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get_obs_local_part fails to handle empty local part #86650

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get_obs_local_part fails to handle empty local part#86650
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3.8 (EOL)end of life3.9 (EOL)end of lifetopic-emailtype-bugAn unexpected behavior, bug, or error

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@dicksonch
dicksonch
mannequin
opened on Nov 27, 2020
BPO 42484
Nosy @warsaw, @bitdancer, @ZackerySpytz, @dicksonch
PRs
  • gh-86650: get_obs_local_part() fails to handle empty local part #24669
    		•

    Note: these values reflect the state of the issue at the time it was migrated and might not reflect the current state.

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    GitHub fields:

    assignee = None
closed_at = None
created_at = <Date 2020-11-27.12:36:59.942>
labels = ['type-bug', '3.8', 'expert-email', '3.9']
title = 'get_obs_local_part fails to handle empty local part'
updated_at = <Date 2021-02-28.16:44:21.314>
user = 'https://github.com/dicksonch'

    bugs.python.org fields:

    activity = <Date 2021-02-28.16:44:21.314>
actor = 'ZackerySpytz'
assignee = 'none'
closed = False
closed_date = None
closer = None
components = ['email']
creation = <Date 2020-11-27.12:36:59.942>
creator = 'dxn126'
dependencies = []
files = []
hgrepos = []
issue_num = 42484
keywords = ['patch']
message_count = 2.0
messages = ['381947', '382153']
nosy_count = 4.0
nosy_names = ['barry', 'r.david.murray', 'ZackerySpytz', 'dxn126']
pr_nums = ['24669']
priority = 'normal'
resolution = None
stage = 'patch review'
status = 'open'
superseder = None
type = 'behavior'
url = 'https://bugs.python.org/issue42484'
versions = ['Python 3.8', 'Python 3.9']

    Linked PRs

    Activity

    1. dicksonch commented on Nov 27, 2020

      @dicksonch
      dicksonchmannequin
      on Nov 27, 2020
      MannequinAuthor

      parse_message_id in the email module crashes with bogus message-id

      Having a Message-ID '<[>' gives me an IndexError: list index out of range

      This happens when

      • creating an EmailMessage with the said Message-ID
        msg = EmailMessage()
        msg['Message-ID'] = '<[>'

      • accessing the bogus Message-ID through
        msg.items()
        or
        msg.get('Message-ID')

      this doesn't happen with python 3.6 or 3.7 when MessageIDHeader didn't exist

      3.8/Lib/email/headerregistry.py line 542

      _default_header_map = {
    ....
    'message-id': MessageIDHeader,
    }
      Traceback (most recent call last):
  File "/usr/lib/python3.8/email/_header_value_parser.py", line 2069, in get_msg_id
    token, value = get_dot_atom_text(value)
  File "/usr/lib/python3.8/email/_header_value_parser.py", line 1334, in get_dot_atom_text
    raise errors.HeaderParseError("expected atom at a start of "
email.errors.HeaderParseError: expected atom at a start of dot-atom-text but found '[>'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "main.py", line 4, in <module>
    msg['Message-ID'] = '<[>'
  File "/usr/lib/python3.8/email/message.py", line 409, in __setitem__
    self._headers.append(self.policy.header_store_parse(name, val))
  File "/usr/lib/python3.8/email/policy.py", line 148, in header_store_parse
    return (name, self.header_factory(name, value))
  File "/usr/lib/python3.8/email/headerregistry.py", line 607, in __call__
    return self[name](name, value)
  File "/usr/lib/python3.8/email/headerregistry.py", line 202, in __new__
    cls.parse(value, kwds)
  File "/usr/lib/python3.8/email/headerregistry.py", line 535, in parse
    kwds['parse_tree'] = parse_tree = cls.value_parser(value)
  File "/usr/lib/python3.8/email/_header_value_parser.py", line 2126, in parse_message_id
    token, value = get_msg_id(value)
  File "/usr/lib/python3.8/email/_header_value_parser.py", line 2073, in get_msg_id
    token, value = get_obs_local_part(value)
  File "/usr/lib/python3.8/email/_header_value_parser.py", line 1516, in get_obs_local_part
    if (obs_local_part[0].token_type == 'dot' or
IndexError: list index out of range

      as you can see in the traceback
      get_msg_id() calls get_obs_local_part()
      and in get_obs_local_part(), you have this

      def get_obs_local_part(value):

    obs_local_part = ObsLocalPart()

    while value and (value[0]=='\\' or value[0] not in PHRASE_ENDS):
        ...
    if (obs_local_part[0].token_type == 'dot':
        ...

      if value does not satisfy the condition in the while loop,
      this gives an IndexError as obs_local_part is empty
      (the value in my example is '[>' from the message id '<[>')

      shouldn't we have a proper Error or default back to no parsing if parsing fails?
      There's no way of bypassing the parser and getting the Message-ID and
      I can't even handle the error with a try catch

    2. dicksonch
      added
      3.8 (EOL)end of life
      3.9 (EOL)end of life
      topic-email
      type-bugAn unexpected behavior, bug, or error
      on Nov 27, 2020

    3. bitdancer commented on Nov 30, 2020

      @bitdancer
      bitdancer
      on Nov 30, 2020
      Member

      Yep, you've found another in a category of bugs that have shown up in the parser: places where there is a missing check for there being any value at all before checking character [0].

      In this case, the fix should be to add

          if not obs_local_part:
        return obs_local_part, value

      just before the if that is blowing up.

    4. bitdancer
      changed the title [-]parse_message_id, get_msg_id, get_obs_local_part is poorly written[/-] [+]get_obs_local_part fails to handle empty local part[/+] on Nov 30, 2020
    5. bitdancer
      changed the title [-]parse_message_id, get_msg_id, get_obs_local_part is poorly written[/-] [+]get_obs_local_part fails to handle empty local part[/+] on Nov 30, 2020
    6. ezio-melotti
      transferred this issue fromon Apr 10, 2022

    7. lesleyxyz commented on Feb 27, 2023

      @lesleyxyz
      lesleyxyz
      on Feb 27, 2023

      I am currently experiencing this issue, has this been looked at yet? Is there a workaround?

    8. fsc-eriker commented on Feb 9, 2024

      @fsc-eriker
      fsc-eriker
      on Feb 9, 2024
      Contributor

      Duplicate of #105802

    9. serhiy-storchaka
      added 2 commits that reference this issue on Apr 16, 2024

      pythongh-86650: Fix IndexError when parse emails with invalid Message-ID

      07c394c

      gh-86650: Fix IndexError when parse emails with invalid Message-ID (G…

      f74e512
    10. miss-islington
      added a commit that references this issue on Apr 17, 2024

      pythongh-86650: Fix IndexError when parse emails with invalid Message…

      00718c9
    11. serhiy-storchaka
      closed this as completedon Apr 17, 2024
    12. serhiy-storchaka
      added a commit that references this issue on Apr 17, 2024

      [3.12] gh-86650: Fix IndexError when parse emails with invalid Messag…

      95982c9
    13. diegorusso
      added a commit that references this issue on Apr 17, 2024

      pythongh-86650: Fix IndexError when parse emails with invalid Message…

      50d6ca6
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