1gFWFOEjXo",
+		map[string]interface{}{"iss": "joe", "exp": 1300819380, "http://example.com/is_root": true},
+		false,
+	},
+}
+// Sample data from http://tools.ietf.org/html/draft-jones-json-web-signature-04#appendix-A.1
+var sha256TestKey = []byte{
+	3, 35, 53, 75, 43, 15, 165, 188, 131, 126, 6, 101, 119, 123, 166,
+	143, 90, 179, 40, 230, 240, 84, 201, 40, 169, 15, 132, 178, 210, 80,
+	46, 191, 211, 251, 90, 146, 210, 6, 71, 239, 150, 138, 180, 195, 119,
+	98, 61, 34, 61, 46, 33, 114, 5, 46, 79, 8, 192, 205, 154, 245, 103,
+	208, 128, 163 }
+
+func TestHS256Verify(t *testing.T) {
+	for _, data := range sha256TestData {
+		parts := strings.Split(data.tokenString, ".")
+
+		method, _ := GetSigningMethod("HS256")
+		err := method.Verify(strings.Join(parts[0:2], "."), parts[2], sha256TestKey)
+		if data.valid && err != nil {
+			t.Errorf("[%v] Error while verifying key: %v", data.name, err)
+		}
+		if !data.valid && err == nil {
+			t.Errorf("[%v] Invalid key passed validation", data.name)
+		}
+	}
+}