add validation for base64 url without = padding (#1024)

Co-authored-by: Yasoob Haider <yasoob.haider@zomato.com>
Co-authored-by: Dean Karn <Dean.Karn@gmail.com>

README.md

@@ -150,6 +150,7 @@ Baked-in Validations
 | - | - |
 | base64 | Base64 String |
 | base64url | Base64URL String |
+| base64rawurl | Base64RawURL String |
 | bic | Business Identifier Code (ISO 9362) |
 | bcp47_language_tag | Language tag (BCP 47) |
 | btc_addr | Bitcoin Address |

baked_in.go

@@ -129,6 +129,7 @@ var (
 		"file":                          isFile,
 		"base64":                        isBase64,
 		"base64url":                     isBase64URL,
+		"base64rawurl":                  isBase64RawURL,
 		"contains":                      contains,
 		"containsany":                   containsAny,
 		"containsrune":                  containsRune,
@@ -1364,6 +1365,11 @@ func isBase64URL(fl FieldLevel) bool {
 	return base64URLRegex.MatchString(fl.Field().String())
 }
 
+// isBase64RawURL is the validation function for validating if the current field's value is a valid base64 URL safe string without '=' padding.
+func isBase64RawURL(fl FieldLevel) bool {
+	return base64RawURLRegex.MatchString(fl.Field().String())
+}
+
 // isURI is the validation function for validating if the current field's value is a valid URI.
 func isURI(fl FieldLevel) bool {
 	field := fl.Field()

regexes.go

@@ -19,6 +19,7 @@ const (
 	e164RegexString                  = "^\\+[1-9]?[0-9]{7,14}$"
 	base64RegexString                = "^(?:[A-Za-z0-9+\\/]{4})*(?:[A-Za-z0-9+\\/]{2}==|[A-Za-z0-9+\\/]{3}=|[A-Za-z0-9+\\/]{4})$"
 	base64URLRegexString             = "^(?:[A-Za-z0-9-_]{4})*(?:[A-Za-z0-9-_]{2}==|[A-Za-z0-9-_]{3}=|[A-Za-z0-9-_]{4})$"
+	base64RawURLRegexString          = "^(?:[A-Za-z0-9-_]{4})*(?:[A-Za-z0-9-_]{2,4})$"
 	iSBN10RegexString                = "^(?:[0-9]{9}X|[0-9]{10})$"
 	iSBN13RegexString                = "^(?:(?:97(?:8|9))[0-9]{10})$"
 	uUID3RegexString                 = "^[0-9a-f]{8}-[0-9a-f]{4}-3[0-9a-f]{3}-[0-9a-f]{4}-[0-9a-f]{12}$"
@@ -84,6 +85,7 @@ var (
 	emailRegex                 = regexp.MustCompile(emailRegexString)
 	base64Regex                = regexp.MustCompile(base64RegexString)
 	base64URLRegex             = regexp.MustCompile(base64URLRegexString)
+	base64RawURLRegex          = regexp.MustCompile(base64RawURLRegexString)
 	iSBN10Regex                = regexp.MustCompile(iSBN10RegexString)
 	iSBN13Regex                = regexp.MustCompile(iSBN13RegexString)
 	uUID3Regex                 = regexp.MustCompile(uUID3RegexString)

validator.go

@@ -452,7 +452,6 @@ OUTER:
 			v.ct = ct
 
 			if !ct.fn(ctx, v) {
-
 				v.str1 = string(append(ns, cf.altName...))
 
 				if v.v.hasTagNameFunc {

validator_instance.go

@@ -613,7 +613,7 @@ func (v *Validate) Var(field interface{}, tag string) error {
 }
 
 // VarCtx validates a single variable using tag style validation and allows passing of contextual
-// validation validation information via context.Context.
+// validation information via context.Context.
 // eg.
 // var i int
 // validate.Var(i, "gt=1,lt=10")
@@ -632,6 +632,7 @@ func (v *Validate) VarCtx(ctx context.Context, field interface{}, tag string) (e
 	}
 
 	ctag := v.fetchCacheTag(tag)
+
 	val := reflect.ValueOf(field)
 	vd := v.pool.Get().(*validate)
 	vd.top = val

validator_test.go

@@ -5652,6 +5652,53 @@ func TestBase64URLValidation(t *testing.T) {
 	}
 }
 
+func TestBase64RawURLValidation(t *testing.T) {
+	validate := New()
+
+	testCases := []struct {
+		decoded, encoded string
+		success          bool
+	}{
+		// empty string, although a valid base64 string, should fail
+		{"", "", false},
+		// invalid length
+		{"", "a", false},
+		// base64 with padding should fail
+		{"f", "Zg==", false},
+		{"fo", "Zm8=", false},
+		// base64 without padding
+		{"foo", "Zm9v", true},
+		{"hello", "aGVsbG8", true},
+		{"", "aGVsb", false},
+		// // base64 URL safe encoding with invalid, special characters '+' and '/'
+		{"\x14\xfb\x9c\x03\xd9\x7e", "FPucA9l+", false},
+		{"\x14\xfb\x9c\x03\xf9\x73", "FPucA/lz", false},
+		// // base64 URL safe encoding with valid, special characters '-' and '_'
+		{"\x14\xfb\x9c\x03\xd9\x7e", "FPucA9l-", true},
+		{"\x14\xfb\x9c\x03\xf9\x73", "FPucA_lz", true},
+		// non base64 characters
+		{"", "@mc=", false},
+		{"", "Zm 9", false},
+	}
+	for _, tc := range testCases {
+		err := validate.Var(tc.encoded, "base64rawurl")
+		if tc.success {
+			Equal(t, err, nil)
+			// make sure encoded value is decoded back to the expected value
+			d, innerErr := base64.RawURLEncoding.DecodeString(tc.encoded)
+			Equal(t, innerErr, nil)
+			Equal(t, tc.decoded, string(d))
+		} else {
+			NotEqual(t, err, nil)
+			if len(tc.encoded) > 0 {
+				// make sure that indeed the encoded value was faulty
+				_, err := base64.RawURLEncoding.DecodeString(tc.encoded)
+				NotEqual(t, err, nil)
+			}
+		}
+	}
+}
+
 func TestFileValidation(t *testing.T) {
 	validate := New()