fix: str_to_isoformat for unformatted datetime

[0xAlcidius]

Summary

Introduce str_to_isoformat to format datetime strings encountered in Windows Task Scheduler XML. This ensures non-padded months/days and space-separated datetimes are converted into strict ISO 8601 strings.

Motivation

Parsing a velo package could result in the following error:

  File "/usr/lib/pypy/lib/pypy3.11/datetime.py", line 1852, in fromisoformat
    raise ValueError(
ValueError: Invalid isoformat string: '2025-7-29T16:34:00'

This PR solves that issue.

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[0xAlcidius]

@DissectBot agree [company="Hunt & Hackett"]

[bobkarreman]

Hi @0xAlcidius thanks for your contribution.

Can you please add some unit-tests for this case?

Maybe the fix can be much easier by parsing the datetime with datetime.strptime something like this:

datetime.strptime("2025-7-9T16:34:00", "%Y-%m-%dT%H:%M:%S")

But I'm not sure if the format is always the same else some variants could be added to the parse function. Besides that you can simply return a datetime object, no need to format it as a string.

[0xAlcidius]

Thank you @bobkarreman for your comment and suggestion! I’ve noticed that Windows Scheduled Tasks can be a bit inconsistent when it comes to the StartBoundary. I did try using datetime.strptime, but given the ambiguity in the formats, I leaned towards string manipulation instead. Returning a datetime object would definitely be a cleaner approach.

Could you point me to the right place in the codebase to add the unit tests?

[Schamper]

Could you point me to the right place in the codebase to add the unit tests?

https://github.com/fox-it/dissect.target/blob/main/tests/plugins/os/windows/test_tasks.py

[0xAlcidius]

Added a few test cases with timestamps observed in scheduled tasks. str_to_isoformat now also returns a datetime object as was suggested.

[B0TAxy]

Should we also update the records and change the return type to datetime?

[bobkarreman]

Added a few test cases with timestamps observed in scheduled tasks. str_to_isoformat now also returns a datetime object as was suggested.

Please also include a test case for the case you described in the this PR ('2025-7-29T16:34:00')

[bobkarreman]

Thank you @bobkarreman for your comment and suggestion! I’ve noticed that Windows Scheduled Tasks can be a bit inconsistent when it comes to the StartBoundary. I did try using datetime.strptime, but given the ambiguity in the formats, I leaned towards string manipulation instead. Returning a datetime object would definitely be a cleaner approach.

Could you point me to the right place in the codebase to add the unit tests?

Parsing it with datetime.fromisoformat with some fallback logic is a cleaner way in my opinion (also fromisoformat has been improved in 3.11 so will work in almost all of the test cases).

Could be something like this:

def parse(s):
    try:
        d = datetime.fromisoformat(s)
    except ValueError:
        s = s.replace(" ", "T")
        if 'Z' in s:
            d = datetime.strptime(s, "%Y-%m-%dT%H:%M:%SZ")
            return d.replace(tzinfo=timezone.utc)
        d = datetime.strptime(s, "%Y-%m-%dT%H:%M:%S")
    return d

[bobkarreman]

Should we also update the records and change the return type to datetime?

@B0TAxy The record already has the type datetime for start and end boundary. Or are you referring to something else?

[0xAlcidius]

@bobkarreman Following your suggestion, I’ve refactored the function to make it cleaner while maintaining the same functionality. Additionally, I’ve added the missing test case you mentioned earlier.

[B0TAxy]

Should we also update the records and change the return type to datetime?

@B0TAxy The record already has the type datetime for start and end boundary. Or are you referring to something else?

My mistake — you’re correct, the records are already in datetime format. Thanks for clarifying!

[0xAlcidius]

@bobkarreman Thank for you your review! I provided changes accordingly.

[0xAlcidius]

@bobkarreman @Schamper Would any of you have had the time to look at the changes yet?

[bobkarreman]

@bobkarreman Thank for you your review! I provided changes accordingly.

I was on holiday and after that quite busy so didn't have time to look at it. I provided some feedback, let me know if its unclear else we can maybe have a chat on Discord or something if that makes it easier.