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[3.11] gh-143927: Normalize all line endings (CR, CRLF, and LF) in configparser (GH-143929) #152006

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Merged
pablogsal merged 1 commit into from
Aug 10, 2026
Merged

[3.11] gh-143927: Normalize all line endings (CR, CRLF, and LF) in configparser (GH-143929) #152006

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gh-143927: Normalize all line endings (CR, CRLF, and LF) in configpar… 
…ser (GH-143929)

(cherry picked from commit 5858e42)

Co-authored-by: Seth Larson <seth@python.org>
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@sethmlarson @miss-islington
sethmlarson authored and miss-islington committed Jun 23, 2026
commit 6c29d2ac15ca8848cd60c68bd36e592cfc028fda
4 changes: 3 additions & 1 deletion Lib/configparser.py
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Original file line number Diff line number Diff line change
Expand Up @@ -945,7 +945,9 @@ def _write_section(self, fp, section_name, section_items, delimiter):
value = self._interpolation.before_write(self, section_name, key,
value)
if value is not None or not self._allow_no_value:
value = delimiter + str(value).replace('\n', '\n\t')
# Convert all possible line-endings into '\n\t'
value = (delimiter + str(value).replace('\r\n', '\n')
.replace('\r', '\n').replace('\n', '\n\t'))
else:
value = ""
fp.write("{}{}\n".format(key, value))
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11 changes: 11 additions & 0 deletions Lib/test/test_configparser.py
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Expand Up @@ -528,6 +528,17 @@ def test_default_case_sensitivity(self):
cf.get(self.default_section, "Foo"), "Bar",
"could not locate option, expecting case-insensitive defaults")

def test_crlf_normalization(self):
cf = self.newconfig({"key1": "a\nb","key2": "a\rb", "key3": "a\r\nb", "key4": "a\r\nb"})
buf = io.StringIO()
cf.write(buf)
cf_str = buf.getvalue()
self.assertNotIn("\r", cf_str)
self.assertNotIn("\r\n", cf_str)
self.assertEqual(cf_str.count("\n"), 10)
self.assertEqual(cf_str.count("\n\t"), 4)
self.assertTrue(cf_str.endswith("\n\n"))

def test_parse_errors(self):
cf = self.newconfig()
self.parse_error(cf, configparser.ParsingError,
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2 changes: 2 additions & 0 deletions Misc/NEWS.d/next/Security/2026-01-16-11-58-19.gh-issue-143927.aviFeG.rst
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Original file line number Diff line number Diff line change
@@ -0,0 +1,2 @@
Normalize all line endings (CR, CRLF, and LF) to LF+TAB when writing
multi-line configparser values.
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