Fix panic due to invalid schedule string #365
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Fix a bug where cron panics if the schedule string ("spec") has a
particular format, namely "TZ=" or "CRON_TZ=". If this is string is user
controlled that user may be able to panic and thereby exit the program
using cron. Alternatively, if the string is constructed dynamically by
the program and there is a mistake in that logic, it would panic
unexpectedly.
The solution I propose is simply to check against the condition that
causes cron to panic. There are alternative solution, e.g.:
- Using more complex logic (using e.g. regexp) to detect the
"TZ"-syntax.
- Updating parsing logic so that the "provided bad location" error is
returned. I opted away from this as I figured it might be useful to
distinguish these two scenarios.
Disclose: I found this bug using https://github.com/dvyukov/go-fuzz and
did not encounter any other parsing issues.
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Fix a bug where cron panics if the schedule string ("spec") has a particular format, namely exactly "TZ=" or "CRON_TZ=". If this string is user controlled that user may be able to cause a panic and thereby exit the program that is using cron. Alternatively, if the string is constructed dynamically by the program and there is a mistake in that logic, the program would panic unexpectedly.
The solution I propose is simply to check against the condition that causes cron to panic. There are alternative solution, e.g.:
"provided bad location"error is returned. I opted away from this as I figured it might be useful to distinguish these two scenarios.I also added some tests for these strings to ensure they're properly accounted for in the future.
Disclosure: I found this bug using https://github.com/dvyukov/go-fuzz and did not encounter any other parsing issues.