Skip to content

gh-152212: Reject a POSIX TZ footer with a missing std offset in pure-Python zoneinfo #152213

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
StanFromIreland merged 2 commits into from
Jun 27, 2026
Merged

gh-152212: Reject a POSIX TZ footer with a missing std offset in pure-Python zoneinfo #152213

Show file tree
Hide file tree
Changes from 1 commit
Commits
Show all changes
2 commits
Select commit Hold shift + click to select a range
babe3da
gh-152212: Reject a POSIX TZ footer with a missing std offset in pure…
tonghuaroot Jun 25, 2026
aec9aea
gh-152212: Add STD-offset-required comment and tighten NEWS per review
tonghuaroot Jun 27, 2026
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
Next Next commit
gh-152212: Reject a POSIX TZ footer with a missing std offset in pure… 
…-Python zoneinfo

The pure-Python _parse_tz_str defaulted a missing std offset to 0, so a POSIX TZ
footer with a bare std abbreviation and no offset (e.g. 'AAA') was silently accepted
as a fixed offset-0 zone.  POSIX requires the offset after std, and the C accelerator
already rejects it, so the pure-Python parser now raises ValueError to match.
  • Loading branch information
@tonghuaroot
tonghuaroot committed Jun 25, 2026
commit babe3da7705c186e15b2779499ce53d78f66c22a
5 changes: 5 additions & 0 deletions Lib/test/test_zoneinfo/test_zoneinfo.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -1142,6 +1142,11 @@ def test_extreme_tzstr(self):
def test_invalid_tzstr(self):
invalid_tzstrs = [
"PST8PDT", # DST but no transition specified
# gh-152212: the std offset is required (POSIX TZ grammar)
"AAA",
"A",

@StanFromIreland StanFromIreland Jun 26, 2026 •
edited
Loading

Copy link
Copy Markdown
Member

Choose a reason for hiding this comment

The reason will be displayed to describe this comment to others. Learn more.

I was going to say these are rejected for another reason, i.e. because of the spec's required length:

three byte minimum length

But of course, we don't enforce that. However, I'm also not sure if this is just part of the 2024 updated spec, and I don't have time to check right now. I'll put this on my to-do list.

"AA",
"B",
"+11", # Unquoted alphanumeric
"GMT,M3.2.0/2,M11.1.0/3", # Transition rule but no DST
"GMT0+11,M3.2.0/2,M11.1.0/3", # Unquoted alphanumeric in DST
Expand Down
2 changes: 1 addition & 1 deletion Lib/zoneinfo/_zoneinfo.py
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -672,7 +672,7 @@ def _parse_tz_str(tz_str):
except ValueError as e:
raise ValueError(f"Invalid STD offset in {tz_str}") from e
else:
std_offset = 0
raise ValueError(f"Invalid STD offset in {tz_str}")
Comment thread
StanFromIreland marked this conversation as resolved.

if dst_abbr is not None:
if dst_offset := m.group("dstoff"):
Expand Down
6 changes: 6 additions & 0 deletions Misc/NEWS.d/next/Library/2026-06-25-12-00-00.gh-issue-152212.Zk7Qm2.rst
View file
Open in desktop
Original file line number Diff line number Diff line change
@@ -0,0 +1,6 @@
Fixed a parity bug in the pure-Python :mod:`zoneinfo` implementation, which
accepted a POSIX TZ footer whose ``std`` field had no offset (for example
``AAA``), silently building a fixed offset-0 zone. Such a string is invalid per
POSIX (the offset following ``std`` is required), and the C accelerator already
rejects it; the pure-Python parser now raises :exc:`ValueError` to match.
Patch by tonghuaroot.
Comment thread
StanFromIreland marked this conversation as resolved.
Outdated
Loading