Revert Encoding/Decoding changes for better compatibility

parser_test.go

@@ -435,6 +435,88 @@ func TestParser_ParseUnverified(t *testing.T) {
 	}
 }
 
+var setPaddingTestData = []struct {
+	name          string
+	tokenString   string
+	claims        jwt.Claims
+	paddedDecode  bool
+	signingMethod jwt.SigningMethod
+	keyfunc       jwt.Keyfunc
+	valid         bool
+}{
+	{
+		name:          "Validated non-padded token with padding disabled",
+		tokenString:   "",
+		claims:        jwt.MapClaims{"foo": "paddedbar"},
+		paddedDecode:  false,
+		signingMethod: jwt.SigningMethodRS256,
+		keyfunc:       defaultKeyFunc,
+		valid:         true,
+	},
+	{
+		name:          "Validated non-padded token with padding enabled",
+		tokenString:   "",
+		claims:        jwt.MapClaims{"foo": "paddedbar"},
+		paddedDecode:  true,
+		signingMethod: jwt.SigningMethodRS256,
+		keyfunc:       defaultKeyFunc,
+		valid:         true,
+	},
+	{
+		name:          "Error for padded token with padding disabled",
+		tokenString:   "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJwYWRkZWRiYXIifQ==.20kGGJaYekGTRFf8b0TwhuETcR8lv5z2363X5jf7G1yTWVTwOmte5Ii8L8_OQbYwPoiVHmZY6iJPbt_DhCN42AeFY74BcsUhR-BVrYUVhKK0RppuzEcSlILDNeQsJDLEL035CPm1VO6Jrgk7enQPIctVxUesRgswP71OpGvJxy3j1k_J8p0WzZvRZTe1D_2Misa0UDGwnEIHhmr97fIpMSZjFxlcygQw8QN34IHLHIXMaTY1eiCf4CCr6rOS9wUeu7P3CPkmFq9XhxBT_LLCmIMhHnxP5x27FUJE_JZlfek0MmARcrhpsZS2sFhHAiWrjxjOE27jkDtv1nEwn65wMw==",
+		claims:        jwt.MapClaims{"foo": "paddedbar"},
+		paddedDecode:  false,
+		signingMethod: jwt.SigningMethodRS256,
+		keyfunc:       defaultKeyFunc,
+		valid:         false,
+	},
+	{
+		name:          "Validated padded token with padding enabled",
+		tokenString:   "eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJmb28iOiJwYWRkZWRiYXIifQ==.20kGGJaYekGTRFf8b0TwhuETcR8lv5z2363X5jf7G1yTWVTwOmte5Ii8L8_OQbYwPoiVHmZY6iJPbt_DhCN42AeFY74BcsUhR-BVrYUVhKK0RppuzEcSlILDNeQsJDLEL035CPm1VO6Jrgk7enQPIctVxUesRgswP71OpGvJxy3j1k_J8p0WzZvRZTe1D_2Misa0UDGwnEIHhmr97fIpMSZjFxlcygQw8QN34IHLHIXMaTY1eiCf4CCr6rOS9wUeu7P3CPkmFq9XhxBT_LLCmIMhHnxP5x27FUJE_JZlfek0MmARcrhpsZS2sFhHAiWrjxjOE27jkDtv1nEwn65wMw==",
+		claims:        jwt.MapClaims{"foo": "paddedbar"},
+		paddedDecode:  true,
+		signingMethod: jwt.SigningMethodRS256,
+		keyfunc:       defaultKeyFunc,
+		valid:         true,
+	},
+}
+
+// Extension of Parsing, this is to test out functionality specific to switching codecs with padding.
+func TestSetPadding(t *testing.T) {
+	for _, data := range setPaddingTestData {
+		t.Run(data.name, func(t *testing.T) {
+
+			// If the token string is blank, use helper function to generate string
+			jwt.SetDecodePadding(data.paddedDecode)
+
+			if data.tokenString == "" {
+				data.tokenString = signToken(data.claims, data.signingMethod)
+
+			}
+
+			// Parse the token
+			var token *jwt.Token
+			var err error
+			parser := new(jwt.Parser)
+
+			// Figure out correct claims type
+			token, err = parser.ParseWithClaims(data.tokenString, jwt.MapClaims{}, data.keyfunc)
+
+			if (err == nil) != data.valid || token.Valid != data.valid {
+				t.Errorf("[%v] Error Parsing Token with decoding padding set to %v: %v",
+					data.name,
+					data.paddedDecode,
+					err,
+				)
+			}
+
+		})
+		jwt.SetDecodePadding(false)
+
+	}
+}
+
 func BenchmarkParseUnverified(b *testing.B) {
 
 	// Iterate over test data set and run tests

token.go

@@ -7,6 +7,16 @@ import (
 	"time"
 )
 
+var decodePaddingAllowed bool
+
+// SetDecodePadding will switch the codec used for encoding/decoding JWTs respectively. Note that the JWS RFC7515
+// states that the tokens will utilize a Base64url encoding with no padding. Unfortunately, some implementations
+// of JWT are producing non-standard tokens, and thus require support for decoding. Note that this is a global
+// variable, and updating it will change the behavior on a package level, and is also NOT go-routine safe.
+func SetDecodePadding(setPadding bool) {
+	decodePaddingAllowed = setPadding
+}
+
 // TimeFunc provides the current time when parsing token to validate "exp" claim (expiration time).
 // You can override it to use another time value.  This is useful for testing or if your
 // server uses a different time zone than your tokens.
@@ -112,5 +122,12 @@ func EncodeSegment(seg []byte) string {
 // Deprecated: In a future release, we will demote this function to a non-exported function, since it
 // should only be used internally
 func DecodeSegment(seg string) ([]byte, error) {
+	if decodePaddingAllowed {
+		if l := len(seg) % 4; l > 0 {
+			seg += strings.Repeat("=", 4-l)
+		}
+		return base64.URLEncoding.DecodeString(seg)
+	}
+
 	return base64.RawURLEncoding.DecodeString(seg)
 }