[issue37491] IndexError in get_bare_quoted_string

[R. David Murray]

Change by R. David Murray :


--
resolution:  -> fixed
stage: patch review -> resolved
status: open -> closed

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[issue37491] IndexError in get_bare_quoted_string

[Stéphane Wirtel]

Stéphane Wirtel  added the comment:

@barry

the 3 PR have been merged, do you think we could close this issue?

Thank you

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nosy: +matrixise

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[issue37491] IndexError in get_bare_quoted_string

[miss-islington]

Change by miss-islington :


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pull_requests: +14614
pull_request: https://github.com/python/cpython/pull/14819

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[issue37491] IndexError in get_bare_quoted_string

[miss-islington]

Change by miss-islington :


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pull_requests: +14613
pull_request: https://github.com/python/cpython/pull/14820

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[issue37491] IndexError in get_bare_quoted_string

[Abhilash Raj]

Change by Abhilash Raj :


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pull_requests: +14607
stage:  -> patch review
pull_request: https://github.com/python/cpython/pull/14813

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[issue37491] IndexError in get_bare_quoted_string

[Abhilash Raj]

Abhilash Raj  added the comment:

I just wanted to report before I forgot and hence missed some details, turns 
out the bug report was slightly wrong too. The testcase I provided wasn't right.

Here is the right test case to reproduce the exception with master:

# bpo_37491.py
from email.parser import BytesParser, Parser
from email.policy import default

payload = 'Content-Type:"'
msg = Parser(policy=default).parsestr(payload)
print(msg.get('content-type'))


$ ./python bpo_37491.py 

 
Traceback (most recent call last):
  File "bpo_37491.py", line 5, in 
msg = Parser(policy=default).parsestr(payload)
  File "/home/maxking/Documents/cpython/Lib/email/parser.py", line 68, in 
parsestr
return self.parse(StringIO(text), headersonly=headersonly)
  File "/home/maxking/Documents/cpython/Lib/email/parser.py", line 58, in parse
return feedparser.close()
  File "/home/maxking/Documents/cpython/Lib/email/feedparser.py", line 187, in 
close
self._call_parse()
  File "/home/maxking/Documents/cpython/Lib/email/feedparser.py", line 180, in 
_call_parse
self._parse()
  File "/home/maxking/Documents/cpython/Lib/email/feedparser.py", line 256, in 
_parsegen
if self._cur.get_content_type() == 'message/delivery-status':
  File "/home/maxking/Documents/cpython/Lib/email/message.py", line 578, in 
get_content_type
value = self.get('content-type', missing)
  File "/home/maxking/Documents/cpython/Lib/email/message.py", line 471, in get
return self.policy.header_fetch_parse(k, v)
  File "/home/maxking/Documents/cpython/Lib/email/policy.py", line 163, in 
header_fetch_parse
return self.header_factory(name, value)
  File "/home/maxking/Documents/cpython/Lib/email/headerregistry.py", line 602, 
in __call__
return self[name](name, value)
  File "/home/maxking/Documents/cpython/Lib/email/headerregistry.py", line 197, 
in __new__
cls.parse(value, kwds)
  File "/home/maxking/Documents/cpython/Lib/email/headerregistry.py", line 447, 
in parse
kwds['decoded'] = str(parse_tree)
  File "/home/maxking/Documents/cpython/Lib/email/_header_value_parser.py", 
line 126, in __str__
return ''.join(str(x) for x in self)
  File "/home/maxking/Documents/cpython/Lib/email/_header_value_parser.py", 
line 126, in 
return ''.join(str(x) for x in self)
  File "/home/maxking/Documents/cpython/Lib/email/_header_value_parser.py", 
line 796, in __str__
for name, value in self.params:
  File "/home/maxking/Documents/cpython/Lib/email/_header_value_parser.py", 
line 770, in params
value = param.param_value
  File "/home/maxking/Documents/cpython/Lib/email/_header_value_parser.py", 
line 679, in param_value
return token.stripped_value
  File "/home/maxking/Documents/cpython/Lib/email/_header_value_parser.py", 
line 710, in stripped_value
token = self[0]
IndexError: list index out of range


This time I attached a correct patch instead of copy-pasting only the diff :)

About IndexError, I agree, it must be an empty string value and not a None 
value.

--
keywords: +patch
Added file: https://bugs.python.org/file48462/fix-indexerror.patch

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[issue37491] IndexError in get_bare_quoted_string

[Terry J. Reedy]

Terry J. Reedy  added the comment:

Also, quotes should be attributed to a file and patch snipped should indicate 
the target.  

As for the bug, the author(s) of the expressions "value[1:]" and "value[0]" 
presumably *expected* value to initially have length 2 so that it would be be 
non-empty after clipping.  In the absence of additional information, it is 
possible that the bug is in the unquoted code that produced value.  This is 
potentially true whenever a function or expession raises.

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[issue37491] IndexError in get_bare_quoted_string

[Terry J. Reedy]

Terry J. Reedy  added the comment:

To avoid such questions, bug reports should contain exception messages and 
usually at least some of the tracebacks.

>>> ''[0]
Traceback (most recent call last):
  File "", line 1, in 
''[0]
IndexError: string index out of range
>>> x=None
>>> x[0]
Traceback (most recent call last):
  File "", line 1, in 
x[0]
TypeError: 'NoneType' object is not subscriptable

IndexError should mean object was indexable.
Operations on None should give TypeError.

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[issue37491] IndexError in get_bare_quoted_string

[Abhilash Raj]

Abhilash Raj  added the comment:

Thanks for the explanation Terry!

In this case, value becomes None (I think), which causes the IndexError.

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[issue37491] IndexError in get_bare_quoted_string

[Terry J. Reedy]

Terry J. Reedy  added the comment:

An Python exception is not a crash; a crash is the program stopping without an 
exception and proper cleanup.

If s is a string (rather than, for instance, None),
s and (s[0] == char) is equivalent to s[0:1] == char

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nosy: +terry.reedy
type: crash -> behavior

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[issue37491] IndexError in get_bare_quoted_string

[Abhilash Raj]

New submission from Abhilash Raj :

from email.parser import BytesParser, Parser
from email.policy import default

payload = 'Content-Type:x;\x1b*="\'G\'\\"'
msg = Parser(policy=default).parsestr(payload)
print(msg.get('content-type'))


When trying to review PR for BPO 37461, I found another bug where an IndexError
is raised if there aren't closing quote characters in the input message:

Suggested patch:

@@ -1191,7 +1192,7 @@ def get_bare_quoted_string(value):
 "expected '\"' but found '{}'".format(value))
 bare_quoted_string = BareQuotedString()
 value = value[1:]
-if value[0] == '"':
+if value and value[0] == '"':
 token, value = get_qcontent(value)
 bare_quoted_string.append(token)
 while value and value[0] != '"':

--
components: email
messages: 347190
nosy: barry, maxking, r.david.murray
priority: normal
severity: normal
status: open
title: IndexError in get_bare_quoted_string
type: crash
versions: Python 3.8, Python 3.9

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