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bpo-33529, email: Fix infinite loop in email header encoding (GH-12020) (GH-13321)

(cherry picked from commitc1f5667)Co-authored-by: Krzysztof Wojcik <wojcikk2903@users.noreply.github.com>

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+27

-14

lines changed

+27

-14

lines changed

Lines changed: 13 additions & 10 deletions

Original file line number	Diff line number	Diff line change
`@@ -2724,16 +2724,19 @@ def _fold_as_ew(to_encode, lines, maxlen, last_ew, ew_combine_allowed, charset):`
`2724`	`2724`	`lines.append(' ')`
`2725`	`2725`	`# XXX We'll get an infinite loop here if maxlen is <= 7`
`2726`	`2726`	`continue`
`2727`		`-first_part=to_encode[:text_space]`
`2728`		`-ew=_ew.encode(first_part,charset=encode_as)`
`2729`		`-excess=len(ew)-remaining_space`
`2730`		`-ifexcess>0:`
`2731`		`-# encode always chooses the shortest encoding, so this`
`2732`		`-# is guaranteed to fit at this point.`
`2733`		`-first_part=first_part[:-excess]`
`2734`		`-ew=_ew.encode(first_part)`
`2735`		`-lines[-1]+=ew`
`2736`		`-to_encode=to_encode[len(first_part):]`
	`2727`	`+`
	`2728`	`+to_encode_word=to_encode[:text_space]`
	`2729`	`+encoded_word=_ew.encode(to_encode_word,charset=encode_as)`
	`2730`	`+excess=len(encoded_word)-remaining_space`
	`2731`	`+whileexcess>0:`
	`2732`	`+# Since the chunk to encode is guaranteed to fit into less than 100 characters,`
	`2733`	`+# shrinking it by one at a time shouldn't take long.`
	`2734`	`+to_encode_word=to_encode_word[:-1]`
	`2735`	`+encoded_word=_ew.encode(to_encode_word,charset=encode_as)`
	`2736`	`+excess=len(encoded_word)-remaining_space`
	`2737`	`+lines[-1]+=encoded_word`
	`2738`	`+to_encode=to_encode[len(to_encode_word):]`
	`2739`	`+`
`2737`	`2740`	`ifto_encode:`
`2738`	`2741`	`lines.append(' ')`
`2739`	`2742`	`new_last_ew=len(lines[-1])`

Lines changed: 4 additions & 4 deletions

Original file line number	Diff line number	Diff line change
`@@ -1643,10 +1643,10 @@ def test_fold_overlong_words_using_RFC2047(self):`
`1643`	`1643`	`self.assertEqual(`
`1644`	`1644`	`h.fold(policy=policy.default),`
`1645`	`1645`	`'X-Report-Abuse: =?utf-8?q?=3Chttps=3A//www=2Emailitapp=2E'`
`1646`		`-'com/report=5F?=\n'`
`1647`		`-' =?utf-8?q?abuse=2Ephp=3Fmid=3Dxxx-xxx-xxxx'`
`1648`		`-'xxxxxxxxxxxxxxxxxxxx=3D=3D-xxx-?=\n'`
`1649`		`-' =?utf-8?q?xx-xx=3E?=\n')`
	`1646`	`+'com/report=5Fabuse?=\n'`
	`1647`	`+' =?utf-8?q?=2Ephp=3Fmid=3Dxxx-xxx-xxxx'`
	`1648`	`+'xxxxxxxxxxxxxxxxxxxx=3D=3D-xxx-xx-xx?=\n'`
	`1649`	`+' =?utf-8?q?=3E?=\n')`
`1650`	`1650`
`1651`	`1651`
`1652`	`1652`	`if__name__=='__main__':`

Lines changed: 8 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -237,6 +237,14 @@ def test_adding_default_policies_preserves_default_factory(self):`
`237`	`237`	`email.policy.EmailPolicy.header_factory)`
`238`	`238`	`self.assertEqual(newpolicy.__dict__, {'raise_on_defect':True})`
`239`	`239`
	`240`	`+deftest_non_ascii_chars_do_not_cause_inf_loop(self):`
	`241`	`+policy=email.policy.default.clone(max_line_length=20)`
	`242`	`+actual=policy.fold('Subject','ą'*12)`
	`243`	`+self.assertEqual(`
	`244`	`+actual,`
	`245`	`+'Subject:\n'+`
	`246`	`+12*' =?utf-8?q?=C4=85?=\n')`
	`247`	`+`
`240`	`248`	`# XXX: Need subclassing tests.`
`241`	`249`	`# For adding subclassed objects, make sure the usual rules apply (subclass`
`242`	`250`	`# wins), but that the order still works (right overrides left).`

Lines changed: 2 additions & 0 deletions

Original file line number	Diff line number	Diff line change
`@@ -0,0 +1,2 @@`
	`1`	`+Prevent fold function used in email header encoding from entering infinite`
	`2`	`+loop when there are too many non-ASCII characters in a header.`

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