unmarshal: validate date (#622)

decode.go

@@ -43,6 +43,10 @@ func parseLocalDate(b []byte) (LocalDate, error) {
 
 	date.Day = parseDecimalDigits(b[8:10])
 
+	if !isValidDate(date.Year, date.Month, date.Day) {
+		return LocalDate{}, newDecodeError(b, "impossible date")
+	}
+
 	return date, nil
 }
 
@@ -330,3 +334,38 @@ func checkAndRemoveUnderscores(b []byte) ([]byte, error) {
 
 	return cleaned, nil
 }
+
+// isValidDate checks if a provided date is a date that exists.
+func isValidDate(year int, month int, day int) bool {
+	return day <= daysIn(month, year)
+}
+
+// daysBefore[m] counts the number of days in a non-leap year
+// before month m begins. There is an entry for m=12, counting
+// the number of days before January of next year (365).
+var daysBefore = [...]int32{
+	0,
+	31,
+	31 + 28,
+	31 + 28 + 31,
+	31 + 28 + 31 + 30,
+	31 + 28 + 31 + 30 + 31,
+	31 + 28 + 31 + 30 + 31 + 30,
+	31 + 28 + 31 + 30 + 31 + 30 + 31,
+	31 + 28 + 31 + 30 + 31 + 30 + 31 + 31,
+	31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30,
+	31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31,
+	31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30,
+	31 + 28 + 31 + 30 + 31 + 30 + 31 + 31 + 30 + 31 + 30 + 31,
+}
+
+func daysIn(m int, year int) int {
+	if m == 2 && isLeap(year) {
+		return 29
+	}
+	return int(daysBefore[m] - daysBefore[m-1])
+}
+
+func isLeap(year int) bool {
+	return year%4 == 0 && (year%100 != 0 || year%400 == 0)
+}

toml_testgen_test.go

@@ -176,7 +176,6 @@ func TestTOMLTest_Invalid_Control_StringUs(t *testing.T) {
 }
 
 func TestTOMLTest_Invalid_Datetime_ImpossibleDate(t *testing.T) {
-	t.Skip("FIXME")
 	input := "d = 2006-01-50T00:00:00Z\n"
 	testgenInvalid(t, input)
 }

unmarshaler_test.go

@@ -353,6 +353,22 @@ func TestUnmarshal(t *testing.T) {
 				}
 			},
 		},
+		{
+			desc:  "local leap-day date into interface",
+			input: `a = 2020-02-29`,
+			gen: func() test {
+				type doc struct {
+					A interface{}
+				}
+
+				return test{
+					target: &doc{},
+					expected: &doc{
+						A: toml.LocalDate{2020, 2, 29},
+					},
+				}
+			},
+		},
 		{
 			desc:  "local-time with nano second",
 			input: `a = 12:08:05.666666666`,
@@ -2091,6 +2107,16 @@ world'`,
 			desc: "multiline basic string with unfinished escape sequence after the first escape code",
 			data: "a = \"\"\"\\t\\",
 		},
+		{
+			desc: `impossible date-day`,
+			data: `A = 2021-03-40T23:59:00`,
+			msg:  `impossible date`,
+		},
+		{
+			desc: `leap day in non-leap year`,
+			data: `A = 2021-02-29T23:59:00`,
+			msg:  `impossible date`,
+		},
 	}
 
 	for _, e := range examples {