time: time.Parse accepts out of range value for offsets, and can't always be roundtripped #67470
Description
When passing an offset like +99:99 to time.Parse like so:
func main() {
t, err := time.Parse("-07:00", "+99:99")
fmt.Println(err, t.Format(time.RFC3339))
_, off := t.Zone()
fmt.Println("offset", off)
// Round-trip.
fmt.Println(time.Parse("-07:00", t.Format("-07:00")))
}
The initial Parse will work without error, but the second fails. The above outputs:
<nil> 0000-01-01T00:00:00+100:39
offset 362340
0001-01-01 00:00:00 +0000 UTC parsing time "+100:39" as "-07:00": cannot parse "+100:39" as "-07:00"
The 99 minutes overflows to 01:39. The roundtrip doesn't work because Parse checks if the numbers in hour:min are exactly two digits, so that does return an error.
This is a bit of an obscure edge case that came up during fuzzing; can check that offset >86400 for outrageous offsets to throw an error on parse, but validating the hour:min requires re-parsing the date as that information isn't available.
Everything else (second, minute, hour, day, month) already throws an out of range error so this seems like a good fix. AFAIK these offsets never have and never will be valid. Below is a patch to do exactly that.
commit cfb8f654e8
Author: Martin Tournoij <martin@arp242.net>
Date: Fri May 17 11:34:12 2024 +0100
time: return out of range errors for invalid timezone offsets
diff --git a/src/time/format.go b/src/time/format.go
index 875fb36df8..7b43b5bb05 100644
--- a/src/time/format.go
+++ b/src/time/format.go
@@ -1242,6 +1242,12 @@ func parse(layout, value string, defaultLocation, local *Location) (Time, error)
if err == nil {
ss, _, err = getnum(seconds, true)
}
+ if hr > 24 {
+ return Time{}, newParseError(alayout, avalue, "", value, ": offset hour out of range")
+ }
+ if mm > 59 {
+ return Time{}, newParseError(alayout, avalue, "", value, ": offset minute out of range")
+ }
zoneOffset = (hr*60+mm)*60 + ss // offset is in seconds
switch sign[0] {
case '+':
diff --git a/src/time/time_test.go b/src/time/time_test.go
index 86335e3796..d110c28d4c 100644
--- a/src/time/time_test.go
+++ b/src/time/time_test.go
@@ -832,8 +832,8 @@ func TestUnmarshalInvalidTimes(t *testing.T) {
{`[]`, "Time.UnmarshalJSON: input is not a JSON string"},
{`"2000-01-01T1:12:34Z"`, `<nil>`},
{`"2000-01-01T00:00:00,000Z"`, `<nil>`},
- {`"2000-01-01T00:00:00+24:00"`, `<nil>`},
- {`"2000-01-01T00:00:00+00:60"`, `<nil>`},
+ {`"2000-01-01T00:00:00+25:00"`, `parsing time "2000-01-01T00:00:00+25:00": offset hour out of range`},
+ {`"2000-01-01T00:00:00+00:60"`, `parsing time "2000-01-01T00:00:00+00:60": offset minute out of range`},
{`"2000-01-01T00:00:00+123:45"`, `parsing time "2000-01-01T00:00:00+123:45" as "2006-01-02T15:04:05Z07:00": cannot parse "+123:45" as "Z07:00"`},
}
With 1.22, and current master branch